FR2550550A1 - PROCESS FOR ACID-FREE HYDROLYSER OF LIGNOCELLULOSIC BIOMASS - Google Patents

Abstract

PROCESS FOR ACID-FREE HYDROLYZING LIGNOCELLULOSIC BIOMASS. PRELIMINARY HYDROLYSIS OF THE BIOMASS IS PERFORMED TO ELIMINATE HEMICELLULOSES (PENTOSES), THEN EXTRACTION UNDER HIGH PRESSURE TO SEPARATE LIGNIN, THEN MAIN HYDROLYSIS GIVING CELLULOSIS AND HEXES. FOR PRELIMINARY AND MAIN HYDROLYSES, A DISAGGREGATION AND PEPTIZATION REACTOR IS USED, ASSOCIATED WITH A MECHANICAL HOMOGENIZATION AND DISAGGREGATION EFFECT AND WITH THE ACTION OF WATER VAPOR UNDER HIGH TEMPERATURES AND PRESSURES. RAPID COOLING BY EXTENSION EVAPORATION AVOIDS SUGAR DECOMPOSITION. APPLICATION: TRANSFORMATION OF A BIOMASS, CONTAINING SAWDUST, BAGASSE OR CORN RAFLE, INTO A CONCENTRATED GLUCOSE SOLUTION THAT CAN UNDERGO ALCOHOLIC FERMENTATION.

Description

The invention relates to a process for hydrolysis, under pressures and

  high temperatures, a biomass containing cellulose, especially sawdust, bagasse, scrap or corn cobs or similar materials, biomass that has

  milled and pasted with a solvent.

  The hydrolysis of biomass containing lignocellulose under high pressure and temperature with the use of acids has been known for a long time, for example by the Scholler-Tornesch or Rheinau processes. In addition, the hydrolyzate thus obtained has a very low concentration of glucose. In addition, during the hydrolysis with acid, degradation takes place. additional glucose, so that the actual glucose yield is significantly lower than the theoretical yield A treatment of this substrate to obtain alcohol is therefore not

  not profitable, because of its low concentration and the large quantities that must be evaporated.

  The hydrolysis of lignocelluloses, with the use of a corresponding high pressure water vapor, has already been carried out in the laboratory by a few researchers without significantly improving the concentration of the final substrate. Moreover, the results of this hydrolysis without acid are were unsatisfactory, as the conditions chosen, for example insufficient mechanical breakdown, did not

  not allowed to achieve effective hydrolysis.

  The invention therefore aims to prepare, from a biomass consisting of several constituents, a substrate

  to produce ethanol profitably.

  The problem thus posed is solved by degrading the fractions of the biomass, namely hemicelluloses, into pentoses, by thinning the lignin and degrading the celluloses into hexoses, withdrawing all three fractions successively in three separate operations. and therefore in particular reaction zones by separating them from each other with water as a solvent and conveying the hexoses, in the form of a liquid substrate, into

  view of a continuation of their treatment.

  According to the invention, the fractions are first separated separately from one another. This has the advantage of avoiding the drawbacks of the known processes, since no acid is used for the hydrolysis of lignocellulose. and, in place of the acid, it is possible to work with mechanical disintegration by operating also under pressure and at correspondingly higher temperatures. The concentration of the final substrate, obtained

  during this hydrolysis, may exceed 10%.

  It must therefore be considered that the essence of the invention lies in the use of water as a solvent during the separate withdrawal of the fractions, namely pentoses, lignin and hexoses The withdrawal or withdrawal of the fractions may be perform successively

  in operative steps known per se.

  Particularly preferred process steps for separating the three fractions are the

following operations.

  The first step functions as a preliminary hydrolysis, in which the biomass is impasted with water at a concentration of from 15 to 45% solids or dry extract, with simultaneous delivery of strongly compressed steam. in a disintegration-peptization reactor in which the hemicelluloses are degraded, during a reaction time of between 1 second and 10 minutes at temperatures of between 100 and 200 ° C. and at pressures between 1 and 16 bars, to give pentoses, the biomass then being relaxed, and the expanded mixture is separated with the addition of a liquid of

  washing to mechanically remove the pentose-containing substrate.

  During the preliminary hydrolysis, the biomass with water as the solvent undergoes hydrolysis under the effect of a known thermal homogenization reaction.

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  mechanical short-term, then it relaxes spontaneously so that the biomass is disintegrated, "crushed" or fragmented, pasted and dispersed under high pressure and at high temperature in a disintegration reactor peptisation This known process of homogenization- (DE- B1 922 932, DE-C-1 782 456, applications DE-A-3 127 684

  and DE-A-3 150 750) produces accelerated hydrolysis.

  The hydrolysis step therefore has the important advantage that hydrolysis can be carried out without acid, because of the high mechanical disintegration occurring in the disintegration-peptization reactor and the high temperatures and pressures applied; as a result of rapid cooling by flash evaporation, the resulting sugars can be preserved without decomposition and can be separated by the simplest means.

  the simplest means the pentoses, possibly with the addition of a washing liquid.

  In the second step, the lignin is removed by

  extraction under high pressure, so that hexoses remain.

  In the high-pressure extraction stage, the biomass, freed from pentoses, is introduced into an extraction autoclave and the solvent brought to the pressure and to the reactor is conveyed in a closed circuit in the stirred biomass. temperature required for the extraction, the lignin-laden solvent being relaxed and the lignin separating mechanically, while the remaining cellulose

  is removed from the extraction autoclave.

  Thus, the solvent is charged with lignin which, after expansion of the extracted extract phase at the top, is removed in a separator. The expanded solvent, containing lignin, then arrives at a mechanical filter, which can have the same configuration. separator, centrifuge or the like, wherein lignin is mechanically separated and removed Separated solvent

  can be recycled in the circuit or recycling loop.

  The extraction autoclave operates at

  between 100 and 300 bar, at a temperature between 50 and 200 G, and the duration of the extraction oscillates between 1/2 hour and 3 hours is circulated in recycling circuit or closed circuit in the autoclave of extraction 2 to 10 kg of solvent per hour of extraction time and

per kilogram of biomass.

  The extraction autoclave may be provided with corresponding solids retainers for continuous operation of the entire high pressure extraction. If the solids retainers are not sufficient for continuous operation, the solids can be processed continuously. discontinuously the biomass inside the extraction autoclave, that is to say that the biomass is introduced into the extraction autoclave, this apparatus is closed, then it is conveyed and circulated in circuit

closed the solvent in the autoclave.

  To enable the continuous operation of the entire process, the biomass from the preliminary hydrolysis step, and removed from the hemicellulose, can be introduced into a reservoir of this type.

  biomass feeds the extraction step under high pressure.

  Likewise, the extraction autoclave may be followed by a reservoir in which the cellulose is collected and from where

  it is sent to the main hydrolysis.

  Instead of the reservoir or reservoirs, it is also possible to provide several extraction autoclaves that a common conduit feeds biomass and another common conduit feeds solvent Thus, to maintain an almost continuous overall operation, the cellulose can, according to

  needs, be removed from one of the autoclaves and routed to the main hydrolysis step.

  It has been found, however, that extraction of the lignin from the biomass with water as the solvent is sufficient. However, it has been found that the extraction can be improved by using alcohols as the solvent. ,

  ethers, esters or alkanes or mixtures thereof.

  As a particularly advantageous mixture of solvents, a mixture of water and ethanol comprising 20

at 80% ethanol.

  The third step functions as the main hydrolysis in which the biomass, free of pentoses and lignin and consisting to a large extent of cellulose, is hydrolysed in a main thermal / mechanical reaction. The product obtained is removed from this step under In this step, the celluloses are again impregnated with water to a concentration of 15 to 45% solids and with simultaneous delivery of water vapor under high pressure. pressure, the paste is sent to a known disintegration-peptization reactor, in which, in a reaction time of between 1 second and 10 minutes at temperatures ranging between 210 and 350 ° C. and at pressures between 20 and 190 ° C. bars it happens

  a degradation giving hexoses, then there is relaxation.

  The expanded mixture is removed as a substrate containing hexoses.

  Thus, in the third step, a substrate strongly concentrated in hexoses is obtained, obtained in a manner that is favorable to the environment and that can be converted into ethanol in an economical manner into energy. of the operating parameters that are the temperature and the pressure, this step involves a further mechanical disintegration with respect to that of the preliminary hydrolysis and which takes place inside the known high-frequency disintegration-peptization reactor ( which has the same constructional characteristics as the disintegration-peptization reactor used in the first preliminary hydrolysis step). It has been found that dispersion in a high frequency mechanical field significantly accelerates the chemical reactions. reactor or dispersing apparatus and peptization is to cause in the product, during the passage of this it by the fixed and rotating flow channels, waves of

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  compression and decompression as well as shear forces and shock forces on the edges or edges Finally, it still results in the product a microcavitation set and desired The physical forces described above result in: an opening and a spontaneous bursting of the cells; a clear increase of the specific surface and therefore an acceleration of the reactions a uniform wetting of the solids by the liquids; an acceleration of the diffusion of the solvent in the cellulose crystals; and

  the possibility of dissociating (disintegrating) the cellulosic fibers.

  The apparatus or reactor of disintegration and peptization is constructed so as to allow the realization within it of the hydrolysis of cellulose, carried out under the effect of the simultaneous application of a high pressure and a high temperature. In the third step, the pressures and temperatures can be raised before the degradation of the glucose occurs. After completion of the hydrolysis, the temperature is again immediately lowered by expansion evaporation at the outlet of the process. the device, so that no further glucose degradation occurs.

  glucose is the final product of hydrolysis.

  The effects occurring in the preliminary hydrolysis step and the main hydrolysis step are of the same kind, regardless of the different temperature and pressure conditions. For cost-effective ethanol production, it is advantageous to maintain all parameters in the three stages, preliminary hydrolysis, high pressure extraction and main hydrolysis. In the preliminary hydrolysis, the reaction time can be lengthened by operating the disintegration-peptization reactor with a reaction loop.

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  For this purpose, a simple binass duct having the corresponding valves or valves is provided for this purpose.

  to convey in closed circuit the material to be treated.

  In the main hydrolysis, it is also possible to modify the reaction time by operating the disintegration-peptization reactor with a reaction or recycling loop. In this case, a simple bypass duct with the corresponding valves or valves is also provided. can achieve another elongation or shortening of the reaction time during the main hydrolysis, placing after the disintegration-peptization reactor, a screw reactor which can also be provided with an airlock with each time a conduit bypass or bypass The material leaving the disintegration-peptization reactor of the main hydrolysis can be conveyed into the screw reactor and, bypassing the airlock, be sent to an expansion vessel Treatment in the screw reactor On the contrary, the reaction time must be shortened, the material leaving the Disintegration-peptization reactor is conveyed, bypassing the screw reactor, in the airlock and arrives from there in the expansion vessel. The mode of action of the disintegration reactor also allows, after the main hydrolysis

  proper, to carry out an enzymatic post-hydrolysis.

  the thermal and mechanical treatment of celluloses, according to the process of the invention, is a good prerequisite for the enzymatic post-hydrolysis following this process

  The yields of cellulose hydrolyzate are thus increased.

  In this case, the material leaving the main hydrolysis and passing through an expansion vessel is cooled in a heat exchanger and the post-hydrolysis is carried out, in a reaction time of between 4 and 10 hours, in a tank of reaction comprising a reaction or recycling loop In the post-hydrolysis, a

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  disintegration-peptization reactor, also known per se and as a reaction accelerator, in which, using known enzymes, the material is treated at a temperature of between 40 and 120 ° C. under a pressure of 1 to 10 bar 1 to 5 seconds per pass. If new applicable enzymes are found, the pressures and temperatures required for the reaction should be adjusted to match these new enzymes. The enzyme is introduced into the reaction or recycle loop In this case, the substrate containing hexoses, and which is to be treated to obtain ethanol,

  is removed from the reaction vessel of the post-hydrolysis.

  The course of the process of the invention will now be described in more detail, by way of illustration and in no way limiting, with reference to the appended diagrammatic drawings in which: FIG. 1 shows the preliminary hydrolysis; Figure 2 shows the extraction under high pressure; Figure 3 shows another form of high pressure extraction; Figure 4 shows the main hydrolysis, and

  Figure 5 shows the enzymatic post-hydrolysis.

  The biomass containing lignocellulose, for example sawdust, corn husk or bagasse waste, is introduced via a pipe 1 into a suitable apparatus 2 in which it is subjected to mechanical pre-fragmentation. in order to obtain particles whose sizes are between 0.5 and 4 mm The prefragmented biomass arrives, for the purpose of preliminary hydrolysis, through a pipe 3 in a mashing tank in which a pipe 4 is introduced through a pipe solvent, advantageously water Through a transport member 7 and a conduit 8, the biomass reaches a disaggregation-peptization reactor 9, in which, by injecting water vapor through a conduit 10, the temperature and pressure conditions necessary for the hydrolytic-optimal degradation of hemicelluloses The temperatures are between 100 and 200 C and the corresponding pressures between 1 and 16 bar A valve 13 ret The apparatus 9 or disintegration and peptization reactor may comprise a recirculation reaction circuit or loop 11, which makes it possible to vary the reaction times. The biomass thus treated leaves the disintegrating and peptizing apparatus or reactor 9 via line 12, valve 13 and line 14, and this biomass arrives in an expansion vessel which may be, for example, a cyclone of relaxation. resulting from the preliminary hydrolysis are then conveyed via a conduit 16 to a separator 17 in which wash water is introduced via a conduit 18 The separated substrate, containing pentoses, is withdrawn via a conduit 19

  the preliminary hydrolysis leaves, via a line 20, the preliminary hydrolysis step.

  In a second subsequent separation step, the high pressure extraction is separated by

cellulose lignin.

  For the high pressure extraction, the biomass which has undergone preliminary hydrolysis is introduced via the conduit 20, and by a pump 21 and a conduit 22 having a valve 23, in an autoclave 36 at 81 o'clock extraction After filling of the autoclave 36 by the biomass and closure of the apparatus, the solvent brought to the temperature and pressure necessary for the extraction is conveyed therein for passing it into the biomass subjected to stirring. from a solvent container 24 and is introduced through a conduit 25 and a valve or valve 26 at the base of the autoclave 36. A compressor 27 and two heat exchangers 28 and 28 'associated with the conduct 25 provide the corresponding values of the temperature and pressure required for extraction Inside the autoclave 36, the solvent is loaded with lignin This extraction phase comes out in head and borrows a conduit 27 provided with a valve or valve 28 to reach a heat exchanger 29 5, then through a conduit 30, in a separator 31 The extract phase undergoes a relaxation, which allows to convey the expanded mixture through a conduit 32, having a valve or valve 33, to a filter 34

  The lignin separated therefrom is removed by a conduit 10 and the separated solvent is recycled to the container 24.

  The cellulose extracted from the biomass is removed via a conduit 38 having a valve or valve 37. When correspondingly provided, but not shown, solids containment devices are used, the step can be operated continuously. extraction process under high pressure, which means that the biomass conveyed and introduced at 20 is removed, in the form of cellulose, in the same ratio in 38 If it is not possible to implement a continuous operation, it is necessary to In a batch process, the extraction under high pressure is carried out inside the extraction autoclave 36. That is to say that the autoclave 36 is filled, closed and the solvent circulated after the autoclave 36. At the corresponding extraction time, the valves 23, 26 and 28 are closed and the valve 37 is opened to withdraw the cellulose. When the substrate is withdrawn, the discontinuous device is put into operation again. The entire system is to be provided in a quasi-continuous manner. Within tanks 20 and 38 (or served by conduits 20 and 38) there are also reservoirs which are not shown. Instead of reservoirs, provision can also be made for the presence of several autoclaves 36a, 36b and 36c, for example, extraction (see Figure 3) In this case, it operates the autoclaves so that one of them is always ready for a racking in order to always be able to extract cellulolse from one of the ducts 38 a,

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  38 b and 38 c to maintain operation in the continuous assembly For the rest, the details shown in Figure 3 correspond to those shown in Figure 2 and the elements are simply provided with index letters. The prehydrolysed biomass, freed from hemicellulose and lignin, is introduced via a conduit 38 into a mash-kneading container 39 for the main hydrolysis, and is supplemented with a solvent 10 from the conduit 40. pulp or suspension is conveyed by conduits 41 and 43, as well as by a transport member 42, through an inlet lock 44 and a conduit 45, in a reactor 46 of disintegration-peptization under high pressure The reactor 46 is constructed so as to achieve temperatures between 210 and 350 C and pressures between 20 and 190 bar. A duct 47 introduces high water vapor.

pressure in the reactor 46.

  The reactor 46 may also include a reaction or recycling loop 48 for recycling a reactor.

part of the biomass.

  In the case of biomasses requiring an even longer reaction time, it is then possible to carry out additional treatment in a reactor with

  screw arranged downstream and which is fed by a conduit 49.

  For this purpose, it is possible to group the disaggregation and peptization reactor 46 and the screw reactor 50 in a single assembly comprising a common housing. The extended reaction times can be varied between 1 second and 10 minutes. An outlet lock 53 allows the treated product to leave the pressurized zone and to enter into an expansion vessel 53. The resulting hydrolyzate exits as a substrate containing cellulose (or hexoses) and this hydrolyzate is conveyed by a duct 57 to other transformation processes A duct 55 makes it possible to bypass the airlock 53 The ducts 51 and 54 serve to ensure

the link.

  Figure 5 shows another embodiment

of the main hydrolysis.

  This embodiment is used when the cellulosic-containing substrate is not fully converted to glucose. The hydrolysed cellulosic substrate is withdrawn downstream of the vessel or vessel 56 and is conveyed via a conduit 57. to a heat exchanger 58 The product is cooled there up to

   C., which is the optimum temperature for a subsequent enzymatic post-hydrolysis reaction.

  The product is conveyed via a line 59 into a reaction vessel, or reactor 60, which is associated with a disintegration and peptization reactor 61 comprising a loop or an additional reaction and recycling circuit 62. The enzymes required for posthydrolysis are introduced by a conduit 63 in the circuit or loop 62 reaction, before the reactor 61 After completion of the reaction after 4 to 10 hours,

  separates from the remainder of the biomass the substrate solution containing the hexoses and is withdrawn via line 64.

  To accelerate the enzymatic reaction in the reactor 61, the biomass substrate is circulated, in the presence of a suitable enzyme, in the turbulence field of a homogenization machine known per se, which consists of a casing surrounding a truncated cone-shaped rotor whose circumferential surface is provided with coaxial rings of stepped diameters each located in the recesses or gaps between like rings attached to the inner wall of the casing of the housing facing the rotor, a low amount of enzyme is also introduced into the field of turbulence The substrate with

  the enzyme travels at least once the homogenization apparatus undergoing an intimate mixing.

  It goes without saying that, without departing from the scope of the invention, many modifications may be made

  the method, described and shown, of hydrolysis of a biomass containing ligno-cellulose.

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Claims (15)

  Process for the hydrolysis under high pressures and temperatures of biomass containing lignocellulose, especially sawdust, bagasse, corn husks or maize cobs or the like biomass which has been fragmented and impasted with the aid of a solvent, characterized in that the fractions of the biomass are degraded, that is to say that hemicelluloses are degraded to pentoses, 10 fluidifies the lignin and degrades the celluloses into hexoses, the three fractions are removed successively and separately from each other in three separate stages using water as   solvent, and the hexoses are conveyed in the form of a liquid substrate to further their treatment.   Process according to Claim 1, characterized in that it is carried out in three separate reaction zones, the three steps of the process.   Process according to claim 1, characterized in that the first step acts as a preliminary hydrolysis during which the biomass is impregnated with water at a concentration of 15 to 45% of the dry substance or dry extract, with simultaneous introduction of high-pressure water vapor, in a disintegration reactor 25 in which the hemicelluloses are degraded in a reaction time of between 1 second and 10 minutes, at temperatures of between 100 and 200 ° C. under pressures between 1 and 16 bar, for   give pentoses, then the biomass is relaxed and the expanded mixture is removed to remove the pentose-containing substrate, mechanical separation with the addition of a washing liquid.   4. Process according to claim 1, characterized in that the second step is a high-pressure extraction, during which the biomass, freed from pentoses, is introduced into an autoclave for   extraction and it is routed in closed circuit in the bio- 2550-550   mass agitated solvent at the pressure and temperature necessary for extraction, then the lignin-laden solvent is expanded, then the lignin is mechanically separated and removed from the extraction autoclave the remaining cellulose. Process according to Claim 4, characterized in that the extraction autoclave is operated under   pressures between 100 and 300 bar, at a temperature between 50 and 200 G and for an extraction time between 1/2 hour and 3 hours.   6 Process according to one of claims 4 and   , characterized in that 2 to 10 kg of solvent per hour of duration are circulated in the extraction autoclave.   extraction and per kilogram of biomass.   Method according to one of Claims 4 to 6, characterized in that   Discontinue the biomass inside the extraction autoclave.   8 Process according to claim 7, characterized in that, during a batch operation, the extraction autoclave is fed from a reservoir into the biomass removed from the hemicelluloses and introduced after extraction, the remaining cellulose,   from biomass, in another reservoir.   9 Process according to claim 7, characterized in that, in the high-pressure extraction circuit, two or more extraction autoclaves supplied with biomass are operated by a common conduit and solvent by another common conduit, and in that each time an autoclave is withdrawn, the cellulose for   maintain an almost continuous overall operation.   Process according to one of Claims 4 to 9, characterized in that water is used   as a solvent during extraction under high pressure. Method according to one of Claims 4 to 9, characterized in that during   extraction under high pressure, as solvent, alcohols, ethers, esters or alkanes or mixtures thereof.   Process according to any one of Claims 4 to 11, characterized in that, during   extraction under high pressure, as a solvent, a   mixture of water and ethanol containing 20 to 80% of ethanol.   Process according to claim 1, characterized in that the third step acts as a main hydrolysis during which the remaining cellulose of the biomass is again impregnated, using water to obtain a paste comprising 45% dry extract, which is introduced, with simultaneous delivery of high pressure water vapor, in a disintegration and peptization reactor in which occurs for a reaction time of between 1 second and 10 minutes. minutes at temperatures between 210 and 350 C and under pressures between 20 and 190 bar, a degradation giving hexoses, the mass is then subjected to expansion.   14 Process according to any one of claims 1 to 13, characterized in that it operates with a reaction circuit or loop or recycling the   reactor of disintegration and peptisation during   preliminary hydrolysis, to prolong the reaction time.   Process according to any one of Claims 1 to 13, characterized in that it operates   with a reaction loop or recycling the reactor   disintegration and peptization during the main hydrolysis.   Process according to any one of Claims 1 to 13 and 15, characterized in that, after having left the reactor of disintegration and peptization of   the main hydrolysis, the biomass is subjected to post-treatment in a screw reactor.   Method according to claim 16, characterized in that a bypass duct is used which bypasses the screw reactor.   Process according to one of Claims 1 to 17, characterized in that the substrate containing   hexoses, which originate from the main hydrolysis, are cooled and subjected to further enzymatic post-hydrolysis. Process according to Claim 18, characterized in that the post-hydrolysis is carried out in a reactor   which is associated with a reaction or recycle loop, during a reaction time of between 4 and 10 hours.   Process according to Claim 19, characterized in that the reaction loop comprises a disintegration and peptization reactor serving as a reaction accelerator and which is operated at a temperature between 40 and 120 ° C under a pressure of situating   between 1 and 10 bar, for 1 to 5 seconds per pass.   Method according to one of claims 18   and 20, characterized in that the enzymes are introduced into   the reaction circuit or loop and in that the reaction temperature is adjusted according to the enzymes.