JPS638753B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing fermented products that consumes less energy and that recovers and utilizes the fermentation reaction heat and the latent heat of vaporization of the fermented products. Recently, biomass has been attracting attention as an alternative energy source to petroleum resources, and there are expectations for the development of fermentation methods for producing alcohol for use in gasoline additives and various fuels from biomass, for example. However, in the conventional alcohol fermentation process, the ratio of input energy to output energy is close to 1, and there is a problem in energy efficiency, so it cannot be said to be suitable as a method for producing alcohol as an alternative energy source from biomass. In other words, in conventional fermentation processes, the concentration of fermentation products produced is low, and a large amount of energy is required to concentrate them.In the case of alcoholic fermentation, the alcohol produced inhibits yeast fermentation, reducing the rate of alcohol production. Fermentation reaction heat (for example, in ethanol fermentation, about 13 Kcal/
mol ethanol), a large amount of cooling water is required, and the cooling water that has heated up due to the heat is wasted.Moreover, power is required to circulate the cooling water, and the work environment is also cooled. It is not good due to water splashing, etc., and there is also significant corrosion of the structure.
There was a problem. Various methods and devices have been proposed to improve such fermentation processes. For example, a portion of the liquid extracted from the fermenter is heated in a heat exchanger, then guided to a flash evaporator, the ethanol-rich vapor is extracted into the gas phase, and this is led to a rectification column to produce azeotropic ethanol. A method in which the vapor at the top of the rectifying column is adiabatically compressed using a compressor and used as a heat source for the rectifying column and a heat exchanger in the front stage of the flash evaporator (ATPAL method, Chem.Age.
Nov. 21, (1980) p11). However, in this method, the rectifier must evaporate the ethanol vapor in the amount required for the total production and reflux (including water to balance), so the capacity of the rectifier vapor compressor is The volume is huge considering the scale of production.A portion of the compressor outlet gas is used as a reboiler heat source for the rectification column, which increases the temperature of the alcohol collection tank and increases the amount of ethanol that escapes from the vent due to evaporation. In order to increase the fermentation rate, if fermentation is already carried out at the maximum temperature at which microorganisms (bacterial cells) can be active, further heating the fermentation liquid with a heat exchanger will cause a thermal shock to the microorganisms in the fermentation liquid. give,
Therefore, it has the disadvantage that it may stop its activity and cause irreversible damage. Another method is to circulate the fermentation liquid through an evaporative cooler, evaporate water that is part of the fermentation liquid, increase the bacterial cell concentration and culture liquid concentration, and recirculate the cooled fermentation liquid (Special Publication No. 39-26041 No.). However, this method did nothing to recover or utilize the latent heat of vaporization, and could not be said to be satisfactory in terms of thermal efficiency. As a result of various studies to overcome the shortcomings and problems of the conventional methods, the inventors have determined that the fermenters can be divided into two types, depending on the fermentation rate: a pre-fermenter with a high fermentation rate, and a post-fermenter with a low fermentation rate. Divided into fermenters, 1st
A reduced pressure flash evaporator is connected to the fermenter with a high fermentation rate in the stage, and the fermented liquid is circulated through the flash evaporator to perform flash evaporation by self-evaporation.
After the fermentation product vapor is taken out and the temperature of the fermented liquor is controlled by its latent heat of vaporization, and a predetermined proportion of fermentation is completed, the fermented liquor from the first stage is sent to the post-fermentation tank to complete the fermentation. By heating the fermentation liquid in the two stages with steam from the flashing tank in the first stage fermentation, the fermentation heat and the latent heat of vaporization of the fermentation product (including the equilibrium water) are effectively used to cool the cooling water. It has been found that fermentation can be carried out in an extremely energy-efficient manner without the need for this method, thus meeting the above objectives. This invention has been made based on such knowledge. That is, this invention divides the fermenter into two stages according to the fermentation reaction rate: a pre-fermenter with a high reaction rate and a post-fermenter with a low reaction rate, and connects the pre-fermenter with the post-fermenter to perform flash evaporation. A tank is provided, and the fermentation liquid is circulated between the pre-fermentation tank and the flash evaporation tank to carry out flash evaporation and fermentation with a high reaction rate, and then the fermented liquid that has completed this fermentation is introduced into the post-fermentation tank. A method for producing a fermented product, characterized in that the fermented mash is further heated by the fermented product vapor containing equilibrium moisture vapor from the above-mentioned flash evaporator. This is what we provide. In this invention method, the fermenter is divided into two stages, front and rear, depending on the fermentation speed. Note that the first stage and second stage fermenters may be composed of a plurality of fermenters as appropriate. In this case, if the entire fermentation is carried out in one stage without dividing the fermenter into two stages, the time for the fermentation reaction with a low fermentation rate is longer than the time for the fermentation reaction with a high fermentation rate, so the volumetric efficiency of the fermenter (per unit volume) (fermentation yield) deteriorates. In addition, temperature control during fermentation also requires temperature control of the fermentation liquid at this time, as the amount of heat generated is large when the fermentation rate is high, so temperature control is facilitated by separating it into two stages as described above. and can be implemented efficiently. At this time, the second stage fermentation can be carried out in an open fermenter without the need for cooling water. The operating time (residence time in the tank) of the pre-fermenter in this first stage is generally the time from when the fermentation rate passes the peak to when it drops to A percent of this peak. This A can be said to be the optimum operation coefficient for flash fermentation, and the fermentation product production rate at the end of the fermentation operation in the above-mentioned pre-fermenter is expressed by the following equation. dc/dt=A (dc/dt) _nax , where c: fermentation product concentration t: fermentation time dc/dt: fermentation product production rate (dc/dt) _nax : maximum fermentation product production rate A: optimum for flash fermentation The operating coefficient A ranges from 0.05 to 0.83, preferably from 0.11 to 0.56, in the case of ethanol fermentation. In the case of acetone-butanol fermentation, A ranges from 0.075 to 0.14.
If A is too large outside these ranges, heat recovery in the first stage will not be sufficient and the temperature increase in the second stage fermenter will be 5° C. or more. On the other hand, if A is too small, the volume of the fermenter at the front stage becomes large even though the temperature rise in the fermenter at the later stage is as small as 1° C. or less, and the volumetric efficiency of the fermenter deteriorates. In this invention, a flash evaporation tank is connected to the first stage fermenter having a high fermentation rate. This achieves heat removal and temperature uniformity from the fermenter. Note that the fermentation liquid can be circulated between the fermentation tank and the flash evaporation tank by utilizing the operating pressure difference in the two tanks. The capacity of the flash evaporator is set to be large enough to remove the heat of fermentation reaction, and the flow rate of the fermentation liquor circulated to the flash evaporator is set at an amount corresponding to the fermentation rate, that is, the heat of fermentation reaction. At this time, the circulation flow rate is controlled so that the liquid level in the flash evaporation tank remains constant. If the fermenter is operated in batch mode, multiple fermenters are combined with a considerable number of flash evaporators and operated in parallel at fixed time intervals to reduce fluctuations in the flow rate of steam generated from the batch fermenter. It is preferable to equalize by the number of parallel lines. After the steam containing the fermentation products generated in the flash evaporator is recovered, the fermentation heat energy contained in the steam is converted into a form that can be easily used in the distillation process. This is achieved by installing vacuum pumps in two stages to achieve the vacuum level in the flash evaporation tank and extracting steam, and then post-fermenting the steam leaving the first stage vacuum pump before entering the second stage vacuum pump. Preferably, this is carried out by cooling and condensing the thermal mash from the tank and at the same time preheating the fermentation liquor. Next, the method of the present invention will be explained in more detail based on the drawings. The drawing is a flow sheet showing a simplified embodiment of the method of the present invention, and is an example of ethanol fermentation using yeast. The pre-fermentation tank 2 consists of five fermentation tanks, each of which receives a predetermined amount of fermentation liquid through the fermentation liquid supply line 1.
Start preparing from 9. Next, a pre-cultured yeast mash is added to the pre-fermentation tank 2 from the mash tank 1, and air is blown through the air line 20 to start fermentation. 21 is a scrubber that recovers ethanol vapor accompanying carbon dioxide gas. After several hours have passed after addition of the yeast mash, a portion of the fermentation liquid is extracted from the pre-fermentation tank 2 and transferred to the five fermentation tanks each connected to the above-mentioned five fermentation tanks by a liquid circulation line 4 having a circulation pump 3. It is circulated between a flash evaporation tank consisting of a flash drum. The fermented liquid from which ethanol has been evaporated under reduced pressure in the flash evaporator 5 is returned to the pre-fermenter 2. After a certain percentage of fermentation has been completed in this way, the fermented liquor in the pre-fermenter 2 is taken out from the take-out line 15 and sent to the post-fermenter 6, where it is allowed to stay for a predetermined period of time to perform the remaining fermentation and aging. . The steam generated from the flash evaporation tank 5 is collected in a header, compressed by a vacuum pump 17 in a steam line 8 provided with a vacuum pump 17, and then passed through an intercooler 9. Here, heat exchange is performed with the aged mash extracted from the post-fermentation tank 6 and sent through the mash line 16 by the pump 7. The vapor is thereby cooled and condensed, and the condensed liquid is separated in the gas-liquid separator 10. The uncondensed vapor is sent to a line 11 with a vacuum pump 12, and after being recompressed by the vacuum pump 12, it is sent to a final cooler 13.
It is cooled and condensed. The condensed liquid from the gas-liquid separator 10 is sent from the line 14 to the aging mash tank 18, and the condensed liquid from the cooler 13 is also sent to the aged mash tank 18, and these condensed liquids are heated by sensible heat. Therefore, the temperature of the aged mash is further raised by mixing it with the aged mash fed into the aged mash tank 18 from the mash liquid line 16. The aged mash heated in this way is sent to the distillation process via line 22. In the above operation conditions, the temperature of the pre-fermenter 2 is preferably 28 to 35°C. If the temperature is too low or too high outside this range, the fermentation rate will decrease. Further, the pressure is preferably 1 atm in order to diffuse the generated carbon dioxide into the atmosphere. Further, the temperature of the post-fermenting tank 6 is within a range not higher than the temperature of the pre-fermenting tank 2 by 2°C or more, that is, 35-37°C or less, and the pressure can be 1 atm. The temperature of the flash evaporator 5 is lower than that of the pre-fermenter 2.
It is preferable to lower the temperature by ~2℃, and the boiling pressure of the fermented liquid at that time becomes the operating pressure, which is usually 25 to 70 Torr.
It is. Next, in order to enable the gas-liquid separator 10 to be cooled with the matured mash from the post-fermenter 6, the pressure is maintained at equilibrium at a temperature of 3°C or higher, i.e., 60~60°C.
500 Torr, preferably 100 to 250 Torr. In the above description, a case has been described in which the pre-fermenter is operated in a batch manner, but it goes without saying that the method is not limited to this and a continuous type can be employed as appropriate. The following table shows the utility consumption, fermenter volumetric efficiency, etc. when fermentation is carried out using a fermentation device with an ethanol production scale of 100K/day according to the method in the above flow sheet, in comparison with the conventional method.

【table】

[Table] However, in contrast to the method of the present invention, the conventional method adopts a temperature control method by cooling the fermenter tank wall with irrigation water, and therefore does not have a flash evaporator or vapor compression device, and is divided into a front stage and a rear stage. The difference is that it does not use a traditional fermentation system. As described above, the present invention divides the fermenter into two stages, front and rear, and utilizes the latent heat of vaporization of the fermented product and recovers the heat of fermentation reaction, and achieves the following excellent effects. (1) Fermentation reaction heat, which has not been recovered in the past, can be recovered and used to preheat the aged mash after fermentation, which greatly reduces thermal energy in subsequent processes such as the distillation process. This method is suitable as a method for producing consumable fermentation products. (2) There is no need to water-cool the fermenter, so there is no need for a cooling device or cooling water. Therefore, the power required for circulating the cooling water is also reduced. (3) Since fermentation is carried out while removing a certain amount of fermentation products from the pre-fermentation tank, it is possible to prevent fermentation inhibition of the fermentation products, increase the fermentation reaction rate, and increase the production amount. When the fermentation product has a relative volatility of 1 or more with respect to a solvent (such as water), the concentration of the fermentation product can be increased compared to the conventional method. This invention method includes ethanol fermentation, acetone fermentation,
It can be applied to exothermic fermentation reactions, such as butanol fermentation, where the fermentation product is a volatile substance that has a vapor pressure at its fermentation temperature. Next, the present invention will be explained in more detail based on examples. Note that % in the description represents weight %. EXAMPLE Ethanol fermentation was carried out according to the flow sheet of the present invention shown in the drawings. From the fermentation solution supply line 19 to each tank of the pre-fermentation tank 2, 15.3% of the sugar solution is supplied at staggered intervals of 12 hours.
%, water 82.2%, and other nutrients 2.5% was charged at a rate of 45390 kg/hr, and each tank was charged with 554680 kg of fermented liquid. After the preparation was completed, the mash was added to each tank, air was blown through the air line 20 for the first few hours, and fermentation in the pre-fermentation tank 2 was started at 33°C and 1 atm. After 5 hours of addition of the yeast mother, the fermentation liquor is extracted from the pre-fermentation tank 2 at a rate of 199,720 kg/hr, and circulation with the flash evaporation tank 5 is started. The flash evaporator 5 is operated at 33° C. and 64 Torr. Fermentation was carried out in this manner, and 48 hours after the start of fermentation, the composition of the fermentation liquor in the pre-fermenter 2 was 7.0% ethanol, 1.8% sugar solution, 88.5% water, and 3.0% others. Therefore, this fermentation liquid was taken out from the takeout line 15 at a rate of 40,720 kg/hr and introduced into the post-fermentation tank 6. After this, in the fermentation tank 6, the fermented liquid is left as it is at 1 atm for 72 hours to carry out the remaining fermentation and aging.
A matured mash at 35.4°C was obtained with a composition of 7.6% ethanol, 87.4% water, and 2.93% others. On the other hand, the steam generated from the flash evaporation tank 5 and collected in the header contains 19.2% ethanol,
The composition was 0.9% CO ₂ and 79.9% water, and the amount generated was 1590 Kg/hr. After compressing this ethanol vapor with the vacuum pump 17 to make it into vapor at 285°C and 250 Torr,
It is led to the intercooler 9, where it undergoes heat exchange with the aged mash (40,290 kg/hr (35.4°C)) extracted from the post-fermenter 6 and sent from the mash liquid line 16, and aged. The moromi is heated to 57℃. On the other hand, the ethanol vapor was cooled and condensed to form a multiphase flow at 50° C. and 200 Torr, and the condensed liquid was separated in the gas-liquid separator 10. The condensate has a composition of 18.2% ethanol, 81.8% water, and a temperature of 50℃.
Kg/hr is sent to aging mash tank 18. The vapor that is not condensed in the gas-liquid separator 10 is recompressed in the vacuum pump 12 and then cooled in the final cooler 13 to produce a condensate containing 62.3% ethanol and 37.7% water at a rate of 40 kg/hr. Sent to 18. These condensates are mixed with the aged mash, which has been heated to 57°C, which is sent from the mash line 16 to the aged mash tank 18, and is mixed with 8.0% ethanol and water.
Aged mash with a composition of 89.1% and 2.8% at a temperature of 56.7°C was obtained at a rate of 41,860 Kg/hr.

[Brief explanation of the drawing]

The drawing is a flow sheet showing one example of the method for producing fermented products of the present invention. Explanation of symbols, 2... Pre-fermenter, 4... Liquid circulation line, 5... Flush evaporator, 6... Post-fermenter, 8... Generated steam line, 9... Intercooler,
10... Gas-liquid separator, 12, 17... Vacuum pump, 14... Condensate line, 16... Mash liquid line, 18... Aging mash tank, 19... Raw material liquid supply line, 20... Air line , 22... Aging mash removal line.

Claims (1)

[Scope of Claims] 1. Fermentation tanks are divided into two types according to the fermentation reaction rate: a pre-fermenter with a high reaction rate and a post-fermenter with a low reaction rate.
The pre-fermenter is divided into stages, and a flash evaporation tank is connected to the pre-fermenter, and the fermentation liquid is circulated between the pre-fermenter and the flash evaporator to perform flash evaporation and fermentation with a high reaction rate. Then, the fermented liquor that has completed this fermentation is introduced into the post-fermentation tank to complete the fermentation, and the aged mash that has completed this fermentation is then transferred from the above-mentioned flat evaporation tank.
A method for producing a fermented product, characterized in that heating is performed using fermented product vapor containing equilibrium water vapor. 2 The fermentation reaction is ethanol fermentation or acetone fermentation.
This is butanol fermentation, and the fermentation operation in the pre-fermenter is performed until the fermentation product production rate has passed the peak dc/dt = A (dc/dt) _nax (where c: fermentation product concentration t: fermentation time dc/dt: Fermentation product production rate (dc/dt) _nax : Maximum fermentation product production rate, A is 0.05 to 0.83 (0.05 to 0.83 in the case of ethanol fermentation, 0.075 to 0.14 in the case of acetone/butanol fermentation). ) The method for producing a fermented product according to claim 1, wherein the method is carried out until the range specified in (1) is reached. 3. The method for producing a fermented product according to claim 1, wherein the aged mash heated by fermented product vapor containing equilibrium water vapor is sent to a distillation process.