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Post on 07-Nov-2014
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CHRISTU JYOTI INSTITUTE OF TECH.& SCIENCE(YESHWANTAPUR, JANGOAN, WARANGAL, AP)
PROJECT REPORT Topic: Rice bran oil extraction process Industry Sri venkata narasimha solvent oil extraction plant (nakkalapelly,shambunpet, warangal, AP) STUDENT NAMES CH.NAGESH(08681A0314) SYED.MINHAJ MOHSIN(09685A0305) MD.LIYAKHAT HUSSAIN(09685A0302) L.VENUGOPAL(08681A0328)
K.MANOJKUMAR(08681A0321)K.KRISHNA REDDY MANAGING DIRECTOR, (SREE MAHA VENKATA NARASIMHA SOLVENT OILS PVT.LTD.)
SOLVENT OIL EXRACTION PROCESS
INTRODUCTION Solvent extraction is basically a process of diffusion of a solvent into oil-bearing cell of the raw material, resulting in a solution of the oil in solvent. Various solvents can be used for extraction. However ,hexane is considered to be the best it is exclusively used for the purpose.
In a nutshell, the extraction process consists of treating the raw material with hexane and recovering the oil by distillation of the resulting solution of oil in hexane called miscella. The hexane absorbed in the material is recovered by evaporation and condensation as also from the distillation of miscella. The hexane thus recovered is reused. The low boiling point of hexane (67 C) and the high solubility of oils and fats in it are the properties exploited in the solvent extraction process.
The entire extraction process can be divided into the fallowing stages. 1. Preparation of raw material. 2. Process of extraction. 3. Desolventisation of extracted material. 4. Distillation of miscella. 5. Solvent recovery by absorption 6. Meal finishing and bagging.
Because of the highly inflammable character of the normal hexane , those stages of process which involve high speed machineries, such as material preparation. Finishing and bagging are carried out at 50 feet away from main plant, where the remaining processing stages involveing handling of the solvent are carried out.
PREPARATION OF RAW MATERIAL
For thorough and efficient extraction, it is necessary that each and every oil-bearing cell of the material is brought in contact with the solvent. Therefore, proper preparation of materials prior to extraction is very important to ensure this contact. The smaller the material size, the better is the penetration of the solvent into the oil-bearing cells, but too fine a size will prevent the solvent from percolating trough the mass. Therefore an optimum size is to be maintained for better extraction. Hence material preparation methods vary from material depending on its oil content, size and physical properties.
For high oil content material (oil content 15% or more), the fallowing steps of preparation are recommended to make the material suitable for penetration of the solvent into the cells as well as for best percolation. 1. Passage of the seed through corrugated roller mills with 3 mm flutes to reduse the size to about 3mm. 2. Heating the broken material to about 80C with open steam in a temperor and humidifying the material to raise the moisture content to about 11 to 12%. 3. Flaking of the humidified material between a pair of plan rolls to 0.25mm thickness or below. 4. Conveying the flakes to the extraction system after crisping them firm.
Rice bran is a fine floury material and therefore is bound to abstract the percolation. The best preparation of rice bran for extraction is found to be palletizing the same after tempering with open steam. The palletized bran is then crisped in a current of air while conveying to extractor. Some oilseeds can be directly extracted e.g.cottenseed, Soya been, etc. but they are to be decorticated by special equipment to separate the oil-bearing meats from the hulls. The decorticating equipment varies from seed to seed. The decorticated meats are tempered, flaked and the flakes are sent to extractor after crisping.
PROCESS OF EXTRACTIONThe prepared material enters the extractor through the rotory air seel. The extractor consists mainly of a very slow moving articulated band conveyor inside a totally enclosed chamber. The band is lined with perforated sheets and porous stainless steel cloths. The mass of the material moving on this band forms a slow moving bed.During the movement of the bed through the extractor it is washed continuously at various points with miscella of decreasing concentrations and finally with a fresh meal bed. The miscella percolates through the perforated bottom and collects in various hoppers kept below the bed. The miscella from the last hopper that is concentrated is taken off for distillation.
DESOLVENISATION OF EXTRACTED METERIAL
After the fresh solvent wash the material is discharged from the band conveyor into an airtight chain conveyor, which conveys it to the disolventiser. In the desolventiser the material is heated to about 100 C by jacketed steam, and thus the absorbed solvent is evaporated into vapors . Finally, the material, which is now completely desolventised, is continuously discharged through rir tight into a pneumatic conveyor, which carries into the bagging section. The vapors evolved in the desolvenisers are led through a dust catcher wherein they are washed with hot water, to a condenser.
Some material. Such as cottonseeds and Soya been extractions or toasted after desolventisation. In those cases both the steps of desolventisation and toasting can be combined into one operation by the use of desolventisation-toaster (D.T) instead of the tubular-jacked desolventiser . The D.T consists of a vertical cylindrical vessel with horizontal jacketed compartments and a central rotating vertical shaft on which are mounted sweeps in each compartment. The material to be desolventised and toasted is fed in to top compartment of D.T and heated with open steam.
open steam condenses a lot of moisture in the material at the same time evaporating the solvent. The moisture up to 14 to 15% is condensed. The material then flows to lower compartment. In lower thus evaporating all the solvent, cooking in presence of moisture destroys undesirable enzymes. High temperature attained toasts the material. The solvent and water vapors from various compartments hot water spray to remove fine dust and then led to a condenser to condense the vapors. The desoventised and toasted meal from compartment discharges into a redler conveyor. bottom-most
DISITILLATION OF MISCELLThe final miscella (solution of oil in hexane) obtained from the extractor is collected in a tank from where it is pumped to distillation column kept under vacuum by means of a series of steam ejectors. The miscella is heated by jacket steam in the distillation column and thus the hexane is turned into vapor immediately. The vapors are led to another condenser through an entrainment separator.
The concentrated miscella from the evaporator is pumped into a similar secondary distillation unit to raise the temperature to about 100= 110 C and then into the final stripper kept under high vaccum. Opne steam is injected in the latter to strip the last traces of hexane from the oil freed from solvent is pumped from the stripper to the storage.
SOLVENT ROCOVERY BY CONDENSATION All the condensers are of floating head type with tube bundles to carry the cooling water. The cooled water at 30 C or below is calculated inside the tubes in all the condenser and the vapors are passed outside the tubes. Thus the vapors are cooled and condensed into liquid. The uncondensed vapors from each condenser are sucked by a series of ejectors and pushed through the last condenser to a contact cooler where they are washed with cold-water spray.
All the condensate liquid hexane + water from these condensers and contact cooler is led to a solvent water separator where in the pure solvent is separated from water by settling the difference in densities of water and the solvent and their immiscibility accomplished complete separation.The fresh pure solvent from this tank is pumped to the extractor continuously for the final washing of the meal bed.
FINAL SOLVENT RECOVERY BY ABSORPTIONThe vapor and gases from the contact cooler are led to absorbers where they come into intimate contact with absorbing oil (vegetable oil or mineral oil). The solvent vapor if any are absorbed in this oil and no condensable gases are let out into the atmosphere. While theoretically these gases leaving the plant are expected to be free from hexane, in practice a small amount of the solvent is lost with those gasses.
The oil containing the absorbed solvent is led into an evaporator kept under vacuum and heated to 100 C. the solvent is vaporized and these vapors are led into one of condensers and recovered.The hot oil from the evaporator is passed through a hexane it is sprayed back into the absorber.
MEAL FINISHING AND BAGGING
The redler conveyor carries the desolventised meal from the DT to bagging section. The meal is not only conveyed but also cooled to a about 45-50C by means of cold air draft induced in the conveyor by a blower. The meal drops to humidifier from the redler.
In the humidifier the meal is mixed with enough moisture to bring in the moisture content, thus replacing the amount of water lost during the extraction and desolventisation steps. The humidified meal is the bagged at the discharge of the humidifier.