A METHOD FOR TREATING THE EFFLUENT PRODUCED FROM A PALM OIL MILLING PROCESS

Abstract

The present invention relates to a method for treating effluent produced from a palm oil milling process, comprising the steps of removing solids (20) from the effluent, wherein the removed solids are formed into dry products, removing water (30) from the effluent for reuse of the water in the palm oil milling process, and extracting oil (40) from the effluent to form a residual sludge, wherein the steps of removing solids, removing water, and extracting oil are carried out in the sequential order of solids, water, and oil.

Description

A METHOD FOR TREATING THE EFFLUENT PRODUCED FROM A PALM OIL MILLING PROCESS FIELD OF INVENTION The present invention relates to a process for treating effluent produced from the processing of palm oil, and more particularly, the present invention relates to a method for processing the effluent from a palm oil mill in order to reduce or remove discharge into the environment. BACKGROUND OF THE INVENTION Palm oil is an important commodity with wide-ranging applications, from the production of cooking oils, food, and confectionery to oleochemicals such as soaps and lubricants, as well as biodiesel. Palm oil is derived from the fresh fruit bunches (FFBs) of oil palm trees, Elaeis guineensis. The FFBs harvested from the oil palm plantation are processed in a palm oil mill to extract crude palm oil and palm kernels as the main products. During the processing of palm fruit bunches (PFBs) to recover crude palm oil and palm kernels, a large volume of sludge is also produced at the mill in several stages. A condensate is produced from the sterilizer during the PFB sterilization process. Pressing the mesocarp produces a thick sludge composed of crude palm oil, water, and solids. Water is added to this sludge during the clarification process to aid in the recovery of crude palm oil. When the empty palm fruit bunches (EFBs) are pressed, an EFB press liquor containing oil, water, and solids is produced. All three fractions can be processed separately or together to recover crude palm oil. The residual sludge, which typically contains less than 1% oil, 3–6% solids, and 93–96% water, is commonly referred to as palm oil mill effluent (PAM).The total volume of sludge is normally in a ratio of 60% with respect to the amount of RFF processed. Other by-products and waste produced include palm kernel shell, empty palm fruit bunches, mesocarp fiber, and decanter cake. The effluent from the palm oil mill (EMAP) contains a high concentration of organic matter and needs to be treated to comply with regulations as required by the relevant authorities. However, due to this high concentration of organic matter, EMAP treatment has always been a challenge in the palm oil milling industry. EMAP treatment does not generate revenue, represents a substantial cost for the palm oil mill, and occupies a large area of ​​land. A medium-sized mill with PACI? ίη / ZZOZ / E / YILI capacity of 45 t / h of RFF often requires pond treatment systems that occupy 2-4 hectares (5-10 acres) of land. Recent developments in the treatment of EMAP include the capture and utilization of biogas generated during an anaerobic digestion process. The biogas can be used to generate electricity and contribute to the revenue of certain mills by selling the collected energy to the national grid. Alternatively, the biogas can be used as fuel for boilers or simply burned. Aside from that, there have been ongoing efforts to find new and improved treatment methods in the palm oil milling industry to reduce environmental pollution and comply with the stricter regulations set by local authorities regarding milling effluent. Furthermore, as the area of ​​oil palm plantations has increased over the years, the effluent treatment systems of palm oil mills need to be upgraded to handle the growing amount of raw material required for processing. The international publication WO 2013 / 169091 A1 describes a method for processing EMAP, comprising the steps of pretreatment, biological treatment, and membrane separation. The pretreatment step includes subjecting the EMAP to a rotary separator, a particle separator, and water-oil separation. The biological treatment in the method produces methane gas, which requires further treatment to reduce greenhouse gas emissions into the atmosphere. International publication WO 2014 / 05415 A1 describes a system for recovering oil from EMAP (Excess Palm Oil), comprising a screening machine, a heater, catalyst feedstock, a reactor, and a centrifuge. The system is mounted on a vehicle for portability. The system recovers crude palm oil from EMAP after centrifugation. However, the system does not address the issue of effluent discharge as solids, and an aqueous phase is produced as a byproduct. Malaysian patent MY-144226-A describes a method for extracting crude palm oil from press liquor to reduce effluent discharge, comprising the steps of removing the solid, aqueous, and oil phases from the press liquor. The method requires modification of existing palm oil milling equipment and processes, as it uses press liquor as the starting substrate. In view of the above, it is therefore desirable to provide a method for treating EMAP in order to effectively reduce or remove effluent discharge, recovering the solid phase, aqueous phase, and oil phase of EMAP so that each phase can be recycled for other uses. Furthermore, there is a need to provide a method for treating EMAP that can PACI? ίη / 77P7 / E / YILI to be incorporated into the existing palm oil extraction operation. The method is configured to be added after the last process in the normal oil recovery, so that the current operations used in the palm oil mill are not affected in terms of the quality of the recovered oil and oil loss by the incorporation of the EMAP treatment method. BRIEF DESCRIPTION OF THE INVENTION It is an objective of the present invention to provide a method for treating the effluent produced from the palm oil milling process. It is also an objective of the present invention to provide a method for removing the effluent discharge from the palm oil milling process, treating the EMAP and recovering the solid, aqueous, and oily phases of the EMAP. Another objective of the present invention is to provide a method for extracting crude palm oil from EMAP. Another additional objective of the present invention is to provide an economically viable method for achieving zero discharge from the palm oil milling process, thereby reducing or eliminating the release of methane gas from conventional effluent treatment ponds. It is also an objective of the present invention to provide a method of treating EMAP that can be incorporated into the existing palm oil extraction process without changing said process. The present invention relates to a method for treating the effluent produced from the palm oil milling process, comprising recovering solids, water, and crude palm oil from the effluent to produce a residual sludge, wherein the recovery of solids, water, and crude palm oil is carried out in sequential order: solids first, water next, and finally crude palm oil, and each of the recovered solids, water, crude palm oil, and the final residual sludge is recycled or converted into usable products. In one aspect of the invention, the solid phase separation is selected from the group comprising filtration, pressing, centrifugation, or any combination thereof, wherein at least 50% to 90% of the suspended solids are removed from the effluent. In one aspect of the invention, the separation of the aqueous phase comprises multi-effect evaporation using multiple evaporation units at different pressures or vacuums to achieve energy efficiency. The removed aqueous phase can be used in boilers or in palm oil mill processing to achieve cost savings in raw water treatment. In one aspect of the invention, the sequence of evaporation units in a PACI? ίη / ZZΖΠZ / E / YΙΛΙ The multi-effect evaporation system is changed after a predetermined time or upon detecting a predetermined value of viscosity, moisture content, solids content or oil content of the effluent, to reduce scaling in the evaporators. In one aspect of the invention, the separation of the oil phase from the effluent comprises the mechanical separation of the oil phase from the residual sludge by sedimentation in an intermediate tank and centrifugation. The oil recovered from the EMAP can generate revenue for palm oil milling plants. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow diagram illustrating a procedure for treating the effluent from the palm oil milling process according to the present invention. Figure 2 is a flow diagram illustrating a one-stage preconditioning process in the treatment of the effluent from the palm oil milling process according to the present invention. Figure 3 is a flow diagram illustrating a solids removal process in the treatment of the effluent from the palm oil milling process according to the present invention. Figure 4 is a flow diagram illustrating a water removal process in the treatment of the effluent from the palm oil milling process according to the present invention. Figure 5 is a flow diagram illustrating an oil extraction process in the treatment of the effluent from the palm oil milling process according to the present invention. Figure 6 is a flow diagram illustrating a method for treating residual sludge from the palm oil milling process according to the present invention. Figure 7 is a flow diagram illustrating a solvent extraction process on the dry solids recovered from solids removal and processing of the residual sludge. DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in more detail with reference to the accompanying figures, which show preferred embodiments of the invention. However, this invention can be incorporated in many different forms and should not be interpreted as being limited to the embodiments set forth herein; rather, these embodiments are provided so as to make this description complete and fully convey the scope of the invention to those skilled in the art. With respect to Figure 1, the present invention relates to a method for treating the effluent produced from a palm oil milling process. Figure 1 shows The process comprises three main stages of solids removal (20), water removal (30), and oil extraction (40) from the effluent to produce a residual sludge. The three main stages of the method are closely integrated and designed to work in this particular sequential order of solids, water, and oil removal. The three main stages are interrelated in that each stage enables the next step to achieve higher performance under economically feasible conditions. The residual sludge is produced after oil extraction (40) and undergoes a stage of recycling, drying, or a combination thereof (50). The solids removed from the effluent are converted into dry products, while the water removed from the effluent is reused in the palm oil milling process.The oil extracted from the effluent is crude palm oil, with a quality similar to that recovered in the oil milling process, and can be further processed to obtain palm oil products. In a preferred embodiment, the effluent addressed in the present invention is the palm oil mill effluent (PAM). PAM is the wastewater produced from the processing of fresh fruit bunches (FFB). PAM comprises the sludge following clarification or oil recovery from the sterilizer condensate, the pressed liquid from small fruits, and the liquor from the pressed empty palm fruit bunches (OFB). PAM is typically a thick, brown, colloidal water slurry with a high biochemical oxygen demand and high levels of suspended and dissolved solids. The typical average ratio of suspended to dissolved solids is between 1:1 and 1:2; the actual ratio varies from mill to mill due to factors such as soil, clone, handling, and milling process. Figure 2 illustrates the preconditioning stage method, preceding the solid phase separation stage. The preconditioning stage (10) is an optional stage that depends on the actual configuration of the palm oil mill. In a preferred embodiment, this preconditioning stage (10) can be multi-stage with the objective of removing coarse fibrous solids, sand, and excess solids from the effluent. Thus, the preconditioning stage, by way of non-limiting example, involves a vibrating screen (11) followed by a cyclone for grit removal (12), in order to precondition some or all of the effluent that still contains coarse fibrous solids and sand. The preconditioning stage (10) may further involve a settling tank (13) to remove excess solids such as fine sand and organic matter, if these solids have not been removed during the milling process. With reference to Figure 3, the solid removal (20) comprises one or more separation devices (21) for removing the solids from the effluent. In a preferred embodiment, the removal of at least 50%–90% of the solids is required. In a more preferred embodiment, at least 60%–90% of the solids are removed. Taking into consideration the results PACI? ίη / 77Ω7 / B / YILI technical and cost factors, 90-95% solids removal is preferred. 99% solids removal would be ideal, but would incur higher costs. Solids removal (20) comprises single-stage or multi-stage equipment operating in series or parallel to remove solids. The use of multi-stage equipment has advantages as it allows the separation of solids with different physical properties. An example of multi-stage equipment includes multiple filters that have sieves or membranes with different mesh or pore sizes. The removal of solids in the present invention can be carried out using a method selected from the group comprising filtration, pressing, centrifugation, or any combination thereof. Any other equipment capable of performing a solid-liquid phase separation can be used in the solid phase separation. The separated solids need not be completely dry, and a moisture content of less than 80% would be acceptable. The filtration equipment may be selected, but is not limited to, continuous filters comprising vacuum belt filters, rotary drum filters, rotary disc filters and belt press filters, tangential flow filters or batch filters comprising filter presses, membrane filters, horizontal disc filters, leaf filters, hose filters, tower filters and multi-element spark plug filters, and bag filters. An example of a pressure-based means for separating the solid phase is a rotary press. Alternatively, a centrifuge can be used as a two-phase decanter / separator, which can separate solids and liquids, with the separated solids having a moisture content of less than 80%. Depending on the method used to remove suspended solids, some of the dissolved solids will be removed simultaneously as moisture in the wet removed solids. As a result of this effect, it can be advantageous to have a high moisture content in the removed solids to simultaneously reduce the dissolved solids in the residual sludge. In a preferred embodiment, the moisture content of the removed solids is as high as 80%. In another preferred embodiment, the moisture content of the removed solids can be as low as 40%. The removed solids are dried to obtain dry products with a moisture level of less than 15%, in bulk, and are stored in separate silos to facilitate storage, transport and sale, or further processing. Figure 4 illustrates the water removal (30) in the treatment of EMAP using evaporation units (31) according to the present invention. In a preferred embodiment, a plurality of multiple-effect evaporators may be employed, using any combination of—but not limited to—common evaporator designs, such as a multi-effect evaporator. PACI? ίη / ZZΖΠZ / E / YΙΛΙ Falling film evaporator, forced circulation evaporator, natural circulation evaporator, batch tray evaporator, renewed film evaporator, rising film evaporator, plate-type evaporator, falling film tubular evaporator, and rising / falling film tubular evaporator. All these evaporators can be arranged in a forward or reverse feed configuration. Multiple-effect evaporation uses the steam produced in one evaporation unit to provide the heat needed to evaporate the product in a second evaporation unit, which is maintained at a lower pressure. In a two-effect evaporator, approximately 2 kg of product vapor can be evaporated for every kg of steam supplied. As the number of effects increases, the cost-effectiveness of supplying steam to the evaporation process also increases. The evaporation in the present invention can be incorporated with the use of thermal vapor recompression (RTV) and mechanical vapor recompression (RMV), to improve the economy of evaporation. The water evaporated or removed by evaporation will be clean and clear water that can be recycled either to the mill or to a boiler in the palm oil grinding process. The water specifications are as follows: pH 5-6, TS ~ 150 ppm, BOD ~ 20 ppm. Evaporation is carried out to remove at least 50% of the moisture, and preferably, between 60-75% of the moisture. Theoretically, depending on the percentage of suspended and dissolved solids in the feed, it is possible to remove more than 85% of the moisture by evaporation. PACI? ίη / 77Π7 / E / YΙΛΙ Effluent After 50% Water Removal After 60% Water Removal After 75% Water Removal Oil 1% 1.9-2.0% 2.3-2.4% 3.3-3.6% Solids 3-6% 6-11% 7.0-13.6% 10.8-19.8% Suspended Solids 1-2% 1.9-3.7% 2.4-4.5% 3.6-6.6% Dissolved Solids 2-4% 3.9-7.5% 4.7-9.1% 7.1-13.2% Water 93-96% 87-92% 84-91% 77-86% Total 100% 100% 100% 100% Table 1 Approximate ratio of oil, solids and water at different stages without solids removal Table 1 shows that the percentage of oil increases as a greater percentage of water is removed. Theoretically, oil recovery is possible without removing solids. However, in practice, there are four problems with oil recovery without solids removal. This refers to the case where the initial solids concentration is 6%. First, at 75% water removal, the water percentage is too low, causing the sludge to become too viscous to flow through the evaporation units. Therefore, water removal will be subject to an upper limit of approximately 60–75%. Secondly, with over 60% water removal, the percentage of solids is too high for most current centrifugation equipment. Therefore, oil recovery is a problem at higher water removal rates, but oil recovery efficiency will be severely compromised at lower water removal rates. Third, since it is only possible to target around 60% water removal without first removing the solids, this will not only reduce oil recovery but also result in a larger quantity of residual sludge. The eventual drying process will require more heat energy, or else there may be too much sludge to recycle. Finally, solids, especially larger particles, are prone to sticking to the tubes of evaporation units and causing scaling problems. For example, without solids removal, and at 60% water removal, oil recovery is approximately 56% and the amount of residual sludge is approximately 44% at EMAP. PACI? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Effluent After 50% Suspension Removal After 50% Water Removal After 60% Water Removal After 75% Water Removal Oil 1% 1% 1.9-2.0% 2.3-2.4% 3.5-3.7% Solids 3-6% 2.5-4.9% 4.8-9.3% 5.9-11.3% 9.0-16.7% Suspended Solids 1-2% 0.5-1.0% 1.0-1.9% 1.2-2.3% 1.8-3.4% Dissolved Solids 2-4% 2-3.9% 3.8-7.3% 4.7-8.9% 7.1-13.2% Water 93-96% 94-97% 89-93% 86-92% 80-87% Total 100% 100% 100% 100% 100% ΡΑΓΉ ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Table 2 Approximate ratio of oil, solids and water at various stages with 50% removal of suspended solids with 80% moisture According to Table 2, comparing 50% and 75% water removal, the oil concentration increased from approximately 2% to 3.5%. The current oil recovery method, using a centrifugal method such as a decanter or separator, will have a residual oil concentration of 0.6%–1% remaining in the sludge. Therefore, the higher oil concentration implies a higher oil recovery percentage. In conclusion, water removal has a direct impact on oil recovery from the sludge. A higher percentage of water removal will result in a higher percentage of oil recovery. However, water removal is subject to a maximum limit beyond which the sludge will still flow during the water removal process. In the case of evaporators, depending on their design, each design will have a different limit, but the common denominator is the percentage of solids in the sludge, especially suspended solids. According to Table 2, although the oil concentration remains similar, as without solids removal, water removal of between 60% and 75% is possible depending on the initial solids content, resulting in better oil recovery and also less residual sludge to be dried or recycled. For example, with 50% removal of suspended solids and 75% removal of water, oil recovery is greater than 70% and the amount of residual sludge is approximately 29% of the EMAP. Therefore, the advantages of removing at least 50% of suspended solids include a higher oil recovery rate of 70%, residual sludge less than 30% of the EMAP, and simplified drying and / or recycling of the residual sludge due to its lower volume. Furthermore, fewer solids mean fewer particles adhering to the evaporator tubes and causing scaling problems. Effluent After 90% removal of suspended solids After 50% water removal After 60% water removal After 75% water removal Oil 1% 1% 1.9-2.0% 2.3-2.4% 3.5-3.7% Solids 3-6% 2-4% 4.0-7.6% 4.9-9.3% 7.5-13.9% Suspended solids 1-2% 0.1-0.2% 0.2-0.4% 0.2-0.5% 0.4-0.7% Dissolved solids 2-4% 2-3.8% 3.8-7.2% 4.7-8.8% 7.1-13.2% Water 93-96% 95-97% 90-94% 88-93% 82-89% Total 100% 100% 100% 100% 100% PACI? Ln / Zznz / E / YIAI Table 3 Approximate ratio of oil, solids and water at various stages with 90% removal of suspended solids at 80% humidity Table 3 shows the approximate oil, solids, and water ratios of the effluent after 90% solids removal from suspended solids at 80% moisture and after 50%, 60%, and 75% water removal. The figures in the table demonstrate the importance of solids removal before the evaporation stage. With 90% suspended solids removal in the first stage, the solids content of the standard effluent was reduced from 3–6% to 2–4%. With 90% removal of suspended solids, it is possible to remove more than 75% of the water. Depending on the initial solids content, it is possible to remove 80-85% of the water. With 75% water removal, oil recovery is over 70% and the amount of residual sludge is only about 28% of the EMAP. At 80% water removal, oil recovery is over 76% and the amount of residual sludge is only about 23% of the EMAP. In one embodiment of the present invention, the sequence of the evaporation units is changed after a predetermined time to reduce fouling problems in the evaporation unit tubes, or upon detection of a predetermined value for viscosity, moisture content, solids content, or oil content of the effluent in the evaporation units. Measurements of viscosity, moisture, solids, or oil content can be taken at certain intervals to determine whether a change in the sequence is necessary. The moisture, solids, or oil content can be measured by a 3- to 5-minute centrifugation test of a sample taken from the effluent. Scale buildup in evaporation units typically develops in the later effects where the liquid is thick and viscous. Therefore, in this invention, the evaporator design allows for changing the sequence of the evaporation units by utilizing the readily flowing feed effluent to clean the evaporator tube without downtime. Aside from the temperature and pressure difference, which requires a short adjustment time of several minutes depending on the equipment size, the evaporator continues to function and evaporate water as normal; only the effect sequence has changed. This ability to change the sequence of the evaporation units is advantageous. Total 100% 100% 100% 100% 100% PRCfr Ln / Zznz / E / YIAI Table 2 Approximate ratio of oil, solids and water at various stages with 50% removal of suspended solids with 80% moisture According to Table 2, comparing 50% and 75% water removal, the oil concentration increased from approximately 2% to 3.5%. The current oil recovery method, using a centrifugal method such as a decanter or separator, will have a residual oil concentration of 0.6%–1% remaining in the sludge. Therefore, the higher oil concentration implies a higher oil recovery percentage. In conclusion, water removal has a direct impact on oil recovery from the sludge. A higher percentage of water removal will result in a higher percentage of oil recovery. However, water removal is subject to a maximum limit beyond which the sludge will still flow during the water removal process. In the case of evaporators, depending on their design, each design will have a different limit, but the common denominator is the percentage of solids in the sludge, especially suspended solids. According to Table 2, although the oil concentration remains similar, as without solids removal, water removal of between 60% and 75% is possible depending on the initial solids content, resulting in better oil recovery and also less residual sludge to be dried or recycled. For example, with 50% removal of suspended solids and 75% removal of water, oil recovery is greater than 70% and the amount of residual sludge is approximately 29% of the EMAP. Therefore, the advantages of removing at least 50% of suspended solids include a higher oil recovery rate of 70%, residual sludge less than 30% of the EMAP, and simplified drying and / or recycling of the residual sludge due to its lower volume. Furthermore, fewer solids mean fewer particles adhering to the evaporator tubes and causing scaling problems. Effluent After 90% removal of suspended solids After 50% water removal After 60% water removal After 75% water removal Oil 1% 1% 1.9-2.0% 2.3-2.4% 3.5-3.7% Solids 3-6% 2-4% 4.0-7.6% 4.9-9.3% 7.5-13.9% Suspended solids 1-2% 0.1-0.2% 0.2-0.4% 0.2-0.5% 0.4-0.7% common to evaporation units. In a preferred embodiment, the evaporation units are grouped into a plurality of clusters, each comprising at least two evaporation units adjacent to each other in sequence, and the sequence of the evaporation units is changed by switching between the clusters of evaporation units. For example, changing the first and second evaporation units to the penultimate and last evaporation units simplifies the arrangement of the evaporation units and makes it more cost-effective. In another example, for a 3-effect evaporator, simply swapping the evaporation units of the first and third effects would suffice. For a 5-effect evaporator, simply replacing the evaporation units of the fourth and fifth effects as a whole with those of the first and second effects would greatly simplify the design and construction. The evaporation unit described herein shall be interpreted as an evaporator device, evaporator body, or partition within an evaporator in which a single evaporation effect is carried out in a multi-effect evaporation system. Evaporation units may be provided in a parallel configuration as shown in the following examples. It is also possible to build the evaporator with multiple first or second effect evaporation units operating in parallel, but some of these first or second effects can be made to operate as last and / or penultimate effects, while the last and / or penultimate effects function as first or second effects on those occasions. For example, in a three-effect evaporator, it's possible to have two or more first-effect evaporation units, and one or more of these first effects can swap sequences with the last effect. In a five-effect evaporator, it's possible to have two or more first-effect evaporation units and two or more second-effect units. In this case, simply swapping the fourth or fifth-effect units with the first-effect units would suffice. It is also possible to achieve a similar result of scale reduction by dividing an evaporator into multiple evaporation units so that multiple-effect evaporation can be carried out within the same evaporator, and changing the sequence of the evaporator units as described above. Figure 5 illustrates the extraction of oil (40) from the effluent after water removal (30), comprising centrifugation (41) of the effluent, heating of the effluent, feeding the effluent to an intermediate tank, and mechanical separation of the oil layer in the intermediate tank, removing the oil layer floating on top of the PACI? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ tank. The centrifuge used for mechanical separation can be a two- or three-phase decanter or a two-phase separator capable of separating the oil from the liquid. At this stage, the oil content of the effluent is reduced to less than 1%, forming a residual sludge. Based on Tables 2 and 3, the removal of solids and water increases the oil concentration from 1% in the feed to between 2 and 3.7% after a water removal of 60–75%. At this concentration of 2–3%, the oil recovery from the effluent after the removal of solids and water increases. After separation of the oil phase, residual sludge is produced, which, in one example, may still contain approximately 0.5–1% oil, 5–9% solids, and 90–94% water, with a volume between 20–40% of the original input. The residual sludge undergoes further processing as shown in Figure 6. In a preferred embodiment, the residual sludge is subjected to recycling, drying, or a combination of both (50). By recycling the residual sludge back into the process (51), it can be used as dilution water for the press station or the clarification station. In this way, no liquid is discharged as effluent and, therefore, no oil loss can occur. Alternatively, the residual sludge (52) is dried to reduce its moisture content to less than 15% to facilitate storage, transport, and sale or further processing. The low moisture content allows the solid to be stored for a period of time without deterioration of quality. The drying apparatus (54) that may be used includes a rotary drum dryer, spray dryer, vacuum dryer, or any other suitable design of drying machinery, along with thermal energy from any combination of boiler discharge, high-pressure boiler steam, or low-pressure backpressure receiver steam (turbine discharge steam), or any other heat source, if available. Another embodiment is the use of a combination of recycling and drying (53) in the treatment of residual sludge. This minimizes the addition of water to the grinding process while simultaneously eliminating the need for additional heat energy from steam to dry the residual sludge. In this recycling and drying combination, more solids are removed using a solids removal system with separation machinery (55) of different specifications compared to solid-phase separation. A percentage of 90–99% of the solids in the residual sludge is removed. The moisture content of the removed solids can be high, allowing for the removal of more solids, including dissolved solids, and this moisture content can be adjusted based on the available heat energy from the boiler discharge.The liquid, after the removal of solids, is fed to an intermediate and can be reheated to a required temperature before recirculation. PACI? ίη / ZZOZ / E / YILI to the press or clarification station in the milling process. Sludge temperature is a crucial parameter throughout the entire process and is closely monitored, controlled, and optimized for performance and energy efficiency. Aside from the evaporation stage, the sludge is maintained at 90 degrees Celsius or higher wherever possible. An example of a solids removal system that can be used in a drying and recycling combination is a membrane filter press. By recycling the filtrate as dilution water, the actual EMAP to be removed by the evaporator is only 0.41 per 1 ton of processed fresh fruit bunches instead of the standard 0.61 per 1 ton of fresh fruit bunches. The boiler discharge would be sufficient to dry the solids removed from both the solid-phase separation and the residual sludge dried to a moisture content of less than 15%. The decanter cake from the normal oil milling and preconditioning stages, if applicable, can be added to the drying process to increase the amount of dry solids. The dry solids will be stored in silos before further processing in the mill. The dry solids can also be sold or transported to a centralized processing plant for further processing. The dry solids will have an average protein content of 8–13% and fiber of 3–16%, plus an oil content of 3–5%. Therefore, the dry solids can be sold as is for their protein value, or the oil can be recovered first through solvent extraction, and solids with less than 1% oil can be sold separately for their protein value as animal feed. They also contain minerals such as calcium (Ca), phosphorus (P), magnesium (Mg), and potassium (K) between 0.2% and 1%, making it possible to sell them as organic fertilizer. The mineral content can be recovered separately to increase the concentration and improve their nutritional value as organic fertilizer. The dry solids also contain a high level of ether extract, between 20–40%, which increases the energy content but also creates a rancidity problem during storage. In a preferred embodiment, the present invention separates the different solid fractions in the residual sludge, making use of the physical properties of each fraction. Since the solids were removed in different stages, using equipment with different operating parameters and multiple steps in each stage, it is possible to adjust the solid separation parameters at each stage to remove solids with a higher concentration of a certain particle size. For example, the use of multi-stage filtration with pores of varying sizes allows for the removal of solids with a high initial sand concentration, subsequently PACI? ίη / 77P7 / E / YILI fiber and eventually protein. The use of centrifugation or tangential flow filtration in the later stage after 95-99% of suspended solids have been removed, allows the removal of specific minerals if the economy justifies the use of such equipment. It is possible to handle the solids separately, from drying to oil recovery. Drying and storage can be done in batches or using smaller drying units and silos for each fraction. In a further process, the recovered solid phase is subjected to solvent extraction (60) to recover the oil from the solids. Solvent extraction comprises soaking or washing the solids with the solvent, recovering the solvent, and distilling the solvent to recover the oil, as shown in Figure 7. The solvent used can be a flammable solvent such as hexane, or a non-flammable solvent such as trichloroethylene, depending on the application of the solids and the oil after processing. A typical solvent extraction plant is designed with an extractor (62) and a desolventizing roaster (DT) (64) operating sequentially to recover oil from solids. In extreme cases, where economics warrant it, the solvent extraction plant may be designed with multiple sets of extractors (62) and desolventizing roasters (DT) (64) operating in parallel to handle different solid fractions. However, the distillation portion may be shared among the multiple extractors (62) and desolventizing roasters (DT) (64). The solvent extraction plant may be located within the mill or separately. When the solvent extraction plant is separate from the mill, the dried solids of this invention are stored in silos at the mill and transported to a centralized solvent extraction plant for further extraction. This centralized solvent extraction plant is typically located near a port to facilitate the export of the dried solids. In the solvent extraction process, the dry solids received from the mills may be powders mixed with lumps, depending on the drying operation and the mill design. There may be a need to precondition (61) the solid into a form suitable for solvent extraction. For example, the solid is ground into a powder and then pelletized. The lumps can be removed, and only the powder needs to be formed into pellets. Subsequently, in the extraction process, the solvent needs to soak, wash, or rinse the dried products in several cycles and stages, using solvent with a high to low oil content as the solids move through the extractor (62). The extractor design can be a horizontal bed extractor, a rotary extractor, or a loop extractor. The prepared material enters the extractor by solvent through a rotating air seal. The material is then distributed across the width of the extractor in a manner PACI? ίη / ZZΖΠZ / E / YΙΛΙ uniform, resting on a perforated plate or sieve of the appropriate size to retain the solid. The solids move from the inlet to the outlet of the extractor at a speed that can be varied depending on the feed rate. The solvent flow is typically countercurrent to the flow of the dry product. The solvent is fed from the top of the extractor above the material and is distributed evenly across the extractor's width to thoroughly soak the dry product. The solvent is then collected at the bottom of the conveyor. Fresh solvent with little to no oil content is introduced into the extractor at the material discharge end. This low-oil solvent is used to extract the oil from the dry solids at the discharge end, which also have a low oil content. The oil content of the solvent increases from low to high as it flows from chamber to chamber in the opposite direction to the material flow. The solvent will overflow from one chamber to the next due to the continuous feed of fresh solvent at the material discharge end.The solid leaving the extractor will have an oil content of less than 1%. At the same time, the micelle, which is a liquid containing solvent with extracted oil, will leave the extractor on the material inlet side with an oil content of less than 10%. The micelle will be subjected to a distillation process (63) to recover the oil, while the recovered solvent will be recycled to the extractor. The solids leaving the extractor contain solvent, which is also recovered in a desolventizing roaster (DTR) (64). Inside the DTR (64), the material is subjected to continuous heating to evaporate the residual solvent. The dripping of solids from one layer to the next creates a swirling effect that aids in solvent recovery. The vapor from the DTR contains a high concentration of solvent and is condensed by a condenser (65) to recover the solvent. The micelle, a liquid containing solvent and recovered oil, is fed to the distillation section (63), where the solvent evaporates from the liquid, leaving the oil behind. The solvent is then recovered by another condenser (65). This operation can be multi-stage to gradually increase the oil concentration as the liquid passes through the distillation apparatus. At the end of the distillation process, the oil is completely separated from the solvent (<100 ppm).The quality of this oil may deteriorate slightly due to exposure to the heat of the drying process and the storage time before treatment. However, it is still a valuable product with a value of at least 50% of normal oil. The recovered solvent can be recycled back into the process. The dried and deoiled solids may contain less than 1% oil, 8-16% protein, and 10-25% fiber. Consequently, the solid can be sold as a whole, or its many different fractions can now be sold separately for their high fiber content, high protein value, or nutritional value as fertilizer. ΡΑΓΉ ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Although the present invention has been described in a specific embodiment as in the preceding description, it is understood that the preceding description does not limit the invention to the details given above. It will be evident to those skilled in the art that various changes and modifications can be made to it without departing from the principle of the invention or the scope of the appended claims. PACI? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ NOVELTY OF THE INVENTION Having described the invention as above, it is considered novel and therefore claimed as property, as contained in the following:

Claims

1. A method for removing water from the effluent produced from a palm oil milling process, comprising: performing multiple-effect evaporation on the effluent with a plurality of evaporation units; characterized in that the method further comprises changing the sequence of the evaporation units to carry out the multiple-effect evaporation.

2. The method for removing water from the effluent produced from a palm oil milling process according to claim 1, wherein the sequence of the evaporation units is changed after a predetermined time or upon detecting a predetermined value of viscosity, moisture content, solids content, or oil content of the effluent in the evaporation units.

3. The method for removing water from the effluent produced from a palm oil milling process according to claim 1 or 2, wherein the sequence of the evaporation units is changed by controlling the flow of effluent, steam and condensate in the ducts interconnecting the evaporation units.

4. The method for removing water from the effluent produced from a palm oil milling process according to claim 3, wherein the flow of effluent, steam, condensate in the conduits is controlled by at least one valve coupled to the conduits.

5. The method for removing water from the effluent produced from a palm oil milling process according to claim 3 or 4, wherein the conduits interconnecting the evaporation units are incorporated with at least one common header to form at least one common inlet or at least one common outlet so that the evaporation units allow changing the sequence of the evaporation units.

6. The method for removing water from the effluent produced from a palm oil milling process according to any of claims 1 to 5, wherein changing the sequence of the evaporation units comprises switching at least a first evaporation unit in sequence with at least a last evaporation unit or at least a penultimate evaporation unit in sequence.

7. The method for removing water from the effluent produced from a palm oil milling process according to any of claims 1 to 6, in PACI? ίη / ZZΖΠZ / E / YILI wherein changing the sequence of the evaporation units comprises switching at least a second evaporation unit in sequence with at least a last evaporation unit or at least a penultimate evaporation unit in sequence.

8. The method for removing water from the effluent produced from a palm oil milling process according to any of claims 1 to 7, wherein the evaporation units are assembled into a plurality of groups, each group comprising at least two evaporation units adjacent to each other in sequence, and changing the sequence of the evaporation units comprises switching between the groups of evaporation units.

9. The method for removing water from the effluent produced from a palm oil milling process according to claim 8, wherein the first group of evaporation units in the sequence is switched with the last group of evaporation units in the sequence.