KR20080089961A - Process for producing anhydrous ethanol by using extractive distillation - Google Patents

Abstract

A method for producing anhydrous ethanol is provided to increase the separation effect of ethanol and water and to reduce the using amount of an extracting agent. A method for producing anhydrous ethanol comprises the steps of separating diluted ethanol fermentation liquor to supply it to a low temperature concentration tower(100) and a high temperature concentration tower(200); distilled the supplied liquor, respectively, to product a concentrated ethanol steam of the each concentration tower upper part and a fluid product of the lower part; condensing the concentrated ethanol steam of the upper part of the low pressure concentration tower; partially condensing the concentrated ethanol steam of the upper part of the high pressure concentration tower by the heat exchange with the lower pressure concentration tower and compressing the uncondensed steam; extraction distilling the condensed and compressed concentrated ethanol to product anhydrous ethanol at the upper part of an extraction tower(300) and the fluid product of a lower part; distilling the fluid product of the lower part of the extraction tower at a recovery tower(400) to recover an extracting agent and refluxing the recovered extracting agent to the extraction tower; and condensing the anhydrous ethanol to produce anhydrous ethanol.

Description

Process for producing anhydrous ethanol by using extractive distillation

1 is an anhydrous ethanol production process according to an embodiment of the present invention

<Explanation of symbols for main parts of the drawings>

100: low pressure concentration column 110: heat exchanger

120: reboiler 130: condenser

140: heat exchanger

200: high pressure concentration tower 210: heat exchanger

220: compressor 230: fluid separator

240: Rework 250: Rework

300: extraction tower 310: reboiling

400: recovery tower 410: recycling

420: Compressor

The present invention relates to a method for producing anhydrous ethanol using extractive distillation, and more particularly, using a thermally integrated extractive distillation process, the process operation is continuous and stable, saves energy efficiently, reduces the circulation of the extractant and extracts The present invention relates to a method for producing anhydrous ethanol using extractive distillation that drastically reduced the required stage of the tower and increased operating efficiency.

In recent years, with the era of high oil prices, there is a problem that the natural system is damaged by fuels, and the development of alternative fuels has been made at various angles. One of the most popular alternative fuels is bioethanol obtained through fermentation of grain or biomass. Such bioethanol should be substantially anhydrous ethanol with a molar weight of ethanol of at least 99 mol%.

Conventional methods for producing anhydrous ethanol from fermented liquor or synthetic ethanol were typical separation techniques using azeotropic distillation and separation techniques using molecular sieves. However, the azeotropic distillation process using chemical additives such as benzene or cyclohexane had environmental problems and process operation problems. Therefore, a separation process using a molecular sieve which produces anhydrous ethanol from ethanol near azeotrope with little energy using mainly adsorption / desorption phenomenon due to pressure difference without using chemical additives has been mainly used recently. However, the separation process using molecular sieve is a discontinuous process that repeatedly performs adsorption and desorption by using two or more adsorption / desorption towers, and periodic replacement is necessary because physical grinding of molecular sieve occurs through continuous operation. In addition, it is also necessary to concentrate the ethanol as much as possible in the concentration tower has a disadvantage of smooth operation.

The present invention has been proposed to solve the problems of the conventional anhydrous ethanol production method as described above, using an extractive distillation environment-friendly and continuous process is possible, and thermal integration and extractive distillation of a new method that dramatically reduced energy consumption The purpose is to provide an anhydrous ethanol production method.

In addition, the present invention condenses the steam generated in the upper part of the recovery tower and efficiently utilizes condensation energy, and lowers the water content ratio of the extractant recovered in the recovery tower, thereby increasing the content ratio of ethanol produced from the extraction tower. The purpose is to.

In addition, the present invention has a purpose to achieve a stable process operation without excessively increasing the operating pressure of each tower by compressing the steam of the upper part of the tower by using a compressor.

In addition, the present invention is to effectively save energy by reducing unnecessary energy loss in the two concentration tower, to effectively separate the water and ethanol by the extractant, and to reduce the required stage of the extraction tower by reducing the amount of extractant circulation. Its purpose is.

Anhydrous ethanol production method using the extractive distillation of the present invention for achieving the above object,

(a) separating the diluted ethanol fermentation liquor and supplying the distilled ethanol fermentation column to the low pressure concentration tower and the high pressure concentration tower, respectively;

(b) distilling the dilute ethanol fermentation liquor supplied from each of the low pressure concentration tower and the high pressure concentration column to produce a concentrated ethanol vapor and a fluid product at the top of each concentration tower;

(c) condensing the concentrated ethanol vapor at the top of the low pressure column through a condenser;

(d) heat condensing the concentrated ethanol vapor at the top of the high pressure condenser with a low pressure condenser to compress the partially condensed vapor through a compressor;

(e) extracting and distilling the concentrated ethanol condensed and compressed in steps (c) and (d) with an extractant in an extraction tower to produce anhydrous ethanol vapor at the top of the extraction tower and a fluid product at the bottom;

(f) distilling the fluid product at the bottom of the extraction tower in a recovery tower to recover the extractant at the bottom of the recovery tower and refluxing the recovered extractant to the extraction tower; And

(g) condensing the anhydrous ethanol vapor produced in step (e) to produce anhydrous ethanol.

That is, the anhydrous ethanol production method according to the present invention is extracted from the concentrated ethanol vapor in the upper part of the high pressure concentration tower which is operated at a relatively high pressure in step (d) separately from the concentrated ethanol vapor in the upper part of the low pressure concentrate tower by using a compressor. By supplying the tower is characterized in that it can significantly reduce the energy consumption.

Another feature of the anhydrous ethanol production method using the extractive distillation of the present invention, in the step (f) to condense and discharge the steam generated in the upper part of the recovery tower, the condensation of the steam generated in the recovery tower top of the high pressure concentration tower It is made by exchanging heat with the reboiler and refluxing some of the uncondensed steam through the heat exchange to the recovery tower. That is, according to the present invention, by condensing the steam generated in the upper part of the recovery tower with the reboiler of the high-pressure concentrating tower to condense the energy efficiently, the water content ratio of the extractant recovered from the recovery tower to the extraction tower without energy loss. It can be significantly lowered, thereby increasing the content ratio of ethanol produced from the extraction tower.

In the method of producing anhydrous ethanol using the extractive distillation of the present invention, a method of compressing the steam generated in the upper part of the recovery tower through a compressor and then condensing it by heat exchange with a reboiler of the high pressure concentration tower may be used. As described above, according to the present invention, when the steam generated in the upper part of the recovery tower is compressed using a compressor and then heat exchanged with the reboiler of the high pressure concentration tower, the operation can be performed without excessively increasing the operating pressure of the recovery tower. Therefore, the safety of process operation can be ensured.

Anhydrous ethanol production method using the extractive distillation of the present invention, the ratio of the content of ethanol produced from the extraction tower further comprising the step of discharging the high-boiling impurities obtained in the side flow of the low pressure and the high pressure concentration column through a fluid separator To increase.

Anhydrous ethanol production method using the extractive distillation of the present invention, in order to increase the feed ratio of the fermented liquor supplied to the high pressure concentrated tower relative to the low pressure concentrated tower, in order to reduce unnecessary energy loss and effectively save energy, the step (a) In the dilute ethanol fermentation liquor, it is preferable to be supplied separately from the low pressure concentration tower and the high pressure concentration tower at a ratio of 4: 5-7.

In the anhydrous ethanol production method using the extractive distillation of the present invention, it is preferable to use a mixture of ethylene glycol and glycerol as the extractant used in step (e). In the case of using the mixture, while increasing the relative volatilization of ethanol and water while reducing the amount of extractant used to increase the separation effect of ethanol and water, it is possible to reduce the required stage of the extraction tower by reducing the amount of extractant circulation.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

1 shows anhydrous ethanol production process according to the present invention, referring to this, the anhydrous ethanol production method of the present invention is a low pressure concentration tower 100, high pressure concentration tower 200, extraction tower 300, and recovery tower The four towers of 400 each consist of a series of processes for producing concentrated ethanol and anhydrous ethanol through distillation, and recovering the extractant. On the other hand, Figure 1 schematically shows a process according to the present invention, a general configuration such as a heat exchanger for the initial start-up and the pump required to operate the four towers is omitted.

First, the distilled ethanol fermented liquor is supplied through the first tube, and the fermented liquor is separated and supplied to the low pressure concentration tower 100 and the high pressure concentration tower 200 through the second and third tubes. The low pressure concentrating tower 100 and the high pressure concentrating tower 200 are operated in parallel, respectively, distilling the fermented liquor supplied to produce concentrated ethanol vapor at the top of the tower and producing fluid products at the bottom of the tower. Concentrated ethanol obtained from the top of each concentration tower (100, 200) is supplied to the extraction tower 300, the fluid product obtained from the bottom is heat exchanged with the heat exchanger (110, 210) provided in the middle of the second and third pipes, each concentrated Preheat the fermented liquor supplied to the tower (100, 200).

The fermented liquor is preferably supplied in a low pressure concentration tower 100 and a high pressure concentration tower 200 at a ratio of 4: 5 to 7, more preferably at a ratio of 4: 5.5 to 6.5, and the high pressure concentration tower 200 is provided. Is operated at a higher operating pressure than the low pressure concentration tower (100). In addition, the concentrated ethanol vapor obtained from the high pressure concentration tower 200 is used as a heat source of the reboiler 120 for heating the low pressure concentration tower (100). As an example, the low pressure concentration tower 100 is operated at an operating pressure in the range of 0.1 to 0.5 kg / cm 2, and the high pressure concentration tower 200 is operated at an operating pressure in the range of 1.0 to 2.0 kg / cm 2. Preferably, in the present embodiment, the low pressure concentration tower 100 is operated at an operating pressure of 0.2 kg / cm 2, and the high pressure concentration tower 200 is operated at an operating pressure of 1.4 kg / cm 2. As such, by increasing the throughput in the high pressure concentration tower 200 compared to the low pressure concentration tower 100, it is possible to minimize the heat loss in the high pressure concentration tower 200 that is operated at a relatively high pressure, and further reduce energy Make sure

The concentrated ethanol vapor obtained at the top of the tower of the low pressure concentration tower 100 is condensed through the condenser 130. The condenser 130 condenses the concentrated ethanol vapor of the low pressure concentration tower 100 using an external refrigerant, a part of the concentrated ethanol condensed by the condenser 130 is refluxed to the low pressure concentration tower, and the rest is a product of the low pressure concentration tower. Obtained. Concentrated ethanol vapor obtained from the top of the tower of the high pressure concentration tower 200 is used as a heat source of the reboiler 120 of the low pressure concentration tower 100, a portion of the liquid condensed through the reboiler 120 is a high pressure concentration tower ( 200, the remainder is compressed through compressor 220. Condensed concentrated ethanol, which is the top top product of the low pressure concentration tower 100, and compressed concentrated ethanol, which is the top top product of the high pressure concentration tower 200, are supplied to the extraction tower 300 through pipes 10 and 11, respectively. At this time, the concentrated ethanol, which is the top product of the low pressure concentration tower 200, passes through a heat exchanger 140 installed in the middle of the tenth pipe, and is extracted by heat exchange with an extractant obtained at the bottom of the recovery tower 400 as described below. Supplied to the tower 300. The ethanol composition of the product obtained in each concentration tower (100, 200) is 63 ~ 84 mol%, the extraction tower 300 is treated with a relatively wide range of ethanol composition as described above.

The fluid product produced at the bottom of each concentration tower 100, 200 is separated by less than 0.01 mol% ethanol composition. At this time, at the upper end of each concentration tower (100, 200) to improve the stability of the process operation and to remove the high-boiling impurities (eg, fusel oil, etc.) generated during fermentation, a small amount of side flow is drawn through the tube 18 and 19 fluid separator Supply to 230. The fluid separator 230 discharges impurities to the outside, and a separate coolant is used to increase the fluid separation performance.

The concentrated ethanol vapor obtained from the low pressure concentration tower 100 and the high pressure concentration tower 200 is condensed and compressed through the condenser 130 and the compressor 220, respectively, and is supplied to the extraction tower 300, and the extraction tower 300. In extracting, concentrated ethanol is extracted and distilled using an extractant to produce anhydrous ethanol vapor at the top of the column and a fluid product at the bottom of the column. At this time, the extractant used is ethylene glycol (Ethylene glycol) or TEG (Triethylene glycol) can be used alone, but preferably a mixture of ethylene glycol and glycerol (Glycerol). The preferred weight ratio of the mixture is 60 to 90 wt% of ethylene glycol and 10 to 40 wt% of glycerol. As such, when the mixture of ethylene glycol and glycerol is used as an extractant, the relative volatility of ethanol and water can be increased to reduce the amount of extractant used, and to separate ethanol and water more efficiently. The effect of reducing the required stage of 300) can be obtained.

The fluid product generated at the bottom of the extraction tower 300 is introduced into the middle portion of the recovery tower 400, and the recovery tower 400 separates water and the extractant from the introduced fluid product. The operating pressure of the recovery tower 400 is a pressure high enough to allow the upper steam of the recovery tower 400 to be used as a heat source of the reboiler 250 of the high pressure concentration tower 200, for example, 2.0 to 4.0 kg / cm 2. And preferably 3.5 kg / cm 2. When the upper steam temperature of the recovery tower 400 is an inappropriate temperature to be used as a heat source of the reboiler 250 of the high pressure concentration tower 200, the pressure is increased by using the compressor 420 indicated by broken lines in FIG. 1. It can be utilized as a heat source of the reboiler 250. In this case, since the operating pressure of the recovery tower 400 does not have to be excessively increased, the process operation can be stabilized. The upper steam of the recovery tower 400 is used as a heat source of the reboiler 250 of the high-pressure concentrator 200, and then condensed, some are refluxed, and the other is introduced into the fluid separator 230 to treat wastewater.

The extractant is recovered from the bottom of the recovery tower 400, and the recovered extractant is refluxed to the upper portion of the extraction tower 300 by heat exchange with concentrated ethanol which is a product of the low pressure concentration tower 100. At this time, since the concentration of water in the bottom of the recovery tower 400 affects the composition of the anhydrous ethanol produced in the extraction tower 300, the extractant of the highest purity is recovered. Preferably, the water content of the extractant for producing at least 99.85 mol% of anhydrous ethanol is maintained at 0.01 mol% or less.

Extraction tower 300 is operated at a pressure of approximately 4.5 ~ 6.5 kg / ㎠, preferably at 5.1 kg / ㎠. The anhydrous ethanol vapor in the upper part of the extraction tower 300 operated at such a high pressure is used as a heat source of the reboiler 240 of the high pressure concentration tower 200, and is condensed by heat exchange with the reboiler 240. Some of the condensed anhydrous ethanol is produced as 99.5 ~ 99.85 mol% anhydrous ethanol product, the rest is refluxed to the top of the extraction tower (300).

Meanwhile, the reboilers 310 and 410 respectively provided in the extraction tower 300 and the recovery tower 400 are heated by an external heat source.

Characteristic of the process according to the invention is that the two concentration towers (100, 200) are operated in parallel to concentrate the diluted ethanol fermentation liquor to a low concentration (approximately 63 ~ 84 mol%) of ethanol and the concentrated ethanol extraction tower (300 ) Produces fuel grade anhydrous ethanol. In order to minimize the energy used in the process, the two concentration towers 100 and 200 have an appropriate pressure difference, and the fermentation liquor is separated at a ratio of about 4: 6 to the low pressure concentration tower 100 and the high pressure concentration tower 200. By supplying each, it is possible to compensate for the energy loss that can be relatively large in the high pressure concentration tower (200). The steam of the high pressure condensation tower 200, which is relatively high pressure, is used as a heat source of the reboiler 120 of the low pressure concentrating tower 100, and then condensed. The condensed liquid is refluxed in the high pressure condensing tower, and the gas phase is the compressor 220. It is supplied to the high pressure extraction tower 300 by using. The primary concentrated ethanol obtained in the low pressure concentration tower 100 is heat-exchanged with the extractant recycled from the bottom of the recovery tower 400 and then supplied to the high pressure extraction tower 300. In addition, the steam of the extraction tower 300 and the steam of the recovery tower 400 is used as a heat source of the reboilers 240 and 250 of the high pressure concentration tower 200. The lower fluid obtained in each concentration tower 100 and 200 exchanges heat with the fermentation wine supply pipe to save the total energy. Only the heat source of the reboilers 310 and 410 of the extraction tower 300 and the recovery tower 400 is introduced from the outside. In addition, the extractant used in the extraction tower 300 is a mixture of ethylene glycol and glycerol, so that the separation effect of ethanol and water can be further enhanced than when only ethylene glycol is used alone. The effect of reducing the stage can be obtained.

Example

The following examples show one embodiment of the anhydrous ethanol production method according to the present invention, <Table 1> shows the extract quality components and composition ratio of each stream in the process diagram of Figure 1, <Table 2> shows each tower Shows the energy usage at.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope of the technical idea of the present invention. It will be apparent to those of ordinary skill in Esau.

As described above, the anhydrous ethanol production method using the extractive distillation according to the present invention, environmentally friendly and continuous process is possible by using the extractive distillation, it is possible to drastically reduce energy consumption by changing the conventional heat exchange network and using a compressor. It is possible to treat the impurities generated in each tower waste water to increase the ethanol content ratio, to maintain the operating pressure of the recovery tower stable, to reduce the unnecessary energy loss by differentially supplying the fermentation liquor supply cost of the concentrated tower in parallel operation, It is possible to reduce the required stage of the extraction tower by increasing the separation effect of ethanol and water while reducing the amount of extractant.

Claims (19)

(a) separating the diluted ethanol fermentation liquor and supplying the distilled ethanol fermentation column to the low pressure concentration tower and the high pressure concentration tower, respectively; (b) distilling the dilute ethanol fermentation liquor supplied from each of the low pressure concentration tower and the high pressure concentration column to produce a concentrated ethanol vapor and a fluid product at the top of each concentration tower; (c) condensing the concentrated ethanol vapor at the top of the low pressure column through a condenser; (d) heat condensing the concentrated ethanol vapor at the top of the high pressure condenser with a low pressure condenser to compress the partially condensed vapor through a compressor; (e) extracting and distilling the concentrated ethanol condensed and compressed in steps (c) and (d) with an extractant in an extraction tower to produce anhydrous ethanol vapor at the top of the extraction tower and a fluid product at the bottom; (f) distilling the fluid product at the bottom of the extraction tower in a recovery tower to recover the extractant at the bottom of the recovery tower and refluxing the recovered extractant to the extraction tower; And (g) anhydrous ethanol production method using extractive distillation comprising the step of condensing the anhydrous ethanol vapor produced in step (e) to produce anhydrous ethanol. The method of claim 1, Anhydrous ethanol production method using an extractive distillation, characterized in that the step of condensing the steam generated in the upper part of the recovery tower in the step (f) through a fluid separator. The method of claim 2, Condensing the steam generated in the upper part of the recovery tower is an anhydrous ethanol production method using an extractive distillation, characterized in that the heat exchange with the reboiler of the high pressure concentration tower. The method of claim 3, wherein Anhydrous ethanol production method using an extractive distillation, characterized in that the steam generated in the upper part of the recovery tower is compressed through a compressor and then heat exchanged with the reboiler of the high pressure concentration tower. The method of claim 1, Anhydrous ethanol production method using an extractive distillation, characterized in that further comprising the step of discharging the high-boiling impurities obtained from the side of the low pressure concentration tower and the high pressure concentration column through a fluid separator. The method of claim 1, The extractant recovered from the bottom of the recovery tower in step (f) is refluxed by heat exchange with the concentrated ethanol vapor condensed in the step (c) anhydrous ethanol production method using an extractive distillation. The method of claim 1, Anhydrous ethanol production method using an extractive distillation, characterized in that further comprising the step of preheating the diluted ethanol fermentation liquor supplied to each concentration tower using the fluid product of the bottom of each concentration tower produced in step (b). The method of claim 1, The step (d) is an anhydrous ethanol production method using an extractive distillation, characterized in that the compressed ethanol vapor of the upper pressure column after the heat exchange with the reboiler of the low pressure concentration column. The method of claim 8, Anhydrous ethanol production method using an extractive distillation, characterized in that the reflux of the condensate obtained by partial condensation of the concentrated ethanol vapor in the upper portion of the high pressure concentrated tower heat exchanged with the reboiler of the low pressure concentrated tower. The method of claim 1, The step (g) is anhydrous ethanol production method using an extractive distillation, characterized in that the anhydrous ethanol vapor is condensed by heat exchange with the reboiler of the high pressure concentration tower. The method of claim 10, Anhydrous ethanol production method using an extractive distillation, characterized in that the reflux of the anhydrous ethanol heat exchanged with the reboiler of the high-pressure concentrate tower to the extraction column. The method of claim 1, Distilled ethanol fermentation in the step (a) 4: 5 ~ 7 anhydrous ethanol production method using an extractive distillation, characterized in that the separation is supplied to a low pressure concentration tower and a high pressure concentration tower. The method of claim 1, Anhydrous ethanol production method using an extractive distillation, characterized in that the extracting agent used in step (e) is ethylene glycol. The method of claim 1, Anhydrous ethanol production method using an extractive distillation, characterized in that the extracting agent used in step (e) is triethylene glycol. The method of claim 1, Extraction agent used in step (e) is an anhydrous ethanol production method using an extractive distillation, characterized in that ethylene glycol and glycerol is mixed. The method of claim 1, Operation pressure of the low pressure concentration tower is anhydrous ethanol production method using an extractive distillation, characterized in that 0.1 ~ 0.5 kg / ㎠. The method of claim 1, Anhydrous ethanol production method using an extractive distillation, characterized in that the operating pressure of the high pressure concentration tower is 1.0 ~ 2.0 kg / ㎠. The method of claim 1, Anhydrous ethanol production method using an extractive distillation, characterized in that the operating pressure of the extraction tower is 4.5 ~ 6.5 kg / ㎠. The method of claim 1, Operation pressure of the recovery tower is anhydrous ethanol production method using an extractive distillation, characterized in that 2.0 ~ 4.0 kg / ㎠.

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