Method for treating lignocellulosic biomass
阅读说明：本技术 处理木质纤维素生物质的方法 (Method for treating lignocellulosic biomass ) 是由 C·艾马尔 L·佩罗塔 于 2018-12-04 设计创作，主要内容包括：本发明涉及处理木质纤维素生物质的方法,所述方法包括以下步骤：a.制备包含意在用于浸渍所述生物质的化学催化剂的浸渍液体(4)；b.经由浸渍反应器(5)的入口引入经研磨的生物质(6),所述入口位于所述浸渍反应器的第一浸渍区(5a)中,所述浸渍反应器包括两个叠置区,即所述第一浸渍区和在所述浸渍区上方的所谓的第二脱水区(5b)；c.经由位于反应器的所述第一浸渍区(5a)中的第一液体入口引入液体(4a)；d.经由位于第一浸渍区(5b)中的生物质入口下方的反应器的另一区域(5d)中的第二液体入口将所述液体(4b)引入所述反应器。本发明还涉及用于实施所述方法的装置。(The present invention relates to a method for treating lignocellulosic biomass, said method comprising the steps of: a. preparing an impregnation liquid (4) comprising a chemical catalyst intended for impregnating the biomass; b. introducing ground biomass (6) via an inlet of an impregnation reactor (5), said inlet being located in a first impregnation zone (5a) of said impregnation reactor, said impregnation reactor comprising two superposed zones, namely said first impregnation zone and a so-called second dewatering zone (5b) above said impregnation zone; c. introducing a liquid (4a) via a first liquid inlet located in said first impregnation zone (5a) of the reactor; d. the liquid (4b) is introduced into the reactor via a second liquid inlet in another region (5d) of the reactor located below the biomass inlet in the first impregnation zone (5 b). The invention also relates to a device for implementing said method.)
1. A method of treating lignocellulosic biomass (6), the method comprising the steps of:
a. preparing an impregnation liquid (4) comprising a chemical catalyst intended for impregnating the biomass, the chemical catalyst being selected from the group consisting of acid catalysts, basic catalysts and oxidation catalysts, preferably acid catalysts;
b. introducing the ground biomass via an inlet of an impregnation reactor (5), said inlet being located in a first impregnation zone (5a) of said impregnation reactor, said impregnation reactor comprising two superposed zones, namely said first impregnation zone and a second "draining" zone (5b) above said impregnation zone;
c. introducing a liquid (4) via a first liquid inlet located in said first impregnation zone (5a) of the reactor;
characterized in that the method further comprises the steps of:
d. the liquid is introduced into the reactor (5) via a second liquid inlet in another region (5d) of the reactor located below the biomass (6) inlet in the first impregnation zone (5 b).
2. The method according to the preceding claim, characterized in that the biomass (6) is transported by means of one or more conveying screws (5c) from a first impregnation zone (5a), in which the biomass is impregnated with liquid, to a second draining zone (5b), in which the biomass is drained.
3. The method as claimed in one of the preceding claims, characterized in that the biomass (6) is introduced into the first impregnation zone (5a) of the reactor by means of a feed device (6a) which produces a biomass plug (6b) which prevents a backflow of liquid from the first zone (5a) into the feed device (6a), in particular a feed screw.
4. The method as claimed in one of the preceding claims, characterized in that 80% -98%, in particular 85% -90%, of the liquid introduced into the impregnation reactor (5) is introduced via the first liquid inlet (4a) and the remainder up to 100% of the liquid introduced into the reactor is introduced via the second liquid inlet (4 b).
5. The method according to one of the preceding claims, wherein introducing liquid via the first liquid inlet (4a) and/or via the second liquid inlet (4b) is carried out continuously or discontinuously.
6. The method according to any of the preceding claims, wherein the further area (5d) of the reactor (5) where the second liquid inlet is located is an inactive zone located at the bottom of the reactor, which is placed substantially vertically or inclined with respect to the vertical.
7. Method according to one of the preceding claims, characterized in that the liquid (4) is an acidic catalytic liquid and the pH of the liquid is adjusted to 0.1-4, in particular 0.3-2.
8. Method for the continuous treatment of lignocellulosic biomass, characterized in that it comprises the steps according to one of the preceding claims and is carried out continuously or discontinuously by comprising the following steps:
e. transferring the impregnated and drained biomass from the impregnation reactor outlet (5) to a digestion pretreatment reactor (9);
f. pre-treating the biomass in the digestion reactor (9);
g. enzymatically hydrolyzing (16) the pretreated biomass (15);
h. the enzymatic hydrolysate (17) obtained from the pretreated biomass is subjected to alcoholic fermentation (18).
9. An apparatus for treating lignocellulosic biomass, comprising:
-a zone (3) equipped with a liquid outlet for preparing an impregnation liquid (4) comprising a chemical catalyst for impregnating the biomass, selected from an acid catalyst, a basic catalyst or an oxidation catalyst, preferably an acid catalyst;
-an impregnation reactor (5) comprising a first impregnation zone (5a) equipped with an inlet for biomass and a second zone (5b), called draining zone, superimposed on said first impregnation zone and equipped with an outlet for biomass;
-means (6a) for feeding the ground biomass to the impregnation reactor (5) via the biomass inlet of the reactor located in the first impregnation zone (5 a);
-feeding an impregnation liquid to a first device (4a) of the reactor (5) connecting a liquid outlet of the preparation zone (3) of the liquid (4) to a first liquid inlet in a first impregnation zone of the reactor;
characterized in that the device further comprises:
-feeding impregnation liquid to a second device (4b) of the reactor (5) connecting the liquid outlet of the liquid preparation zone (3) to a second liquid inlet in a reactor zone (5d) located below the biomass inlet of the first impregnation zone (5 a).
10. The apparatus according to the preceding claim, characterized in that the impregnation reactor (5) is vertical or oriented obliquely with respect to the vertical, the biomass being subjected to an ascending movement from the first impregnation zone (5a) to the second draining zone (5b) by means of one or more conveying screws (5c) placed in said zone in the reactor.
11. The apparatus according to claim 9 or claim 10, wherein the impregnation liquid preparation zone is a tank (3) or a static mixer or a dynamic mixer.
12. The apparatus according to any one of claims 9 to 11, wherein the first liquid feeding means and the second liquid feeding means comprise a common line section (4) connected to the same liquid outlet of the liquid preparation zone (3), or wherein the first liquid feeding means and the second liquid feeding means are each connected to a different outlet of the liquid preparation zone (3).
13. The apparatus as claimed in one of claims 9 to 12, characterized in that the biomass feed device (6a), in particular the feed screw, produces a biomass plug (6b) which prevents a backflow of liquid from the first zone into the feed device.
14. The apparatus according to any of the claims 9 to 13, characterized in that it further comprises a pretreatment reactor (9) of the biomass obtained at the outlet of the impregnation reactor (5), an enzymatic hydrolysis reactor (16) and an alcohol fermentation reactor (18), all or at least two of which are installed in series.
15. Use of the method or device of one of the preceding claims for the treatment of biomass (6), such as wood, straw, agricultural residues and all dedicated energy crops, in particular annual or perennial plants, such as miscanthus, for the production of sugars, biofuels or bio-based molecules.
Technical Field
The present invention relates to a process for treating lignocellulosic biomass to produce "second generation" (2G) sugar liquors. These sugar solutions can be used to produce other products (e.g., alcohols such as ethanol, butanol, or other molecules, e.g., solvents such as acetone, etc.) via biochemical pathways. The process typically comprises three steps, namely liquid (liquor) preparation, impregnation of the biomass and pretreatment of the impregnated biomass, for example by cooking, optionally followed by steam explosion. The invention more particularly focuses on the first two steps of the method.
Prior Art
Lignocellulosic biomass represents one of the most abundant renewable resources on earth. The substrates considered are very diverse and they relate to woody substrates, such as various woods (hardwood and softwood), by-products resulting from agriculture (wheat straw, rice straw, corn cobs, etc.) or from other industries of agro-food, paper, etc.
The process for biochemical conversion of lignocellulosic material into a 2G sugar liquor comprises in particular a pretreatment step and a step of enzymatic hydrolysis with an enzyme mixture (cocktail). These methods also typically include an impregnation step prior to pretreatment. The sugar liquor resulting from the hydrolysis is then treated, for example by fermentation, and the process further comprises a separation step and/or a purification step of the final product.
Lignocellulosic biomass is composed of three main polymers: cellulose (35% -50%), which is a polysaccharide consisting essentially of hexoses; hemicellulose (20% -30%), which is a polysaccharide consisting essentially of pentoses; and lignin (15% to 25%), which is a polymer having a complex structure and a high molecular weight, composed of aromatic alcohols connected via ether bonds. These different molecules are responsible for the intrinsic properties of the plant wall and organize themselves into complex tangles.
Among the three basic polymers constituting lignocellulosic biomass, cellulose and hemicellulose are basic polymers capable of producing 2G sugar liquor.
Typically, during pretreatment, hemicellulose is mainly broken down into sugars, and cellulose is converted to glucose by enzymatic hydrolysis. However, for enzymes, it is difficult to access the crude cellulose, and thus pretreatment is required. This pretreatment can alter the physicochemical properties of the lignocellulosic material, thereby improving the accessibility of the cellulose to enzymes and its reactivity to enzymatic hydrolysis.
There are many techniques for implementing this pretreatment that are advantageous to the present invention, which will be hereinafter classified under the generic term "cooking": acid cooking, alkaline cooking, steam explosion and organic solvent pulping. The latter method involves pretreatment in the presence of one or more organic solvents and usually water. The solvent may be an alcohol (ethanol), an acid (e.g. acetic acid or formic acid) or acetone. The "organosolv pulping" process results in at least partial dissolution of lignin and partial dissolution of hemicellulose. Thus, there are two exit streams: a pretreated substrate with residual cellulose, hemicellulose and lignin, and a solvent phase containing dissolved lignin and a portion of the hemicellulose. There is usually a regeneration step of the solvent, which can extract the lignin stream. Certain "organic solvent pulping" processes (particularly with ethanol) and the addition of strong acids (e.g., H)2SO4) And (4) combining. It is also conceivable to contact the biomass with a solvent via an impregnation reactor before the digestion stage, or with an acidic catalyst before carrying out "organosolv pulping" digestion.
For example, various configurations are reported in the publications "Production of Bioethanol from biochemical materials: A review", M. Balt, Energy Conversion and management 52 (2011) 858-875, or in the publications "Bioethanol Production from biological costs: an overview", N. Sarkar, S. Kumar Ghosh, S. Banner jee, K.kat, recoverable Energy (37) (2012) 19-27.
One of the most effective pretreatments is acid steam explosion, which allows almost complete hydrolysis of the hemicellulose and significantly improves the accessibility and reactivity of the cellulose to the enzymes. One or more further treatments may be performed prior to this pre-treatment.
Patents US-8057639 and US-8512512 propose a process comprising a first step of hydrolysis of hemicelluloses into C5 sugars under mild conditions, which thus protect them from degradation. This step is carried out in the first reactor by injecting steam at a pressure of 1.5 bar or more, at a temperature of 110 ℃ or more, and optionally in the presence of a weak acid. After this step, washing is carried out to extract and recover the C5 sugar liquor, and then the remaining biomass, rich in cellulose and lignin, is sent to the second step (second reactor) where steam explosion takes place. By injecting high pressure steam, which results in a sudden expansion of the biomass (steam explosion), the second reactor is operated at a higher pressure than the first reactor.
Patent application WO-2013/141776 in the field of papermaking describes an impregnation process in a vertical reactor (impregnator) containing an alkaline impregnation liquid, which reactor thus defines a first zone in which the impregnation is carried out. The lignocellulosic material is received at the bottom of the impregnator and transferred to the top of the impregnator by means of two conveying screws. During its transfer to the second zone of the impregnator, which is located above the liquid level, the biomass is drained off and the liquid falls back into the first zone. In this configuration, the liquid level is controlled by introducing an alkaline liquid.
The object of the present invention is to improve the impregnation method and the suitable equipment described in the above-mentioned application WO-2013/141776.
The invention relates in particular to improving the quality of the impregnation of biomass with a catalytic liquid.
In addition, the present invention is directed to making the impregnation method and apparatus easier to use and/or less fluid intensive.
Summary of The Invention
The subject of the present invention is firstly a process for treating lignocellulosic biomass, comprising the following steps:
a. preparing an impregnation liquid comprising a chemical catalyst intended for impregnating the biomass, the chemical catalyst being selected from the group consisting of acid catalysts, basic catalysts and oxidation catalysts, preferably acid catalysts;
b. introducing the ground biomass via an inlet of an impregnation reactor, the inlet being located in a first impregnation zone of the impregnation reactor, the impregnation reactor comprising two superposed zones, namely the first impregnation zone and a second "draining" zone above the impregnation zone;
c. liquid is introduced via a first liquid inlet located in said first impregnation zone of the reactor.
The invention is characterized in that the method further comprises the steps of:
d. the liquid is introduced into the reactor via a second liquid inlet located in another region of the reactor below the biomass inlet in the first impregnation zone.
In the context of the present invention, spatial references of the "above" or "below" type are understood to vary with the preferred vertical direction or the inclination with respect to the vertical of the reactor, so that the reactor comprises, along its height, a series of zones (including an introduction zone followed by a draining zone) through which the biomass fed to the reactor passes. The biomass preferably undergoes an ascending movement in the reactor, so that the introduction zone is located "below" the draining zone. (the invention may be applied to other reactor configurations, and these terms apply as well).
The invention therefore proposes to inject the catalytic liquid into the impregnation reactor not only in the impregnation zone of the reactor, which is conventional, but also below the impregnation zone, below the point of injection of the biomass in the reactor. This region is generally considered to be the "dead zone" or "inactive zone" of the reactor, since the biomass introduced into the first impregnation zone will be conveyed to the drainage zone above the impregnation zone, the ascending movement being caused by the conveying means (e.g. conveying screw) in the reactor. This zone is generally low in height with respect to the other two zones and is located below the first impregnation zone, corresponding to the bottom of the reactor, which is generally placed vertically or inclined, via which one or more conveyor screws are introduced into the reactor, the movement of which is driven by an electric motor. Injecting liquid into this zone runs counter to conventional practice in that there is little/no biomass remaining in the zone, if it is envisaged that the fluid would be injected into this zone, it is only possible that the fluid (if any) would be water intended to lubricate the screw (and therefore essentially for mechanical purposes) if a conveying screw were used in the reactor.
It has now surprisingly proved that the injection of catalytic liquid into this zone below the point of injection of the biomass in the reactor is particularly beneficial for the impregnation process. In fact, it is indirectly demonstrated by comparative measurements of the yield at the end of the steam explosion pre-treatment carried out after the impregnation treatment: impregnation of the biomass proceeds more successfully for an equal amount of catalyst consumption (i.e. not consuming too much catalytic liquid, but by injecting the catalytic liquid into two different zones of the reactor instead of into one zone).
The reasons for this improved impregnation may be varied: the liquid injected below the point of biomass injection may allow better treatment of the biomass just in its injection zone. Indeed, for injecting biomass, it is generally possible to use a feed screw which compresses and conveys the biomass into the reactor, the biomass plug formed in the downstream part of the screw preventing the backflow of liquid to the upstream end of the screw. Furthermore, the biomass plug is mechanically broken when entering the reactor, in particular by using a piston (which meets the biomass plug in question in the reactor). Injecting the liquid slightly below the region where the biomass plug breaks seems to be very advantageous for allowing the catalyst to impregnate the biomass "earlier" during the transport of the biomass in the reactor, thus achieving a better, more complete impregnation for the same reactor residence time. In addition, it was found that the liquid thus injected perfectly replaced any wash water used to lubricate the screw-type biomass conveying device in the reactor.
Other advantages of the invention: better results were obtained without additional consumption of catalyst. The apparatus is simplified because there is no need to provide a separate water supply at the bottom of the reactor, but rather the liquid is withdrawn from its preparation zone. Limiting the addition of water to the reactor is also advantageous to limit the dilution of the catalytic liquid in the reactor, thus limiting the need, if any, to readjust the catalyst content in the liquid.
Advantageously, and as previously described, the biomass is transported from the first impregnation zone to the second draining zone by means of a transport device, such as one or more transport screws. In the first zone, the biomass becomes liquid-impregnated and drains in the second zone. The conveying screw of the draining section may be surrounded by a grid, the excess liquid flowing out through the openings of the grid.
It is also advantageous to introduce the biomass into the first impregnation zone of the reactor by means of a feeding device, in particular a feeding screw, which creates a biomass plug preventing liquid from flowing back from the first zone into the feeding device.
Thus, according to the invention, the liquid produced from the same preparation zone is injected into two points, it being possible, for a given liquid consumption, to meter the proportion of liquid injected into the impregnation zone relative to the liquid injected below the biomass injection point: preferably, 80% to 98%, in particular 85% to 90%, by volume of the liquid introduced into the impregnation reactor is introduced via the first liquid inlet, and the remainder up to 100% of the liquid introduced into the reactor is introduced via the second liquid inlet. Thus, most of the liquid is injected in its conventional zone, "taking" up at most 20% of this quantity in order to inject it into the bottom of the reactor.
The introduction of liquid via the first liquid inlet and/or via the second liquid inlet may be carried out continuously or discontinuously.
Preferably, the further region of the reactor in which the second liquid inlet is located is an inactive region located at the bottom of the reactor which is positioned substantially vertically or inclined with respect to the vertical.
According to a preferred embodiment, the liquid used is an acidic catalytic liquid and the pH of the liquid is adjusted to 0.1 to 4, in particular 0.3 to 2.
Examples of the acid that can be used include at least one acid selected from sulfuric acid, hydrochloric acid, nitric acid, and oxalic acid. Their content in the aqueous phase is preferably from 0.2% to 8% by weight.
Another subject of the present invention is a process for the continuous treatment of lignocellulosic biomass comprising the aforementioned steps and carried out continuously or discontinuously by comprising the following steps:
e. transferring the impregnated and drained biomass from the impregnation reactor outlet to a digestion reactor, optionally in combination with steam explosion;
f. pretreating the biomass in the reactor;
g. enzymatically hydrolyzing the pretreated biomass;
h. the enzymatic hydrolysate (must) obtained from the pretreated biomass is subjected to alcoholic fermentation.
Another subject of the invention is a lignocellulosic biomass processing plant comprising:
-a zone equipped with a liquid outlet for preparing an impregnation liquid comprising a chemical catalyst for impregnation of the biomass, in particular an acid catalyst, a basic catalyst or an oxidation catalyst, preferably an acid catalyst;
-an impregnation reactor comprising a first impregnation zone equipped with an inlet for biomass and a second zone, called draining zone, superimposed on said first impregnation zone and equipped with an outlet for biomass;
-means for feeding the ground biomass to the impregnation reactor via a biomass inlet of the reactor located in the first impregnation zone;
-a first means for feeding an impregnation liquid to the reactor, said means connecting the liquid outlet of the liquid preparation zone to the first liquid inlet in the first impregnation zone of the reactor;
the device further comprises:
-feeding an impregnation liquid to a second device of the reactor, which device connects the liquid outlet of the liquid preparation zone to a second liquid inlet in the region of the reactor located below the biomass inlet of the first impregnation zone.
The apparatus may carry out the aforementioned method by providing means for introducing a catalytic liquid into the second point of the impregnation reactor.
It should be noted that the invention also includes injecting the catalytic liquid into the impregnation reactor at a point other than two injection points, for example via three or four different inlets, including at least one of the impregnation zones, for example two inlets, and at least one below the biomass injection point, for example one or two inlets.
The apparatus according to the invention preferably uses an impregnation reactor which is oriented vertically or obliquely with respect to the vertical, the biomass being subjected to an ascending movement from the first impregnation zone to the second draining zone by means of one or more conveying screws placed in the reactor in said zone.
The impregnation liquid preparation zone may be a tank, a static or dynamic mixer or any other vessel which can mix the solvent (e.g. water) and the catalyst (e.g. in the case of an acidic liquid an acid such as H2SO4) The apparatus of (1).
According to a first embodiment, the first and second liquid feeding means comprise a common line section connected to the same liquid outlet of the liquid preparation zone: a bypass is formed on the line to supply liquid to the impregnation zone of the reactor.
According to another embodiment, the first and second liquid feeding means are each connected to a different outlet of the liquid preparation zone: the liquid is then transported from the other outlet to the second liquid inlet of the reactor using an entirely separate line.
As already mentioned, the biomass feed device, in particular the feed screw, is preferably designed to produce a biomass plug which prevents a backflow of liquid from the first zone into the feed device.
The apparatus according to the invention may additionally comprise a reactor for pretreating the biomass obtained at the outlet of the impregnation reactor, an enzymatic hydrolysis reactor and an alcohol fermentation reactor, the reactor bank or at least two of the reactors therein being installed in series.
Another subject of the invention is the use of the aforementioned method or device for treating biomass, such as wood, straw, agricultural residues and all specialized energy crops, in particular annual or perennial plants, for example miscanthus, to produce sugars, biofuels or bio-based molecules. More generally, the lignocellulosic biomass or lignocellulosic material used in the process according to the invention is obtained, for example, from logs or processed wood (hardwood and softwood), agricultural by-products (e.g. straw), plant fibers, forestry crops, residues from alcohol-, sugar-and grain-producing plants, residues from the paper industry, marine biomass (e.g. cellulose macroalgae) or cellulosic or lignocellulosic material conversion products. The lignocellulosic material may also be a biopolymer, and is preferably cellulose-rich.
Preferably, the lignocellulosic biomass used is wood, wheat straw, wood pulp, miscanthus, rice straw or corn stover.
Detailed Description
The invention will now be described in detail by way of non-limiting examples illustrated by the following figures:
FIG. 1: schematic representation of an apparatus for impregnating biomass with a liquid according to the prior art;
-figure 2: a general schematic diagram of a block diagram type of impregnation apparatus and process used in the present invention;
-figure 3: a schematic overview of a block diagram type of the complete apparatus and process for continuous conversion of biomass to ethanol from biomass impregnation as shown in figure 2.
Fig. 1-3 are described using the following reference numbers, with like numbers corresponding to like components/fluids/products throughout the figures:
1: the water enters the liquid preparation tank
2: the acid enters a liquid preparation tank
3: liquid preparation equipment (tank)
4: acidic liquid
4 a: the acidic liquid enters the impregnation apparatus (reactor) (injection via the impregnation zone)
4 b: the acidic liquid enters the impregnation apparatus (reactor) (injected into the bottom to lubricate the conveyor screw)
5: impregnation apparatus (reactor)
5 a: impregnation zone of impregnation reactor
5 b: draining zone of impregnation reactor
5 c: screw for conveying biomass into impregnation reactor
5 d: an impregnation reactor zone located below the impregnation zone 5a (below the point 6b where the biomass enters the reactor 5 via the feed screw 6a)
6: ground biomass
6 a: conical screw for feeding biomass to an impregnation reactor
6 b: biomass sealing plug in feeding screw 6a
7: impregnated and drained biomass
8: screw feeder or plug-screw (plug-screw) feeder of pretreatment equipment
9: pretreatment equipment (blasting reactor)
10: squeezing liquid of screw 8 of pretreatment equipment
11: steam injection for pretreatment
12: pretreated biomass and steam
13: device for separating steam and pretreated biomass (cyclone)
14: condensation of steam
15: pretreated biomass
16: enzymatic hydrolysis
17: sugar-containing enzymatic hydrolysates
18: alcohol (ethanol) fermentation
19: fermented wine containing ethanol
20: distillation
21: concentrated alcohol
22: crude distiller's grains.
FIG. 1 is a schematic diagram of an apparatus for impregnating biomass with a liquid according to the prior art; accordingly, it is not necessarily drawn to scale and does not represent all of the components of a device, but only those components that are of particular interest for describing the present invention.
The process according to the invention is a process for treating lignocellulosic biomass prior to enzymatic hydrolysis. It is integrated into processes involving the production of second generation sugars from which oxygen-containing molecules (e.g., alcohols such as ethanol, butanol, etc.) can be obtained by a number of biochemical pathways.
Thus, the following examples relate to an integrated acid impregnation process followed by a continuous or discontinuous steam explosion pretreatment, optionally with recycling of the acidic impregnation liquid.
The process is compatible with processes for the production of 2G sugars (i.e. those obtained from lignocellulosic biomass) or, more generally, bio-based molecules (i.e. molecules derived from or derived from natural substrates).
Biomass and transfer zone
Depending on the biomass (straw, wood, etc.), a grinding step is required to make the particle size compatible with the technical means and operating conditions of the step. For this reason, simple shredding may be sufficient, but grinding with or without thinning may be required.
Typically, the ground biomass 6 has a particle size (largest dimension) of no greater than 300 mm. Typically, the grinding of the straw is carried out using a 5-100mm screen and the wood is cut into cuboid pieces having a length of 20-160mm, a width of 10-100mm and a thickness of 2-20 mm.
The ground biomass 6 is introduced into the first impregnation zone 5a of the impregnation reactor via a conical feed screw 6a in which a plug of sealed biomass 6b prevents liquid from flowing back from said zone 5a into the screw 6a just before entering the first impregnation zone. The conical compression helix may comprise a shield in the form of a perforated grid. It has a conical portion connected to the bottom of the first impregnation zone 5a of the reactor. Thus, the helix 6a serves a dual function: firstly, biomass is continuously introduced into the impregnation reactor and secondly, a biomass plug is formed to achieve tightness and prevent leakage of liquid from the impregnation reactor to the spiral and upstream of the spiral.
Step of impregnation
The impregnation is carried out at atmospheric pressure and at a temperature of from 10 to 95 ℃. The residence time of the biomass in the impregnation reactor 5 is generally from 20 seconds to 60 minutes, preferably at least 30 seconds, preferably at least 1 minute, preferably not more than 45 minutes, and generally from 1 to 35 minutes. Preferably, it is carried out in a single reactor.
The impregnation reactor 5 (or impregnator) is tubular and has an inclined orientation perpendicular or at an angle of less than 60 ° with respect to the perpendicular. In the example it is vertical. The reactor comprises two superposed impregnation zones 5a, 5b located on the same axis. The lower zone 5a is called the first impregnation zone and receives the compressed biomass from the feed screw 6a via an orifice above which the acidic liquid inlet 4 is arranged, still located in this first zone 5 a. The zone 5b located above (top zone) is called the second impregnation zone or draining zone: it receives biomass from the first impregnation zone 5 a.
The reactor 5 (impregnator) is equipped with one or more conveying screws 5c which transfer the biomass via the bottom of the first impregnation zone to the outlet orifice via the top of the second impregnation zone 5 b.
The first impregnation zone 5a (thus the zone where the impregnation takes place) corresponds to a space filled with an impregnation liquid. The second impregnation zone 5b does not contain any continuous liquid phase. It is particularly advantageous to maintain a constant distribution between the first impregnation zone and the second impregnation zone. For this purpose, the reactor is equipped with a detection system (level sensor), preferably with a system for regulating the level (not shown), which can ensure filling to the desired level.
The catalytic impregnation liquid is an aqueous solution having a pH of 0.1-6, preferably 0.2-4.0, and a temperature of 10-95 ℃. The acid here is sulfuric acid. Liquids of this type are well known to those skilled in the art and any other acid commonly used for impregnation is suitable for use. The amount of acid and the temperature of the liquid are generally fixed. Means for obtaining and maintaining the temperature are known to the person skilled in the art. The preparation of the liquid here takes place in a tank 3 with a water inlet 1 and a concentrated sulfuric acid inlet 2.
The effect of compressing the biomass during the formation of the plug of biomass (at the level of the conveying screw) and the effect of reducing the pressure at the inlet of the first impregnation zone filled with liquid, allows a better saturation of the biomass (sponge effect). The biomass is transferred through a first zone 5a, in which first zone 5a the biomass is impregnated towards a second impregnation zone 5b located above the liquid level.
In the second impregnation zone 5b, a part of the impregnation liquid is separated from the impregnated biomass by draining during the rise to the second impregnation zone, the drained liquid falling back into the first impregnation zone 5 a.
Preferably, the second impregnation zone 5b is equipped with one or more screens that hold the wet biomass in the second impregnation zone, said screens thereby allowing liquid to flow from the second impregnation zone 5b into the first impregnation zone 5 a.
Upon leaving the second impregnation zone and the impregnation reactor, the impregnated and drained biomass is recovered and contains little or no free water. The solids content is generally from 15% to 40% by weight.
Separated liquid, commonly referred to as waste liquid, is found in the liquid in the first impregnation zone.
Preparation of impregnation liquids
Due to the impregnation, liquid and acidity are lost. It is therefore necessary to add fresh acidic liquid periodically.
These additions make it possible to precisely adjust the liquid level in the impregnation reactor.
Liquid preparation is also a step in which the operating parameters, such as temperature, pH or any other characteristic, can be adjusted. The appropriate acid concentration is adjusted by the input of acid and/or water. Homogeneous liquids can also be produced. This step is carried out in the liquid preparation zone.
Various apparatuses can be used, for example here a mixing tank or a mixer (preferably a static mixer) equipped with a stirring system (not shown).
Preferably, the device is equipped with sensors for measuring pH and flow of water, acid and prepared liquid, etc. All of these sensors together can implement control of the equilibrium flow and acidity, thus having a steady continuous operation under the desired conditions.
The liquid preparation tank 3 and/or the impregnation reactor 5 are equipped with heating means such as jackets, coils (and optionally an exchanger located on an optional liquid recirculation loop adjacent to or directly on the device (tank, mixer, etc.)) to heat.
The liquid tank 3 is connected to the impregnation reactor via one or more liquid transfer lines.
Thus, the liquid can be prepared in a suitable concentration and at a suitable flow rate, which can result in a determined pH (or any other characteristic), which can be an adjusted nominal value.
The present invention results from the following observations: still in fig. 1, in the impregnation reactor 5, it is noted that there is a third zone 5d located below the introduction level of the biomass plug 6b, below the first impregnation zone 5 a: this is a "dead" zone, since no desired biomass passes through at this location. This dead or "inactive" zone is necessary to allow space for the expansion of the biomass plug and limit the accumulation of solids at the bottom of the reactor. This zone 5d consists essentially of liquid, since it is located outside the channels required for the solids. However, considering the deviation from the ideal case of piston conveyance by the rising screw 5c, and considering the presence of particles in the biomass plug, the presence of a small fraction of solids may be observed in the dead zone. Now, it is desirable to avoid accumulation of solid components in this region 5 d.
It is therefore chosen to inject into this zone 5d a fluid which is not a simple water supply (which would lead to an additional dilution of the liquid in the reactor), but an additional liquid supply from the preparation tank 3, as shown in figures 2 and 3 described below.
According to fig. 2, acid and water are introduced into the acidic liquid preparation tank 3 via line 1 and line 2, respectively. The acidic liquid of line 4 is then injected into the macerator 5, mixing with the ground biomass introduced into the process via line 6. The acidic liquid 4 is injected into the impregnation tank 5, more precisely into the impregnation zone 5a, by means of the line 4a and the line 4 b. The biomass, which is in contact with the acidic liquid in the impregnation zone 5a, then enters the draining zone 5b for separation from the liquid fraction. The impregnated and drained biomass is transferred to the next step of the process via line 7.
In this embodiment of the invention, an additional line 4b is optionally added for supplying liquid to the reactor 5 in a region 5d below the biomass feed point, said line 4b here being in the form of a bypass line of the main line 4-4a connected to the inlet of the tank 3. It goes without saying that any other piping arrangement is also possible which also transports the liquid to the bottom of the reactor, in particular by alternatively providing a dedicated line connecting the second outlet of the tank to the inlet of the zone 5d of the reactor 5, or by using any other system of distributing the liquid from the tank 3 to two separate inlets of the reactor 5. Means are provided for adjusting the quantity of liquid injected into the impregnation zone 5a with respect to the quantity in the injection zone 5d and are known in the art (regulating valves, etc.).
Fig. 3 shows the process of fig. 2, which is continued after impregnation by a continuous steam explosion pretreatment, and then through several other successive process steps until alcohol fermentation.
The process is therefore carried out in the following manner: the impregnation takes place in the reactor 5 as shown in fig. 2 and will therefore not be described again.
Once the biomass is impregnated and drained, the biomass is transferred via line 7 and introduced into a steam explosion pre-treatment unit 9 by means of a conveying screw 8, which conveying screw 8 is capable of compressing the biomass to form a biomass plug. During this compression, solid/liquid separation occurs and the spent acid liquid 10 is discharged through the perforated region of the spiral. Optionally, the spent acidic liquid 10, also known as press liquor, can be at least partially recycled by reintroducing it into the liquid preparation tank 3. The biomass is then treated in a treatment device 9. Steam is introduced into the pretreatment reactor 9 via line 11. In the reactor, acid digestion and steam explosion were carried out. Explosive expansion takes place and the mixture 12 of pretreated substrate and steam is fed to a separation device 13 of the cyclone type.
It should be noted that in this example steam explosion is performed after cooking, but still optional, and for the purpose of this pre-treatment other treatments than cooking are possible, i.e. changing at least one physicochemical property of the (impregnated) biomass, such as its degree of polymerization or crystallinity. These other cooking processes have already been mentioned above. The operating conditions for the cooking, which here is acidic, are for example as follows: the apparatus 9 comprises a cooking zone in which the biomass is brought into contact with steam for a period of time ranging from 1 to 30 minutes at a specific steam consumption of from 0.05 to 10 tons per ton of biomass solids, said zone having a temperature of 150 ℃ and a temperature of 250 ℃ and a pressure of from 0.5 to 4 MPa, followed by a zone where the biomass obtained from the cooking zone is expanded and followed by a zone where the steam is separated from the biomass. Preferably, the conditions are adjusted to limit the cooking time to 1-30 minutes. Typically, specific steam consumption is in the range of 0.05 to 10 tonnes per tonne of solids. The recovered steam is advantageously recycled to the steam explosion step after compression, or optionally to on-site utilities. Here, this step is carried out in a reactor 9, the reactor 9 being tubular and horizontal (it is also possible to slightly incline to make the liquid flow) and equipped with a biomass conveying screw. At the downstream end of the reactor 9, the biomass is very rapidly entrained by the steam to an expansion zone in a line called a purge line (blowline) which has a reduced diameter with respect to the cooking zone.
In the device 13, the steam 14 is separated from the pretreated biomass 15. The pretreated biomass is then converted in a conversion device 16 with an enzyme mixture into a sugar-containing enzymatic hydrolysate (must) 17. The sugars are converted to alcohols (e.g., ethanol, acetone, butanol) by fermentation in fermentation step 18. The fermented wine 19 is sent to a separation and purification step 20. Step 20, for example by distillation, may effect separation of a stream 21 containing concentrated alcohol from a crude stillage (waste water, residual lignin) 22. The conditions of enzymatic hydrolysis and of continuous or simultaneous fermentation are adapted to the desired product and are known to the person skilled in the art.
It should be noted with respect to fig. 2 that the present invention applies equally and with the same advantages to processes in which some or all of the steps following the steam explosion are not performed continuously but rather in a "batch" or "batch feed" mode.
Examples
In the examples described below, the abbreviation "SC" denotes the solid content, determined according to the Standard ASTM E1756-08(2015), "Standard Test Method for Determination of Total Solids in Biomass".