JP2013059274A - Ammonia treatment method in pretreatment of saccharification of biomass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ammonia treatment method by which ammonia can be reliably absorbed and recovered.SOLUTION: In the method for diffusing ammonia from a pretreated material of saccharification containing ammonia which is obtained from a substrate mixture in a reaction container 2, allowing ammonia water in an ammonia absorbing tower 3 to absorb ammonia for recovery, the ammonia water in the ammonia absorbing tower 3 is diluted with water when the concentration of the ammonia water in the ammonia absorbing tower 3 reaches a value preventing absorption of ammonia. When the fluid volume of the ammonia water exceeds a reception amount limit, the ammonia water is transferred to the outside of the ammonia absorbing tower 3 and is reserved. When the diffusion of ammonia is started, the ammonia water reserved outside is flowed back to the ammonia absorbing tower 3 so that the capacity of the ammonia water to absorb ammonia may be maintained.

Description

  The present invention relates to an ammonia treatment method in biomass saccharification pretreatment.

  In recent years, it is known that cellulose contained in lignocellulosic biomass is saccharified using a saccharifying enzyme, and the resulting glucose is fermented to obtain ethanol.

  However, in the lignocellulosic biomass, since cellulose and hemicellulose are usually firmly bound to lignin, it is difficult to perform an enzymatic saccharification reaction on the cellulose as it is. Therefore, when the cellulose is subjected to an enzymatic saccharification reaction, the lignocellulosic biomass is pretreated for saccharification in advance so that the enzymatic saccharification reaction is possible.

  As the saccharification pretreatment, a method is known in which lignocellulosic biomass as a substrate and aqueous ammonia are mixed to form a substrate mixture, and an ammonia-containing saccharification pretreatment product is obtained from the substrate mixture. The ammonia-containing saccharification pretreatment product is pretreated so that the lignocellulosic biomass as the substrate can undergo an enzymatic saccharification reaction, but has a high pH because it contains ammonia. It cannot be served.

  Then, next, ammonia is diffused and separated from the ammonia-containing saccharification pretreatment product. As a result, an ammonia separated saccharification pretreatment product from which ammonia has been separated can be obtained, and the ammonia separation saccharification pretreatment product can be subjected to an enzymatic saccharification reaction.

  On the other hand, the diffused ammonia can be dissolved in water, recovered as ammonia water, and reused as a raw material of ammonia water mixed with the substrate.

  Conventionally, as an ammonia treatment method, a method is known in which ammonia separated from the ammonia-containing saccharification pretreated product is absorbed by water contained in an ammonia absorption tower and recovered (see, for example, Patent Document 1).

JP 2010-142680 A

  However, when the release of ammonia from the ammonia-containing saccharification pretreatment product is started, a high concentration and a large amount of ammonia are temporarily released. In such a case, the conventional ammonia treatment method has a disadvantage that the concentration of the ammonia water in which the ammonia has absorbed ammonia in the ammonia absorption tower temporarily increases, which may result in a value that hinders the absorption of ammonia. There is.

  An object of the present invention is to provide an ammonia treatment method capable of eliminating such inconvenience and reliably absorbing and recovering ammonia even if a large amount of ammonia is diffused.

  In order to achieve such an object, the present invention provides a process of obtaining a substrate mixture by supplying lignocellulosic biomass as a substrate and ammonia water to a reaction vessel and mixing them, and the substrate and the substrate in the reaction vessel. A step of obtaining an ammonia-containing saccharification pre-treatment product from the substrate mixture by reacting with ammonia water; and ammonia is dissipated from the ammonia-containing saccharification pre-treatment product in the reaction vessel; In the ammonia treatment method comprising the steps of guiding to an ammonia absorption tower containing water and absorbing the ammonia water contained in the ammonia absorption tower and recovering the ammonia treatment tower, the concentration of the ammonia water contained in the ammonia absorption tower Is a step of diluting the ammonia water with water when it becomes a value that prevents absorption of ammonia. A step of transferring the ammonia water to the outside of the ammonia absorption tower and storing it when the amount of ammonia water accommodated in the ammonia absorption tower is exceeded, and ammonia from the ammonia-containing saccharification pretreatment product When the emission of NO is started, the ammonia water stored outside the ammonia absorption tower is refluxed to the ammonia absorption tower, and the ammonia water accommodated in the ammonia absorption tower absorbs the ammonia to be emitted. And maintaining the ability to do.

  In the ammonia treatment method of the present invention, first, a substrate mixture is obtained by supplying and mixing lignocellulosic biomass as a substrate and ammonia water into a reaction vessel.

  Next, an ammonia-containing saccharification pretreatment product is obtained from the substrate mixture by reacting the substrate with the ammonia water in the reaction vessel. The ammonia-containing saccharification pretreatment product is pretreated so that the lignocellulosic biomass as the substrate can undergo an enzymatic saccharification reaction, but has a high pH because it contains ammonia. It cannot be served.

  Therefore, ammonia is diffused and separated from the ammonia-containing saccharification pretreatment product, and the diffused ammonia is absorbed and recovered by aqueous ammonia contained in an ammonia absorption tower. As a result, an ammonia separated saccharification pretreatment product from which ammonia has been separated can be obtained, and the ammonia separation saccharification pretreatment product can be subjected to an enzymatic saccharification reaction.

  Next, when the concentration of the ammonia water stored in the ammonia absorption tower becomes a value that prevents the ammonia from being absorbed, the ammonia water is diluted with water. By diluting the ammonia water accommodated in the ammonia absorption tower, the ammonia water can absorb a large amount of ammonia again. Can be absorbed into.

  When the amount of ammonia water stored in the ammonia absorption tower exceeds the storage limit, the ammonia water is transferred to the outside of the ammonia absorption tower and stored. By doing in this way, it can prevent that the liquid quantity of the ammonia water accommodated in the said ammonia absorption tower increases too much from the said accommodation limit amount.

  Further, when the release of ammonia from the ammonia-containing saccharification pretreatment product is started, the ammonia water stored outside the ammonia absorption tower is refluxed to the ammonia absorption tower and accommodated in the ammonia absorption tower. Aqueous ammonia is maintained to retain the ability to absorb the emitted ammonia.

  When the start of the release of ammonia, which causes a high concentration and a large amount of ammonia to be released, the ammonia water accommodated outside the ammonia absorption tower has the ability to absorb ammonia. By increasing the amount of ammonia water contained in the ammonia absorption tower, the ability to absorb the ammonia to be diffused is maintained. As a result, since the system for recovering ammonia is stable, ammonia can be reliably absorbed and recovered.

  As a result, according to the ammonia treatment method of the present invention, the ammonia absorption capacity of the ammonia absorption tower can be maintained as needed, so even if it is necessary to absorb a high concentration and a large amount of ammonia, the ammonia absorption This can be done without increasing the size of the tower.

  Moreover, in the ammonia treatment method of the present invention, the ammonia water stored outside the ammonia absorption tower is supplied to the step of obtaining the substrate mixture, whereby the recovered ammonia can be reused more efficiently. .

  Further, the ammonia water stored outside the ammonia absorption tower has a concentration of the ammonia water when the amount of ammonia water stored in the ammonia absorption tower exceeds a storage limit. After being diluted to the concentration of ammonia water supplied to the step of obtaining the above, it is transferred to the outside of the ammonia absorption tower and stored.

  By doing in this way, the ammonia water stored outside the ammonia absorption tower can be supplied to the step of obtaining the substrate mixture without additional concentration adjustment.

  Moreover, in the ammonia processing method of this invention, it is preferable to cool the ammonia water accommodated in the said ammonia absorption tower. By doing in this way, the ammonia water can absorb much more ammonia by raising the solubility of the ammonia water accommodated in the ammonia absorption tower.

The system block diagram which shows the apparatus structure which implements the ammonia processing method of this embodiment.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  The ammonia treatment method of this embodiment can be applied when saccharification pretreatment is performed using the pretreatment apparatus 1 shown in FIG.

  The pretreatment device 1 includes a reaction vessel 2, an ammonia absorption tower 3, and a storage tank 4.

  The reaction vessel 2 is provided with a substrate supply conduit 5 and an ammonia water supply conduit 6 at the top, and a first exhaust conduit 7 that discharges ammonia gas and guides it to the ammonia absorption tower 3. It is arranged via a bag filter 9. The substrate supply conduit 5 supplies lignocellulosic biomass as a substrate, such as rice straw, to the reaction vessel 2, and the ammonia water supply conduit 6 supplies ammonia water from the storage tank 4 to the reaction vessel 2.

  In addition, the reaction vessel 2 includes a motor 10 disposed in the upper portion, a rotating shaft 11 suspended from the motor 10 into the reaction vessel 2, and a stirring blade 12 extending from the rotating shaft 11 in the horizontal direction. At the same time, a jacket 13 through which high-temperature water as a heat medium is circulated is provided. A high temperature water conduit 14 is connected to the jacket 13, and high temperature water having a temperature in the range of, for example, 90 to 95 ° C. is supplied through the high temperature water conduit 14.

  The ammonia absorption tower 3 includes a tower main body 15 and an ammonia water tank 16 provided in communication with a lower portion of the tower main body 15. The ammonia gas guided to the ammonia water tank 16 by the first exhaust pipe 7 is converted into ammonia water. To absorb (dissolve). For this reason, the tower main body 15 is provided with a showering device 18 for showering the ammonia water supplied from the ammonia water tank 16 via the ammonia water circulation conduit 17.

  The first exhaust conduit 7 is connected to the ammonia water tank 16 through an on-off valve 19. The first exhaust conduit 7 branches off the second exhaust conduit 20 upstream of the on-off valve 19, and the second exhaust conduit 20 includes a vacuum pump 21 on the way, and joins the first exhaust conduit 7 downstream of the on-off valve 19. doing.

  The ammonia water circulation conduit 17 is connected from the ammonia water tank 16 to the showering device 18 via the circulation pump 22, the ammonia water heat exchanger 23, and the ammonia concentration sensor 24. The tower body 15 is provided with a dilution water conduit 25, and the dilution water conduit 25 is connected to a dilution water tank 27 via a water supply valve 26.

  The ammonia water tank 16 includes a liquid level sensor 28 that measures the liquid level of the ammonia water to be accommodated, and a drainage conduit 29 that discharges the ammonia water. The drainage conduit 29 is stored via a drainage pump 30. It is connected to the tank 4.

  The ammonia water heat exchanger 23 is connected to a low temperature water conduit 31 that cools the ammonia water circulated through the ammonia water circulation conduit 17. The low-temperature water conduit 31 circulates, as a heat medium, low-temperature water having a temperature in the range of, for example, 10 to 15 ° C. from the cooling chiller 32 to the ammonia water heat exchanger 23 via the low-temperature water pump 33.

  The ammonia water supply conduit 6 connected to the storage tank 4 is connected to the reaction vessel 2 via a reflux pump 34. The ammonia water supply conduit 6 branches off a reflux conduit 36 via a switching valve 35 on the downstream side of the reflux pump 34, and the reflux conduit 36 is connected to the ammonia water tank 16.

  Next, the operation of the pretreatment device 1 of this embodiment will be described.

  In the pretreatment device 1, first, the ammonia separation saccharification pretreatment product obtained in the previous treatment is discharged from the discharge port (not shown) at the bottom of the reaction vessel 2 and transferred to the next step. Thereafter, lignocellulosic biomass as a new substrate, for example, rice straw, is supplied to the reaction vessel 2 from the substrate supply conduit 5, and ammonia water is supplied to the reaction vessel 2 from the ammonia water supply conduit 6.

  At this time, in the reaction vessel 2, the rotating shaft 11 is rotationally driven by the motor 10, and the rice straw and the ammonia water are stirred by the stirring blade 12, whereby the substrate mixed solution is prepared.

  The substrate mixed solution is heated to a predetermined temperature, for example, a temperature in the range of 80 to 85 ° C. in the reaction vessel 2 by the high temperature water supplied from the high temperature water conduit 14 to the jacket 13, and the temperature in the range is Held for hours. As a result, it is possible to obtain an ammonia-containing saccharification pretreatment product in which lignin is dissociated from the substrate or the substrate is swollen so that rice straw as the substrate can be enzymatically saccharified.

  In the present embodiment, the dissociation means that at least a part of the lignin binding sites bonded to cellulose or the like is cut. Swelling means that voids are formed in cellulose or the like constituting crystalline cellulose by the ingress of liquid, or the voids are generated inside the cellulose fibers to expand.

  Next, in the pretreatment device 1, the ammonia contained in the ammonia-containing saccharification pretreated product is diffused as a gas by opening the exhaust valve 8, and ammonia water is discharged from the first exhaust conduit 7 through the bag filter 9. Guide to tank 16. At this time, the pressure in the reaction vessel 2 is higher than the atmospheric pressure, and by opening the exhaust valve 8, the ammonia gas can be easily diffused from the ammonia-containing saccharification pretreatment product.

  The ammonia gas is introduced into the ammonia water tank 16 through the first exhaust pipe 7 by opening the on-off valve 19. The pressure of the ammonia gas decreases as it is diffused, and when it becomes equal to atmospheric pressure, it becomes difficult to dissipate further. Therefore, in the pretreatment device 1, when the pressure of the ammonia gas becomes equal to the atmospheric pressure, the on-off valve 19 is closed and the vacuum pump 21 is operated to suck the ammonia in the reaction vessel 2, The water is introduced into the ammonia water tank 16 through the first exhaust pipe 7 and the second exhaust pipe 20.

  In the reaction vessel 2, the ammonia-separated saccharification pretreatment product from which ammonia has been separated can be obtained as a result of the ammonia being diffused from the ammonia-containing saccharification pretreatment product as described above.

  The ammonia separation saccharification pretreatment product is discharged from a discharge port (not shown) at the bottom of the reaction vessel 2 and transferred to the next step. Then, the next process is prepared in the reaction vessel 2.

  The ammonia treatment method of this embodiment when performing such saccharification pretreatment of lignocellulosic biomass will be described in detail below.

  First, the ammonia gas introduced into the ammonia water tank 16 of the ammonia absorption tower 3 is then introduced into the tower main body 15 communicating with the ammonia water tank 16. In the tower body 15, ammonia water circulated by the circulation pump 22 through the ammonia water circulation conduit 17 is showered by the showering device 18, thereby absorbing (dissolving) the ammonia gas in the ammonia water.

  At this time, an ammonia water heat exchanger 23 is provided in the middle of the ammonia water circulation conduit 17, and is circulated to the ammonia water circulation conduit 17 by the low-temperature water supplied from the cooling chiller 32 via the low-temperature water pump 33. The aqueous ammonia is cooled to a temperature in the range of 15 to 20 ° C., for example.

  An ammonia concentration sensor 24 is provided in the ammonia water circulation conduit 17 to detect the ammonia concentration of the ammonia water circulated through the ammonia water circulation conduit 17. When the detected ammonia concentration becomes equal to or higher than the concentration that hinders the absorption of ammonia, the water supply valve 26 is opened, and the pure water from the dilution water tank 27 to the ammonia absorption tower 3 through the dilution water conduit 25 is opened. Start supplying.

  By doing so, the ammonia water in the ammonia water tank 16 is diluted and a large amount of ammonia can be absorbed again, so even if a high concentration and a large amount of ammonia are diffused from the reaction vessel 2, Can be absorbed reliably.

  Next, when the ammonia concentration detected by the ammonia concentration sensor 24 falls to the concentration range used for the preparation of the substrate mixed solution, the water supply valve 26 is closed and pure water is supplied to the ammonia absorption tower 3. To stop.

  Next, the liquid level sensor 28 detects the amount of ammonia water. When the detected amount of the ammonia water becomes equal to or greater than the upper limit amount of accommodation of the ammonia water tank 16, until the ammonia water reaches the lower limit amount of accommodation via the drainage conduit 29 by the drainage pump 30. The ammonia water is transferred and stored in the storage tank 4.

  At this time, as described above, the ammonia concentration of the ammonia water stored in the storage tank 4 is in the concentration range used for preparing the substrate mixture in the reaction vessel 2, for example, in the range of 20 to 25%. Yes. Therefore, the ammonia water stored in the storage tank 4 is reused for the preparation of the substrate mixed solution by refluxing the ammonia water to the reaction vessel 2 through the ammonia water supply conduit 6 by the reflux pump 34. be able to.

  In addition, when the emission of ammonia from the reaction vessel 2 is started, a high concentration and a large amount of ammonia are temporarily introduced into the ammonia water tank 16. Therefore, when the amount of ammonia water detected by the liquid level sensor 28 is less than the predetermined amount set to be less than the upper limit storage amount and equal to or higher than the lower limit storage amount, the ammonia water is stored until the predetermined amount is reached. The ammonia water stored in the tank 4 is returned to the ammonia water tank 16.

  The ammonia water stored in the storage tank 4 is returned to the ammonia water tank 16 by switching the switching valve 35 and the ammonia water stored in the storage tank 4 is supplied by the reflux pump 34 through the reflux conduit 36. .

  Here, the ammonia water accommodated in the ammonia water tank 16 is obtained by transferring the ammonia water after being diluted with the pure water to the ammonia water tank 16, so that it has a sufficient ability to absorb ammonia. doing. Accordingly, by returning the ammonia water stored in the storage tank 4 to the ammonia water tank 16, the ammonia absorption tower 3 can absorb more ammonia.

  By doing so, the ammonia absorption capacity of the ammonia absorption tower 3 can be maintained as needed, so that even if it is necessary to absorb a high concentration and a large amount of ammonia, the ammonia absorption tower is enlarged. It can respond without.

DESCRIPTION OF SYMBOLS 1 ... Pretreatment apparatus, 2 ... Reaction container, 3 ... Ammonia absorption tower, 4 ... Storage tank, 15 ... Tower main body, 16 ... Ammonia water tank.

Claims (4)

Supplying a lignocellulosic biomass as a substrate to a reaction vessel and ammonia water and mixing them to obtain a substrate mixture;
Obtaining an ammonia-containing saccharification pre-treatment product from the substrate mixture by reacting the substrate with the aqueous ammonia in the reaction vessel;
Ammonia is released from the ammonia-containing saccharification pretreatment product in the reaction vessel, and the released ammonia is guided to an ammonia absorption tower containing ammonia water, and the ammonia water contained in the ammonia absorption tower is converted into ammonia water. In the ammonia treatment method comprising the step of absorbing and recovering,
Diluting the ammonia water with water when the concentration of the ammonia water contained in the ammonia absorption tower reaches a value that prevents absorption of ammonia; and
A step of transferring the ammonia water to the outside of the ammonia absorption tower and storing it when the storage capacity of the ammonia water stored in the ammonia absorption tower is exceeded;
When the release of ammonia from the ammonia-containing saccharification pretreatment product is started, the ammonia water stored outside the ammonia absorption tower is refluxed to the ammonia absorption tower, and the ammonia water stored in the ammonia absorption tower Maintaining the ability to absorb the emitted ammonia.   2. The ammonia treatment method according to claim 1, wherein ammonia water stored outside the ammonia absorption tower is supplied to the step of obtaining the substrate mixture.   3. The ammonia treatment method according to claim 2, wherein the ammonia water stored outside the ammonia absorption tower, when the amount of ammonia water stored in the ammonia absorption tower exceeds a storage limit, Ammonia treatment method characterized in that after being diluted until the concentration of ammonia water reaches the concentration of ammonia water supplied to the step of obtaining the substrate mixture, the ammonia water is transferred to the outside of the ammonia absorption tower and stored. .   The ammonia processing method according to any one of claims 1 to 3, wherein the ammonia water accommodated in the ammonia absorption tower is cooled.

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