SPECIFICATIONMethod of hydrolysinga lignocellulose-containing biomassThe invention consists of a general process for the hydrolysis at high pressures and temperatures of organic matter (biomass) with a lignocellulose content, previously crushed and mashed with a solvent agent, particularly ground wood, bagasse, corn on the cob waste or the like.
Hydrolysis of organic matter with a lignocellulose content under pressure and heat with the use of acids has been known for some time, under the name Scholler-Tornesch or Rheinau process. These already known processes operate with acids, which have a considerable pollutant effect. Besides this, the hydrolyte yields a very small quantity of glucose content. In addition, with the acid method of hydrolysis there is a further reduction of glucose, so that the actual amount of glucose that can be won is very much smaller than the theoretical amount. Processing this substrate in alcohol is uneconomic in view of the low content and large quantities of water that are consequently needed for steaming.
Hydrolysis of ligno-cellulose with the use of appropriate high-pressure steam has already been carried out by some researchers in the laboratory, but without any significant improvement in the concentration of end substrate attained. Moreover, the results of this acid-free form of hydrolysis were unsatisfactory, in that the conditions selected, e.g. inadequate mechariical treatment, were unsuitable for achieving an effective hydrolysis.
The underlying objective of the invention is the creation of a substrate from organic matter comprising a number of components by means of which ethyl alcohol can be produced economically.
This objective is attained in that the fractions of the organic matter named hemicelluloses are reduced to pentoses, lignin is liquefied and celluloses are reduced to hexoses, all three fractions being extracted separately from one another in succession in three separate steps and so in separate reaction areas with the use of water as the solvent agent, and the hexoses delivered as liquid substrate for reprocessing.
In this invention the fractions are initially extracted separately from one another. This presents the advantage that the disadvantages inherent in the processes known so far are avoided, since no acids are used for the hydrolysis of ligno-cellulose and that, instead of these, mechanical breaking-down treatment, pressure and correspondingly high temperatures can be used in the operation of hydrolysis. The concentration that can be achieved in the end substrate with the employment of this form of hydrolysis is over 10 per cent.
The nature of the invention can therefore be seen to lie in the separate extraction of the fractions, namely pentoses, lignin and hexoses, and the use of water as the solvent agent. The fractions can be extracted in succession in so-called steps in the process.
The steps for separation of the three fractions that bring particular advantages are as follows.
The first stage operates as a prehydrolysis process, that the organic matter is mashed with water to form 15 to 45% dry matter and is then directed with simultaneous feed-in of high-pressure steam into what is known as a dispersing reactor, where the hemicelluloses, in a reaction time of between 1 second and 10, minutes at temperatures of between 100 and 200"C and pressures of between 1 and 1 6 bar, are reduced to pentoses and then depressurized, the depressurized mixture then being separated with mechanical extraction of the pentose substrate with the addition of a detergent liquid.
In prehydrolysis the organic matter, treated with water as the solvent agent, is hydrolyzed through the well-known temporary thermomechanical homogenizing reaction and then spontaneously depressurized, whereby the organic matter, comminuted in the homogenizing reaction, is mashed and dispersed under high pressure and at a high temperature in the dispersing reactor (dispergator, e.g. a centrifugal apparatus). This well-known homogenizing process (DE-AS 1 9 22 932, DE-PS 1782456, DE-OS 3127684, DE-OS 31 50 750) accelerates hydrolysis.
The hydrolysis stage has the important advantage that hydrolysis, due to the high degree of mechanical breaking down provided by the dispersing reactor and the elevated temperatures and pressures, can be carried out without the use of acids, and the resulting sugar can be prevented from dissociating by being quick-cooled by means of flash evaporation. After this the pentose can be separated mechanically with the use of very simple agents, such as detergents.
In the second stage, the lignin is removed by high-pressure extraction, leaving the hexoses.
In the high-pressure extraction stage the organic matter, freed of pentoses, is fed into an extraction autoclave and the solvent circulated at the correct extraction pressure and extraction temperature through the charge of organic matter, the solvent agent charged with lignin being depressurized, the lignin being separated out mechanically and the remaining cellulose being extracted from the extraction autoclave.
The solvent agent is hereby charged with lignin, and after depressurization the extract at this phase is fronted into a separator. The depressurized solvent, together with the lignin arrives at a mechanical filter, which can bedeveloped as a separator, centrifuge or thelike, where the lignin is mechanically separated and extracted. The separated solventagent can be returned to circulation. The extraction autoclave is operated at pressuresof between 100 and 300 bar, a temperatureof between 50 and 200 C and an extraction time of between half an hour and 3 hours.
Between 2 and 10 kgs of solvent agent perhour of extraction time and per kg of organicmatter are circulated through the extraction autoclave.
The extraction autoclave can be provided with appropriate anti-solid blocking devices toenable the whole of the high-pressure extraction process to be operated on a continuousbasis. If the anti-solid blocking devices shouldnot be sufficient for continuous operating, the organic matter can be treated inside the extraction autoclave on a batch system basis, i.e. the organic matter is loaded into the autoclave, which is then closed and the solvent agent is then circulated through the autoclave.
To enable to whole process to be executed on a continuous basis, the organic matter, freed of hemicellulose, can be fed into a supply bin after the prehydrolysis stage, from which feed-in for the high-pressure extraction stage is provided. A supply bin can also be connected up to the extraction autoclave, in which the cellulose is collected and thence conveyed for the main hydrolysis process.
A number of extraction autoclaves can be provided in place of the supply bins, with admission through a common line of the organic matter and of the solvent agent through another common line. The cellulose required at any one time for maintaining virtually continuous operating is thereby extracted from one of the autoclaves and redirected for processing at the main hydrolysis stage.
It has been shown that a single extraction process for removing the lignin from the organic matter by using water as the solvent agent is sufficient. It has further been shown that extraction can be improved if alcohol, ether, ester or alkane or combinations thereof are used instead as solvent agents. A particularly advantageous solvent mix is a mix of water and ethyl alcohol with a 20 to 80% ethyl alcohol content.
The third stage operates as a main hydrolysis process whereby the organic matter, freed of pentoses and lignin and consisting largely of cellulose, is hydrolyzed by means of a main thermo-mechanical reaction and subsequently extracted as a hexose substrate. For this stage the cellulose is re-mashed with water to form 15 to 45% dry matter and, with simultaneous delivery of high-pressure steam, is then conveyed to a known type of dispersing reactor where, in a reaction time of between 1 second and 10 minutes, at temperatures of between 210 and 350it and pressures of between 20 and 1 90 bar, it isreduced to hexose and subsequently depressurized. The depressurized mixture is extracted as hexose substrate.
With the third stage, therefore, a highly concentrated hexose substrate is created thatis non-pollutant and can be processed into ethyl alcohol in a manner that is not energyintensive. This is due in particular to the fact that, besides the operating parameters of pressure and tempetature that have been mentioned, a further mechanical treatment in addition to that provided at the prehydrolysis stage is effected inside an ordinary highfrequency dispersing reactor (which displays the same design and construction features as the dispersing reactor used at the prehydrolysis stage). It has been shown that dispersingis a mechanically high-frequency field accelerates chemical reactions significantly.The effect of the dispersing reactor is that compression and decompression waves, as well as tangential and edge-impact forces, are created in the product through its passage through static and rotating ducts or tunnels. Finally a deliberate, controlled micro-cavitation occurs in the product. As a result of the abovementioned physical forces, cellules are spontaneously closed, -the specific surface is greatly increased so that reaction is accelerated, solids are uniformly wetted with liquids, -the diffusion of solvent agents in the cellulose crystals is accelerated and --cellulosefibres can be decomposed (deflaked)."l)The dispersing reactor is so designed that cellulose hydrolysis can take place in it with simultaneous application of pressure and heat.
Since no acids are used for the operation, pressures and temperatures can be raised at the third stage without causing the glucose to dissociate. On the conclusion of hydrolysis the temperature is lowered again by means of flash evaporation at the outlet from the machine, to prevent any further reduction of the glucose. Glucose is the end product of the hydrolytic process.
Actions in the prehydrolysis and main hydrolysis stages are the same, apart from the different pressure and temperature conditions.
In the interest of economy in the production of ethyl alcohol it is beneficial for all the parameters to be adhered to at all three stages, prehydrolysis, high-pressure extraction and main hydrolysis.
For the prehydrolysis stage, reaction time can be extended through operation of the dispersing reactor with the addition of a reaction loop. For this an ordinary bypass line is provided, fitted with the appropriate valve installations, to enable the product for treatment to be introducted into the cycle.
At the main hydrolysis stage reaction time can also be modified through operation of the dispersing reactor with the addition of a reaction loop.
Here too an ordinary bypass line is provided fitted with the appropriate valves. Reaction time at the main hydrolysis stage can also be further extended, or shortened, by connecting up to the dispersing reactor a screw reactor and a discharge sluice, both the screw reactor and the discharge sluice being provided with a bypass line. The product leaving the dispersing reactor, at the main hydrolysis stage, can be directed into'the screw reactor and then, bypassing the discharge sluice, into a depressuring vessel. Processing with the use of the screw reactor involves a longer reaction time.
If it is desired to shorten the reaction time, the product leaving the dispersing reactor bypasses the screw reactor and is directed into the discharge sluice and from there into the neutralization tank.
The manner in which the dispersing reactor works lends itself, after completion of the main hydrolytic process, to a process of enzymic re-hydrolysis. The thermo-mechanical treatment of cellulose used in the invented process provides suitable preconditions for subsequent enzymic re-hydrolysis. This results in a greatly increased end product from cellulose hydrolytes. In this process the product leaving the main hydrolysis stage via a neutralization tank is cooled in a heat exchanger, and re-hydrolysis is carried out in a reaction tank with a reaction loop attachment, reaction time being between 4 and 10 hours.For the re-hydrolysis process a dispersing reactor of a known type is also used, designed to serve as a reaction accelerator, which is operated with the use of known enzymes at a temperature of between 40 and 120 C and a pressure of between 1 and 10 bar for between 1 and 5 seconds per cycle. If new, usable enzymes should be found the pressures and temperatures required for reaction to take place will need to be adapted to such enzymes. The enzyme is fed into the reaction loop. In this case the hexose substrate to be processed into ethyl alcohol is taken from the re-hydrolysis reaction tank.
Flow diagrams illustrating the invented process are shown in the attached sketches. The cycle is described in detail below. The diagrams are:Figure 1 PrehydrolysisFigure 2 High-pressure extractionFigure 3 Alternative method of high-pressure extractionFigure 4 Main hydrolysis processFigure 5 Enzymic re-hydrolysis.
Ligno-cellulose matter, for example ground wood, corn on the cob waste or bagasse, is fed via a line (t) into an appropriate device (2) and precrushed in such a way that particle sizes of between 0.4 and 4 mm are achieved.
For prehydrolysis, the precrushed organic matter is conveyed via another line (3) to a mashing vat, to which a solvent agent, preferably water, is added via line (4). The matter is then conveyed by means of a conveyor (7) and line (8) to a dispersing reactor (9), in which through the injection of steam via line (10) the pressure and temperature are maintained at the correct setting required for the optimum hydrolytic reduction of the hemicelluloses. Temperatures are between 100 and 200"C, the corresponding pressures between 1 and 16 bar. A counterpressure valve (13) is provided for setting the required operating conditions. The dispersing reactor can be provided with a reaction loop (11), whereby reaction times can be varied.The organic matter, after treatment as described, leaves the dispersing reactor (9) via lines 1 2 and 1 3 and arrives at a depressurizing vessel (15), which can be, for example, a depressurizing cyclone. Additionally, the pentoses found at the prehydrolysis stage are conveyed via line (16) to a separator (17), to which detergent liquid is added via line (18). The separated pentose substrate is removed via line (19).
The prehydrolyzed organic matter leaves the prehydrolysis stage by line (20).
In a second, follow-up separation stage the lignin is separated out from the cellulose by means of a high-pressure extraction process, e.g. in a centrifugal apparatus.
In the high-pressure extraction process the prehydrolyzed organic matter is fed in via line (20) by means of a pump (21) and over line (22) with valve (23) to an extraction autoclave (36). After the autoclave (36) has been charged with the organic matter and sealed, the solvent agent is circulated through the charge of organic matter, having been brought up to the required extraction pressure and extraction temperature. The solvent agent is taken from a solvent tank (24) and conveyed over line (25) and via valve (26) to the sump area of the extraction autoclave (36). A compressor (27) with two heat exchangers (26) and (28) monitor and control the pressures and temperatures required for extraction. Inside the autoclave (36) the solvent agent becomes charged with lignin.The product at this phase of extraction is fed from the front end via line (27) and valve (28) to a heat exchanger (29) and from there via line (30) to a separator (310. Here the extract is depressurized, and the depressurized mixture can be fed via line (32) with valve (33) to filter (34).
The separated lignin is then extracted via line (35) and the separated solvent agent is conveyed back to the solvent tank (24). The cellulose extracted from the organic matter is removed via line (28) and valve (37). With the provision of appropriate anti-solid blocking devices (not illustrated) the high-pressure extraction stage can be operated on a continuous basis, in other words the organic matter fed in by line (20) is extracted in the same propor tion as cellulose via line (38). If continuous operating is not feasible, high-pressure extraction must take place inside the autoclave on the basis of batch procedure. In other words, autoclave (36) is charged, then sealed, and the solvent agent is passed through. After the lapse of the appropriate extraction time, valves (23), (26) and (28) are closed and valve (37) opened for extraction of the cellulose.Once the substrate has been extracted, batch-procedure operating is restarted. For virtually continuous operating, supply bins need to be provided (not illustrated) as part of line circuits (20) and (38). Additional autoclaves (36a) (36b) and (36c) can also be provided instead of the supply bins. In this case the autoclaves need to be operated in such a way that one of them is always ready for extraction to be effected, so that for maintaining continuous operating the cellulose can always be drawn off by one or other of the lines (38a) (38b) or (38c). Incidentally, the data given below in Fig. 3 tally with those supplied inFig. 2, and are merely given extra letter indicators.
The prehydrolyzed organic matter, freed of the hemicelluloses and lignin, is fed over line (38) into a mashing vat (39) for the main hydrolysis process, and mixed with a solvent agent introduced via line (40). The suspension is then conveyed by lines (41) and (43) and a conveyor (42) over a feed-in sluice (44) on line (45) to a high-pressure dispersing reactor, so designed that temperatures of between 210 and 350or and pressures of between 20 and 190 bar can be attained. High-pressure steam is fed into the loop (46) and over line (47).
The high-pressure dispersing reactor can also be provided with a reaction loop (46), through which part of the organic matter can be returned.
In the case of organic matter that requires a longer reaction time, supplementary treatment can also be given in a screw reactor connected up to the circuit, fed by line (49). To this end the dispersing reactor (46) and the screw reactor (50) can be constructed as a single machine unit with a common housing.
Extended reaction times can vary between 1 second and 10 minutes. A discharge sluice (53) draws off the processed product from the pressurized area into a depressurizing vessel (53). From there the hydrolyzed product in the form of cellulose substrate is conveyed via line (57) for reprocessing. (55) represents an additional line bypassing the discharge sluice. (51) and (54) are connection lines.
Fig. 5 shows an optional complementary system as part of the main hydrolytic process.
This complementary system is for use if the cellulose substrate has not yet been fully converted into glucose. The hydrolyzed cellulose substrate is drawn off behind depressurizing vessel (56) by means of line (57) and fed into a heat exchanger (58). There the product is cooled down to about 50 C, the optimal reaction temperature for enzymic re-hydrolysis. It is then conveyed via line (59) to a reaction tank (60), to which a dispersing reactor (61) and a supplementary reactor loop (62) are attached. The enzymes required for a re-hydrolysis are fed in before the dispersing reactor by line (63) to the reaction loop (62).
After reaction is completed, after between 4 to 10 hours, the glucose solution is separated out from the organic matter and drawn off over line (64).
In order to accelerate the process of enzymic reaction in reactor (61), the organic matter substrate, together with a suitable enzyme, is directed through the turbulence field of a known type of homogenizing machine, consisting of a housing inside which there is a revolving truncated cone-shaped rotor, with coaxial rings of staggered diameters mounted on the shell, themselves staggered from time to time with similar rings on the inside wall of the housing opposite the rotor, together with a small quantity of enzyme apportioned out and introduced into the turbulence field. The substrate, along with the enzyme, is conveyed at least once through the homogenizing machine, whereby it is homogenously mixed.