WO2008150152A1

WO2008150152A1 - A continuous waterless biodiesel unit attached to a vegetable oil refinery.

Info

Publication number: WO2008150152A1
Application number: PCT/MY2008/000008
Authority: WO
Inventors: Ruslee Bin Hussain
Original assignee: Ruslee Bin Hussain
Priority date: 2008-02-05
Filing date: 2008-02-05
Publication date: 2008-12-11

Abstract

The invention discloses a method and a process to cost effectively manufacture biodiesel from refined vegetable oil via continuous transesterification by attaching a specially designed low temperature and low pressure waterless continuous biodiesel unit at vegetable oil refinery by Unking pipelines from the refined oil bulk stofage tank (1) directly to the reactor (9), thus eliminating the need to transport the refined oil feedstock, erecting a new storage tank facility, putting-up a new steam boiler and providing a huge land area as in the case of a new plant facility for the commercial production of palm biodiesel. Waste refinery heat is utilized by heat exchanger (7) to minimize the fuel use by thermal oil heater (8) for heating purposes in the specially designed reactors (9), (10), (11), (12), (13), (14), (15), biodiesel purifier (16) and glycerol purifier (17). As the processes of palm diesel separation and purification are continuous and waterless, there is no need for a water treatment plant and big tanks for big production capacity.

Description

A CONTINUOUS WATERLESS BIODIESEL UNIT ATTACHED TO A VEGETABLE OIL REFINERY.

[1] A continuous waterless biodiesel unit is a small biodiesel plant with a foot print of less than 232 square meter that is capable of producing biodiesel or methyl ester continuously without the requirement of any water treatment facility and also without the need to erect a new steam boiler. This biodiesel unit is attached to a vegetable oil refinery in order to produce biodiesel or methyl ester continuously and cost effectively. Technical Field

[2] The present invention relates to an improved method and a process of producing biodiesel or methyl ester with improved continuous production process without the need for any water washing processes. More particularly but not exclusively, it relates to an improved cost and production time to produce continuously large quantity of biodiesel or methyl ester as a substitute for petroleum diesel or methyl ester as a semi-processed feedstock for oleo-chemical plant from palm olein a refined vegetable oil. It has enormous low cost potential in producing bio-diesel or methyl ester from palm olein at Palm Oil Refinery as palm olein or RBD palm oil is a refined palm oil product of the refinery and it requires only low pressure and low temperature transesterification process which can utilize waste refinery heat. Background Art

[3] This invention is a continuation of an invention filed under PI20053542 in Malaysia on 1^st. August 2005. Palm biodiesel has of late been recognized as an efficient fuel substitute. In Malaysia, biodiesel has been successfully derived from palm oil. Patent No. PJ 1105/88 has revealed a process of producing palm oil methyl esters (palm diesel) from palm oil. Palm oil is converted into palm oil methyl esters via transesterification and the derived palm oil methyl esters or palm diesel have proven to exhibit good fuel properties and are able to be used as a diesel substitute. Production and evaluation of palm oil methyl esters as diesel substitute published in Elaeis Special Issue, November 1995, pp 15-25 discloses the fuel characteristics of palm diesel and also its potential to be used as a diesel substitute . (MPOB, Patent No. US2004/0231236 Al)

[4] Conventionally, palm diesel is prepared from palm oil or its derivatives by reacting with alcohol using a acid/alkali/enzyme catalyst in the temperature range of 40 °C-80°C under constant stirring for a period of 45 minutes to 2 hours. In order to achieve higher product conversion, 1 to 3 moles per moles of oil in excess to the stoichioOmetric quantity of alcohol is normally used and the unreacted alcohol is removed in the subsequent process steps. The ester obtained is separated from glycerine by gravity separation process and the ester is washed with water and mild acid.The product is purified further by evaporation to remove the unreacted alcohol and traces of moisture. The final product is normally used in combination with regular petroleum fuels to overcome the viscosity and related problems. Disclosure of Invention Technical Problem

[5] The major limitation associated with a new conventional Palm biodiesel Plant setup in Malaysia is that the overall production facility requires a major investment in having a big land area to house the new tank yard, a new plant building, a new administrative building, a new loading and unloading yard and a new steam boiler. In most cases it is estimated to cost around RM 40 million or more for a capacity of 60,000 MT per annum. Moreover, the bulk batch process or continuous process with water washing results in prolonged time, which may be as high as 2 to 4 hours and thereby enhancing the cost of the process significantly.

[6] Another limitation associated with these processes is that the process is batch separation or continuous requiring big reactor tank for bigger production capacity and uses large amount of water for purification of the product. A big and costly water treatment plant has to be built and it will add-up to the capital and operation cost of running the biodiesel plant.

[7] Water washing process requires more tanks to be built, more water separators needed and traces of water will conventionally needs to be removed by distillation which is an energy intensive process. The process of water washing esters would normally weaken the oxidative stability of the ester to as much as a factor of 2.5 times as stated in a patent application No. PCT/US2004/032637 and WO2005/037969A2 by The Dallas group of America, Inc. which avoided water washing by using an absorbent material invented by them. Technical Solution

[8] The main object of the present invention is to provide an improved process for the preparation of biodiesel or methyl ester which obviates the limitations as stated above.

[9] Another object of the present invention is to provide a continuous mechanical process for biodiesel separation and purification which overcome the need to wait for the product to settle in the reactor or a separate settling tank which has to later undergo water washing or chemical treatment or absorbent treatment for purification of the ester product.

[10] Still another object of the present invention is to utilize waste refinery heat by using heat exchangers or heating coils for processing heat requirements. [11] Yet another object of the present invention is to use mild steel pipes extensively instead of food grade stainless steel for tank construction.

[12] Still yet another object of the present invention is to connect pipeline from the refined vegetable oil storage tank tank directly to the reactor thus eliminating the construction of a big storage tank for keeping bulk feed stock.

[13] Accordingly the present invention provides an improved process for the preparation of biodiesel, which comprises;

[14] An area of 232 square meter or 2,500 square feet situated next to the refinery refined oil storage tank or fractionation plant housing 4 units to 12 units of mild steel pipe construction reactors of size 3Metric ton to lOMetric ton each preferably SMetric ton each with bottom stirrer capable of stirring at 1000 rpm or more, heating coil or heat exchangers, a vacuum evaporation system for the recovery of excess methanol and or ethanol, a custom designed continuous separator of capacity 12Metric ton per hour or more, a mild steel neutralization pipe vessels of size 5Metric ton or more and a second stage continuous 12Metric ton per hour or more custom designed purifier.

[15] Subjecting the mixture, as formed in [14] to separation of the esterified oil by known method continuous separation, followed by conventional continuous purification to get biodiesel.

[16] In an embodiment of the present invention the oil used is selected from palm olein, a refined vegetable oil.

[17] In another embodiment of the present invention the alcohol used may be selected from methanol, ethanol.

[18] In yet another embodiment of the present invention the catalyst used may be selected from sodium hydroxide, potassium hydroxide.

[19] In still another embodiment of the present invention, the known method of separation used are continuous separation and continuous purification.

[20] The process of the present invention is described below in brief.

[21] Palm olein having specific gravity in the range of 0.80 to 0.98 and iodine value from

50 to 98 is heated to a temperature not exceeding 75° C for not more than 15 minutes and is transesterified using 8 to 20% w/w, of alcohol of general formula R-OH, where R represents (C-H_2n+O, fl being any integer between 1 and 5, by known method in presence of not more than 1.5% w/w, of a known catalyst, at a temperature higher than the boiling point of the alcohol but not exceeding 75° C. for not more than 30 minutes under continuous stirring condition at rpm in the range of IOOOD to 5500 rpm to get a mixture of ester and glycerol.

[22] After the process [21] above is completed, the mixture of ester and glycerol is immediately fed by gravity to a custom design continuous mechanical separator.

[23] The inventive step of the present invention lies not only in selecting the temperature of transesterification at higher than the boiling point of the alcohol while not exceeding 75° C, but also in maintaining homogeneity monitored by sampling of the mixture every 5 minutes to ensure about 80% to 97% conversion of the oil into ester within a period of as low as 35 minutes, thereby enhancing the formation of fuel properties in the resulting product called palm biodiesel or methyl ester. Advantageous Effects

[24] No large area or site is needed to house the biodiesel continuous unit.

[25] No new steam boiler plant needed to supply heat.

[26] No new bulk storage tank needed to keep the feedstock refined vegatable oil.

[27] Low cost construction using mild steel instead of food grade stainless steel as the final product palm diesel is classified as bio-fuel.

[28] The low temperature with turbulent flow created by the bottom stirrer, reduces the reaction time significantly.

[29] The special provision in the reactor, separators and purifiers enable the effective recovery of excess alcohol added for the reaction.

[30] The product has a better oxidative stability compared to the product from conventional water washed process.

[31] The product is based on renewable source.

[32] The product can be used as substitute fuel for diesel engines without any major modification of engines.

[33] The products fuel properties and the engine efficiency are comparable with normal diesel engine fuels.

[34] The emission characteristics are like those of normal fuels. Description of Drawings

[35] Figure 1 is the biodiesel unit schematic process flow diagram attached to the vegetable oil refinery.

[36] Figure 2 is the gas chromatography analysis result of the palm biodiesel using EN14103:2003 test method.

[37] The following detail description is given by way of illustration only and therefore should not be construed to limit the scope and spirit of the present invention.

[38] This invention is characterized by the fact that the biodiesel unit is attached directly to the vegetable oil refinery by connecting pipeline (6) from the first reactor (9) to the refined oil bulk storage tank. Sodium methoxide is fed from methoxide tank (2) through a flow control valve (3). The mixture of about 20% sodium methoxide with about 80% palm olein passes through pump (4) into pipeline (6) being controlled by a flow control valve (5) to deliver the correct flow rate being fed into the first reactor (9). Another character of this invention is that waste refinery heat from the boilers and or thermal oil heaters used in the refinery flow through heat exchanger (7) to supply almost all or supplement the required heat energy in the biodiesel unit. The biodiesel unit thermal oil heater (8) is used to regulate the feed temperature and also use in the case of intermittent heat supply requirement or the unavailability of waste energy due to shutdown or maintenance of the refinery boilers and or thermal oil heaters. [39] It is also the object of the invention to demonstrate that the biodiesel unit is a waterless process by further describing the process flow of the transesterifϊcation process. The raw material enters the bottom of the first reactor (9) and agitated by a high speed agitator of about 2,800 rpm attached at the bottom of the reactor. The mixture is subjected to a turbulent flow due to the high speed agitation. As the mixture travels to the top of the reactor the flow becomes laminar. The mixture then flows into the next reactor (10) through pipe (57). Excess volatile methanol escapes through the top of the reactor via a pipe to the methanol header (54) and condenses in the ambient pressure condenser (53) into flash drum (46). The mixture goes through this process continuously and repeatedly until it reaches reactor (15) where reactor (15) is set to the highest temperature of about 75 Deg C among the reactor (9) to (14). Due to the repeated turbulent and laminar flow and the continuous removal of volatile methanol from each reactor it is believed to have push the reaction of transesterification forward to at least 97% conversion to methyl ester. The mixture of methyl ester, glycerol, spent catalyst and methanol then enters glycerol separator (37). While the mixture travels to the top of the separator, more and more of the impurities in the methyl ester settles to the bottom of the separator into the bottom glycerol phase. The glycerol is continuously removed by an automatic discharge valve located at the bottom of the separator which is connected to pipe (61) that leads to pump (45) and then to glycerol purifier (17). Any volatile methanol will continuously escapes to the top of the separator into a pipe to the methanol header (54). This process is repeated until the mixture reach the last separator (40) where the purity of methyl ester has been found to be improved. The product crude palm biodiesel then travels to methyl ester purifier (16) to remove any remaining methanol. Then the product travels to cooling tank (41) to undergo a sudden cooling shock with high agitation. This process is believed to dislodge any spent catalyst from the crude palm diesel. The cooling tank (41) and (42) is cooled down by using a chiller (55). The product then is further cooled in cooling tank (42) without agitation to allow for the spent catalyst to separate out from the biodiesel. Tank (43) is the holding tank of the crude biodiesel before it undergoes further separation and purification in the centrifugal purifier (44). Spent catalyst is separated out intermittently from the bottom part of the centrifugal purifier bowl, while the refined biodiesel emerges continuously from the top bowl of the centrifugal purifier into pipe (64) to biodiesel storage tank (65). [40] The analysis result of a sample taken from pipe (64) yield 99.7 % ester content. The test was conducted using Shimadzu Gas Chromatography GC-17A using the EN14103:2003 test method. The analysis result is enclosed in Figure 2. The biodiesel exceeds the EN 14214 biodiesel specifications and was used for running a test engine.

Claims

[ 1 ] An improved method and process for the commercial production of biodiesel or methyl ester as fuel or as oleo-chemical feedstock , which comprises;

(a) The manufacture of biodiesel or methyl ester from refined vegetable oil by attaching a specially designed low temperature and low pressure continuous biodiesel unit (Figure 1.) at a vegetable oil refinery by linking pipelines from the refined oil bulk storage tank (1) directly to the first transesterification reactor(9).

(b) Utilizing waste heat from the existing refinery boilers and or existing refinery thermal oil heaters by using heat exchanger (7) to supplement or totally supply the heating energy needed for the biodiesel unit which the temperature and the flow of the heating oil is controlled and regulated by the biodiesel unit thermal oil heater (8).

[2] A process, as claimed in claim 1 wherein the oil is selected from refined vegetable oil from the refinery bulk storage tank. [3] A process, as claimed in claim 1, wherein the heat needed is supplied by waste refinery heat either from the returning line of the existing refinery steam boilers and or the returning line of the existing refinery thermal oil heaters. [4] A process, as claimed in claim 1, wherein the heat needed is supplied by waste refinery heat either from the flue gas of the steam boilers and or the flue gas of the thermal oil heaters. [5] A process, as claimed in claim 1, wherein the method of separation is continuous using a special design separator (37), (38), (39) and (40). [6] A process, as claimed in claim 1 wherein the method of purification is continuous and absorbentless using the combination of cooling tank (41) and

(42) and holding tank (43) along with a centrifugal purifier (44) or a centrifugal decanter. [7] A process, as claimed in claim 1 wherein the purification of the methyl ester or better known as biodiesel is a waterless process.