JPWO2009034707A1 - Cellulose biomass raw material pretreatment method - Google Patents

Abstract

Provided is a cellulosic biomass raw material pretreatment method capable of dissociating lignin from a cellulosic biomass raw material, reducing the molecular weight of hemicellulose, and reducing the crystallinity of cellulose with a small energy without using a large apparatus. The cellulosic biomass raw material and water are continuously supplied between a pair of grindstones 2 and 3 arranged facing each other at a predetermined interval, the grindstone 2 is fixed, and the grindstone 3 is rotated. The cellulosic biomass raw material is ground. The supply amount of the water is controlled so that the temperature of the cellulosic biomass raw material to be ground is in the range of 50 to 100 ° C. The water supply amount is controlled by measuring the temperature of the cellulosic biomass raw material to be ground and performing feedback control based on the temperature. The cellulosic biomass raw material is rice straw.

Description

  The present invention relates to a pretreatment method for cellulosic biomass material used for ethanol production.

  Conventionally, a technique for producing ethanol by converting cellulose obtained from a cellulosic biomass raw material into a sugar such as glucose by enzymatic saccharification and fermenting the obtained sugar is known.

  However, the cellulose has a structure in which fibrous substances are aggregated and crystallized, and further, crystallized substances aggregate to form microfibrils, and thus are not easily affected by an enzyme. In addition, since the cellulose is strongly bound to lignin and hemicellulose and forms a cell wall, the enzymatic saccharification reaction on the cellulose is inhibited as it is.

  Therefore, it is necessary to pretreat the cellulose for enzymatic saccharification, dissociate the lignin, lower the molecular weight of the hemicellulose, and reduce the crystallinity of the cellulose. As the pretreatment, steam explosion is known in which a mixture of cellulosic biomass, steam and water is exposed to a rapid pressure drop. In the steam explosion, the cellulosic biomass raw material may be mixed with a small amount of caustic alkali in advance (see, for example, Patent Document 1).

  As the pretreatment, hydrothermal treatment in which a cellulosic biomass material is treated with pressurized hot water is known (for example, see Patent Document 2).

However, since all of the conventional pretreatments use high-temperature and high-pressure steam, there is a disadvantage that a large amount of heat energy is required to obtain the steam. The heat energy can be recovered by providing a heat exchanger and a heat storage device, and energy saving is possible, but an increase in the size of the device system is inevitable.
Special table 2001-519486 JP 2006-136263 A Japanese Patent No. 3558687

  The present invention eliminates such inconveniences, dissociates lignin from cellulosic biomass raw materials with a small amount of energy without using a large apparatus, lowers the molecular weight of hemicellulose, and reduces the crystallinity of cellulose. It aims at providing the pre-processing method of the cellulosic biomass raw material which can be processed.

  In order to achieve such an object, the cellulosic biomass raw material pretreatment method of the present invention is a method for producing cellulose by saccharifying cellulose obtained from the cellulosic biomass raw material with an enzyme. The cellulosic biomass raw material and water are continuously supplied between a pair of grindstones arranged opposite to each other with a predetermined interval, and one of the grindstones is fixed. And rotating the other to grind the cellulosic biomass raw material and control the amount of water supplied so that the temperature of the cellulosic biomass raw material to be ground is in the range of 50 to 100 ° C. It is characterized by.

  In the method of the present invention, first, a cellulosic biomass raw material is continuously supplied together with a predetermined amount of water between a pair of grindstones arranged to face each other at a predetermined interval. Then, one of the grindstones is fixed and the other is rotated.

  In this way, when the cellulosic biomass raw material and water pass between the pair of grindstones, they are ground by the grindstone and simultaneously heated by Joule heat generated by the grinding. According to the heating, there is a concern that the cellulosic biomass raw material will burn, but the cellulosic biomass raw material is supplied between the pair of grindstones together with the predetermined amount of water, thus preventing the burnt. be able to.

  At this time, in the method of the present invention, the supply amount of the water is controlled by the heating so that the temperature of the cellulosic biomass raw material to be ground is in the range of 50 to 100 ° C.

  When the temperature of the cellulosic biomass raw material to be ground is within the above range, the lignin is first softened by the heating. The lignin can be dissociated to some extent only by the grinding, but the dissociation can be easily performed by receiving the grinding of the lignin softened by the heating.

  Moreover, the water supplied with the said cellulose biomass raw material and the water contained in this cellulose biomass raw material are boiled by the said heating. Since the water causes a phase change by boiling, the cellulosic biomass raw material is expanded by the phase change. The cellulosic biomass raw material is easily pulverized by being subjected to the grinding in the expanded state as described above, and the hemicellulose is removed, and the crystallinity of the obtained cellulose is reduced. Reduced.

  As a result, according to the method of the present invention, lignin is dissociated from the cellulosic biomass raw material with a small energy without using a large device, and the molecular weight of hemicellulose is reduced, and the crystallinity of cellulose is reduced. In the subsequent enzymatic saccharification, excellent saccharification efficiency can be obtained.

  When the temperature of the cellulosic biomass raw material is less than 50 ° C., the dissociation of the lignin, the molecular weight reduction of the hemicellulose, and the reduction of the crystallinity of the cellulose are all insufficient, and the relative amount of moisture is relatively high. In addition, since the substrate concentration decreases, sufficient saccharification efficiency cannot be obtained in the subsequent enzymatic saccharification.

  On the other hand, since the boiling point of water under atmospheric pressure is 100 ° C., it is difficult to make the temperature of the cellulosic biomass raw material exceed 100 ° C.

  Moreover, by maintaining the temperature of the cellulosic biomass raw material in the range of 50 to 100 ° C., the amount of heat can be used for the enzymatic saccharification in the subsequent step, and it is not necessary to heat again in the enzymatic saccharification step.

  In the method of the present invention, the water supply amount can be controlled, for example, by measuring the temperature of the cellulosic biomass raw material to be ground and performing feedback control based on the temperature. However, the water supply amount may be controlled by feedforward control based on the temperature of the cellulosic biomass raw material.

  In the method of the present invention, for example, rice straw can be used as the cellulose-based biomass raw material. When the rice straw is used as the cellulosic biomass raw material, microorganisms are present in the rice straw, and the microorganisms digest with sugar as a substrate, so that the sugar content obtained in the subsequent enzymatic saccharification is reduced. There is concern that the yield of ethanol will be reduced. However, in the method of the present invention, since the microorganisms can be killed by the heating, the sugar content can be prevented from being reduced even when the rice straw is used as the cellulosic biomass raw material.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory sectional view showing the pretreatment method of this embodiment, and FIG. 2 is a graph showing the saccharification efficiency when the cellulose obtained by the pretreatment method of this embodiment is subjected to enzymatic saccharification in the subsequent step. It is.

  In the method of this embodiment, for example, when cellulose obtained from a cellulose-based biomass material such as rice straw is saccharified with an enzyme to produce ethanol, the rice straw is pretreated.

  In the method of this embodiment, naturally dried rice straw having a water content of 6 to 10% by weight is pulverized by a cutter mill, and rice straw chips that have been passed through a screen filter having a diameter of 3 mm are used as the cellulosic biomass raw material. The chips are continuously supplied together with a predetermined amount of water to the grinding apparatus 1 shown in FIG.

  The grinding apparatus 1 shown in FIG. 1 includes a pair of disc-shaped grindstones 2 and 3 arranged opposite to each other in the vertical direction, and the upper grindstone 2 is fixed, while the lower grindstone 3 is not shown. It is rotated by a rotation driving means.

  The upper grindstone 2 includes a conical wall portion 4 having a smaller diameter in the upper part, and the conical wall portion 4 communicates with the cylindrical wall portion 5 at the upper part. Furthermore, the cylindrical wall portion 5 communicates with the raw material hopper 6 at the upper portion, and a water supply port 7 is connected to the side wall of the raw material hopper 6. The lower grindstone 3 is provided with a conical wall portion 8 having a smaller diameter toward the lower portion at a portion facing the inner conical wall portion 4, and the conical wall portion 8 is connected to the bottom surface 9 at the lowest position.

  In the grinding device 1, a space portion 10 is formed in a portion sandwiched between the conical wall portions 4 and 8 of the grindstones 2 and 3, and the grindstones 2 and 3 are ground on the outer peripheral side of the space portion 10. Surfaces 2a and 3a are provided. The grinding surfaces 2a and 3a face each other with a predetermined clearance t, and are provided with abrasive grains (not shown) having a grain size roughness number 46 # on the surfaces.

  As the grinding device 1 having the above-described configuration, for example, Super Grindell (trade name) manufactured by Masuko Sangyo Co., Ltd. can be used (see Patent Document 3).

  In the grinding apparatus 1, the rice straw chips are continuously supplied from the raw material hopper 6 while rotating the grindstone 3, and a predetermined amount of water is continuously supplied from a water supply pump (not shown) through a water supply port 7. Supplied. The rice straw chips and water supplied to the grinding device 1 flow out from the space 10 to the clearance between the grinding surfaces 2a and 3a, and are ground by the abrasive grains provided on the grinding surfaces 2a and 3a. It is discharged to the outer peripheral side of the grinding surfaces 2a, 3a.

The clearance t between the grinding surfaces 2a and 3a is set to an appropriate range, and the rice straw chips and water are heated by Joule heat generated as the rice straw chips are ground. At this time, there is a concern that the rice straw chips may be burnt by the heating, or the ground surfaces 2a and 3a may be damaged by silicon oxide (SiO ₂ ) contained in a large amount in the surface layer portion of the rice straw chips. However, since the rice straw chips are supplied to the grinding device 1 together with a predetermined amount of water as described above, it is possible to prevent the burning and the grinding surfaces 2a and 3a from being damaged.

  In the present embodiment, the amount of water supplied by the water supply pump is controlled so that the rice straw chips to be ground have a temperature in the range of 50 to 100 ° C. by heating with the Joule heat. The amount of water supplied is, for example, provided with a temperature sensor (not shown) on the outer peripheral side of the grinding surfaces 2a, 3a, and detects the temperature of the ground rice straw chips discharged from the grinding device 1, Feedback control can be performed according to the detected temperature.

  The water supply amount may be feedforward controlled using a temperature detected by the temperature sensor. According to the feedforward control, the type of cellulosic biomass material (rice straw chips in the present embodiment) and particle size are fixed, and the rotational speed of the grindstone 3 and the clearance t between the grinding surfaces 2a and 3a are set. For example, the temperature of the ground rice straw chips is almost determined by setting the amount of water supply relative to the amount of the cellulosic biomass feedstock that is stationary. Therefore, the data of the type of cellulosic biomass material, the particle size, the rotational speed of the grindstone 3, the clearance t between the grinding surfaces 2a and 3a, the steady supply amount of the cellulosic biomass material, and the water supply amount are collected as table data. By setting the initial value, the fluctuation of the water supply amount can be reduced, and the power of the water supply pump can be reduced.

  When the temperature of the rice straw chips to be ground is in the range of 50 to 100 ° C., the lignin that is firmly bonded to the cellulose of the rice straw chips is first softened by the heating. The lignin can be dissociated to some extent only by the grinding, but the lignin softened by heating is easily dissociated from the cellulose by receiving the grinding.

  Moreover, the water supplied from the feed pump and the water contained in the rice straw chips are boiled by the heating. The rice straw chip is expanded by causing a phase change of the water by boiling, and is easily pulverized by being subjected to the grinding in an expanded state. As a result, hemicellulose forming the cell wall of cellulose of the rice straw chip is removed and the crystallinity of cellulose of the rice straw chip is lowered.

  In addition, microorganisms are present in the rice straw chip, but the microorganisms can be killed by the heating. As a result, when a sugar is generated by enzymatic saccharification in the subsequent step, the sugar is not digested as a substrate of the microorganism, and a decrease in the sugar can be prevented.

  When the temperature of the rice straw chips to be ground is less than 50 ° C., dissociation of the lignin, low molecular weight of the hemicellulose, and reduction of the crystallinity of the cellulose are all insufficient, and excessive moisture As a result, the substrate concentration is relatively lowered, so that sufficient saccharification efficiency cannot be obtained in the subsequent enzymatic saccharification.

  On the other hand, since the boiling point of water under atmospheric pressure is 100 ° C., it is difficult to make the temperature of the rice straw chips exceed 100 ° C. depending on the amount of water supplied.

  Moreover, by maintaining the temperature of the ground straw chip to be ground in the range of 50 to 100 ° C., the amount of heat can be used for enzyme saccharification in the subsequent step, and it is necessary to heat it again in the enzyme saccharification step. Absent.

  Next, the amount of water supplied by the feed pump is varied in the grinding device 1, the temperature of the rice straw chips to be ground is changed, and the saccharification rate is measured when the cellulose obtained at each temperature is saccharified with an enzyme. did. The temperature of the rice straw chips to be ground is 32 ° C. (Comparative Example 1), 45 ° C. (Comparative Example 2), 55 ° C. (Example 1), 60 ° C. (Example 2), 84 ° C. (Example 3). And 100 ° C. (Example 4).

  For the saccharification by the enzyme, a cellulase (manufactured by Genencor Kyowa Co., Ltd., trade name) is used as an enzyme in an aqueous cellulose solution (substrate concentration 5% by weight) obtained by grinding the rice straw chips with the grinding device 1. GC220) was added to an enzyme concentration of 0.5% by weight, the pH was adjusted to 4.0, and the mixture was shaken and stirred at 50 ° C. for 48 hours. The saccharification rate was determined as the ratio of the amount of glucose obtained by saccharification by the enzyme to the amount of α-cellulose obtained by solid analysis of rice straw chips.

  On the other hand, as a reference example, according to the conventional hydrothermal treatment method, the enzyme obtained by treating the rice straw chips with 180 ° C. and 1 MPa water vapor for 30 minutes was used in the same manner as in each of the Examples and Comparative Examples. And saccharification rate was measured.

  The saccharification rates of the Examples and Comparative Examples are shown in FIG. 2 as saccharification efficiency where the saccharification rate of the reference example is 1. From FIG. 2, it is clear that in Examples 1 to 4 where the temperature of the rice straw chips to be ground is in the range of 50 to 100 ° C., the saccharification efficiency is almost equivalent to that of the reference example. On the other hand, in Comparative Examples 1 and 2 in the range of 32 to 45 ° C., it is clear that the saccharification efficiency is lower than that of the reference example and does not reach the conventional hydrothermal treatment method.

Explanatory sectional drawing which shows one Embodiment of the pre-processing method of this invention. The graph which shows the saccharification efficiency when the cellulose obtained by the pre-processing method of this invention is used for the enzyme saccharification of a post process.

Explanation of symbols

  1 ... grinding equipment, 2,3 ... grinding stone.

Claims (3)

In order to produce ethanol, when cellulose obtained from cellulosic biomass raw material is saccharified with an enzyme, a method for pretreating the cellulosic biomass raw material,
The cellulosic biomass raw material and water are continuously supplied between a pair of grindstones arranged opposite to each other with a predetermined interval, and one of the grindstones is fixed and the other is rotated. , Grinding the cellulosic biomass raw material,
A pretreatment method for a cellulosic biomass raw material, wherein the amount of water supplied is controlled so that the temperature of the cellulosic biomass raw material to be ground is in the range of 50 to 100 ° C.   2. The pretreatment method for a cellulosic biomass raw material according to claim 1, wherein the water supply is controlled by measuring the temperature of the cellulosic biomass raw material to be ground and performing feedback control based on the temperature.   The cellulosic biomass material pretreatment method according to claim 1 or 2, wherein the cellulosic biomass material is rice straw.

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