Copra Extraction Meal
|Infobox on Copra Extraction Meal|
|Example of Copra Extraction Meal|
|Origin||This Table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.|
|Stowage factor (in m3/t)||2.0 - 2.3 m³/t|
|Angle of repose||-|
|Humidity / moisture|
|Oil content||0.1 - 1.5%|
|Ventilation||Copra extraction meal requires particular temperature, humidity/moisture and ventilation conditions.|
Recommended ventilation conditions: surface ventilation.
|Risk factors||Copra extraction meal readily becomes rancid.|
Copra extraction meal is liable to the risk of self-heating/spontaneous combustion.
Copra Extraction Meal
Coconut Oil is obtained by extracting the oil contained in copra. The residue is generally called copra cake, sometimes it is called copra meal. Coconut oil is used for food and for industrial purposes. Edible oil, by international standards should have less than 0.1% free fatty acid content. The oil obtained from good quality copra, with a free fatty acid content of < 0.1%, is used as cooking oil without any further processing. Even if the free fatty acid content is 3-5%, the international standard of < 0.1% can be obtained by refining and deodorizing. Edible oils are either used as cooking oil (frying oil) or processed further into filled milk, table margarine and baker's margarine.
In industry, coconut oil is used for manufacturing toilet and laundry soap. In its original or modified form, it is used as a vehicle in the paint and varnish industry. Coconut oil is also processed into methyl esters, Fatty Acids and fatty alcohols. These intermediate products are raw materials for manufacturing detergents, surfactants, emulsifiers, plasticizers and various other organic products which are bio-degradable. Copra cake is used in blending animal feed.
Expellers are the residue from processing by the continuous screw process, with an oil content of between 1,5-7%, but sometimes more if old machinery has been used.
Extractions are the residue after solvent extraction of the oil, the remaining oil content is >1,5%. Usally in the form of regular grain-sized pellets.
Extraction Technology, Dry Processing:
Oil extraction from copra is carried out by two methods: mechanically by pressing; or by use of solvents. Mechanical and solvent extraction uses standard technology that has been developed in the vegetable oil industry. For Oil Seeds such as copra which have a high oil content, mechanical extraction is efficient and economical. For oil seeds with low oil content or for further oil extraction from copra cake, the solvent extraction method is more suitable. The residual material from solvent extraction is called copra meal. Oil extraction involves five basic steps: copra storage; preparation of copra; oil extraction - full press, prepress - solvent, and full solvent methods; processing of extracted oil; processing of cake or meal and storage of products.
Full press method:
In the full press method of oil extraction, maximum pressure is applied to the material and sufficient time is allowed for the oil to escape. The temperature of the material should not be allowed to rise to a level where the oil darkens due to overheating. The pressure is applied to the material between the screws and the cage of slitted steel bars. Pressing may be done in a single or in double stages. By adjusting the clearance in the choking device, the thickness of the cake can be controlled. When the clearance is reduced to decrease the thickness of the cake, the pressure applied is increased. To prevent overheating the oil, the shaft is usually hollow for water cooling, and the oil is sprinkled over the cage bars.
In the prepress-solvent process, the oil is partially extracted by preliminary low pressure mechanical extraction, and then subjected to solvent extraction to remove most of the residual oil. The oil content of the initial copra material is around 70%; after the mechanical prepress extraction, the residual oil content in the prepressed cake is 16 - 20% for optimum operation. After full press extraction, the oil content in the residual copra cake is 6 - 10%, depending upon efficiency. The equipment used for prepressing is similar to expellers used for full pressing, but adjusted for less pressure and therefore it has a higher throughput.
Full solvent method:
In solvent extraction, oil in the material is leached with a solvent (where the oil dissolves in the solvent) whereas the insoluble meal is retained unaffected. The extent of extraction depends upon the kind of solvent, the temperature of solvent, the ratio of solvent to meal, the number of extraction stages, the shape of particles, the porosity of the material, and the contact duration. The most common solvent used is Template:Hexane because of its price, low toxicity, suitable boiling point for recovery and handling, and its availability. Solubility of oil in hexane increases with temperature.
The resulting streams from solvent extraction are: the micella or oil, solvent solution, and the extracted meal which comprises the meal, some solvent and a little residual oil. The solvent in the meal is removed by heating to boil off the volatile solvent, and the solvent is recovered by condensation. The solvent from the micella is removed and recovered by evaporation and condensation. Traces of solvent left in the meal and the oil are removed by steam-stripping under reduced pressure.
The equipment for solvent extraction consists of two general types; the roto-cell type with cells revolving around a vertical axis, and the basket type with baskets travelling horizontally while the solvent is sprayed over the material in counter-current flow. In the full solvent process, the prepared copra is first subjected to a first extraction (percolation), using the weak micella from the second extractor as starting solvent, and producing the strong micella for oil recovery. The extracted meal is then flaked and subjected to a second extraction (immersion) which uses fresh solvent as starting solvent and produces the weak micella solvent for the first extractor. The solvent with the extracted oil is removed in a Desolventizer-Toaster (DT) which is either of the multi-decked vertical design with steam heated pans and paddle scrapers, or the horizontal barrel type with rotating conveying paddles attached to a horizontal shaft, and steam jacketed walls. These are equipped with condensers for solvent recovery and scrubbers to remove dust entrained in the vapours. In some designs, the heat with the vapours leaving the DT is used to pre-concentrate the micella prior to evaporation of the micella.
The solvent with the micella is recovered, first by an evaporator, usually of the falling film type, where hexane is distilled off by indirect steam heating, and subsequently by a stripping column where traces of hexane in the oil are stripped by steam under vacuum. The water-hexane vapours from the stripper are condensed and collected in a water-hexane separator where hexane is separated by gravity from the water. It is decanted and reused in the extraction. Vent vapours of hexane from the extractors and condensers are recovered in a vent recovery system where hexane is absorbed by mineral oil. Hexane is recovered from the mineral oil by stripping, and recycled to the extractor.
Processing extracted oil:
Processing the extracted oil is the next basic step in the oil extraction technology. Oil from the expellers contain substantial quantities of solids (foots) that should be removed before the oil is pumped into the storage tanks. The oil is cleaned first by settling and screening and subsequently by filtration. The screening equipment is a rectangular steel tank equipped with a continuous drag chain conveyor with scraper blades, which scoop the settled solids and lift them over a fine screen for drainage at one end of the screening tank, after which they are conveyed back to the expellers to be mixed with the copra. The filtering equipment generally consists of a plate and frame filter press with canvass filtering media. Some factories use leaf filters with perforated steel filtering leaves. The foots or filter cake from the filters are recycled to the expellers for oil extraction. The oil from solvent extraction is free of solids. It leaves the stripping column at 120°C and is cooled and pumped into the storage tanks through an oil meter.
Processing cake or meal:
Copra cake leaving the expellers has a temperature of about 110 °C and is cooled in a cake cooler. The cake cascades down the cooler baffles and is cooled by a cross-flow of cooled air from blowers. After cooling, it is ground to fine particles by hammer mills or disc mills. The ground cake is bagged for local use or pelletized for export. Pelletizing requires additional equipment which small plants cannot afford. However, cake or meal for export has to be pelletized for safer and easier handling and conveying. Prior to pelletizing, the cake has to be moistened to about 12% moisture and then fed to the pellet mill. Moistening in this manner improves pelleting property, and is required for export. The oil content of copra cake should be around 6 to 10% and moisture not higher than 12%. For Copra Expeller, the oil content is approx. 1,5-7% and for copra meal 0.5 - 1,5% depending on the efficiency of solvent extraction. Due to absorption, the moisture level rises during storage.
Storage of products:
The unpelletized copra cake should be bagged in woven sacks and stacked about 10 high on wooden pallets. It is hazardous to store unpelletized cake in bulk for long periods. The piles of unbagged meal should be kept small and turned over as frequently as necessary to prevent spontaneous combustion.
The (hot) finished expellers leave the production plant with a variable moisture content. After pressing, the expellers are cooled and, since they are in large pieces, they are ground and adjusted to a water content suitable for storage and transport. The ground products are then held in intermediate storage in silo cells or sent for transport.
Copra cake/expeller/meal is used as an ingredient in blending animal feed, due to the presence of oil, protein and carbohydrates. Copra cake from poor quality copra has a limited market due to its degraded condition and the presence of aflatoxin.
Upon shipment, the copra produce should be accompanied by certificates stating the moisture, residual oil content and the maturing time of the product. It should also be stated that the product really is expeller and not extraction meal (extracting agent/solvent content). Oil contents of < 1.5% are indicative of extraction meal.
Overheating during the production process, or subjecting the product to pro longed storage, may be manifested by brown or reddish to black discoloration. Expeller/Extraction meal is mainly transported as bulk cargo.
Favorable travel temperature: 5 - 25°C.
At elevated external temperatures, the product temperature must be no more than 10% higher than the external temperature.
In tropical ports, temperatures of 25 - 55°C may occur in the products to be loaded.
If the cargo temperature during the voyage rises to >55°C and any further increase is observed, adequate measures must be taken, e.g. tight closing of all hatch openings and injection of CO2 or inert gas may have to be considered.
Stow away from heat sources (i.e. engine room bulkheads, heated fuel tanks, etc.).
- Self-heating / Spontaneous combustion
- Toxicity / Hazards to health
- Insect infestation / Diseases
Note: Reference is made to the relevant IMO regulations on hazardous cargo.