CN1473907A

CN1473907A - Process for producing biological diesel oil

Info

Publication number: CN1473907A
Application number: CNA021335915A
Authority: CN
Inventors: 俞建秋; 陈德裕; 李俊雄; 陈自端
Original assignee: GUSHAN OIL CHEMISTRY CO Ltd SICHUAN
Current assignee: GUSHAN OIL CHEMISTRY CO Ltd SICHUAN
Priority date: 2002-08-07
Filing date: 2002-08-07
Publication date: 2004-02-11
Anticipated expiration: 2022-08-07
Also published as: CN1197937C

Abstract

The present invention relates to one technology of recovering fatty acid from waste. The leftover produced in the vegetable oil refining process and the recovered edible oil as material is processed through eliminating impurity, continuous dewatering, esterification, recovering methanol, letting stand to stratify, recovering glycerine, and continuous distillation to obtain biological diesel oil product. The said process is simple and reliable, may be completed in 6 hr, has acid value lowered to below 1 mg KOH/g, fatty acid converting rate as high as 93 %, high yield, low methanol consumption and low production cost, and is suitable for industrial production.

Description

Method for producing biodiesel

The technical field is as follows: the invention relates to a technology for recovering fatty acid from waste materials, in particular to a method for producing biodiesel used for diesel machinery power fuel by using byproducts, namely oil residue, soapstock, acidified oil or other animal oil and fat and edible recovered oil, generated in the refining process of vegetable oil as raw materials.

(II) background technology: with the annual reduction of the storage amount of mineral diesel, all countries are seeking renewable biological energy sources, and as fatty acid methyl ester is closest to the mineral diesel in the aspects of combustion performance, characteristics and thelike, and some indexes exceed the mineral diesel, developed countries such as Europe and America and the like develop the production of the biological diesel by using vegetable oil as a raw material.

Biodiesel was successfully developed in Germany in 1988, biodiesel was produced by rapeseed oil, and was formally put on the market in 1989, and three years of practical demonstration proves that various performances of B30 biodiesel (30% biodiesel and 70% petrochemical diesel) machines are well exerted, the emission of harmful gases is greatly reduced under the condition of no reduction of power, and the biodiesel is popularized and applied in German legislation in 1991.

In the United states, the soybean oil is used for producing the biodiesel on a small scale in 1990, and the biodiesel is listed as clean fuel by the national energy agency and is popularized and applied, wherein the current mixing ratio is 20 percent of the biodiesel to 80 percent of the petrochemical diesel, and the biodiesel is B20 for short.

China also has worked on this aspect, for example, Chinese patent application 92114795.3, which is to produce biodiesel from natural oil and fat, and cannot be widely used due to high price of raw materials; chinese patent application CN1151433A discloses a method for synthesizing mixed fatty acid by using cotton oil nigre as raw material, but the industrial production can not be realized because the production technology is immature, the product quality is poor and the energy consumption is high.

(III) the invention content: the invention aims to provide a method for producing biodiesel by using organic oil leftovers as raw materials, which can reduce the production cost, is suitable for large-scale industrial production and can reduce environmental pollution aiming at the defects of the prior technical scheme.

The technical content of the invention is divided into two parts:

1. a pretreatment stage: removing mechanical impurities, putting the mixture into a raw material storage tank, heating the mixture, and dehydrating the mixture in a dehydrator with the vacuum degree of-0.08 MPa to-0.095 MPa and the temperature of 60 ℃ to 130 ℃ for later use.

2. An esterification stage: pumping the pretreated raw materials into a reactor, adding other ingredients, and heating to 60-80 ℃. The water produced in the reaction and the ingredient methanol enter a recovery tower in a gas phase, the water is separated out, and the pure methanol returns to the reactor to continue the reaction. When the reaction is completed, the catalyst is removed, and the excess methanol which has not reacted is purified and recovered from the methanol recovery column.

The generated material enters a precipitation tank, a small amount of water is removed, the material enters a distillation tower, continuous distillation is carried out under reduced pressure, a distillate is cooled to obtain a finished product, and the finished product is pumped to a finished product storage tank.

The raw materials used in the invention can be soapstock, oil residue and acidified oil (leftovers for short) generated in the refining process of vegetable oil such as rape oil, soybean oil, cottonseed oil and the like, can also be edible recovered oil, and can also be a mixture of the soapstock, the oil residue and the acidified oil.

The catalyst used in the invention is the compound of inorganic acid and organic acid; the inorganic acid is as follows: sulfuric acid, hydrochloric acid, phosphoric acid; the organic acid is p-toluenesulfonic acid, dodecylbenzene sulfonic acid, naphthalene sulfonic acid or homologues thereof.

The invention utilizes fatty substances in animal and vegetable oil leftovers to react with methanol under the action of a catalyst to generate fatty acid methyl ester, and the reaction formula is as follows:

(R：C₁₃-C₂₁)

in addition, there is a reaction of a small amount of mono-and diglycerides with methanol, which is different from fatty acid methyl esters to produce fatty acid methyl esters in the presence of an acidic catalyst; and is also different from the preparation of fatty acid methyl ester by grease and methanol in the presence of a basic catalyst. The difficulty is greater than both of the former.

The reaction is a reversible reaction, whether water generated in the reaction process can be removed in time or not is the key for improving the conversion rate of methyl ester, because the traditional method is to react in an enamel kettle, the water generated cannot be discharged in time, and the reaction reaches a certain degree, the reaction is carried out to a certain extentThe reaction can not be carried out in the positive reaction direction, so the reaction is incomplete and the conversion rate is not high; the invention adopts the structure that the esterification reactor and the methanol recovery tower are connected into a whole, and can remove water generated in the reaction process at any time. The reaction is developed towards the positive reaction direction all the time, so the reaction is thorough, the ester conversion rate is high and can reach more than 93 percent; and the reactor can be made to be 20m³The method is particularly suitable for industrial mass production. Also, by adopting this structure, the excess methanol which does not participate in the reactioncan be recovered and purified, so that the methanol content is highThe consumption is greatly reduced.

The invention adopts continuous vacuum dehydration, the dehydrator adopts a specially designed plate structure or a packing structure, and the vacuum forming equipment is a water ring pump or a hydraulic jet vacuum pump.

Because the composite catalyst system is adopted, the fatty acid can be converted into methyl ester, and the neutral oil can be alcoholyzed into the methyl ester, so that the product yield is high; because the esterification reaction is a reversible process, after the esterification meets the requirement, the catalyst must be removed first, and then the methanol is recovered, otherwise, the acid value will be slightly increased.

The invention is characterized in that the distillation of the crude methyl ester adopts continuous distillation after decompression. The crude methyl ester is preheated to about 230 ℃ by a rising film type pre-filter and then enters an evaporation tower, the evaporation tower adopts a falling film type heat exchanger for heating to prevent the material from being excessively heated and deteriorating, the vacuum reaches 1-6mmHg, and the equipment is a steam jet vacuum pump or a steam pump and a water ring pump which are connected in series. After the product is evaporated, the product is cooled to below 35 ℃ to ensure good color and luster of the product.

The main quality indexes of the biodiesel produced by the method are as follows:

serial number	Index name	Unit of	Index value
			Index value	Special class
			1	Special class	Color intensity	Number (C)	≤1
2	Sulfur content	％(m/m)	1	≤0.05	Color intensity	Number (C)	≤1
2	Sulfur content	％(m/m)	3	≤0.05	Acid value	mgKOH/10	≤45
4	Ash content	％(m/m)	3	≤0.005	Acid value	mgKOH/10	≤45
4	Ash content	％(m/m)	5	≤0.005	Freezing point	℃	≤-5
6	Cold filter plugging point	℃	5	≤-1	Freezing point	℃	≤-5
6	Cold filter plugging point	℃	7	≤-1	Flash point (closed)	℃	≥70
8	10% of carbon residue of distillation residue	％(m/m)	7	≤0.5	Flash point (closed)	℃	≥70
8	10% of carbon residue of distillation residue	％(m/m)	9	≤0.5	Corrosion of copper sheet	Stage	≤1
10	Moisture content	％(m/m)	9	Trace of	Corrosion of copper sheet	Stage	≤1
10	Moisture content	％(m/m)	11	Trace of	Mechanical impurities		Is free of
12	Kinematic viscosity (20)	mm²/s	11	3.0～8.0	Mechanical impurities		Is free of
12	Kinematic viscosity (20)	mm²/s	13	3.0～8.0	Cetane number		≥46

The process of thepresent invention has high biodiesel oil quality, simple and reliable process, low consumption, high yield and low cost, and is suitable for industrial production.

Claims

1. A method for producing biodiesel, comprising the steps of:

A. continuously vacuum dehydrating the raw material to reduce the water content to below two thousandth;

B. the dehydrated raw materials are mixed with methanol in a ratio of 1: 0.15-0.35 and a catalyst in a ratio of 1-3% (all weight ratios), the mixture is put into an esterification reactor, forced circulation is carried out by a pump, heating and mixing are enhanced, and the reaction temperature is controlled at 60-80 ℃; the newly generated water is continuously removed from the bottom of the methanol recovery tower, and the pure methanol at the top of the tower returns to the esterification reactor to participate in the reaction; after the reaction is finished, firstly removing the catalyst, and then recovering and purifying excessive methanol in the system; the material which has been recovered with methanol enters a precipitation tank to remove a small amount of water, and then enters a distillation tower for continuous reduced pressure distillation to separate the biodiesel.

2. The method for producing biodiesel according to claim 1, wherein the raw material thereof may be leftovers produced in the refining process of vegetable oil, or edible recovered oil; mixtures thereof are also possible.

3. The method for producing biodiesel according to claim 1 or 2, wherein the dehydration process comprises continuous vacuum dehydration at a vacuum degree of-0.08 to-0.095 MPa and a temperature of 60 to 95 ℃ to control the water content of the raw material to be less than 0.2%.

4. The method for producing biodiesel according to claim 1 or 2, wherein the crude methyl ester is distilled by continuous distillation under reduced pressure, and the absolute distillation pressure is 1-6 mmHg.

5. The method for producing biodiesel according to claim 3, wherein said crude methyl ester is distilled by continuous distillation under reduced pressure, and the absolute distillation pressure is 1-6 mmHg.

6. The method for producing biodiesel according to claim 1 or 2, wherein the catalyst is a combination of an inorganic acid and an organic acid; the inorganic acid is as follows: sulfuric acid, hydrochloric acid, phosphoric acid; the organic acid is p-toluenesulfonic acid, dodecylbenzene sulfonic acid, naphthalene sulfonic acid or homologues thereof.

7. The method for producing biodiesel according to claim 3, wherein the catalyst is a combination of an inorganic acid and an organic acid; the inorganic acid is as follows: sulfuric acid, hydrochloric acid, phosphoric acid; the organic acid is p-toluenesulfonic acid, dodecylbenzene sulfonic acid, naphthalene sulfonic acid or homologues thereof.

8. The method for producing biodiesel according to claim 4, wherein the catalyst is a combination of an inorganic acid and an organic acid; the inorganic acid is as follows: sulfuric acid, hydrochloric acid, phosphoric acid; the organic acid is p-toluenesulfonic acid, dodecylbenzene sulfonic acid, naphthalene sulfonic acid or homologues thereof.

9. The method for producing biodiesel according to claim 5, wherein the catalyst is a combination of an inorganic acid and an organic acid; the inorganic acid is as follows: sulfuric acid, hydrochloric acid, phosphoric acid; the organic acid is p-toluenesulfonic acid, dodecylbenzene sulfonic acid, naphthalene sulfonic acid or homologues thereof.