JP6518070B2 - Ethanol synthesis method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for synthesizing ethanol from a source gas such as syngas, and more particularly to an ethanol synthesis method and apparatus suitable for performing ethanol synthesis after removing a hydrocarbon compound such as benzene in the source gas. .

  The plant which manufactures ethanol from source gas, such as syngas (syngas), is publicly known (refer to patent documents 1, 2 grade). This type of plant often requires a step of removing aromatic compounds such as BETX (benzene, ethylbenzene, toluene, xylene) in syngas and other hydrocarbon compounds. For example, in the case of purifying ethanol by the fermentative action of an anaerobic microorganism, it is considered that BETX or the like adversely affects the activity of the anaerobic microorganism (see Patent Document 3 and the like).

As a method of removing BETX from syngas, a PSA (pressure-swing absorption) method or a water absorption method can be considered.
The PSA method is to make a solid absorbent such as zeolite absorb BETX in syngas. The solid absorbent is then regenerated by desorbing the BETX from the solid absorbent by evacuation.
In the water absorption method, water is made to absorb BETX. The water after absorption is released to the atmosphere to evaporate BETX.

JP 2004-504058 A JP, 2012-217886, A JP, 2014-050406, A ([0096], [0102])

The PSA method has the following problems.
(1) It is necessary to periodically replace the solid absorbent because the solid absorbent is susceptible to damage by sulfur in syngas.
(2) Since solid absorbents absorb not only BETX but also water, water removal in syngas is indispensable.
(3) The power consumption for driving a vacuum pump or the like to regenerate the solid absorbent or heating for removing water is large.
(4) The production efficiency of ethanol is reduced because the solid absorbent also absorbs raw material components such as CO and H ₂ .

The water system has the following issues.
(1) A large amount of water is required because the solubility of water in BETX is low.
(2) When air is released to regenerate water, BETX is released to the environment and mixed with a large amount of air. It is almost impossible to recover and process this BETX.

  In view of the above circumstances, the present invention efficiently removes aromatic compounds such as BEXT (benzene, ethylbenzene, toluene, xylene) and other hydrocarbon compounds from a raw material gas such as syngas, and efficiently produces ethanol. The purpose is to

In order to solve the above problems, the method of the present invention is an ethanol synthesis method for synthesizing ethanol from a source gas such as syngas,
An absorption step of bringing a hydrocarbon compound contained in the raw material gas into the absorption liquid by bringing the raw material gas before the synthesis step of ethanol into contact with the absorption liquid containing ethanol;
A separation / regeneration step of separating the hydrocarbon compound from the absorption liquid after the absorption step to make the absorption liquid reusable;
It is characterized by having.

  Examples of the hydrocarbon compound include BET X, that is, aromatic compounds such as benzene, ethylbenzene, toluene and xylene. Ethanol has a higher ability to absorb these hydrocarbon compounds than water. Therefore, by using the absorption liquid containing ethanol, hydrocarbon compounds can be efficiently removed from the raw material gas. As a result, the quality of the source gas can be improved, and ethanol for synthesis can be efficiently produced. In addition, the required flow rate of the absorbing solution can be reduced, and enlargement of the equipment can be avoided. Furthermore, by the separation and regeneration step, the absorbing ability of the absorbing liquid to hydrocarbon compounds can be recovered (regenerated), and the absorbing liquid can be recycled and reused.

In the ethanol synthesis step, the source gas after the absorption step is introduced into a culture solution, and ethanol is synthesized from the source gas by fermentation of anaerobic microorganisms in the culture solution,
The method further comprises a purification step of purifying ethanol from the culture solution after the ethanol synthesis step,
It is preferable that at least a part of the purification process also serves as the separation and regeneration process by sending the absorption liquid after the absorption process to the purification process.
By this, it is possible to omit the separation / regeneration step dedicated to the absorbent after the absorption step, and to simplify the treatment process. By making the absorbing substance that absorbs the hydrocarbon compound and the target substance of the synthesis the same substance (ethanol), it is advantageous in terms of man-hours, equipment cost, etc. as compared to using different substances.
On the other hand, when an absorption part using ethanol is used in a plant for synthesizing a substance other than ethanol (for example, butanol etc.), ethanol is removed from the system by heating or cooling after the absorption step or recovered. Need to be added, the additional equipment is increased, and the cost is increased. When a hydrocarbon compound is absorbed by a substance other than ethanol (such as butanol) in a plant that synthesizes ethanol, the substance other than ethanol is removed from the system by heating or cooling after the absorption step, or recovered. Need to be added, the additional equipment is increased, and the cost is increased.

And a storage step of storing the absorption liquid after the absorption step in a liquid tank after absorption,
It is preferable to use the absorption liquid in the post-absorption liquid tank for the separation and regeneration step.
Even if the concentration of the hydrocarbon compound in the absorbing liquid after the absorbing step fluctuates due to fluctuations in the partial pressure of the hydrocarbon compound in the raw material gas, the absorbing liquid after the absorbing step is stored in the liquid tank after absorption The hydrocarbon compound concentration can be averaged and stabilized at a concentration sufficiently lower than the concentration at peak time. By subjecting the absorbing solution with a low hydrocarbon compound concentration to the separation and regeneration step to this stable and low hydrocarbon compound concentration, it is possible to avoid exceeding the treatment capacity of separation and regeneration, and to cope with the peak of hydrocarbon compound concentration. There is no need to

An ethanol synthesis apparatus according to the present invention is an ethanol synthesis apparatus having an ethanol synthesis unit that synthesizes ethanol from a source gas such as syngas.
An absorbing unit for bringing a hydrocarbon compound contained in the raw material gas into absorption into the absorbing solution by bringing the raw material gas before introduction into the ethanol synthesis unit into contact with an absorbing solution containing ethanol;
A separation / regeneration unit that separates the hydrocarbon compound from the absorption liquid after absorption to make the absorption liquid reusable;
It is characterized by having.
As a result, hydrocarbon compounds can be efficiently removed from the source gas, the quality of the source gas can be improved, and ethanol for synthesis purposes can be efficiently produced. In addition, the required flow rate of the absorbing solution can be reduced, and enlargement of the equipment can be avoided. Furthermore, in the separation and regeneration section, the absorbing ability of the absorbing liquid to hydrocarbon compounds can be recovered (regenerated), and the absorbing liquid can be recycled and reused by returning it to the absorbing section.

The ethanol synthesis unit has a culture vessel for culturing, in a culture solution, an anaerobic microorganism which synthesizes ethanol from the raw material gas by fermentation.
Further, an after-absorption gas path for sending the absorbed source gas to the culture tank,
A purification unit for purifying ethanol from the culture solution after the ethanol synthesis;
And d) a regeneration path for transferring the absorption liquid after absorption to the purification unit,
Preferably, at least a part of the purification unit is provided as the separation and regeneration unit.
By this, it is possible to omit the separating and regenerating part dedicated to the absorbing liquid after absorption. In this type of anaerobic microorganism-based ethanol synthesis system, a purification unit that purifies ethanol from the culture solution after ethanol synthesis is generally provided (see Patent Document 1 etc.), so use this existing purification unit. The absorbent can be regenerated. Therefore, the facility can be prevented from becoming large-scaled, and an increase in facility cost can be avoided.

The purification unit comprises a plurality of distillation towers connected in sequence;
The culture vessel is connected to the first distillation column of the first stage,
The regeneration path is connected to a second distillation column connected in a stage subsequent to the first distillation column,
Furthermore, it is preferable to provide a regeneration return path for returning a part of the bottoms of the second distillation column as the absorption liquid to the absorption part.
A relatively high-concentration ethanol distillate can be obtained by distilling the culture solution after the ethanol synthesis in the first distillation column. The ethanol distillate is introduced into the second distillation column, and the absorption liquid after absorption is introduced into the second distillation column. These two liquids are preferably mixed with each other and introduced into the second distillation column, but may be introduced separately into the second distillation column and mixed in the second distillation column. The mixed solution is distilled in the second distillation column to separate and remove the hydrocarbon compound derived from the absorption solution after absorption.
By connecting the regeneration path to the second distillation column instead of the first distillation column, the ethanol concentration of the absorption liquid after absorption is lowered by mixing with the culture fluid before distillation in the first distillation column. It can prevent. Therefore, the burden of distillation or separation and regeneration in the second distillation column can be reduced, and purification efficiency or separation efficiency can be secured. And a part of the bottoms of the second distillation column can be reused as an absorbing liquid by returning a portion of the bottoms of the second distillation column from the regeneration return path to the absorbing part.

And a post absorption liquid tank for storing the absorption liquid after absorption,
Preferably, the regeneration path extends from the post-absorption fluid tank to the purification section.
Even if the concentration of the hydrocarbon compound in the absorbing solution after absorption fluctuates due to fluctuations in the partial pressure of the hydrocarbon compound in the raw material gas, carbonization is performed by storing the absorbing solution after absorption in the liquid tank after absorption The hydrogen compound concentration can be averaged and stabilized at a concentration sufficiently lower than the peak concentration. Therefore, it is not necessary to match the processing capacity of the purification section, that is, the separation and regeneration section at the peak time, and enlargement of equipment can be avoided.

It is preferable that the absorbing solution is a mixture of ethanol and water.
A solution in which a hydrocarbon compound such as benzene is absorbed in a mixture of ethanol and water is more effective in separating ethanol and a hydrocarbon compound at an azeotropic point than a solution in which a hydrocarbon compound such as benzene is absorbed in 100% ethanol. Can be raised. Therefore, the separation efficiency of the hydrocarbon compound in the separation and regeneration process (separation and regeneration unit) can be increased. It is desirable to set the ratio of ethanol to water in the mixture so as to ensure the desired absorption efficiency and the desired separation efficiency. If the ethanol content of the mixture is too low (if the water content is too high), the absorption efficiency of hydrocarbon compounds in the collecting part is reduced. If the ethanol content of the mixture is too high (if the water content is too low), the separation efficiency of the hydrocarbon compound in the separation and regeneration unit is reduced.

  According to the present invention, a hydrocarbon compound can be efficiently removed from a raw material gas, and ethanol can be efficiently produced.

FIG. 1 is a circuit diagram showing an ethanol synthesis apparatus according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the ethanol synthesis apparatus 1 includes a syngas generation unit 2 (raw material gas generation unit), an ethanol synthesis unit 10, a pretreatment unit 20, and an ethanol purification unit 40. Although detailed illustration is omitted, the syngas generation unit 2 is configured of a waste processing facility that processes industrial waste and the like. In other words, the ethanol synthesis device 1 is incorporated into the waste treatment system. The syngas production unit 2 is equipped with a gasification furnace. In this gasification furnace, waste is burned with high concentration oxygen gas and decomposed to a low molecular level, and finally it is mixed with syngas 2a (source gas) Become. The syngas 2a contains carbon dioxide (CO ₂ ) and nitrogen (N ₂ ) as main components in addition to carbon monoxide (CO) and hydrogen (H ₂ ). Furthermore, syngas 2a at the time of formation (before the absorption step) is a trace or small amount (mol-ppm order to several mol% order) of hydrogen sulfide (H ₂ S), oxygen (O ₂ ), BET X (benzene, ethyl benzene) May contain a hydrocarbon compound including an aromatic compound such as toluene, xylene).

The ethanol synthesis unit 10 includes a culture tank 11 and a culture stock solution supply unit 12. The culture solution 8 is stored in the culture tank 11. Anaerobic microorganisms 19 are cultured in the culture solution 8. As the anaerobic microorganism 19, for example, anaerobic bacteria disclosed in Patent Documents 1 and 3 (Japanese Patent Application Laid-Open Nos. 2004-504058 and 2014-050406) can be used. The anaerobic microorganism 19 synthesizes ethanol (C ₂ H ₅ OH) or the like from carbon monoxide (CO), hydrogen (H ₂ ) or the like by its fermentative action.

  The culture stock solution supply unit 12 is connected to the culture tank 11. The culture stock solution supply unit 12 supplies the stock solution of the culture solution 8 before the anaerobic microorganism 19 is put into the culture tank 11. The stock solution of the culture solution 8 mainly contains water, and various nutrient components for the anaerobic microorganism 19 are dissolved in the water.

A pretreatment unit 20 is provided between the syngas generation unit 2 and the ethanol synthesis unit 10. The pretreatment unit 20 includes a desulfurization unit 21, a deoxygenation unit 22, and a BETX absorption unit 23. The desulfurization unit 21, the deoxygenation unit 22, and the BETX absorption unit 23 are connected in series in this order from the side (upstream side) of the syngas generation unit 2. The desulfurizing unit 21 contains a desulfurizing agent such as Fe ₂ O ₃ or the like. Deoxygenation part 22 contains transition metal catalysts, such as Cu.

  The BET X absorber 23 includes an absorber 30, a pre-absorption liquid tank 31, and a post-absorption liquid tank 32. In the pre-absorption liquid tank 31, the absorption liquid 3a before the absorption step described later is stored.

  The absorber 30 is a cylindrical container extending vertically (up and down). At the upper end in the absorber 30, a liquid dispenser 33 is disposed. A pre-absorption fluid path 34 extends from the pre-absorption fluid tank 31 and is connected to the liquid dispenser 33. At the bottom of the absorber 30, the temporary storage absorbent 3b after the absorption step is stored.

  A pre-absorption gas path 24 extends from the deoxygenation section 22 and is connected to the bottom of the absorber 3. The connection portion of the absorber 30 to the pre-absorption gas path 24 is preferably disposed above the liquid surface of the temporary storage absorbent 3 b. Further, after absorption, the gas passage 25 extends from the upper side of the absorber 30 and is connected to the bottom of the culture tank 11.

The temperature in the absorber 30 is preferably a normal temperature (for example, about 10 ° C. to 40 ° C.). The lower the temperature, the easier BEXT is absorbed.
The internal pressure of the absorber 30 is preferably higher than atmospheric pressure, more preferably 5 atmospheres (gauge pressure) or more, more preferably 10 atmospheres or more, but is not limited thereto, and may be atmospheric pressure or atmospheric pressure or less. .

A post-absorption fluid path 35 extends from the bottom of the absorber 30 and is connected to the post-absorption fluid tank 32. The post-absorption storage liquid 3c (the absorption liquid after the absorption step) is stored in the post-absorption liquid tank 32. The internal volume of the absorbing solution after tank 32 depends on the processing capacity of ethanol synthesizer 1, for example ^{1 m} 3 through 10m ³ mm, preferably 2m ³ approximately.

Absorbent liquids 3a, 3b and 3c are liquid mixtures containing ethanol (C ₂ H ₅ OH) and water (H ₂ O). The ethanol concentration of the absorbents 3a, 3b, 3c is, for example, about 50 wt% to about 95 wt%. Most of the components other than ethanol in the absorbing liquids 3a, 3b and 3c are occupied by water. If the ethanol content of the absorbent 3a is too low (if the amount of water is too large), the BETX absorption efficiency is reduced. If the ethanol content of the absorbing liquid 3c is too high (if the amount of water is too small), the separation efficiency of BETX in the separation and regeneration process described later is reduced.

Furthermore, the absorbents 3b and 3c contain BETX. The BETX concentration of the temporary storage absorbent 3b fluctuates, for example, in the range of ppm order to several% order. The BETX concentration of the post-absorption storage liquid 3c is stable at a concentration sufficiently lower than the peak value of the BETX concentration of the temporary storage absorption liquid 3b.
In addition, the absorption liquid 3a before absorption may contain a very small amount of BETX. The BETX allowable concentration of the absorbing liquid 3a is sufficiently smaller than the BETX concentration of the absorbed liquid 3c, for example, several tens mol-ppm or less is desirable.

An ethanol purification unit 40 is disposed downstream of the ethanol synthesis unit 10.
The ethanol purification unit 40 includes distillation columns 41, 42,... Of a plurality of stages (only two stages are shown in FIG. 1). These distillation columns 41, 42... Are sequentially connected in series. Each distillation column 41, 42... Extends vertically.

  A post-culture solution channel 14 is drawn out from the culture solution 8 of the culture tank 11, and the post-culture solution channel 14 is connected to the middle portion of the first distillation column 41 of the first stage. At the lower end of the first distillation column 41, a first reboiler 44 is provided, and a water treatment unit 4 (waste water treatment) is connected.

  At the upper end of the first distillation column 41, a first condenser 43 is provided. A primary condensate path 47 extends from the first condenser 43 and is connected to the middle part of the second distillation column 42 at the second stage (rear stage).

  On the other hand, the regeneration path 36 is drawn out from the post-absorption liquid tank 32 and extends to the purification unit 40. The regeneration path 36 merges with the primary condensate path 47 at the merging portion 47c. Therefore, the regeneration forward path 36 is connected to the second distillation column 42 via the primary condensate path 47 downstream of the merging portion 47 c.

  At the upper end of the second distillation column 42, a second condenser 45 is provided. A secondary condensate line 49 extends from the second condenser 45.

  At the lower end of the second distillation column 42, a second reboiler 46 is provided. In addition, a secondary bottoms discharge passage 48 extends from the lower end portion of the second distillation column 42 and is connected to a third distillation column (not shown). A regeneration return path 37 branches off from the secondary bottom outlet flow path 48. The regeneration return path 37 extends to the absorbing portion 23 and is connected to the pre-absorption liquid tank 31.

A method of synthesizing ethanol by the above-mentioned ethanol synthesis apparatus 1 will be described.
<Source gas generation process>
The waste is burned in the syngas generation unit 2 to generate syngas 2a. The BETX concentration in the syngas 2a at the time of production (before the absorption step) largely fluctuates depending on the waste component of the raw material.

<Pretreatment process>
Prior to introducing the syngas 2 a into the culture tank 11, the syngas 2 a is subjected to a pretreatment step by the pretreatment unit 20. The pretreatment step includes a desulfurization step, a deoxygenation step, and a BETX absorption step.
<Desulfurization process>
Specifically, first, in the desulfurization unit 21, H ₂ S in the syngas 2 a is absorbed by a desulfurization agent such as Fe ₂ O ₃ and removed.
<Deoxidation process>
Next, in the deoxygenation unit 22, O ₂ in the syngas 2a is reacted with another gas (CO, H ₂ or the like) in the syngas 2a and removed using a transition metal catalyst such as Cu. By removing H ₂ S in advance by the desulfurization unit 21, it is possible to prevent the Cu catalyst of the deoxygenation unit 22 from being damaged.

<Absorption process>
Next, the BET X in the syngas 2 a is absorbed by ethanol and removed in the BET X absorbing unit 23.
Specifically, the syngas 2 a from the deoxygenation unit 22 is introduced into the absorber 30 through the pre-absorption gas path 24 and ascends in the absorber 30.
Further, the absorbent 3 a of the pre-absorptive liquid tank 31 is introduced into the liquid dispenser 33 through the pre-absorption liquid channel 34, and is dropped from the liquid dispenser 33 into the absorber 30 and dropped.
As a result, in the absorber 30, the syngas 2a and the absorbing liquid 3a contact each other while forming a counterflow, and the BETX in the syngas 2a is absorbed by the absorbing liquid 3a.
Since the absorption capacity of ethanol to BETX is 1,000 times or more that of water, the required flow rate of the absorbent 3a can be significantly reduced as compared to the case where 100% of water is used as the BETX absorbent. By increasing the pressure in the absorber 30, the BETX partial pressure of the syngas 2a can be increased, and the BETX absorption rate of the absorbent 3a can be increased.
Prior to this absorption step, by removing O ₂ in the deoxygenation part 22 in advance, it is possible to prevent the ethanol of the absorbing solution 3 a from reacting with O ₂ to generate unnecessary components such as formic acid.

The BETX concentration of the post-absorption syngas 2b at the top of the absorber 30 is lower than the BETX concentration of the pre-absorption syngas 2a. Further, in the absorber 30, a part of ethanol in the absorbing liquid 3a is vaporized. Therefore, the post-absorption syngas 2b contains ethanol.
The initial temperature (the temperature at the time of introduction into the absorber 30) of the syngas 2a is, for example, about 30 ° C. to 50 ° C., preferably about 40 ° C., at a temperature higher than normal temperature. By removing the heat of vaporization of ethanol from the syngas 2a, the temperature in the absorber 30 is maintained at about normal temperature (for example, about 25 ° C.).

At the bottom of the absorber 30, the temporary storage absorbent 3b that has absorbed BETX is temporarily stored. The BETX concentration of the temporary storage absorbent 3b is approximately in equilibrium with the BETX partial pressure of the syngas 2a at the bottom of the absorber 30.
Since the BETX partial pressure of the syngas 2a is likely to fluctuate according to the waste components burned in the syngas generation unit 2, the BETX concentration of the temporary storage absorbent 3b is also likely to fluctuate.

<Storage process>
The temporary storage absorption liquid 3b is sent to the post-absorption liquid tank 32 through the post-absorption liquid path 35, and is stored in the post-absorption liquid tank 32 as the post-absorption storage liquid 3c.
Even if the BETX concentration of the temporary storage absorbent 3b fluctuates with the fluctuation of the BETX partial pressure of the syngas 2a, the BETX concentration can be averaged by the storage in the post-absorption liquid tank 32. As a result, the BETX concentration of the post-absorption storage liquid 3c can be stabilized at a concentration sufficiently lower than the peak value of the BETX concentration of the temporary storage absorption liquid 3b. Therefore, in the separation and regeneration process described later, when BETX is separated from the absorbed liquid 3c and the absorbent 3a is regenerated, it is not necessary to adjust the separation and regeneration processing capacity of the separation and regeneration unit 42 to the above peak value. The burden of 42 can be reduced, and enlargement of the equipment can be avoided.
A stirrer may be provided in the post-absorption liquid tank 32 to stir the post-absorption storage liquid 3c, thereby promoting equalization of the BETX concentration of the post-absorption storage liquid 3c.

<Synthesis process>
The syngas 2 b after the absorption step is introduced into the culture tank 11 through the gas path 25 after absorption, and dissolved in the culture solution 8. Then, the anaerobic microorganism 19 in the culture solution 8 performs fermentation to synthesize ethanol from CO, H _{2 and the} like in the syngas 2 b. By introducing the syngas 2b that has undergone BETX absorption and removal into the culture tank 11, it is possible to prevent an adverse effect on the anaerobic microorganism 19, and it is possible to reliably carry out the fermentation production of ethanol.

  At this time, ethanol in syngas 2 b is also dissolved in the culture solution 8. That is, even if ethanol is vaporized from the absorbing solution 3a in the absorption step, the ethanol can be combined with the ethanol generated in the ethanol synthesis unit 10. Then, ethanol can be recovered by the purification step described later. Therefore, the waste of ethanol can be suppressed. In addition, by suppressing the vaporization flow rate of ethanol in the absorption step to, for example, about 1/10 of the flow rate of ethanol production by the anaerobic microorganism 19, it is possible to prevent the fermentation activity of the anaerobic microorganism 19 from decreasing.

<Gas release process>
The gas in the culture tank 11 is released from the gas release passage 13. The released gas components are mainly unreacted CO and H ₂ , CO ₂ , N ₂ , and may further contain trace amounts of ethanol, BETX and the like. The released gas may be recovered and reused, or may be released after being appropriately abated.

<Culture fluid delivery process>
A portion 8 a of the culture solution 8 in the culture tank 11 is led to the post-culture solution channel 14 at a predetermined flow rate. The outlet culture solution 8a is a mixture of ethanol and water. Furthermore, the derived culture fluid 8a contains a living organism of the anaerobic microorganism 19 or a biomass such as straw, and other solid components (suspended solids). The solid component is preferably captured and collected by a filter (not shown), returned to the culture tank 11, or decomposed.

<Purification process>
After removal of the solid component, the culture broth 8a is sent to the ethanol purification unit 40 and subjected to the purification step.
Specifically, the derived culture fluid 8a is first introduced into the first distillation column 41 and distilled to be separated into the lower primary bottoms effluent 8b and the upper primary distillate vapor 9a. Most of the primary bottoms effluent 8b is water (H ₂ O). A portion of the primary bottoms effluent 8b is sent to the first reboiler 44 where it is heated and turned back to the first distillation column 41 as steam. Further, the remaining portion of the primary bottoms effluent 8b is sent to the water treatment unit 4 and subjected to aerobic treatment or the like. The primary bottoms effluent 8b after the treatment may be discarded or may be returned to the culture tank 11.

The primary distillation vapor 9 a contains relatively high concentration of ethanol gas and water that can not be separated in the first distillation column 41, that is, water vapor (H ₂ O). The primary distillation vapor 9a is sent from the upper end of the first distillation column 41 to the first condenser 43, and is cooled and condensed to form the primary condensate 9b. A portion of the primary condensate 9 b is returned to the first distillation column 41. The remaining portion of the primary condensate 9 b is sent to the second distillation column 42 through the primary condensate passage 47.

<Joining process>
At the same time, a constant flow rate of the absorbed post-absorption liquid 3c is delivered from the post-absorption liquid tank 32, passes through the regeneration forward path 36, and is mixed with the primary condensate 9b at the junction 47c. As a result, a secondary pre-distillation solution 9c consisting of a mixture of the post-absorption storage solution 3c and the primary condensate 9b is produced. The secondary distillation front end liquid 9c contains relatively high concentrations of ethanol and water, and further contains BETX and the like derived from the post absorption liquid 3c. The ethanol concentration of the mixed solution 9c can be maintained high by mixing the post-absorption storage solution 3c with high ethanol concentration with the primary condensate solution 9b with high ethanol concentration instead of mixing with the culture solution 8a with low ethanol concentration. Therefore, the burden on the purification unit 40 can be reduced, and the purification efficiency can be secured. Specifically, the required heat quantity of the reboiler 46 can be reduced.

<Separation and regeneration process>
The secondary distillation front end liquid 9c is introduced into the second distillation column 42 and is distilled to be separated into the upper secondary distillation vapor 9d and the lower secondary bottoms effluent 9e. The secondary distillation vapor 9d contains, in addition to relatively low concentration ethanol gas and water vapor, a low boiling point substance such as BETX gas derived from the absorbed liquid 3c, and methanol gas derived from the culture solution 8a. The secondary bottoms 9e is a mixture of relatively high concentration of ethanol and water, and hardly contains BETX derived from the absorbed liquid 3c. In short, BETX can be separated from the ethanol of the after-absorption stored liquid 3c by the second distillation column 42 of the ethanol purification unit 40, and the absorption capacity to BETX can be recovered to be reusable as the absorbing liquid 3a. Therefore, at least a portion (the second distillation column 42) of the ethanol purification unit 40 is provided as a separation / regeneration unit that separates BETX from the absorbed liquid 3c and regenerates the absorbent 3a. In addition, at least a part of the purification process doubles as the separation and regeneration process. Therefore, it is not necessary to separately provide a separate regeneration unit dedicated to the after-absorption reservoir liquid 3c, and it is not necessary to separately perform the separation and regeneration process separately from the purification process. As a result, it is possible to prevent large-scale equipment, to avoid an increase in equipment cost, and to simplify the treatment process.

  Furthermore, since the second distillation front end liquid 9c is a mixture of ethanol and water, and this mixture is mixed with BETX, ethanol at an azeotropic point rather than a liquid in which 100% of ethanol is mixed with BETX And BETX separation rate can be increased. Therefore, the ethanol concentration of the secondary distillation vapor 9d can be further lowered, and the BETX concentration of the secondary bottoms 9e can be further lowered.

  The secondary distillation vapor 9d is introduced into the second condenser 45 and is cooled and condensed to become the secondary condensate 9f. A portion of the secondary condensate 9f is returned to the second distillation column 42. The remaining portion of the secondary condensate 9f may be used as fuel or the like, and may be discarded after post-treatment.

  A portion of the secondary bottoms 9e is sent to the second reboiler 46 where it is heated and turned back to the second distillation column 42 as steam.

<Second stage purification process>
The other part of the secondary bottoms 9e is further distilled and purified by being sent to the third distillation column (not shown) through the secondary bottoms 48. A high concentration ethanol solution of 99 wt% or more can be obtained by distillation purification after the third stage.

<Reuse process>
The remaining portion (part) of the secondary bottoms liquid 9 e is returned to the absorbing portion 23 by the regeneration return path 37 and stored in the pre-absorption liquid tank 31. As a result, the remaining part (part) of the secondary bottoms 9e can be reused as the absorbent 3a.

According to the present apparatus 1, by making the absorbing substance that absorbs BET X and the target substance of synthesis the same substance (ethanol), it is advantageous in terms of processing process, equipment cost, etc. rather than using different substances. Become.
On the other hand, when the BETX absorber 23 by ethanol is used in a plant for synthesizing substances other than ethanol (such as butanol), ethanol is removed from the system by heating or cooling after the absorption step, or recovered Need to be added, the additional equipment is increased, and the cost is increased. When BETX is absorbed by a substance other than ethanol (for example, butanol etc.) in a plant that synthesizes ethanol, the substance other than ethanol is removed or recovered from the system by heating or cooling after the absorption step. Needs to be added, the additional equipment is increased, and the cost is increased.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention.
For example, an ethanol solution of approximately 100% may be used as the BETX absorption solution. In this case, BETX can be taken out as a mixture with ethanol by distilling the absorbed ethanol solution. The content ratio of BET X to ethanol in this mixture is about 1: 1 in molar ratio.
The syngas generation unit 2 may be a steel mill or a coal combustion unit.
The source gas is not limited to the syngas 2a containing carbon monoxide and hydrogen, and may contain only one of carbon monoxide and hydrogen, and may contain carbon dioxide and hydrogen instead of carbon monoxide. It is good (refer patent document 2 grade | etc.).
In the synthesis step, ethanol may be synthesized by contacting the source gas with a catalyst (see Patent Document 2 and the like).
The hydrocarbon compound to be separated from the source gas is not limited to BET X (benzene, ethylbenzene, toluene, xylene), and may be another aromatic compound such as naphthalene, or may be acetylene or the like.
The circuit configuration of the ethanol synthesis apparatus 1 can be modified as appropriate. For example, the regeneration path 36 may be directly connected to the second distillation column 42 without joining the primary condensate path 47.

  The present invention is applicable to, for example, an ethanol synthesis system that synthesizes ethanol from syngas produced by incineration treatment of industrial waste.

1 Ethanol Synthesizer 2a Syngas before absorption (raw gas before absorption process (before absorption))
2b Syngas after absorption (raw material gas after absorption process (after absorption))
3a Pre-absorption solution (absorption solution before absorption process (before absorption))
3b Temporary storage liquid after absorption (absorbent liquid after absorption process (after absorption))
3c Absorbed liquid after absorption (absorbed liquid after absorption process (after absorption))
8 culture solution 8a Derivation culture solution (culture solution after ethanol synthesis)
9e Secondary bottoms (bottom of second distillation column)
19 Anaerobic microorganism 10 Ethanol synthesis unit 11 Culture tank 23 BETX absorption unit (absorption unit)
25 post-absorption gas path 32 post-absorption liquid tank 36 regeneration forward path 37 regeneration return path 40 ethanol purification section (purification section)
41 1st distillation column (distillation column)
42 Second distillation column (Separation and regeneration unit, distillation column)

Claims (7)

In an ethanol synthesis method for synthesizing ethanol from a source gas,
An absorption step of bringing a hydrocarbon compound contained in the raw material gas into the absorption liquid by bringing the raw material gas before the synthesis step of ethanol into contact with the absorption liquid containing ethanol;
A separation / regeneration step of separating the hydrocarbon compound from the absorption liquid after the absorption step to make the absorption liquid reusable;
A storage step of storing the absorption liquid after the absorption step in a liquid tank after absorption,
The method according to claim 1, wherein the absorption liquid in the liquid tank after absorption is subjected to the separation and regeneration step . In the ethanol synthesis step, the source gas after the absorption step is introduced into a culture solution, and ethanol is synthesized from the source gas by fermentation of anaerobic microorganisms in the culture solution,
The method further comprises a purification step of purifying ethanol from the culture solution after the ethanol synthesis step,
The ethanol synthesis method according to claim 1, wherein at least a part of the purification step also serves as the separation and regeneration step by sending the absorption liquid after the absorption step to the purification step. The method according to claim 1 or 2 , wherein the absorbing solution is a mixture of ethanol and water. In an ethanol synthesis apparatus having an ethanol synthesis unit that synthesizes ethanol from a source gas,
An absorbing unit for bringing a hydrocarbon compound contained in the raw material gas into absorption into the absorbing solution by bringing the raw material gas before introduction into the ethanol synthesis unit into contact with an absorbing solution containing ethanol;
A separation / regeneration unit that separates the hydrocarbon compound from the absorption liquid after absorption to make the absorption liquid reusable;
And the ethanol synthesis unit has a culture vessel for culturing, in a culture solution, an anaerobic microorganism which synthesizes ethanol from the raw material gas by fermentation.
Further, an after-absorption gas path for sending the absorbed source gas to the culture tank,
A purification unit for purifying ethanol from the culture solution after the ethanol synthesis;
And d) a regeneration path for transferring the absorption liquid after absorption to the purification unit,
At least a part of the purification unit is provided as the separation and regeneration unit . The purification unit comprises a plurality of distillation towers connected in sequence;
The culture vessel is connected to the first distillation column of the first stage,
The regeneration path is connected to a second distillation column connected in a stage subsequent to the first distillation column,
5. The ethanol synthesizing apparatus according to claim 4 , further comprising a regeneration return path for returning a part of the bottoms of the second distillation column as the absorbing liquid to the absorbing section. And a post absorption liquid tank for storing the absorption liquid after absorption,
The ethanol synthesis apparatus according to claim 4 or 5 , wherein the regeneration path extends from the post-absorption liquid tank to the purification unit. The absorption liquid, ethanol synthesis apparatus according to any one of claims 4-6, characterized in that a mixture of ethanol and water.

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