Any oil bearing material can be extracted by solvent extraction plant with proper preparation of raw material before feeding to the extraction process. Solvent extraction process is an Universal process of extracting vegetable oil from rice bran, soya bean etc. It is the most popular used oil extraction method. In the earlier times, rice bran was used as either fertilizer or animal feed. But in these days, it is used for extraction of oil namely rice bran oil (RBO). The most successful countries producing rice bran oil are India and Thailand. In India, about 6.5 lakh tons of rice bran oil is produced from 40 lakh tons of rice bran by solvent extraction process. The rice bran layer contains 20% oil and considered as richest oil sources among the grain by-products. Rice Bran Oil is a unique vegetable oil produced from the outer brown layer of rice which is removed in the form of rice bran during the polishing process of the rice milling Industry. Besides having an almost ideally balanced fatty acid profile, it is rich in natural anti-oxidants. All these studies have attributed these properties of the oil to the presence of unique nutraceuticals in this oil known as oryzanol & tocotrienols. Rice bran oil is the world’s healthiest edible oil, containing vitamins, antioxidants and nutrients. Rice Bran Oil is extensively used in Japan, Korea, China, Taiwan and Thailand as premium edible oil. It is the conventional ; the most favorite cooking medium of the Japanese and is popularly known as “Heart Oil” in Japan. Humans have been enjoying grain foods from past thousand years. Grain foods including cereals are dietary staples for many populations over worldwide. India is no exception. Among major grain foods, rice is used as staple food for many populations in the country. It forms an important part of diet of many people in the country. Much of the nutritional value of rice lies in its germ and bran which has been discarded during milling process in the traditional times. During milling of paddy, rice endosperm (70%) obtained as a major product while rice husk (20%), rice bran (8%) and rice germ (2%) obtained as by-product. During de-husking and milling of paddy, the brownish portion of rice taken out in form of fine grain, is the rice bran which is nearly 8% of milled rice. The bran is multilayered structure composed of pericarp, nucellus, seed coat and aleurone. It is the outer coat of rice endosperm. When rice bran is obtained as by-product during milling process, it contains some fractions of rice endosperm, rice germ and aleurone layer which are rich in proteins, vitamins, carbohydrates and trace minerals. So, rice bran is also rich source of essential nutrients. Rice bran also contains 20% oil, 15% protein, 50% carbohydrates (mainly starch), dietary fibers like pectin, beta-glucan and gum.
Solvent extraction has been reported to be the most promising method for removing oil from rice bran since the bran is bulky and usually contains less than about 18% of oil. Comparing with pressing method, solvent extraction always needs a whole line to process, which is more mechanized and easier to be automated. In another word, operations personnel needed for solvent extraction plant is much less than pressing. Meanwhile, energy consumption for solvent extraction is also much less than pressing. In one word, low production cost is one of the equitable of solvent extraction. In pressing, it is impossible to destroy oil cells completely or to degenerate proteins completely. Meanwhile, the temperature and pressure of oil press barrel is limited, which 5-12% oil residue. But oil residue of solvent extraction is less than 1%. In. To extract biodiesel from crude rice bran oil and rice bran oil. To evaluate the performance and emission analysis of compression ignition engine fueled with different blends of biodiesel extracted from crude rice bran oil and rice bran oil. To optimize the compression ratio of a variable compression ratio compression ignition engine using blend of rice bran methyl ester. To compare crude rice bran methyl ester and rice bran methyl ester based on the performance and emission characteristics. Comparing with pressing, solvent extraction operates in low temperature, which protect meals from degeneration of proteins. This is very important to meals used in animal feed.
2.1 SOLVENT EXTRACTION
Solvent extraction, also called liquid-liquid extraction (LLE) and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids. Immiscible liquids are ones that cannot get mixed up together and separate into layers when shaken together. These liquids are usually water and an organic solvent. In this process one of the components of a mixture dissolves in a particular liquid and the other component is separated as a residue by filtration.
Fig 2.1: Solvent Extraction or Liquid-Liquid Extraction
2.2 EXPELLER PRESSING
Expeller pressing (also called oil pressing) is a mechanical method for extracting oil from raw materials. An expeller press is a screw-type machine that mainly presses oil seeds through a caged barrel-like cavity. Raw materials enter one side of the press and waste products exit the other side. The machine uses friction and continuous pressure from the screw drives to move and compress the seed material. Pressure involved in expeller pressing creates heat in the range of 140–210 °F (60–99 °C). Some companies claim that they use a cooling apparatus to reduce this temperature to protect certain properties of the oils being extracted.
Fig 2.2: Expeller Pressing or Oil Pressing Machine
3.0 DESIGN (COMPONENTS)
3.1 SCREW CONVEYOR
A screw conveyor or auger conveyor is a mechanism that uses a rotating helical screw blade, called a “flighting”, usually within a tube, to move liquid or granular materials. They are used in many bulk handling industries. Screw conveyors in modern industry are often used horizontally or at a slight incline as an efficient way to move semi-solid materials, including food waste, wood chips, aggregates, cereal grains, animal feed, boiler ash, meat and bone meal, municipal solid waste, and many others. In industrial control applications the device is often used as a variable rate feeder by varying the rotation rate of the shaft to deliver a measured rate or quantity of material into a process. A flexible screw conveyor works by using the internal friction within a powder or bulk solid to transfer the forward motion of the powder in contact with the spiral to the whole tube contents. With an angled system, a dynamic equilibrium is set up with the spiral action moving some particles upwards. Screw conveyors can be operated with the flow of material inclined upward.
Fig 3.1: Screw Conveyor
3.2 BUCKET ELEVATOR
A bucket elevator, also called a grain leg, is a mechanism for hauling flowable bulk materials (most often grain or fertilizer) vertically. It consists of Buckets to contain the material. A belt to carry the buckets and transmit the pull. Means to drive the belt. Accessories for loading the buckets or picking up the material, for receiving the discharged material, for maintaining the belt tension and for enclosing and protecting the elevator.
A bucket elevator can elevate a variety of bulk materials from light to heavy and from fine to large lumps. A centrifugal discharge elevator may be vertical or inclined. Vertical elevators depend entirely on the action of centrifugal force to get the material into the discharge chute and must be run at speeds relatively high. Inclined elevators with buckets spaced apart or set close together may have the discharge chute set partly under the head pulley. Since they don’t depend entirely on the centrifugal force to put the material into the chute, the speed may be relatively lower. Nearly all centrifugal discharge elevators have spaced buckets with rounded bottoms. They pick up their load from a boot, a pit, or a pile of material at the foot pulley.
Fig 3.2: Bucket Elevator
3.3 RICE BRAN BUFFERING TANK
Temporarily storing the product in safe conditions during as production run, the buffer tank balances up and down stream processes in such a way as to minimize product losses and increase efficiency.
The mechanical plate feeder is a device for feeding material at a fixed and uniform rate. It is generally applied at the tail end of a conveyor or elevator which feeds a plant, but may be applied to feeding any other single unit.
Fig 3.4: Feeder
3.5 EMBEDDED SCRAPER CONVEYOR
The embedded scraper conveyor is a kind of traditional transportation equipment, it is mainly used to transport powder, particle and powder block materials. It can both horizontal conveying and tilt conveying. It is widely used in field of metallurgy, building material, power plant, grain, mining, mechanical, cement and so on.
The embedded scraper conveyor has reasonable whole structure and can multipoint feeding. The operating speed is steadily with low noise through the use of cycloidal planetary gear speed reducer. It is welcomed in metallurgy, mining and power plant. There are two types can be chosen which are the MC and MZ type. It is a transportation equipment by means of the moving scraper chain to transport bulk material in a closed rectangular cross-section shell.
Fig 3.5: Embedded Scraper Conveyor
3.6 COUNTER-CURRENT DRYER
Counter current drying is when the drying air flows in the opposite direction of the material flow. A counter current system is also beneficial for materials that have internal moisture retention and require higher heat and a longer drying cycle to draw out the moisture. Counter Current Spray Drying Systems are used for the production of non-sensitive materials and offer very high efficiency and lower residence times.
Fig 3.6: Counter-Current Dryer
3.7 LOOP EXTRACTOR
A “closed loop” refers to a system in which the entire process is done within a “closed” vessel. The solvent used to extract does not ever come in contact with the outside atmosphere. The “loop” portion refers to the recovery and reuse aspect of the system.
Fig 3.7: Loop Extractor
3.8 MISCELLA CENTRIFUGAL SEPARATOR
Miscella is defined as a mixture of oil and solvent that results from the extraction of flakes or extruded cottonseed kernels. Thus the refining of the oil in a solvent (usually Hexane) in which it was extracted is known as miscella refining.
A centrifugal water–oil separator or centrifugal liquid-liquid separator is a device designed to separate oil and solvent by centrifugation. It generally contains a cylindrical container that rotates inside a larger stationary container.
Fig 3.8: Miscella Centrifugal Separator
An evaporator is a device in a process used to turn the liquid form of a chemical substance such as water into its gaseous-form/vapor. The liquid is evaporated, or vaporized, into a gas form of the targeted substance in that process.
Pre-evaporation systems utilize low-level waste heat to evaporate weak liquor prior to the main evaporator train. Three heat sources are most often utilized in a pre-evaporator system: heat from a blow heat system, heat from a stand-alone concentrator, or heat from a continuous digester extraction liquor flash tank. The amount of evaporation achievable is dependent upon both the quantity of heat available and the number of effects in the system. Whenever a pre-evaporator is installed, its impact on the existing multiple effect evaporator system must be considered, in particular the effect of the higher feed solids. Aside from using waste heat, one of the main advantages of a pre-evaporation system is condensate segregation. The pre-evaporator strips the bulk of the TRS and VOC’s from the liquor resulting in an evaporator system condensate that is substantially cleaner.
Fig 3.9: Pre-Evaporator
3.10 ROLLER MAGNETIC SEPARATOR
Magnetic separation is a process in which magnetically susceptible material is extracted from a mixture using a magnetic force. This separation technique can be useful in mining iron as it is attracted to a magnet. his takes a lot of importance in food or pharma industries.
Fig 3.10: Roller Magnetic Separator
4.1 RICE BRAN AND RICE BRAN OIL
Rice bran is an oily layer in between the paddy husk and the white rice unique cooking oil produced from rice bran is rice bran oil. Rice bran oil is unique among edible oil due to its rich source of commercially and nutritionally important phytoceuti-cals such as, oryzanol, lecithin, tocopherols, and tocotrinols. However, most of these phytoceuticals are removed from the rice bran oil as waste byproducts during the refining process. It is a mixture of ferulic acid esters of sterol and triterpene alcohols. It occurs in rice bran oil at a level of 1-2 per cent where it serves as natural antioxidant. The article de- scribes the production of rice bran oil from rice bran and different methods of extraction of ?-oryzanol from rice bran oil. Rice bran oil (RBO) can be extracted from rice bran by solvent extraction using food grade n-hexane or in solvent free process by using ohmic heating or supercritical fluid extraction technology.
Fig 4.1: Structure of rice with different layers and Rice Bran Oil
4.2 Rice Bran and Rice Grain
Rice bran is the by-product obtained during milling of rice grain which contains 12-15% protein. The crude rice bran oil obtained in the solvent extraction process is subjected to either chemical refining or physical refining to meet the specifications of edible grade vegetable oil. Chemical refining of crude rice bran oil yields better product in terms of color and cloud point.
Fig 4.2: Rice bran and Rice grain
5.0 WORKING PROCESS
In modern days there are many methods used for extracting Rice Bran oil from rice bran and rice bran grain. The most commonly and efficiently used methods are Solvent Extraction method and Mechanical Oil Pressing Extraction method.
5.1 SOLVENT OIL EXTRACTION PROCESS
Solvent extraction as the name describes is “extraction of oil” from seeds, cakes or oil bearing material by using a Solvent. Normally Hexane a petroleum by-product is used as a solvent. In recent years, the principle and theory behind solvent extraction has gained wide acceptance as one of the new tools of modern hydro-metallurgy. With the growing demand for metals of ever higher purity, the increasing use of unusual metals, and the necessity for treating ores of lower grade and greater complexity, solvent extraction has joined the ranks of other accepted recovery methods and has added certain unique characteristics of its own in the constant struggle to lower costs.
Fig 5.1: Solvent Oil Extraction Process Diagram
5.2 RAW MATERIAL DISCHARGED TO THE PIT
At first raw material (Rice Bran) discharge in screw conveyor and store it in Rice bran buffering tank through the Bucket elevator. After measure the rice bran in scale weight it goes in the cleaning screen through the Uniform feeder. After cleaning, the bran send through the bucket elevator in roller magnetic separator. Oilseeds arriving at the processing plant contain many foreign matters such as dirt, stones, leaves, scrap metal etc. These foreign matters should be removed first prior to being stored, in order to eliminate substances that might cause heating in storage. It may then pass over a rough screen sufficiently coarse in mesh to allow all the seed to pass through, but on which any large pieces of foreign material are retained. It may subsequently be screened from fine dust etc., by passing over a shaking tray screen or through a rotating cylinder screen of such sizes that the seed is separated from all foreign matter other than particles of magnitude between the extreme limits of the diameter of the seeds. Then the dean seed is passed over a magnetic separator in order to remove small particles of iron which may have escaped separation in the cleaning process. This is an important precaution both in view of danger to cattle from the presence of fragments of iron in seedcake and also in view of possible damage to the cutting and crushing roll machinery in the succeeding processes. Magnets are particularly useful because the most common metallic contaminant found in seed is of magnetic type (mostly iron). As a matter of fact, magnets are commonly employed throughout the oil removal process, one being placed near the entrance to each of the various pieces of machinery which could be damaged by stray pieces of iron.
5.3 BRAN AND TIPS SEPARATION ON SCREEN
The bran send through distribution double layer scraper conveyor in the bran and tips separator where the bran and tips separates and the tips and broken rice collecting with the help of the conveyor to store it in the tips and broken rice holding tank. Mechanically adherent mineral or vegetable matter is removed from the seeds in the first stage by a combination of shaking and screening machinery.
And the pure bran send through the scraper conveyor in the condition tank and processing. After complete the process it goes through the Embedded scraper conveyor to Expander.
It is a process by which a set of mixed ingredients are forced through an opening in a perforated plate or die with a design specific to the food, and is then cut to a specified size by blades.
Expander treatment is related to extruder treatment. The feed material enters a feed barrel through an inlet gate. An anger or screw conveyor driven by an electrical motor forces the feed material towards a resistor in the outlet gate of the expander. This creates high shear and pressure, and aided by addition of steam, heat is produced. After the material passes the resistor in the outlet gate, the pressure immediately drops to atmospheric. The release of pressure and spontaneous evaporation of water makes the feed material expand in volume and the temperature to drop rapidly. The temperature can rise to high levels, but the entire process is usually completed within seconds. The desired size bran send in the Counter-current dryer container and the air heater start processing. The moisture is taking out from the bran.
The Bran after cooking is having 13-14% moisture is palletized in Pellet mill ,The powder form Bran Will be converted into high porosity pellet form in this Process Which helps the bran oil extraction with normal –Hexane from Bran pellets, because of Easy penetration of hexane through pellets and The oil present in the Bran completely Dissolved In normal-Hexane.
5.7 Cooling of pellets
The pellets coming out of pellet mill are having 11-12%moisture and 70 degree centigrade in temperature .These pellets needs to be cooled to 50 degree centigrade before going to Extraction process .The cooling of pellets takes place in a pellet cooler. Theses pellets will be passed to main plant by a drag conveyor where the extraction of oil takes place.
5.8 PRETREATMENT OF RAW MATERIAL
Proper preparation is the most important step for the successful working of a solvent extraction plant. A properly prepared material must be easily extractable, easy to filter-(good draining rate and relatively incompressible, and must have a reasonable minimum fines content and proper size distribution). The case of filtration of the material is measured by a term called mass velocity, which is the pounds of liquid passing through the filter bed per hour per square foot of filter area.
There are five steps in the accomplishment of proper preparation
I. HULLING: First determine the extent to which hulling may be required. In the case of cottonseed, groundnuts and soya beans, rice bran some or all of the hulls may be added to the meats prior to extracting or after, in order to lower or control the protein content of the final meal product.
II. CONDITIONING: The main purpose of oil process is to help the subsequent operation of rolling. Materials with refractory hulls, or the hulls which contain much oil, such as flaxseed and sesame, may require drying to about two per cent moisture content. This makes the material more frangible, increases the capacity of the rolls and reduces power consumption. Fibrous materials such as milo-germ need drying. Rice bran needs only cooking and crisping before extraction. For other oilseeds, including cottonseed, groundnuts and soya beans, use a. moisture content and temperature that is below the plastic range for flaking. This uses a little more power but promotes oil release (not actual oil flow). The optimum moisture content is roughly proportional to the oil-free, moisture-free meal content.
III. ROLLING AND FLAKING: By this third step a further reduction in size of the material is brought about. The term rolling is used when the material is passed through the “rolling machine” (3 to 5 high) such as are usually used for hydraulic or screw-pressing preparation. The term flaking is used to apply to the one pair-high smooth rolls used for direct extraction or sometimes for flaking· prepressed cake prior to solvent extraction, the product coming out in the form of thin flakes. Rolling or flaking if carried out at temperature. 120°F or lower will have little or no effect in reducing the alkali solubility of protein. But these operations have a profound effect on gland breakage and the final free gossypol value of the meals. Generally speaking, for rolling the operator wants to do the best job possible for breaking glands. On the other hand, for flaking the operator would probably want to break as few glands as possible. In the first case some form of cooking will follow’ the rolling, and gossypol made accessible by breaking or rupturing pigment glands which may be converted to the bound or non-toxic condition. In the second case, cooking is either not used or has been previously used as in pre-pressing and gossypol removed from broken or ruptured glands, will appear in the solvent extracted oil.
IV. COOKING: In the cooking process, the time cycle is short (15-25 minutes) for very soluble proteins such as in soya beans and groundnuts. Longer time (40-60 minutes) is needed for cottonseed and fibrous materials. Rice bran requires 30-45 minutes. Temperatures need not exceed 225°F. Moisture for most materials must be between 12 to 20 per cent, and for milo-germ must be between 30 and 40 per cent. Moisture is affected by oil content, protein content, protein solubility, starch content, and other characteristics of the material. The functions of cooking are (a) to complete the oil release started in conditioning and rolling, and if possible to put water on the inside and oil in the outside of the particles; and (b) to agglomerate or make big ones out of little ones.
V. CRISPING (EVAPORATIVE COOLING): This is the last step in the series. One per cent to three per cent of the moisture is lost during the conveying and screening operations. Crisping gives the cooked particles their relative incompressibility needed for higher filtration rates. As a result, each particle appears to be separate from the other. A handful, when pressed together can be easily separated.
5.9 SOLVENT EXTRACTION SECTION
In Solvent Extraction section, The seed after relevant preparation in the pre-treatment plant (cleaning, de-hulling, cracking, cooking, flaking and pressing) feeds the extractor where it is laid on a filtering belt with automatic level control devices. The filtering belt moving from one to the other side of the extractor charges the oil cake coming from the feeding hopper, submits the seed cake to solvent shower and discharges the de-oiled cake into the extractor discharging hopper discharging hopper from which the same by screw conveyor and chain elevator goes to the next step. The solvent (Hexane) enters the extractor in the opposite side of the oilseed, it is sprayed on the seed belt, flows through the same and is recovered in the underneath hopper from where it is pumped into the next sprayer step; the number of sprayer steps changes depending on the capacity of the plant. The solvent with extracted oil is pumped to the next step. Solvent is enriched with oil, as it goes through the different steps. The oil-hexane miscella from relevant tank is pumped to the distillation section where the hexane is distilled under vacuum and subsequently stripped from the oil with live steam.
Fig 5.9: Solvent Extraction section
Degumming is the first stage in the refining process. It is sued to separate the gums, phospholipids, proteins etc. that are insoluble in oil when hydrated. The crude filtered oil enters the process at a temperature of 5-35°C through a recuperative heat exchanger, where it is heated by the output oil from the process. Subsequently, it is heated in the heat exchanger by a heating medium to the desired temperature. After adding the appropriate amount of acid in front of the first dynamic mixer, the oil in the dynamic mixer is sufficiently mixed with the acid and proceeds to the vessel where the acid reacts with the non-hydratable phospholipids. It then proceeds to the second dynamic mixer, where precise amounts of lye with water are added, and then continues to the impeller-equipped reactor , where further chemical reactions, or precipitation of phospholipids, occurs. Then the oil enters the separator. The desired temperature is reached before the inlet and precipitated mucus is separated from the oil in the separator. Mucus is transferred to containers according to use of lye. If lye is used in the process of removing fatty acids, waste from the centrifuge is called soapstock. If lye is not used to remove fatty acids, it is called gums. After centrifuging, the oil is pumped through the recuperative heat exchanger, where it is preheated with the output oil, and continues to the heat exchanger where it is heated with heating media. Washing water is added to the heated oil and the oil is pumped through the third dynamic mixer into the second separator, where water and soaps are separated from the oil. The oil from the separator is conveyed to a vacuum dryer where the water content in the oil is minimized. From the dryer, the oil is pumped through the filters into a storage container. The vacuum in the dryer is provided by a water-ring with its own cooling circuit. The condensed water vapour is lifted into a separating storage tank.
Edible oil decolorization process is also called bleaching process. At first we use vacuum system to make decolorized tank vacuum status. Add degumming & deacidification edible oil into decolorization tank, then heat by high temperature for dewatering. Then add white clay, white clay have the absorption effect, it is mainly for removing the color and make oil more clear. Decolorizing section is mainly used to remove oil pigment, residual soap particles and metal ions. Under negative pressure, the mechanical mixing method combined with steam mixing will improve the decolorizing effect. The degumming oil firstly enters into the heater to be heated to the appropriate temperature of 110 degrees Celsius, and then goes to the blenching earth mixing tank. The blenching earth is delivered from the low blenching box to the temporary tank by wind. The blenching earth is added by automatic metering and is interlockly with the oil. The oil mixed with the blenching earth overflows into the continuous decolorizer, which is stirred by non-powered steam. The decolorized oil enters into the two alternate leaf filters to be filtered. Then the filtered oil enters the decolorized oil storage tank through the security filter.
Fig 5.11: Decolorizing Machine
Oil deodorization is the final stage in an edible oil refinery. Edible oil deodorizing is essential for removing undesired components such as moisture, color, and odor that negatively impact the taste, smell, and appearance of the final product. Deodorization of rice bran oil can be carried out in the normal manner by heating the oil to temperatures 200-250° C under high vacuum, stripping out the undesirable volatiles, in a current of dry steam. Any free fatty acids, peroxides and certain proportion of natural tocopherol antioxidants are also removed. In the process of deodorizing fats and oils by distillation with steam and under vacuum wherein the organic distillates are condensed in a scrubber in recirculating water in which flocs form that are emulsions of said distillates in water, said flocs decreasing the fluidity of the condenser water substantially as the concentration of distillates increases toward a value on the order of 2%, the improvement for suppressing the effect of said flocs on the fluidity of the condenser water as the concentration of distillates approaches and exceeds said 2% value that comprises incorporating and maintaining in said condenser water a concentration of water-soluble protein in the range of 0.05% to 0.5% and permitting the concentration of said distillates in said recirculating water to build up to values several times greater than 2%.
Fig 5.12: Deodorizing section
Today the process of Solvent Extraction is widely applied in miscellaneous fields of Science and Technology
1. Food industry (essential oil extraction)
2. Extraction of Rare-earths & PGM
3. Analytical Chemistry
4. Waste water treatment
5. Mineral oil treatment & dewaxing
6. Perfume industry (fragrance extraction)
7. Pharmaceutical industry
8. DNA purification
9. Analytical chemistry
10. Purification of amines
6.1 ADVANTAGES OF SOLVENT EXTRACTION PROCESS
1. Universal application in extraction of solvent components mixtures.
2. Flexibility with physical properties and various parameters.
3. Columnar design enhance the efficiency of the extraction.
4. Facilities stage wise phase contact.
5. Low production cost.
6. Solvent extraction machine has less finished cost, high oil yeild, less labor cost, excellent equipment safety, easy to operate and maintain, good operating conditions, etc.
7. Good meal quality.
8. Heat sensitive products are processed at ambient or moderate temperature.
9. Suitable at wide range of temperature.
10. Very large capacities are possible with a minimum of energy consumption.
11. Recovery of solvent is possible.
6.2 DISADVANTAGES OF SOLVENT EXTRACTION PROCESS
1. The toxicity of solvent leads to the restrictive regulations regarding their use.
2. Lack of selectivity, many lipophilic substances may end up in the concretes and render futher purification necessary.
3. Residues in the final product.
4. Time consuming.
5. Required skilled labour.
7.0 FUTURE PROSPECT
We were traditionally familiar with some of the oil crops like mustard, sesame and linseed grown around us. But the replacement of those traditional oils was in progress by that time with the introduction of relatively cheaper soybean oil imported from the western world. Later on, the additional requirement was satisfied by the palm oil imported from Malaysia. In contrast, there was an effort to introduce soybean in the greater district of Noakhali. That effort was limited only to that area. By these time some of the innovative industrialists became familiar with the prospect of rice bran oil. As a matter fact, the rice millers used to export a portion of their rice bran to India and elsewhere who were preparing RBO from that brans. Being informed of all this information, a section of the business community of the country came across to establish a number of rice bran oil extraction mills. A few years back BRRI made a survey on those mills to find out the existing status and constraints of the rice bran oil manufacturing system in Bangladesh. The country has a total paddy (unhusked rice) production about 50 million metric tones (2012-13). Out of this total production, 30% is processed at the household level and keep away from the marketing channel. The rest 70% is processed in rice mills with varying capacities. It is estimated that bran oil production potential is 2, 53,000 tone. As per an earlier survey by FMPHTD (Farm Machinery Post Harvest Technology Division) and, BRRI, we have 17000 of different types of medium to large rice mills in operation all over the country. These milling machines could be an instant source of huge amount of rice bran ready to be used for oil production. At least 22% oil content in the bran is worthy to be extracted economically. As per the BRRI survey team, there were 12 rice bran oil manufacturing industries in the country. Out of them, 7 mills were in operation and the others were in progress towards the production. Rupam oil mill, Dinajpur was the first bran oil manufacturing industries established in the 1980’s. Unfortunately, the operation of that industry came to a halt for reasons unknown. The BRRI survey team collected the information from KBC Agro Products Private Limited (Savar, Dhaka), Ali Natural Oil Mills ; Agro Industries Limited (Sonotia Bazar, Jamalpur), The Green ; Poultry Feed Industries (Utam Hajirhat, Rangpur), Emerald Oil Industries Limited (Sheripara, SherpurSadar, Sherpur), Rashid Oil Mills Limited, Majumder groups of Industries (Station Bazar, Noapara, Jessore, ChankaSherpur, Bogra) initiated their production on due time. There are some more industries like Agrotech International Limited, Shambhuganj, Mymensingh, having the capacity of producing 25,000 tones of oil which was not included in this study. There is a huge potential of exporting rice bran oils in different developed and developing countries of the world. As per the survey report, Majumder groups exported 20,000 tones of bran oil to India, Japan, China, Australia and some European countries.
The basic unit operations in vegetable oil processing have remained relatively unchanged for the past 5–6 decades. There are several drawbacks to today’s technology, and so alternative approaches are needed to overcome these drawbacks. In spite of having the advantage of a rapid extraction kinetics with a feasibility of recycling the solvent, there are some drawbacks of this process.
Use of toxic and flammable organic diluents. Sometimes the cost of solvent system becomes too expensive. In several cases there is loss of organic solvent in the process. Solvent Extraction may not pollute the air as much as other pyrometallurgical processes, but a lot of toxic chemicals find
their way into the waterbodies, polluting them. The extensive application of S.E. has become a field(& industry!) of its own. With proper modeling of the process, invention of new equipments, use of more effective extractants and a better understanding of the science behind it may lead it to be one of the most important extraction processes in many fields.
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