WO2014035760A1

WO2014035760A1 - Pressed palm fibre solvent extraction

Info

Publication number: WO2014035760A1
Application number: PCT/US2013/055966
Authority: WO
Inventors: Timothy G. Kemper; Marc Kellens
Original assignee: Desmet Ballestra North America, Inc.
Priority date: 2012-08-29
Filing date: 2013-08-21
Publication date: 2014-03-06

Abstract

Wet pressed palm fibres (PPF) having a moisture content of greater than about 30 wt% water are extracted in an extractor to yield miscella and marc. In one embodiment, palm oil precursor sludge (POPS) comprising a slurry with solids containing palm oil, is mixed with an extraction solvent. The solvent/POPS mixture is separated into a miscella fraction and a water/solids fraction with the water/solids fraction fed to the upstream entry end of a DTDC. The miscella from the solvent/POPS mixture can be separated in a cyclone or the like to yield a "lights" solvent/palm oil fraction and a "heavies" fraction containing predominantly solids particles. The solids particles may be recycled to the PPF extractor.

Description

PRESSED PALM FIBRE SOLVENT EXTRACTION

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of U.S. Provisional Patent Application Serial No. 61/694,515 filed August 29, 2012.

BACKGROUND OF THE INVENTION

[0002] Palm oil is one of the most important sources of edible oil in the world. In the extraction of palm oil, the fresh fruit bunches (FFB) are cut from the top of palm trees and brought to a Palm Oil Mill (POM) on trucks. The FFB weigh about 140 pounds each and are composed of about 1200 fruits hanging on a stem structure, similar to grapes, only much larger. The bright red fruits are about ¾-inch in diameter, and they have a fleshy outer part (mesocarp) with a pit in the middle (nut) similar to an olive.

[0003] At the POM, the FFB are first sterilized with live steam heat, then the palm fruits are stripped from the empty fruit bunch (EFB). The EFB is discarded. The palm fruits are then digested with live steam heat, to enable the mesocarp to be separated from the nuts and to allow the cellular structure of the mesocarp to be broken down. The resultant mash from the digester goes to a screw press. The screw press squeezes out as much palm oil and water as possible, with the goal being to create a press cake with only 5-6% remaining palm oil with less than 10% of the nuts crushed. After pressing, the crude palm oil (CPO) is clarified before being sent to an oil refinery. After pressing, the press cake goes to a nut/fibre separation unit where the nuts are removed from the pressed palm fibre (PPF). The nuts are then cracked, and the internal palm kernel (PK) is separated for further processing while the shell of the nut is used for other purposes. The PPF containing about 35-40% moisture and 5- 6% oil is then sent to a biomass boiler to create steam for the POM.

[0004] In recent years, the value of palm oil has increased greatly. In contrast, the value of PPF as a boiler fuel is only a fraction of the palm oil value. Due to the high value of the extracted palm oil, it is highly desirable to remove as much palm oil from the PPF as possible.

SUMMARY OF THE INVENTION

[0005] In accordance with one embodiment of the invention, a process is provided for removing palm oil from pressed palm fibres (PPF). The process comprises the step of providing a wet mass of PPFs having from about 30% or higher moisture content. This wet mass of PPFs is forwarded to an extractor to extract palm oil from the wet PPFs by contacting the PPFs with a solvent. This extraction results in a miscella fraction comprising palm oil and solvent and a marc fraction comprising solids, water, and solvents. The marc is subjected to a separation process to separate the solvent therefrom, and the miscella is separated via conventional techniques, such as by distillation, to recover solvent and yield the desired palm oil.

[0006] In another exemplary embodiment, the PPFs that are extracted are not dried prior to entry into the extractor. Further, and in another aspect of the invention, the marc separation step wherein solvent is separated from the meal results in the recovery of solids having about 30% water content. These solids are then burned as fuel in a steam generating boiler of the type wherein the boiler is adapted to provide steam to the palm oil mill (POM).

[0007] In yet another embodiment, the step of separating solvent from the marc is performed in a desolventizer toaster-dryer-cooler (DTDC). In other embodiments, the miscella fraction separated in the extractor can be forwarded to a cyclone separator or other separation device. The heavy fraction from this miscella separation, including solids particles, is then recycled back into the extractor.

[0008] In another aspect, a palm oil precursor (POP) sludge is mixed with a suitable solvent, such as hexane, in a mixing vessel or the like. This sludge is then separated, such as by decanting, into a miscella fraction containing palm oil, solvent, and some minor solids, and a water/solids fraction. The water/solids fraction may be forwarded to the DTDC. Further, the miscella fraction resulting from separation of this POP sludge may be subjected to a further separation operation, such as by a hydrocy clone or the like, with the heavy fraction from this separation being fed back to the extractor.

[0009] In one embodiment, the POP sludge comprises spent bleaching earth or clay. In another embodiment, the POP sludge comprises condensed dirty water resulting from a pressing operation of palm fibre or palm pulp.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 is a flow diagram of a pressed palm fibre solvent extraction process in accordance with the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0011] In accordance with one embodiment of the invention, and as shown in Fig. 1 , pressed palm fibre (PPF) 2 having from about 30-40% moisture therein is used as feed to the upstream end of extractor 6 through hopper 4. The PPF is taken directly from the palm oil mill (POM) and is not dried prior to feed into the extractor. This feed of "wet" i.e. , 30-40% moisture containing PPF contrasts with prior art processes wherein the PPF from the POM is dried to about 10% or less by weight prior to any solvent extraction step.

[0012] The PPF is extracted in the extractor 6 via well known techniques. Extractor 6, as shown, may comprise a foraminous, inclined belt or the like traveling from the upstream section of the extractor toward the downstream, with stripping solvent, such as hexane, acetone, toluene, xylene, or isopropyl alcohol, or the like being admitted through downstream inlet 10 for counter current percolation through the traveling "wet" PPF in the extractor. Preferably, the extractor is an "LM" - Extractor, available from DeSmet Ballestra, in which an inclined conveyor carries the PPFs from the inlet toward the solids (marc) exit 12 at the downstream end of the extractor.

[0013] The miscella, comprising extraction solvent and palm oil, exits at the upstream exit 64 of the extractor where it is forwarded via the action of pump 62 to miscella recycle line 68. The recycled miscella is subjected to a cyclone 26 or other separation mechanism with the "lights" or liquid fraction separated via line 30 and forwarded to miscella tank 32 whereby it is then forwarded to further separation techniques such as distillation 34 for separation of the solvent from the desired palm oil. A minor "heavies" of solids, such as predominantly fines, is separated in the cyclone at 26 and then fed at 28 into the extractor.

[0014] As shown, marc or wet meal exiting at 12 is forwarded via line 14 to the upstream end of a desolventizer toaster-dryer-cooler 40 (DTDC). The DTDC can be of the convention type such as that available from DeSmet Ballestra. The DTDC is a vertical vessel containing trays or stages capable of pre-desolventizing, desolventizing, toasting, drying, and cooling the marc recovered from the extractor. In the pre-desolventizing section, hexane or other solvent is evaporated by indirect heating via heated trays. In the desolventizing section, most of the hexane is evaporated while condensing live steam. In the toasting and stripping sections, a combination of indirect and live steam is used to strip the remaining solvent such as hexane. In the drying section or drying trays located downstream from the toasting and stripping trays, hot air is admitted and blown through the meal, whereas the air blown or pulled through the meal for cooling.

[0015] As shown in Fig. 1 , the marc is admitted to the DTDC at the top or inlet entry conduit 14 with hexane or other vapor being removed from the DTDC as shown at 60. A fan 42 or the like is provided in conjunction with heater 44 to provide heated air through the inlet ducts 46, 48, 50. As indicated above, the DTDC functions to desolventize, toast, dry, and cool the marc as it enters from the upstream end of the vertical DTDC to the exit 70 at the downstream end of the DTDC. Air is drawn off the DTDC 40 via vent 51. The moist air from conduit 51 is subjected to separation action via a separator such as a cyclone separator shown at 52 with wet air removed at line 54 and with the solids exiting through 56. The separated solids are combined with the marc from line 70 and provided as feed 58 to the POM boiler. This solids feed to the boiler has about a 30% moisture content. One exemplary DTDC is described in U.S. Patent 4,622,760, hereby incorporated by reference herein. [0016] In accordance with one aspect of the invention and as shown in Fig. 1 , sludge, comprising palm oil precursor (POP) is provided as shown at 16. This POP sludge is formed from one or more of a variety of POM effluent streams and is a water/solids slurry wherein the solids comprise varying amounts of palm oil. For example, the POP sludge may be prepared by a process comprising a first step of pressing the wet fruit fibre or pulp to yield a pressed oil/water mixture. This pressed oil/water mixture is separated, such as by decanting, into a palm oil fraction and a "dirty" water fraction. The dirty water fraction is then concentrated such as by evaporation or the like resulting in a POP sludge comprising about 60-70% water with palm oil and palm oil bearing solids.

[0017] POP sludge can also consist of spent bleaching earth or clay. As is known in the art, palm oil and other oils may be bleached to reduce oil color by the use of bleaching earths or clays such as phosphoric acid activated bleaching earth. Bentonite and montmorillonite clays can also be used as bleaching agents, with the treated palm oil being ultimately separated from the bleaching aid. The spent bleaching earth or clay contains gums and impurities along with significant amounts of the desired palm oil. As used herein, the term POP sludge is therefore used to define any water/solids slurry wherein the solids component contains extractable palm oil. Specific examples of POP sludge include the aforementioned condensed "dirty" water/sludge mixture which includes minor portions of the desired palm oil or the spent bleaching earth or clay that also contains palm oil as a component.

[0018] The POP sludge is provided as shown at 16 and is mixed with a solvent, such as hexane 18, or any of the other previously mentioned solvents in a mixing vessel 19. The resulting mixed solvent/sludge is pumped via pump 20 to a separation station 22 such as a decanting vessel. Here, the sludge is separated into a miscella fraction and a water and solids fraction. The water and solids fraction is forwarded via line 36 into the marc feed line 14 to the DTDC. The miscella or oil/solvent fraction is forwarded through conduit 24 to the miscella recycle pump 62 wherein it is forwarded through miscella recycle line 68 for separation at cyclone 26 with the solids or "heavies" fraction then recycled to the extractor 6 via line 28. The miscella rich fraction is forwarded through line 30 to miscella tank 32.

[0019] In summary, various aspects of the PPF extraction process involve taking the 30-40% moisture PPF directly from the POM and feeding them to the extractor without drying the PPFs. With a sufficient extraction time, usually about 1 hour, and temperature of about 55 °C, and the provision of a number of extraction stages, usually about 10, it has been determined that 4-5 % oil can be removed without doing any preparation of the PPF prior to solvent extraction. This ability to extract a 30-40 % moisture content PPF is unique as all other seed extractions require lowering the moisture to about 10% by weight to obtain sufficient percolation of the solvent.

[0020] Additionally, certain embodiments of the invention provide drying of the extracted PPF in a DTDC (using steam/heated hot air) from about 45 % moisture content after desolventizing down to 30% moisture content. Preliminary observations indicate that the PPF will not ignite in the biomass boiler once the oil is extracted out, unless the moisture is reduced to 30% or less. In this embodiment, the moisture is removed in a post-extraction process where it is done with air, and this drying does not negatively affect the extracted palm oil quality.

[0021] As mentioned above, POMs have various effluent streams. These effluent streams can be concentrated by various means resulting in a sludge consisting of water, various palm fruit residue, and palm oil. This sludge cannot be directly added to a PPF extraction without negatively affecting percolation and extraction results. However, in one embodiment, solvent is added to the sludge, dissolving the oil fraction into the lighter hexane (solvent) fraction, enabling a simple decantation to separate the light phase consisting of miscella (oil and solvent) from the heavy phase consisting of solids/water and some residual solvent. In one embodiment, the light phase is then introduced to the miscella distillation system in the PPF extraction plant, and the heavy phase can be introduced into the desolventizer toaster of the PPF extraction plant. The result is additionally oil recovery from the sludge without adversely affecting the oil recovery from the PPF. [0022] Although this invention has been described in connection with specific forms thereof, it will be appreciated that a wide variety of equivalents may be substituted for those specific elements and steps of operation shown and described herein and that certain features may be used independently of other features, all without departing from the spirit and scope of this invention as defined in the appended claims.

[0023] What is claimed is:

Claims

1. Process for removing palm oil from pressed palm fibres (PPF) comprising:

(a) providing a wet mass of PPFs having from about 30% and higher moisture content therein;

(b) extracting palm oil from said wet PPFs by contacting said wet PPFs with a solvent in an extractor, thereby resulting in a miscella fraction comprising palm oil and solvent and a marc fraction comprising solids, water, and solvent; and

(c) separating said solvent from said marc.

2. Process as recited in claim 1 wherein said PPFs, extracted in said step (b), are not dried prior to entry into said extractor.

3. Process as recited in claim 1 further comprising recovering solids having about 30% water content from said marc fraction as a result of said step (c) and burning said recovered solids as boiler fuel for a steam generating boiler adapted to provide steam to a palm oil mill (POM).

4. Process as recited in claim 1 wherein said step of separating said solvent from said marc in step (c) is performed in a desolventizer toaster dryer cooler (DTDC).

5. Process as recited in claim 1 further comprising separating solids from said miscella in a cyclone separator and recycling said separated solids from said miscella back into said extractor.

6. Process for removing palm oil from pressed palm fibres (PPF) comprising:

(a) providing a mass of PPFs; (b) extracting palm oil from said PPFs by contacting said PPFs with a solvent in an extractor, thereby resulting in a miscella fraction comprising palm oil and solvent, and a marc fraction comprising solids, water, and solvent;

(c) separating said solvent from said marc in a DTDC;

(d) mixing a palm oil precursor (POP) sludge and a solvent, and separating said mixed POP sludge into a miscella fraction containing palm oil, solvent, and some solids, and a water and solid fraction;

(e) feeding said water and solids fraction from step (d) to said

DTDC.

7. Process as recited in claim 6 further comprising separating solids from said miscella from said step (d) in a separation mechanism, and feeding said separated solids to said extractor.

8. Process as recited in claim 7 wherein said POP sludge comprises spent bleaching earth or clay.

9. Process as recited in claim 7 wherein said POP sludge comprises condensed dirty water from a pressing operation of palm fruit fibre or palm pulp.

10. Process as recited in claim 7 further comprising feeding said miscella fraction from said step (b) to said separation mechanism and forwarding miscella from said separation mechanism to a miscella tank, and recycling solids from said separation mechanism to said extractor.