METHOD FOR THE DETERMINATION OF THE CONTENT OF HEMICELLULOSE, CELLULOSE AND LIGNIN IN BIOMASS AND LI

专利摘要:
Method for determining the content of hemicellulose, cellulose and lignin in biomass and lignocellulosic pastes. The present invention relates to a method for the characterization of lignocellulosic biomass according to their tendency to produce volatile or carbonaceous residues. In this method a new standard or characteristic property of lignocellulosic biomass (herbaceous, wood or pulp) is introduced, the V/C index, measurable by thermogravimetric analysis and which can be correlated with its composition and, consequently, with those characteristics dependent on she. With this invention a fast and cheap determination of the content of hemicellulose, cellulose and lignin of lignocellulosic materials is achieved, in particular those used in the production of pastes, allowing biomass control before entering the digester and paste raw once obtained. (Machine-translation by Google Translate, not legally binding)
公开号:ES2730430A1
申请号:ES201830451
申请日:2018-05-08
公开日:2019-11-11
发明作者:Carmona Jose Ariza；Barneto Agustin Garcia
申请人:Universidad de Huelva；
IPC主号:

专利说明:

[0001]
[0002]
[0003]
[0004] FIELD OF THE INVENTION
[0005]
[0006] The present invention belongs to the technical field of the characterization of materials, more specifically to the determination of the content of hemicellulose, cellulose and lignin in biomass and lignocellulosic pastes.
[0007]
[0008] BACKGROUND OF THE INVENTION
[0009]
[0010] In the scientific community there is agreement about the close relationship between the cellulose content (not hemicellulose) of a wood and its paste yield. Hence the interest in developing fast and cheap analytical systems that allow the analysis of many wood samples. The composition of lignocellulosic biomass can be determined by chemical, chromatographic or spectroscopic analysis. For example, Wright and Wallis (1998) discuss the accuracy of various chemical methods and compare them with high pressure liquid chromatography (Wright, P., Wallis, A. 1998 Rapid determination of cellulose in plantation eucalypt Woods to predict kraft pulp yield TAPPI Journal, February 1998, 126-130). For his part, Schimleck (2007) finds that near infrared spectrometry (NIR) is an alternative to traditional methods of evaluating wood properties and suggests that it will play an important role in future clone selection programs, however alert that the method needs a thorough pre-calibration and that its accuracy is poor for a particular tree and that it should be used not to characterize individuals but populations (Schimleck, L. 2007. Near-Infrared spectroscopy: A rapid non-destructive method for measuring wood properties, and its application to tree breeding. New Zealand Journal of Forestry Science 38,1, 14-35).
[0011]
[0012] We understand by chemical paste that which is obtained from wood by some chemical process of separation of lignin. Historically, chemical methods have been used that occur in acid medium (sulphite paste) or basic medium (soda method, kraft method). Currently the most widespread is the kraft method, which is based on an attack on wood with hydroxide and sodium sulphide (white bleach). The chemical reaction (cooking) takes place in digesters that can be continuous or not. In them, wood and white liquor increase the temperature to a setpoint that is maintained during a stipulated time to get a cellulose paste with previously established characteristics. Currently the control of both the production of pasta and its bleaching is carried out by means of a chemical analysis that determines the oxidizable matter in the paste (kappa number) (number of milliliters of 0.1N potassium permanganate solution that is consumed by 1 gram of pasta) by standard procedures (TAPPI um 235).
[0013]
[0014] The optimization of the pasta production process must take into account both the generation of the raw pasta and its subsequent bleaching. The first seeks to increase the yield of raw pulp and the second to reduce the consumption of bleaching reagents. In this sense it is very important to establish the appropriate level of cooking that allows the optimal operation of the bleaching section. For this, a cutting kappa number is usually used at the exit of the digesters.
[0015]
[0016] Since the organic matter removed in the wood during digestion is used to produce energy by combustion of black liquor and the removal of raw pulp during bleaching has to be treated in the liquid effluent plant, it is not surprising that there is some pressure to decrease as much as possible the kappa number at the output of digesters. In any case, it should be borne in mind that the same kappa number in two pastes does not ensure the same whiteness in them. Experience in producing plants indicates that the cooking of low-yielding wood (for example, Rostrata eucalyptus) should be completed when the pasta has a kappa number 4 or 5 units greater than when high-yield wood is cooked (for example, eucalyptus Globulus)
[0017]
[0018] It is evident, therefore, that the control of the cooking and bleaching processes based on the kappa number is imprecise. Additives (for example, anthraquinone or polysulfides) and changes in the functioning of the digester have been used to improve the digestion process, both aimed at reducing alkaline carbohydrate degradation (isothermal cooking, low solids cooking, ...) and avoid the deposition of xylanes or lignin in the final phase of digestion (for example, if the pH falls below 12.5). On the other hand, in the improvement of bleaching, efforts have been directed towards reducing the environmental impact of the reagents used, oriented towards chlorine-free technologies (TCF) that make use of oxygen, ozone and hydrogen peroxide.
[0019] As indicated, with exceptions, the control system of the cellulose pulp production process revolves around the extent of the degree of delignification achieved. Traditionally this measure has been carried out by redox evaluation and resulted in the kappa number of pasta.
[0020]
[0021] Recently, alternatives based on chromatographic or spectroscopic methods have been proposed. An example is US4944841 which suggests using gas chromatography to control the lignin content in the pulp. However, the most abundant are those that are based on infrared spectroscopy. Some examples of this is US4743339 which monitors black liquor and US7604712 which monitors pulp. In any case, they continue to use the kappa number as a criterion in decision making in the control of the productive process.
[0022]
[0023] Given the difficulty of implementing these expensive control systems, in general cellulose pulp producing plants control the post-cooking process, that is: the analysis of the raw pulp obtained (kappa number) serves to modify the upstream digester conditions (alkalinity, sulphidity, temperature, time). In these facilities the control of the wood is scarce, there are no routine analyzes that evaluate its quality. Instead, specialized departments of the company usually take samples of woods that are purchased in large batches to determine their paste yield under conditions similar to those used in the industrial plant. There are, therefore, catalogs of wood properties that were acquired in large quantities at specific times. This information was useful until that batch of wood was consumed, then lost much of its usefulness.
[0024]
[0025] Wood changes can also be expected after weeks or months in the open in the storage facilities of the processing plants. These changes are not taken into account.
[0026]
[0027] On the other hand, in general, the control of the bleaching process is also carried out afterwards by means of the kappa number of the pastes obtained in the successive stages. It is common for the raw pulp after being subjected to an alkaline scrubbing and washing process to have a kappa number close to 20. In an ECF bleach based on an O-D0-PO-D1 sequence (oxygen delignification, chlorine dioxide, hydrogen peroxide and chlorine dioxide) the kappa number can be reduced to 1 or less. In absolute terms the The greatest decrease takes place in the first stage (O), but in relative terms the most effective are the chlorine dioxide (D0 and D1) stages that can decrease the kappma by more than 60%.
[0028]
[0029] In general terms, it can be verified that the scientific research and the patents described are oriented towards real-time control of the characteristics of black liquor and paste in the digester. This proposal is expensive to implement and expensive to maintain, being hardly justifiable in economic terms if, as proposed in the present invention, there is a control of the characteristics of the wood used as raw material. From the point of view of the present invention, the control of digestion must move towards the wood, since if it is properly characterized the operating conditions in the digester can be easily inferred. In this context, it is necessary to identify the wood and the pulp that is obtained from it by means of a parameter (V / C) that adequately reports its composition, avoiding confusing measures such as the kappa number.
[0030]
[0031] Note the ES2359163T3 patent, which proposes a digestion control system that is not based on the kappa number. It is proposed to analyze the paste at the exit of the digester to determine the proportion that is not soluble in a 5% NaOH solution (called parameter R5). According to the authors of this patent, that parameter R5 can replace the kappa number in the characterization of pastes. The monitoring of pulps with parameter R5 allows to obtain pastes of uniform characteristics even if the wood that feeds the digester is modified.
[0032]
[0033] The purpose is to monitor the pulp content in the pulps, assuming that pulps with similar pulp contents will show similar characteristics when they are transformed into paper.
[0034]
[0035] The aforementioned method measures the amount of cellulose of the raw pulp through the fraction of soluble in 5% NaOH, this being an arbitrary decision, so the reliability of this method is highly questioned, since it is based on correlations Empiricals that are subsequently established.
[0036] DESCRIPTION OF THE INVENTION
[0037]
[0038] The present invention introduces a new standard or characteristic property of lignocellulosic biomass (herbaceous, wood or pulp), the V / C index, measurable by thermogravimetric analysis and which can be correlated with its composition and, consequently, with those characteristics dependent on it such as its ability to produce pasta of a particular kappa or the proper digestion conditions to produce a certain yield. Likewise, parameter V / C finds application in the characterization of cellulose pastes, substituting with advantage the current standard, the kappa number.
[0039]
[0040] With this invention a fast and cheap determination of the content of hemicellulose, cellulose and lignin of lignocellulosic materials is achieved, in particular those used in the production of pastes, allowing biomass control before entering the digester and paste raw once obtained.
[0041]
[0042] The main novelty of the present invention is the characterization of lignocellulosic biomass according to their tendency to produce volatile or carbonaceous residues. For this it is necessary to use thermogravimetric analysis.
[0043]
[0044] In a first aspect of the invention, the method for determining the content of hemicellulose, cellulose and lignin in biomass and lignocellulosic pastes comprises the following steps:
[0045] (a) analyze a sample of biomass and / or lignocellulosic pulp by thermogravimetric analysis;
[0046] (b) represent the thermogravimetric data obtained in step (a) indicating the percentage of mass loss (TG curve) and the rate of mass loss (DTG curve) for each time and temperature;
[0047] (c) perform the calculation of the V / C index from the thermogravimetric data using the formula:
[0048]
[0049] where V is the volatilized sample mass and C is the carbonized sample mass, calculated as C = 100-V;
[0050] (d) determine the amount of hemicellulose, cellulose and lignin in the sample using linear relationships that depend on parameter V / C.
[0051] The data obtained in the method of the invention allow the calculation of the V / C index, the composition of lignocellulosic biomass and the optimal treatment conditions during cooking.
[0052]
[0053] This allows to anticipate the level of severity of the cooking process, avoiding trial and error tests when changing the type of biomass and, consequently, improving the economic balance of the industrial installation. In the case of wood from young crops, the method can be extended to a large number of samples and would allow the establishment of potential cellulose production in adulthood, therefore, it would be useful in the selection of clones in the nursery.
[0054]
[0055] Another aspect of the invention relates to the fact that lignocellulosic biomass and pulp can be wood, cellulose pulp, herbaceous or residual materials.
[0056]
[0057] Another aspect of the invention is the possibility of carrying out the analysis of the lignocellulosic biomass sample of step (a) in an inert or oxidizing atmosphere.
[0058]
[0059] Another aspect of the invention relates to the fact that the analysis of the lignocellulosic biomass sample of step (a) can be carried out at heating rates between 5 and 20 ° C / min, preferably at 10 ° C / min.
[0060]
[0061] Another aspect of the invention is the application of the method at the end of digestion and the successive stages of bleaching of biomass and lignocellulosic pastes.
[0062]
[0063] BRIEF DESCRIPTION OF THE FIGURES
[0064] Figure 1 shows a flow chart of the calibration process of the thermogravimetric system described in the invention.
[0065] Figure 2 shows a flow chart of the determination of the V / C index in biomass and its application in the determination of parameters of interest in the cooking process.
[0066] Figure 3 shows a flow chart of the determination of the V / C index in pasta and its application in the determination of parameters of interest in the cooking and bleaching process. Figure 4 shows a flow chart of one of the preferred embodiments of this invention directed to the data processing modules.
[0067] Figure 5 shows a block diagram of a computer system that automates the calculation modules.
[0068] Figure 6 shows the relationship between parameter V / C (measured in an inert atmosphere) and the cellulose and lignin contents of eucalyptus woods (a and b) and that of cellulose from raw pastes c).
[0069] Figure 7 shows the relationship between the kappa index and the V / C index of pulps obtained from high yield (E2) and low yield (E12) woods.
[0070] Figure 8 shows the linear relationship between the pulp yield of a wood up to kappa number 16 (squares) or 20 (circles) and the parameter V / C in atmosphere a) inert and b) oxidant.
[0071] Figure 9 shows the linear relationship between the active alkali used in cooking and the V / C index of the wood to obtain kappa 16 pastes.
[0072]
[0073] DESCRIPTION OF EMBODIMENTS
[0074] Having described the present invention, it is further illustrated by the following examples.
[0075]
[0076] It is important to note that a calibration process is performed prior to the use of the V / C index. It follows the method 100 described below and whose flow chart is represented in Figure 1.
[0077]
[0078] In step 110 the biomass samples or pastes are subjected to thermogravimetric analysis and their results are used to obtain the V / C index according to procedures 220 and 230 for biomass and 320 and 330 for cellulosic pastes, which will be detailed below.
[0079]
[0080] In step 120 the biomass samples or pastes are subjected to chemical analysis (HPLC, gas chromatography) to determine the content of their main components.
[0081]
[0082] In step 130 the biomass samples will be subjected to cooking with different active alkalis and various H-factor values to produce pastes of preset kappa indices.
[0083] In step 140, the data obtained from thermogravimetric and chemical analyzes will be used to obtain the necessary correlations between the V / C index and the parameters of interest outlined in methods 200 and 300, which will be detailed below.
[0084]
[0085] According to the 100 calibration method of the technique, it can be applied to any other biomass (pine wood, cellulose pulp, herbaceous, etc.) with the following protocol: a) select samples of the biomass of interest that cover a range of sufficiently broad compositions;
[0086] b) chemically analyze these samples to determine the contents of their main components (for example, using HPLC);
[0087] c) perform thermogravimetries in nitrogen and air;
[0088] d) measure parameter V / C; and
[0089] e) correlate cellulose and lignin contents with parameter V / C.
[0090]
[0091] One of the preferred embodiments of this invention is directed to cellulose pulp producing biomass. In it, the V / C index is calculated according to method 200 described below and whose flow chart is represented in Figure 2.
[0092]
[0093] In step 210 of thermogravimetric analysis, a sample of 5-15 mg of biomass is placed in a thermobalance. The thermogravimetric analysis is carried out in nitrogen or air from room temperature to 750 ° C with a heating rate of 10 ° C / min. As a result of this analysis, thermogravimetric data indicating the percentage of mass loss (TG curve) and the rate of mass loss (DTG curve) for each time and temperature will be obtained.
[0094]
[0095] In step 220, the DTG curve is deconvolved. For this, five pseudo-components are used in an inert atmosphere (nitrogen) and seven in an oxidative atmosphere (air).
[0096]
[0097] In the first case (nitrogen) four pseudo-components represent the volatilized fractions of hemicellulose, amorphous cellulose, crystalline cellulose and lignin, and the fifth the volatilized fraction of carbon obtained from the pyrolysis of the previous fractions.
[0098] In the second case (air), four pseudo components represent the volatilized fractions of hemicellulose, amorphous cellulose, crystalline cellulose and lignin, and the other three represent the oxidation of the carbon produced by hemicellulose, cellulose and lignin.
[0099]
[0100] To achieve a good fit, the thermal degradation of the pseudo-components is simulated with autocatalytic kinetics (Prout-Tompkins type):
[0101]
[0102] gives
[0103] ----- = k (1 - car r (í tt m)
[0104] cit
[0105]
[0106] where a represents the degree of conversion, n the order of reaction, m the order of nucleation (measure of the degree of autocatalysis), and k the kinetic constant which, in turn, depends on the frequency factor k ⁰ , the activation energy E and the temperature T according to the equation of
[0107] Arrhenius
[0108]
[0109] Once the initial values of the masses of the pseudo-components and the kinetic parameters have been established (frequency factor, activation energy, reaction order, nucleation order), the deconvolution is achieved through an optimization process in the that the difference between the experimental values provided by the thermogravimetric analysis and the sum of the thermal degradations of the referred pseudo-components is minimized. As a result of this adjustment process, the optimal values of the kinetic parameters and the contents of the pseudo-components in the analyzed sample are obtained, in particular the masses of hemicellulose, amorphous cellulose, crystalline cellulose and lignin that have been volatilized. This process can be done with programs like Matlab or with a spreadsheet.
[0110]
[0111] In step 230 the calculation of the V / C index is carried out. For this, the volatilized sample mass V is first calculated by adding the masses of the first four pseudo-components (they represent the volatilized masses of hemicellulose Hv, amorphous cellulose Cav, crystalline cellulose Ccv and lignin Lv). Then the mass of carbonized sample is calculated: C = 100 - V. In short: V / C = V / (100-V).
[0112]
[0113] In step 240, the hemicellulose, cellulose and lignin contents of the sample are calculated. This calculation can be done in two different ways: by means of the specific carbon productions of each of the biomass components (Method 1), and by means of the V / C index (Method 2).
[0114] Method 1: This method is already known and allows to calculate the amounts of hemicellulose H, cellulose C and lignin L using the masses of volatilized hemicellulose, cellulose and lignin (Hv; Cv and Lv) previously obtained in the thermogravimetric analysis, thus avoiding Calculate parameter V / C as intermediate step. To do this, we should optimize the equation H C L = 100, where H = c1Hv; C = c2 (Ccv + Cav); L = c3Lv, where parameters c1, c2 and c3 represent the intrinsic tendencies of the pseudo-components to form carbon. Taking the initial standard values according to the biomass analyzed, an adjustment procedure similar to that of step 230 can be established to calculate its optimal values and, consequently, the hemicellulose, cellulose and lignin contents in the sample. For this you can use a spreadsheet.
[0115]
[0116] Method 2: In this method, object of the invention, the composition is obtained directly from the V / C index determined in step 230. For this it is necessary to carry out a previous calibration according to method 100 which, after chemical analysis and thermogravimetric of several biomass, allow to establish the constants f1 to f5 of the following linear relationships between the contents of hemicellulose H, cellulose C and lignin L with the index V / C.
[0117] H = f1 + f2 (V / C)
[0118] C = f3 + f4 (V / C)
[0119] L = f5-f6 (V / C)
[0120]
[0121] In step 250, the potential pulp yield of a biomass is calculated from the V / C index.
[0122]
[0123] In step 270, the calculation of the active alkali necessary to obtain a paste of a predetermined kappa index starting from the V / C index is carried out.
[0124]
[0125] In step 260, the calculation of the H index necessary to obtain a paste of a preset kappa index is started from the V / C index.
[0126]
[0127] For the calculations of steps 250, 260 and 270, a previous calibration according to method 100 is necessary.
[0128] Another of the preferred embodiments of this invention is directed to the determination of the V / C index in pasta and its application in the determination of parameters of interest in the cooking and bleaching process. In this example, the V / C index is calculated according to the method 300 described below and whose flow chart is represented in Figure 3.
[0129]
[0130] In step 310 of thermogravimetric analysis, a sample of 5-15 mg of the material to be analyzed is placed in a thermobalance. The thermogravimetric analysis is carried out in nitrogen or air from room temperature to 750 ° C with a heating rate of 10 ° C / min. As a result of this analysis, thermogravimetric data indicating the percentage of mass loss (TG curve) and the rate of mass loss (DTG curve) for each time and temperature will be obtained.
[0131]
[0132] In step 320, the DTG curve is deconvolved. For this, five pseudo-components are used in an inert atmosphere (nitrogen) and seven in an oxidative atmosphere (air).
[0133]
[0134] In the first case (nitrogen) four pseudo-components represent the volatilized fractions of hemicellulose, amorphous cellulose, crystalline cellulose and lignin, and the fifth the volatilized fraction of carbon obtained from the pyrolysis of the previous fractions.
[0135]
[0136] In the second case (air), four pseudo components represent the volatilized fractions of hemicellulose, amorphous cellulose, crystalline cellulose and lignin, and the other three represent the oxidation of the carbon produced by hemicellulose, cellulose and lignin.
[0137]
[0138] To achieve a good fit, the thermal degradation of the pseudo-components is simulated with autocatalytic kinetics (Prout-Tompkins type):
[0139]
[0140]
[0141]
[0142]
[0143] where a represents the degree of conversion, n the order of reaction, m the order of nucleation (measure of the degree of autocatalysis), and k the kinetic constant which, in turn, depends on the frequency factor k ⁰ , the activation energy E and the temperature T according to the equation of
[0144] Arrhenius
[0145]
[0146] Once the initial values of the masses of the pseudo-components and the kinetic parameters have been established (frequency factor, activation energy, reaction order, order of nucleation), the deconvolution is achieved through an optimization process in which the difference between the experimental values supplied by the thermogravimetric analysis and the sum of the thermal degradations of the referred pseudo-components is minimized. As a result of this adjustment process, the optimal values of the kinetic parameters and the contents of the pseudo-components in the analyzed sample are obtained, in particular the masses of hemicellulose, amorphous cellulose, crystalline cellulose and lignin that have been volatilized (Hv , Cav, Ccv, Lv). This process can be done with programs like Matlab or with a spreadsheet.
[0147]
[0148] In step 330, the calculation of the V / C index is carried out. For this, the volatilized sample mass V is first calculated by adding the masses of the first four pseudo-components (they represent the volatilized masses of hemicellulose Hv, amorphous cellulose Cav, crystalline cellulose Ccv and lignin Lv). Then the mass of carbonized sample is calculated: C = 100 - V. In short: V / C = V / (100-V).
[0149]
[0150] In step 340, the contents of hemicellulose, cellulose and lignin in the sample are calculated. This calculation can be done in two different ways: by means of the specific carbon productions of each of the biomass components (Method 1), and by means of the V / C index (Method 2).
[0151]
[0152] Method 1: This method is already known and allows to calculate the amounts of hemicellulose H, cellulose C and lignin L using the masses of volatilized hemicellulose, cellulose and lignin (Hv; Cv and Lv) previously obtained in the thermogravimetric analysis, thus avoiding Calculate parameter V / C as intermediate step. For this, the equation H + C + L = 100 should be optimized, where H = c1Hv; C = c2 (Ccv + Cav); L = c3Lv, where parameters c1, c2 and c3 represent the intrinsic tendencies of the pseudo-components to form carbon.
[0153] Taking the standard initial values according to the biomass analyzed, an adjustment procedure similar to that of step 330 can be established to calculate its optimal values and, consequently, the hemicellulose, cellulose and lignin contents in the sample. For this you can use a spreadsheet.
[0154]
[0155] Method 2: In this method, object of the invention, the composition is obtained directly from the V / C index determined in step 330. For this it is necessary to carry out a previous calibration according to method 100 which, after chemical analysis and thermogravimetric of several biomass, allow to establish the constants f1 to f5 of the following linear relationships between the contents of hemicellulose H, cellulose C and lignin L with the index V / C.
[0156] H = f1 + f2 (V / C)
[0157] C = f3 + f4 (V / C)
[0158] L = f5-f6 (V / C)
[0159]
[0160] In step 350, the kappa index of the paste is calculated from the V / C index.
[0161]
[0162] In step 360, the cellulose crystallinity of the pulp is calculated from the V / C index.
[0163]
[0164] For the calculations of stages 350 and 360, a previous calibration according to method 100 is necessary.
[0165]
[0166] Figure 4 shows a flow chart of one of the preferred embodiments of this invention directed to the data processing modules.
[0167]
[0168] Module 410 receives the thermogravimetric data of biomass and / or cellulosic pastes. Module 420 calculates the V / C index. Module 430 calculates the composition of biomass from the V / C index or from thermogravimetric data and specific carbon productions. Module 440 calculates the composition of pastes from the V / C index or from thermogravimetric data and specific carbon productions. Module 450 calculates the pulp yield of a given biomass. Module 470 calculates the H factor necessary for the cooking of a biomass to produce a paste of the desired characteristics. Module 490 calculates the active alkali necessary for the cooking of a biomass to produce a paste of the desired characteristics. Module 460 calculates the kappa index of a given V / C index paste. Module 480 calculates the crystallinity of a given V / C index paste.
[0169]
[0170] On the other hand, Figure 5 shows a block diagram of a computing system 500 in which the present invention can be implemented.
[0171]
[0172] The computing system has a central processing unit (processor) 520, an input / output interface 530 and a support circuit 540. In certain embodiments of the In the present invention, where the computer system requires a direct human interface, a display 510 and a data input device 550 such as a keyboard or mouse will also be necessary.
[0173]
[0174] The display 510, the data input device 550, the processor 520 and the support circuit 540 will be connected to a bus (digital system that transfers data between the components of a computer or between several computers) which, in turn, will be connected to memory 560. Program storage memories 570 and data 580 may include volatile (RAM) or non-volatile (ROM) memory units and may also contain hard drives and backup storage capacity.
[0175]
[0176] The program storage memory 570 stores the associated software and data modules, and in particular will store the modules 410 to 490 described in Figure 4.
[0177]
[0178] The data storage memory 580 will store the results and other data generated by one or more modules of the present invention. This computer system 500 may be a personal computer, minicomputer, or the like. The computer system 500 supports an operating system, for example, stored in the program storage memory 570 and executed in the processor 520.
[0179]
[0180] Example 1.- Correlation between the composition of eucalyptus wood and its kappa 16 index pastes with the V / C indices.
[0181]
[0182] A selection of wood was made so as to cover the largest possible spectrum of pulp yields after cooking by the kraft method.
[0183] Once subjected to acetone extraction, all samples were subjected to two types of analysis: determination of lignin Klason and HPLC to determine the contents of hemicellulose, cellulose and lignin and thermogravimetry to determine the V / C index according to the procedure previously described For this, 5 mg of each of them were heated in a thermobalance from room temperature to 700 ° C in inert (nitrogen) and oxidative (air) atmospheres. The heating rates were 5, 10 and 20 ° C / min.
[0184]
[0185] It was found that the V / C index maintains a linear relationship with the cellulose and lignin contents of the wood and with the cellulose content of the raw pastes (see figure 6). The data shown in Figure 6 belong to heating rates of 10 ° C / min and inert atmosphere.
[0186]
[0187] Table 1 collects the information obtained from 12 woods of different eucalyptus species and their respective raw kappa pastes 16. Eucalyptus woods are ordered from the highest yield in pulp (E1) to the lowest yield (E12).
[0188]
[0189] Table 1. Parameter V / C (in nitrogen and air) and composition of eucalyptus wood and raw kappa 16 pasta obtained after the cooking process.
[0190]
[0191]
[0192]
[0193] -Cel: Cellulose; Hem: Hemicellulose; Lig: Lignina
[0194] -V / C: quotient between the volatilized and carbonized mass during heating in nitrogen (N) or in air (A).
[0195] -Wood: E1-E8 Globulus; E9-E11 Urograndis; E12 Rostrata.
[0196]
[0197] Once subjected to acetone extraction, all samples were subjected to two types of analysis: determination of lignin Klason and HPLC to determine the contents of hemicellulose, cellulose and lignin and thermogravimetry to determine the V / C index according to the method previously described For this, 5mg of each of them were heated in a thermobalance from room temperature to 700 ° C in inert (nitrogen) and oxidative (air) atmospheres.
[0198] The heating rates were 5, 10 and 20 ° C / min, the exposed data being those obtained with 10 ° C / min. As can be seen, the V / C index maintains a linear relationship with the cellulose and lignin contents of the woods and with the cellulose content of the raw pastes (see figure 6). The exposed data are those corresponding to V / C in an inert atmosphere. Usually the parameter V / C measured in an inert atmosphere changes between 2.0 and 3.5 in the woods and between 3.5 and 5.5 in the pastes, regardless of the origin of the sample analyzed.
[0199]
[0200] As shown in Table 1, the same kappa pastes (16) may have compositions that differ by up to 6% in cellulose or hemicellulose. It has been proven that the pastes of a certain kappa index from low-yielding woods (E11 and E12) that (to eliminate their high lignin contents) have been subjected to high alkalinity in the digester, produce pastes with a higher proportion of cellulose than high performance woods (see table 1).
[0201]
[0202] The high alkalinity that has been used in its production eliminates more lignin at the cost of degrading more carbohydrates, mainly hemicellulose, and producing a paste with lower viscosity. Obviously, these pastes will have different physical properties than those obtained from high-yield wood pulp, which have been obtained with less aggressive alkaline digestions and retain even greater proportion of hemicellulose and a greater degree of cellulose polymerization.
[0203]
[0204] In this regard, it should be borne in mind that the kappa number is a measure of the oxidizable matter present in the paste and that for pulps obtained from hardwoods (eg eucalyptus) the greatest contributions to the total kappa number are made by the residual lignin and hexenuronic acids (HexA) formed during cooking (carbonyl groups may also be important). Since the lignin and HexA contents of the pasta evolve inversely with changes in alkalinity in the digester, it may happen that there are pastes with the same kappa number that belong to two different categories: those with low lignin content and high HexA and those high in lignin and low in HexA. Between both ends fit all intermediate possibilities. In short, obtaining pastes of the same kappa index from different woods does not guarantee to obtain products of the same composition and physical-chemical behavior.
[0205] This fact that has been described is known in the cellulose pulp industry, but in the absence of a new index that solves the shortcomings of the kappa index, the industry must resort to empirical solutions such as those used in plants that have two cooking lines, one specialized in high-performance wood and another in low-performance wood.
[0206]
[0207] In this type of facility it is known that raw pastes of the same kappa number obtained in the two production lines have very different behaviors in the later stages of bleaching and, therefore, if you want to mix those pastes in a common discharge tub In order to feed the subsequent bleaching-bleaching process, it is necessary that the line fed with low-performance wood produces a paste with a number kappa several units higher than that obtained in the line of high-performance wood. In this way, from different woods, process engineers produce pastes of different kappa indices without knowing, until now, that they were producing pastes of the same V / C index.
[0208]
[0209] The method of the invention is supported by the tests performed, such as those shown in Figure 7, in which kappa number 16 paste from a high performance wood (eg Globulus E2) has the same V / C index as a Kappa 21 paste that comes from a low-yield wood such as Rostrata eucalyptus (E12).
[0210]
[0211] Example 2.- Determination of the paste yield of various eucalyptus samples. Thermogravimetric method for the selection of wood based on its paste performance. Usefulness of parameter V / C in the estimation of wood pulp yields of different eucalyptus species.
[0212]
[0213] Table 2. Characterization of the cooking process of different eucalyptus woods and raw pasta obtained according to the established kappa number.
[0214]
[0215]
[0216]
[0217]
[0218]
[0219] -Wood: E1-E8 Globulus; E9-E11 Urograndis; E12 Rostrata.
[0220] -Alcali active: Measures the content of NaOH and Na2S in the white liquor and expresses 10 grams of Na2O in 100mL of white liquor.
[0221] -Pulp yield: Measured as grams of pulp obtained per 100g of treated wood.
[0222]
[0223] As described in the procedure 100 of the present invention, the results obtained by subjecting various eucalyptus woods (of Glóbulus, Urograndis and Rostrata varieties) to cooking with different levels of active alkali are summarized in Table 2. The following variables were stable in all tests: 3.5: 1 hydromodule, 25% sulfide, maximum temperature 165 ° C, temperature rise time 90 minutes, temperature standby time 50 minutes (factor H = 578 ). After each test the following parameters were measured: residual alkali, gross yield, rejection of uncooked foods, kappa index and viscosity of the paste obtained.
[0224]
[0225] For each wood the yield increased as the kappa number of the pulp obtained decreased. In all cases a linear relationship between both parameters was obtained. This allowed to establish by interpolation the active alkali that produces pasta with kappa number 16 or 20. It was also found that: i) the viscosity of the obtained pasta decreased linearly as the active cooking alkali increased, and ii) there was a relationship linear between the viscosity of the paste and the measured yield.
[0226]
[0227] Since both the tendency to produce volatile (or coal) of a wood and its yield in pulp depend on the composition, it is expected that there is some kind of relationship between both variables. Figure 8 shows that this relationship exists and is especially simple: the woods with the highest V / C parameters are also those that produce the highest pulp yield, both for kappa number 16 and for kappa number 20.
[0228]
[0229] In short, cellulose content affects volatile formation and pulp production in the same proportion. This fact is of great interest for the selection of high-performance clones since an alternative to infrared spectroscopy (NIR) would be available as a quick and cheap analysis in the measurement of cellulose content in forest plantations. In this sense, the advantages of thermogravimetry seem obvious since its results are not affected by so many variables.
[0230]
[0231] Example 3.- Determination of the optimal active alkali to obtain a cellulose paste with a preset kappa index.
[0232]
[0233] Figure 9 shows the linear relationship between the active alkali of various cookings and the V / C indices of eucalyptus wood used in obtaining kappa 16 pasta. This fact shows that thermogravimetric control of eucalyptus wood allows establish a priori the optimal operating conditions in the cooking process.
[0234]
[0235] Example 4.- Procedure for the application of thermogravimetric control in the cellulose pulp industry
[0236]
[0237] The application of the thermogravimetric control of wood and cellulose pulps according to the present invention has two great advantages over the current one: i) the company can acquire lumber in the market based on economic criteria since the ignorance of its behavior during the cooking will not imply expensive previous analyzes that guide the engineer during cooking, and ii) the cooking conditions will be set prior to the digestion of the wood, without waiting for subsequent analyzes of the kappa number of the obtained paste to report the necessary changes in active alkali or factor H.
[0238]
[0239] The procedure for the application of the present invention would be the following:
[0240]
[0241] i. Adaptation to the digestion system of the industrial plant
[0242] For its application in a specific industrial installation, the method proposed in the present invention requires a process of adaptation to the cooking procedures used therein.
[0243] The objective would be to introduce the necessary corrections in the already known standard correlations between type of wood, cooking conditions and characteristics of the pulp obtained. Several controlled cooking, made in the factory digesters, applied to the usual woods would be necessary in order to produce the usual pastes. As a final result of this process there will be thermogravimetric data of wood and pulp that will be related to each other by means of cooking processes of each industrial factory. Apply 100 calibration method.
[0244]
[0245] ii. Application in the selection of high performance clones in pulp
[0246] A wooden sample (of the order of milligrams) will be taken to perform the corresponding thermogravimetric analysis and calculate the V / C parameter. The latter will report the cellulose and lignin content and the potential paste yield.
[0247]
[0248] iii. Optimization of digestion conditions
[0249] Once the parameter V / C of the wood has been determined and the adaptation tests to the factory cooking process have been carried out, the control engineer may adopt the appropriate digestion conditions to obtain a V / C paste or preset kappa number. To confirm that the digestion process is operating properly, the thermogravimetric analysis of the raw pastes obtained will be performed. This will confirm that the setpoint of the V / C parameter has been reached and, otherwise, the necessary measures can be taken to achieve it.

权利要求:
Claims (6)
[1]
1. Method for determining the content of hemicellulose, cellulose and lignin in biomass and lignocellulosic pastes, characterized in that it comprises the following steps: (a) analyze a sample of biomass and / or lignocellulosic paste by means of a thermogravimetric analysis;
(b) represent the thermogravimetric data obtained in step (a) indicating the percentage of mass loss (TG curve) and the rate of mass loss (DTG curve) for each time and temperature;
(c) perform the calculation of the V / C index from the thermogravimetric data using the formula:
V / C = V / (100-V)
where V is the volatilized sample mass and C is the carbonized sample mass, calculated as C = 100-V;
(d) determine the amount of hemicellulose, cellulose and lignin in the sample using linear relationships that depend on parameter V / C.
[2]
2. Method according to claim 1, characterized in that the lignocellulosic pulses and pulp are selected from the group comprising wood, cellulose pulp, herbaceous or residual materials.
[3]
3. Method according to claim 1, characterized in that the analysis of the lignocellulosic biomass sample of step (a) can be carried out in an inert or oxidizing atmosphere.
[4]
Method according to claim 1, characterized in that the analysis of the lignocellulosic biomass sample of step (a) can be carried out at heating rates between 5 and 20 ° C / min.
[5]
5. Method according to claim 4, characterized in that the analysis of the lignocellulosic biomass sample of step (a) can be carried out at a heating rate of 10 ° C / min.
[6]
Method according to any one of claims 1 to 5, characterized in that it can be used at the end of digestion and the successive bleaching stages of biomass and lignocellulosic pastes.

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同族专利:

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公开号 | 公开日

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ES2730430B2|2020-05-19|

引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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CN106323796A|2016-10-27|2017-01-11|青岛大学|Method for determining content of chemical composition of lignocellulose plant by adopting thermogravimetric analysis meter|

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ES201830451A|ES2730430B2|2018-05-08|2018-05-08|METHOD FOR THE DETERMINATION OF THE CONTENT OF HEMICELLULOSE, CELLULOSE AND LIGNIN IN BIOMASS AND LIGNOCELLULOSE PASTES|ES201830451A| ES2730430B2|2018-05-08|2018-05-08|METHOD FOR THE DETERMINATION OF THE CONTENT OF HEMICELLULOSE, CELLULOSE AND LIGNIN IN BIOMASS AND LIGNOCELLULOSE PASTES|