CN105194895B - A kind of method that biodiesel is prepared using thermal coupling next door reactive distillation column - Google Patents

Abstract

The invention discloses a production method for preparing biodiesel in a thermally coupled partition wall reaction rectification tower. The thermally coupled dividing wall reactive distillation column includes a condenser, a reboiler and a main tower with a dividing wall; the main tower includes a reaction separation area, a production area and a tower bottom area; the preparation method of the high-purity biodiesel Including raw material oil and alcohol enter the reaction separation area after preheating to contact with the catalyst for reaction pre-separation, the by-product water is extracted from the top of the reaction separation area, and the target product high-purity biodiesel component is extracted from the bottom area to provide raw material pre-separation Energy is required for heat, and the unreacted component raw material alcohol is extracted through the top of the extraction area. The method of the present invention integrates the reaction and the separation of the three substances into one tower, and the effect of two rectification towers is realized by one rectification tower. Compared with the conventional process, the thermally coupled partition reaction rectification tower has the advantages of saving equipment The effect of investing and reducing energy consumption to produce high-purity biodiesel.

Description

A method for preparing biodiesel using a thermally coupled dividing wall reactive distillation column

technical field

The invention relates to the field of biochemical technology, in particular to a method for preparing biodiesel by using a thermally coupled partition wall reaction distillation tower.

Background technique

Biodiesel Fuel is a long-chain monoalkyl ester made from vegetable oil or animal fat, which can replace petrochemical diesel for regenerative diesel fuel in compression ignition engines. Compared with traditional petrochemical energy , with low sulfur and aromatic content, high flash point, high cetane number, good lubricity, and can be partially added to petrochemical diesel.

In recent years, with the depletion of fossil energy and the sharp increase in human demand for fuel energy, the biodiesel industry has received extensive attention. Whether it can improve the net energy gain, whether it has environmental benefits and economic competitiveness, and whether it can be produced in large quantities without reducing food supply is the prerequisite for the industrial application of biodiesel. In the process of biodiesel production, catalysts play a key role, commonly used are alkaline catalysts, acid catalysts, enzyme catalysts and inorganic catalysts.

Bioenzyme production of biodiesel has the advantages of mild reaction conditions, low energy consumption, and low equipment requirements. Patent CN1436834A provides a method for synthesizing bio-oil from short-chain fatty acid esters, using bio-enzymes to catalyze animal and vegetable oils and other renewable resources to produce bio-diesel at a suitable temperature. However, the production cost of bio-enzyme method is high, the reaction efficiency is low, and the catalytic enzyme is easily inactivated, which hinders the application of bio-enzyme technology in industrial production, and its research is currently in the exploratory stage.

Compared with enzymatic biodiesel synthesis, chemical biodiesel production has the advantages of lower production cost, easy reaction control, and high oil conversion rate, which is of great significance for improving production efficiency and reducing production cost. Patent CN103756791A uses waste oil to produce biodiesel under the action of composite catalyst, the oil conversion rate is high, and the catalyst can be recycled. Patent CN 103756792A removes most of the free fatty acids in oils and fats through pretreatment and effectively reduces water content, and effectively removes soap, glycerin, and some colored impurities in biodiesel through activated clay treatment in transesterification, and adds stabilizers in post-treatment, Increased biodiesel stability.

Although the chemical method can increase the conversion rate of bio-oil and reduce the production cost, its high energy consumption load has become one of the problems faced by the wide application of this method in industry. Experts and scholars at home and abroad have made outstanding contributions to reducing device energy consumption and operating costs. Patent CN 103320233A proposes a method for producing biodiesel using a continuous tubular reactor. This method does not require heating or stirring during the esterification reaction process, and is highly efficient and energy-saving. The entire process is carried out under low temperature and normal pressure, with low energy consumption and high utilization rate High, energy saving and environmental protection; Patent US 2008312460A1 has developed an ultrasonic device that uses multi-frequency ultrasonic energy to convert vegetable oil or animal oil into biodiesel, saving energy consumption.

Contents of the invention

In order to reduce the problem of high energy consumption in the process of producing biodiesel by chemical method, the present invention proposes a method for preparing high-purity biodiesel by using a thermally coupled bulkhead reaction distillation column to produce biodiesel to reduce equipment investment and energy consumption.

The object of the present invention is to provide a process and device for producing high-purity biodiesel. The present invention simplifies the traditional two-tower process into a single-tower process by utilizing thermally coupled next-wall reactive distillation towers, reduces equipment investment, and reduces energy consumption for biodiesel production by using thermal coupling in the towers, and then uses the high-temperature products at the bottom of the towers for Due to the preheating of raw materials, the energy utilization efficiency is greatly improved.

The present invention adopts following technical scheme:

The thermally coupled partition wall reactive distillation column used for preparing biodiesel in the present invention comprises a main tower with a partition wall, a tower top water condenser, a tower top alcohol condenser and a tower bottom reboiler; the inside of the main tower is divided into a reaction separation area, Extraction area and tower bottom area, the tower bottom area is located in the lower part of the rectification tower, the reaction separation area and the extraction area are located in the middle and upper part of the rectification tower, the two are separated by a vertical partition, and the upper part of the vertical partition It is connected to the top of the distillation column, and the lower end is suspended above the bottom area of the column.

The outside of the rectification tower in the reaction separation area is connected with a raw material oil feed pipe and a raw material alcohol feed pipe. The two pipes are respectively equipped with a raw material oil preheater and a raw material alcohol preheater; The top of the separation area; the top alcohol condenser is connected to the top of the production area through pipelines; the bottom of the rectification tower is provided with a discharge pipe, which is divided into two, and one is connected to the reboiler at the bottom of the tower. It is connected to the rectification tower body in the production area, and the other is connected to the raw material oil preheater and the raw material alcohol preheater in turn.

The reaction separation area is filled with a reaction catalyst to play the role of reactive rectification, and the production area and the tower bottom area are filled with high-efficiency structured packing or trays to play the role of rectification and separation.

Utilize the method for preparing biodiesel with thermally coupled bulkhead reactive distillation column of the present invention:

After preheating, the raw material oil and alcohol enter the reaction separation area to contact with the catalyst for reaction pre-separation, the by-product water flows out from the top of the reaction separation area, and the target product high-purity biodiesel component flows out from the bottom area to provide the raw material preheating Energy, unreacted component Methanol is extracted via the top of the extraction zone.

The raw material oil is free fatty acid.

The raw material alcohol is monohydric alcohol, preferably methanol.

The catalyst is a solid-phase acid catalyst.

The operating pressure of the thermally coupled dividing wall reaction distillation column is 100-1000kPa, the operating temperature of the top of the reaction zone is 117-152°C, the operating temperature of the reaction separation area (I) is 102-145°C, and the operating temperature of the bottom area (Ⅲ) is 120 ~350°C.

Specific steps are as follows:

After preheating, the raw material alcohol enters the thermally coupled next-wall reactive distillation column from the lower part of the reaction separation area, and the raw material oil enters the thermally coupled next-wall reactive distillation column from the upper part of the reaction separation area after preheating. The two raw materials are produced under the action of a solid acid catalyst The esterification reaction produces the target product biodiesel and by-product water. The reaction by-product water is separated in the reaction separation area of the thermally coupled next-wall reactive distillation column, and high-purity water is obtained at the top of the tower. Part of it is extracted after being condensed by the top condenser, and the other part is returned to the tower as top reflux. The high-boiling point component biodiesel is separated in the bottom area of the thermally coupled dividing wall reaction distillation column, and high-purity biodiesel is obtained at the bottom of the tower. The biodiesel whose temperature is lowered after heat exchange in the feed preheater is extracted as a product, and the other part is returned to the tower as the rising steam at the bottom of the tower. The unreacted methanol component is separated in the extraction area of the thermally coupled next-wall reactive distillation column, and high-purity methanol is obtained at the top of the column, part of which is extracted after being condensed by the overhead alcohol condenser, and the other part is returned to the column as column top reflux Inside.

Compared with the prior art, the effect of the present invention is:

The production of high-purity biodiesel is realized in the thermally coupled dividing wall reactive distillation column, and the traditional reactive distillation and subsequent separation and purification processes are integrated into a thermally coupled dividing wall reactive distillation column, which saves equipment investment and reduces energy consumption. The heat-coupled dividing wall reaction distillation column process realizes closed-circuit circulation, and the incompletely reacted raw materials are refluxed and reused, which improves the total conversion rate.

In the present invention, the reaction catalyst is filled on the feed side of the dividing wall rectifying tower, so that the reaction is carried out in the pre-separation section, that is, the thermally coupled dividing wall reactive rectifying tower is formed. Through this process, the conversion rate of raw material oil is above 99%, and the purity of biodiesel obtained is above 99.5%, which meets the same hydrolysis rate and product separation requirements, and can save energy by more than 30% compared with conventional reactive distillation processes.

Description of drawings

Fig. 1 is the technological flow diagram of producing high-purity biodiesel with thermally coupled bulkhead reactive distillation column;

Explanation of reference signs:

E1 tower top water condenser; E2 tower bottom reboiler; E3 tower top alcohol condenser; E4 raw material oil preheater; E5 raw material alcohol preheater; 2 preheated raw material oil; 3 raw material alcohol; 4 preheated raw material alcohol; 5 top water vapor in the reaction separation zone; 6 top methanol vapor in the production area; 7 condensed water; 8 condensed methanol; 9 Top reflux in the reaction separation zone; 10 Top reflux in the production area; 11 Part of biodiesel returned to the tower; 12 Biodiesel steam returned to the tower; 13 Part of biodiesel produced; 14 Biodiesel product after heat exchange with raw material alcohol; 15 Biodiesel product after heat exchange with raw oil; Ⅰ reaction separation area; Ⅱ production area; Ⅲ tower bottom area.

detailed description

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

As shown in Figure 1: the thermally coupled dividing wall reactive distillation column for preparing biodiesel of the present invention comprises main tower RDWC, tower top water condenser E1 with dividing wall, tower top alcohol condenser E3 and tower bottom reboiler E2; The inside of the main tower is divided into reaction separation area Ⅰ, production area Ⅱ and tower bottom area Ⅲ, the tower bottom area Ⅲ is located in the lower part of the rectification tower, and the reaction separation area Ⅰ and production area Ⅱ are located in the middle and upper part of the rectification tower. The latter are separated by a vertical partition, the upper end of the vertical partition is connected to the top of the rectification column, and the lower end is suspended above the bottom area III.

The rectification tower in the reaction separation zone I is connected with feed pipes for feed oil and feed pipes for feed alcohol, and the two pipes are respectively equipped with feed oil preheater E4 and feed alcohol preheater E5; tower top water condenser E1 The tower top of the reaction separation area I is connected by a pipe; the top alcohol condenser E3 is connected to the tower top of the production area II by a pipe; the bottom of the rectification tower is provided with a discharge pipe, and the discharge pipe is divided into two, one It is connected to the bottom reboiler E2 and then connected to the rectification tower body in the production area II, and the other one is connected to the raw material oil preheater E4 and the raw material alcohol preheater E5 in turn.

The reaction separation zone I is filled with a reaction catalyst to play the role of reactive rectification, and the extraction zone II and tower bottom zone III are filled with high-efficiency structured packing or trays to play the role of rectification and separation.

The thermally coupled partition wall reactive distillation process used in the present invention is that the raw material alcohol enters the thermally coupled partition wall reactive distillation column RDWC from the lower part of the reaction separation area after being preheated, and the raw material oil enters the thermally coupled partition wall from the upper part of the reaction separation area I after preheating In the reactive distillation column RDWC, the two raw materials undergo an esterification reaction under the action of a solid acid catalyst to produce the target product biodiesel and by-product water. In the reaction separation zone Ⅰ of the thermally coupled dividing wall reaction distillation column RDWC, the reaction by-product water is separated, and high-purity water is obtained at the top of the tower. After being condensed by the top condenser E1, part of it is extracted, and the other part is returned to the tower as top reflux. Inside. The high boiling point component biodiesel is separated in the bottom area of the thermally coupled dividing wall reactive distillation column (RDWC), and high-purity biodiesel is obtained at the bottom of the column, and part of it is used as a heat source for feed preheating by feed preheater E4 After heat exchange with E5, the biodiesel whose temperature is lowered is extracted as a product, and the other part is returned to the tower as the bottom reflux ascending steam after heat exchange with the bottom reboiler E2. The unreacted component methanol is separated in the extraction area II of the thermally coupled dividing wall reactive distillation column RDWC, and high-purity methanol is obtained at the top of the tower, and part of it is extracted after being condensed by the top condenser E3, and the other part is used as the top reflux Return to the tower.

In order to better illustrate the production effect of the present invention, three examples are selected for illustration, and these examples are only for the purpose of illustration, and are not intended to limit the scope of the present invention.

Example 1:

The thermally coupled partition wall reactive distillation process used in the present invention is that the raw material alcohol enters the thermally coupled partition wall reactive distillation column RDWC from the lower part of the reaction separation area after being preheated, and the raw material oil enters the thermally coupled partition wall from the upper part of the reaction separation area I after preheating In the reactive distillation column RDWC, the two raw materials undergo an esterification reaction under the action of a solid acid catalyst to produce the target product biodiesel and by-product water. In the reaction separation zone Ⅰ of the thermally coupled dividing wall reaction distillation column RDWC, the reaction by-product water is separated, and high-purity water is obtained at the top of the tower. After being condensed by the top condenser E1, part of it is extracted, and the other part is returned to the tower as top reflux. Inside. The high boiling point component biodiesel is separated in the bottom area of the thermally coupled dividing wall reactive distillation column (RDWC), and high-purity biodiesel is obtained at the bottom of the column, and part of it is used as a heat source for feed preheating by feed preheater E4 After heat exchange with E5, the biodiesel whose temperature is lowered is extracted as a product, and the other part is returned to the tower as the bottom reflux ascending steam after heat exchange with the bottom reboiler E2. The unreacted component methanol is separated in the extraction area II of the thermally coupled dividing wall reactive distillation column RDWC, and high-purity methanol is obtained at the top of the tower, and part of it is extracted after being condensed by the top condenser E3, and the other part is used as the top reflux Return to the tower.

The process is shown in Figure 1. The actual number of plates in each area is shown in Table 1, and the feed flow rate and composition are shown in Table 2. The feeding positions of raw oil and alcohol (counting from top to bottom) are the third and 22nd theoretical plates of thermally coupled dividing wall reactive distillation column RDWC respectively, and the feeding temperature is 100°C. The operating pressure of the thermally coupled dividing wall reaction distillation column RDWC is 350kPa, the output at the top of the reaction separation area is 100kmol/h, the temperature at the top is 138°C, and the temperature at the bottom is 107°C; the output at the top of the output area is 100kmol/h , the top temperature is 99°C, the bottom temperature is 104°C; the flow rate in the bottom area of the tower is 100kmol/h, the top temperature is 107°C, and the bottom temperature is 339°C. The flow rate and composition of each stream are shown in Table 2, and the purity of the obtained biodiesel is 99.99%.

Table 1 The actual number of boards in each area

tower section Reactive distillation area mining area Bottom area Actual number of boards twenty four twenty four 6

Table 2 Example 1 Each logistics mass flow rate and each component mass fraction

Example 2:

The thermally coupled partition wall reactive distillation process used in the present invention is that the raw material alcohol enters the thermally coupled partition wall reactive distillation column RDWC from the lower part of the reaction separation area after being preheated, and the raw material oil enters the thermally coupled partition wall from the upper part of the reaction separation area I after preheating In the reactive distillation column RDWC, the two raw materials undergo an esterification reaction under the action of a solid acid catalyst to produce the target product biodiesel and by-product water. In the reaction separation zone Ⅰ of the thermally coupled dividing wall reaction distillation column RDWC, the reaction by-product water is separated, and high-purity water is obtained at the top of the tower. After being condensed by the top condenser E1, part of it is extracted, and the other part is returned to the tower as top reflux. Inside. The high boiling point component biodiesel is separated in the bottom area of the thermally coupled dividing wall reactive distillation column (RDWC), and high-purity biodiesel is obtained at the bottom of the column, and part of it is used as a heat source for feed preheating by feed preheater E4 After heat exchange with E5, the biodiesel whose temperature is lowered is extracted as a product, and the other part is returned to the tower as the bottom reflux ascending steam after heat exchange with the bottom reboiler E2. The unreacted component methanol is separated in the extraction area II of the thermally coupled dividing wall reactive distillation column RDWC, and high-purity methanol is obtained at the top of the tower, and part of it is extracted after being condensed by the top condenser E3, and the other part is used as the top reflux Return to the tower.

The process is shown in Figure 1. The actual number of plates in each area is shown in Table 3, and the feed flow rate and composition are shown in Table 4. The feeding positions of raw oil and alcohol (counting from top to bottom) are the third and 22nd theoretical plates of thermally coupled dividing wall reactive distillation column RDWC respectively, and the feeding temperature is 100°C. The operating pressure of the thermally coupled dividing wall reaction distillation column RDWC is 350kPa, the output at the top of the reaction separation area is 80kmol/h, the temperature at the top is 139°C, and the temperature at the bottom is 107°C; the output at the top of the output area is 80kmol/h , the top temperature is 100°C, the bottom temperature is 105°C; the flow rate in the bottom area of the tower is 80kmol/h, the top temperature is 107°C, and the bottom temperature is 339°C. The flow rate and composition of each stream are shown in Table 2, and the purity of the obtained biodiesel is 99.99%.

Table 3 The actual number of boards in each area

tower section Reactive distillation area mining area Bottom area Actual number of boards twenty four twenty four 6

Table 4 Example 1 Each logistics mass flow rate and each component mass fraction

Example 3:

The thermally coupled partition wall reactive distillation process used in the present invention is that the raw material alcohol enters the thermally coupled partition wall reactive distillation column RDWC from the lower part of the reaction separation area after being preheated, and the raw material oil enters the thermally coupled partition wall from the upper part of the reaction separation area I after preheating In the reactive distillation column RDWC, the two raw materials undergo an esterification reaction under the action of a solid acid catalyst to produce the target product biodiesel and by-product water. In the reaction separation zone Ⅰ of the thermally coupled dividing wall reaction distillation column RDWC, the reaction by-product water is separated, and high-purity water is obtained at the top of the tower. After being condensed by the top condenser E1, part of it is extracted, and the other part is returned to the tower as top reflux. Inside. The high boiling point component biodiesel is separated in the bottom area of the thermally coupled dividing wall reactive distillation column (RDWC), and high-purity biodiesel is obtained at the bottom of the column, and part of it is used as a heat source for feed preheating by feed preheater E4 After heat exchange with E5, the biodiesel whose temperature is lowered is extracted as a product, and the other part is returned to the tower as the bottom reflux ascending steam after heat exchange with the bottom reboiler E2. The unreacted component methanol is separated in the extraction area II of the thermally coupled dividing wall reactive distillation column RDWC, and high-purity methanol is obtained at the top of the tower, and part of it is extracted after being condensed by the top condenser E3, and the other part is used as the top reflux Return to the tower.

The process is shown in Figure 1. The actual number of plates in each area is shown in Table 5, and the feed flow rate and composition are shown in Table 6. The feeding positions of raw oil and alcohol (counting from top to bottom) are the third and 22nd theoretical plates of thermally coupled dividing wall reactive distillation column RDWC respectively, and the feeding temperature is 100°C. The operating pressure of the thermally coupled dividing wall reaction distillation column RDWC is 350kPa, the output at the top of the reaction separation area is 90kmol/h, the temperature at the top is 139°C, and the temperature at the bottom is 107°C; the output at the top of the output area is 90kmol/h , the top temperature is 99°C, the bottom temperature is 105°C; the flow rate in the bottom area of the tower is 90kmol/h, the top temperature is 106°C, and the bottom temperature is 339°C. The flow rate and composition of each stream are shown in Table 2, and the purity of the obtained biodiesel is 99.99%.

Table 5 The actual number of boards in each area

tower section Reactive distillation area mining area Bottom area Actual number of boards twenty four twenty four 6

Table 6 Example 1 Each logistics mass flow rate and each component mass fraction

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (6)

1. A kind of 1. method that biodiesel is prepared using thermal coupling next door reactive distillation column, it is characterised in that：Described rectifying column Including the king-tower (RDWC) with partition wall, tower top water condenser (E1), tower top alcohol condenser (E3) and tower bottom reboiler (E2)； It is divided into Reaction Separation region (I) inside king-tower, produces region (II) and bottom of towe region (III), bottom of towe region (III) is located at rectifying column Bottom, Reaction Separation region (I) and extraction region (II) are located at the middle and upper part of rectifying column, and both are separated by vertical dividing plate Come, vertical clapboard upper end is connected with rectifying column tower top, and lower end is hanging above bottom of towe region (III)；

   Feedstock oil feed pipe and raw alcohol feed pipe are connected with outside the rectifying column of the Reaction Separation region (I), on two pipelines It is respectively equipped with fuel oil preheating device (E4) and raw alcohol preheater (E5)；Tower top water condenser (E1) passes through pipeline coupled reaction point From the tower top of region (I)；Tower top alcohol condenser (E3) connects the tower top of extraction region (II) by pipeline；The bottom of towe of rectifying column is set There is discharge nozzle, discharge nozzle is divided into two, and a connection tower bottom reboiler (E2) reconnects the rectifying tower body of extraction region (II), separately One is sequentially connected fuel oil preheating device (E4) and raw alcohol preheater (E5)；

   The Reaction Separation region (I) fills catalysts, plays reactive distillation effect, produces region (II) and bottom of towe region (III) High Efficient Standard Packing or column plate are filled, plays rectifying centrifugation；

   The method that described thermal coupling next door reactive distillation column prepares biodiesel, it is comprised the following steps that：

   Feedstock oil and alcohol contact after preheating into Reaction Separation region (I) with catalyst carries out reaction pre-separation, accessory substance By being flowed out at the top of Reaction Separation region (I), target product high-purity biodiesel component is flowed out and carried by bottom of towe region (III) water For energy needed for raw material preheating, unreacted component methanol is via extraction at the top of extraction region (II).
2. 2. preparation method as claimed in claim 1, it is characterised in that：Described feedstock oil is free fatty.
3. 3. preparation method as claimed in claim 1, it is characterised in that：Described raw alcohol is monohydric alcohol.
4. 4. preparation method as claimed in claim 3, it is characterised in that：Described raw alcohol is methanol.
5. 5. preparation method as claimed in claim 1, it is characterised in that：Described catalyst is solid phase acid catalyst.
6. 6. preparation method as claimed in claim 1, it is characterised in that：Thermal coupling next door reactive distillation column operating pressure is 100 ~1000kPa, reaction zone tower top operation temperature are 117~152 DEG C, and Reaction Separation region (I) operation temperature is 102~145 DEG C, Bottom of towe region (III) operation temperature is 120~350 DEG C.