CN111724865A

CN111724865A - Bed combustion SO of garbage incineratorXPollutant calculation method

Info

Publication number: CN111724865A
Application number: CN202010434106.8A
Authority: CN
Inventors: 马文超; 刘旭; 马晨; 谷天宝; 王萍; 陈冠益; 钟磊; 颜蓓蓓; 程占军; 林法伟
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2020-05-21
Filing date: 2020-05-21
Publication date: 2020-09-29

Abstract

The invention discloses a bed combustion SO of a garbage incinerator_XThe calculation method of the pollutants comprises the following steps: establishing a control equation based on the N-S equation; according to the steps of garbage combustion, giving a water evaporation reaction equation, a volatile analysis reaction equation, a volatile combustion reaction equation and a fixed carbon combustion reaction equation; establishing boundary conditions including a waste incineration volume change calculation equation, an energy equation of the upper and lower boundaries of a bed layer and a bed layer gas concentration component equation; solving a control equation to obtain the generation and change trend of each pollutant in the waste incineration process. The invention researches five S-type gas pollutants SO₂、SO₃、COS、CS₂、S₂The generation condition on the incineration bed layer; SO under different working conditions is analyzed by developing a calculation method for solid-gas two-phase convection diffusion heat and mass transfer in waste incineration_XThe optimal working condition is explored according to the generation rule and concentration distribution of pollutants, so that suggestions and guidance are provided for the actual operation of the waste incineration grate furnace.

Description

Bed combustion SO of garbage incineratorXPollutant calculation method

Technical Field

The invention relates to a solid waste incineration treatment technology, in particular to SO in a combustion process of a grate bed layer of a waste incineration grate_XAnd (4) a calculation method of the pollutants.

Background

Along with the continuous acceleration of the urbanization process in China, the annual production amount of urban domestic garbage in China is higher and higher, the urban domestic garbage clearing and transporting amount in China in 2017 reaches 2.15 hundred million tons, the urban domestic garbage is increased by about 4.5% in 2016, and the annual garbage yield is increased annually. In order to solve the dilemma of the current city enclosing the garbage, the garbage incineration technology has the advantages of reduction, harmlessness, resource utilization and the like in the garbage treatment, so that the garbage incineration technology is more and more widely applied in China and also becomes a main mode for treating the urban domestic garbage in China. But at the same time, the problem of pollutant discharge caused by the waste incineration process also arouses wide social attention.

SO generated during incineration₂、SO₃The contaminants are the main source of acid rain formation. In addition, the burning process will also form gas H with the odor of rotten eggs₂S and COS, both being highly toxic gases, and wherein H₂S is more toxic, even in trace amounts, H₂S also has strong stimulation to the respiratory tract and eyes of the human body, so the S is particularly critical to the prolapse of the S in the burning process. Finally, another S-type gas CS generated by incineration₂Which is less chemically reactive but can be oxidized to SO by photochemical reaction in the atmosphere₂Also, acid rain is formed, and thus, CS₂To the atmospheric environmentThe resulting hazard is also not negligible. Therefore, how to effectively predict and control SO_XThe generation of gaseous pollutants is particularly important.

The burning process is generally divided into two parts, namely bed gas-solid two-phase burning and gas-phase partial burning in a hearth. Currently, studies on the S model are rare and mostly based on the kinetics of chemical reactions. The SO of the gas phase part of the furnace can be effectively simulated by using FLUENT commercial software_XDistribution of pollutant concentrations, however, these works lack the effect on SO in the gas-solid two-phase on the bed_XThe analysis of contaminants, mostly for pure gas phase processes, is directed to the SO involved_XThe pollutant species and the initial operation condition are less, SO that the respective SO is not needed_XThe change trend of the gas pollutants under multiple working conditions is explored.

Therefore, on the premise that the CFD theory is used as a basis, the MATLAB software is used for programming and solving, the solid waste is assumed to be uniform solid particles, the bed layer part is modeled, and the SO in the bed layer porous medium incineration process is established_XA pollutant distribution model.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide SO in the combustion process of a grate layer of a waste incineration grate_XAnd (4) a calculation method of the pollutants. The invention utilizes MATLAB software to compile codes on the basis of analyzing the operation mechanism of the waste incineration grate furnace. The method adopts a CFD theory, establishes an N-S control equation aiming at the gas phase and the solid phase of a bed layer respectively, disperses the control equation by adopting a central difference and full implicit format, and finally adopts a SIMPLE algorithm to write codes by using MATLAB to calculate. The invention mainly researches five S-type gas pollutants SO through simulation₂、SO₃、COS、CS₂、S₂Formation on the incineration bed. The invention analyzes SO under different working conditions by developing a calculation method for solid-gas two-phase convection diffusion heat and mass transfer in waste incineration_XThe optimal working condition is explored according to the generation rule and concentration distribution of pollutants, so that suggestions and guidance are provided for the actual operation of the waste incineration grate furnace.

The technical scheme adopted by the invention is as follows: bed combustion SO of garbage incinerator_XA method of calculating a contaminant comprising the steps of:

establishing a control equation: establishing a control equation based on the N-S equation, wherein the control equation comprises a mass conservation equation, an energy conservation equation, a momentum conservation equation and a chemical component reaction equation;

mathematical expression of the waste incineration process: according to the steps of garbage combustion, giving a water evaporation reaction equation, a volatile analysis reaction equation, a volatile combustion reaction equation and a fixed carbon combustion reaction equation;

establishing a boundary condition: the boundary conditions comprise a calculation equation of the volume change of the waste incineration, an energy equation of the upper and lower boundaries of the bed layer and a bed layer gas concentration component equation;

solving a control equation to obtain the generation and change trend of each pollutant in the waste incineration process.

Further, the mass conservation equation comprises a mass conservation gas phase control equation and a mass conservation solid phase control equation, the mass conservation gas phase control equation is shown in the formula (1-1), and the mass conservation solid phase control equation is shown in the formula (1-2):

where phi is the porosity of the solid particles in the bed, p_gIs the gas density, p_sDensity of solid particles, U gas flow rate, S_gA source term for the gas phase in the mass conservation equation;

the energy conservation equation comprises an energy conservation gas phase control equation and an energy conservation solid phase control equation, and the energy conservation gas phase control equation and the energy conservation solid phase control equation are both shown in formula (2):

in the formula, C_pgIs the specific heat capacity of the gas, C_psIs the specific heat capacity of a solid, k_effIs the effective thermal conductivity, S, on the bed_TIs the source of the energy conservation equation, and T is the bed temperature;

the momentum conservation equation comprises a momentum conservation gas phase control equation and a momentum conservation solid phase control equation, the momentum conservation gas phase control equation is shown as a formula (3), the momentum conservation solid phase control equation is 0, and 0 represents that solid phase movement is ignored:

in the formula, P is gas pressure, K is the permeability coefficient of the porous medium, beta is a resistance coefficient, and mu is a gas dynamic viscosity coefficient;

the chemical component reaction equation comprises a chemical component reaction gas phase control equation and a chemical component reaction solid phase control equation, wherein the chemical component reaction gas phase control equation is shown as a formula (4-1), and the chemical component reaction gas phase control equation is shown as a formula (4-2):

in the formula, Y_igIs the mass fraction of component i, D_igIs the diffusion coefficient of the component i,

is a source of the mass fraction of component i, p_isIs the density of component i, r_isIs the reaction rate of component i.

Further, the water evaporation reaction equation takes 373K as a demarcation point:

when the bed temperature T <373K, the water evaporation reaction equation is as follows:

R_evp＝A_sh_s(C_w，s-C_w，g) (5)

in the formula, R_evpAs the evaporation rate of water, A_sIs the surface area of the solid particles on the bed, C_w，sWater vapour concentration, C, representing the solid phase in the bed_w，gRepresenting the water vapour concentration of the gas phase in the bed, h_sIs the convective mass transfer coefficient of the gas-solid two phases;

wherein, the convective mass transfer coefficient h of gas-solid two phases_sCalculated according to equation (6):

wherein Sh is a Sheword coefficient, D_gIs the gas diffusion coefficient, d_pIs the particle size of the solid particles, Sc is the Schmidt coefficient, Re is the Reynolds number, p_gIs the gas density, μ is the aerodynamic viscosity coefficient;

wherein the water vapor concentration C is relative to the solid phase in the bed layer_w，sWhen the bed temperature is T, C_w，sIs represented by equation (7):

wherein R is an ideal gas constant;

when the temperature T of the bed layer is more than or equal to 373K, the water evaporation reaction equation is as follows:

R_evp＝Q_cr/H_evp(8)

in the formula, H_evpThe heat quantity, Q, required for the evaporation of the water per unit of the raw material_rTo absorb heat from the outside for evaporating moisture;

wherein the heat Q for evaporating the water is absorbed from the outside_crExpressed by formula (9):

in the formula, S_aIs the specific surface area of the solid particles on the bed,

phi is the porosity of the solid particles on the bed, and sigma is the Stefan-Boltzmann constant, which is 5.67 × 10^-8W/(m²K⁴) Is emissivity coefficient, T_evpIs the boiling temperature of water, h_TIs the heat transfer coefficient of a gas phase and a solid phase, and is calculated according to the formula (10):

where Nu is the Nussel number, k_gIs the thermal conductivity of the gas, Pr is the Planck constant, C_pgIs the specific heat capacity of the gas phase in the bed section of the incinerator.

Further, the volatile analysis reaction equation is as follows:

in the formula, R_vIs the rate of evolution of the volatile component, ρ_sIs the density of solid particles, Y_vIs the mass fraction of the gas of different volatiles in the gas phase, A_vIs an exponential pre-factor, typically of fixed value A_v＝3×10³s^-1，E_vIs the activation energy of the reaction in the course of the volatile analysis, E_v69kJ/mol, R is the ideal gas constant and T is the bed temperature.

Further, the volatile combustion reaction equation is as follows:

r＝min(R_kin，R_mix) (12)

wherein R is the burning rate of the volatile component, R_kinFor the temperature-dependent kinetic reaction rate, R_mixIs the rate of the mixing reaction between the volatile components and air;

wherein the rate R of the mixing reaction between the volatile component and the air_mixAccording to the formula(13) And calculating to obtain:

in the formula, C_mixFor empirical mixing constants, typically 0.5, ρ_gPhi is the porosity of the solid particles on the bed, D_gIs the molecular diffusion coefficient of the volatile component, d_pIs the particle size of the solid particles, U is the gas flow rate, Y_igIs the mass fraction of component i, S_igIs the stoichiometric coefficient of component i, i ═ 1,2, …;

wherein the rate R of the mixing reaction between the volatile component and the air_kinThe calculation is performed by using the arrhenius formula, as shown in formula 14:

in the formula, k is the reaction rate constant in the Arrhenius formula, A is the pre-exponential factor of the volatile combustion reaction, b is the temperature index, [ A ] A]And [ B]Is the molar concentration of substance X, m and n are the number of reaction stages, E_aActivation energy was tested.

Further, the fixed carbon combustion reaction equation is:

C+αO₂→2(1-α)CO+(2α-1)CO₂(15)

wherein α is the reaction coefficient of oxygen, and its value is equal to CO and CO₂Is calculated according to equation (16):

further, the calculation equation of the volume change of the waste incineration is as follows:

where V is the volume of each calculation unit, i.e. each small grid divided, V⁰Is eachAn initial volume of the grid; x is the number of_mIs the conversion of the moisture reaction, x_vIs the conversion of the volatile reaction, x_cIs the conversion of the fixed carbon reaction, x_m、x_v、x_cHas a value of 0 to 1, β_mIs the porous medium shrinkage factor corresponding to water evaporation, β_vIs porous medium shrinkage factor corresponding to volatile matter precipitation, β_cIs the porous medium shrinkage factor corresponding to fixed carbon oxidation, β_m、β_v、β_cThe value of (A) is 0 or 1, the value of 1 is obtained when reaction occurs, and the value of 0 is obtained otherwise;

the energy equation of the upper and lower boundaries of the bed layer is as follows:

in the formula, k_effIs the effective thermal conductivity on the bed, A_sIs the cross-sectional area of the bed, h_TIs the heat transfer coefficient of gas-solid two phases, T_∞Is the ambient temperature, T, of heat transfer to the boundary_radIs the radiation temperature outside the bed boundary, T_sIs the temperature at the surface of the bed,

is the assumed temperature of the boundary layer, generally set to the initial primary wind temperature, and σ is the Stefan-Boltzmann constant, which is 5.67 × 10^-8W/(m²K⁴) And is the emissivity.

The bed gas concentration component equation is as follows:

in the formula, D_igIs the diffusion coefficient of component i, Y_igIs the mass fraction of the component i, h_sIs the convective mass transfer coefficient of the gas-solid two phases, Y_i，∞Is the mass fraction of component i outside the boundary layer, Y_i，sIs the mass fraction of the boundary layer component i.

Further, solving the control equation includes:

step 4-1, inputting initial parameters including the proportions of moisture, volatile matters, fixed carbon and ash in the raw materials, the elements and the proportion of each element in the raw materials, the particle size of solid particles, the density of the solid particles, the void ratio of the solid particles and the gas flow rate;

step 4-2, gridding the calculation area, and dispersing the initial parameters, the control equation and the reaction equation of the waste incineration process into each control grid;

step 4-3, setting the total calculation time, wherein the initial time t is 0, the cycle calculation frequency is n, the initial cycle frequency n is 0, the time calculation interval is dt, and the instantaneous time t is n × dt;

step 4-4, assigning the gas pressure, the gas flow rate, the bed layer temperature and the mass fraction of the component i of the garbage;

step 4-5, solving a momentum conservation equation to obtain the gas flow rate;

step 4-6, the gas flow rate obtained by the solution in the step 4-5 is assigned again;

step 4-7, solving a chemical component reaction equation to obtain the mass fraction of the component i, namely the pollutant content, and solving an energy conservation equation to obtain the bed temperature;

step 4-8, according to the mass fraction and the bed temperature of the component i obtained by the solution in the step 4-7, and re-assigning the mass fraction and the bed temperature of the component i;

4-9, judging whether the gas flow rate, the bed layer temperature and the pollutant content meet the requirement of prediction precision, if so, carrying out the next step, outputting a result and increasing the cycle number n; if not, returning to the step 4-4, assigning values to the gas flow rate calculated in the step 4-5, the bed temperature calculated in the step 4-7 and the mass fraction of the component i, and repeating the steps 4-4 to 4-9;

step 4-10, judging whether the requirement of the total operation time is met, if so, performing the next step and outputting a result, if not, returning to the step 4-4, assigning corresponding parameters according to the gas flow rate calculated in the step 4-5, the bed temperature calculated in the step 4-7 and the mass fraction of the component i, and repeating the steps 4-4 to 4-10;

4-11, finishing and storing the result to perform data sorting analysis to obtain SO in the waste incineration process_XThe generation and the variation trend of pollutants.

Compared with the existing calculation method, the method has obvious technical characteristics and beneficial effects. According to the technical scheme, the invention has the following technical advantages:

1. the invention models the gas-solid two-phase part of the counter bed layer based on the CFD theory and the chemical reaction kinetics theory,

simulate SO_XThe whole process of conversion from solid phase to gas phase involves more SO_XThe related chemical reaction greatly supplements the existing algorithm;

2. the invention defines the assumption of the combustion of the bed layer of the garbage incinerator, simplifies the model, accelerates the calculation speed and improves the calculation efficiency.

3. A large amount of optimization is carried out on the physical and chemical model, the combustion model of the fixed carbon which is more in line with the calculation of S pollutants is used, and the calculation result is more accurate.

Drawings

Fig. 1 is a block diagram of a simulation calculation proposed by the present invention.

FIG. 2 shows a SO system according to the present invention_XA flow chart is calculated.

FIG. 3 is a simulation and experimental results of the calculation method proposed by the present invention at a temperature of 900 ℃ SO₂Results of concentration are compared and compared.

FIG. 4 is a simulation result and an experimental result of the calculation method proposed by the present invention at a temperature of 1000 ℃ for SO₂Results of concentration are compared and compared.

Fig. 5 is a graph showing the time-dependent changes of the respective S-species according to the present invention.

Detailed Description

In order to further understand the contents, features and effects of the present invention, the following embodiments are illustrated and described in detail with reference to the accompanying drawings:

the present invention is based on the following basic assumptions:

1) in the calculation method, the temperatures of gas phase and solid phase in the same grid in the fixed bed are the same, and the same energy equation is adopted for solving;

2) the calculation method adopts a one-dimensional unsteady state model to solve;

3) solid particles deposited on the bed are considered to be homogeneous porous media;

4) the reduction in solid volume is entirely due to mass consumption, ignoring the slow movement of the solid bed that results therefrom;

5) the raw materials in the calculation method mainly comprise C, H, O, N, S five elements;

6) the gas species considered in the calculation method is mainly N₂、O₂、CO、CO₂、H₂、NH₃、CH₄、 H₂O、COS、CS₂、S₂、SO₂、SO₃The components in the solid only contain four conventional components of moisture, volatile components, fixed carbon and ash;

7) the gas-solid two-phase heat exchange is only carried out through convection and radiation, and heat is exchanged between solid phases through conduction and radiation;

8) water evaporation starts to occur only at a specific temperature (373K) and is affected only by temperature;

9) all physical quantities at the same height of the fixed bed are consistent with all physical quantities at the central point of the height, and the heat exchange process of the left boundary and the right boundary is neglected;

10) the gas is considered to be an incompressible ideal gas.

As shown in figure 1, a bed combustion SO of a garbage incinerator_XA method of calculating a contaminant comprising the steps of:

1. establishing a governing equation

According to an energy conservation equation, a mass conservation equation, a momentum conservation equation and a chemical component reaction equation, an N-S control equation is respectively established for a solid phase and a gas phase, and the specific description is shown in an attached table 1.

TABLE 1 control equation

Where the solid phase governing equation in the conservation of momentum equation is 0, 0 means ignoring the slow movement of the solid according to assumption 4).

2. Mathematical expression of waste incineration process

According to four processes of water evaporation, volatile analysis, volatile combustion and fixed carbon combustion which are successively undergone by the garbage in the process of incineration, the reaction and reaction rate in each process are described by a mathematical expression.

(1) The water evaporation reaction equation takes 373K as a demarcation point:

R_evp＝A_sh_s(C_w，s-C_w，g) (5)

wherein R is an ideal gas constant;

R_evp＝Q_cr/H_evp(8)

in the formula, H_evpThe heat quantity, Q, required for the evaporation of the water per unit of the raw material_crTo absorb heat from the outside for evaporating moisture;

(2) The reaction equation of volatilization analysis is as follows:

in the formula, R_vIs the rate of evolution of the volatile component, ρ_sIs the density of solid particles, Y_vFor gases of different volatile components in the gas phaseMass fraction of (A)_vIs an exponential pre-factor, typically of fixed value A_v＝3×10³s^-1，E_vIs the activation energy of the reaction in the course of the volatile analysis, E_v69kJ/mol, R is the ideal gas constant and T is the temperature.

(3) The volatile combustion reaction equation is:

r＝min(R_kin，R_mix) (12)

wherein the rate R of the mixing reaction between the volatile component and the air_mixCalculated according to equation (13):

wherein the rate R of the mixing reaction between the volatile component and the air_kinNamely, the kinetic model is calculated by adopting an Arrhenius formula, which is shown in formula 14:

in the formula, k is the reaction rate constant in the Arrhenius formula, A is the pre-exponential factor of the volatile combustion reaction, b is the temperature index, [ A ] A]And [ B]Is the molar concentration of substance X, m and n are the number of reaction stages, E_aActivation energy was tested. The specific chemical reaction is the reaction equation shown in column 1 of table 2, and the reaction rate of the chemical reaction is specifically described by the reaction rate equation in column 5 of table 2. Reaction schemeAs shown in fig. 2.

Table 2 expression of chemical reaction rate of garbage during incineration process proposed by the present invention

Chemical reaction	A	b	E_a	Equation of reaction rate
					H₂+0.5O₂→H₂O_(g)	6.8×10¹⁵	-1	1.67×10⁸	k[H₂]^0.25[O₂]^1.5
CH₄+1.5O₂→CO+2H₂O_(g)	5.012×10¹¹	0	2×10⁸	k[CH₄]^0.7[O₂]^0.8
					CH₄+H₂O→CO+3H₂	3×10⁸	0	1.26×10⁸	k[CH₄][H₂O]
CO+0.5O₂→CO₂	2.239×10¹²	0	1.702×10⁸	k[CO][O₂]^0.25[H₂O]^0.5
					CO+H₂O→CO₂+H₂	2.75×10⁹	0	8.4×10⁷	k[CO][H₂O]
H₂S+1.5O₂→SO₂+H₂O_(g)	6.5×10¹⁴	0	1.08×10⁴	k[H₂S][O₂]
					SO₂+0.5O₂→SO₃	9.2×10¹⁰	0	8.5×10⁵	k[SO₂][O₂]
SO₃→SO₂+0.5O₂	4.4×10¹¹	0	2.55×10⁷	k[SO₃]
					0.75S₂+H₂O→H₂S+0.5SO₂	31081	0	3.56×10⁴	k[S₂]^0.75[H₂O]
CH₄+2S₂→CS₂+2H₂S	5.53×10¹⁰	0	1.93×10⁴	k[S₂][CH₄]
					CO+0.5S₂→COS	3.18×10⁵	0	5.58×10⁴	k[S₂][CO]
COS→CO+0.5S₂	4.36×10⁹	0	1.8×10⁵	k[COS]
					H₂S→H₂+0.5S₂	3.6×10⁸	0	2.01×10⁵	k[H₂S]

(4) The fixed carbon combustion reaction equation is:

C+αO₂→2(1-α)CO+(2α-1)CO₂(15)

3. establishing boundary conditions

The determination of the boundary conditions is performed for the bottom and top of the calculation method.

Along with the progress of waste incineration, the volume change of the waste changes, and the calculation area changes. The volume change calculation equation of the waste incineration is as follows:

where V is the volume of each calculation unit, i.e. each small grid divided, V⁰Is the initial volume of each mesh; x is the number of_mIs the conversion of the moisture reaction, x_vIs the conversion of the volatile reaction, x_cIs the conversion of the fixed carbon reaction, x_m、x_v、x_cHas a value of 0 to 1, β_mIs the porous medium shrinkage factor corresponding to water evaporation, β_vIs porous medium shrinkage factor corresponding to volatile matter precipitation, β_cIs the porous medium shrinkage factor corresponding to fixed carbon oxidation, β_m、β_v、β_cThe value of (A) is 0 or 1, the value of 1 is obtained when reaction occurs, otherwiseThe value is 0.

The side walls of the reactor are considered to be absolutely insulating with no heat loss inside the bed. At the upper and lower bed boundaries, the energy equation at the upper and lower bed boundaries is shown in equation (18):

The bed gas concentration component equation is shown as formula (19):

in the formula, D_igIs the diffusion coefficient of component i, Y_i，∞Is the mass fraction of component i outside the boundary layer, Y_i，sIs the mass fraction of the boundary layer component i.

4. Solving a governing equation

The solving process is shown in FIG. 1, where P is P in FIG. 1⁰Is at standard atmospheric pressure, U⁰At an initial gas flow rate, T⁰As initial bed temperature, Y⁰Is the initial mass fraction of the gas component, U^*For gas flow rates not achieving accuracy and then re-assigning values, T^*For bed temperatures, Y, which are reassigned after accuracy has not been reached^*The mass fractions of the gas components which are reassigned after the accuracy is not reached, U is the calculated gas flow rate, T is the calculated bed temperature,y is the calculated mass fraction of the gas component. The method specifically comprises the following steps:

step 4-1, inputting initial parameters of the garbage incinerator, including initial parameters of raw materials for experimental verification, wherein the specific parameters are shown in table 4;

step 4-5, solving a momentum conservation equation to obtain the gas flow rate;

step 4-8, according to the bed layer temperature and the mass fraction of the component i obtained by the solution in the step 4-7, and re-assigning the mass fraction of the component i and the bed layer temperature;

4-9, judging whether the gas flow rate, the bed layer temperature and the pollutant content meet the requirement of prediction precision, if so, carrying out the next step, outputting a result and increasing the cycle number n; if not, returning to the step 4-4, assigning values to corresponding parameters according to the gas flow velocity value obtained by calculation in the step 4-5, the bed temperature obtained by calculation in the step 4-7, the mass fraction of the component i and the bed temperature, and repeating the steps 4-4 to 4-9;

step 4-10, judging whether the requirement of the total operation time is met, if so, performing the next step and outputting a result, if not, returning to the step 4-4, assigning corresponding parameters according to the gas flow rate calculated in the step 4-5 and the bed layer temperature, the mass fraction of the component i and the bed layer temperature calculated in the step 4-7, and repeating the steps 4-4 to 4-10;

Examples

Fixed bed refuse incineration is taken as an example. The height of the fixed bed combustion chamber is 1.3m, the inner diameter is 180mm, the experimental raw materials are domestic garbage, and the specific parameters of the raw materials and the experimental working conditions are shown in Table 4.

Table 4 initial parameters of the raw materials of the present invention for experimental verification

Firstly, according to steps 1 to 4 of the inventive content and referring to the hypothesis definition, the raw material parameters, the working condition parameters and the related reaction control equation are input, and the simulation calculation is performed according to the calculation flow shown in fig. 1, and the result is shown in fig. 3 and fig. 4. Wherein the gray curve in the figure is the obtained generated SO₂The black curve is the corresponding experimental result, and SO is compared₂The change trend of the generation amounts at 900 ℃ and 1000 ℃ with time can be found out₂Whether from SO or from the simulation results and the experimental results of₂The generated amount and the time-dependent trend of the product are basically consistent. As shown in FIG. 5, the simulation result of the S-type pollutants also conforms to the actual working conditions, further showing that the calculation method of the invention has a certain degree of accuracy and can be used for the generated SO_XAnd (5) performing simulation prediction on the pollutants.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make many modifications without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. Bed combustion SO of garbage incinerator_XA method of calculating a contaminant, comprising the steps of:

2. A refuse incinerator bed combustion SO as claimed in claim 1_XThe pollutant calculation method is characterized in that the mass conservation equation comprises a mass conservation gas phase control equation and a mass conservation solid phase control equation, the mass conservation gas phase control equation is shown as a formula (1-1), and the mass conservation solid phase control equation is shown as a formula (1-2):

is a source of the mass fraction of component i, p_isAs a function of the density of the component i,r_isis the reaction rate of component i.

3. A refuse incinerator bed combustion SO as claimed in claim 1_XThe pollutant calculation method is characterized in that the water evaporation reaction equation takes 373K as a demarcation point:

R_evp＝A_sh_s(C_w，s-C_w，g) (5)

wherein R is an ideal gas constant;

R_evp＝Q_cr/H_evp(8)

in the formula, H_evpAs raw materialsHeat required for evaporation of water per unit, Q_crTo absorb heat from the outside for evaporating moisture;

4. A refuse incinerator bed combustion SO as claimed in claim 1_XThe pollutant calculation method is characterized in that the volatile analysis reaction equation is as follows:

in the formula, R_vIs the rate of evolution of the volatile component, ρ_sIs the density of solid particles, Y_vIs the mass fraction of the gas of different volatiles in the gas phase, A_vIs an exponential pre-factor, typically of fixed value A_v＝3×10³s^-1，E_vIs the activity of the reaction in the process of volatile analysisConversion of energy, E_v69kJ/mol, R is the ideal gas constant and T is the bed temperature.

5. A refuse incinerator bed combustion SO as claimed in claim 1_XThe pollutant calculation method is characterized in that the volatile component combustion reaction equation is as follows:

r＝min(R_kin，R_mix) (12)

6. A refuse incinerator bed combustion S as claimed in claim 1O_XThe pollutant calculation method is characterized in that the fixed carbon combustion reaction equation is as follows:

C+αO₂→2(1-α)CO+(2α-1)CO₂(15)

7. a refuse incinerator bed combustion SO as claimed in claim 1_XThe pollutant calculation method is characterized in that the calculation equation of the volume change of the waste incineration is as follows:

where V is the volume of each calculation unit, i.e. each small grid divided, V⁰Is the initial volume of each mesh; x is the number of_mIs the conversion of the moisture reaction, x_vIs the conversion of the volatile reaction, x_cIs the conversion of the fixed carbon reaction, x_m、x_v、x_cHas a value of 0 to 1, β_mIs the porous medium shrinkage factor corresponding to water evaporation, β_vIs porous medium shrinkage factor corresponding to volatile matter precipitation, β_cIs the porous medium shrinkage factor corresponding to fixed carbon oxidation, β_m、β_v、β_cThe value of (A) is 0 or 1, the value of 1 is obtained when reaction occurs, and the value of 0 is obtained otherwise;

in the formula, k_effIs the effective thermal conductivity on the bed, A_sIs the cross-sectional area of the bed, h_TIs the heat transfer coefficient of the gas-solid two phases,T_∞is the ambient temperature, T, of heat transfer to the boundary_radIs the radiation temperature outside the bed boundary, T_sIs the temperature at the surface of the bed,

The bed gas concentration component equation is as follows:

8. A refuse incinerator bed combustion SO as claimed in claim 1_XThe method for calculating the pollutants is characterized in that the solving of the control equation comprises the following steps:

step 4-5, solving a momentum conservation equation to obtain the gas flow rate;