|EP3 - Pollution Prevention Assessment for an Olive Oil Extraction and Soap Manufacturing Facility||A developing country||1993||CP Audit|
MANUFACTURE OF CHEMICALS AND CHEMICAL PRODUCTS # 1
This facility extracts and refines oil from spent olive oil pressing waste (grignon) for sale as consumable oil. Any oils that cannot be used for consumption are used in the manufacture of soap. The facility operates three eight-hour shifts, employing eighty permanent workers and eighty seasonal workers. Sales exceeded $ 2.6 million during 1992-1993 operating season.
The facility is the only company in the area that extracts olive oil from grignon. It represents approximately 30 percent of the national market for oil seed refining and sells about 15 percent of the nation's bar soap used primarily for clothes laundering.
The cleaner production initiatives were undertaken under the Environmental Pollution Prevention Project (EP3) sponsored by the United States Agency for International Development (USAID).
Cleaner Production Principle
Process modification; Housekeeping; New technology, Recovery, Reuse and Recycle; Material substitution
Cleaner Production Application
Overall, the assessment identified 13 pollution prevention opportunities that could provide first year savings of $ 420,000 (US) for a one-time investment of $ 236,000 (US). If implemented, these changes could reduce energy and water use per unit output, reduce contaminated wastewater, and improve product quality.
The plant has five main unit operations: grignon drying, oil extraction, recovery of hexane, oil refining, and soap making (a detailed process flow chart is available from the EP3 Clearinghouse).
Each day, raw grignon is ground and dried in three large hot air rotary dryers to 7 percent moisture before the extraction process begins. The plant operates two systems of six 13-ton extractor/desolventizer vessels. Each system uses three tanks at a time in series for oil extraction. The grignon is placed in the tanks, and an un-metered amount of hexane is added through the top of the first tank. It extracts oil as it percolates through the grignon. The mixture of hexane and olive oil (called miscella) flows to fill the second tank, overflows, and then fills the third before going to temporary storage to await separation.
The miscella drains from the extractors and is pumped to the evaporators. The evaporators use non-contact steam to evaporate the hexane from the mixture.
The neutralization process separates the oil from the waste, called "soap stock." The neutralized oil is then decolorized and deodorized. The refined oil is sold for consumption.
Oil of insufficient quality for refining and the soap stock from the neutralizing step in refining and the soap stock from the neutralizing step in refining are used as feed for soap making. In large, steam-heated cylindrical tanks, oil and/or soap stock mix with sodium hydroxide, salt, and a variable amount of water, reacting to form a soap that floats on top of the tank. The wet soap is filtered, steam heated, and vacuum dried. The soap next passes through a high-shear mixing machine to an extruder where it is cooled and molded into a continuous rectangular solid. The soap bar is cut, inspected, dried, and boxed for shipment.
Existing Pollution Problems
At the time of the assessment, there were a number of pollution problems at the facility, including : (1) excessive hexane emissions during oil extraction, (2) particulate and NOx emissions from boilers, (3) fire hazard from dried grignon, (4) excessive waste water from hexane evaporation, (5) oil loss to the water stream, and (6) excessive fatty acids dumped directly into the sea.
Pollution Prevention Opportunities
Overall, the assessment identified 13 pollution prevention opportunities that could provide first year savings of $ 426,000 (US) for a one-time investment of $ 236,000 (US).
The predicted savings could rise dramatically by including the avoided capital costs for a waste water pre-treatment station designed for pre-assessment operating conditions. Below is a list of pollution prevention opportunities in order of unit operation processes.
Summary of Recommended Pollution Prevention Opportunities
|Grignon Drying -- Leave 12 percent residual moisture instead of the current 7%|
|Oil extraction : Hexane washing--purchase and install a heat exchanger to pre-heat the gringnon and hexane to 60 oC -|
|Oil extraction : Hexane Distribution -- Design build and install a hexane distribution manifold for each extractor|
|Oil extraction : Control hexane feed rate -- purchase and install flow meters for each extractor|
|Oil extraction : Vapor vent condensing -- Purchase a shell and tube condenser to maintain a negative pressure (vacuum) on the system|
|De-solventizing Grignon : Steam measuring : Purchase and install flow meters and pressure gauges|
Miscella Distillation :
|Deodorization purchase and install two shell and vacuum condensers|
A number of the recommendations can help the facility produce superior oil for consumption, including (1) cooling the oil from the oil/hexane Stripper, (2) adding process flow meters and controls in the refining stage, and (3) upgrading equipment in the deodorizing process.
The facility has appointed a follow-up team that is working under the supervision of the local EP3 office and a specialized local consultant in order to implement the assessment's recommendations. After setting priorities relative to the implementation plan, actual execution began. The follow-up team is conducting experiments to determine the most suitable way of obtaining 12 percent moisture level in the dried grignon and whether such a moisture level yields the desired results, for both oil extraction and combustion purposes. Two shell-and-tube heat exchangers have been purchased to pre-heat hexane (before extraction) to 60 oC and are scheduled for installation by the end of September 1994. The follow-up team is screening for appropriate flow meters and pressure gauges to ensure better measurement and control of its production operations. The facility has also purchased two NIAGARA filters to reduce the volume of waste water and hexane losses in its deodorizing operation effluents.
Environmental and Economic Benefits
A option-wise summary of the implementation costs and anticipated benefits is provided below.
|Grignon Drying -- Leave 12 percent residual moisture instead of the current 7% reduces hexane emissions from extraction and particulate and NOx emissions from boilers.|
|Oil extraction : Hexane washing--purchase and install a heat exchanger to pre-heat the gringnon and hexane to 60 oC - reduces hexane emissions. The implementation costs are $12,000 (US) with a financial benefit of $213,000 (US) combined and a payback period of 3 months.|
|Oil extraction : Hexane Distribution -- Design build and install a hexane distribution manifold for each extractor reduces hexane emissions. The implementation costs are $24,000 (US) with a financial benefit of $213,000 (US) combined and a payback period of 3 months.|
|Oil extraction : Control hexane feed rate -- purchase and install flow meters for each extractor - reduces hexane emissions. The implementation cost is estimated at $14,500 (US) with a financial benefit of $213,000 (US) combined and a pay back period of 3 months.|
|Oil extraction : Vapor vent condensing -- Purchase a shell and tube condenser to maintain a negative pressure (vacuum) on the system - reduce hexane emissions. The implementation cost is $7,000 (US) with a financial benefit of $213,000 (US) combined and a payback period of 3 months.|
|De-solventizing Grignon : Steam measuring : Purchase and install flow meters and pressure gauges - reduces hexane emissions. Implementation cats of $15,500 (US) with a financial benefit of $21,000 (US) combined and a payback period of 1.5 years combined.|
Miscella Distillation :
|Deodorization purchase and install two shell and vacuum condensers - reduces fatty acids dumped into the sea. Implementation costs of $29,000 (US) and financial benefit of $6,000 (US) and a payback period of 5 years.|
Recommendations made to help the facility to produce superior oil for consumptionare expected to reduce waste water volume by nearly 50 percent, lower the COD level, hydrocarbon loading, and the amount of solids in the waste water. These changes could help the facility improve its competitiveness in the domestic and export markets.
If implemented, these pollution prevention improvements will reduce hexane emissions to the atmosphere and to waste water by over 160,000 kilograms; reduce waste water volume by 96,000 cubic meters per year; reduce particulate and NOx emissions; and reduce the risk of fire or explosion from hexane.
This case study was carried out in a developing country in which EP3 has an established Program. It was submitted to UNEP IE and edited for the ICPIC diskette in August 1995.
Subsequently the case study has undergone a technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.