JPS6338191B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing fermentation products such as ethanol, acetone, butanol, etc. by effectively utilizing the thermal energy of fermentation liquid. Fermentation processes using microorganisms have the advantage of being able to carry out synthesis reactions at room temperature and pressure, compared to chemical synthesis methods that have been widely used in the past, but generally produce the desired product at a low concentration (10 %
1-2% in acetone butanol fermentation),
Therefore, it has the disadvantage that a large amount of energy is consumed to concentrate and separate it. On the other hand, at present, however, the heat generated by microorganisms during fermentation reactions, that is, reaction heat, is usually simply removed using shower coolers, flash coolers, cooling coils, and the like. In ethanol fermentation, this generated heat is expressed as follows:
Reaching 26Kcal/mol glucose. This amounts to about 1/4 of the amount of heat required to strip ethanol from, for example, a 10% aqueous ethanol solution. C ₆ H ₁₂ O ₆ →2C ₂ H ₅ OH + CO ₂ + 26 Kcal/mol glucose Various methods and devices have been proposed to improve the drawbacks of this fermentation process. For example, in the fermentation production of ethanol, a fermentation tank or a flash tank combined with a fermentation tank is depressurized to remove ethanol-rich evaporation (US Pat. No. 2,440,925). There is a method (Japanese Patent Publication No. 39-26041) that removes it by circulating it. However, in this method, the extracted steam is cooled in a condenser, which still results in heat loss. There are also other problems, such as the need for power to compress the condenser to normal pressure during cooling, and the need for deep cooling to cool the condenser. The other method is intended to concentrate the fermentation liquid, and has the disadvantage that only the volatile fermentation product (+water) can be obtained in an amount corresponding to the calorific value of the fermentation reaction. Furthermore, with respect to these conventional techniques, there is a severe debate as to whether the energy required to produce fermentation products such as ethanol is greater than the energy contained in fermentation products such as ethanol. Therefore, as a particularly low-cost ethanol fermentation method, a portion of the liquid extracted from the fermenter is heated through a heat exchanger, and then guided to a vacuum flash evaporator.
The ethanol-rich vapor is taken out into the gas phase, which is led to a vacuum rectification column to produce azeotropic ethanol (95vol%
ethanol), and then adiabatically compresses the vapor at the top of the rectification column using a compressor to use it as a heat source for the rectification column and a heat source for the heat exchanger at the front stage of the vacuum flash evaporator (ATPAL method, Chem.Age,
Nov. 21, (1980) p11) is proposed. However, in this method, the amount of heat required to evaporate the ethanol is transported in the form of sensible heat from the heat exchanger to the vacuum flash evaporator, so the amount of circulating fermentation liquid is large and the required heat transfer area of the heat exchanger is also large. It had the following drawbacks. Furthermore, a disadvantage of this method is that if fermentation is already carried out at the maximum temperature at which microorganisms (bacterial cells) can be active in order to increase the fermentation rate in the fermenter, the fermentation liquid may be further heated with a heat exchanger. The microbial cells in the fermentation broth are subjected to a thermal shock, which can stop their activity and cause irreversible damage. In order to overcome the shortcomings and problems of these conventional methods, the inventors conducted various studies, and as a result, they extracted a portion of the fermentation liquid containing fermentation products from the fermenter,
This is led to an evaporator with a built-in heat exchanger whose pressure is reduced to below the vapor pressure at the fermentation temperature, where volatile (boiling point lower than water) fermentation products are evaporated, and the steam containing this fermentation product is compressed and heated. If this is used as a heating source for an evaporator with a built-in heat exchanger, the above objectives can be achieved: removal of fermentation reaction heat, effective use of the reaction heat for evaporation, and energy-saving evaporation concentration of fermentation products without damaging bacterial cells. found that it can be achieved. This invention has been completed based on this knowledge. That is, the present invention extracts a part of the fermentation liquid containing volatile fermentation products from the fermenter and depressurizes it below the vapor pressure at the fermentation temperature, thereby performing heat exchange in which a liquid hydrostatic head is not substantially generated. circulates to the built-in evaporator to generate volatile fermentation product vapor,
The present invention provides a method for producing a volatile fermentation product, which is characterized in that the vapor is adiabatically compressed, heated, and used as a heating source for an evaporator with a built-in heat exchanger. In this invention, there is no particular restriction on the type of evaporator with a built-in heat exchanger used, but the heat exchanger may be a falling film type, a falling thin film type, a thin film type (horizontal tube type),
Types such as the Luwa type, which have a structure in which virtually no hydrostatic head is generated, are used because they have good cooling efficiency for the fermentation liquid. The evaporator with a built-in heat exchanger is operated at a reduced pressure below the vapor pressure at the fermentation temperature (a degree of vacuum at which the fermentation liquor containing volatile fermentation products boils below the fermentation temperature). The specific degree of pressure reduction varies depending on the type of fermentation reaction and the fermentation temperature of the fermenter at that time, but it is usually
It ranges from 720 to 20 torr, preferably from 150 to 30 torr. To put this more specifically, in ethanol fermentation, the maximum temperature at which fermentation can be practically carried out with current yeast (Saccharomyces genus) is around 35°C at normal pressure, but when the ethanol concentration is 6% by volume, the pressure is reduced to 50 torr. It is preferable to do so. The fermentation temperature, that is, the temperature of the fermentation liquid in the fermenter, varies depending on the type of fermentation reaction, but is usually between 20 and 80℃.
℃ range, preferably 30 to 65℃ range. In this invention, the rate of withdrawal of the fermented liquor from the fermenter is 10%/10% of the fermented liquor retained in the fermenter.
A range of 180% per hour to 180% per hour is preferred. The fermented liquor from which volatile fermentation products have been removed by evaporation in the evaporator with a built-in heat exchanger is circulated to the fermenter after fermentation heat is also removed by evaporation. Therefore, the fermentation reaction can proceed smoothly by cooling the fermenter, and fermentation inhibition can be reduced by removing fermentation products. On the other hand, the vapor rich in volatile fermentation products removed by evaporation in the evaporator with a built-in heat exchanger is compressed adiabatically, and after increasing the temperature and pressure, it is heated by the evaporator with a built-in heat exchanger. used as a liquid, it is cooled and liquefied in its evaporator. After adiabatic compression, the temperature of the vapor rich in volatile fermentation products is 3 to 20°C higher than the temperature of the fermentation liquor in the fermenter. The method of this invention can be applied to ethanol fermentation, acetone butanol fermentation, etc. Next, the present invention will be explained in more detail with reference to the drawings. Figure 1 shows the conventional ATPAL method described above.
A process flow sheet is shown, and FIG. 2 shows a flow sheet as one embodiment of the method of the present invention. In Figure 1, feed line 2 is connected to fermenter 1.
The fermentation raw material is supplied through
CO ₂ ) is exhausted through vent line 3. The fermentation liquor containing volatile products is extracted through the fermentation liquor withdrawal line 4, heated in a heat exchanger 5, and then sent to a flash evaporator 6 where it is subjected to flash evaporation treatment. Vapor rich in volatile products separated by this flash evaporation is sent to a rectification column 8 via a line 7, and vapor of volatile products is sent to a vapor compressor 10 via a rectification column overhead vapor line 9.
This compressed steam is sent to the heat exchanger 5 through the line 11 and used as a heating source for the heat exchanger 5.
2, it is taken out as condensed steam. On the other hand, the fermentation liquor which has released vapor rich in volatile products is returned to the fermenter 1 through the fermentation liquor return line 13. 14 is a line for taking out the bottom liquid of the rectification column 8. Next, the method of the present invention will be explained with reference to FIG. In the same figure, as in the case of FIG. 1, the fermentation raw material supplied to the fermenter 1 through the feed line 2 undergoes a fermentation reaction to produce fermentation products, and gaseous products (e.g. CO ₂ ) are discharged through the vent line 3. be done. The fermentation liquor containing volatile fermentation products is led to the evaporator 16 with a built-in heat exchanger through the fermentation liquor withdrawal line 15, where it releases steam rich in volatile fermentation products and fermentation heat, and passes through the heat exchanger. After being cooled to the boiling point of the fermentation liquor corresponding to the degree of pressure reduction in the built-in evaporator 16, the fermentation liquor is returned to the fermentation tank 1 through the fermentation liquor return line 17. The evaporator 16 with a built-in heat exchanger has a structure that does not generate a liquid hydrostatic head on the heat transfer surface like a falling film heat exchanger, so the temperature of the fermented liquid within this evaporator is maintained at a predetermined degree of vacuum. The boiling point is maintained below the fermentation temperature, so it does not reduce the activity of the bacteria involved in the fermentation reaction. Next, the steam rich in volatile fermentation products discharged from the evaporator 16 with a built-in heat exchanger is transferred to the evaporative steam line 18.
After being compressed and heated by the vapor compressor 19, it is supplied as a heating medium to the evaporator 16 with a built-in heat exchanger through the compressed vapor line 20, supplying heat to the fermentation liquid via the heat transfer surface, and condensing itself. Then, it is taken out of the system via the condensed steam line 21. As described above, the present invention extracts a portion of the fermentation liquid from the fermenter, guides it to the evaporator with a built-in heat exchanger operated under reduced pressure, generates steam rich in volatile fermentation products, and removes the fermentation products. This method is characterized by transferring the fermentation product into the gas phase, adiabatically compressing the vapor of the fermentation product, and using it as a heat source for the evaporator, and has excellent effects as described below. (1) Volatile fermentation products can be separated and concentrated from the fermentation liquid and condensed and recovered using the heat of fermentation and the heat of condensation resulting from the compression of evaporated steam. Fermentation products can be concentrated and recovered using energy, and distillation can be performed using far less energy than traditional distillation methods. Therefore, this invention is intended to overcome the problem of energy input from biomass, which is currently attracting worldwide attention, where the energy input into the process is greater than the energy produced, resulting in no true energy production. There is a lot to contribute. (2) Especially compared to the above-mentioned ATPAL process, there is no need to further raise the temperature of the fermentation liquid, so thermal shock does not damage or reduce the activity of microbial cells involved in the fermentation reaction. Furthermore, since the evaporator has a built-in heat exchanger, the amount of circulating fluid can be small, and the heat transfer efficiency is high, so the heat transfer area can be small. (3) Furthermore, in the ATPAL process, the steam at the outlet of the rectification column is introduced as a heat source for the heat exchanger before the flash evaporator, and in actual operation, the operation of both must always be harmonized, which is difficult. In contrast, the present invention uses vapor compression within a single piece of equipment, making it easier to operate in practice. (4) In addition, without using a distillation device that has a pressure drop like a stripping tower, the pressure drop (liquid hydrostatic head)
Since an evaporator with no structure is used, less pressure is required for depressurization. Furthermore, the steam leaving the evaporator is
Since it is cooled by itself in an evaporator and liquefied, no cooling water is required. (5) Fermentation products can be continuously taken out of the system, making it easy to make the fermentation process continuous. (6) Furthermore, even if there is product inhibition such as in alcoholic fermentation (produced alcohol reduces yeast activity), product inhibition can be prevented because the product is continuously extracted. Fermentation speed can be kept high. Next, the present invention will be explained in more detail based on examples. EXAMPLE Ethanol fermentation was carried out according to the flow sheet of the present invention shown in FIG. Contains 5.9% ethanol and baker's yeast, 35% by weight
To the fermenter 1 containing 26,000 g of fermentation liquid kept at ℃, 1,511 g of a 33% by weight glucose aqueous solution was added per hour through the feed line 2, while 24,000 g of fermentation liquid per hour was drawn out from the fermentation liquid extraction line 15, and the pressure was reduced to 44 torr. Evaporator with built-in heat exchanger 1
6, and 1276 g of water-containing ethanol vapor with an ethanol concentration of 20.2% by weight was obtained from the evaporator 16 per hour. The fermentation liquid is heated to 32℃ in the evaporator 16 with a built-in vacuum heat exchanger.
It is cooled down to
±35°C without external cooling by other means
The temperature is maintained at 1℃, and the ethanol concentration in fermenter 1 is
It was maintained at 5.9±0.5% by weight. The water-containing ethanol vapor obtained in the evaporator 16 is adiabatically compressed in the vapor compressor 19, heated to 40°C, and used as a heating source for the heat exchanger in the evaporator 16, and is cooled and converted into a condensate. A multiphase flow of uncondensed vapor was obtained. The proportion of condensate in the multiphase flow was 85% by weight. The heat transfer area of the heat exchanger incorporated in the evaporator 16 at this time was 0.02 m ² , and sufficient heat exchange performance was achieved. Comparative Example Ethanol fermentation was carried out according to the flow sheet shown in FIG. 33 to fermenter 1 having the same fermentation liquid as in Example 1.
% glucose aqueous solution was added per hour, 82000 g of fermented liquid was extracted per hour from the fermented liquid extraction line 4, and heated to 37°C in the heat exchanger 5.
The mixture was fed into a flash evaporator 6 whose pressure was reduced to 44 torr to obtain 1276 g/hour of water-containing ethanol vapor containing 20.2% by weight of ethanol. The fermented liquid is stored in a depressurized flash evaporator 6.
℃ and returned to fermenter 1, which is then cooled to 35℃± without external cooling by other means.
The temperature was maintained at 1° C., and the ethanol concentration in fermenter 1 was maintained at 5.9±0.5% by weight. The water-containing ethanol vapor obtained in the flash evaporator 6 is heated to 40°C by adiabatic compression in the vapor compressor 10, and is used as a heating source for the heat exchanger 5, where it is cooled and separated into condensed liquid and condensed vapor. A multiphase flow was obtained. The proportion of condensate in the multiphase flow is 85% by weight
It was hot. At this time, in order to obtain sufficient heat exchange performance of the heat exchanger 5, a heat transfer area of 0.13 m ² was required. The results of Examples and Comparative Examples are summarized in the following table.

[Table] Steam

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an example of a conventional method for producing fermented products, and FIG. 2 is a flow sheet showing an example of the method for producing fermented products of the present invention. Explanation of symbols, 1... Fermentation tank, 2... Feed line, 3... Vent line, 15... Fermented liquor extraction line, 16... Evaporator with built-in heat exchanger, 17
... Fermentation liquid return line, 18 ... Evaporation steam line, 19 ... Vapor compressor, 20 ... Compressed steam line, 21 ... Condensed steam line.

Claims (1)

[Scope of Claims] 1 A part of the fermentation liquid containing volatile fermentation products is extracted from the fermenter and the pressure is reduced to below the vapor pressure at the fermentation temperature, thereby generating heat that substantially does not generate a liquid hydrostatic head. Volatile fermentation production characterized by circulating to an evaporator with a built-in exchanger to evaporate the volatile fermentation product, adiabatically compressing this vapor to raise the temperature, and using the vapor as a heating source for the evaporator with a built-in heat exchanger. How things are manufactured. 2 The evaporator with built-in heat exchanger is a falling film type falling film type,
The method for producing a volatile fermentation product according to claim 1, which has a horizontal tube type thin film type or Luwa type structure. 3. The method for producing a volatile fermentation product according to claim 1, wherein the volatile fermentation product is ethanol, acetone, or butanol.