Title of Invention

"A PROCESS TO RECOVER OIL AND BLEACHING EARTH FROM SPENT BLEACHING EARTH"

Abstract

a process to recover oil and bleaching earth from spent bleaching earth obtained from vegetable oil refining process characterized in that the process comprises: i) treating the sli~nt bleaching earth with a solvent selected from a group consisting of toluene, acetone, xylene, isopropyl alcohol or n-hexane at a temperature between 350C to 500C to form a slurry; ii) separating the solids from liquid in the slurry formed in step (i) by (A) separating the mixture of solids and liquid into a first solid fraction and a first liquid fraction; (B) treating the first solid fraction from step (A) with the same solvent used in step (i) to form a second mixture of solids and liquid; and (C) separating the second mixture of solids and liquid into a second solid fraction and a second liquid fraction; iii) extracting vegetable oil from at least one of the liquid fractions obtained in step (ii).

Full Text

FIELD OF INVENTION The present invention relates to a process of recovery of oil and bleaching earth from spent bleached earth. More particularly the invention relates to the recovery of palm oil from spent bleached earth or clay. BACKGROUND ART Spent bleaching earth is a solid waste material generated as part of the refining process in the vegetable oil industry worldwide. A typical vegetable oil refining process involved pretreatment of crude vegetable oil such as palm oil with phosphoric acid, followed by bleaching deodorization. The purifying treatment is designed to remove undesired free fatty acids, phophatides, glycerides, sterols, tocopherols, resinous and mucilaginous materials from the crude palm oil. Bleaching is done solely to reduce the colour of the oil and is done using bleaching earth or clay. This process is followed by deodorization, which is intended primarily for the removal of traces of constituents that give rise to flavours and odors. The most common adsorbent used for bleaching is the bleaching earth or clay. Naturally occurring bleaching earth is bentonite or montmorillonite clay which when acid activated with sulfuric acid increases adsorption capacity. After the treatment of crude oil with phosphoric acid, the oil is treated with bleaching earth, which adsorbs the impurities. Subsequently the treated oil is separated from the bleaching earth by filtration mostly in batches. The spent bleaching thus separated from the oil contains gums and impurities along with significant amount of oil. It is not economical to recover the oil from the spent bleaching earth due to the small amounts of bleaching for individual oil refinenes. In some countries it is generally a practice to dispose of the spent bleaching earth in landfills where else in some other countries it is treated as hazardous and is disposed off accordingly as hazardous waste. In countries or regions where the palm oil industry is very large there is large amount of spent bleaching earth generated in the refining of crude palm oil process. Thus there is a need for a process to recover the oil in the spent bleaching earth in an economical manner before disposing of the spent bleached earth. SUMMARY OF THE INVENTION The invention discloses a process to recover oil from spent bleaching earth recovered from vegetable oil refining process. Although the example described in this invention refers to palm oil, the technology can equally be used in the extraction of other vegetable oil from spent bleaching earth used in the refinery process of other vegetable oils, such as soyabean oil, peanut oil, sunflower oil, etc. The process involves three sub-processes compnsing of reacting the spent bleaching earth with a solvent selected from a group consisting of toluene, acetone, xylene, isopropyl alcohol or n-hexane at a temperature between 35oC to 5000; separating the solids and liquid from slurry formed in the previous step; and extracting oil from the liquid fraction obtained in the previous step. The separation of the solids and the liquid from slurry can be formed in two steps. The slurry mixture of solids and Hquid is first separated into a solid fraction and a liquid fraction. The solid fraction so separated still contains a significant portion of oil. Therefore the solid fraction is reacted with some solvent. The next slurry of solids and liquids is again separated into a solid fraction and a liquid fraction. More particularly the invention descnbed a process where spent bleaching earth from crude palm oil refinery process is reacted with n-hexane at a temperature between 35oC to 5000 in an agitated reactor for about 15 to 45 minutes. The reaction in the agitated reactor allows the dissolution of oil into the solvent The slurry concentration in the agitator iS maintained between 5% to 50% weight The slurry thus formed is led to gravity settlers having plates for settling of solids. The thicker slurry from the settlers is then introduced to vacuum belt filter for separation of the clay/bleaching earth and miscelle. Alternatively the slurry from the agitator reactor can be filtered in porou.s metal filters in two stages to improve efficiency About 30% to 35% by weight of slurry from agitator is fed to the porous metal filter to get a clear filtrate and a cake with 70% to 75% dryness. This separated cake is ten remixed with fresh and/or recycled hexane to recover further absorbed oil from the cake in another agitator reactor. The slurry from this agitator is then again separated in another porous metal filter to obtain deciled bleaching earth with about 3% to 5% oil content. The filtrate or the miscella from the settlers/porous metal filters is than distilled in a listillation plant, which is a combination of rising film and fall film evaporators. The n-hexane disblled off is condensed in condensers and recycled back for processes. The extracted oil is urther sent to refining to remove free fatty acids (FFA) in a normal deodorizer system. The spent bleaching earth after removal of significant portion of the oil is the desolventized in a loop system using steam to recover left over solvent. This process condition is maintained between 800C to 110OC to ensure complete removal of solvent before being fed to the incinerator system. The present invention relates to a process to recover oil and bleaching earth from spent bleaching earth obtained from vegetable oil refining process characterized in that the process comprises: i) treating the spent bleaching earth with a solvent selected from a group consisting of toluene, acetone, xylene, isopropyl alcohol or n~ hexane at a temperature between 350C to 500C to form a slurry; ii) separating the solids from liquid in the slurry formed in step (i) by (A) separating the mixture of solids and liquid into a first solid fraction and a first liquid fraction; (B) treating the first solid fraction from step (A) with the same solvent used in step (i) to form a second mixture of solids and liquid; and (C) separating the second mixture of solids and liquid into a second solid fraction and a second liquid fraction; iii) extracting vegetable oil from at least one of the liquid fractions obtained in step (ii). DEATILED DESCRIPTON OF DRAWINGS The invention Will now be described in detail by reference to preferred embodiments by way of example only and to the following drawings in which: - Figure 1 shows a block diagram of a process according to the present invention Figure 2 shows a flow diagram of an extraction plant DETAILED DESCRIPTION OF THE INVENTION A preferred embodiment of the invention will now be described with reference to Figures 1 and 2. The commercial process for the recovery of oil from spent bleaching earth includes reacting spent bleaching earth such as bentonite or montmorillonite clay with solvents such as acetone, tuolene, xylene, sopropyl alcohol or n-hexane at a temperature range between 35CC to 5O0C in an agitated reactor for about 15 to 45 minutes. It is preferred that n-hexane be used as the solvent and the operating temperature is 45~C and the reaction time within the agitated reactor vessel (10) is 30 minutes. The reaction in the agitated reactor vessel (10) allows the dissolution of oil in the bleaching earth into the solvent. Typically the slurry concentration in the agitator vessel (10) is maintained between 5% to 50% by weight ideally between 30% to 35% ww. This level in the agitator vessel (12) is maintained by re-circulation of part of the slurry. The slurry thus formed is led to gravity seWers (12) having plates for settling of solids. Thus the solids are separated from the miscella (solution of oil in solvent). The settlers (12) are operated with controlled feed rates to suit individual capacity and to ensure that the overflow is clear of solids and to ensure that the underfiow is about 45% to 65% solids by weight The operating conditions may vary from time to time depending on the solids characteristics. Hence the gravity settlers (12) need to be drained from time to time. The thicker slurry from the gravity settlers (12) is then led to a vacuum belt filter (14) for separation of the clay/bleaching earth and the miscella. This vacuum belt filters can be used in combination with gravity type settlers. Alternatively the said settlers and belt filters can be replaced by the use of static porous metal filters under pressures of 1 to 4 bars. Preferably the filtration can be done using the static porous metal filters in two stages to improve efficiency About 30% to 35% by weight of slurry from agitator is fed to the porous metal filters to obtain a clear fllb~ate and a cake of about 70% to 75% dryness. This separated cake is then remixed with fresh and/or recycled hexane to recover further adsorbed or remaining oil from the cake in another agitated reactors vessel. The slurry from this agitator is then again separated in another porous metal filter to obtain deojled bleaching earth with about 3% to 5% oil content The filtrate or the miscella from the settlers/vacuum belt filter/porous metal filters is then distilled in a distillation plant, which is a combination of rising hIm and falling film evaporators. The hexane, which is distilled off is condensed in condensers and recycled back for process. The extracted oil is sent for refining to remove the free fatty acids (FFA) in a normal deodorizer system. The spent bleaching earth after removal of significant portion or oil is then desolventised in a loop system, using steam to recover leftover solvent The process conditioners are maintained between 800C to 11000 to ensure complete removal of solvent The resultant bleached earth cake is disposed off. It is environmentally safe enough to be disposed in landfills. In another aspect the resultant bleached earth (the deoiled bleached earth) is used as fuel in the incinerator system in the plan itself. The organic content remaining in the deoiled bleached earth is burnt off leaving anhydrous clay as residue. The anhydrous clay is advantageously used as raw material in other industries, such as the cement manufacturing industry. The inventors carried out research trials to identify other suitable solvents that can be used commercially in the extraction of the maximum percentage of oil from the spent bleaching earth (SBE) whilst at the same time without deteriorating final oil quality. SBE was mixed with selected solvent to make 35% solid concentration in slurry form. The slurry was agitated using a magnetic stirrer for 15 minutes at 400C to 4500. After 15 minutes. the slurry was filtered in which the cake of 75% dryness was separated from the clear filtrate The percentage oil in the filtrate was analyzed whereas the cake was kept for second stage washing. In the second stage extraction, sufficient amount of the same solvent as used in the first stage extraction was added into the wet cake from the first stage washing to provide 35% solid concentration The temperature and time of mixing was maintained the same as in the first stage. The slurry was then filtered. The filtrate and wet cake were analyzed for oil content The above described procedure was repeated using same lot and quantity of SBE but with different solvent The result of the analysis is given below in Table 1. Tablel (Table Removed) From the analysis results as shown in Table 1, it is evident that the best solvent to extract maximum oil from SBE in decreasing order is: - Acetone ' Tuolene > IPA' Hexane. Howeverm t soffi eandoilco hebestsolventwasstillproduced byusinq hexane. Oil quality (colour) in decreasing order is Hexane Tuolene> IPA> Acetone. The research findings show that hexane is still the most suitable solvent to use in extracting oil from SBE. The inventors have found that the use of porous metal filters as compared to vacuum belt filter produces better efficiency of extraction of oil from SBE. The palm oil extracted from SBE utillzing the method described above yields a retined, degummed and deodorized oil with the typical specifications as shown in Table 2. (Table Removed) The fatty acid distillate extracted from SBE utilizing the method described above yields a distillate with the specifications as shown in Table 3. Table 3 industrial Grade Palm Oil (lGPO) is a Refined, Degumowd and Deodorized Oil (Table Removed) We Claim: 1. A process to recover oil and bleaching earth from spent bleaching earth, obtained from vegetable oil refining, characterized in that the said process includes the steps of: (i) treating the spent bleaching earth with a solvent, selected from the group consisting of toluene, acetone, xylene, isopropyl alcohol and nhexane, at a temperature between 350C to 500C for a period of 15 to 45 minutes to form a slurry with a spent bleaching earth to solvent ratio of 5% to 50% by weight; (ii) separating the solids from liquid in the said slurry by - introducing the said slurry to a filter, 30% to 35% by weight at a time, for at least one stage of filtration to obtain a clear filtrate and a cake of about 70% to 75% dryness; (iii) extracting oil from the said filtrate. 2. A process as claimed in claim 1 wherein extracting oil from the said filtrate is conducted by distilling the filtrate to separate the solvent used and the oil. 3. A process as claimed in claim 1 wherein the oil obtained from step (iii) is subjected to refining for removal of free fatty acids. 4. A process as claimed in claim I wherein the cake obtained from step (ii) is subjected to a de-solventising process comprising steam treatment to recover left over solvent and deoiled bleaching earth. 5. A process as claimed in claim 4 wherein the said steam treatment is conducted at a temperature of about 800C to 1 100C. 6. A process as claimed in any of the preceding claims wherein the solvent used is n—hexane. 7. A process as claimed in any of the preceding claims wherein the spent bleaching earth is obtained from palm oil refining. 8 A process to recover oil and bleaching earth from spent bleaching earth, obtained from vegetable oil refining substantially as herein described with reference to and as illustrated in the accompanying drawings.

Documents:

1344-del-2003-abstract.pdf

1344-del-2003-assignment.pdf

1344-del-2003-claims.pdf

1344-del-2003-complete specification (granted).pdf

1344-del-2003-correspondence-others.pdf

1344-del-2003-correspondence-po.pdf

1344-del-2003-description (complete).pdf

1344-del-2003-drawings.pdf

1344-del-2003-form-1.pdf

1344-del-2003-form-18.pdf

1344-del-2003-form-2.pdf

1344-del-2003-form-3.pdf

1344-del-2003-form-5.pdf

1344-del-2003-form-6.pdf

1344-del-2003-gpa.pdf

1344-del-2003-petition-138.pdf