CN114880919B - Method for calculating optimal internal and external desulfurization proportion of circulating fluidized bed unit - Google Patents
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- 238000006477 desulfuration reaction Methods 0.000 title claims abstract description 151
- 230000023556 desulfurization Effects 0.000 title claims abstract description 151
- 238000000034 method Methods 0.000 title claims abstract description 44
- 235000019738 Limestone Nutrition 0.000 claims abstract description 76
- 239000006028 limestone Substances 0.000 claims abstract description 76
- 239000003245 coal Substances 0.000 claims abstract description 47
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 32
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000003546 flue gas Substances 0.000 claims abstract description 32
- 239000011593 sulfur Substances 0.000 claims abstract description 32
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 32
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000011575 calcium Substances 0.000 claims abstract description 29
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 29
- 239000002002 slurry Substances 0.000 claims abstract description 20
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 5
- 238000005507 spraying Methods 0.000 claims abstract description 4
- 230000005611 electricity Effects 0.000 claims description 19
- 239000010440 gypsum Substances 0.000 claims description 15
- 229910052602 gypsum Inorganic materials 0.000 claims description 15
- JGIATAMCQXIDNZ-UHFFFAOYSA-N calcium sulfide Chemical compound [Ca]=S JGIATAMCQXIDNZ-UHFFFAOYSA-N 0.000 claims description 14
- 230000035772 mutation Effects 0.000 claims description 12
- 238000004364 calculation method Methods 0.000 claims description 9
- 230000002068 genetic effect Effects 0.000 claims description 7
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 claims description 6
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 6
- 230000003009 desulfurizing effect Effects 0.000 claims description 4
- 125000003275 alpha amino acid group Chemical group 0.000 claims description 3
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 3
- 235000010216 calcium carbonate Nutrition 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- XSQUKJJJFZCRTK-UHFFFAOYSA-N urea group Chemical group NC(=O)N XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000000243 solution Substances 0.000 description 5
- 239000003344 environmental pollutant Substances 0.000 description 3
- 238000005457 optimization Methods 0.000 description 3
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- 238000012986 modification Methods 0.000 description 1
- 238000010977 unit operation Methods 0.000 description 1
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Abstract
The invention discloses a method for calculating the optimal internal and external desulfurization proportion of a circulating fluidized bed unit, which comprises the steps of firstly, establishing an internal and external desulfurization comprehensive cost model of the CFB unit, and selecting load, coal quality, coal feeding amount, total air quantity, bed temperature, rated power of a limestone conveying fan, rated power of a slurry circulating pump, limestone feeding flow rate in the furnace, ammonia spraying amount, original flue gas SO 2 concentration and net flue gas SO 2 concentration as input variables; when the comprehensive cost model is established, determining a relational expression of the desulfurization efficiency in the furnace, the load, the molar ratio of calcium to sulfur, the bed temperature and the wind-coal ratio; then, determining SO2 generation concentration by utilizing the input of the comprehensive cost model selected in the step 1, and establishing an in-and-out desulfurization comprehensive cost model under the typical load working condition of the CFB unit after assuming the desulfurization proportion in the furnace; and finally, solving the optimal in-furnace desulfurization proportion under the typical load working condition by utilizing an intelligent optimizing algorithm, and fitting to obtain the optimal in-furnace desulfurization proportion under each load working condition.
Description
Technical Field
The invention belongs to the field of pollutant control optimization of thermal power generating units, and relates to a method for calculating an optimal internal and external desulfurization ratio of a circulating fluidized bed unit.
Background
The Circulating Fluidized Bed (CFB) unit has the advantages of strong combustion stability and low pollutant treatment cost, and can reach the low-emission standard through desulfurization in the furnace, and the process flow is simple. After the ultralow emission standard is provided for pollutant emission of the coal-fired generator set in China, in order to realize ultralow emission, the circulating fluidized bed set is additionally provided with an external desulfurization (flue gas desulfurization) device, and the ultralow emission is realized in a mode of combined desulfurization outside the furnace, wherein the ultralow emission standard of SO 2 is less than or equal to 35mg/m 3. The research on the optimal in-furnace and out-furnace desulfurization proportion of the CFB unit is less at present, and the on-site operation is lack of guidance. On-site operators often ensure that the concentration of SO 2 in raw flue gas at the outlet of a hearth is in a certain fixed range by adjusting the calcium-sulfur ratio of desulfurization in the furnace, and ensure that the emission concentration of SO 2 is lower than 35mg/m 3 after desulfurization outside the furnace. The operation mode is simple, but does not consider the change rule of the desulfurization efficiency and the operation cost in the furnace/outside the furnace under different load working conditions of the unit, so that the desulfurization material consumption of the CFB unit is increased, the desulfurization cost is increased, and the operation economy of the unit is reduced.
Object of the Invention
The invention aims to solve the problems of poor distribution of the internal and external desulfurization proportion of a CFB unit and poor desulfurization operation economy in the prior art, and provides a method for calculating the optimal internal and external desulfurization proportion of the CFB unit.
Disclosure of Invention
The invention provides a method for calculating the optimal internal and external desulfurization proportion of a circulating fluidized bed unit, which comprises the following steps:
Step 1, establishing a comprehensive cost model of internal and external desulfurization of a CFB unit furnace, and selecting load, coal quality, coal feeding amount, total air quantity, bed temperature, rated power of a limestone conveying fan, rated power of a slurry circulating pump, limestone feeding flow rate in the furnace, ammonia spraying amount, original flue gas SO 2 concentration and net flue gas SO 2 concentration as input variables of the comprehensive cost model;
Step 2, determining a relational expression of desulfurization efficiency, load, calcium-sulfur mole ratio, bed temperature and wind-coal ratio in the furnace when the comprehensive cost model is established;
step 3, determining SO 2 generation concentration by utilizing the input of the comprehensive cost model selected in the step 1, and establishing an in-furnace and out-furnace desulfurization comprehensive cost model under the typical load working condition of the CFB unit after assuming the in-furnace desulfurization proportion;
And 4, solving the optimal in-furnace desulfurization ratio under the typical load working conditions by utilizing an intelligent optimizing algorithm, and fitting to obtain the optimal in-furnace desulfurization ratio under each load working condition.
Preferably, the process of establishing the integrated cost model for the in-furnace and out-furnace desulfurization of the CFB unit in the step 1 is as follows: defining the total cost of the combined desulfurization inside and outside the furnace as comprising: the equipment electricity consumption cost, the in-furnace denitration cost, the heat loss cost and the limestone consumption cost are the comprehensive cost which is the total desulfurization cost minus the income generated by gypsum; wherein the limestone consumption cost comprises the consumption cost of the desulfurization limestone in the furnace and the consumption cost of the desulfurization limestone outside the furnace; the equipment electricity consumption cost comprises the electricity consumption of a limestone conveying fan in the furnace and the electricity consumption of a slurry circulating pump outside the furnace; the denitration cost in the furnace increases along with the increase of the molar ratio of the desulfurization calcium and the sulfur in the furnace; when the desulfurization efficiency in the furnace is unchanged, the lower the molar ratio of calcium to sulfur is, the lower the heat loss cost is, and the lower the converted coal consumption is; the dosage of the desulfurization limestone in the furnace is determined by the molar ratio of desulfurization calcium and sulfur in the furnace, the desulfurization efficiency in the furnace and the coal quality, and the desulfurization efficiency in the furnace is related to load, the molar ratio of calcium and sulfur, bed temperature and the wind-coal ratio; the dosage of the off-furnace desulfurization limestone is related to the off-furnace desulfurization efficiency;
Desulfurizing efficiency in the furnace Represented by the following formula (1):
In the formula (1), W c is the coal feeding amount, S ar is the sulfur content, A ir is the total air quantity, k f is the dimensionless flue gas conversion coefficient, Is the concentration of SO 2 in the original flue gas under standard conditions;
Desulfurizing efficiency outside the furnace Represented by the following formula (2):
In the formula (2), under the standard condition Is the concentration of SO 2 in the clean flue gas.
Preferably, in step 2, a relation between the desulfurization efficiency in the furnace and the load, the molar ratio of calcium to sulfur and the bed temperature under a typical load working condition is fitted by a least square method, and the coefficient of the relation is corrected by using the wind-coal ratio, and the method specifically comprises the following substeps:
s21, selecting bed temperature, coal feeding amount, total air quantity, coal quality, raw flue gas SO 2 concentration and limestone feeding flow rate in a furnace under a typical load working condition;
step S22, calculating to obtain the in-furnace desulfurization efficiency, the wind-coal ratio and the calcium-sulfur molar ratio under the typical load working condition, wherein the calculation of the in-furnace desulfurization calcium-sulfur molar ratio is shown by a formula (3):
In the formula (3), the amino acid sequence of the compound, The purity of the limestone is used for preparing the limestone,A limestone feed flow rate into the furnace;
Step S23, fitting a relation between the desulfurization efficiency in the furnace and the molar ratio of calcium to sulfur and the bed temperature under a typical load working condition by adopting a least square method, wherein the relation is expressed as shown in a formula (4):
In the formula (4), A is a dimensionless coefficient, B is a function of bed temperature, and m CFB is the molar ratio of calcium to sulfur in the furnace;
and S24, correcting A by using the wind-coal ratio under the typical load working condition according to the operation data, and finally obtaining a relational expression of the desulfurization efficiency in the furnace, the molar ratio of calcium to sulfur and the bed temperature under the typical load working condition.
Preferably, in step 3, after assuming the desulfurization proportion in the furnace, the power consumption of a limestone conveying fan, the power consumption of a slurry circulating pump and the limestone consumption of desulfurization inside and outside the furnace are determined, wherein the power consumption of the limestone conveying fan is determined by the feeding flow rate of limestone in the furnace and the rated power of the limestone conveying fan, the power consumption of the slurry circulating pump is determined by the number of circulating pumps put into operation and the rated power, and the method specifically comprises the following substeps:
And S31, fitting the relation between the desulfurization efficiency outside the furnace and the concentration of SO 2 in the raw flue gas and the total air quantity by a least square method, wherein the relation is shown as a formula (6):
in the formula (6), a 1、a2、a3 is a model coefficient;
Step S32, assuming that the in-furnace desulfurization proportion is x under a certain typical load working condition, the out-of-furnace desulfurization proportion is 1-x, and combining the formula (1) and the formula (4), determining the calcium-sulfur molar ratio m CFB of the in-furnace desulfurization;
And a substep S33, wherein the limestone consumption cost W 1 in the furnace is expressed as the formula (7):
In the formula (7), M CaCO3、MCao is the relative molecular mass of CaCO 3 and CaO respectively, and the unit is g/mol; u1 is the unit price of limestone in the furnace, and the unit is yuan/kg;
The heat loss cost W 2 is expressed as shown in the formula (8):
W2＝Wc[η/(η-Δη)-1]u2 (8)，
In the formula (8), η is the boiler design efficiency; Δη is boiler heat loss; u 2 is the unit price of the fire coal in yuan/kg;
the denitration cost W 3 is expressed as shown in formula (9):
W3＝k1mCFBWcu3 (9)，
In formula (9), k 1 is a cost factor; u 3 is urea unit price in yuan/kg;
and the power consumption cost W 4 of the conveying fan is expressed as shown in a formula (10):
In the formula (10), alpha is the compressed air coefficient; u 4 is the electricity price of the internet, and the unit is Yuan/kWh;
The out-of-furnace limestone usage cost W 5 is expressed as shown in formula (11):
in the formula (11), m CFB and wet are the molar ratio of calcium to sulfur outside the furnace; u 5 is the unit price of the limestone outside the furnace, and the unit is yuan/t.
The power consumption W 6 of the circulating pump is expressed as shown in a formula (12):
In the formula (12), n is the number of started slurry circulating pumps and is determined by the concentration and load of the raw flue gas SO 2; p w is the power of a single slurry circulating pump, and the unit is kW;
the gypsum gain V 7 is expressed as shown in formula (13):
Wherein eta (H 2 O) is the water content of gypsum; u 8 is the unit price of gypsum in yuan/kg;
the combined desulfurization integrated cost f (x) inside and outside the furnace is expressed as shown in a formula (14):
f(x)W1+W2+W3+W4+W5+W6-V7 0≤X≤Xmax(14)，
In the formula (14), W 1、W2、W3、W4、W5、W6、V7 is determined by the desulfurization proportion x in the furnace, and is respectively the limestone consumption cost, heat loss cost, denitration cost, conveying fan electricity consumption cost, the limestone consumption cost outside the furnace, circulating pump electricity consumption and gypsum income; xma x is determined by the desulfurization capacity in the furnace of the CFB unit.
Preferably, in step 4, the optimal in-furnace desulfurization proportion under the typical load condition is a solution obtained by optimizing the minimum comprehensive cost of in-furnace desulfurization and out-furnace desulfurization by a genetic algorithm, wherein the genetic algorithm optimization process comprises the following substeps:
substep S41, encoding: selecting an unsigned binary integer to represent an individual x i;
substep S42, generating an initial population: randomly generating N individuals as an initial group, and setting the iteration number as N;
Substep S43, fitness calculation: using the integrated cost function value g (x i) as fitness of the individual x i, a fitness function as shown in formula (15) is selected:
g(xi)＝minf(xi) (15)；
Substep S44, selecting, intersecting, and mutation operation: the individuals with higher fitness in the current population are inherited to the next generation; performing crossover operation by adopting a single-point crossover method, performing mutation operation by adopting a basic mutation method, generating a next generation group, and increasing the iteration times by 1;
Substep S45, termination condition judgment: if the iteration number is greater than or equal to n, terminating calculation, and outputting the obtained individual with the minimum fitness as an optimal solution, namely the optimal in-furnace and out-furnace desulfurization proportion; otherwise, the process returns to the substep S43.
Further preferably, the number of groups n=20, the number of termination iterations n=80, the crossover probability is 0.4, and the mutation probability is 0.001.
Drawings
FIG. 1 is a schematic flow chart of the method for calculating the optimal in-furnace and out-furnace desulfurization ratio of the circulating fluidized bed unit.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It will be appreciated by persons skilled in the art that the description herein is merely illustrative of the preferred embodiments of the invention and should not be taken as limiting the scope of the invention, any variations or modifications that do not depart from the gist and spirit of the invention are intended to be within the scope of the invention.
The invention discloses a method for calculating the optimal internal and external desulfurization ratio of a circulating fluidized bed unit, which is shown in fig. 1, and comprises the following steps:
Step 1, establishing a comprehensive cost model of internal and external desulfurization of a CFB unit furnace, and selecting load, coal quality, coal feeding amount, total air quantity, bed temperature, rated power of a limestone conveying fan, rated power of a slurry circulating pump, limestone feeding flow rate in the furnace, ammonia spraying amount, original flue gas SO 2 concentration and net flue gas SO 2 concentration as inputs of the comprehensive cost model;
Step 2, determining a relational expression of desulfurization efficiency, load, calcium-sulfur mole ratio, bed temperature and wind-coal ratio in the furnace when the comprehensive cost model is established;
step 3, determining SO 2 generation concentration by utilizing the input of the comprehensive cost model selected in the step 1, and establishing an in-furnace and out-furnace desulfurization comprehensive cost model under the typical load working condition of the CFB unit after assuming the in-furnace desulfurization proportion;
And 4, solving the optimal in-furnace desulfurization ratio under the typical load working conditions by utilizing an intelligent optimizing algorithm, and fitting to obtain the optimal in-furnace desulfurization ratio under each load working condition.
In the embodiment, in step 2, a relation between the desulfurization efficiency in the furnace and the load, the molar ratio of calcium to sulfur and the bed temperature under a typical load working condition is fitted by a least square method, and the coefficient of the relation is corrected by using the wind-coal ratio. In the step 3, after the desulfurization proportion in the furnace is assumed, the power consumption of a limestone conveying fan, the power consumption of a slurry circulating pump and the power consumption of limestone for desulfurization inside and outside the furnace are determined, wherein the power consumption of the limestone conveying fan is determined by the feeding flow rate of limestone in the furnace and the rated power of the limestone conveying fan, and the power consumption of the slurry circulating pump is determined by the number of circulating pumps put into operation and the rated power. In the step 4, the optimal in-furnace desulfurization proportion under the typical load working condition is a solution of the minimum comprehensive cost of in-furnace and out-furnace desulfurization after genetic algorithm optimization.
The method comprises the following steps:
1. selection of model input variables
The circulating fluidized bed unit realizes ultra-low emission by the operation mode of combined desulfurization inside and outside the furnace. The total cost of the combined desulfurization inside and outside the furnace comprises: the equipment electricity consumption cost, the in-furnace denitration cost, the heat loss cost and the limestone consumption cost are combined to obtain the benefits generated by subtracting gypsum from the total desulfurization cost. Wherein: the limestone consumption cost comprises the in-furnace desulfurization limestone consumption cost and the out-furnace desulfurization limestone consumption cost. The equipment electricity consumption cost comprises: the power consumption of a limestone conveying fan in the furnace and the power consumption of a slurry circulating pump outside the furnace; the denitration cost in the furnace is influenced by the molar ratio of the desulfurization calcium and sulfur in the furnace, and the denitration cost in the furnace tends to be increased along with the increase of the calcium-sulfur ratio; the heat loss cost is also influenced by the molar ratio of the desulfurization calcium and sulfur in the furnace, and when the desulfurization efficiency in the furnace is unchanged, the lower the molar ratio of the calcium and the sulfur is, the lower the heat loss cost is, and the lower the converted coal consumption is; the dosage of the desulfurization limestone in the furnace is determined by the molar ratio of the desulfurization calcium and sulfur in the furnace, the desulfurization efficiency in the furnace and the coal quality, and the desulfurization efficiency in the furnace is related to the load, the molar ratio of the calcium and sulfur, the bed temperature and the wind-coal ratio; the amount of the off-furnace desulfurization limestone is related to the off-furnace desulfurization efficiency.
According to CFB unit operation data, desulfurization efficiency in the furnaceCan be obtained by the following formula:
wherein W c is the coal feeding amount; s ar is sulfur content, which is determined by coal quality; a ir is the total air quantity; k f is a dimensionless flue gas conversion coefficient; Is the concentration of SO 2 in the raw flue gas (under standard conditions).
Desulfurization efficiency outside the furnaceCan be obtained by the following formula:
Wherein, Is the concentration of SO 2 in the clean flue gas (under standard conditions).
Therefore, load, coal quality, coal feeding amount, total air quantity, bed temperature, rated power of a limestone conveying fan, rated power of a slurry circulating pump, limestone feeding flow rate in a furnace, ammonia injection amount, raw flue gas SO 2 concentration and net flue gas SO 2 concentration are selected as input variables of the model.
2. Determining the relation between the desulfurization efficiency and load, bed temperature and wind-coal ratio in the furnace
The method specifically comprises the following substeps:
s21, selecting bed temperature, coal feeding amount, total air quantity, coal quality, raw flue gas SO 2 concentration and limestone feeding flow rate in a furnace under a typical load working condition;
step S22, calculating to obtain the in-furnace desulfurization efficiency, the wind-coal ratio and the calcium-sulfur molar ratio under the typical load working condition, wherein the calculation of the in-furnace desulfurization calcium-sulfur molar ratio is shown by a formula (3):
In the formula (3), the amino acid sequence of the compound, The purity of the limestone is used for preparing the limestone,A limestone feed flow rate into the furnace;
Step S23, fitting a relation between the desulfurization efficiency in the furnace and the molar ratio of calcium to sulfur and the bed temperature under a typical load working condition by adopting a least square method, wherein the relation is expressed as shown in a formula (4):
In the formula (4), A is a dimensionless coefficient, B is a function of bed temperature, and m CFB is the molar ratio of calcium to sulfur in the furnace;
and S24, correcting A by using the wind-coal ratio under the typical load working condition according to the operation data, and finally obtaining a relational expression of the desulfurization efficiency in the furnace, the molar ratio of calcium to sulfur and the bed temperature under the typical load working condition.
3. Comprehensive cost model and solution
Desulfurization efficiency outside the furnaceRegarding the concentration and total air quantity of the original flue gas SO 2, the relation between the desulfurization efficiency outside the furnace, the concentration and the total air quantity of the original flue gas SO 2 can be fitted through a least square method, and the method specifically comprises the following substeps:
And S31, fitting the relation between the desulfurization efficiency outside the furnace and the concentration of SO 2 in the raw flue gas and the total air quantity by a least square method, wherein the relation is shown as a formula (6):
in the formula (6), a 1、a2、a3 is a model coefficient;
Step S32, assuming that the in-furnace desulfurization proportion is x under a certain typical load working condition, the out-of-furnace desulfurization proportion is 1-x, and combining the formula (1) and the formula (4), determining the calcium-sulfur molar ratio m CFB of the in-furnace desulfurization;
And a substep S33, wherein the limestone consumption cost W 1 in the furnace is expressed as the formula (7):
In the formula (7), M CaCO3、MCao is the relative molecular mass of CaCO 3 and CaO respectively, and the unit is g/mol; u1 is the unit price of limestone in the furnace, and the unit is yuan/kg;
The heat loss cost W 2 is expressed as shown in the formula (8):
W2＝Wc[η/(η-Δη)-1]u2 (8)，
In the formula (8), η is the boiler design efficiency; Δη is boiler heat loss; u 2 is the unit price of the fire coal in yuan/kg;
the denitration cost W 3 is expressed as shown in formula (9):
W3＝k1mCFBWcu3 (9)，
In formula (9), k 1 is a cost factor; u 3 is urea unit price in yuan/kg;
and the power consumption cost W 4 of the conveying fan is expressed as shown in a formula (10):
In the formula (10), alpha is the compressed air coefficient; u 4 is the electricity price of the internet, and the unit is Yuan/kWh;
The out-of-furnace limestone usage cost W 5 is expressed as shown in formula (11):
in the formula (11), m CFB and wet are the molar ratio of calcium to sulfur outside the furnace; u 5 is the unit price of the limestone outside the furnace, and the unit is yuan/t.
The power consumption W 6 of the circulating pump is expressed as shown in a formula (12):
W6＝nPwu4 (12)，
In the formula (12), n is the number of started slurry circulating pumps and is determined by the concentration and load of the raw flue gas SO 2; p w is the power of a single slurry circulating pump, and the unit is kW;
the gypsum gain V 7 is expressed as shown in formula (13):
wherein eta (H 2 O) is the water content of gypsum; u 8 is the unit price of gypsum, yuan/kg.
The combined desulfurization integrated cost f (x) inside and outside the furnace is expressed as shown in a formula (14):
f(x)＝W1+W2+W3+W4+W5+W6-V7 0≤X≤Xmax(14)，
In the formula (14), W 1、W2、W3、W4、W5、W6、V7 is determined by the desulfurization proportion x in the furnace, and is respectively the limestone consumption cost, heat loss cost, denitration cost, conveying fan electricity consumption cost, the limestone consumption cost outside the furnace, circulating pump electricity consumption and gypsum income; x max is determined by the desulfurization capacity in the furnace of the CFB unit.
The genetic algorithm optimizing process of the optimal in-furnace desulfurization proportion specifically comprises the following substeps:
substep S41, encoding: selecting an unsigned binary integer to represent an individual x i;
substep S42, generating an initial population: randomly generating N individuals as an initial group, and setting the iteration number as N;
Substep S43, fitness calculation: using the integrated cost function value g (x i) as fitness of the individual x i, a fitness function as shown in formula (15) is selected:
g(xi)＝minf(xi) (15)；
Substep S44, selecting, intersecting, and mutation operation: the individuals with higher fitness in the current population are inherited to the next generation; performing crossover operation by adopting a single-point crossover method, performing mutation operation by adopting a basic mutation method, generating a next generation group, and increasing the iteration times by 1;
Substep S45, termination condition judgment: if the iteration number is greater than or equal to n, terminating calculation, and outputting the obtained individual with the minimum fitness as an optimal solution, namely the optimal in-furnace and out-furnace desulfurization proportion; otherwise, the process returns to the substep S43.
In a specific embodiment, the number of groups n=20, the number of terminating iterations n=80, the crossover probability is 0.4, and the mutation probability is 0.001.
The invention has the following beneficial effects:
(1) According to the operation characteristics of the CFB unit, corresponding variables are selected, and the relation between the desulfurization efficiency in the furnace and the bed temperature and the wind-coal ratio is determined by adopting a least square method.
(2) On the basis, after the desulfurization proportion in the furnace is assumed, a desulfurization comprehensive cost model under a typical load working condition is respectively established.
(3) And a genetic algorithm is adopted, and the minimum desulfurization comprehensive cost is used as an objective function to optimize the optimal in-furnace and out-furnace desulfurization ratio under typical load working conditions.
Claims (3)
1. The method for calculating the optimal in-and-out desulfurization ratio of the circulating fluidized bed unit is characterized by comprising the following steps of:
Step 1, establishing a comprehensive cost model of internal and external desulfurization of a CFB unit furnace, and selecting load, coal quality, coal feeding amount, total air quantity, bed temperature, rated power of a limestone conveying fan, rated power of a slurry circulating pump, limestone feeding flow rate in the furnace, ammonia spraying amount, original flue gas SO 2 concentration and net flue gas SO 2 concentration as input variables of the comprehensive cost model;
The process for establishing the CFB unit internal and external desulfurization comprehensive cost model comprises the following steps:
The total cost of the combined desulfurization inside and outside the furnace is defined as comprising: the equipment electricity consumption cost, the in-furnace denitration cost, the heat loss cost and the limestone consumption cost are the comprehensive cost which is the total desulfurization cost minus the income generated by gypsum; wherein the limestone consumption cost comprises the consumption cost of the desulfurization limestone in the furnace and the consumption cost of the desulfurization limestone outside the furnace; the equipment electricity consumption cost comprises the electricity consumption of a limestone conveying fan in the furnace and the electricity consumption of a slurry circulating pump outside the furnace; the denitration cost in the furnace increases along with the increase of the molar ratio of the desulfurization calcium and the sulfur in the furnace; when the desulfurization efficiency in the furnace is unchanged, the lower the molar ratio of calcium to sulfur is, the lower the heat loss cost is, and the lower the converted coal consumption is; the dosage of the desulfurization limestone in the furnace is determined by the molar ratio of desulfurization calcium and sulfur in the furnace, the desulfurization efficiency in the furnace and the coal quality, and the desulfurization efficiency in the furnace is related to load, the molar ratio of calcium and sulfur, bed temperature and the wind-coal ratio; the dosage of the off-furnace desulfurization limestone is related to the off-furnace desulfurization efficiency;
Desulfurizing efficiency in the furnace Represented by the following formula (1):
In the formula (1), W c is the coal feeding amount, S ar is the sulfur content, A ir is the total air quantity, k f is the dimensionless flue gas conversion coefficient, Is the concentration of SO 2 in the original flue gas under standard conditions;
Desulfurizing efficiency outside the furnace Represented by the following formula (2):
In the formula (2), under the standard condition Is the concentration of SO 2 in the clean flue gas;
Step 2, determining a relational expression of desulfurization efficiency, load, calcium-sulfur mole ratio, bed temperature and wind-coal ratio in the furnace when the comprehensive cost model is established;
fitting a relation between the desulfurization efficiency in the furnace and the load, the molar ratio of calcium to sulfur and the bed temperature under a typical load working condition by adopting a least square method, and correcting the coefficient of the relation by utilizing the wind-coal ratio, wherein the method specifically comprises the following substeps:
s21, selecting bed temperature, coal feeding amount, total air quantity, coal quality, raw flue gas SO 2 concentration and limestone feeding flow rate in a furnace under a typical load working condition;
step S22, calculating to obtain the in-furnace desulfurization efficiency, the wind-coal ratio and the calcium-sulfur molar ratio under the typical load working condition, wherein the calculation of the in-furnace desulfurization calcium-sulfur molar ratio is shown by a formula (3):
In the formula (3), the amino acid sequence of the compound, The purity of the limestone is used for preparing the limestone,A limestone feed flow rate into the furnace;
Step S23, fitting a relation between the desulfurization efficiency in the furnace and the molar ratio of calcium to sulfur and the bed temperature under a typical load working condition by adopting a least square method, wherein the relation is expressed as shown in a formula (4):
In the formula (4), A is a dimensionless coefficient, B is a function of bed temperature, and m CFB is the molar ratio of calcium to sulfur in the furnace;
S24, correcting A by using the wind-coal ratio under the typical load working condition according to the operation data, and finally obtaining a relational expression of the desulfurization efficiency in the furnace and the molar ratio of calcium to sulfur and the bed temperature under the typical load working condition;
step 3, determining SO 2 generation concentration by utilizing the input of the comprehensive cost model selected in the step 1, and establishing an in-furnace and out-furnace desulfurization comprehensive cost model under the typical load working condition of the CFB unit after assuming the in-furnace desulfurization proportion;
After the desulfurization proportion in the furnace is assumed, the power consumption of a limestone conveying fan, the power consumption of a slurry circulating pump and the power consumption of limestone for desulfurization inside and outside the furnace are determined, wherein the power consumption of the limestone conveying fan is determined by the feeding flow rate of limestone in the furnace and the rated power of the limestone conveying fan, and the power consumption of the slurry circulating pump is determined by the number of circulating pumps put into operation and the rated power, and the method specifically comprises the following substeps:
And S31, fitting the relation between the desulfurization efficiency outside the furnace and the concentration of SO 2 in the raw flue gas and the total air quantity by a least square method, wherein the relation is shown as a formula (6):
in the formula (6), a 1、a2、a3 is a model coefficient;
Step S32, assuming that the in-furnace desulfurization proportion is x under a certain typical load working condition, the out-of-furnace desulfurization proportion is 1-x, and combining the formula (1) and the formula (4), determining the calcium-sulfur molar ratio m CFB of the in-furnace desulfurization;
And a substep S33, wherein the limestone consumption cost W 1 in the furnace is expressed as the formula (7):
In the formula (7), M CaCO3、MCao is the relative molecular mass of CaCO 3 and CaO respectively, and the unit is g/mol; u 1 is the unit price of limestone in the furnace, and the unit is yuan/kg;
The heat loss cost W 2 is expressed as shown in the formula (8):
W2＝Wc[η/(η-Δη)-1]u2 (8)，
In the formula (8), η is the boiler design efficiency; Δη is boiler heat loss; u 2 is the unit price of the fire coal in yuan/kg;
the denitration cost W 3 is expressed as shown in formula (9):
W3＝k1mCFBWcu3 (9)，
In formula (9), k 1 is a cost factor; u 3 is urea unit price in yuan/kg;
and the power consumption cost W 4 of the conveying fan is expressed as shown in a formula (10):
In the formula (10), alpha is the compressed air coefficient; u 4 is the electricity price of the internet, and the unit is Yuan/kWh;
the out-of-furnace limestone usage cost W 5 is expressed as shown in formula (11):
In the formula (11), m CFB and wet are the molar ratio of calcium to sulfur outside the furnace; u 5 is the unit price of the limestone outside the furnace, and the unit is yuan/t;
The power consumption W 6 of the circulating pump is expressed as shown in a formula (12):
W6＝nPwu4 (12)，
In the formula (12), n is the number of started slurry circulating pumps and is determined by the concentration and load of the raw flue gas SO 2; p w is the power of a single slurry circulating pump, and the unit is kW;
the gypsum gain V 7 is expressed as shown in formula (13):
Wherein eta (H 2 O) is the water content of gypsum; u 8 is the unit price of gypsum in yuan/kg;
the combined desulfurization integrated cost f (x) inside and outside the furnace is expressed as shown in a formula (14):
f(x)＝W1+W2+W3+W4+W5+W6-V7 0≤X≤Xmax (14),
In the formula (14), W 1、W2、W3、W4、W5、W6、V7 is determined by the desulfurization proportion x in the furnace, and is respectively the limestone consumption cost, heat loss cost, denitration cost, conveying fan electricity consumption cost, the limestone consumption cost outside the furnace, circulating pump electricity consumption and gypsum income; x max is determined by the desulfurization capacity in the CFB unit furnace;
And 4, solving the optimal in-furnace desulfurization ratio under the typical load working conditions by utilizing an intelligent optimizing algorithm, and fitting to obtain the optimal in-furnace desulfurization ratio under each load working condition.
2. The method for calculating the optimal in-furnace and out-of-furnace desulfurization ratio of the circulating fluidized bed unit according to claim 1, wherein in the step 4, the optimal in-furnace desulfurization ratio under the typical load working condition is a solution obtained by optimizing the minimum in-furnace and out-of-furnace desulfurization comprehensive cost by a genetic algorithm, and the process of optimizing the minimum in-furnace and out-of-furnace desulfurization comprehensive cost by the genetic algorithm comprises the following substeps:
substep S41, encoding: selecting an unsigned binary integer to represent an individual x i;
substep S42, generating an initial population: randomly generating N individuals as an initial group, and setting the iteration number as N;
substep S43, fitness calculation: using the integrated cost function value g (x i) as fitness of the individual x i, a fitness function as shown in formula (15) is selected:
g(xi)＝min f(xi) (15)；
Substep S44, selecting, intersecting, and mutation operation: the individuals with higher fitness in the current population are inherited to the next generation; performing crossover operation by adopting a single-point crossover method, performing mutation operation by adopting a basic mutation method, generating a next generation group, and increasing the iteration times by 1;
Substep S45, termination condition judgment: if the iteration number is greater than or equal to n, terminating calculation, and outputting the obtained individual with the minimum fitness as an optimal solution, namely the optimal in-furnace and out-furnace desulfurization proportion; otherwise, the process returns to the substep S43.
3. The method for calculating the optimal in-furnace and out-of-furnace desulfurization ratio of the circulating fluidized bed unit according to claim 2, wherein the number of groups n=20, the number of termination iterations n=80, the crossover probability is 0.4, and the mutation probability is 0.001.
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