A method for predicting the syngas product distribution of a biomass updraft fixed-bed gasifier

Abstract

The application discloses a biomass updraft fixed-bed gasifier synthesis gas product distribution prediction method, comprising the following steps: S1, performing element analysis and industrial analysis on the biomass to obtain main components of the biomass, including cellulose, hemicellulose, lignin and soluble extract; S2, obtaining a temperature distribution of a bed layer according to energy conservation, wherein the bed layer comprises a pyrolysis section, a reduction section and an oxidation section; S3, determining calculation boundary conditions according to furnace type design parameters, biomass mass flow rate, bed layer height, bed layer radius, gasification agent type and flow rate; and S4, calculating product concentration distributions in different stages under the determined calculation boundary conditions according to the main components of the biomass and the obtained bed layer temperature distribution. The prediction method can predict product compositions according to element and industrial analysis of materials, equivalent air ratio and furnace size information, has high speed and certain accuracy, and brings great convenience to furnace design.

Description

Technical Field

[0001] This invention belongs to the field of gasification product distribution prediction technology, specifically relating to a method for predicting the distribution of syngas products in a biomass top-suction fixed-bed gasifier. Background Technology

[0002] With the increasing use of high-carbon fossil energy, the growing problem of climate change has attracted widespread attention. Zero-carbon renewable energy, represented by biomass energy, is the future direction of energy development. Biomass energy utilization technologies mainly fall into two categories: thermochemical conversion and biochemical conversion. Among them, thermochemical methods are more efficient, and biomass gasification is one of the most important thermochemical treatment methods. The main reactors for biomass gasification include updraft gasifiers, downdraft gasifiers, and fluidized beds. Updraft fixed-bed biomass gasifiers hold a very important position in the field of biomass gasification due to their wide adaptability to raw materials and the high hydrogen content in syngas.

[0003] Updraft fixed-bed biomass gasifiers are commonly used biomass gasification reactors in industry. In an updraft gasifier, the material moves downwards while the gas moves upwards, and the material sequentially undergoes drying, pyrolysis, reduction, and oxidation stages. High-temperature gas flows counter-currently with the material; after being heated, dried, and pyrolyzed by the high-temperature gas, the material primarily undergoes a heterogeneous combustion reaction between residual solids and oxygen at the bottom of the furnace. The gasification products mainly include non-condensable syngas (CH4, CO2, CO, and H2, etc.), tar, and solid products, with a relatively complex composition; there is currently no perfect method for predicting the gas phase composition.

[0004] Currently, the main methods for predicting gaseous products in the design of biomass updraft fixed-bed gasifiers include: empirical data, experimental equipment measurements, and existing commercial operating data. However, empirically obtained product distributions generally have large errors, especially for design conditions with large variations, such as air equivalence ratio and raw material composition, where accurate predictions cannot be provided. Equipment testing typically involves laboratory measurements of raw materials. Because laboratory equipment differs significantly from industrial equipment, the measured components cannot be directly used for industrial furnace design and require corrections. These corrections are empirically determined, leading to significant design errors. Furthermore, measuring a large number of components incurs substantial economic costs and is time-consuming. While commercial operating data offers some guidance, it is not applicable to biomass components for which operational data is currently unavailable. Summary of the Invention

[0005] Technical problem solved: In view of the above-mentioned technical problems, the present invention provides a method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier, which can effectively solve the shortcomings of the above-mentioned prediction methods, such as large error, high economic cost and limited guidance.

[0006] Technical solution: A method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier, comprising the following steps:

[0007] S1. Elemental and industrial analysis of biomass revealed that its main components include cellulose, hemicellulose, lignin, and soluble extracts.

[0008] S2. Obtain the temperature distribution of the bed according to the law of energy conservation, wherein the bed includes a pyrolysis section, a reduction section and an oxidation section;

[0009] S3. Based on the furnace design parameters, biomass mass flow rate, bed height, bed radius, gasifying agent type and flow rate, determine the calculation boundary conditions;

[0010] S4. Based on the main components of biomass obtained in step S1 and the bed temperature distribution obtained in step S2, the product concentration distribution at different stages is calculated under the calculation boundary conditions determined in step S3.

[0011] Preferably, the specific process of step S1 is as follows: Elemental and industrial analysis is performed on the biomass to obtain that the main components of the biomass are cellulose, hemicellulose, lignin, and soluble extracts, wherein the chemical formula of cellulose is (C6H2O) 10 O5) x The chemical formula for hemicellulose is (C5H8O4). x Lignin includes H-type, O-type, and C-type lignin, with the chemical formulas C0, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C< 22 H 28 O9, C 20 H 22 O 10 and C 15 H 14 O4; soluble extracts include TGA and TANN, with chemical formulas C10, C20, and C30, respectively. 57 H 100 O7 and C 15 H 12 O7;

[0012] The biomass composition is approximated as three categories: RM1, RM2, and RM3. RM1 consists of 60% cellulose and 40% hemicellulose; RM2 consists of 64% H-type lignin, 16% C-type lignin, and 20% TGA; and RM3 consists of 64% O-type lignin, 16% C-type lignin, and 20% TANN. The formulas for calculating the proportions of the three categories are as follows:

[0013] H=x1*RM1_H+x2*RM2_H+x3*RM3_H (1)

[0014] C=x1*RM1_C+x2*RM2_C+x3*RM3_C (2)

[0015] O=x1*RM1_O+x2*RM2_O+x3*RM3_O (3)

[0016] In the formula, H, C, and O represent the mass fractions of each element in the biomass; RM1_H, RM1_C, and RM1_O represent the mass fractions of H, C, and O in component RM1; RM2_H, RM2_C, and RM2_O represent the mass fractions of H, C, and O in component RM2; RM3_H, RM3_C, and RM3_O represent the mass fractions of H, C, and O in component RM3; and x1, x2, and x3 represent the mass fractions of RM1, RM2, and RM3, respectively.

[0017] Preferably, the temperature distribution of the bed in step S2 is represented as follows:

[0018] The energy balance of the pyrolysis section is shown in equation (4) below:

[0019]

[0020] In the formula, The initial temperature T o Enthalpy of biomass formation at h f，i (T o (T) represents the initial temperature. o The enthalpy of formation of each of the generated components, h i (T p (T) represents the pyrolysis temperature. p The enthalpy of formation of each component, h i (T o (T) represents the pyrolysis temperature. o The enthalpy of formation of each component below, For heat decomposition; among which,

[0021] The calculation method is as follows:

[0022]

[0023] In the formula: MC represents the moisture content in biomass industrial analysis; m B For biomass mass flow rate; h f，DB (T o ) is T o Enthalpy of formation of dry-based biomass at temperature; h f，MC (T o ) is T o The enthalpy of formation of water at temperature;

[0024] h f，DB (T oThe calculation method for ) is as follows:

[0025]

[0026] In the formula: HHV is the higher heating value of biomass; Y C The mass fraction of carbon in biomass elemental analysis; h f，CO2 (T o ) is T o Enthalpy of CO2 formation at temperature Y H This refers to the mass fraction of H in the elemental analysis of biomass. For T o Enthalpy of formation of H2O at temperature (A / F); stoic It is the air equivalent ratio; The enthalpy of formation of O2:

[0027] The calculation method for HHV is as follows:

[0028] HHV=0.3419C+1.1783H+0.1005S-0.10340-0.015N-0.0211Ash (7)

[0029] In the formula, C, H, S, O, N, and Ash represent the mass fractions of each element in biomass element detection and industrial testing, respectively.

[0030] The calculation method is as follows:

[0031]

[0032] In the formula, LHV is the lower heating value of biomass, and ER is the air equivalence ratio; where,

[0033] LHV is calculated as follows:

[0034] LHV = HHV - h fg ×(9Y H +Y MC (9)

[0035] Where: h fg Y is the latent heat of phase transition of H2O; H and Y MC These are the mass fractions of H element and water, respectively.

[0036] The ER calculation method is as follows:

[0037]

[0038] In the formula: This represents the actual mass ratio of air to biomass introduced. The chemical equivalent mass ratio of air to biomass;

[0039] The energy balance of the reduction section is shown in equation (11):

[0040]

[0041] In the formula: h is the enthalpy of formation of air. i (T red ( ) represents the enthalpy of each product in the reduction phase. The heat loss of the reduction section is calculated using the following formula (12):

[0042]

[0043] The energy balance of the oxidation section is shown in equation (13):

[0044]

[0045] Where: h i (T com () represents the enthalpy of each product in the oxidation phase; The heat loss of the oxidation section is calculated using the following formula (14):

[0046]

[0047] Preferably, the product concentration distributions in the pyrolysis, reduction, and oxidation sections are calculated using the mass conservation equation and the component conservation equation, as specifically shown below:

[0048] mass conservation equation:

[0049]

[0050] In the formula, m represents mass, t represents time, in represents inflow, and out represents outflow;

[0051] Component conservation equation:

[0052]

[0053] In the formula, Y k The mass fraction of component k; m k，gen The formation rate in component k is calculated using the following formula:

[0054] m k，gen =Vω k W k (17)

[0055] In the formula, V is the volume, and W k ω is the molecular weight of component k; k The reaction rate of component k is calculated using the following formula:

[0056] ω k =[A][B]K f (18)

[0057] in,

[0058] K f =AT b e -Ea / RT (19)

[0059] In the formula, K f Let A be the chemical reaction rate, T be the temperature, b be the temperature exponent, E be the activation energy, and R be the gas constant.

[0060] During the calculation process, the temperature was kept constant and the flow velocity inside the furnace was approximately constant. Equations (15) and (16) were integrated over time, and the product concentration distribution of the pyrolysis, reduction and oxidation stages was calculated based on the reaction kinetics of different stages.

[0061] Furthermore, the integration time range is the residence time of the medium, and its calculation is shown in equation (20):

[0062]

[0063] In the formula, t is the residence time, L is the length of the reactor, where the length of the pyrolysis section is 0.5L, the length of the reduction section is 0.25L, and the length of the oxidation section is 0.25L; v is the flow velocity of the medium in the reactor, which is calculated as shown in the following formula (21):

[0064] v = V / S (21)

[0065] In the formula, V is the reactor volume, S is the reactor cross-sectional area, and

[0066] V = S * L (22)

[0067] In the integral solution, the time step is calculated as follows:

[0068] dt = t / n (23)

[0069] In the formula, dt is the solution time step, and n is the number of segments.

[0070] Furthermore, the reaction kinetics at different stages are shown below:

[0071] The reaction kinetics of the pyrolysis section are shown in Table 1 below:

[0072] Table 1 Reaction kinetics of the pyrolysis section

[0073]

[0074]

[0075] The reaction kinetics of the reduction and oxidation stages are shown in Table 2 below:

[0076] Table 2 Reaction kinetics of the reduction and oxidation stages.

[0077] REACTIONS CONSIDERED A b E 1. H₂ + 0.5O₂ => H₂O 6.96E+10 0 25.4 2. CH4 + 1.5O2 => CO + 2H2O 1.58E+13 0 40.3 3. C + 2H₂ => CH₄ 4.19E+00 0 4.4 4. CH4 + H2O = CO + 3H2 6.09E+17 0 60.4 5. CO + H₂O = CO₂ + H₂ 2.78E+06 0 2.9 6. C + CO2 => 2CO 2.78E-01 1 9.3 7. CO + 0.5O₂ + OH₂O => CO₂ 2.31E+10 0 38.2 8. C + O₂ => CO₂ 1.20E+10 0 32.3 9.C + 0.5O₂ => CO 2.50E+11 0 38.2 10. C + H₂O => CO + H₂ 2.50E+09 0 52

[0078] Beneficial effects: This invention provides a method for predicting the distribution of syngas products in a biomass top-suction fixed-bed gasifier. It can predict the product composition based on the elemental and industrial analysis of the material, the equivalent air ratio, and the furnace size information. The calculation is more convenient and requires almost no time or economic cost. Using this theory for modeling and calculation can greatly improve the design efficiency of the furnace and save a lot of time and economic costs spent in the testing process. The calculated values ​​are more accurate and are within the allowable error range in engineering. Attached Figure Description

[0079] Figure 1 This is a flowchart illustrating a method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier according to the present invention.

[0080] Figure 2 This is a schematic diagram of the calculation process for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier according to the present invention. Detailed Implementation

[0081] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0082] Example 1

[0083] like Figure 1 As shown, a method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier includes the following steps:

[0084] S1. Elemental and industrial analyses of biomass revealed that its main components include cellulose, hemicellulose, lignin, and soluble extracts; among which, cellulose has the chemical formula (C6H2O). 10 O5) x The chemical formula for hemicellulose (HCELL) is (C5H8O4). x Lignin includes H-type (LIGH), O-type (LIGO), and C-type (LIGC), with chemical formulas C0, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10< / 22 H 28 O9, C 20 H 22 O 10 and C 15 H 14 O4; soluble extracts include TGA and TANN, with chemical formulas C10, C20, and C30, respectively. 57H 100 O7 and C 15 H 12 O7; these seven components account for over 99% of biomass, effectively representing its main components. These seven components can be obtained through testing or calculation, primarily based on chemical element balance. Biomass mainly consists of three elements: C, H, and O. Since biomass comprises seven components, the linear equations derived from element balance are not closed. To reduce the degrees of freedom and make the equations closed and solvable, the biomass composition is approximated as the composition of three categories of substances: RM1, RM2, and RM3. RM1 consists of 60% cellulose and 40% hemicellulose; RM2 consists of 64% H-type lignin, 16% C-type lignin, and 20% TGA; RM3 consists of 64% O-type lignin, 16% C-type lignin, and 20% TANN. The formulas for calculating the proportions of these three categories are as follows:

[0085] C=x1*RM1_C+x2*RM2_C+x3*RM3_C (2)

[0086] O=x1*RM1_O+x2*RM2_O+x3*RM3_O (3)

[0087] In the formula, H, C, and O represent the mass fractions of each element in the biomass; RM1_H, RM1_C, and RM1_O represent the mass fractions of H, C, and O in component RM1; RM2_H, RM2_C, and RM2_O represent the mass fractions of H, C, and O in component RM2; RM3_H, RM3_C, and RM3_O represent the mass fractions of H, C, and O in component RM3; x1, x2, and x3 represent the mass fractions of RM1, RM2, and RM3, respectively; based on the composition of RM1, RM2, and RM3, the mass fractions of the seven substances can be further calculated.

[0088] S2. Obtain the temperature distribution of the bed according to the law of energy conservation, wherein the bed includes a pyrolysis section, a reduction section and an oxidation section;

[0089] The energy balance of the pyrolysis section is shown in equation (4) below:

[0090]

[0091] In the formula, The initial temperature T o Enthalpy of biomass formation at h f，i (T o (T) represents the initial temperature. o The enthalpy of formation of each of the generated components, h i (T p (T) represents the pyrolysis temperature. p The enthalpy of formation of each component, h i(T o (T) represents the pyrolysis temperature. o The enthalpy of formation of each component below, For heat decomposition; among which,

[0092] The calculation method is as follows:

[0093]

[0094] In the formula: MC represents the moisture content in biomass industrial analysis; m B For biomass mass flow rate; h f，DB (T o ) is T o Enthalpy of formation of dry-based biomass at temperature; h f，MC (T o ) is T o The enthalpy of formation of water at temperature;

[0095] h f，DB (T o The calculation method for ) is as follows:

[0096]

[0097] In the formula: HHV is the higher heating value of biomass; Y C The mass fraction of carbon in biomass elemental analysis; h f，CO2 (T o ) is T o Enthalpy of CO2 formation at temperature Y H This refers to the mass fraction of H in the elemental analysis of biomass. For T o Enthalpy of formation of H2O at temperature (A / F); stoic It is the air equivalent ratio; The enthalpy of formation of O2:

[0098] The calculation method for HHV is as follows:

[0099] HHV=0.3419C+1.1783H+0.1005S-0.10340-0.015N-0.0211Ash(7)

[0100] In the formula, C, H, S, O, N, and Ash represent the mass fractions of each element in biomass element detection and industrial testing, respectively.

[0101] The calculation method is as follows:

[0102]

[0103] In the formula, LHV is the lower heating value of biomass, and ER is the air equivalence ratio; where,

[0104] LHV is calculated as follows:

[0105] LHV = HHV - h fg ×(9Y H +Y MC (9)

[0106] Where: h fg Y is the latent heat of phase transition of H2O; H and Y MC These are the mass fractions of H element and water, respectively.

[0107] The ER calculation method is as follows:

[0108]

[0109] In the formula: This represents the actual mass ratio of air to biomass introduced. The chemical equivalent mass ratio of air to biomass;

[0110] The energy balance of the reduction section is shown in equation (11):

[0111]

[0112] In the formula: h is the enthalpy of formation of air. i (T red ( ) represents the enthalpy of each product in the reduction phase. The heat loss of the reduction section is calculated using the following formula (12):

[0113]

[0114] The energy balance of the oxidation section is shown in equation (13):

[0115]

[0116] Where: h i (T com () represents the enthalpy of each product in the oxidation phase; The heat loss of the oxidation section is calculated using the following formula (14):

[0117]

[0118] The product concentration distributions in the pyrolysis, reduction, and oxidation sections are calculated using the mass conservation equation and the component conservation equation, as shown below:

[0119] mass conservation equation:

[0120]

[0121] In the formula, m represents mass, t represents time, in represents inflow, and out represents outflow;

[0122] Component conservation equation:

[0123]

[0124] In the formula, Y k The mass fraction of component k; m k，gen The formation rate in component k is calculated using the following formula:

[0125] m k，gen =Vω k W k (17)

[0126] In the formula, V is the volume, and W k ω is the molecular weight of component k; k The reaction rate of component k is calculated using the following formula:

[0127] ω k =[A][B]K f (18)

[0128] in,

[0129] K f =AT b e -Eα / RT (19)

[0130] In the formula, K f Let A be the chemical reaction rate, T be the temperature, b be the temperature exponent, E be the activation energy, and R be the gas constant.

[0131] During the calculation process, the temperature is kept constant and the flow velocity in the furnace is approximately constant. Equations (15) and (16) are integrated over time. Based on the reaction kinetics of different stages, the product concentration distribution of the pyrolysis section, reduction section and oxidation section is calculated.

[0132] The integration time range is the residence time of the medium, and its calculation is shown in equation (20):

[0133]

[0134] In the formula, t is the residence time, L is the length of the reactor, where the length of the pyrolysis section is 0.5L, the length of the reduction section is 0.25L, and the length of the oxidation section is 0.25L; v is the flow velocity of the medium in the reactor, which is calculated as shown in the following formula (21):

[0135] v = V / S (21)

[0136] In the formula, V is the reactor volume, S is the reactor cross-sectional area, and

[0137] V = S * L (22)

[0138] In the integral solution, the time step is calculated as follows:

[0139] dt=t / n (23)

[0140] In the formula, dt is the solution time step, and n is the number of segments.

[0141] S3. Based on the furnace design parameters, biomass mass flow rate, bed height, bed radius, gasifying agent type and flow rate, determine the calculation boundary conditions; assume that the initial average temperature of each stage is as follows: pyrolysis stage T0_pro is 400-450℃; reduction stage T0_red is 650-700℃; oxidation stage T0_com is 850-900℃.

[0142] S4. Based on the main components of biomass obtained in step S1 and the bed temperature distribution obtained in step S2, the product concentration distribution at different stages is calculated under the calculation boundary conditions determined in step S3.

[0143] Example 2

[0144] like Figure 2 As shown, a method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier is presented. The overall solution process is as follows:

[0145] (1) Based on biomass industrial analysis and elemental analysis, calculate the mass fractions of the three components RM1, RM2 and RM3 by combining equations (1)-(3) in Example 1. Further calculate the mass fractions of the seven components of biomass based on the mass fractions of the three components.

[0146] (2) Obtain furnace design parameters, biomass mass flow rate, bed height, bed cross-sectional area, gasifying agent type and flow rate, etc., as calculation boundary conditions;

[0147] (3) Determine the length of each reaction stage according to the bed height; the pyrolysis stage is 0.5 times the bed height; the reduction stage is 0.25 times the bed height; the gasification stage is 0.25 times the bed height; determine the reactor volume of each stage according to formula (22);

[0148] (4) Assume that the initial average temperature of each stage is divided into: pyrolysis stage T0_pro; reduction stage T0_red; oxidation stage T0_com; use this temperature as the initial temperature for iterative solution; the general value of T0_pro is 400-450℃; the general value of T0_red is 650-700℃; the general value of T0_com is 850-900℃;

[0149] (5) Based on the initial temperature of the pyrolysis section and T0 and the biomass composition obtained in step (1), the boundary conditions are used, and the integration time step dt is determined according to equation (23). Equations (15) and (16) are integrated over the residence time of the pyrolysis section to obtain the product concentration distribution of the pyrolysis section.

[0150] (6) Calculate the apparent enthalpy h of the pyrolysis products based on the T0_pro temperature. i (T p The theoretical apparent enthalpy h is solved using equations (4)-(10). i (T p ) * ; Calculate the error h i (T p ) * -h i (T p );

[0151] (7) Determine the relative error (h) i (T p ) * -h i (T p )) / h i (T p ) * If the fluctuation is within 2%, the initial temperature T0_pro needs to be adjusted. After adjustment, repeat steps (5)-(6) until the error is within a reasonable range. Take the adjusted temperature as the final temperature of the pyrolysis section under this working condition, and the obtained component concentration is the final concentration distribution of the pyrolysis section.

[0152] (8) Obtain the concentration distribution of the pyrolysis products, separate the gaseous CH4, CO, CO2, H2 and tar products, and use the remaining solid products as the inlet components of the oxidation section. In actual furnaces, the solid products first pass through the reduction section and then through the oxidation section. However, since the solid phase reaction is independent of the solid concentration, it is assumed that the solid phase passes through the oxidation section first and then through the reduction section, which makes no significant difference in calculation.

[0153] (9) Using the initial temperature T0 of the oxidation section assumed in step (4) and the solid mass flow rate of the pyrolysis section obtained in step (8) as the initial and boundary conditions, and according to the integral time step dt determined by equation (23), equations (15) and (16) are integrated and solved within the residence time of the oxidation section to obtain the product concentration distribution of the oxidation section.

[0154] (10) Calculate the apparent enthalpy h of the oxidation product based on the T0_com temperature. i (T com The theoretical apparent enthalpy h is solved using equations (13) and (14). i (T com ) * ; Calculate the error h i (T com ) * -h i (T com );

[0155] (11) Determine the relative error (h) i (T com ) * -h i (T com )) / h i (T com ) * If the fluctuation is within 2%, the initial temperature T0_com needs to be adjusted. Then repeat steps (9)-(10) until the error is within this reasonable range. Take the adjusted temperature as the final temperature of the oxidation section under this working condition, and the product concentration distribution as the final concentration distribution of the oxidation section.

[0156] (12) Take the product concentration distribution and the initial temperature T0_red of the reduction section obtained in step (11) as the initial and boundary conditions of the reduction section. According to the integration time step dt determined by equation (23), integrate equations (15) and (16) within the residence time of the reduction section to obtain the product concentration distribution of the reduction section.

[0157] (13) Calculate the apparent enthalpy h of the reduction product based on the T0_red temperature. i (T red The theoretical apparent enthalpy h is solved using equations (11) and (12). i (T red ) * ; Calculate the error h i (T red ) * -h i (T red );

[0158] (14) Determine the relative error (h)i (T red ) * -h i (T red )) / h i (T red ) * If the fluctuation is within 2%, the initial temperature T0_red needs to be adjusted. Then repeat steps (12)-(13) until the error is within this reasonable range. Take the adjusted temperature as the final temperature of the reduction section under this working condition, and the product concentration distribution as the final concentration distribution of the reduction section.

[0159] (15) Separate the solid products and gaseous products obtained from the reduction section. The solid products are the solid residues obtained from the final gasification, and the gaseous products are combined with the gaseous products from the pyrolysis section obtained in step (8). The combined components are the components of the gaseous products obtained from the final gasification.

[0160] Example 3

[0161] Table 3. Elemental and Industrial Analysis of Biomass Materials

[0162] Cad (%) Had (%) Oad (%) Mad (%) Aad(%) Vad(%) Wood chips 49.88 5.72 41.23 10.54 2.68 78.48

[0163] Biomass feed rate: 7 t / h;

[0164] Vaporizing agent: air;

[0165] Air equivalent ratio (ER): 0.25;

[0166] Air intake volume: 8064 m³ / h;

[0167] Furnace body parameters: Furnace body diameter: 3.5m, furnace bed height: 4m;

[0168] Calculation steps:

[0169] (1) Based on the biomass industrial analysis and elemental analysis in Table 3, calculate the mass fractions of the three components RM1, RM2 and RM3 by combining equations (1)-(3). Further calculate the mass fractions of the seven components of biomass based on the mass fractions of the three components, as shown in Table 4.

[0170] Table 4: Biomass Composition

[0171] Element CELL HCELL LIGH LIGC LIGO TGA TANN quality score 0.45 0.21 0.02 0.04 0.19 0.02 0.07

[0172] (2) Determine the calculation boundary conditions based on the furnace design parameters, biomass mass flow rate, bed height, bed radius, gasifying agent type and flow rate;

[0173] (3) The length of each reaction stage is determined based on the bed height; the pyrolysis section is 2m; the reduction section is 1m; the gasification section is 1m; the volume of each stage of the reactor is: pyrolysis section: 19.23m. 3 Restoration section: 9.6m 3 Oxidation section 9.6m 3 ;

[0174] (4) Assume that the initial average temperature of each stage is as follows: pyrolysis stage 400℃; reduction stage 650℃; oxidation stage 850℃;

[0175] (5) Based on the initial temperature of the pyrolysis section and the biomass composition obtained in step (1), the integration time step of 0.01s is determined according to formula (23) to obtain the product concentration distribution of the pyrolysis section.

[0176] (6) Calculate the apparent enthalpy h of the pyrolysis products based on the initial pyrolysis temperature. i (T p The theoretical apparent enthalpy h is solved using equations (4)-(10). i (T p ) * ; Calculate the error h i (T p ) * -h i (T p );

[0177] (7) Determine the relative error (h) i (T p ) * -h i (T p )) / h i (T p ) * The error rate is 16%, which is within the acceptable range. The initial temperature was increased by 10°C each time, and the calculation was performed sequentially. When the temperature reached 540°C, the error was within a reasonable range. 540°C was taken as the pyrolysis temperature, and the product composition at that temperature is considered the final product of the pyrolysis stage.

[0178] (8) The concentration distribution of the pyrolysis products obtained in step (7) is used to separate the gaseous products: CH4, CO, CO2, H2 and tar products. The remaining solid products are used as the inlet boundary of the oxidation section.

[0179] (9) Assuming the initial temperature of the oxidation section is 850℃, the solid mass flow rate of the pyrolysis section obtained in step (8) is used as the boundary condition; according to the integral time step determined by equation (23) is 0.01s, equations (15) and (16) are integrated and solved within the residence time of the oxidation section to obtain the product concentration distribution of the oxidation section.

[0180] (10) Calculate the apparent enthalpy h of the product in the oxidation section based on the temperature of 850℃.i (T com The theoretical apparent enthalpy h is solved using equations (13) and (14). i (T com ) * ; Calculate the error h i (T com ) * -h i (T com Relative error (h) i (T com ) * -h i (T com )) / h i (T com ) * The concentration is 24%. Each time the initial temperature of the oxidation section is increased by 10℃, and after repeated calculations, the final temperature of the oxidation section is 1020℃. The product concentration distribution at this temperature is the final concentration distribution of the oxidation section.

[0181] (11) Take the concentration distribution of all products obtained in step (10) and the initial temperature of the reduction section 650℃ as the initial and boundary conditions of the reduction section. According to the integration time step of 0.01s determined by equation (23), integrate equations (15) and (16) within the residence time of the reduction section to obtain the concentration distribution of products in the reduction section.

[0182] (12) Calculate the apparent enthalpy h of the product in the reduction section based on the temperature of 650℃. i (T red The theoretical apparent enthalpy h is solved using equations (11) and (12). i (T red ) * ; Calculate the error h i (T red ) * -h i (T red ); relative error (h) i (T red ) * -h i (T red )) / h i (T red ) *The initial temperature was increased by 10°C each time, and the calculation was repeated. The final reduction temperature was 840°C. The product distribution at this temperature is the final component distribution of the reduction section. (13) The solid and gaseous products calculated in the reduction section were separated. The solid product is the solid residue obtained from the final gasification. The gaseous product is combined with the gaseous product obtained from the pyrolysis section in step (8). The value is the component distribution of the gaseous product obtained from the final gasification. The calculated gaseous product distribution and the results obtained from the engineering test are shown in Table 5 below:

[0183] Table 5 Gas volume fractions predicted by the model and in industrial trials

[0184] Element [N2] <![CDATA[O2]]> <![CDATA[H2]]> CO <![CDATA[CO2]]> <![CDATA[CH4]]> Model prediction 0.5395 0.0015 0.0723 0.1831 0.1379 0.0646 Industrial trials 0.512 0.001 0.068 0.172 0.148 0.075

[0185] Note: 25℃, 1 atm, dry basis;

[0186] Example 4

[0187] Table 6. Elemental and Industrial Analysis of Biomass Materials

[0188] Detection Cad (%) Had (%) Oad (%) Mad (%) Aad(%) Vad(%) straw 45.21 5.62 36.48 9.67 8.88 72.99

[0189] Biomass feed rate: 7 t / h;

[0190] Vaporizing agent: air;

[0191] Air equivalent ratio (ER): 0.25;

[0192] Furnace body parameters: Furnace body diameter: 3.5m, furnace bed height: 4m;

[0193] The calculation steps are the same as in Example 3. The distribution of the calculated gaseous products and the results obtained from the engineering experiment are shown in Table 7 below:

[0194] Table 7 Gas volume fractions predicted by the model and in industrial trials

[0195] Element <![CDATA[N2]]> <![CDATA[O2]]> <![CDATA[H2]]> CO <![CDATA[CO2]]> <![CDATA[CH4]]> Model prediction 0.5121 0.0011 0.0523 0.2331 0.1642 0.0246 Industrial trials 0.52 0.0008 0.071 0.201 0.184 0.03

[0196] Note: 25℃, 1 atm, dry basis;

[0197] Examples 3 and 4 illustrate that the method of the present invention has good applicability to different types of biomass.

[0198] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier, characterized in that, Includes the following steps: S1. Elemental and industrial analysis of biomass revealed that its main components include cellulose, hemicellulose, lignin, and soluble extracts. S2. The temperature distribution of the bed is obtained based on the law of energy conservation. The bed includes a pyrolysis section, a reduction section, and an oxidation section. Specifically, the temperature distribution of the bed is represented as follows: The energy balance of the pyrolysis section is shown in equation (4) below: In the formula, The initial temperature T o Enthalpy of biomass formation at h f,i (T o (T) represents the initial temperature. o The enthalpy of formation of each of the generated components, h i (T p (T) represents the pyrolysis temperature. p The enthalpy of formation of each component, h i (T o (T) represents the pyrolysis temperature. o The enthalpy of formation of each component below, For pyrolysis, it is calculated using the following formula (8): In the formula, LHV is the lower heating value of biomass, and ER is the air equivalence ratio; The energy balance of the reduction section is shown in equation (11): In the formula: h is the enthalpy of formation of air. i (T red ( ) represents the enthalpy of each product in the reduction phase. The heat loss of the reduction section is calculated using the following formula (12): The energy balance of the oxidation section is shown in equation (13): Where: h i (T com () represents the enthalpy of each product in the oxidation phase; The heat loss of the oxidation section is calculated using the following formula (14): S3. Based on the furnace design parameters, biomass mass flow rate, bed height, bed radius, gasifying agent type and flow rate, determine the calculation boundary conditions; S4. Based on the main components of biomass obtained in step S1 and the bed temperature distribution obtained in step S2, the product concentration distribution at different stages is calculated under the calculation boundary conditions determined in step S3.

2. The method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier according to claim 1, characterized in that, The specific process of step S1 is as follows: Elemental and industrial analysis of the biomass reveals that its main components are cellulose, hemicellulose, lignin, and soluble extracts. The chemical formula of cellulose is (C6H2O). 10 O5) x The chemical formula for hemicellulose is (C5H8O4). x Lignin includes H-type, O-type, and C-type lignin, with the chemical formulas C0, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C2 ... 22 H 28 O9, C 20 H 22 O 10 and C 15 H 14 O4; soluble extracts include TGA and TANN, with chemical formulas C10, C20, and C30, respectively. 57 H 100 O7 and C 15 H 12 O7; The biomass composition is approximated as three categories: RM1, RM2, and RM3. RM1 consists of 60% cellulose and 40% hemicellulose; RM2 consists of 64% H-type lignin, 16% C-type lignin, and 20% TGA; and RM3 consists of 64% O-type lignin, 16% C-type lignin, and 20% TANN. The formulas for calculating the proportions of the three categories are as follows: H=x1*RM1_H+x2*RM2_H+x3*RM3_H (1) C=x1*RM1_C+x2*RM2_C+x3*RM3_C (2) O=x1*RM1_O+x2*RM2_O+x3*RM3_O (3) In the formula, H, C, and O are the mass fractions of each element in the biomass; RM1_H, RM1_C, and RM1_O are the mass fractions of H, C, and O in component RM1; RM2_H, RM2_C, and RM2_O are the mass fractions of H, C, and O in component RM2; RM3_H, RM3_C, and RM3_O are the mass fractions of H, C, and O in component RM3; and x1, x2, and x3 are the mass fractions of RM1, RM2, and RM3, respectively.

3. The method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier according to claim 1, characterized in that: The calculation method is as follows: In the formula: MC represents the moisture content in biomass industrial analysis; m B Biomass mass flow rate; h f,DB (T o ) is T o Enthalpy of formation of dry-based biomass at temperature; h f,MC (T o ) is T o The enthalpy of formation of water at temperature; h f,DB (T o The calculation method for ) is as follows: In the formula: HHV is the higher heating value of biomass; Y C The mass fraction of carbon in biomass elemental analysis; h f,CO2 (T o ) is T o Enthalpy of CO2 formation at temperature Y H This refers to the mass fraction of H in the elemental analysis of biomass. For T o Enthalpy of formation of H2O at temperature (A / F); stoic It is the air equivalent ratio; The enthalpy of formation of O2: The calculation method for HHV is as follows: HHV=0.3419C+1.1783H+0.1005S-0.1034O-0.015N-0.0211Ash(7) In the formula, C, H, S, O, N, and Ash represent the mass fractions of each element in biomass element detection and industrial testing, respectively.

4. The method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier according to claim 1, characterized in that: LHV is calculated as follows: LHV=HHV-h fg ×(9Y H +Y MC ) (9) Where: h fg Y is the latent heat of phase transition of H2O; H and Y MC These are the mass fractions of H element and water, respectively. The ER calculation method is as follows: In the formula: This represents the actual mass ratio of air to biomass introduced. It is the chemical equivalent of the mass ratio of air to biomass.

5. The method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier according to claim 1, characterized in that, The product concentration distributions in the pyrolysis, reduction, and oxidation sections are calculated using the mass conservation equation and the component conservation equation, as shown below: mass conservation equation: In the formula, m represents mass, t represents time, in represents inflow, and out represents outflow; Component conservation equation: In the formula, Y k The mass fraction of component k; m k，gen The formation rate in component k is calculated using the following formula: m k，gen =Vω k W k (17) In the formula, V is the volume, and W k ω is the molecular weight of component k; k The reaction rate of component k is calculated using the following formula: oh k =[A][B]K f (18) in, In the formula, K f Let A be the chemical reaction rate, T be the temperature, b be the temperature exponent, E be the activation energy, and R be the gas constant. During the calculation process, the temperature was kept constant and the flow velocity inside the furnace was approximately constant. Equations (15) and (16) were integrated over time, and the product concentration distribution of the pyrolysis, reduction and oxidation stages was calculated based on the reaction kinetics of different stages.

6. The method for predicting the distribution of syngas products in a biomass updraft fixed-bed gasifier according to claim 5, characterized in that: The integration time range is the residence time of the medium, and its calculation is shown in equation (20): In the formula, t is the residence time, L is the length of the reactor, where the length of the pyrolysis section is 0.5L, the length of the reduction section is 0.25L, and the length of the oxidation section is 0.25L; v is the flow velocity of the medium in the reactor, which is calculated as shown in the following formula (21): v = V / S (21) In the formula, V is the reactor volume, S is the reactor cross-sectional area, and V = S * L (22) In the integral solution, the time step is calculated as follows: dt=t / n (23) In the formula, dt is the solution time step, and n is the number of segments.

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