FIELD OF INVENTION

This invention relates to a post-treatment for vegetable oil mill effluent. More particularly, the present invention relates to a method of recovering oil from palm oil mill effluent involving the use of a ceramic membrane system.

BACKGROUND OF INVENTION

Vegetable oils are found to be useful in many applications such as food or for cooking, as oleochemical feedstock, a lubricant, or as a biofuel. Extraction of the vegetable oils is usually done by pressing method, particularly wet pressing method which produces a large quantity of vegetable oil mill effluent, consisting of water-soluble vegetable components and suspended materials including fibres and oil. Palm oil is among the most rapidly growing vegetable oil industry because of its versatility in many areas.

Palm oil mill effluent (POME) is a wastewater generated from palm oil milling activity. Typically POME contains 95-96% water, about 1% oil, and 4-5% total dry content of which the suspended matter makes up 2-4%. Main source of solids includes sterilizer condensate, separator sludge, and hydrocyclone wastewater. Composition wise POME also produces quite a considerable biochemical and chemical effluent load which typically carries chemical oxygen demand (COD) of 30-100 gco _D L and biological oxygen demand (BOD) of 25-60 g _C0 D L.PME is also acidic and has a pH varying from 3.0 to 6.5. Hence, discharge of the untreated POME will create adverse impact to the environment.

Despite the pollutant contained in POME, POME also contains high concentrations of recoverable protein, carbohydrate, nitrogenous compounds, lipids and minerals that may be converted into useful materials. It is desirable to treat the POME prior to discharge to recover useful materials as well as reducing environmental burden. Research effort has been put to method of recovering oil from vegetable oil mill effluent, and more particularly from POME. Through the process of oil recovery, pollutants in the oil mill effluent can be effectively reduced. There are few patented technologies over the prior art relating to systems and methods of treating oil mill effluent. However, there is a wide variation in the system designs and qualities as well as the methods. PCT Publication No. WO 2013169091 has disclosed a treatment method for POME comprising the steps of a pre-treatment and subsequently followed by a biological treatment and a membrane separation treatment. The pre-treatment involves the use of aerobic/clarifier system for waste oil/sludge recovery while the biological treatment involves the production of biogas from the POME in order to reduce the BOD to an acceptable level. Membrane separation treatment is performed on the wastewater from POME for reuse or recycles.

Another PCT Publication No. WO 2014051415 has disclosed a portable oil recovery system for POME using chemical reaction and centrifugal separation in order to recycle POME, which is commonly disposed and environmentally harmful, and to produce reusable oil. Catalytic reaction takes place within the POME to separate impurities which are insoluble in natural oil and readily separable as sludge. A three-phase centrifuge is used to separate natural oil from the mixture. The disclosed invention can be used in various locations for multiple POME ponds due to its portability.

However, the inventions provided in the prior art still possesses some drawbacks. The recovered oil usually has a much lower free fatty acid value and comparatively not as fresh as the crude palm oil. Hence, the recovered oil has a much lower commercial value as the crude palm oil. Further, the prior art still is not able to meet the sustainable development requirement, in which the system or process itself has to be environmental friendly as well as concurrently reducing environmental burden from the discharged POME.

This invention provides a solution to the problems. SUMMARY OF INVENTION

One of the objects of the invention is to provide an improved method of recovering oil from vegetable oil mill effluent utilizing membrane technology.

Another object of the invention is to provide a system for recovering oil from oil mill effluent for the improved method including a ceramic membrane system.

Still another object of the invention is to provide an improved ceramic membrane module which can efficiently separate oil and water.

Yet another object of the invention is to develop a method of treating vegetable oil mill effluent which can recover oil therefrom and concurrently reduce environmental burden of the discharged effluent.

Again another object of the invention is to recover oil from vegetable oil mill effluent which can be as fresh as the crude vegetable oil. The recovered oil has a comparative free fatty acid value as the crudely extracted vegetable oil.

At least one of the preceding aspects is met, in whole or in part, by the present invention, in which the embodiment of the present invention describes a ceramic membrane module comprising a cylindrical housing having an inlet at one end, a permeate outlet at other end, and retentate outlets at the outer peripheral wall surface of the housing; and a porous ceramic membrane having a plurality of through- channels disposed within the housing and extended from one end of the housing to another end of the housing, wherein the pore size is 1-5000 nm and the molecular weight cut-off is 1,000-10,000,000 Da, wherein the ceramic membrane is supported by material made from Ti0 ₂ , Zr0 ₂ , Al ₂ 0 ₃ , SiC, or any two or above.

In a preferred embodiment of the invention, the housing is a circular cylinder or a hexagonal cylinder and the cross-sectional shape of the through-channels is a circle, square, pentagon, or hexagon. In another preferred embodiment of the invention, the number of channels is 1-900.

Still in another preferred embodiment of the invention, the ratio of the length to the diameter of the module is 0.1-1000.

A further embodiment of the invention is a method of recovering oil from a vegetable oil mill effluent comprising the steps of reducing viscosity of the effluent by heating to a temperature of 50-95 °C filtering the heated effluent to remove solids; passing the treated effluent into a ceramic membrane module as described in any of the preceding description to separate of oil and water into a filtrate and a concentrate; and recovering oil by centrifuge the concentrate from the ceramic membrane module. In another further embodiment of the invention, the treated effluent is passed into the ceramic membrane module at a flow rate of 30,000-50,000 kg/hour (30-50 ton/hour).

The preferred embodiment of the invention consists of novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings and particularly pointed out in the appended claims; it being understood that various changes in the details may be effected by those skilled in the arts but without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated.

FIGURE 1 is a front view of a ceramic membrane system as embodied by one of the preferred embodiments of the invention. FIGURE 2 is an elevated view of a ceramic membrane system as embodied by one of the preferred embodiments of the invention.

FIGURE 3 is a side view of a ceramic membrane system as embodied by one of the preferred embodiments of the invention.

FIGURE 4 is a perspective view showing part of a ceramic membrane system as embodied by one of the preferred embodiments of the invention.

FIGURE 5 is a perspective view of a ceramic membrane module as embodied by one of the preferred embodiments of the invention.

FIGURE 6 is a perspective view of through-channels within a ceramic membrane module as embodied by one of the preferred embodiments of the invention.

FIGURE 7 is an example of a system for recovering oil from palm oil mill effluent as embodied by one of the preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a post-treatment for vegetable oil mill effluent More particularly, the present invention relates to a method of recovering oil from palm oil mill effluent involving the use of a ceramic membrane system.

Hereinafter, the invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings. However, it is to be understood that limiting the description to the preferred embodiments of the invention and to the drawings is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim. The invention discloses a ceramic membrane module (1) comprising a cylindrical housing (2) having an inlet (5) at one end, a permeate outlet (7) at other end, and retentate outlets (6) at the outer peripheral wall surface of the housing (2); and a porous ceramic membrane (3) having a plurality of through-channels (4) disposed within the housing (2) and extended from one end of the housing (2) to another end of the housing (2), wherein the pore size is 1-5000 nm and the molecular weight cut-off is 1,000-10,000,000 Da, wherein the ceramic membrane (3) is supported by material made from Ti0 ₂ , Zr0 ₂ , A1 ₂ C>3, SiC, or any two or above.

Referring now to FIGURE 1 to 3, there is shown a perspective view of the ceramic membrane module (1) comprising a cylindrical housing (2) and a plurality of through-channels (4) of porous ceramic membrane (3) in accordance with the invention. The cylindrical housing (1) has an inlet (5) at one end of the housing (2), a permeate outlet (7) at another end of the housing, and at least two retentate outlets (6) at the outer peripheral wall surface of the housing (2). Feed is introduced to the module through the inlet (5) and permeate is removed through the porous through- channels (4) and removed through the permeate outlet (7) while the retentate is removed through the retentate outlet (6). Preferably, the housing (2) can be made from metal, plastic, or ceramic. More preferably, the housing (2) is made from stainless steel.

According to the preferred embodiment of the invention, the plurality of through-channels (4) of porous ceramic membrane (3) is linearly disposed within the housing (2) and extended from one end of the housing (2) to another end of the housing (2). The channels (4) are preferably distributed symmetrically but may not necessary to be uniformly. The ceramic membrane (3) is supported by a porous material which provides mechanical strength to the membrane without significant flow resistance. The support material is preferably without limiting to titanium oxide (Ti0 ₂ ), zirconium oxide (Zr0 ₂ ), aluminium oxide (Al ₂ Os), silica carbide (SiC), or any combination thereof. The pore size of the ceramic membrane (3) is preferably 1 nm to 5000 nm or in terms of molecular weight cut-off is preferred to be 1,000 Da to 10,000,000 Da. The pores are preferably in an interconnected network structure which can provide extra mechanical strength to the ceramic membrane module (1). As described by the preferred embodiment of the invention, the ceramic membrane module (1) can be configured to be in any size or shape that is suitable to be used for various purposes. More particularly, the cylindrical housing (2) of the module can be either a circular cylinder or a hexagonal cylinder, without deviating the efficiency and functionality of the module. The length of the housing (2) is preferably ranged from 0.1 m to 10 m while the diameter of the housing (2) is preferably ranged from 1 cm to 100 cm, depending on the desired yield of a process. In another word, the ratio of the length of the module (1) to the diameter of the module (1) is preferably ranged from 0.1 to 1000. With such configuration, the module (1) can be readily be transported, mounted, and manufactured.

In accordance with the preferred embodiment of the invention, the through-channels (4) of porous ceramic membrane (3) can also be configured to be in any size or shape that is suitable to be used for various purposes. More particularly, the cross-sectional shape of channels (4) can be a circle, a square, a pentagon, or a hexagon. The number of channels (4) within the housing (2) can be 1 to 300, or even to 900. Diameter can be from 1mm to 100 mm. Length can be from 10cm to 200 cm, or even to 1000cm. The channels (4) can be of a combination of various diameters within the housing (2) for a higher surface area per unit volume, and hence increased permeate flow. The membrane thickness is carefully configured to achieve a balanced pressure drop across the housing to provide uniform and hence increased permeate flow. A positive pressure gradient is maintained to drive permeation through membrane and the support. The flow pattern in the housing (2) can be counter- current, co-current, or radial current with respect to the permeate flow in the channels (4).

The ceramic membrane module (1) is mainly for the use in liquid-phase separation, more particularly to separate oil and water. However, it is to be noted that the use of ceramic membrane module (1) shall not be limited to only in liquid-phase separation but can also be used in gas-phase separation. A further embodiment of the invention is a method of recovering oil from a vegetable oil mill effluent comprising the steps of reducing viscosity of the effluent by heating to a temperature of 50-95 oC; filtering the heated effluent to remove solids; passing the treated effluent into a ceramic membrane module (1) as described in any of the preceding description to separate of oil and water into a filtrate and a concentrate; and recovering oil by centrifuge the concentrate from the ceramic membrane module (1).

The vegetable oil can be of any oil derived from plant origin but palm oil, peanut oil, soybean oil, sunflower oil are preferred, and palm oil is most preferred. The effluent from the vegetable oil mill is fed into a treatment system to recover vegetable oil escaped to the effluent as well as to reduce harmful substances in the effluent so that it can be discharged with compliance with the government regulation.

In the further embodiment of the invention, vegetable oil mill effluent is transferred to a holding tank, preferably equipped with a heating device. The effluent is heated and maintained to a temperature of 50 °C to 90 °C, and preferably to a temperature of 60 °C to 80 °C. Heating of the effluent is essential prior to any filtration or separation process in order to reduce the viscosity of the effluent to a satisfactory level for a smooth flow of the effluent. Solid oil lumps are dissolved at such elevated temperature thereby reducing the effluent viscosity and a higher amount of oil can also be recovered in the later stage.

Suspended and insoluble solid substances are subsequently removed mechanically from the heated effluent, preferably by means of filtration and more preferably by means of micro- filtration. Preferably, the heated effluent is filtered with a self-cleaning scraper filter with 100- 500 mesh size. The residue which mainly consisting of fibres are discharged therefrom while the filtrate which mainly consisting of an aqueous mixture of vegetable oil, water, and other liquor is transmitted for subsequent treatment. Still in the further embodiment of the invention, the filtrate, or the treated effluent, is passed to a ceramic membrane module (1) as described in any of the preceding description to separate water from the aqueous mixture. The filtrate which mainly consisting of clear water can be discharged to wastewater pond for further post-treatment process. The remainders are the concentrate. The treated effluent is fed to the ceramic membrane module (1) by a feeding pump (8) so that the feed has a desired inlet flow rate to achieve a desired separation efficiency. Preferably, the inlet flow rate is 30,000 kg/hour (30 ton/hour) to 50,000 kg/hour (50 ton/hour) and most preferably 40,000 kg/ hour (40 ton/hour).

The concentrate is fed into a three-phase tricanter centrifuge to recover vegetable oil therefrom. The concentrate is separated into three phases: solid phase, light liquid phase, and heavy liquid phase. Recovered oil is contained within the light liquid phase while the watery-sludge is contained within the heavy liquid phase. The solid phase on the centrifuge bowl wall is discharged as fibre cake. The recovered oil can be transferred to a recovered oil tank for storage and the watery-sludge can be discharged. The discharged fibre cake and watery-sludge may be collected for other uses.

Again in the further embodiment of the invention, the method further comprises a step of cleaning the ceramic membrane module with a cleaning-in-process (CIP) system. CIP system is used to avoid the problem of dismantling the equipment as well as possible contamination of the recovered oil. An example of a system for recovering oil from a vegetable oil mill effluent for the method as described in any of the preceding description is illustrated herein. As illustrated in FIGURE 7, the system comprises a holding tank connected to a heating device to heat up the vegetable oil mill effluent contained in the holding tank. A filter is connected to the holding tank receiving heated effluent therefrom and removing solids from the heated effluent. A ceramic membrane module (1) is connected to the filter receiving filtered effluent from the filter and separating water from the aqueous mixture of the filtered effluent. A three-phase tricanter centrifuge is connected to the ceramic membrane module (1) to recover oil from the concentrate from the ceramic membrane module. The system further comprises a feeding pump (8) in between the filter and the ceramic membrane module (1) to feed the filter effluent from the filter to the ceramic membrane module (1) at a desired flow rate. The system further comprises a recovered oil tank for storage of the recovered oil from the tricanter centrifuge.

Although the invention has been described and illustrated in detail, it is to be understood that the same is by the way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims. EXAMPLE

The invention will now be illustrated, without limiting the scope of the invention, by the following examples.

Example 1

20,000 kg (20 ton) of palm oil mill effluent (POME) is pumped into a holding tank and is heated with steam to around 70 °C. The POME comprises around 0.96 % palm oil and 3.3 % suspended wet solid, which is mainly palm fruit fibre. The biochemical oxygen demand (BOD) of the POME is 41000 mg/m ³ . The heated POME is filtered with a 20 mu filter to remove the suspended solids from the heated POME. The filtrate is passed through a ceramic membrane module in which water is separated from the aqueous liquid. The BOD of the separated water is tested to be 396 mg/m . The separated clear water is discharged to wastewater pond for bio- treatment while the concentrate from the ceramic membrane module is passed through a three- phase tricanter centrifuge to recover the oil. The total oil recovered from the concentrate is 182 kg or the oil recovery is 94.8 %. Example 2

30,000 kg (30 ton) of palm oil mill effluent (POME) is pumped into a holding tank and is heated with steam to 60 °C to 80 °C. The POME comprises around 0.95 % palm oil and 3.0 % suspended solid, which is mainly palm fruit fibre. The biochemical oxygen demand (BOD) of the POME is 42000 mg/m ³ . The heated POME is filtered with a 20 mu filter to remove the suspended solids from the heated POME. The filtrate is passed through a ceramic membrane module in which water is separated from the aqueous liquid. The BOD of the separated water is tested to be 413 mg/m ³ . The separated clear water is discharged to wastewater pond for bio- treatment while the concentrate from the ceramic membrane module is passed through a three- phase tricanter centrifuge to recover the oil. The total oil recovered from the concentrate is 265 kg or the oil recovery is 93 %.

Example 3

30,000 kg (30 ton) of palm oil mill effluent (POME) is pumped into a holding tank and is heated with steam to 60 °C to 80 °C. The POME comprises around 0.92 % palm oil and 3.2 % suspended solid, which is mainly palm fruit fibre. The biochemical oxygen demand (BOD) of the POME is 41500 mg/m ³ . The heated POME is filtered with a 20 mu filter to remove the suspended solids from the heated POME. The filtrate is passed through a ceramic membrane module in which water is separated from the aqueous liquid. The BOD of the separated water is tested to be 407mg/m . The separated clear water is discharged to wastewater pond for bio- treatment while the concentrate from the ceramic membrane module is passed through a three- phase tricanter centrifuge to recover the oil. The total oil recovered from the concentrate is 262 kg or the oil recovery is 95 %.