palm oil refining

. . . . . . . . . .
..........
The Edible Oil & Ghee
Sector
Environmental Report
DRAFT
1
Table of Contents
Preface
Executive Summary
1. Introduction
1.1 Environmental Technology Program for Industry (ETPI)
1.2 Demonstration Project
1.3 Environmental Problems of Edible Oil Industry of Pakistan
2. The Edible Oil Industry
2.1 Raw Material
2.2 Process Chemicals
2.3 Utilities
2.4 Process Description
2.4.1 Vegetable Ghee
2.4.2 Cooking Oil
2.4.3 Acid Oil
2.4.4 Carbon Oil
2.4.5 Soap
3. Environmental Stresses and their Quantification
3.1 Wastewater
3.1.1 Sources and Disposal
3.1.2 Quantification
3.1.3 Characterisation
3.1.4 Pollution Load
3.2 Solid Waste
3.3 Soil Contamination
3.4 Air Emissions
3.5 Noise Emissions
3.6 Occupational Health and Safety (OH&S)
3.7 Energy Inefficiency
4. Impacts
4.1 Impacts Associated with Wastewater
4.2 Impacts Associated with Solid Waste
4.3 Impacts Associated with Soil Contamination
4.4 Impacts Associated with Air Emissions
4.5 Impacts Associated with Noise
4.6 Implication Associated with Occupational Health and Safety
4.7 Impact Associated with Energy Wastage
5. Recommendations
5.1 Wastewater Reduction & Treatment
5.1.1 Size Optimisation of Separation Chambers
5.1.2 Recycling of washing water after neutralisation
5.1.3 Replacement of Gravity Settling by Centrifuge after
Neutralisation
5.1.4 Use of Pressurised Water for Floor Cleaning
5.1.5 Improvement of Foam and Soap Removal from Fat
Traps
5.1.6 Reorganisation of Water Systems
5.1.7 Use of Flow Meters
5.1.8 Construction of a Wastewater Treatment Plant
5.2 Solid Waste
5.2.1 Improvement of Waste Management and Land Filling
5.2.2 Use of Tankers with Internal Coils to Minimise Sludge
5.2.3 Increased Recycling of Nickel Catalysts
5.2.4 Recovery of Oil from Spent Earth
5.3 Soil Contamination Prevention
5.4 Air Emissions Control
5.4.1 Recovery of FFA at Deodoriser
5.4.2 Recovery of CO2 from Gas Cracking Plant
5.4.3 Optimisation of Combustion at Boiler
5.5 Safety and Health (S&H)
5.5.1 Exhaust Combustion Gases out of Gas Cracking
Building
5.5.2 Improvement of Noise Abatement and Protection
5.5.3 Improvement of Working Conditions at the Tin Shop
5.5.4 Use of Material Safety Data Sheets (MSDS) of Raw
Products
5.6 Energy
5.6.1 Recovery of Heat from Cooling Water Used during
Hydrogenation
5.6.2 Pre-heating of Incoming Oil with Outgoing Oil at
Hydrogenation
5.6.3 Pre-heating of Incoming Oil with Outgoing Oil at
Deodorization
5.6.4 Improvement of Steam Pipes Insulation
5.6.5 Increasing Temperature during Deodorization
5.6.6 Installation of a Cogeneration Plant
5.7 General Recommendations
5.7.1 Inert Atmosphere after Deodorization
5.7.2 Covering of Lye Preparation Area
5.7.3 Insulation of Chilling Room’s Doors
5.7.4 Environmental Management Systems (EMS)
LIST OF TABLES
Table 2.1: Edible Oil Local Production and Imports (1995)
Table 2.2: Process Chemicals and their Usage
Table 2.3: Utilities and their Consumption
Table 3.1: Daily Wastewater Discharge
Table 3.2: Wastewater Analysis
Table 3.3: Daily Pollution Load
Table 3.4: Details of Solid Waste
Table 3.5: Air Emission from Different Sources
Table 5.1: Design Data of Primary Treatment System
Table 5.2: Cost Estimates for Primary Treatment System
Table 5.3: Design Data of Secondary Treatment System
Table 5.4: Cost Estimates for Secondary Treatment System
LIST OF FIGURES
Figure 2.1: Ghee Process Flow Sheet
Figure 2.2: Cooking Oil Process Flow Sheet
Figure 5.1: Gravity Settling Tank
Figure 5.2: Chemically Enhanced Dissolved Air Flotation
Figure 5.3: Process Flow Diagram of Activated Sludge System
Figure 5.4: Proposed System for Pre-heating of Incoming Oil with
Outgoing Oil at Hydrogenation
2
Preface
This report is a part of the ETPI demonstration project
component. The purpose of this report is to address the
environmental problems of edible oil sector.
The report has been prepared on the basis of the findings of
the environmental audits of three edible oil mills which
were conducted by ETPI in February, 1998. The study was
jointly carried out by two leading firms of the ETPI
consortium i.e. National Environmental Consulting (Pvt.)
Ltd. and Haskoning Royal Dutch Consulting Engineers and
Architects, The Netherlands.
This report is a step towards the dissemination of
information, about the environmental problems of the
edible oil and ghee manufacturing facility along with the
possible solutions and investment required to mitigate these
problems and to comply the present and future
environmental legislation.
It is envisaged that this effort will help to enable edible oil
mills to initiate efforts to combat the environmental
problems to produce environmentally clean products.
In addition it is hoped this report would also support the
efforts of R&D institutions, environmental equipment and
chemical suppliers, and environmental researchers/students
working towards the betterment of the environment.
We acknowledge the participation of PVMA and edible oil
mills in the program and for extending their co-operation in
all aspects of the study and thank them for their continuous
support and encouragement.
April, 1999
3
Acronyms
BOD Biochemical Oxygen Demand
COD Chemical Oxygen Demand
CT Cleaner Technologies
dB Decibel
E O P END-OF-PIPE
FFA Free Fatty Acids
GCP Ghee Corporations of Pakistan
IHI In-House Improvements
MP Melting Point
MT Metric Ton
NCS National Conservation Strategy
NEQS National Environmental Quality Standards
NG Natural Gas
O&G Oil and Grease
O H & S Occupational Health and Safety
PM Particulate Matter
PPM Parts per Million
RBD Refined Bleached and Deodorized
TDS Total Dissolved Solids
th Thermies = 1000 calories
TSS Total Suspended Solids
VOC Volatile Organic Carbon
4
Executive Summary
Environmental degradation by the industrial sector is a
matter of serious concern in Pakistan. The Federation of
Pakistan Chambers of Commerce and Industry (FPCCI)
with the assistance of the Government of the Netherlands
has undertaken the Environmental Technology Program for
Industry (ETPI) to facilitate the industrial sector in
implementing environmental control projects in Pakistan.
This occurs by initiating measures to combat pollution,
thereby, enabling the industries to comply with the
National Environmental Quality Standards (NEQS) and the
forthcoming ISO 14000 certification.
ETPI aims at the implementation of demonstration projects
of environmental cleaner technologies. ETPI defines
demonstration project as “a project under which those
environmental technologies will be implemented which
offer both technological solutions for pollution abatement
and economic benefits for the industry. At the same time,
the solutions should suit the local conditions for successful
implementation."
ETPI is being implemented in alignment with the National
Conservation Strategy (NCS). It will be implemented in 20
industrial sectors in two successive phases. Six priority
industrial sectors including edible oil and ghee sector are
included in the first phase.
This study focuses on environmental problems caused by
edible oil industries and recommends measures to abate
them.
There are around 160 small and medium sized vegetable oil
and ghee plants in Pakistan with a total capacity of over
two million tons. Most of the mills have integrated
facilities of manufacturing soap as a by-product. The major
raw material used is raw oil extracted from different
botanical species. Pakistan imports 70-80% of the raw oil,
mostly from Malaysia. Water, electricity and natural gas
are the major utilities consumed.
The main processes for cooking oil refining include:
degumming, neutralisation, bleaching and deodorization.
For ghee manufacturing, hydrogenation is also carried out
in addition to these processes.
An edible oil industry generates large quantities of
wastewater. On average, for every ton of oil produced, the
discharge of wastewater is about 30 m3. The wastewater of
edible oil mills can be categorised into process wastewater
and non-process wastewater. Process wastewater
contributes to most of the pollution load in the effluent
being drained by the industry; while non-process
wastewater constitutes the major portion of total
wastewater quantity. The process effluent is high in BOD,
COD, TSS, TDS, oil, phosphate, sulphate and chloride.
Concentration of these pollutants in the process effluent is
much higher than allowable NEQS limits. These pollutants
need to be removed from the effluent to prevent the damage
being done to the environment, as well as to avoid paying
the Environmental Improvement Charges (EIC).
Spent fuller’s earth, spent nickel and filter cloth are the
major solid wastes of oil mills. Spent fuller’s earth and
nickel are sold for down-stream use.
Spillage of oil on uncovered ground around oil storage
tanks results in soil contamination, which can further lead
to contamination of groundwater.
Major sources of air pollution are boiler and generator
exhausts, and emission from the gas cracking unit. From
these sources, carbon monoxide (CO) is emitted in very
high concentration. NOx emission is high in the generator
exhaust. CO and NOx have been suggested by Pakistan
Environmental Protection Agency (PEPA) for selfmonitoring
and reporting and emissions exceeding NEQS
will be liable for EIC. In some industries gas cracking unit
also emits huge amount of carbon dioxide which is a
greenhouse gas.
In general, occupational health and safety (OH&S)
situation is very poor in the edible oil mills. Use of any
protective gear by employees is almost non-existent.
Inefficient and obsolete processes consume and waste
much energy as compared to modern technologies.
The recommendations to improve environmental
performance are categorised as in-house improvements,
cleaner technologies, and end-of-pipe treatment. In-house
improvements and cleaner technologies will not only result
in the improvement of economical and environmental
performance of the mill, but will also reduce the cost of the
end-of-pipe treatment.
Oil losses in the effluent can be reduced either by
increasing the size of the separation chambers beneath the
pre- and post- neutralisation vessels or by replacing gravity
settling by centrifuge separators. This measure will also
reduce BOD and COD of the effluent. Water consumption
as well as discharge can be reduced significantly by
reusing/recycling the cooling water and vacuum water after
proper treatment. End-of-pipe treatment options, which
include oil skimmers and biological treatment of the
process wastewater, are the ultimate solution for
compliance with the NEQS. The oil concentration in the
effluent can be reduced either by gravity settling or
chemically enhanced dissolved air floatation. Aerated
lagoons or activated sludge are the recommended
biological treatment options to remove organic pollutants.
The solid waste management system can be improved by
good working practices. By applying solvent extraction, the
oil content in spent earth can be reduced to 5%. Paving the
area near oil storage tanks and collecting spills will reduce
the risk of soil contamination.
Air emissions can be reduced by optimising the combustion
at boiler and recovering CO2 from the gas cracking plant.
Installation of a stack on the gas cracking exhaust, use of
protective gears such as gloves, goggles, ear muffs, etc.,
will improve the working conditions in the plants.
The wastage of energy can be minimised by efficiently
performing the processes, such as preheating of incoming
oil with outgoing oil at hydrogenation and deodorization.
The edible oil industry is an energy intensive industry and
the industry’s normal working is effected because of power
failure. The new concept of producing electric as well as
heat energy together at the plant, known as ‘Cogeneration’,
has been developed recently in developed countries. It is a
very efficient and cost-effective way to generate electricity
and heat for the industry.
To improve the overall environmental conditions of the
industry Environmental Management System (EMS)
should be implemented. This is also a requirement of ISO
14000.
5
1. Introduction
This report aims to address the environmental pollution
problems of the Edible Oil sector. It has been compiled on
the basis of the findings of three environmental audits,
conducted in three edible oil mills under the Environmental
Technology Program for Industry (ETPI). The objective of
this report is to assess the nature and extent of
environmental problems caused by an edible oil industry
and to recommend solutions to mitigate their impacts. The
limitation of this report is that the information has been
generalised on the basis of the data obtained from three
environmental audits for the whole sector. This limitation
has been minimised using substantial national and
international secondary information available for the edible
oil sector.
1.1 Environmental Technology Program for
Industry (ETPI)
The Environmental Technology Program for Industry
(ETPI) is a joint project of the Federation of Pakistan
Chambers of Commerce & Industry (FPPCI) and the
Government of The Netherlands. The primary objective of
ETPI is to promote the use of environmentally safe
technologies for the production of environmental safe
products by Pakistan’s manufacturing/industrial sector.
To provide the required technical expertise and support to
industries, a consortium of local and foreign consulting
firms has been hired to execute ETPI. The members of the
consortium are.
· National Environmental Consulting (Pvt.). Ltd.
(NEC), Pakistan; the lead consultant;
· HASKONING, Royal Dutch Consulting, Engineering
and Architects, The Netherlands;
· KRACHTWERKTUIGEN (KWT), The Netherlands;
· Management for Development Foundation (MDF),
The Netherlands; and
· Hagler Bailly, Pakistan.
This five year project began in 1996 and works with
Pakistani industries and their associations in identifying
those pollution prevention and abatement technologies
which are economically most feasible, and in implementing
these solutions. The five components of the program
include the development of a user-friendly database of
relevant information, institutional networking within and
between key industrial institutions of the country,
dissemination and communication to promote cleaner
industrial production, institutional support and training to
create in-house environmental capability within chambers
and industrial associations and demonstration projects in 20
selected industrial sectors to demonstrate the economic
feasibility and environmental efficacy of environmental
technologies.
1.2 Demonstration Project
Each component of ETPI has been given specific
definition, and carries its own objective, scope of work and
methodology. The present study is part of the
demonstration project component. Hence, this report will
focus mainly on this component.
As discussed above, physical interventions in the form of
demonstration projects are an integral part of ETPI, which
is defined as a “project under which those environmental
technologies will be implemented which qualify both the
technical and the financial feasibility criteria, and at the
same time are relevant to the local industrialists.
Improvements in processing practices will also be an
essential part of the demonstration projects.”
Objectives of the demonstration project include:
· To establish live examples in the major industrial
sectors of Pakistan for the direct dissemination of
environmental technologies in the country.
· To prepare a representative database in the shape of an
industry specific Environmental Audit for establishing
the environmental policy implication, financial and
institutional support requirements.
· To create a more aware and committed constituency of
industrialists for undertaking environmental
investment.
· To identify industry sector specific research and
development areas in the discipline of environment
and industry for local and international research
institutions.
For the implementation of a demonstration project, a
comprehensive procedure for the selection of industries in
each sector has been developed. According to this
procedure, three industries are selected for an
environmental audit from each sector. Subsequently one of
these three is selected for the demonstration project.
1.3 Environmental Problems of Edible Oil
Industry of Pakistan
The biggest problem faced by an edible oil industry is
wastewater, both quantitatively and qualitatively.
Wastewater generation in an edible oil industry can be
divided into two categories:
· Wastewater generated directly from processes e.g.
neutralisation washings etc.
· Wastewater generated from auxiliary systems e.g.
cooling and vacuum systems etc.
Wastewater generated from both these sources varies
greatly in pollution load and concentration. Process
wastewater contains high amounts of BOD, COD, oil &
grease, TSS, TDS, and nickel etc. Wastewater generated
from the auxiliary systems is huge in quantity and
relatively higher in temperature. It sometimes contains
traces of VOCs. Boiler condensate recovery system is not
efficient in some, and practically non-existent in most.
Apart from liquid waste, solid waste and air emissions are
also generated. Solid waste generation is mainly in the form
of spent earth, filter cloth, and spent catalyst. Spent earth
and spent catalyst are in slurry form and are combined
together to extract what is known as “Carbon Oil” before
their final disposal. After carbon oil extraction, the left over
slurry is sold to contractors.
6
Soil contamination can be seen around oil storage tanks in
oil mills due to spillage on uncovered ground. This also
poses risk of contaminating the groundwater.
Air emissions are generated mainly from boiler and
generator stacks. Besides, process emissions may also be
present, comprising of volatile organic substances from
bleaching, deodorization, etc. In some cases, air emissions
have pollutants higher than the limits mentioned in the
National Environmental Quality Standards (NEQS).
Noise and odour levels at many places in every mill are
high. Temperature of the working areas is generally
acceptable during winter season, but it becomes quite high
during summer. General rating of the lighting and
ventilation arrangements is on a scale of satisfactory to
poor.
A variety of chemicals are used in edible oil processing.
While other chemicals also contribute, use of nickel as
catalyst during the hydrogenation process is the most
important concern from an environmental point of view.
Chemicals used pose a twofold problem. Firstly, they come
in the wastewater or as waste products of chemical
processes. Secondly, they might come into direct contact
with the persons handling them. Generally, practices for
handling of chemicals in oil mills are poor and need drastic
improvement. Open air storage and transportation, manual
feeding, and dripping of chemicals is common. In most of
the mills, workers are improperly attired. Use of protective
gears is very rare, and most of the workers work without
shirts.
Edible oil processing requires quite an intensive use of
energy. It is due to the fact that for different processes and
operations, different temperatures have to be maintained.
The most common modus operandi is to heat up water
either to steam, or to higher temperature, and then to
transfer the energy contained by this water to the material
being processed. Some amount of this energy is consumed
during the processes, while the remaining is lost either
during the cooling of the product for the subsequent
process, or in terms of heat contained by the wastewater. In
almost all cases, an efficient arrangement of heat transfer to
save this energy does not exist.
Though some edible oil mills have acquired ISO 9000
certification and some are passing through the
implementation phase of ISO 9000 standards, others still
lag far behind. A lot more could be achieved from the
occupational health and safety (OH&S) perspective. The
management is keen to undertake environmental initiatives
in many cases. Still, the awareness level in workers and line
staff is dismally low, making the implementation of better
in-house management practices difficult. This, however,
does not liberate the management from the responsibility
and the resulting consequences.
Since it is perceived that environmental protection calls to a
large extent for investments with low or nil payback, it is
natural that most of the industries tend to postpone
environmental protection projects for as long as possible.
This perception is not true in every situation, and often is a
misperception.
With the promulgation of the Pakistan Environmental
Protection Act 1997, the Pakistani edible oil industry will
be required to comply with the regulations for
environmental protection. The Pakistan Environmental
Council’s Environmental Standard Committee has
proposed certain Environmental Improvement Charges to
be imposed on the industries not complying with NEQS. A
formula for calculations of these charges has already been
devised. Therefore, every edible oil mill would have to
thoroughly investigate its existing operations with the aim
of identifying opportunities for containing the
environmental impacts through implementation of
appropriate in-plant measures.
2. The Edible Oil Industry
Pakistani society has traditionally been consuming butterfat
“Desi Ghee” prepared from butter by heating, as a cooking
medium of choice. However, this product has been in short
supply for a long time due to numerous reasons. Therefore,
the past few decades have witnessed an increasing
dependence on the vegetable oil, and products derived from
it. Until the mid-seventies, domestic production of edible
oils was sufficient to meet 75% of the domestic
requirements. A high rate of growth in vegetable oil
consumption afterwards due to population growth, increase
in per capita income, and decrease in the real price of
vegetable ghee, created a gap between production and
demand. The share of imported oils and fats has thus been
increasing gradually to fill up this gap.
Presently, the per capita consumption of vegetable oil/ghee
is 16-18 kg per annum. The average demand growth is
projected at 4.4% per annum between 1988-2000, and the
domestic production is expected to increase by 7.3% during
the same period.
Pakistan’s Edible Oil industry was nationalised in 1972 and
a public sector organisation i.e. Ghee Corporation of
Pakistan (GCP) was created to run this industry. Since
1988, private sector has been allowed to emerge and grow.
Most of the units under the control of GCP have been
privatised. At present 94% of the sector is under private
sector control. A total of around 160 small and medium
sized vegetable oil and ghee plants are operational with a
total capacity of over two million tons.
Two institutions in Pakistan represent the edible oil
industry. The Pakistan Vanaspati Manufacturing
Association (PVMA) is an association of over 100 mills
which import refined crude oil, process and package it, and
market it. The total installed capacity of these units is
around 1.8 million ton. The All Pakistan Solvent Extraction
Association (APSEA) is an association of five mills. These
mills process oil from raw oil seed through solvent
extraction process. The total installed capacity of these
units is around 550,000 tons.
2.1 Raw Material
The edible oil industry uses a variety of raw oils such as
RBD soft and hard1, palmolein, soybean oil, corn oil,
cottonseed oil, rapeseed oil, sunflower oil, and canola oil.
The last five raw materials are used occasionally, either due
to the shortage of the soybean supply, or because of
specific requirement of the product.
1 RBD soft oil is refined, bleached, and deodorized oil with
no hydrogenation. RBD hard oil is refined, bleached and
deodorized oil with hydrogenation.
7
The local production and imports for 1995 is shown in
Table 2.1. Cottonseed, corn oil, and canola (recently) are
purchased from the local market. The local oil seed
production caters to only 20-30% of the requirement,
whereas the rest is imported. Palm oil, which has 80%
share in the imports of oil and fat, is being imported from
Malaysia, while sunflower and soybean are imported from
the Eastern European Block. In fact, by importing over a
million ton of palm oil, Pakistan has become world’s
largest importer of palm oil from Malaysia.
Table 2.1: Local Production and Import of
Edible Oil (1995)
Quantity (Ton) S. # Type
Local Imported
1. Cottonseed Oil 374,400 14,000
2. Sunflower Oil 30,000 24,600
3. Rape Seed Oil 66,000 -
4. Butter Fat 379,900 -
5. Soybean Oil - 200,000
6. Palm Oil - 1,059,000
7. Palm Kernel Oil - 5,800
8. Tallow - 57,000
Total 850,300 1,360,400
Source: PORIM Karachi
Oils mainly consist of triglycerides, however, some
impurities such as gummy matter, pigments, and long chain
free fatty acids (FFA) are also present in them. These
unwanted substances are removed from the oil during
various refining processes.
2.2 Process Chemicals
Various chemicals are used at different stages of the
refining process. A list of these chemicals, and their
utilisation is shown in Table 2-2.
Table 2-2 : Process Chemicals and their Usage
Chemicals Usage
Phosphoric acid De-gumming
Caustic soda FFA removal, oil extraction
from fuller’s earth and soap
manufacturing
Fuller’s earth Pre- and post-bleaching
Nickel sulphate Catalyst in hydrogenation
Citric acid Odour Removal
Vitamins ( A, D &E) To improve nutritional value of
oil
Butyric acid & Ethyl
butyrate
For flavouring the ghee
Antioxidant BHT For stability of the product
Sulphuric acid For acid oil production.
Common salt (NaCl) For soapstock graining and for
the regeneration of cation resin
Monoethanolamine
(MEA)
To absorb CO2 in the
purification of H2 gas.
Source: ETPI primary & secondary surveys
2.3 Utilities
The consumption of different utilities in oil mills is
presented in Table 2-3.
Table 2.3: Utilities and their Consumption
Utility Quantity Usage
Water
(m3)
12 - 45 Washing of oil, cooling &
vacuum systems, steam
production, etc.
Electricity
(kwh)
45 – 130 Process house operations,
vacuum pumps, water
pumps, natural gas
cracking unit, boiler house.
Natural Gas
(Mcf)
3 – 25 H2 gas manufacturing, soap
manufacturing, boilers, etc.
Steam (tons) 1.4 – 3.4 Process house, gas cracking
unit, heating of oil in
storage tanks, decanting.
Source: ETPI surveys
Note: The quantities are based on 1 ton of oil or ghee
produced.
2.4 Process Description
The major process being carried out in the oil mills is the
refining of raw vegetable oil to render it edible.
Hydrogenation is also carried out for ghee manufacturing.
Apart from cooking oil and ghee, soap, acid oil, carbon oil,
and bottled carbon dioxide are also produced as byproducts.
The unwanted material, removed during the oil
refining process, is utilised either for soap or acid oil
manufacturing.
2.4.1 Vegetable Ghee
Vegetable ghee is produced by blending and processing
different raw oils. A detailed process flow sheet is shown in
Figure 2.1.
· De-Gumming
The first step is the removal of gummy matter such as
phospholipids and lipoproteins etc. from raw soybean or
cottonseed oil. It is accomplished by exposing the oil to
water and adding the phosphoric acid at 50oC. As a result
precipitate of gum is generated which is removed from the
oil.
· Pre-Neutralisation
Pre-neutralisation process is done to remove FFA from raw
oil. Caustic Soda solution proportionate to FFA is mixed
with oil. This results in the neutralisation of the FFA. The
resulting soapstock is allowed to settle and then drained out
from the refining kettle. Three hot water washings are
given to remove residual soap.
· Pre-Bleaching
The purpose of oil bleaching is to eliminate its colouring
pigments through the adsorption on bleaching earth.
Fuller’s earth is used for bleaching because of its excellent
adsorption power.
The bleached oil containing fuller’s earth is passed through
a series of filter presses to remove the spent earth.
· Hydrogenation
Hydrogenation process is the hardening of oil to reduce its
un-saturation. At the same time, it improves the stability of
the product against its oxidation. Chemically, the degree of
un-saturation decreases by passing hydrogen gas through
oil in the presence of nickel catalyst at 150oC.
8
Figure 2-1: Ghee Process Flow Sheet
FILTER PRESS
Spent Ni
POST NEUTRALIZATION
INCLUDING WASHINGS
POST-BLEACHING
POST FILTER PRESS Spent Fuller’s
Earth
Ni Recycle
Vacuum
Wastewater
Soap Stock Waste
Water to Soaps Pits
HARDENING STORAGE
CO2, CO, NOx
Fresh Ni
HARD OIL TANK
RAW OIL MAIN STORAGE
DEGUMMING / PRENEUTRALIZER
/
WASHING
Soap Stock &
Wastewater to Soap Pits
PRE-BLEACHER
Vacuum
Wastewater
PRE-FILTER PRESS
NATURAL GAS
CRACKING UNIT
HYDROGENATION
H2
Spent Fuller’s
Earth
DEODORIZER
POLISH FILTER
SEAMING MACHINE
Vacuum Waste
W ater
CHILLING SECTION
WARE HOUSE /
DESPATCH
Phosporic Acid +
Lye + Water
Spent earth + Oil +
Filter cloth washing
Effluents
Fuller’s Earth
9
Post-Neutralisation
Post-Neutralisation is performed in the same way as preneutralisation,
except that dilute lye is used because hard
oil has a low FFA content at this stage.
· Post-Bleaching
Post-bleaching is performed in the same way as prebleaching.
· Deodorization
Most of the odorous substances along with FFA, sterols,
tocopherols, saturated and unsaturated hydrocarbons and
pesticides are stripped out by injecting dry steam into oil at
235 –245oC. Citric acid is also added to remove the odour.
After deodorization, the deodorised oil is cooled in the decooler
to about 85oC. The remaining odorous substances
are removed during the de-cooling under vacuum.
After cooling the hard oil is passed through a final filter
press called “Polish Filter”, which removes undissolved
citric acid, remaining particles of the fuller’s earth or nickel
catalyst, and any other fine impurities. It also reduces the
intensity of the final colour of the oil/ghee.
· Fortification
Before sending to the filling section, vitamin A+D, and
vitamin E are added. Antioxidant BHT is also added for
stability and for the taste of the product. Some flavours are
also added like butyric acid and ethyl butyrate, in a ratio of
88:12.
The finished product after packaging is stored in a chilling
room at a temperature of 0oC for 8-12 hours. This process
converts the hard oil from the molten state into fine
granules and improves its appearance. Afterwards it is sent
to the warehouse.
2.4.2 Cooking Oil
Manufacturing of cooking oil is similar to ghee
manufacturing except that hardening (hydrogenation) of the
cooking oil is not required. Therefore, hydrogenation, postneutralisation,
post-bleaching, and post-filtration are not
performed.
Generally, pure soybean oil (100%) is used in the cooking
oil manufacturing. Cottonseed, canola, sunflower or corn
oil are also occasionally used for this purpose. A process
flow diagram is shown in Figure 2.2.
2.4.3 Acid Oil
Production of acid oil is mainly concerned with the
disposal and treatment of soapstock. Soapstock is generally
treated with excess alkali to enhance saponification of any
remaining neutral oil present in it. Later, it is boiled for 30-
45 minutes through steam coils fitted inside the vessel.
Sulphuric acid is added which reacts with soapstock to
form “acidulated soapstock” or “acid oil”.
2.4.4 Carbon Oil
Carbon oil is extracted from the spent fuller’s earth through
the alkali reaction. Spent catalyst is also mixed with spent
earth for carbon oil extraction. The spent earth collected
from both pre-and post-filter presses is sent to the soap
section. Caustic soda is added in it and the slurry is heated
through steam coils fitted inside the vessel.
Water is also added to facilitate the decanting of oil from the
spent earth. Continuous stirring enhances the skimming of oil
at the upper surface of the slurry. After stirring, the decanted
oil floating above the surface of the slurry is skimmed
manually and is collected in a large drum. Most of this oil is
used in the preparation of soap. Fuller’s earth after carbon oil
extraction is sold to contractor for final disposal.
2.4.5 Soap
Raw materials used in soap manufacturing are soapstock,
oil/ghee spills, soap foam collected from fat traps/soap-pits,
and acid oil or carbon oil.
Caustic soda solution is added to a batch of raw material
and saponified by boiling with live steam. After fatstock
has been saponified, common salt is added to it and boiling
continues. At a certain stage of salt concentration, when
soap becomes insoluble boiling is stopped and the soap is
allowed to settle overnight. It settles to form four layers.
The uppermost layer is foam below this is “neat soap”, the
third layer is of dirty soap or “nigre” and at the bottom is
some spent lye.
After settling, foam is pushed aside and neat soap is
pumped out and filled in frames for solidification.
3. Environmental Stresses and their Quantification
The edible oil industry is one of the many chemical process
industries, which contribute to environmental pollution. In
the following sections pollution from edible oil industries
through various sources have been discussed in detail.
3.1 Wastewater
Generation of large amounts of wastewater is the biggest
environmental problem faced by the edible oil industries.
Wastewater is generated through various sources, varying
greatly both in quantity and quality.
3.1.1 Sources and Disposal
The wastewater generation sources from an edible oil mill
can be broadly divided into four categories:
· Process wastewater
· Cooling water
· Vacuum water
· Boiler and softening plant
Detail of these sources is given in the following section:
· Process wastewater
Following processes contribute to process wastewater:
Neutralisation
Generation of wastewater from the pre-/postneutralization
process is periodic. Wastewater
containing soapstock is transferred into a separation
chamber, with generally three compartments. Soapstock,
10
Figure 2-2: Cooking Oil Process Flow Sheet
DECANTING UNIT
RAW OIL
MAIN STORAGE TANK
* DEGUMMING
NEUTRALIZATION
INCLUDING WASHING
BLEACHING
FILTER PRESS
DEODORIZER
COOLERS
SEAMING MACHINE
WARE HOUSE /
DESPATCH
HOT OIL TANKS
DRYING
Waste Water & Soap
Stock to Soap Pits
Vacuum (wastewater)
Spent Fuller Earth
(to Soapry & Oil)
* Cotton Seed / Sunflower Oil
POLISH FILTER
Phosphoric Acid
Fullers Earth
Vacuum (Condensate)
Lye + H2O
Effluent
Good Oil
Vitamins + BHT
(30 g. + 20 g.)
11
oil, and water are separated in the successive
compartments. Wastewater goes to the fat trap after
separation of soap stock and water.
Acid Oil Production
Acid oil production is another source of wastewater.
Wastewater stemming from this source is small in
quantity but qualitatively it is significant.
During this process ‘acidulated soapstock’ or ‘acid oil’
rises upward in the reaction vessel due to its low
density, while the acid water, containing remaining acid,
sodium sulphate and water-soluble impurities, settles
down. The acid water is drained out to the fat trap from
where it is discharged into the sewer.
Soap Manufacturing
The brine water from the graining process during soap
manufacturing is drained out after settling. This wastewater
goes to the soap pit and after decanting oil and soap, it is
discharged into the sewer.
Filter Cloth Washing
The filter cloths, used in the filter press, are washed using
caustic soda, water, steam and detergents. The caustic bath,
which is very small in quantity, is retained and is drained
once every three months. Water bath is drained every
month and detergent washing is intermittent. All the above
three streams go into the final trap and after decanting oil,
wastewater is discharged into the sewer.
· Cooling Water
Water is used for equipment/product cooling purposes in
hydrogenation, deodorization, gas cracking unit and
ammonia compressors. The cooling water is recirculated
after dissipating its heat by spraying. The capacity of
spraying system is generally insufficient to dissipate
enough heat quickly, hence most of the water is drained
out.
· Vacuum Water
Water is used in the vacuum system to provide vacuum for
certain operations. Vacuum water having relatively high
temperature (average 35oC) is cooled through spraying and
then is re-circulated. As the spraying system does not have
the required efficiency in most cases, a portion of water has
to be discharged to maintain the temperature to the desired
level.
· Boiler and Softening Plant
The boiler generates wastewater as blowdown. Some
wastewater is also generated during the regeneration of the
softening plant. The pattern of wastewater generation is
periodic, however it is distributed almost evenly over 24
hours.
Disposal
Edible oil industries usually dispose off all their effluent
into nearby receiving water bodies, such as canal, river or
sea, without any treatment.
3.1.2 Quantification
The quantification of wastewater was done on the basis of
water balance, flow monitoring, and water consumption.
Based on the information of audited mills, the typical
ranges of wastewater generation are tabulated in Table 3-1.
Table 3-1: Daily Wastewater Discharge
Source Wastewater Quantity
m3/100ton of oil/ghee
Processes 50 - 80
Auxiliary Systems 1400 - 3600
Total 1450 - 3680
Source: ETPI survey
3.1.3 Characterisation
Wastewater of an edible oil mill can be divided into two
separate classes i.e. process wastewater and non-process
wastewater. The process wastewater was found to be highly
polluted as compared to non-process wastewater. The
characteristics of process wastewater and non-process
wastewater are given in Table 3.2.
Table 3.2: Wastewater Analysis
Parameter
Process
Wastewater
Cooling &
Vacuum
Wastewater
pH 11 – 12 6 - 8
Temp (oC) 40 – 50 -
BOD5 450 – 700 -
COD 1300 – 2100 -
TSS 2000 – 16500 -
TDS 3000 – 20000 350 - 10000
Oil & Grease 100 – 180 0 - 5
Nickel 2 - 2.5 -
Phosphate 10 – 20 -
Sulfate 10000 - 15000 -
Chloride 1525 - 5300 -
Conductivity 30 - 1400 -
Total Alkalinity 6000 - 22200 -
Source: ETPI survey, 1998
Note: All values are in mg/l, except pH, Temp. (oC) &
conductivity (ms/cm).
3.1.4 Pollution Load
The pollution load generated daily by edible oil mills is
presented in Table 3-3. This has been calculated by
multiplying quantity of wastewater with the concentration of
each parameter.
Table 3-3: Daily Pollution Load
Pollution Load
Parameters Mill-1 Mill-2 Mill-3
BOD5 60 230 1,600
COD 170 380 3,000
TSS 280 130 3,100
TDS 3,750 960 5,400
O&G 15 0.8 15
Ni 0.05 0.5 0.5
PO4
--- 4.2 -- --
SO4 200 -- --
Cl- 304 1,530 95,000
Total Alkalinity 1,150 1,000 1,800
Source: ETPI survey
Note: All quantities are in Kg per 100 tons of oil/ghee
12
3.2 Solid Waste
Solid waste generated by edible oil mills can be classified in the
following general families:
- General waste
- Tin scrap
- Filter cloth
- Sludge from settling ponds, fat traps and raw oil tanks
- Spent earth
- Spent catalyst
- Spent lubricants
General type of waste produced usually contains pipes, mild
steel (MS) sheets, iron angles, wires, cans, bottles, and waste
paper. Some of this solid waste is sold to a contractor on
monthly basis, while the remaining is disposed off at municipal
garbage dumps.
Tin scrap consists of rejected tin containers, lids and waste from
tin can manufacturing area. Tin waste is temporarily stored
inside the mill and afterwards is sold for recycling. The quantity
of scrap is estimated to be 2-10% of the total tin used.
Filter cloth is used in the filter press. Once the filter cloth is
fixed in a filter press, it could serve for 4-6 batches after which,
the filter press is dismantled and filter cloths are washed. One
piece is used twice or thrice before it is discarded. After
rejection, filter cloths are used for floor cleaning and general
cleaning purpose.
When water ponds are cleaned the sludge is produced. The
quantity is dependent on the quality of water stored. Sludge is
also produced in the fat trap, where the oily wastewater from
pre- and post- neutralisation is stored. This sludge is used for
soap manufacturing. Wastewater from the filter cloth washing,
acid oil production, soapstock tanks and soap manufacturing
goes to another fat trap. The sludge from this trap is also used to
make soap.
Raw oil tanks are emptied twice a year for cleaning purposes.
Raw oil storage tank also produces sludge. The sludge that is
settled at the bottom is salted and heated. The upper layer of oil
is skimmed to be used in the process. The rest is sent to the soap
section for soap production.
Fuller’s earth is used in the pre-and post-bleaching process. Oil
content of spent Fuller's earth after filtration of the oil coming
from bleaching is about 40% by weight. This earth is scraped
from the filter clothes and processed to extract carbon oil.
Afterwards, it is sold to outside vendors. The cleaning is done
manually and needs considerable labour force, as spent earth is
put into used fullers earth bags and taken out of the building by
workers.
Nickel (Ni) is used in hydrogenation process as a catalyst. The
general practice is to recycle some of the used nickel and to add
fresh catalyst for the total required quantity. The ratio of
recycling to fresh varies from mill to mill. After about 5 batches,
the spent Ni is completely replaced by fresh Ni. Spent Ni is
mixed with spent earth and treated for carbon oil extraction.
Afterwards it is disposed off, generally with spent earth.
Spent lubricants come from the machinery and equipment
maintenance. These are sold for reuse or for burning in cement
kilns or brick furnaces. The details of solid waste generated by
edible oil mills, with its per annum quantities, are tabulated in
Table 3-4.
Table 3-4: Details of Solid Waste
S. No. Category Type/Source Quantity Fate
1 General Pipes, MS sheets, iron angles,
wires, cans, broken glass,
bottles, paper, plastic, etc.
Sold or disposed off
2. Tin Scrap Tin workshop Sold for recycling
3. Filter Cloth Filter press 0.1 - 0.2 m Mostly used for cleaning etc.
Finally thrown with garbage
4. Sludge From water ponds
From small fat trap
From big fat trap
From raw oil storage tanks
Disposed off at solid waste disposal sites
Used for soap making
Used for soap making
Used for soap making
5. Spent Fuller’s
Earth
Pre-bleaching, post-bleaching,
carbon oil making
6 - 9 kg Sold after Carbon oil extraction
6. Spent Nickel Hydrogenation 20 - 160 g Mixed with spent fuller’s earth and carbon oil
is extracted from the mixture. Afterwards, the
spent mixture is sold to contractors for down
stream uses
7. Spent Lubricants From machinery Sold to contractors for burning in kilns or
furnaces.
Source: ETPI Survey
Note: Quantities of wastes are based on per ton of oil/ghee produced.
3.3 Soil Contamination
Soil contamination in an edible oil industry is due to oil
spillage. Oil spillage on soil can be found, in the following
areas:
· Underground furnace oil deposit: Uncovered soil near
underground furnace oil deposit gets highly polluted
with furnace oil spillage.
· Raw oil tanks: Uncovered soil near raw oil tanks gets
highly polluted with raw oil spillage.
· Carbon oil manufacturing area: Bags containing spent
earth are stored on unprotected soil and in the open air.
This means that polluted rainwater and leachates from
this area go into the soil.
13
3.4 Air Emissions
In general, vegetable oil refining processes does not have
significant air emissions. In the refining process, materials
are volatilised, but in every case the volatilised material is
condensed either for recovery or to maintain low pressures
in the systems.
Vents from storage tanks of raw oil and products that have
a certain vapour pressure can be a source of vapours. This
emission occurs principally on the filling of the tanks.
However, the vapour pressure of vegetable fats and oils is
such that the contribution is not significant.
Air emissions emitted by an edible oil mill come chiefly
from the auxiliary systems, i.e. boiler, gas cracking plant,
and power generator etc. Samples from these sources were
analysed. The results of these analyses are presented in
Table 3-5.
Table 3-5: Air Emission from Different Sources
S. No. Emission Boiler Generator Gas Cracking
Plant
NEQS
1. CO, mg / Nm3 40-130 2060 3000 800
2. CO2, VOL % 2 –205 0.8 18 -
3. NOx, mg/Nm3 60-125 1300 -- 400
4. SO2, mg/Nm3 -- 110 -- 400
5. Smoke, Ringlemann Scale -- 5 -- 2
6. Particulate Matter, mg/Nm3 -- 275 -- 300
Source: ETPI survey
3.5 Noise Emissions
Industrial equipment and machinery create high noise levels
during operation. The main noise sources in edible oil
industry include:
- Steam ejectors at the roof of main process building
- Tin can manufacturing
- Gas cracking plant
- Boiler
- Hydrogen compressor
- Ammonia compressor
The noise levels in the above mentioned areas are quite high,
although they were not measured. The allowable noise level
under NEQS is 80 dB.
3.6 Occupation Health and Safety (OH&S)
In edible oil mills OH&S hazards are due to the following
reasons:
- Improper handling of chemicals.
- Poor ventilation
- Slippery floors
- High noise levels
The use of protective gears in handling of chemicals is nonexistent.
Workers were found bare handed working with
chemicals such as caustic soda.
Because of poor ventilation in the process area, fumes
emitted from different processes stay inside for longer time.
Floors get slippery because of oil spills in refining area.
Also industry uses detergent to wash the floor after every
shift, which makes the floor even more slippery.
3.7 Energy Inefficiency
Refining of edible oil includes a number of heating and
cooling operations where the transfer of thermal energy takes
place. This transfer of energy is not efficient in most of the
edible oil mills of Pakistan. Wastage of energy is due to
following reasons in oil mills:
- Cooling of oil after hydrogenation and deodorization.
- Improper insulation of steam pipes.
- Prolonged deodorization at low temperature.
Steam distributing pipes without proper insulation results in
decrease of steam temperature hence more steam is required.
In some industries deodorization of edible oil is carried out
at 190oC for a period of 1.5 hours. However, in the
literature it is reported that the process is carried out at 235-
245oC, which is accomplished only in 25 minutes. The low
temperature deodorization, not only reduces the production
rate, but also increases the oil losses in terms of
polymerisation.
4. Impacts
The major adverse impacts of environmental pollution
caused by the edible oil mills are discussed in this chapter.
These impacts have been described with respect to the local
and global environment, workers health & safety and
deviation from the NEQS.
4.1 Impacts Associated with Wastewater
Pollution of water is the most important environmental impact
of edible oil mills. Impacts of wastewater generated from
edible oil mills are evaluated while keeping in mind the
14
final destination of wastewater. Adverse effects of
pollutants on the ecosystem as well as on the surrounding
population are also taken into account. These impacts are
discussed pollutant wise in the following sections.
· pH
Most of the processes discharge highly alkaline (pH >10)
wastewater but some processes such as acid oil production
discharge highly acidic effluent. Aquatic life is severely
effected by the pH of the water and a larger deviation from
neutral pH could alter the natural biological activities. Also,
acidic or basic wastewater does not facilitate the biodegradation
of organic pollutants. Wastewater with a high
pH value is also corrosive to the sewer system of the area.
· Organic Pollutants
The COD value is the amount of oxygen required to
degrade the pollutants present in the wastewater through
chemical degradation. COD indicates the chemically
degradable pollutants. Similarly BOD indicates the
biodegradable organic pollutants. BOD and COD cause the
depletion of dissolved oxygen in the water body.
Deficiency of oxygen in receiving water could cause
adverse effects on biological activity in the water
environment. In the worst case this can result in the total
depletion of oxygen in the receiving water, causing an
anaerobic environment. This would be fatal to aerobic life
and would also create odour problems.
High COD/BOD ratio indicates the persistence of
chemicals present in effluent. Persistent chemicals always
pose risk of entering into the food chain.
· Phosphates
Phosphorus is an essential nutrient for algae and other
biological organisms. A high concentration of phosphates,
if discharged into the surface water, can result in the
growth of undesired aquatic life such as algae. This can
lead to the eutrofication of the receiving water body. In
most of the countries, the phosphate concentration
allowable for discharge in water bodies is less than 1ppm
because of these characteristics.
Presently NEQS do not have any limit for phosphate in
wastewater but it is likely that phosphate limits will be
imposed in near future.
· Sulphates
Under anaerobic conditions sulphate is reduced to sulphide
and can form hydrogen sulphide. H2S is highly malodorous
gas and toxic at high concentration. Offensive odour can
cause poor appetite for food, impaired respiration, nausea,
vomiting and mental perturbation. Also, H2S can be
oxidised biologically to sulphuric acid which is corrosive to
drain pipes.
· Chlorides
Chloride concentration in wastewater is not significantly
reduced by conventional wastewater treatment methods,
hence finds its way into the receiving water. High
concentration of chloride in the water may convert the
agricultural land into saline land and unfit for agriculture if
the receiving water is used for irrigation purpose.
· Particulate and Sediments
Suspended solids present in process wastewater are
partially organic in nature. Upon settling in the bottom of
the water body, they decompose aerobically as well as
anaerobically, depending on the prevailing condition. In
aerobic decomposition, dissolved oxygen of the water body
is consumed, creating a potential for adverse effects on the
ecological system of the water environment. Anaerobic
decomposition of organic compounds will generate odour.
Suspended solids also reduce the aesthetic value of the
receiving water body.
· Total Dissolved Solids (TDS)
Process effluent from the edible oil mills also contains
large quantities of TDS. Most of the dissolved solids are
undesirable in the receiving water. Dissolved minerals and
organic constituents may produce aesthetically displeasing
colour, tastes and odour. Some chemicals may be toxic and
some of the dissolved organic constituents are known to be
carcinogens. Quite often two or more dissolved substances
combine to form a compound whose characteristics are
more objectionable than those of the original matter.
· Oil and Grease
The concentration of oil and grease in process effluent is
many times higher than allowable limits of NEQS. High
amount of oil present in the wastewater may reduce
absorption of oxygen by the receiving water body, hence
resulting in the depletion of dissolved oxygen. This may
endanger aquatic life as discussed earlier.
Also, oil films on the surface of water result in reduction of
light transmission through surface water, thereby reducing
photosynthesis by aquatic plants. Oils may also form
suspension or emulsion in the water, which could be
harmful for fish and other aquatic life.
· Nickel
Nickel is a heavy metal and is used as a catalyst in the
hydrogenation process of ghee manufacturing. Some of the
nickel is discharged into the effluent while most of the
spent nickel is disposed off as solid waste. Nickel is an
essential element in animal nutrition in trace quantities but
toxic and carcinogenic in higher concentration.
4.2 Impacts Associated with Solid Waste
Dumping of rubbish and waste inside the plant causes
unhygienic conditions.
The sludge that is formed at the water ponds decreases the
pond’s capacity, its recycling capability, and the quality of
water.
Having large amounts of sludge in the fat traps affect the
treatment capacity, as the water flows from one basin to the
next underneath the concrete baffles.
Burning spent nickel in kilns may result in the emission of
nickel compounds in the air. As nickel dust is a possible
carcinogen, producing respiratory cancer, hence its entry
into the air can pose a problem to the population living near
the kilns.
Burning spent oil and lubricants without any control about
the composition of the oil and the flue gases from
combustion is a source of air pollution.
15
4.3 Impacts Associated with Soil
Contamination
Soil contamination can cause ground water pollution that
may afterwards affect surface water.
Soil contamination nowadays is an important issue in
industrialised countries, and companies are very concerned
about its grave environmental impacts. In the past,
industries did not take into account the importance of soil
contamination, but this has drastically changed in the last
few years, as the price of land can decrease, or even
become nil, when the soil where the industry is located is
polluted.
4.4 Impacts Associated with Air Emissions
Impacts associated with possible air emissions from edible
oil industries are given in the following sections.
· Oxides of Nitrogen
Oxides of Nitrogen are emitted from boiler stack and the
generator exhaust.
Continuous or intermittent exposure of humans to NOx
may cause certain illnesses, such as irritation in the
respiratory tract and abnormal accumulation of fluid in the
lungs leading to pulmonary edema. Direct exposure of NOx
to soil causes necrosis, causing vegetation loss and may
lead to inhibition of plant growth.
NOx undergo various photochemical and chemical
reactions in the atmosphere leading to the formation of
photochemical smog and acid rain. Although, emissions of
NOx from generator are for short period of time, still the
cumulative effects of NOx at global scenario should not be
ignored. Depletion of ozone at stratosphere level, formation
of photochemical smog and acid rain may occur due to this.
· Oxides of Sulphur
Oxides of Sulphur are emitted in oil mills due to the
burning of fuels in the generator, and also from gas
cracking. Direct exposure to these oxides can be very
harmful to human health, plants and vegetation. The
harmful effects are dependent on the concentration and
exposure duration. Indirectly SOx reacts in the atmosphere
to form photochemical smog and acid rain.
· Carbon Monoxide
Carbon monoxide is a colourless non-irritating gas, which
is generated due to incomplete combustion.
At high concentrations exceeding 5000 ppm with an
exposure of few minutes, this gas can be fatal for human or
animal lives, by reacting with haemoglobin to form
carboxyheamoglobin.
At much lesser concentrations, buut with a high duration of
exposure, this gas may still be dangerous for human beings,
as it may cause damages to visual perception, manual
dexterity and the ability to learn.
Concentration of CO from the methane cracking plants and
the generator exhausts of the audited mills are very high.
Therefore its long-term impacts can not be ignored.
· Particulate Matter (PM)
Particulate matter covers a large variety of particles,
varying in size and chemical composition, however in this
report, the fine particles of carbon from burning fuel are
considered.
Adverse effects of the particulate matter on human health
are reported in relation to the diseases of the respiratory
system. Lowering of the aesthetics value of a place and loss
of general visibility may also be attributed to PM at high
concentration.
The general corrosion reactions on building materials, due
to the presence of NOx and SOx in the air, may also get
catalysed due to the presence of particulate matter.
· Carbon Dioxide (CO2)
Carbon dioxide is generated in large quantities during
natural gas cracking in edible oil mills. In some mills this is
collected and sold to beverage industry. While in others this
gas is exhausted into the atmosphere. Laboratory results of
gas cracking plant exhaust show that the concentration of
CO2 in the exhaust is about 500 times of its concentration
in clean air.
CO2 is a green house gas and its higher concentration in the
atmosphere is responsible for the phenomenon of ‘global
warming’.
4.5 Impacts Associated with Noise
Noise is considered as an interference to and imposition
upon comfort, health and the quality of life. Given the
conditions like exposure limit and time, noise may have
both physiological as well as psychological effects on
human health.
Physiological effects include dizziness, nausea, unusual
blood pressure variation, physical fatigue, loss of hearing,
etc. While reduced mental capability and irritations may
attribute to psychological effects.
Very high noise levels were observed in the surrounding of
the generator room and the boiler house. As these
operations require almost full attention from the workers all
the time, therefore each worker is expected to be exposed
to high noise for at least 8 hours in 24 hours. This condition
may lead to a permanent hearing loss for workers as well as
physical and mental fatigue, which consequently may lower
their manual and mental dexterity.
4.6 Implications Associated with
Occupational Health and Safety (OH&S)
In edible oil refineries major issues related to OH&S are
handling of chemicals, improper ventilation in process
building, slippery floors and exposure to high noise.
Workers in Pakistan are habitually prone to work with bare
hands and feet. This puts them at the high risk of
contracting skin disease, such as chemical burns, irritations,
ulcers, etc. Handling of hazardous chemicals such as
caustic soda, sulphuric acids, nickel oxides, etc. without
protective gears poses serious health as well as safety
hazard.
In some industries fumes and exhaust gases emitted from
different processes stay in the process building because of
improper ventilation These cause discomfort to workers
and also reduces their output. Some processes also emit
VOCs which may be carcinogenic.
16
Slippery floor of the process building due to oil spills on
the floor, always poses risks of injuries to employees.
4.7 Impacts Associated with Energy Wastage
Environment is nowadays understood as a wide and
comprehensive field that includes not only avoidance of
pollution, but also efficient use of energy and natural
resources. Inefficient usage of energy has the following
disadvantages:
· Wastage of money, as more natural gas or electricity is
consumed.
· Wastage of non-renewable natural resources, as the fuels
required to produce the energy are limited natural
resources.
· Higher emissions of air pollutants such as carbon dioxides,
as more natural gas and fuel are burnt.
5. Recommendations
A number of recommendations, aimed at the improvement of
environmental conditions of edible oil industries, have been
formulated on the basis of the findings of the three audits by
ETPI, and information available through various secondary
sources. Each recommendation has been developed and
worked out on the basis of the present state of information.
For further development and cost estimation of each
recommendation, more specific data would be necessary. This
can be undertaken at the implementation stage.
5.1 Wastewater Reduction & Treatment
In the following sections, the detailed description for the
relevant recommendations formulated for wastewater
reduction and treatment is given.
5.1.1 Size Optimisation of Separation Chambers
Due to the small size of separation chambers beneath the preand
post neutralisation vessels, a proper retention time is not
being given to the washing effluent containing the soapstock
and oil etc. This results in incomplete separation of soapstock,
oil, and wastewater. It is recommended that the size of these
chambers be optimised. This would give the following
advantages:
· Oil losses would be minimised and the recovery of good
oil would be enhanced at this stage, leading to economic
benefits.
· The pollution load in the outgoing water would be
minimised, leading to size optimisation of the end-ofpipe
treatment.
5.1.2 Recycling of Washing Water after
Neutralisation
Usually six to seven washes of about 1 m3 each are applied
after pre-neutralisation and four washes of 1 m3 each after
post-neutralisation to remove soapstock from oil.
The pollution load transferred to washing water decreases
from the first wash to the last wash. Therefore, it seems
feasible to reuse the water coming from the last wash in the
first wash of the oil. In this sense, it is recommended to make
some trials to check the possibility of using a counter current
washing scheme after post-neutralisation. If the results
achieved in post-neutralisation are encouraging enough, the
same trial could be made for pre-neutralisation. Counter
current washing is a normal practice in many industrial
processes.
The importance of decreasing the amount of water used for
washing after neutralisation is not based on the intake water
savings, but on the reduction of the wastewater treatment
plant size. Since pre- and post-neutralisation are the two
main sources of process wastewater and a future treatment
plant would be meant mainly for treating process water, a
reduction on pre- and post-neutralisation wastewater means
a reduction in the investment and operational cost of such a
plant.
5.1.3 Replacement of Gravity Settling by
Centrifuge after Neutralisation
Soapstock and washing water are separated from the oil, after
pre- and post-neutralisation, by means of gravity settling.
The separation of soapstock and water from oil can be
improved by means of centrifugal separators, in which
centrifugal force is applied to separate fractions as it forces the
heavier particles towards the periphery, while the light phase
flows toward the centre of the separator.
The separation efficiency of centrifugal separators is much
higher than of gravity settling. This results in the following
positive effects:
· Reduction in oil losses
Because of better separation caused by the centrifugal force,
less oil is lost with soapstock and washing water. It has been
reported that the use of centrifugal separators instead of
gravity settling can reduce the loss of oil during
neutralisation to more than 25%.
· Reduction of washing water
When centrifugal separators are used, only 2 washes (with an
amount of water of about 10% of the oil weight each) are
required. According to the information received from
equipment supplier, normal process water consumption when
using centrifugal separator is about 50% of present
consumption. Also it will mean a reduction in the investment
and operational cost of the treatment plant.
· Reduction of water content in oil
The use of centrifugal separators will also reduce the amount
of water that remains in the oil after neutralisation by 50%. As
this water must be evaporated before bleaching, the decrease
of water content of the oil will mean a reduction in the amount
of steam required and the time used for this purpose.
· Improvement of oil quality:
Another benefit of using centrifugal separators is the
improvement of the oil quality after neutralisation. The
following oil quality can be achieved after neutralisation if
centrifugation is applied:
Switching from gravity settling to centrifugal separation
means a drastic change in the neutralisation process. It is not
possible to carry out this step by means of some new
equipment and some small modifications to the present
17
process. First of all, it means a change from batch process to
continuous process. Secondly, a complete new installation
has to be purchased and installed.
Table 5.1: Oil Quality due to Centrifugation
Characteristics Incoming Oil Product
Max. FFA content 5 % 0.05%
Max. Phosphatide content 200 ppm 5 ppm
Max. soap content 100 ppm
Max. impurities content 0.1%
Max. moisture content 0.5% 0.5 %
Source: Equipment suppliers
The investment cost of a new refining plant of 187 ton/day
capacity is estimated at Rs. 33,000,000.
Annual savings achievable due to process improvement can
be summarised as follows:
· Decrease of oil losses: approx. Rs 4,100,000/year
· Steam savings at bleaching: approx. Rs 160,000/year
· Personnel cost savings: a modern continuous refining
process is fully automatic and needs minimum of
personnel attention. One worker, with a part-time job,
can operate this installation (including necessary
cleaning and maintenance works).
· Savings in chemicals: with high efficiency equipment
(mixers, reactors, separators), reactive and chemicals
consumption is reduced when implementing a continuos
centrifugal separation system.
· Increase in energy consumption: centrifugal separators
have high electricity consumption. Thus, the
implementation of centrifugal separators will mean an
increase in the electricity demand of the mill. An
installation as described above, has a typical electricity
demand of 12 kWh per ton of oil.
Comparing the investment cost with estimated annual
savings, the payback period of implementing a centrifugal
separation system can be estimated to be about 5 years.
5.1.4 Use of Pressurised Water for Floor Cleaning
It is recommended to use hoses with automatic shut down and
pressurised water nozzles (water flow stops automatically
when the hose is left on the floor) to clean the floor, in order
to increase the efficiency of washing and save the water.
5.1.5 Improvement of Foam and Soap Removal
from Fat Traps
Soap and foam is removed from the fat traps manually after
closing the outlet of the last fat trap and raising the water
level. As outlet of the last fat trap is closed, the water rises and
overflows from the last trap to the drain. The skimming soap
and foam is, therefore, discharged in the drain.
It is rather simple to provide the fat trap with a mechanical or
manual system that can take out the fat from the traps without
the need of raising the water level. The simplest form is a pipe
of about 6” diameter positioned across the water surface and
mounted at the ends in slip bearing. The pipe has a slot cut in
it lengthwise. The pipe is equipped with a means of rotating
and sliding arrangements so that the slot may be positioned at
the desired elevation and the pipe can be moved along the
chamber. The slot is left at the top normally. When it is
desired to skim fat, the pipe is turned until the slot is below
the fat surface. The oil flows into the pipe to a sump at the
end.
The investment required is very low (about Rs.25,000) and
daily operation will benefit as well as the environment. Such
fat removers may be even fabricated locally at the industry’s
own workshop.
5.1.6 Reorganisation of Water Systems
Total water consumption can be minimised by means of
reorganising the water scheme. This reorganisation consists
mainly in segregating the water according to its use and pretreating,
recirculating and finally treating/discharging each
separately. Though, there is a certain segregation of water in
industry, it could be improved, as some of the water types are
mixed up. This would result in a decrease in water
consumption hence in a smaller size wastewater treatment
facility.
Recommendations on how to maintain the quality of each
type of water with the aim of keeping the cycles as close as
possible and with minimum addition of fresh water are
given below:
a) Process water:
The food industry is generally subjected to strict
requirements regarding quality of water that is in contact
with the product. In the previous sections, recommendations
to reuse and reduce the consumption of process water have
already been outlined. The final treatment for process water
is discussed in section 5.1.8.
b) Cooling and vacuum water:
Presently, edible oil mills either discharge the cooling water
into the drain or recirculate it in the vacuum system. It is
recommended to establish two separate semi-closed systems,
for cooling and vacuum water, providing both of them with
cooling towers to dissipate heat. By maintaining proper water
quality it is possible to operate the cooling and vacuum
systems in a closed loop, requiring low make-up water
addition and decreasing the water consumption considerably.
For the vacuum water system an indirect cooling system is
recommended. Vacuum water should be cooled in a heat
exchanger with cooling tower water before being recycled to
the vacuum system. Thus, there is no direct contact between
the two water systems, and the problem of odour and/or
presence of any organic compounds is avoided. The heat
exchanger will need some cleaning, therefore it is advisable
to have two heat exchangers, one in operation while the other
is on stand-by.
For long lasting and smooth operation and efficiency of the
cooling system it is necessary to avoid corrosion, scale
formation and micro-organism and bacteria development.
These problems are normally avoided by means of using
water of an appropriate quality, applying some treatment
(such as filtration) and by dosing some additives.
Because of evaporation, there is an increase of salt content in
water, which results in the scale formation. This is normally
mitigated with a continuous blowing down of certain amount
of water, which is replaced by fresh water.
18
c) Recovery of steam condensate at boiler:
Presently, edible oil industries recover only about 15-50% of
the steam as condensate. The rest is drained as water or sent
to the air at deodoriser.
Following are the advantages of recirculating the condensate:
· Energy savings, as temperature of condensate is higher
than the intake water
· Less water consumption
· Less cleaning cycles of the ion exchange resins
· Less chemicals consumption
With a good piping system, 80% recirculation rate of
condensate is possible. A good piping system means high
quality materials at heat exchangers and a good preventive
maintenance program (to avoid leakage and contamination of
water with oil). 80% recovery of condensate means water
consumption in the boiler will be less than half of present
consumption.
Besides, much attention must be put on boiler water quality,
as it influences directly the life, performance and
maintenance requirements of the boiler. Problems of
corrosion and scale formation are also present in boiler water
with even more influence on the system life. It is of high
importance to remove oxygen and CO2 from condensate in
order to avoid corrosion. This is normally done by injecting
steam at the degasifier and by dosing some additives.
5.1.7 Use of Flow Meters
Presently, none of the measuring system or device is in use in
the process and water systems. The use of flow meters to
measure the quantities of various material and water streams
could prevent the unnecessary excessive dosing, thereby
saving the resources.
5.1.8 Wastewater Treatment
After all in-process recommendations have been undertaken,
the only way to improve the quality of the wastewater
discharge is by means of an end-of-pipe treatment.
Knowing the potential and limitations of in-house
improvements and cleaner technologies, ETPI has adopted an
approach based on both types (in-house and end-of-pipe) of
environmental solutions. The approach is two-phased. In the
first phase, cleaner production technologies (CP) will be
implemented. Once the industrial unit has stabilised the
pollution and hydraulic loads, then end-of-pipe (EOP)
treatment facilities will be designed and will be implemented
in the second phase. It is anticipated that by adopting this
strategy two benefits will be secured. These are: (a) during
implementation of CP the understanding of the management
and technical teams about the environmental problems and
solutions will improve, and (b) the EOP environmental
solutions will be much smaller and more cost effective.
In case of edible oil industries, end of pipe treatment will be
different for process wastewater and non-process wastewater.
Process Wastewater Treatment
Although process wastewater is small in quantity as
compared to non-process wastewater, but it is highly
polluted with oil and has high BOD, COD and suspended
solid. After segregation, the estimated quantity of this
stream will be in the range of 500-800 litre/ton of
production. The average values of pollutants in process
water will be:
BOD 600 mg/L
TSS 2400 mg/L
Oil 100 mg/L
The treatment will comprise of two main steps i.e. primary
treatment and secondary treatment.
Primary Treatment
The purpose of primary treatment is to remove the floatable
oil and grease and suspended solids. This will also reduce
the BOD and COD concentration. This can be achieved
either by gravity settling or by dissolved air flotation. Both
options are discussed below, and the pertinent design data
and costs are given in Table 5-2 and Table 5.3:
Table 5.2: Design Data of Primary Treatment
System
Parameter
Gravity
Settling
Tank
Chemically
Enhanced
DAF
Units
Flow 100 100 m3/day
No of Tanks 1 1 No.
Surface area 4 0.75 m2
Depth 2.5 1 m
Chemical
Mixing Tank
- 1 No.
Depth - 1 m
Area - 0.5 m2
Capacity of air
pump
- 1.5 bars
Removal Efficiencies
BOD 35 35 %
TSS 65 65 %
Oil up to 50 up to 30 ppm
Table 5.3: Cost Estimates for Primary
Treatment System
Cost In Rs.
Components
Option 1 Option 2
Screen 70,000 70,000
Civil work 60,000 40,000
Piping, mechanical & electrical
equipment
150,000 250,000
Contingencies @ 15 % 42,000 54,000
Total 322,000 414,000
Operational and maintenance
per annum
70,000 150,000
· Option 1: Gravity Settling:
The principle behind this process is the same as used by the
industry to separate water, oil and soapstock in soap pits.
The objective of gravity sedimentation or flotation is to
achieve a slow, smooth, tranquil and uniform passage of
the liquid stream from the inlet end to effluent end. During
this process the oil particles rise to the surface because of
lower density and are removed by skimming them from the
top. Suspended solids will settle at the bottom of the tank
and will be removed in the form of sludge. The details with
schematic diagram are shown in Figure 5.1.
· Option 2: Chemically Enhanced Dissolved Air
Flotation
In this process air is dissolved in the wastewater under a
pressure of several atmospheres. When the solution is
depressurised, the dissolved air is released as fine bubbles.
Additives such as aluminium and ferric salts are used to
bind the oil droplets together and in doing so, create a
structure (floc) that can easily entrap air bubbles. A few air
bubbles on a floc will rapidly buoy it to the surface.
19
In principle DAF resembles gravity settling but the surface
overflow rates are four times or even more, as the rise rate
of particles is greater with attached air bubbles. Also the oil
removal efficiency is very high in case of chemically
enhanced air flotation. The details with schematic diagram
are shown in Figure 5.2.
Secondary Treatment
The remaining oil in wastewater after gravity settling or
dissolved air flotation is in a dispersed state or in solution.
Removal of the dispersed oil and other biodegradable
organic compounds can be accomplished by biological
treatment such as activated sludge process or aerated
lagoons.
Both processes require high capital investment. Aerated
lagoons require a large area of land but operational costs
are much lower than activated sludge.
· Option 1 Aerated Lagoons
An aerated lagoon is a basin in which wastewater is
biologically treated on a flow-through basis. A large
surface area is required because of high retention time.
Oxygen is supplied by means of surface aerators. In an
aerobic lagoon most of the solids are maintained in
suspension by mixing while some of the solids settle at the
bottom and decompose anaerobically. The soluble products
of the anaerobic decomposition would, in turn, oxidise in
the upper layer of the lagoon. If groundwater pollution is
not an issue than this method will be low-cost because of
mainly earthwork construction.
· Option 2 Activated Sludge
The activated sludge process is an aerobic, biological
oxidation process in which wastewater is aerated in the
presence of a flocculent, mixed microbial culture, known as
activated sludge.
Essential elements in this process are: the aeration tank in
which the activated sludge and incoming wastewater are
thoroughly mixed (the mixture is known as mixed liquor)
and an abundant supply of dissolved oxygen is provided; a
final settling tank for separating the activated sludge from
the treated effluent; a return sludge system to recycle the
settled activated sludge solids back to the influent; and a
sludge digester.
Operationally, biological waste treatment with the activated
sludge is typically accomplished using a flow diagram such
as that shown in Figure 5.3.
Table 5.4: Design Data of Secondary Treatment
System
Parameter Option 1 Option 2 Units
Flow 100 100 m3/day
Aeration Tanks/Lagoons
No of
Tanks/Lagoons
2 1 No.
Surface area 120 20 m2
Depth 2.5 3 m
Air Requirement 47 47 CFM.
Blower / Surface
Aerator Capacity
25 25 CFM
No of Blowers /
Aerators
2 2 No
Secondary Sedimentation Tanks
No of Tanks - 1 No
Surface area - 4 m2
Depth - 2.5 m
Sludge Digester
No of Tanks 1 No.
Surface area 48 m2
Depth 6.5 m
Sludge Drying Beds
No of Tanks 2 2 No.
Surface area 12 12 m2
Depth 1 1 m
Table 5.4: Cost Estimates for Secondary
Treatment System
Cost In Rs.
Components
Option 1 Option 2
Civil work 1,660,000 900,000
Piping, mechanical & electrical
equipment
250,000 430,000
Contingencies @ 15 % 300,000 200,000
Total 2,210,000 1,530,000
Operational and maintenance
per annum
150,000 300,000
Non process wastewater
By observing good housekeeping this water can be kept
free of all pollutants, except for TDS. TDS can only be
removed by reverse osmosis (R.O), and the water can be
recycled but R.O. treatment is very expensive.
5.2 Solid Waste
Measures, which could be taken to reduce and properly
handle the solid wastes, are given in the following sections:
5.2.1 Improvement of Waste Management and
Land Filling
There are a number of possibilities available for improving
the present waste management system. The investment
involved in such improvements is limited, as many of them
are related to good working practices.
It is of the utmost importance for a food industry to offer a
clean and hygienic surrounding. In order to guarantee this,
waste management procedures should be issued out and
implemented. Furthermore, the management should ensure
that the procedures are regularly followed by workers.
The behaviour of each type of waste and the potential risks to
environment and human health differ very much, therefore,
they must be managed, stored and disposed off separately.
The control measures that can be implemented to improve
the present situation are stated below.
a) Domestic/General waste::
It is recommended that containers should be provided to
avoid uncontrolled dumping of waste inside the plant. Closed
containers should be used to prevent the spillage of waste
and to avoid odour nuisance. Furthermore, it is
recommended to increase the awareness of employees
regarding waste by arranging a certain number of short and
informal training sessions for all employees and by placing
posters in strategic places, such as: canteen, tea shop, near
the waste containers, etc.
The containers must be regularly collected and emptied at a
local landfill, to avoid over spillage and dumping of waste in
the containers’ surroundings.
b) Tin scrap:
The management for tin waste can be improved to get more
tidy and organised storage in the factory. In order to get a
better price for the recycled tin, it is recommended to avoid
mixing it with other kind of waste and avoid longer storage
time.
20
Figure 5.1: Gravity Settling Tank
Figure 5.2: Chemically Enhanced Dissolved Air Flotation
Figure 5.3: Process Flow Diagram of Activated Sludge System
21
c) Sludge from water ponds, fat traps and raw oil tanks:
· Water ponds: It is recommended to clean the water
ponds once every two months, and to dispose off
this sludge in a municipal waste landfill.
· Fat traps: It is recommended to clean the fat traps
regularly (once every 3 months). The sludge
generated as a result of this cleaning process can be
used in the soap section.
· Raw Oil Tanks: It is recommended that raw oil tanks
be cleaned every 3 months, so that the layer of
sludge at the bottom of the tank is as thin as
possible. By keeping the sludge layer thin, the
degradation of oil is minimised and the formation of
sludge is, therefore, minimised.
d) Spent earth:
Cleaning activity of the scraped earth from process building
can be simplified by installing an external vertical chute and
a storage area down the chute, so that the spent earth can be
discharged out of the building through a window and the
chute. It is recommended to cover the area where the spent
earth is piled with a simple roof to avoid getting it wet during
rains and dispersion by wind and water.
e) Spent lubricants:
Spent oil and lubricants are considered hazardous waste and
should only be sold to an authorised waste dealer, who is
responsible for its correct treatment.
5.2.2 Use of Tankers with Internal Coils to
Minimise Sludge
To avoid oil losses and to minimise sludge formation, the tank
trucks must be provided with proper insulation and internal
heating coils. This could reduce the oil losses during storage
and handling by 50 %. This reduction can be estimated as
total oil loss savings of about 0.05% of the oil processed.
Providing internal coils to tank trucks would be a difficult task
to be performed by a single mill, and it is very difficult to
force the carrier to make the investment needed for that.
However, this is something that could be discussed and done
on a sectoral basis.
5.2.3 Increased Recycling of Nickel Catalysts
Nickel catalyst is presently being recycled at a ratio of 90%
fresh to 10% recycled in some industries. This recycling ratio
is very low. Normally, edible oil mills reuse up to 80% of
recycled catalyst. It is recommended to perform some trials
with increased catalyst recycling in order to see what is the
maximum recycling ratio that can be achieved.
Another possibility for improving nickel catalyst recovery is
the use of centrifugal separators instead of filter press.
5.2.4 Recovery of Oil from Spent Earth
Oil mills are presently producing carbon oil from spent earth
by adding caustic soda and heating. This way the oil content
in spent earth is used to make a by-product, while at least
part of this oil content can be recovered as a product, i.e.
edible oil. This can be done in two ways:
· Injection of compressed air and/or steam:
Once the filtration process has finished and before the spent
earth is removed from the filter it is possible to extract some
oil by means of injecting compressed air, or steam or
compressed air followed by steam injection in the filter.
This way, oil content in the spent earth can be reduced from
40% to 30%, if only compressed air is used, and to 20%-25%
if compressed air plus steam are used. The recovered oil can
be reintroduced in the process at bleaching. Considering this
last option (with final oil content of 22%), possible savings
can be estimated to be about 0.18 ton of oil / ton of spent
earth or about Rs. 4840 per ton of spent earth, after
accounting for the money received for the oil content of earth
from the contractor.
· Solvent extraction:
By means of solvent extraction the total oil content of the
spent earth can be decreased to only 5% by weight.
Hexane is used as a solvent to extract oil from the spent
earth. The colouring substances remain in the spent earth,
while the oil is separated and is extracted forming a miscella
with the solvent.
The spent earth can be sent back to the supplier and can be
used, as a raw material for the preparation of new fuller's
earth. Hexane and oil can be separated by distillation. The oil
can be re-processed and the hexane can be stored for reuse in
future extractions.
Annual savings by industry by means of solvent extraction of
oil can be roughly calculated assuming that the oil content in
the spent earth would be reduced from 40% to 5%, thus
resulting in a 35% of oil recovery (on the total spent earth
weight). It gives a saving of about 0.35 ton of oil /ton of
spent earth which is equivalent to Rs. 13300.
Solvent extraction could also be performed for oil extraction
from spent nickel catalyst.
5.3 Soil Contamination Prevention
Prevention of soil contamination is usually a matter of good
working procedures, thus not expensive, while soil
remediation is a very costly activity.
Soil contamination near underground furnace oil deposit and
raw oil tanks can be avoided by taking care while unloading
of oil and by paving this area with concrete, providing a
proper draining system to collect spillage and rainy water
polluted with oil. Collected furnace oil can be sent to a
closed deposit to recover furnace oil and raw oil could be
used at the soapery.
For carbon oil manufacturing area it is recommended to pave
the soil with concrete and construct a cover (or a completely
closed area) to avoid rain water getting into the spent earth.
5.4 Air Emissions Control
Air emissions are of minor importance in the edible oil sector.
Following recommendations are made to reduce the
emissions:
22
5.4.1 Recovery of FFA at Deodoriser
Presently FFA and odorous volatile compounds stripped
during deodorization are condensed in a trap drum to recover
FFA. These FFA are then recycled into the soap section.
An improvement to the present situation is the installation of a
condensate recirculation, cooling and spraying system. In this
system the condensate is taken out of the trap drum, cooled in
a plate heat exchanger with water and sprayed back inside
the trap drum to increase the FFA recovery, which will act as
a kind of scrubber. Most of the distillate is condensed and
recovered in this way.
5.4.2 Recovery of CO2 from Gas Cracking Plant
In some industries, CO2 that is formed at the cracking plant is
released in the air. Normally, edible oil mills recover this
CO2 and confine it into cylinders to be sold to other
industries. According to the information received from other
mills, it is profitable enough to payback the initial
investment.
5.4.3 Optimisation of Combustion at Boiler
A monitoring system for the exhaust gases is required to
optimise the combustion process. It is recommended to
monitor O2, CO and temperature. By monitoring O2 and
temperature and controlling combustion according to the
measured values it is possible to optimise combustion. For
this purpose, measuring equipment connected to a control
device should be installed.
This will avoid having too little air during combustion (lack
of oxygen), and thus high values of CO and unburned
compounds (low combustion efficiency) and will also
avoid too much air into the boiler, which means that the
heat is blown out of the boiler and, therefore, lost.
It is also important to measure CO. Concentrations of CO
above 0.1% v-v are dangerous because of an explosion risk.
Modern boilers are provided with a CO measuring device
connected to an alarm and emergency stop system.
There are more refined methods to optimise combustion, as
low NOx emission burners, but these can be considered once
the basic improvements have been made.
5.5 Safety and Health (S&H)
Some recommendations about S&H have been developed
and are presented below:
5.5.1 Exhaust Combustion Gases out of Gas
Cracking Building
In the cracking unit, natural gas is burned inside the gas
cracker to provide the necessary heat for cracking reaction.
The exhaust gases coming from the natural gas combustion
are evacuated at the top of the gas cracker inside the building
and thus affect the working conditions. It is recommended
that a stack be installed that takes the exhaust gases outside
the building.
5.5.2 Improvement of Noise Abatement and
Protection
There are three main measures that can be taken in order to
minimise noise nuisance to workers:
· Use of equipment with low noise emission level: new
equipment and machinery are designed to have low
noise emission level. Noise should be taken into account,
as additional requirement for suppliers, when purchasing
new machinery.
· Installation of noise insulation/barriers: noisy equipment
must be insulated as much as possible. For this, physical
barriers and building insulation are the common
procedures.
· Protection of workers: in those areas where it is not
possible to reduce the noise below reasonable levels, 80-
85 dB(A), employees should wear protective gears, ear
plugs/muffs being the most common, and have
periodical medical reviews.
Prior to taking any actions it is recommended that a noise
study, with measurement of noise levels in all places where
high noise values are to be expected, be undertaken.
5.5.3 Improvement of Working Conditions at the
Tin Shop
Following recommendations can be made to improve the
working conditions of workers at the tin shop:
· Provide them with appropriate gloves to avoid injuries
caused by the sharp tin foils.
· Provide employees with welding goggles when working
in spark welding section.
· Provide the tin shop building with forced ventilation to
improve inside air quality.
· Provide employees with masks when working in melted
tin welding section.
5.5.4 Use of Material Safety Data Sheets (MSDS)
of Raw Products
The MSDS contain information such as a complete list of
risks of the product, as well as indications about how to
proceed in case of any incident/accident that may occur.
These sheets are very useful for industrial customers to take
proper measures when storing, handling and using the
product. Furthermore, the MSDS can be used to make
working instructions for workers about storing, handling
and use of products.
5.6 Energy
There are good possibilities for increasing efficiency in the
use of energy in edible oil mill. Any improvement in energy
efficiency has the following advantages:
· Savings of money, as less natural gas or electricity is
consumed.
· Savings of limited natural resources, as the fuels required
to produce the saved energy will be saved too.
· Air emission reduction, as less natural gas will be burnt.
Some recommendations for improvement in energy efficiency
are discussed in the following sections.
5.6.1 Recovery of Heat from Cooling Water Used
during Hydrogenation
Hydrogenation is an exothermic reaction, therefore, cooling
water is required to keep the temperature under control.
By using boiler quality water at the cooling system of the
autoclave, it is possible to send the outlet of the cooling water
to the feed water tank of the boiler. In this way, the energy
content of the hot water can save natural gas and money.
23
The amount of natural gas that can be saved per ton of boiler
feed water (at 90°C instead of normal intake water
temperature of 30°C) is approx. 7.6 Nm3.
5.6.2 Pre-heating of Incoming Oil with Outgoing
Oil at Hydrogenation
Oil is heated up with steam before hydrogenation, and is
cooled down with water after hydrogenation. This results first
in energy consumption and wastage afterwards.
There is a more efficient way to perform the same process i.e.
heating incoming oil with outgoing hydrogenated oil, as
shown in Figure 5.4. The installation is provided with a steam
heater placed after the oil-oil heat exchanger to supply any
additional required heating. The same is done with the
hydrogenated oil, by placing a cooler after the oil-oil heat
exchanger to cool it down further. This would also reduce the
amount of cooling water required.
Assuming the temperatures that are shown in the figure,
approx. 6 % of total annual natural gas consumption and
approx. 2% of total annual water consumption can be saved.
The cost of a plate exchanger of this characteristics is around
Rs 350,000, plus installation cost (piping, valves, etc.), which
means that the investment would have a payback period of
less than 12 months.
Figure 5.4: Proposed system for Pre-heating of
Incoming oil with outgoing oil at Hydrogenation
5.6.3 Pre-heating of Incoming Oil with Outgoing
Oil at Deodorization
The same system that has been described for hydrogenation
can be used for deodorization.
Assuming the temperatures that are shown in the figure
approximately 7% of saving on annual natural gas
consumption and approximately 5% of total water
consumption can be saved.
5.6.4 Improvement of Steam Pipes Insulation
The steam distribution system needs to be properly insulated.
Pipes without insulation or with partly damaged insulation
result in energy losses, which means not only loss of
valuable resource but also higher air emissions than
necessary.
5.6.5 Increasing Temperature during
Deodorization
It is recommended to perform deodorization at 235-245oC
to reduce the process duration as well as oil losses during
deodorization.
5.6.6 Installation of a Cogeneration Plant
Producing electricity by means of cogeneration plants has
several advantages, both economical and environmental,
not only for the industry, but also for the country. Some
advantages for the industry include:
- A cogeneration plant is the most efficient way at the
moment to produce energy, as heat and power generated
are near the facility and both are used in the process. This
means a reduction in the energy cost for the industry.
- With cogeneration, the industry has a secure power
source, avoiding stops in production due to power failure.
In this case, the power from the grid is only consumed in
case of failure or maintenance stop of the cogeneration
plant.
- Normally the heat requirements exceed the power
requirements of the factory, there is generally a surplus
electricity which can be sold to nearby industries,
translating into extra income for the company.
- Energy efficiency of cogeneration means savings of
limited natural resources (fuel) of the country.
- Energy efficiency means less air emissions due to less
fossil fuel combustion.
The main disadvantages of a cogeneration plant are the large
investment cost and the intensive maintenance care required
for them.
The two main schemes of a typical cogeneration plant are:
a) Cogeneration with gas turbine
b) Cogeneration with an alternative motor:
In principle, according to energy requirements of different
processes, cogeneration with alternative motors is more
suitable than with gas turbine.
Provided that the industry is allowed to sell surplus
electricity to nearby industries, the typical payback period for
cogeneration plants is between 3 to 5 years. Investment cost
of a cogeneration plant, using alternative motors, can vary
from Rs 30,000 to Rs 35,000 per installed kW.
5.7 General Recommendations
Some recommendations for an overall improvement in the
processes which would subsequently improve the quality of
products and working environment, are discussed below:
150OC
HYDROGENATION
TANK
Steam
170OC
Heat
Exchanger
90OC
100OC
90OC
90 OC 30 OC
Cooling
Water
Filter
Press
160OC
Hydrogenated Oil
Incoming
Oil
To Post-
Neutralization
24
5.7.1 Inert Atmosphere after Deodorization
When the deodorised oil is subjected to the de-cooler which
is not maintained with inert atmosphere (absence of
oxygen), oxygen from air enters the oil and facilitates
oxidation reactions causing formation of odoriferous
compounds. Therefore, it is recommended to have N2
blanketing after deodorization till filling and packing which
will result in prolonged stability and taste of the finished
product. It will also result in the reduction of the moisture
content entrained in the oil.
5.7.2 Covering of Lye Preparation Area
Lye to be used in pre- and post-neutralisation is prepared in
some tanks placed on the ground floor, manually by skilled
employees. These tanks are not covered to provide protection
from the sunlight, rain-water, or harsh weather. Adverse
weather conditions can affect their capability to prepare a
good lye, thus affecting the quality of the neutralisation
process. Moreover, this method of handling poses serious
occupational health and safety dangers.
For this reason, it is recommended to cover this area. An
investment of a few thousands rupees will improve the lye
preparation conditions.
It is also recommended that the management should arrange
for proper information dissemination through posters etc.,
indicating standard working instructions in the area.
5.7.3 Insulation of Chilling Room's Doors
In chilling rooms the final product is stored before dispatch.
These chilling rooms are insulated to avoid heat transmission
and to save energy, but in some industries the doors of the
room are normal wooden doors. A minor improvement, with
a little cost, would be to provide the chilling rooms with a
double foiled door with an inner chamber, between 2 foils of
wood, filled with insulation material.
The investment required for providing the chilling rooms with
insulated doors would be promptly paid back by means of
energy savings.
5.7.4 Environmental Management Systems (EMS)
It is time for the Pakistani industry to start considering
environmental management aspects into the general strategy
and management of companies. First steps that could be
taken in this regard are:
· Identification of all environmental impacts of the
industry
· Collection of legislation that affects the company
· Comparison of environmental situation of the
company with the legislation and, if necessary,
identification of measures to improve the
environmental situation and to comply legislation.
· Implementation of measures to improve the
environmental situation and to comply with legislation.
· Awareness of top management of the company about
the importance of environmental aspects in terms of:
- Image and reputation of the company
- Elimination of potential risks for the company
(fines, court actions, etc.)
- Impact on business of accidents and failures
- Cost savings as a result of better environmental
performance
- Competitiveness
- Jumping over international trade barriers based
on environmental performances, etc.
· Appointment of an environmental manager or coordinator
· Training and awareness improvement of all personnel,
so that environment becomes a new aspect to be
considered in any decision making process (design of
new products, changing of processes or utilities,
changing of legislation, etc.)
Consideration of all these points is the first steps for the
introduction of environmental management as a part of the
general management programme of the company. A further
step is to organise everything into a system, which means to
start the implementation of an EMS (according to ISO or any
other official standard).
References
1. A. Karleskind, Oil and Fats Manual, Volume 1,
184, (1996)
2. B. Braaee, J. Am Oil Chem. Soc. 53, 353 (1976)
3. D. Barnes, P. Bliss, B. Gould and H. Vallentine,
Water and Wastewater Engineering Systems,
Pitman (1981)
4. D. Gunn and R. Horton, Industrial Boilers
(1988).
5. E. R. Sherwin, J. Am. Oil Chemists Soc., 55, 809-
814 (1978)
6. E.A. Avallone and T. Baumeister III (eds.) Marks
Standard Handbook for Mechanical Engineers,
9th Edition (1987).
7. Encyclopedia of Chemical Technology 3rd
Edition, John Wiley & Sons, pp 728, (1983)
8. G.T. Austin, Shreve’s Chemical Process,
Industries, 5th Edition McGraw-Hill Book Co.,
New York (1962).
9. J. Davidson, E.J. Better, A. Davidson, “Soap
Manufacture” Volume - 1 Interscience
Publishers, Inc., New York.
10. J.W. Bodman, E.M. James, and S.J. Rini in K.S.
Markley, Ed., Soyabeans and Soyabeans
Products, Volume - 2, Interscience Publishers,
Inc., New York, 1951, Chapter-17.
11. J.W. E. Coenen, J. Am. Oil Chem. Soc., 53, 382
(1976)
12. L.I. Pinkers, Practical Boiler Water Treatment,
Including Air Conditioning Systems (1962).
13. McGraw-Hill Encyclopedia of Science &
Technology, 7th Edition (1983).
14. Metcalf & Eddy, Wastewater Engineering,
McGraw-Hill, 3rd edition (1991).
15. Moe, Chemical Engineering Program, 58 (3), 33
(1962).
16. Tomas H. and Applewhite in Baily’s Industrial
Oil and Fat Products, Volume - 3 4th Edition
Wiley-Interscience, New York, 1982, Chap-4.