CN106566853B - Pretreatment method of lignocellulose - Google Patents
Pretreatment method of lignocellulose Download PDFInfo
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Abstract
The invention relates to the fields of biological engineering and chemical engineering, and discloses a pretreatment method of lignocellulose, which comprises the following steps: sequentially carrying out rinsing impurity removal treatment, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material, or sequentially carrying out rinsing impurity removal treatment, uniformly mixing treatment with acid-containing or alkali-containing liquid, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material; and the lignocellulosic feedstock is contacted with an acid-containing or alkali-containing liquid in at least one treatment prior to said press dewatering treatment. The method of the invention not only can greatly improve the recovery and utilization rate of hemicellulose and the cellulose enzymolysis conversion rate, but also can effectively remove impurities and reduce the operation cost.
Description
Technical Field
The invention relates to the fields of biological engineering and chemical engineering, in particular to a pretreatment method of lignocellulose.
Background
The pretreatment method of lignocellulose comprises a chemical method, a physical method and a biological method, and aims to separate three components of cellulose, hemicellulose and lignin, hydrolyze the hemicellulose in the lignocellulose, change an ordered structure in the cellulose and increase the contact area of the cellulose and an enzyme catalytic substance.
The prior pretreatment methods comprise a steam explosion method, a dilute acid warm baking method, an ammonia fiber explosion method, a carbon dioxide explosion method, a wet oxidation method, a peroxide method, a sulfur dioxide method and other methods. However, many of the methods are not popularized due to low raw material recovery rate, environmental pollution, high equipment cost and operation cost, complex operation and the like, and the mature methods are only two methods, namely a steam explosion method and a dilute acid warm baking method.
The steam explosion method is a method which utilizes high-pressure steam (the temperature is generally 200-. However, under high temperature and high pressure, sugar monomers generated by hydrolysis of hemicellulose can generate derivatization reaction to generate various derivatives, such as furfural, furan and the like, the recovery rate of the hemicellulose is low (generally 30% -50%), the cellulose hydrolysis conversion rate is low (generally 60% -75%), and high-operation production is directly caused.
The dilute acid warm baking method is also a mature method used at present. Low-concentration sulfuric acid (1-2%) is used for treating for 4-24 hours at the temperature close to 100 ℃, so that the hemicellulose is hydrolyzed, the crystal structure of the cellulose is changed, and the specific surface area of the cellulose is increased to be beneficial to subsequent enzymolysis. The recycling rate of hemicellulose by the dilute acid warm baking method is high (generally 70% -85%), but the hydrolysis conversion rate of cellulase is low (generally 50% -60%), the reaction time is long, the power cost is high, and sugar monomers can be derived into fermentation inhibitors such as furfural and formic acid.
In addition, can be mingled with more silt usually in the lignocellulose raw materials, the metallics of not magnetic separation, a series of impurity such as quick-wear part that machinery rotation position dropped, these impurity can follow the material and get into in the follow-up equipment, cause equipment trouble easily, increase the maintenance work volume, influence the stability of production and the quality of product, and simultaneously, the volume that can also increase the auxiliary material is taken into in impurity, the auxiliary material can adsorb on the impurity body or directly react with impurity, cause the auxiliary material quantity increase.
Disclosure of Invention
The invention aims to overcome the defects of low hemicellulose recovery and utilization rate, low cellulose enzymolysis conversion rate and high operation cost of the lignocellulose pretreatment method in the prior art, and provides the lignocellulose pretreatment method.
In the existing method for pretreating lignocellulose by adopting a steam explosion method, the lignocellulose raw material is not treated before the steam explosion treatment, so that the recovery rate of hemicellulose and the hydrolysis conversion rate of cellulose are low, and higher operation cost is caused. However, the inventor of the present invention has unexpectedly found that, during pretreatment of lignocellulose, before steam explosion treatment, the lignocellulose raw material is sequentially subjected to rinsing impurity removal treatment and extrusion dehydration treatment, or sequentially subjected to rinsing impurity removal treatment, acid-containing or alkali-containing liquid blending treatment and extrusion dehydration treatment, and before the extrusion dehydration treatment, the lignocellulose raw material is contacted with the acid-containing or alkali-containing liquid in at least one treatment, so that the hemicellulose recovery rate and the cellulose enzymolysis conversion rate can be greatly improved, impurities can be effectively removed, and the operation cost can be reduced.
Accordingly, in order to achieve the above object, the present invention provides a method for pretreating lignocellulose, comprising: sequentially carrying out rinsing impurity removal treatment, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material, or sequentially carrying out rinsing impurity removal treatment, uniformly mixing treatment with acid-containing or alkali-containing liquid, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material; and the lignocellulosic feedstock is contacted with an acid-containing or alkali-containing liquid in at least one treatment prior to said press dewatering treatment.
The pretreatment method of the lignocellulose adopts a mode of combining various treatments, not only can greatly improve the recovery and utilization rate of the hemicellulose and the enzymolysis and conversion rate of the cellulose, but also can effectively remove impurities doped in the lignocellulose raw material, well separate the impurities from the lignocellulose raw material, and maximally reduce the influence of the impurities on subsequent links, thereby reducing the using amount of auxiliary materials, reducing the failure rate of equipment, reducing the frequency and intensity of impurity cleaning and reducing the operation cost.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
Fig. 1 is a flow chart of a method for pretreating lignocellulose according to a preferred embodiment of the present invention.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The invention provides a pretreatment method of lignocellulose, which comprises the following steps: sequentially carrying out rinsing impurity removal treatment, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material, or sequentially carrying out rinsing impurity removal treatment, uniformly mixing treatment with acid-containing or alkali-containing liquid, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material; and the lignocellulosic feedstock is contacted with an acid-containing or alkali-containing liquid in at least one treatment prior to said press dewatering treatment.
In the method of the present invention, preferably, the rinsing impurity removal process includes: mixing the crushed lignocellulose raw material with a first liquid, wherein the first liquid is water or an acid-containing or alkali-containing liquid. Further preferably, the water is process primary water. The acid-containing or alkali-containing liquid is not particularly limited, and may be various acid-containing or alkali-containing liquids commonly used in the art, for example, an acid solution or an alkali solution, wherein the acid and alkali are not particularly limited, and may be various acids and alkalis commonly used in the art, preferably, the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid, and the alkali is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.
Preferably, the weight ratio of the lignocellulosic feedstock to the first liquid is from 1:5 to 40, more preferably from 1:10 to 30, even more preferably from 1:15 to 25; the time for rinsing and impurity removing treatment is 2-60min, more preferably 10-45min, and still more preferably 15-30 min.
In the method of the present invention, it should be understood by those skilled in the art that heavy component impurities in the material after rinsing and wetting in the rinsing and impurity removing process will be precipitated to the bottom of the rinsing and wetting device and then discharged out of the rinsing and wetting device in batches, so that the impurities entrained in the lignocellulose raw material can be removed by the rinsing and impurity removing process and the purpose of wetting the material can be achieved. In order to better recycle the materials, the method of the invention preferably further comprises the following steps: and (3) draining impurities precipitated in the rinsing impurity removal treatment, carrying out pollution-free treatment on the precipitate obtained by the draining treatment, and recovering the liquid obtained by the draining treatment and returning the liquid to the rinsing impurity removal treatment for recycling. The pollution-free treatment is not particularly limited, and may be various pollution-free treatments commonly used in the art, such as a field-returning treatment or a landfill treatment, which are well known to those skilled in the art and will not be described herein again.
In the method of the present invention, preferably, the embodiment of the treatment of uniformly mixing with the acid-containing or alkali-containing liquid comprises: and uniformly mixing the impurity-removed material obtained by rinsing impurity removal treatment with the acid-containing or alkali-containing liquid. The acid-containing or alkali-containing liquid is not particularly limited, and may be various acid-containing or alkali-containing liquids commonly used in the art, for example, an acid solution or an alkali solution, wherein the acid and the alkali are not particularly limited, and may be various acids and alkalis commonly used in the art, preferably, the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid, and the alkali is one or more of sodium hydroxide, potassium hydroxide, and ammonia water. It will be understood by those skilled in the art that the acid or base in the acid-or base-containing liquid refers to an acid or base that is solvent-free, i.e. an acidic solute or a basic solute in the acid-or base-containing liquid.
In the method of the present invention, preferably, the method further comprises: after rinsing and impurity removal treatment and before uniformly mixing with acid-containing or alkali-containing liquid, draining and/or extruding and dehydrating the impurity-removed material, and further preferably, the dry matter content of the material obtained by draining and/or extruding and dehydrating treatment is 35-50%. In order to recycle the materials better, the liquid obtained by the draining treatment and/or the squeezing dehydration treatment is preferably returned to the rinsing impurity removal treatment for recycling. It will be understood by those skilled in the art that the liquid obtained by the draining process and/or the press dewatering process refers to a liquid phase material obtained by the draining process and/or the press dewatering process.
In the method of the present invention, preferably, the press dehydration treatment is performed by: and (3) carrying out extrusion dehydration on the material obtained by rinsing impurity removal treatment or even mixing treatment with acid-containing or alkali-containing liquid, and controlling the dry matter content of the material to be more than 30%, preferably more than 35%, and further preferably more than 40%. In order to better recycle the materials, the liquid obtained by the extrusion dehydration treatment is preferably returned to the rinsing impurity removal treatment and/or the blending treatment with the acid-containing or alkali-containing liquid for recycling. As will be understood by those skilled in the art, when the rinsing impurity removal treatment, the squeezing dehydration treatment and the steam explosion treatment are sequentially carried out on the lignocellulose raw material, the material obtained by the rinsing impurity removal treatment is squeezed and dehydrated; when the lignocellulose raw material is sequentially subjected to rinsing impurity removal treatment, mixing treatment with acid-containing or alkali-containing liquid, extrusion dehydration treatment and steam explosion treatment, the material obtained by mixing treatment with the acid-containing or alkali-containing liquid is subjected to extrusion dehydration. Wherein the liquid obtained by the squeezing dehydration treatment is a liquid-phase substance obtained by the squeezing dehydration treatment.
In the method of the present invention, when the steam explosion treatment is performed, a higher temperature, such as more than 180 ℃, may more easily cause the sugar monomer generated by the hydrolysis of hemicellulose to generate a derivatization reaction, and before the steam explosion treatment, the method of the present invention sequentially performs rinsing impurity removal treatment, (draining treatment), blending treatment with an acid-containing or alkali-containing liquid, and squeezing dehydration treatment on the lignocellulose raw material, so that the steam explosion treatment can still be performed at a lower temperature and a better effect can be obtained, and therefore, preferably, the conditions of the steam explosion treatment include: the temperature is 145-180 ℃, more preferably 150-175 ℃, and even more preferably 160-170 ℃; the time is 5-90min, preferably 20-80min, and more preferably 40-60 min. It should be understood by those skilled in the art that the steam used in the steam explosion treatment is saturated steam.
The method of the invention can also comprise the following steps: and adding an additive into the material obtained by the extrusion dehydration treatment, wherein the additive is an acid-containing or alkali-containing liquid, or an acid gas or an alkali gas. The acid gas or the basic gas is not particularly limited, and may be various acid gases or basic gases commonly used in the art, for example, the acid gas may be SO2、CO2And H2One or more of S, the alkaline gas may be NH3. It will be understood by those skilled in the art that the acid or base in the acid-or base-containing liquid refers to an acid or base that is solvent-free, i.e. an acidic solute or a basic solute in the acid-or base-containing liquid.
In the method of the present invention, it should be understood by those skilled in the art that the steam explosion treatment can be performed in a pre-treatment closed device, which is well known to those skilled in the art and will not be described herein.
In the method of the present invention, as described above, an acid or an alkali may be added in the rinsing impurity removal treatment, the blending treatment with the acid-containing or alkali-containing liquid, and the steam explosion treatment, and the amount of the acid or the alkali added in each treatment is not particularly limited as long as the weight ratio of the acid or the alkali contained in the material to the dry material is 0.001 to 0.05: 1, the product is obtained. Therefore, the adding amount of the acid or the alkali in the method is preferably controlled so that the weight ratio of the acid or the alkali contained in the material to the dry material in the steam explosion treatment is 0.001-0.05: 1, more preferably 0.005 to 0.04: 1, more preferably 0.01 to 0.03: 1. in order to reduce the corrosion of acid or alkali to the pretreatment closed equipment, preferably, the amount of the acid or alkali added in the rinsing impurity removal treatment or the rinsing impurity removal treatment and the mixing treatment with the acid-containing or alkali-containing liquid is controlled, so that when the steam explosion treatment is carried out without adding the acid-containing or alkali-containing additive in the steam explosion treatment, the weight ratio of the acid or alkali contained in the material to the dry material is 0.001-0.05: 1, more preferably 0.005 to 0.04: 1, more preferably 0.01 to 0.03: 1. in the process of the present invention, it will be understood by those skilled in the art that no base is added when the acid is added and no acid is added when the base is added in the process, and that the acid or base contained in the feed is meant to be the acid or base without solvent, i.e., the acidic solute or the basic solute in the feed.
In the process of the present invention, the concentration of the acid or base in the acid-or base-containing liquid is preferably from 0.05 to 7% by weight. The kind of the acid and the base is not particularly limited, and various acids and bases commonly used in the art can be used, preferably, the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the base is one or more of sodium hydroxide, potassium hydroxide and ammonia water.
In the method of the present invention, preferably, the method further comprises: and discharging the material obtained by the steam explosion treatment from the pretreatment closed equipment, wherein the discharging mode is a continuous discharging mode or an intermittent discharging mode.
Examples
The present invention will be described in detail below by way of examples. In the following examples and comparative examples, reagents or materials used are commercially available and used in the methods commonly used in the art unless otherwise specified.
Wherein the lignocellulose raw material is corn straw, the particle size is 30-50mm after being crushed, and the water content is 20 wt%.
The infrared moisture meter is available from Western chemical instruments (Beijing) science and technology Co., Ltd, and is GZ 10-FD-720.
Example 1
This example illustrates the pretreatment of lignocellulose according to the invention.
The pretreatment method of lignocellulose comprises the following steps:
(1) mixing 10kg of crushed lignocellulose raw material with 200kg of 1.6 wt% sulfuric acid solution, rinsing and impurity removing treatment is carried out, the rinsing and wetting time is 25min, then impurities precipitated to the bottom of the rinsing and wetting device are discharged out of the rinsing and wetting device, draining treatment is carried out, the sediment obtained by draining treatment is buried, and the liquid obtained by draining treatment is recovered and returned to the rinsing and impurity removing treatment for recycling.
(2) And (2) carrying out extrusion dehydration on the impurity-removed material obtained by rinsing and impurity removing in the step (1) to ensure that the dry matter content of the material is 40% to obtain 20kg of material, and returning the liquid obtained by the extrusion dehydration to the rinsing and impurity removing for recycling.
(3) And (3) feeding 20kg of the material obtained by the extrusion dehydration treatment in the step (2) into a pretreatment closed device for steam explosion treatment, wherein the weight ratio of sulfuric acid contained in the material to dry materials is 0.02: 1, the temperature of the saturated steam explosion treatment is 165 ℃ and the time is 50 min.
(4) And (4) discharging the material obtained by the steam explosion treatment in the step (3) from the pretreatment closed equipment in a continuous discharge mode.
Example 2
This example illustrates the pretreatment of lignocellulose according to the invention.
The pretreatment method of lignocellulose comprises the following steps:
(1) mixing 10kg of crushed lignocellulose raw material with 160kg of 0.97 wt% sodium hydroxide solution, rinsing and impurity removing for 30min, discharging impurities precipitated at the bottom of a rinsing and wetting device out of the rinsing and wetting device, draining, returning the precipitate obtained by draining to the field, recovering the liquid obtained by draining, and returning the liquid to the rinsing and impurity removing treatment for recycling.
(2) And (2) carrying out extrusion dehydration on the impurity-removed material obtained by rinsing and impurity removing in the step (1) to ensure that the dry matter content of the material is 40% to obtain 20kg of material, and returning the liquid obtained by the extrusion dehydration to the rinsing and impurity removing for recycling.
(3) And (3) uniformly mixing 20kg of the material obtained by the extrusion dehydration treatment in the step (2) with 2.86kg of 5 weight percent sodium hydroxide solution.
(4) And (3) carrying out extrusion dehydration treatment on the mixed material obtained in the step (3), controlling the dry matter content of the material to be 35% to obtain 22.86kg of material, and returning the liquid obtained by the extrusion dehydration treatment to the step (1) and/or the step (3) for recycling.
(5) And (3) feeding the 22.86kg of material obtained by the extrusion dehydration treatment in the step (4) into a pretreatment closed device for steam explosion treatment, wherein the weight ratio of sodium hydroxide contained in the material to dry materials is 0.03: 1, the temperature of the saturated steam explosion treatment is 160 ℃, and the time is 60 min.
(6) And (5) discharging the material obtained by the steam explosion treatment in the step (5) from the pretreatment closed equipment in an intermittent discharge mode.
Example 3
The pretreatment method of lignocellulose comprises the following steps:
(1) mixing 10kg of crushed lignocellulose raw material with 250kg of primary process water, rinsing and impurity removing treatment is carried out, the rinsing and wetting time is 20min, then impurities precipitated to the bottom of the rinsing and wetting device are discharged out of the rinsing and wetting device, draining treatment is carried out, the sediment obtained by draining treatment is buried, and the liquid obtained by draining treatment is recovered and returned to the rinsing and impurity removing treatment for recycling.
(2) And (2) carrying out extrusion dehydration on the impurity-removed material obtained by rinsing and impurity removing in the step (1) to enable the dry matter content of the material to be 50% to obtain 16kg of material, and returning the liquid obtained by the extrusion dehydration to the rinsing and impurity removing for recycling.
(3) And (3) uniformly mixing 16kg of the material obtained by the extrusion dehydration treatment in the step (2) with 1.78kg of 4.5 weight percent hydrochloric acid solution.
(4) And (3) carrying out extrusion dehydration treatment on the mixed material obtained in the step (3), controlling the dry matter content of the material to be 45% to obtain 17.78kg of material, and returning the liquid obtained by the extrusion dehydration treatment to the step (1) and/or the step (3) for recycling.
(5) And (3) feeding the 17.78kg of material obtained by the extrusion dehydration treatment in the step (4) into a pretreatment closed device for steam explosion treatment, wherein the weight ratio of hydrochloric acid contained in the material to dry materials is 0.01: 1, the temperature of the saturated steam explosion treatment is 170 ℃, and the time is 40 min.
(6) And (5) discharging the material obtained by the steam explosion treatment in the step (5) from the pretreatment closed equipment in a continuous discharge mode.
Example 4
This example illustrates the pretreatment of lignocellulose according to the invention.
As shown in fig. 1, the pretreatment method of lignocellulose includes:
(1) mixing 10kg of crushed lignocellulose raw material with 300kg of primary process water, rinsing and impurity removing treatment is carried out, the rinsing and wetting time is 15min, then impurities precipitated to the bottom of the rinsing and wetting device are discharged out of the rinsing and wetting device, draining treatment is carried out, the sediment obtained by draining treatment is buried, and the liquid obtained by draining treatment is recovered and returned to the rinsing and impurity removing treatment for recycling.
(2) And (2) carrying out extrusion dehydration on the impurity-removed material obtained by rinsing and impurity removing in the step (1) to enable the dry matter content of the material to be 35% to obtain 22.86kg of material, and returning the liquid obtained by the extrusion dehydration to the rinsing and impurity removing for recycling.
(3) And (3) uniformly mixing 22.86kg of the material obtained by extrusion dehydration treatment in the step (2) with 1.67kg of 10 weight percent ammonia water solution.
(4) And (3) carrying out extrusion dehydration treatment on the mixed material obtained in the step (3), controlling the dry matter content of the material to be 30% to obtain 24.53kg of material, and returning the liquid obtained by the extrusion dehydration treatment to the step (1) and/or the step (3) for recycling.
(5) Feeding 24.53kg of the material obtained by the extrusion dehydration treatment in the step (4) into a pretreatment closed device for steam explosion treatment, wherein 0.07kg of alkaline gas NH is added into the material3NH contained in the material is detected and calculated3·H2The weight ratio of O to dry materials is 0.04: 1, the temperature of the saturated steam explosion treatment is 150 ℃, and the time is 80 min.
(6) And (5) discharging the material obtained by the steam explosion treatment in the step (5) from the pretreatment closed equipment in a continuous discharge mode.
Example 5
This example illustrates the pretreatment of lignocellulose according to the invention.
The pretreatment method of lignocellulose comprises the following steps:
(1) mixing 10kg of crushed lignocellulose raw material with 120kg of 0.1 weight percent nitric acid solution, rinsing and impurity removing treatment is carried out, the rinsing and wetting time is 40min, then impurities precipitated to the bottom of the rinsing and wetting device are discharged out of the rinsing and wetting device, draining treatment is carried out, the sediment obtained by draining treatment is buried, and the liquid obtained by draining treatment is recovered and returned to the rinsing and impurity removing treatment for recycling.
(2) And (2) carrying out extrusion dehydration on the impurity-removed material obtained by rinsing and impurity removing in the step (1) to ensure that the dry matter content of the material is 40% to obtain 20kg of material, and returning the liquid obtained by the extrusion dehydration to the rinsing and impurity removing for recycling.
(3) And (3) uniformly mixing 20kg of the material obtained by the extrusion dehydration treatment in the step (2) with 2.86kg of 0.7 weight percent nitric acid solution.
(4) And (3) carrying out extrusion dehydration treatment on the mixed material obtained in the step (3), controlling the dry matter content of the material to be 35% to obtain 22.86kg of material, and returning the liquid obtained by the extrusion dehydration treatment to the step (1) and/or the step (3) for recycling.
(5) And (3) feeding 22.86kg of the material obtained by the extrusion dehydration treatment in the step (4) into a pretreatment closed device for steam explosion treatment, wherein 2kg of 0.5 wt% nitric acid solution is added into the material, and the weight ratio of nitric acid contained in the material to dry materials is 0.005: 1, the temperature of the saturated steam explosion treatment is 175 ℃, and the time is 30 min.
(6) And (5) discharging the material obtained by the steam explosion treatment in the step (5) from the pretreatment closed equipment in a continuous discharge mode.
Example 6
The method of example 1 was followed except that, in the step (1), 10kg of the pulverized lignocellulose raw material was mixed with 200kg of a 0.08 wt% sulfuric acid solution to carry out rinsing impurity removal treatment; in the step (2), 20kg of material with 40% of dry matter content is obtained through extrusion dehydration treatment; in the step (3), through detection and calculation, the weight ratio of the sulfuric acid contained in the materials to dry materials is 0.001: 1.
example 7
The method of example 1 was followed except that, in the step (5), the temperature of the saturated steam explosion treatment was 220 ℃ for 50 min.
Example 8
The method of example 1 was followed except that, in the step (5), the temperature of the saturated steam explosion treatment was 180 ℃ for 50 min.
Comparative example 1
The procedure of example 1 was followed except that, without carrying out steps (1) to (2), 10kg of the pulverized lignocellulosic raw material was directly charged into a closed pretreatment apparatus to be subjected to steam explosion.
Comparative example 2
The procedure is as in example 1, except that in step (1) the 1.6% by weight sulfuric acid solution is replaced by process water.
Test examples
The recovery rate of hemicellulose, the cellulose enzymolysis conversion rate and the proportion of heavy-grade impurities in a dry basis of the materials obtained in examples 1 to 8 and comparative examples 1 to 2 were measured, and the results are shown in table 1, wherein the recovery rate of hemicellulose is measured by the following method: the method comprises the steps of quantifying and sampling a material before steam explosion treatment and a material after steam explosion treatment respectively, completely degrading hemicellulose in the material into monosaccharide by adding sulfuric acid, detecting xylose concentration, and calculating the content of the hemicellulose in the material before steam explosion treatment and the content of the hemicellulose in the material after steam explosion treatment respectively (see NREL method, wherein the content of various monosaccharides and lignin in biomass is measured (2004 version)), so as to obtain the hemicellulose content in the material before steam explosion treatment and the hemicellulose content in the material after steam explosion treatment, and the hemicellulose recovery rate is the hemicellulose content in the material after steam explosion treatment/the hemicellulose content in the material before steam explosion treatment, wherein the calculation coefficient from xylose to hemicellulose is 1.136, namely the hemicellulose content is xylose/1.136.
The method for measuring the cellulose enzymolysis conversion rate comprises the following steps: quantifying and sampling the material after the steam explosion treatment, completely degrading cellulose in the material into monosaccharide by adding sulfuric acid, detecting the concentration of glucose, and calculating the content of the cellulose in the material after the steam explosion treatment (see NREL method for measuring the content of various monosaccharides and lignin in biomass (2004 version)), so as to obtain the cellulose content in the material after the steam explosion treatment; and then mixing a certain amount of the material subjected to steam explosion treatment with water to prepare a feed liquid with a dry matter concentration of 12.6 wt%, carrying out enzymolysis for 72h at the temperature of 50 +/-5 ℃ and the pH value of 10U of cellulase in terms of per gram of cellulose, measuring the glucose amount in the product subjected to enzymolysis, and calculating the enzymolysis conversion rate of the cellulase, wherein the calculation coefficient of the glucose to the cellulose is 1.11, and the enzymolysis conversion rate of the cellulase is the glucose amount in the product subjected to enzymolysis/1.11/corresponding cellulose amount in the material subjected to steam explosion treatment of 100%.
The method for measuring the proportion of the heavy-grade impurities in the dry basis comprises the following steps: firstly, carrying out enzymolysis and fermentation on a material obtained by steam explosion treatment, then sampling a fermented liquor which is uniformly mixed and matured, and detecting the dry basis (absolute dry matter) content by using an infrared moisture meter; similarly, adding water into a certain amount of well-mixed fermented mash, diluting, standing and settling for 30min, removing supernatant, repeating the steps of diluting with water, standing and settling and removing supernatant for 3 times, wherein heavy-grade impurities in the lower-layer liquid are clearly visible; drying the precipitate in a drying oven at 105 ℃, finally putting the dried precipitate in a high-temperature furnace at 800 ℃ for burning until the weight of the precipitate is constant, and weighing the precipitate to obtain the weight of heavy-grade impurities; the proportion of the heavy-grade impurities in the dry basis is the ratio of the weight value of the heavy-grade impurities to the total weight of the dry basis in the corresponding mash, i.e. the proportion of the heavy-grade impurities in the dry basis is 1000 per mill of the weight of the heavy-grade impurities/the total weight of the dry basis.
TABLE 1
As can be seen from the comparison of the data of examples 1-8 and comparative examples 1-2 in Table 1, the method of the invention can greatly improve the recovery rate of hemicellulose and the enzymolysis conversion rate of cellulose, and can also effectively remove impurities, and maximally reduce the influence of the impurities on subsequent links, thereby reducing the consumption of auxiliary materials, reducing the failure rate of equipment, reducing the frequency and intensity of impurity cleaning, and reducing the operation cost.
As can be seen from the comparison of the data of example 1 and example 6 in table 1, the weight ratio of the acid or alkali contained in the material to the dry material in the steam explosion treatment was 0.01 to 0.03: 1, the method can further improve the cellulose enzymolysis conversion rate and has higher hemicellulose recovery rate.
As can be seen from the comparison of the data in the example 1 and the examples 7-8 in the table 1, the method of the present invention can achieve high hemicellulose recovery and utilization rate and high cellulose hydrolysis and conversion rate without the need of high temperature saturated steam explosion treatment, and in the method of the present invention, when the saturated steam explosion treatment is performed, the temperature is 160-170 ℃, the hemicellulose recovery and utilization rate and the cellulose hydrolysis and conversion rate can be further improved.
The pretreatment method of the lignocellulose adopts a mode of combining various treatments, not only can greatly improve the recovery and utilization rate of the hemicellulose and the enzymolysis and conversion rate of the cellulose, but also can effectively remove impurities and maximally reduce the influence of the impurities on subsequent links, thereby reducing the using amount of auxiliary materials, reducing the failure rate of equipment, reducing the frequency and intensity of impurity cleaning and reducing the operation cost.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (16)
1. A method for pretreating lignocellulose, the method comprising: sequentially carrying out rinsing impurity removal treatment, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material, or sequentially carrying out rinsing impurity removal treatment, uniformly mixing treatment with acid-containing or alkali-containing liquid, extrusion dehydration treatment and steam explosion treatment on the lignocellulose raw material; and prior to said press dewatering treatment, the lignocellulosic feedstock is contacted in at least one treatment with an acid-containing or alkali-containing liquid;
the rinsing impurity removal treatment comprises the following steps: mixing the crushed lignocellulose raw material with a first liquid, wherein the first liquid is water or an acid-containing or alkali-containing liquid;
the conditions of the steam explosion treatment comprise: the temperature is 150 ℃ and 175 ℃; the time is 20-80 min.
2. The method of claim 1, wherein the weight ratio of the lignocellulosic feedstock to the first liquid is from 1:5 to 40; the time of rinsing impurity removal treatment is 2-60 min.
3. The method of claim 2, wherein the weight ratio of the lignocellulosic feedstock to the first liquid is from 1:10 to 30; the time for rinsing and impurity removing treatment is 10-45 min.
4. The method of claim 3, wherein the weight ratio of the lignocellulosic feedstock to the first liquid is from 1:15 to 25; the time for rinsing and impurity removing treatment is 15-30 min.
5. The method of claim 1, wherein an embodiment of the press dewatering process comprises: and (3) carrying out extrusion dehydration on the material obtained by rinsing impurity removal treatment or uniformly mixing the material with acid-containing or alkali-containing liquid, and controlling the dry matter content of the material to be more than 30%.
6. The method according to claim 5, wherein the liquid obtained by the squeezing and dewatering treatment is returned to the rinsing and impurity removing treatment and/or the blending treatment with the acid-containing or alkali-containing liquid for recycling.
7. The method of claim 1, wherein the conditions of the steam explosion treatment comprise: the temperature is 160-170 ℃; the time is 40-60 min.
8. The method of claim 1, wherein the method further comprises: and adding an additive into the material obtained by the extrusion dehydration treatment, wherein the additive is an acid-containing or alkali-containing liquid, or an acid gas or an alkali gas.
9. The method of claim 1, wherein the method further comprises: and after the rinsing impurity removal treatment and before the uniform mixing treatment with the acid-containing or alkali-containing liquid, carrying out draining treatment and/or extrusion dehydration treatment on the impurity-removed material.
10. The method according to claim 9, wherein the material obtained from the draining and/or press dewatering process has a dry matter content of 35-50%.
11. The method according to claim 10, wherein the liquid obtained from the draining and/or squeezing dehydration treatment is returned to the rinsing and impurity removing treatment for recycling.
12. The method of claim 1, wherein the method further comprises: and (3) draining impurities precipitated in the rinsing impurity removal treatment, carrying out pollution-free treatment on the precipitate obtained by the draining treatment, and recovering the liquid obtained by the draining treatment and returning the liquid to the rinsing impurity removal treatment for recycling.
13. The method according to any one of claims 1 to 12, wherein the amount of the acid or the base added in the method is controlled so that the weight ratio of the acid or the base contained in the material to the dry material in the steam explosion treatment is 0.001 to 0.05: 1.
14. the method according to claim 13, wherein the amount of the acid or the base added in the method is controlled so that the weight ratio of the acid or the base contained in the material to the dry material in the steam explosion treatment is 0.005-0.04: 1.
15. the method according to claim 14, wherein the amount of the acid or the base added in the method is controlled so that the weight ratio of the acid or the base contained in the material to the dry material in the steam explosion treatment is 0.01-0.03: 1.
16. the method according to any one of claims 1 to 12, wherein the concentration of the acid or base in the acid-or base-containing liquid is from 0.05 to 7 wt.%; the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the alkali is one or more of sodium hydroxide, potassium hydroxide and ammonia water.
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