Method for determining smoke temperature of combustion chamber outlet of liquid deslagging boiler

Abstract

The invention discloses a method for determining the smoke temperature of a combustion chamber outlet of a liquid-state deslagging boiler and belongs to the technical field of liquid-state deslagging boilers. The method aims at solving the problem that a traditional calculation method for a liquid deslagging boiler combustion chamber is not accurate. The method comprises the steps of firstly calculating combustion product components and smoke characteristics, then performing heat balance calculation according to thermal boundary conditions to obtain boiler thermal efficiency and boiler fuel consumption, then analyzing combustion chamber calculated fuel consumption according to the combustion chamber unburn-off rate, and further calculating effective input heat and theoretical combustion temperature of the combustion chamber. Calculating the effective temperature of flue gas in the combustion chamber and the average heat capacity of combustion products by combining the assumed outlet flue gas temperature of the combustion chamber, and then calculating the thickness of the liquid slag film and the outer surface temperature of the liquid slag film; and calculating new combustion chamber outlet smoke temperature according to the relation between the combustion chamber outlet smoke temperature of the liquid slagging boiler and the relevant parameters obtained by assuming the combustion chamber outlet smoke temperature, and determining the final combustion chamber outlet smoke temperature through iterative calculation.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid slag removal boilers, and particularly relates to a method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slag removal boiler. Background Art

[0002] Liquid slag removal boilers mainly emerged from the 1940s to the 1980s of the last century. The combustion chambers of liquid slag removal boilers adopt cyclone combustion chambers, including vertical cyclones and horizontal cyclones. The development of liquid slag removal boilers in China is relatively late, mostly using vertical cyclone combustion chambers, with small capacity and few in number. Due to problems such as iron precipitation and high-temperature corrosion, and being limited to only low ash fusion point coal types, liquid slag removal boilers have not been widely developed at home and abroad. The combustion heat transfer calculation methods of liquid slag removal boilers are imperfect and unsystematic, and no unified standard method has been formed.

[0003] In recent years, with the large-scale development and utilization of the Zhundong coalfield, the slagging and fouling problems caused by burning Zhundong coal in solid slag removal boilers are particularly prominent. The Zhundong coal has a low ash fusion point temperature, and the content of alkali metal oxides such as calcium, sodium, and potassium in the ash is relatively high. Especially the content of Na2O is mostly above 5%, far exceeding the sodium content level of conventional coal types. Under the high-temperature thermal dynamic conditions in the furnace, after a series of complex physical and chemical changes, serious slagging and fouling problems occur on the heating surfaces of the boiler, affecting the safe and stable operation of the unit and restricting the in-depth development and utilization of Zhundong coal.

[0004] Research shows that the combustion technology of liquid slag removal boilers is a combustion technology with high combustion intensity, high slag capture rate, and low dust content in flue gas. It overcomes the shortcomings of slagging, fouling, and ash accumulation on the furnace water-cooled wall and heating surfaces when solid slag removal boilers burn coal types prone to slagging, and is particularly suitable for high-alkali coal such as Zhundong coal. The high slag capture rate reduces the ash content in the flue gas, and at the same time causes the migration of alkali metals, enabling the decoupling of low-temperature eutectics and fly ash in flue gas, further suppressing slagging and fouling, and having obvious advantages in solving the strong slagging and fouling problems of Zhundong high-alkali coal. However, there is no design and manufacturing experience of large-capacity liquid slag removal boilers at home and abroad. The calculation system of liquid slag removal boilers is imperfect, and traditional calculations of liquid slag removal boilers all adopt relatively rough calculation methods such as estimation, which are only applicable to small-capacity boilers and not applicable to large-capacity liquid slag removal boilers and non-cyclone liquid slag removal boilers. Summary of the Invention

[0005] The present invention aims to solve the problem that the traditional calculation method for the combustion chamber of a liquid slag removal boiler is inaccurate and not applicable to the combustion chambers of large-capacity liquid slag removal boilers and non-cyclone liquid slag removal boilers.

[0006] A method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slag removal boiler includes the following steps:

[0007] Step 1: Calculate the composition of combustion products and flue gas characteristics based on coal quality analysis and excess air coefficient, and then perform a heat balance calculation according to the thermal boundary conditions to obtain the boiler thermal efficiency and boiler fuel consumption.

[0008] Step 2: Based on the boiler fuel consumption, analyze the calculated fuel consumption of the combustion chamber according to the unburned rate in the combustion chamber, and then calculate the effective input heat of the combustion chamber. According to the law of conservation of energy, calculate the theoretical combustion temperature.

[0009] Step 3: First, assume an initial value of the flue gas temperature at the outlet of the combustion chamber. According to the assumed flue gas temperature at the outlet of the combustion chamber and the theoretical combustion temperature, calculate the effective temperature of the flue gas in the combustion chamber and the average heat capacity of the combustion products; according to the effective temperature of the flue gas in the combustion chamber, combined with the structural dimensions of the combustion chamber, the critical temperature of the ash slag and the critical viscosity of the ash slag, calculate the thickness of the liquid slag film and the temperature of the outer surface of the liquid slag film in the complex thermo - dynamic process of gas - liquid - solid multiphase coupled synergistic heat transfer and mass transfer.

[0010] The temperature of the outer surface of the liquid slag film is as follows:

[0011] t zm =C t1 C A C W2 T 2 yx +C t2 C A C W2 T yx +t0

[0012]

[0013] In the formula, T yx is the effective temperature of the flue gas in the combustion chamber; t0 is the critical temperature of the ash slag; C t1 、C t2 are the influence factors of the critical temperature of the ash slag; C A is the influence factor of the thickness of the liquid slag film; C W2 is the influence factor of the secondary air velocity; k” is the coefficient factor; T a is the theoretical combustion temperature expressed in Kelvin; T j is the assumed flue gas temperature at the outlet of the combustion chamber expressed in Kelvin; θ" j is the assumed flue gas temperature at the outlet of the combustion chamber expressed in Celsius.

[0014] Step 4: Calculate a new flue gas temperature at the outlet of the combustion chamber of the liquid - slag - discharging boiler according to the relational formula between the flue gas temperature at the outlet of the combustion chamber and the relevant parameters obtained through the assumed flue gas temperature at the outlet of the combustion chamber, and take it as the assumed flue gas temperature at the outlet of the combustion chamber and return to Step 3. Through iterative calculation, when the difference value of the flue gas temperatures at the outlet of the combustion chamber obtained from the two calculations is less than the threshold value, stop the iteration to obtain the finally determined flue gas temperature at the outlet of the combustion chamber.

[0015] Preferably, the coefficient factor k” is taken as 0.925.

[0016] Furthermore, the excess air coefficient at the combustion chamber outlet is as follows:

[0017]

[0018] In the formula, α l is the excess air coefficient at the furnace outlet; Δα l is the air leakage coefficient of the cooling chamber; Δα ecf is the coefficient of the secondary air entering the cooling chamber; Δα scf is the coefficient of the tertiary air entering the cooling chamber; q 4r is the loss of unburned carbon in the combustion chamber; q4 is the loss of unburned carbon in the boiler.

[0019] Furthermore, the calculated fuel consumption of the combustion chamber is as follows:

[0020]

[0021] In the formula, B gj is the calculated fuel consumption of the boiler; q 4r is the loss of unburned carbon in the combustion chamber; q4 is the loss of unburned carbon in the boiler; Z is the number of operating combustion chambers.

[0022] Furthermore, the thickness of the liquid slag film is as follows:

[0023]

[0024] In the formula, A ar is the ash content of the coal as received; α hz is the slag capture rate of the combustion chamber; μ0 is the critical viscosity of the ash slag; ρ hz is the density of the ash slag; u is the wetted perimeter length of the combustion chamber in contact with the slag; p dl is the flue gas dynamic influence coefficient; B rj is the calculated fuel consumption of the combustion chamber.

[0025] Furthermore, in step 4, the formula for calculating the new flue gas temperature at the combustion chamber outlet based on the relationship between the flue gas temperature at the combustion chamber outlet of the liquid slag removal boiler and the relevant parameters obtained by assuming the flue gas temperature at the combustion chamber outlet is as follows:

[0026]

[0027] In the formula, θ" x is the calculated flue gas temperature at the combustion chamber outlet in degrees Celsius; is the heat preservation coefficient; VC CP is the average specific heat of the combustion chamber flue gas; H fs is the radiant heating surface area of the combustion chamber; α zsis the reduced emissivity; B rj is the calculated fuel consumption of the combustion chamber.

[0028] Furthermore, the reduced emissivity is as follows:

[0029]

[0030] In the formula, α zs is the reduced emissivity, α xs is the radiation absorption characteristic of the liquid slag; χ is the water-cooling coefficient; α hj is the emissivity of the torch.

[0031] Furthermore, the emissivity of the torch is as follows:

[0032] α hj = 1 - e -kps

[0033] where p is the flue gas pressure; s is the radiation layer thickness; k = k RO2 + k ASH + k JT is the flue gas radiation attenuation coefficient, k RO2 is the radiation attenuation coefficient of triatomic gases, k ASH is the radiation attenuation coefficient of ash particles, k JT is the radiation attenuation coefficient of coke particles.

[0034] Furthermore, the radiation attenuation coefficient of triatomic gases, the radiation attenuation coefficient of ash particles, and the radiation attenuation coefficient of coke particles are as follows

[0035] The radiation attenuation coefficient of triatomic gases is as follows:

[0036]

[0037] In the formula, r H2O is the volume fraction of water vapor; p RO2 is the total partial pressure of triatomic gases, kgf / cm 2 ; r RO2 is the total volume fraction of triatomic gases;

[0038] The radiation attenuation coefficient of ash particles is as follows:

[0039]

[0040] In the formula, ρ gas is the flue gas density, kg / m 3 ; μ ash is the ash concentration in the flue gas; d ash is the average diameter of ash particles, μm; The radiation attenuation coefficient of coke particles is as follows:

[0041] KJT = x1x2

[0042] In the formula, x1 is the influence coefficient of fuel type; x2 is the influence coefficient of combustion mode.

[0043] Furthermore, the method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slag removal boiler further includes the following steps:

[0044] Step 5: Determine whether the flue gas temperature at the outlet of the combustion chamber meets the liquid slag removal temperature requirement, that is, the flue gas temperature at the outlet of the combustion chamber of the liquid slag removal boiler should be higher than the ash slag flow temperature + 150°C. If the requirement is met, the calculation ends. If not, the size of the combustion chamber needs to be adjusted and the process returns to Step 3 for recalculation.

[0045] The beneficial effects of the present invention are as follows:

[0046] The present invention constructs the influence relationship of factors such as the viscosity change characteristics of liquid slag with temperature, the amount of liquid slag, and the thickness of the slag film on the flue gas temperature at the outlet of the combustion chamber. By calculating the thickness of the liquid slag film and the outer surface temperature of the liquid slag film in the combustion chamber, the complex heat transfer process in the combustion chamber is simplified to the radiation heat transfer from space to the outer surface of the liquid slag film, and a new method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slag removal boiler is proposed. The present invention can accurately calculate the radiation heat transfer in the combustion chamber, considers the influence of various key factors when calculating the flue gas temperature at the outlet of the combustion chamber, the calculation method is more reasonable, and the degree of coincidence with the measured data is high, indicating that the calculation is more accurate. Moreover, the method of the present invention is applicable to large-capacity liquid slag removal boilers. Description of the Drawings

[0047] Figure 1 It is a flow chart of a method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slag removal boiler. Detailed Embodiments

[0048] The existing calculation of liquid slag boilers only considers the influence of the ash slag melting temperature, simply uses the influence of the ash slag melting temperature on the pollution coefficient, and roughly calculates the heat transfer in the combustion chamber without considering the influence of the ash slag amount, slag capture rate, and different viscosities of the slag on heat transfer. The calculation results are inaccurate and there is a large deviation from the actual operation values. In view of this problem, the present invention constructs the influence relationship between the amount of slag, slag capture rate, and viscosity characteristics of the liquid slag on the thickness and temperature of the slag film on the combustion chamber wall under the influence of the thermal dynamic characteristics in the combustion chamber, calculates the thickness of the flowing slag film covering the combustion chamber wall and the temperature of the outer surface of the slag film, and at the same time considers the influence of the radiation absorption characteristics of the liquid slag on the emissivity, so as to accurately calculate the radiation heat transfer in the combustion chamber. This method for calculating the flue gas temperature at the outlet of the combustion chamber considers the influence of various key factors, the calculation method is more reasonable, and the degree of coincidence with the measured data is high, indicating that the calculation is more accurate and is applicable to large-capacity liquid slag boilers. The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0049] Specific Embodiment 1: In combination with Figure 1 Illustrate this embodiment,

[0050] This embodiment is a method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slag boiler, including the following steps:

[0051] Step 1: According to the coal quality analysis and the excess air coefficient, calculate the components of the combustion products and the flue gas characteristics, and then perform a heat balance calculation according to the thermal boundary conditions to obtain the boiler thermal efficiency and the boiler fuel consumption;

[0052] It is necessary to calculate the composition of combustion products and flue gas characteristics first in order to perform a heat balance calculation using the thermal boundary conditions, and then calculate the thermal efficiency of the boiler and the fuel consumption of the boiler. This process is well-known in the art and will not be elaborated in this invention. It should be noted that: the excess air coefficient in the combustion chamber of a liquid slagging boiler is different from the excess air coefficient at the boiler furnace outlet. In a conventional boiler, all the air is sent into the furnace, and the excess air coefficient at the furnace outlet is a fixed value, unaffected by furnace air leakage and air rate. However, the excess air coefficient at the outlet of the combustion chamber of a liquid slagging boiler is affected by the secondary air, tertiary air volume entering the cooling chamber, and the air leakage in the cooling chamber, and is smaller than the normal excess air coefficient at the furnace outlet. It is necessary to calculate the composition of combustion products and flue gas characteristics separately. But when performing heat balance calculations, boiler efficiency calculations, and boiler fuel consumption calculations, the composition of combustion products and flue gas characteristics corresponding to the normal boiler outlet excess air coefficient still need to be used for calculations. In short, the combustion chamber is upstream of the cooling chamber, and the outlet of the cooling chamber is equivalent to the furnace outlet of a normal boiler. Therefore, all the air directly and actively sent into the cooling chamber or leaking into the cooling chamber does not pass through the combustion chamber, and the excess air coefficient at the outlet of the cooling chamber, that is, the excess air coefficient at the furnace outlet or the total air volume, is a fixed number selected artificially. Therefore, the excess air coefficient at the outlet of the combustion chamber is equal to the excess air coefficient at the furnace outlet minus the coefficient share of various air entering the cooling chamber.

[0053] The excess air coefficient at the outlet of the combustion chamber is calculated according to the following formula:

[0054]

[0055] In the formula, α l is the excess air coefficient at the furnace outlet; Δα l is the air leakage coefficient of the cooling chamber; Δα ecf is the secondary air coefficient entering the cooling chamber; Δα scf is the tertiary air coefficient entering the cooling chamber; q 4r is the unburned carbon loss in the combustion chamber; q4 is the unburned carbon loss of the boiler.

[0056] Step 2: Based on the determined boiler fuel consumption, analyze the calculated fuel consumption of the combustion chamber according to the unburned rate in the combustion chamber, and then calculate the effective input heat of the combustion chamber. According to the law of conservation of energy, calculate the theoretical combustion temperature under the assumption of adiabatic combustion.

[0057] The calculated fuel consumption of the combustion chamber is different from the calculated fuel consumption of the boiler. The fuel does not burn completely in the combustion chamber, and most of the unburned fuel will continue to burn after leaving the combustion chamber. Therefore, the calculated fuel consumption in the combustion chamber is less than the calculated fuel consumption of the boiler, and the number of combustion chambers can be one or more. Therefore, the calculated fuel consumption of the combustion chamber is calculated according to the following formula:

[0058]

[0059] In the formula, B gj is the calculated fuel consumption of the boiler, kg / h; q 4r is the unburned carbon loss in the combustion chamber; q4 is the unburned carbon loss of the boiler; Z is the number of operating combustion chambers.

[0060] The unburned carbon loss in the combustion chamber is different from the unburned carbon loss of the boiler. The unburned carbon loss of the boiler is the final loss of the boiler, and its unburned part will not continue to burn. However, the unburned carbon loss in the combustion chamber is not the final loss of the boiler, and its unburned part will continue to burn after leaving the combustion chamber. Therefore, the unburned carbon loss in the combustion chamber is greater than the unburned carbon loss of the boiler.

[0061] Step 3: The calculation of the flue gas temperature at the outlet of the combustion chamber is a cyclic iterative process. It is necessary to first assume an initial value of the flue gas temperature at the outlet of the combustion chamber. According to the assumed flue gas temperature at the outlet of the combustion chamber (the first iteration is the assumed initial value) and the theoretical combustion temperature, calculate the effective temperature of the flue gas in the combustion chamber and the average heat capacity of the combustion products; according to the effective temperature of the flue gas in the combustion chamber, and combined with the structural dimensions of the combustion chamber, the critical temperature of the ash slag and the critical viscosity of the ash slag, calculate the thickness of the liquid slag film and the temperature on the outer surface of the liquid slag film in the complex thermo-hydrodynamic process of gas-liquid-solid multiphase coupled synergistic heat transfer and mass transfer;

[0062] The thickness of the liquid slag film is related to the amount of ash slag, the density of the slag, the viscosity, the perimeter size, and the flue gas velocity. The calculation formula for the thickness of the liquid slag film is:

[0063]

[0064] In the formula, A ar is the ash content of the coal as received; α hz is the slag capture rate of the combustion chamber. The slag capture rate range of non-cyclone liquid slag removal boilers is 0.4 - 0.6; μ0 is the critical viscosity of the ash slag, kgs / m 2 ; ρ hz is the density of the ash slag, kg / m 3 , usually taken as 2400 kg / m 3 ; u is the wetted perimeter length of the combustion chamber in contact with the slag, m; p dl is the flue gas dynamic influence coefficient.

[0065] The critical viscosity of the ash slag is the viscosity of the ash slag at the critical temperature, which is determined by the viscosity-temperature characteristics of the ash slag. The viscosity of the liquid ash slag decreases with the decrease of temperature. When there is an obvious inflection point on the viscosity-temperature curve, the temperature corresponding to this inflection point is the critical temperature, and the corresponding viscosity is the critical viscosity. This is the key index reflecting the fluidity of the ash slag.

[0066] The flue gas dynamic influence coefficient is related to the coal type and the flue gas velocity. For bituminous coal, p dl The calculation formula is:

[0067] p dl = 0.29w pj 2 - 0.56w pj + 1.45

[0068] Wherein, w pj is the average flue gas velocity, m / s.

[0069] For lignite, p dl The calculation formula is:

[0070] p dl = 0.45w pj 2 - 0.93w pj + 1.66

[0071] The outer surface temperature of the liquid slag film is related to the liquid slag film thickness, the effective temperature of the flue gas in the combustion chamber, the critical temperature of the ash slag, the wind speed, etc. The formula is as follows:

[0072] t zm = C t1 C A C W2 T 2 yx + C t2 C A C W2 T yx + t0

[0073] Wherein, T yx is the effective temperature of the flue gas in the combustion chamber, K; t0 is the critical temperature of the ash slag, °C; C t1 is the critical temperature influence factor 1 of the ash slag; C t2 is the critical temperature influence factor 2 of the ash slag; C A is the liquid slag film thickness influence factor; C W2 is the secondary air velocity influence factor.

[0074] The effective temperature of the flue gas in the combustion chamber is the geometric mean of the theoretical combustion temperature and the assumed flue gas temperature at the outlet of the combustion chamber. The formula is

[0075]

[0076] Wherein, T a is the theoretical combustion temperature, K; T j is the assumed flue gas temperature at the outlet of the combustion chamber, K.

[0077] T j = θ" j + 273

[0078] Wherein, θ" jis the assumed flue gas temperature at the combustor outlet, in °C.

[0079] Meanwhile, an empirical formula for the radiative absorption characteristics of the molten slag and the flame emissivity is established by means of the reduced emissivity; through the reduced emissivity α zs The empirical formula for the radiative absorption characteristics of the molten slag and the flame emissivity is as follows:

[0080]

[0081] In the formula, α xs is the radiative absorption characteristics of the molten slag, representing the effective absorption capacity of the radiation heating surface, and is the experimental data; χ is the water-cooling coefficient; α hj is the flame emissivity.

[0082] The flame emissivity is as follows:

[0083] α hj = 1 - e -kps

[0084] where, k is the radiative attenuation coefficient of the flue gas, 1 / (m·kgf / cm 2 ); p is the flue gas pressure, kgf / cm 2 ; s is the radiation layer thickness, m.

[0085] k = k RO2 + k ASH + k JT

[0086] In the formula, k RO2 is the radiative attenuation coefficient of the triatomic gas, 1 / (m·kgf / cm 2 ); k ASH is the radiative attenuation coefficient of the ash particles, 1 / (m·kgf / cm 2 ); k JT is the radiative attenuation coefficient of the coke particles, 1 / (m·kgf / cm 2 ).

[0087] Radiative attenuation coefficient of the triatomic gas:

[0088]

[0089] In the formula, r H2O is the volume fraction of water vapor; p RO2 is the total partial pressure of the triatomic gas, kgf / cm 2 ; r RO2 is the total volume fraction of the triatomic gas.

[0090] Radiative attenuation coefficient of the ash particles:

[0091]

[0092] Where, ρ gas is the smoke density, kg / m 3 ;μ ash is the concentration of ash in the flue gas; d ash is the average diameter of ash particles, μm.

[0093] The average diameter of ash particles is selected from the following table:

[0094] Combustion equipment Fuel Ash particle diameter μm Chamber furnace, ball mill All fuels 13 Chamber furnace, medium-speed mill or hammer mill All fuels except peat 16 Chamber furnace Peat 24 Cyclone furnace Pulverized coal 10 Cyclone furnace Crushed coal 20 Stoker-fired furnace All fuels 20

[0095] Coke particle radiation attenuation coefficient:

[0096] K JT =x1x2

[0097] Where x1 is the influence coefficient of fuel type, which is 1.0 for low-reactivity fuel and 0.5 for high-reactivity fuel; x2 is the influence coefficient of combustion mode, which is 0.4 for a double-chamber furnace combustion chamber.

[0098] Step 4: Establish a relationship between the flue gas temperature at the combustion chamber outlet of the liquid slag discharge boiler and the relevant parameters obtained by assuming the flue gas temperature at the combustion chamber outlet, calculate the new flue gas temperature at the combustion chamber outlet, and return to step 3 as the assumed flue gas temperature at the combustion chamber outlet. Through iterative calculation, converge the flue gas temperature at the combustion chamber outlet to obtain the final determined flue gas temperature at the combustion chamber outlet.

[0099] The calculation formula for the flue gas temperature at the combustion chamber outlet of a liquid slagging boiler is:

[0100]

[0101] Where, θ" x is the calculated combustion chamber outlet flue gas temperature, °C; is the heat retention coefficient; VC CP is the average specific heat of the flue gas in the combustion chamber, kJ / (kg℃); H fs is the radiation heating area of the combustion chamber, m 2 .

[0102] Compare the combustion chamber outlet flue gas temperatures obtained from the two calculations, which is actually a comparison between the assumed combustion chamber outlet flue gas temperature in the current iteration and the calculated combustion chamber outlet flue gas temperature. When the error is greater than the allowable value, replace the assumed combustion chamber outlet flue gas temperature with the calculated combustion chamber outlet flue gas temperature, and repeat the calculations in steps 3 and 4 until the calculation error is less than the allowable value. The iterative calculation ends, and step 5 is performed at this time.

[0103] Step 5: Determine whether the flue gas temperature at the combustion chamber outlet meets the requirement of liquid slag removal temperature. The flue gas temperature at the combustion chamber outlet of a liquid slag removal boiler should be higher than the ash slag flow temperature + 150°C. If the calculation result meets this condition, the calculation ends. If not, the size of the combustion chamber needs to be adjusted and step 3 should be re-executed for calculation. When the flue gas temperature at the combustion chamber outlet is low, the size of the combustion chamber should be reduced to increase the flue gas temperature at the combustion chamber outlet. When the flue gas temperature at the combustion chamber outlet is much higher than the expected value, the size of the combustion chamber should be enlarged to reduce the flue gas temperature at the combustion chamber outlet until the flue gas temperature at the combustion chamber outlet meets the requirements.

[0104] In this process, the last calculated value in step 4 is used as the accurate value of the flue gas temperature at the combustion chamber outlet and compared with the ash slag flow temperature. If it meets the requirement of being higher than the ash slag flow temperature by more than 150°C, it indicates that the combustion chamber meets the requirement of liquid slag removal and the calculation ends. If not, the size of the combustion chamber needs to be reduced and the calculation should start from step 3 again until the flue gas temperature at the combustion chamber outlet meets the requirements, then the calculation ends.

[0105] The above calculation examples of the present invention are only to illustrate in detail the calculation model and calculation process of the present invention, rather than a limitation on the implementation mode of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to list all the implementation modes here. Any obvious changes or variations derived from the technical solution of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler, characterized in that It includes the following steps: Step 1: Calculate the combustion product components and flue gas characteristics according to the coal quality analysis and the excess air coefficient, and then perform a heat balance calculation based on the thermal boundary conditions to obtain the boiler thermal efficiency and the boiler fuel consumption. Step 2: Based on the boiler fuel consumption, analyze the calculated fuel consumption of the combustion chamber according to the unburned rate of the combustion chamber, and then calculate the effective input heat of the combustion chamber. According to the law of conservation of energy, calculate the theoretical combustion temperature. Step 3: First, assume an initial value of the flue gas temperature at the outlet of the combustion chamber. According to the assumed flue gas temperature at the outlet of the combustion chamber and the theoretical combustion temperature, calculate the effective temperature of the flue gas in the combustion chamber and the average heat capacity of the combustion products; according to the effective temperature of the flue gas in the combustion chamber, and combined with the structural dimensions of the combustion chamber, the critical temperature of the ash slag and the critical viscosity of the ash slag, calculate the thickness of the liquid slag film and the outer surface temperature of the liquid slag film in the complex thermo-dynamic process of gas-liquid-solid multiphase coupling synergistic heat transfer and mass transfer. The outer surface temperature of the liquid slag film is as follows: t zm = C t1 C A C W2 T 2 yx + C t2 C A C W2 T yx + t0 where, T yx is the effective temperature of the flue gas in the combustion chamber; t0 is the critical temperature of the ash; C t1 , C t2 are the influence factors of the critical temperature of the ash; C A is the influence factor of the thickness of the liquid slag film; C W2 is the influence factor of the secondary air velocity; k” is the coefficient factor; T a is the theoretical combustion temperature expressed in Kelvin; T j is the assumed flue gas temperature at the outlet of the combustion chamber expressed in Kelvin; is the assumed flue gas temperature at the outlet of the combustion chamber expressed in Celsius; Step 4: Calculate a new flue gas temperature at the outlet of the combustion chamber according to the relationship between the flue gas temperature at the outlet of the liquid slag removal boiler combustion chamber and the relevant parameters obtained by assuming the flue gas temperature at the outlet of the combustion chamber, and use it as the assumed flue gas temperature at the outlet of the combustion chamber to return to Step 3. Through iterative calculation, when the difference between the flue gas temperatures at the outlet of the combustion chamber obtained by the two calculations is less than the threshold value, stop the iteration to obtain the finally determined flue gas temperature at the outlet of the combustion chamber.

2. The method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler according to claim 1, characterized in that The coefficient factor k” takes 0.

925.

3. A method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler according to claim 1, characterized in that, The excess air coefficient at the outlet of the combustion chamber is as follows: where α l is the excess air coefficient at the furnace outlet; Δα l is the air leakage coefficient of the cooling chamber; Δα ecf is the secondary air coefficient entering the cooling chamber; Δα scf is the tertiary air coefficient entering the cooling chamber; q 4r is the loss of unburned carbon in the combustion chamber; q4 is the loss of unburned carbon in the boiler.

4. The method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler according to claim 1, wherein The calculated fuel consumption of the combustion chamber is as follows: where B gj is the calculated fuel consumption of the boiler; q 4r is the loss of unburned carbon in the combustion chamber; q4 is the loss of unburned carbon in the boiler; Z is the number of operating combustion chambers.

5. The method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler according to claim 1, characterized in that, The thickness of the liquid slag film is as follows: where, A ar is the as-received ash content of coal; α hz is the slag capture rate of the combustion chamber; μ0 is the critical viscosity of ash slag; ρ hz is the density of ash slag; u is the wetted perimeter length of the combustion chamber in contact with the slag; p dl is the flue gas dynamic influence coefficient; B rj is the calculated fuel consumption of the combustion chamber.

6. A method for determining the flue gas temperature at the outlet of a liquid slagging boiler combustion chamber according to any one of claims 1 to 5, characterized in that, The formula for calculating the new flue gas temperature at the outlet of the combustion chamber according to the relationship between the flue gas temperature at the outlet of the liquid slag removal boiler combustion chamber and the relevant parameters obtained by assuming the flue gas temperature at the outlet of the combustion chamber in Step 4 is as follows: Wherein, is the calculated flue gas temperature at the combustor outlet in degrees Celsius; is the heat retention coefficient; VC CP is the average specific heat of the flue gas in the combustor; H fs is the radiant heating surface area of the combustor; α zs is the reduced emissivity; B rj is the calculated fuel consumption of the combustor.

7. A method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler according to claim 6, characterized in that, The reduced emissivity is as follows: where α zs is the reduced emissivity, α xs is the radiation absorption characteristic of the liquid slag; χ is the water-cooling coefficient; α hj is the emissivity of the torch.

8. A method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler according to claim 7, characterized in that, The emissivity of the torch is as follows: α hj ＝1-e -kps Among them, p is the flue gas pressure; s is the thickness of the radiation layer; k = k RO2 + k ASH + k JT is the flue gas radiation attenuation coefficient, k RO2 is the radiation attenuation coefficient of triatomic gases, k ASH is the radiation attenuation coefficient of ash particles, k JT is the radiation attenuation coefficient of coke particles.

9. The method for determining the flue gas temperature at the outlet of the combustion chamber of a liquid slagging boiler according to claim 8, characterized in that, The radiation attenuation coefficient of triatomic gases, the radiation attenuation coefficient of ash particles, and the radiation attenuation coefficient of coke particles are as follows. The radiation attenuation coefficient of triatomic gases is as follows: where r G2O is the volume fraction of water vapor; p RO2 is the total partial pressure of triatomic gases, kgf / cm 2 ; r RO2 is the total volume fraction of triatomic gases; The radiation attenuation coefficient of ash particles is as follows: where ρ gas is the flue gas density, kg / m 3 ; μ ash is the concentration of ash in the flue gas; d ash is the average diameter of ash particles, μm; The radiation attenuation coefficient of coke particles is as follows: K JT = x1x2 In the formula, x1 is the fuel type influence coefficient; x2 is the combustion method influence coefficient.

10. A method for determining the flue gas temperature at the outlet of a liquid slagging boiler combustion chamber according to claim 6, characterized in that, The method further includes the following steps: Step 5: Judge whether the flue gas temperature at the outlet of the combustion chamber meets the requirements of the liquid slag removal temperature, that is, the flue gas temperature at the outlet of the liquid slag removal boiler combustion chamber should be higher than the ash slag flow temperature + 150°C. If the requirements are met, the calculation ends. If not, the size of the combustion chamber needs to be adjusted and the calculation is restarted from Step 3.

Images