CN114880919A - Method for calculating optimal furnace internal and external desulfurization proportion of circulating fluidized bed unit - Google Patents
Method for calculating optimal furnace internal and external desulfurization proportion of circulating fluidized bed unit Download PDFInfo
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- 238000006477 desulfuration reaction Methods 0.000 title claims abstract description 139
- 230000023556 desulfurization Effects 0.000 title claims abstract description 139
- 238000000034 method Methods 0.000 title claims abstract description 47
- 235000019738 Limestone Nutrition 0.000 claims abstract description 71
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- 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 28
- 239000003546 flue gas Substances 0.000 claims abstract description 28
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000011575 calcium Substances 0.000 claims abstract description 23
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 23
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000011593 sulfur Substances 0.000 claims abstract description 22
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 22
- 239000002002 slurry Substances 0.000 claims abstract description 20
- 230000014509 gene expression Effects 0.000 claims abstract description 19
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000005457 optimization Methods 0.000 claims abstract description 7
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 5
- 238000002347 injection Methods 0.000 claims abstract description 5
- 239000007924 injection Substances 0.000 claims abstract description 5
- JGIATAMCQXIDNZ-UHFFFAOYSA-N calcium sulfide Chemical compound [Ca]=S JGIATAMCQXIDNZ-UHFFFAOYSA-N 0.000 claims description 22
- 239000010440 gypsum Substances 0.000 claims description 15
- 229910052602 gypsum Inorganic materials 0.000 claims description 15
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- 230000008901 benefit Effects 0.000 claims description 7
- 230000002068 genetic effect Effects 0.000 claims description 7
- 239000000243 solution Substances 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
- 230000035772 mutation Effects 0.000 claims description 5
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 3
- 235000010216 calcium carbonate Nutrition 0.000 claims description 3
- 238000009401 outcrossing Methods 0.000 claims description 3
- 239000011541 reaction mixture Substances 0.000 claims description 3
- 239000000779 smoke Substances 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
- 238000006243 chemical reaction Methods 0.000 claims description 2
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Abstract
The invention discloses a method for calculating the optimal furnace internal and external desulfurization proportion of a circulating fluidized bed unit, which comprises the steps of firstly establishing a CFB unit furnace internal and external desulfurization comprehensive cost model, and selecting load, coal quality, coal feeding quantity, total air quantity, bed temperature, rated power of a limestone conveying fan, rated power of a slurry circulating pump, feeding flow rate of limestone in a furnace, ammonia injection quantity and raw flue gasSO 2 Concentration, clean flue gas SO 2 Concentration as an input variable; determining relational expressions of the desulfurization efficiency in the furnace and load, the molar ratio of calcium to sulfur, the bed temperature and the air-coal ratio when establishing the comprehensive cost model; secondly, determining the generation concentration of SO2 by using the input of the comprehensive cost model selected in the step 1, and establishing an in-furnace and out-furnace desulphurization comprehensive cost model under the typical load working condition of the CFB unit after assuming the in-furnace desulphurization proportion; and finally, solving the optimal in-furnace desulfurization proportion under the typical load working condition by using an intelligent optimization 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 furnace internal and external desulfurization proportion 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, can reach the standard of low emission through in-furnace desulfurization, and has simple process flow. With the ultralow emission standard of pollutant emission of coal-fired power generating units in China, in order to realize ultralow emission, the circulating fluidized bed unit is additionally provided with external desulfurization (flue gas desulfurization) equipment, and ultralow emission, SO, is realized by a combined desulfurization mode inside and outside the furnace 2 The ultra-low emission standard is less than or equal to 35mg/m 3 . At present, the research on the optimal furnace internal and external desulfurization proportion of the CFB unit is less, and the field operation is lack of guidance. On-site operators often ensure the original SO of the flue gas at the outlet of the hearth by adjusting the calcium-sulfur ratio of the desulfurization in the furnace 2 The concentration is in a certain fixed range, SO is ensured after the external desulfurization of the furnace 2 The emission concentration is less than 35mg/m 3 . Although the operation mode is simple, the change rules of the in-furnace/out-furnace desulfurization efficiency and the operation cost under different load working conditions of the unit are not considered, 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 the CFB unit furnace and poor desulfurization operation economy in the prior art, and provides a method for calculating the optimal internal and external desulfurization proportion of the circulating fluidized bed unit furnace.
Disclosure of Invention
The invention provides a method for calculating the optimal furnace internal and external desulfurization proportion of a circulating fluidized bed unit, which comprises the following steps:
step 1, establishing a CFB unit furnace internal and external desulfurization comprehensive cost model, and selecting load, coal quality, coal feeding quantity, total air quantity, bed temperature, limestone conveying fan rated power, slurry circulating pump rated power, limestone feeding flow rate in a furnace, ammonia injection quantity and raw flue gas SO 2 Concentration, clean flue gas SO 2 Concentration is used as an input variable of the comprehensive cost model;
step 2, determining relational expressions of desulfurization efficiency in the furnace and load, calcium-sulfur molar ratio, bed temperature and air-coal ratio when establishing the comprehensive cost model;
step 3, determining the SO2 generation concentration by using 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 proportion under the typical load working condition by using an intelligent optimization algorithm, and fitting to obtain the optimal in-furnace desulfurization proportion under each load working condition.
Preferably, the process of establishing the comprehensive cost model of the internal and external desulfurization of the CFB unit in step 1 is as follows: defining the total combined desulfurization cost inside and outside the furnace as comprising: the comprehensive cost is the sum of the total desulfurization cost minus the benefit generated by gypsum; wherein the limestone consumption cost comprises the consumption cost of the in-furnace desulfurized limestone and the consumption cost of the out-furnace desulfurized limestone; the power consumption cost of the equipment 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 increased along with the increase of the molar ratio of the desulfurized calcium to the desulfurized calcium in the furnace and the denitration cost in the furnace is increased; 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 in-furnace desulfurization limestone is determined by the in-furnace desulfurization calcium-sulfur molar ratio, the in-furnace desulfurization efficiency and the coal quality, and the in-furnace desulfurization efficiency is related to load, the calcium-sulfur molar ratio, bed temperature and air-coal ratio; the amount of limestone desulfurized outside the furnace is related to the desulfurization efficiency outside the furnace;
in the formula (1), W c For coal supply, S ar Is a sulfur content, A ir Total air volume, k f For the dimensionless conversion coefficient of the smoke,is the raw flue gas SO under standard conditions 2 Concentration;
Preferably, in the step 2, a least square method is adopted to fit a relational expression of the in-furnace desulfurization efficiency, the load, the calcium-sulfur molar ratio and the bed temperature under a typical load working condition, and the coefficient of the relational expression is corrected by using the air-coal ratio, and the method specifically comprises the following substeps:
substep S21, selecting bed temperature, coal supply quantity, total air quantity, coal quality and raw flue gas SO under typical load working condition 2 Concentration, in-furnace limestone feed flow rate;
and a substep S22, calculating the in-furnace desulfurization efficiency, the air-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 an equation (3):
in the formula (3), the reaction mixture is,in order to obtain the purity of the limestone,a feed flow rate for limestone in the furnace;
and a substep S23 of fitting 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 by adopting a least square method, wherein the relational expression is expressed as a formula (4):
in the formula (4), A is a dimensionless coefficient, B is a function of bed temperature, m CFB The molar ratio of calcium to sulfur in the furnace is shown;
and a substep S24, correcting the A by using the air-coal ratio under the typical load working condition according to the operation data, and finally obtaining a relational expression of the in-furnace desulfurization efficiency, the calcium-sulfur molar ratio and the bed temperature under the typical load working condition.
Preferably, in step 3, after assuming the ratio of desulfurization in the furnace, determining 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, 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 in operation and the rated power, specifically comprising the following substeps:
substep S31, fitting the external desulfurization efficiency and the raw flue gas SO by a least square method 2 The relationship between the concentration and the total air volume is expressed by the following formula (6):
in the formula (6), a1, a2 and a3 are model coefficients;
and a substep S32, assuming that the desulfurization ratio inside the furnace is x under a certain typical load working condition, the desulfurization ratio outside the furnace is 1-x, and combining the formula (1) and the formula (4), determining the molar ratio m of calcium and sulfur desulfurized inside the furnace CFB ;
Substep S33, determining the limestone consumption cost W in the furnace 1 Expressed as shown in formula (7):
in the formula (7), MCaCO3 and MCaO are the relative molecular masses of CaCO3 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 Expressed as shown in formula (8):
W 2 =W c [η/(η-Δη)-1]u 2 (8),
in the formula (8), η is the boiler design efficiency; Δ η is boiler heat loss; u2 is the unit price of the fire coal, and the unit is Yuan/kg;
the denitration cost W 3 Expressed as shown in formula (9):
W 3 =k 1 m CFB W c u 3 (9),
in the formula (9), k1 is a cost coefficient; u3 is the urea unit price, unit is yuan/kg;
electrically connecting the conveying fanCost W 4 Expressed as shown in formula (10):
in the formula (10), α is a compressed air coefficient; u. of 4 The unit is yuan/kWh for the price of the power on the internet;
the dosage cost W of the limestone outside the furnace 5 Expressed as shown in formula (11):
in the formula (11), mCFB and wet are in the molar ratio of calcium to sulfur outside the furnace; u5 is the unit price of limestone outside the furnace, and the unit is Yuan/t.
The power consumption W6 of the circulating pump is expressed as shown in the formula (12):
W 6 =nP w u 4 (12),
in the formula (12), n is the number of the slurry circulating pumps started and is the raw flue gas SO 2 Determining concentration and load; p w The power of a single slurry circulating pump is in kW;
the gypsum income V 7 Expressed as shown in formula (13):
wherein eta (H) 2 O) is the water content of the gypsum; u. of 8 Is the unit price of gypsum, and the unit is yuan/kg;
and (3) expressing the comprehensive cost f (x) of the combined desulfurization inside and outside the furnace as shown in a formula (14):
f(x)=W 1 +W 2 +W 3 +W 4 +W 5 +W 6 +W 7 -V 8 0≤x≤x max (14),
in the formula (14), W 1 、W 2 、W 3 、W 4 、W 5 、W 6 、V 7 The amount cost of the limestone in the furnace, the cost of heat loss, the cost of denitration, the cost of power consumption of a conveying fan, the cost of the amount of the limestone outside the furnace, the power consumption of a circulating pump and the benefit of gypsum are respectively determined by the desulfurization proportion x in the furnace; x is the number of max Determined by the in-furnace desulfurization capacity of the CFB unit.
Preferably, in step 4, the optimal in-furnace desulfurization proportion under the typical load condition is a solution obtained by the genetic algorithm optimizing the minimum integrated cost of inside and outside desulfurization of the furnace, wherein the genetic algorithm optimizing process comprises the following substeps:
substep S41, encoding: selecting unsigned binary integers to represent individuals x i ;
Substep S42, generating an initial population: randomly generating N individuals as an initial population, and setting the iteration number as N;
substep S43, fitness calculation: using the value of the integrated cost function g (x) i) As an individual x i Selecting a fitness function as shown in formula (15):
g(x i )=minf(x i ) (15);
substep S44, selection, crossover, mutation operation: the individuals with higher fitness in the current group are inherited to the next generation; the method adopts a single-point crossing method to carry out crossing operation, adopts a basic bit variation method to carry out variation operation, saves the next generation of group, and increases the iteration times by 1;
substep S45, termination condition judgment: if the iteration times are more than or equal to n, stopping the calculation, and outputting the obtained individual with the minimum fitness as an optimal solution, namely the optimal furnace internal and external desulfurization proportion; otherwise, return to substep S43.
Further preferably, the number of population N is 20, the number of termination iterations N is 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 furnace internal and external desulfurization proportion of the circulating fluidized bed unit.
Detailed Description
The following detailed description of the embodiments of the invention refers to the accompanying drawings. It will be understood by those skilled in the art that the present description is illustrative of the preferred embodiments of the invention and is not to be construed as limiting the scope of the invention in any way, and that variations or modifications can be made without departing from the spirit and scope of the invention.
The invention discloses a method for calculating the optimal furnace internal and external desulfurization proportion of a circulating fluidized bed unit, and fig. 1 is a flow schematic diagram of the method for calculating the optimal furnace internal and external desulfurization proportion of the circulating fluidized bed unit, as shown in fig. 1, the method comprises the following steps:
step 1, establishing a CFB unit furnace internal and external desulfurization comprehensive cost model, and selecting load, coal quality, coal feeding quantity, total air quantity, bed temperature, limestone conveying fan rated power, slurry circulating pump rated power, limestone feeding flow rate in a furnace, ammonia injection quantity and raw flue gas SO 2 Concentration, clean flue gas SO 2 Concentration is used as an input of the comprehensive cost model;
step 2, determining relational expressions of desulfurization efficiency in the furnace and load, calcium-sulfur molar ratio, bed temperature and air-coal ratio when establishing the comprehensive cost model;
step 3, determining the SO2 generation concentration by using 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 proportion under the typical load working condition by using an intelligent optimization algorithm, and fitting to obtain the optimal in-furnace desulfurization proportion under each load working condition.
In this embodiment, in step 2, a least square method is used to fit a relational expression of the in-furnace desulfurization efficiency, the load, the calcium-sulfur molar ratio, and the bed temperature under typical load conditions, and the coefficients of the relational expression are corrected by using the air-coal ratio. And 3, after the desulfurization proportion in the furnace is assumed, determining 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, 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 in operation and the rated power. In step 4, the optimal in-furnace desulfurization proportion under the typical load working condition is the solution of the minimum comprehensive cost of in-furnace and out-furnace desulfurization optimized by the genetic algorithm.
The method comprises the following specific steps:
1. selection of model input variables
The circulating fluidized bed unit realizes ultralow emission by a combined desulfurization operation mode inside and outside the furnace. The total cost of the combined desulfurization inside and outside the furnace comprises: the power consumption cost of equipment, the denitration cost in the furnace, the heat loss cost and the consumption cost of limestone, and the comprehensive cost is the total desulfurization cost minus the benefit generated by gypsum. Wherein: the limestone consumption cost comprises the consumption cost of the desulfurized limestone inside the furnace and the consumption cost of the desulfurized limestone outside the furnace. The equipment power consumption cost comprises the following steps: 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 calcium to sulfur of desulfurization in the furnace, and the denitration cost in the furnace is increased along with the increase of the molar ratio of calcium to sulfur; the heat loss cost is also influenced by the molar ratio of calcium to sulfur desulfurized in the furnace, and 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 in-furnace desulfurization limestone is determined by the in-furnace desulfurization calcium-sulfur molar ratio, the in-furnace desulfurization efficiency and the coal quality, and the in-furnace desulfurization efficiency is related to load, the calcium-sulfur molar ratio, bed temperature and air-coal ratio; the amount of limestone desulfurized outside the furnace is related to the desulfurization efficiency outside the furnace.
According to the operation data of the CFB unit, the desulfurization efficiency in the furnaceCan be obtained by the following formula:
wherein, W c Is the coal feeding amount; s ar The sulfur content is determined by the coal quality; a. the ir The total air volume; k is a radical of f Converting the dimensionless smoke into coefficients;is raw flue gas SO 2 Concentration (under standard conditions).
wherein the content of the first and second substances,is clean flue gas SO 2 Concentration (under standard conditions).
Therefore, the load, the coal quality, the coal feeding amount, the total air volume, the bed temperature, the rated power of the limestone conveying fan, the rated power of the slurry circulating pump, the feeding flow rate of the limestone in the furnace, the ammonia injection amount, and the raw flue gas SO are selected 2 Concentration, clean flue gas SO 2 Concentration is used as an input variable for the model.
2. Determining the relation between the desulfurization efficiency in the furnace and the load, bed temperature and air-coal ratio
The method specifically comprises the following substeps:
substep S21, selecting bed temperature, coal supply quantity, total air quantity, coal quality and raw flue gas SO under typical load working condition 2 Concentration, in-furnace limestone feed flow rate;
and a substep S22, calculating the in-furnace desulfurization efficiency, the air-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 an equation (3):
in the formula (3), the reaction mixture is,in order to achieve the purity of the limestone,a feed flow rate for limestone in the furnace;
and a substep S23, fitting a relational expression of the desulfurization efficiency in the furnace, 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 relational expression is shown as a formula (4):
in the formula (4), A is a dimensionless coefficient, B is a function of bed temperature, m CFB The molar ratio of calcium to sulfur in the furnace is shown;
and a substep S24, correcting the A by using the air-coal ratio under the typical load working condition according to the operation data, and finally obtaining a relational expression of the in-furnace desulfurization efficiency, the calcium-sulfur molar ratio and the bed temperature under the typical load working condition.
3. Synthetic cost model and solution
External desulfurization efficiencyWith raw flue gas SO 2 The concentration and the total air volume are related, and the external desulfurization efficiency and the raw flue gas SO can be fitted by a least square method 2 The relation between the concentration and the total air volume specifically comprises the following substeps:
substep S31, fitting the external desulfurization efficiency and the raw flue gas SO by a least square method 2 The relationship between the concentration and the total air volume is expressed by the following formula (6):
in the formula (6), a1, a2 and a3 are model coefficients;
and a substep S32, assuming that the desulfurization ratio inside the furnace is x under a certain typical load working condition, the desulfurization ratio outside the furnace is 1-x, and combining the formula (1) and the formula (4), determining the molar ratio m of calcium and sulfur desulfurized inside the furnace CFB ;
Substep S33, determining the limestone consumption cost W in the furnace 1 Expressed as shown in formula (7):
in the formula (7), MCaCO3 and MCaO are the relative molecular masses of CaCO3 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 Expressed as shown in formula (8):
W 2 =W c [η/(η-Δη)-1]u 2 (8),
in the formula (8), η is the boiler design efficiency; Δ η is boiler heat loss; u2 is the unit price of the fire coal, and the unit is Yuan/kg;
the denitration cost W 3 Expressed as shown in formula (9):
W 3 =k 1 m CFB W c u 3 (9),
in the formula (9), k1 is a cost coefficient; u3 is the urea unit price, unit is yuan/kg;
the power consumption cost W of the conveying fan 4 Expressed as shown in formula (10):
in the formula (10), α is a compressed air coefficient; u. of 4 The unit is yuan/kWh for the price of the power on the internet;
the dosage cost W of the limestone outside the furnace 5 Expressed as shown in formula (11):
in the formula (11), mCFB and wet are in the molar ratio of calcium to sulfur outside the furnace; u5 is the unit price of limestone outside the furnace, and the unit is Yuan/t.
The power consumption W6 of the circulating pump is expressed as shown in the formula (12):
W 6 =nP w u 4 (12),
in the formula (12), n is the number of the slurry circulating pumps started and is the raw flue gas SO 2 Determining concentration and load; p w The power of a single slurry circulating pump is in kW;
the gypsum income V 7 Expressed as shown in formula (13):
wherein eta (H) 2 O) is the water content of the gypsum; u. of 8 The gypsum is monovalent, yuan/kg.
And (3) expressing the comprehensive cost f (x) of the combined desulfurization inside and outside the furnace as shown in a formula (14):
f(x)=W 1 +W 2 +W 3 +W 4 +W 5 +W 6 +W 7 -V 8 0≤x≤x max (14),
in the formula (14), W 1 、W 2 、W 3 、W 4 、W 5 、W 6 、V 7 The desulfurization ratio x in the furnace is determined, and the cost is the consumption cost of limestone in the furnace, the cost of heat loss, the cost of denitration, the cost of power consumption of a conveying fan, the consumption cost of limestone outside the furnace, the power consumption of a circulating pump and the benefit of gypsum; x is the number of max Determined by the in-furnace desulfurization capacity of the CFB unit.
The process of optimizing the optimal in-furnace desulfurization proportion by a genetic algorithm specifically comprises the following substeps:
substep S41, encoding: selecting unsigned binary integers to represent individuals x i ;
Substep S42, generating an initial population: randomly generating N individuals as an initial population, and setting the iteration number as N;
substep S43, fitness calculation: using the value of the integrated cost function g (x) i) As an individual x i Selecting a fitness function as shown in formula (15):
g(x i )=minf(x i ) (15);
substep S44, selection, crossover, mutation operation: the individuals with higher fitness in the current group are inherited to the next generation; the method adopts a single-point crossing method to carry out crossing operation, adopts a basic bit variation method to carry out variation operation, saves the next generation of group, and increases the iteration times by 1;
substep S45, termination condition judgment: if the iteration times are more than or equal to n, stopping the calculation, and outputting the obtained individual with the minimum fitness as an optimal solution, namely the optimal furnace internal and external desulfurization proportion; otherwise, return to substep S43.
In a specific embodiment, the number of population N is 20, the number of termination iterations N is 80, the crossover probability is 0.4, and the mutation probability is 0.001.
The invention has the following beneficial effects:
(1) and selecting corresponding variables according to the operating characteristics of the CFB unit, and determining the relationship between the in-furnace desulfurization efficiency and the bed temperature and the air-coal ratio 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 (3) optimizing the optimal furnace internal and external desulfurization ratio under the typical load working condition by adopting a genetic algorithm and taking the minimum desulfurization comprehensive cost as an objective function.
Claims (6)
1. A method for calculating the optimal furnace inside and outside desulfurization proportion of a circulating fluidized bed unit is characterized by comprising the following steps of:
step 1, establishing a CFB unit furnace internal and external desulfurization comprehensive cost model, and selecting load, coal quality, coal feeding quantity, total air quantity, bed temperature, limestone conveying fan rated power, slurry circulating pump rated power, limestone feeding flow rate in a furnace, ammonia injection quantity and raw flue gas SO 2 Concentration, clean flue gas SO 2 Concentration is used as an input variable of the comprehensive cost model;
step 2, determining relational expressions of desulfurization efficiency in the furnace and load, calcium-sulfur molar ratio, bed temperature and air-coal ratio when establishing the comprehensive cost model;
step 3, determining the SO2 generation concentration by using 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 proportion under the typical load working condition by using an intelligent optimization algorithm, and fitting to obtain the optimal in-furnace desulfurization proportion under each load working condition.
2. The method for calculating the optimal furnace internal and external desulfurization proportion of the circulating fluidized bed unit according to claim 1, wherein the process for establishing the CFB unit furnace internal and external desulfurization comprehensive cost model in the step 1 is as follows:
defining the total combined desulfurization cost inside and outside the furnace as comprising: the comprehensive cost is the sum of the total desulfurization cost minus the benefit generated by gypsum; wherein the limestone consumption cost comprises the consumption cost of the in-furnace desulfurized limestone and the consumption cost of the out-furnace desulfurized limestone; the power consumption cost of the equipment 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 increased along with the increase of the molar ratio of the desulfurized calcium to the desulfurized calcium in the furnace and the denitration cost in the furnace is increased; 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 in-furnace desulfurization limestone is determined by the in-furnace desulfurization calcium-sulfur molar ratio, the in-furnace desulfurization efficiency and the coal quality, and the in-furnace desulfurization efficiency is related to load, the calcium-sulfur molar ratio, bed temperature and air-coal ratio; the amount of limestone desulfurized outside the furnace is related to the desulfurization efficiency outside the furnace;
in the formula (1), the reaction mixture is,W c for coal supply, S ar Is a sulfur content, A ir Total air volume, k f For the dimensionless conversion coefficient of the smoke,is the raw flue gas SO under standard conditions 2 Concentration;
3. The method for calculating the optimal furnace internal and external desulfurization proportion of the circulating fluidized bed unit according to claim 2, wherein in the step 2, a least square method is adopted to fit a relational expression of the furnace desulfurization efficiency, the load, the calcium-sulfur molar ratio and the bed temperature under the typical load working condition, and the coefficient of the relational expression is corrected by using a wind-coal ratio, and the method specifically comprises the following substeps:
substep S21, selecting bed temperature, coal supply quantity, total air quantity, coal quality and raw flue gas SO under typical load working condition 2 Concentration, in-furnace limestone feed flow rate;
and a substep S22, calculating the in-furnace desulfurization efficiency, the air-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 an equation (3):
formula (3)) In the step (1), the first step,in order to obtain the purity of the limestone,a feed flow rate for limestone in the furnace;
and a substep S23 of fitting 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 by adopting a least square method, wherein the relational expression is expressed as a formula (4):
in the formula (4), A is a dimensionless coefficient, B is a function of bed temperature, m CFB The molar ratio of calcium to sulfur in the furnace is shown;
and a substep S24, correcting the A by using the air-coal ratio under the typical load working condition according to the operation data, and finally obtaining a relational expression of the in-furnace desulfurization efficiency, the calcium-sulfur molar ratio and the bed temperature under the typical load working condition.
4. The method according to claim 3, wherein in step 3, assuming the ratio of desulfurization in the furnace, the power consumption of the limestone conveying fan, the power consumption of the slurry circulating pump, and the limestone consumption for desulfurization inside and outside the furnace are determined, wherein the power consumption of the limestone conveying fan is determined by the limestone feeding flow rate 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 in operation and the rated power, and the method specifically comprises the following substeps:
substep S31, fitting the external desulfurization efficiency and the raw flue gas SO by a least square method 2 The relationship between the concentration and the total air volume is expressed by the following formula (6):
in the formula (6), a1, a2 and a3 are model coefficients;
and a substep S32, assuming that the desulfurization ratio inside the furnace is x under a certain typical load working condition, the desulfurization ratio outside the furnace is 1-x, and combining the formula (1) and the formula (4), determining the molar ratio m of calcium and sulfur desulfurized inside the furnace CFB ;
Substep S33, determining the limestone consumption cost W in the furnace 1 Expressed as shown in formula (7):
in the formula (7), MCaCO3 and MCaO are the relative molecular masses of CaCO3 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 Expressed as shown in formula (8):
W 2 =W c [η/(η-Δη)-1]u 2 (8),
in the formula (8), η is the boiler design efficiency; Δ η is boiler heat loss; u2 is the unit price of the fire coal, and the unit is Yuan/kg;
the denitration cost W 3 Expressed as shown in formula (9):
W 3 =k 1 m CFB W c u 3 (9),
in the formula (9), k1 is a cost coefficient; u3 is the urea unit price, unit is yuan/kg;
the power consumption cost W of the conveying fan 4 Expressed as shown in formula (10):
in the formula (10), α is a compressed air coefficient; u. of 4 The unit is yuan/kWh for the price of the power on the internet;
the dosage cost W of the limestone outside the furnace 5 Expressed as shown in formula (11):
in the formula (11), mCFB and wet are in the molar ratio of calcium to sulfur outside the furnace; u5 is the unit price of limestone outside the furnace, and the unit is Yuan/t;
the power consumption W6 of the circulating pump is expressed as shown in the formula (12):
W 6 =nP w u 4 (12),
in the formula (12), n is the number of the slurry circulating pumps started and is the raw flue gas SO 2 Determining concentration and load; p w The power of a single slurry circulating pump is in kW;
the gypsum income V 7 Expressed as shown in formula (13):
wherein eta (H) 2 O) is the water content of the gypsum; u. of 8 Is the unit price of gypsum, and the unit is yuan/kg;
and (3) expressing the comprehensive cost f (x) of the combined desulfurization inside and outside the furnace as shown in a formula (14):
f(x)=W 1 +W 2 +W 3 +W 4 +W 5 +W 6 +W 7 -V 8 0≤x≤x max (14),
in the formula (14), W 1 、W 2 、W 3 、W 4 、W 5 、W 6 、V 7 The desulfurization ratio x in the furnace is determined, and the cost is the consumption cost of limestone in the furnace, the cost of heat loss, the cost of denitration, the cost of power consumption of a conveying fan, the consumption cost of limestone outside the furnace, the power consumption of a circulating pump and the benefit of gypsum; x is the number of max Determined by the in-furnace desulfurization capacity of the CFB unit.
5. The method for calculating the optimal furnace internal and external desulfurization proportion of the circulating fluidized bed unit according to claim 4, wherein in the step 4, the optimal furnace internal desulfurization proportion under the typical load working condition is a solution obtained by genetic algorithm optimization of the minimum integrated cost of the furnace internal and external desulfurization, and the process of genetic algorithm optimization of the minimum integrated cost of the furnace internal and external desulfurization comprises the following sub-steps:
substep S41, encoding: selecting unsigned binary integers to represent an individual x i ;
Substep S42, generating an initial population: randomly generating N individuals as an initial population, and setting the iteration number as N;
substep S43, fitness calculation: using the value of the integrated cost function g (x) i ) As an individual x i Selecting a fitness function as shown in formula (15):
g(x i )=min f(x i ) (15);
substep S44, selection, crossover, mutation operation: the individuals with higher fitness in the current group are inherited to the next generation; the method adopts a single-point crossing method to carry out crossing operation, adopts a basic bit variation method to carry out variation operation, saves the next generation of group, and increases the iteration times by 1;
substep S45, termination condition determination: if the iteration times are more than or equal to n, stopping the calculation, and outputting the obtained individual with the minimum fitness as an optimal solution, namely the optimal furnace internal and external desulfurization proportion; otherwise, return to substep S43.
6. The method of claim 5, wherein the number of groups N is 20, the number of termination iterations N is 80, the crossover probability is 0.4, and the variation probability is 0.001.
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