CN113689917A - Visual ammonia injection optimization method and device based on SCR outlet NOx concentration - Google Patents
Visual ammonia injection optimization method and device based on SCR outlet NOx concentration Download PDFInfo
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 281
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 137
- 238000002347 injection Methods 0.000 title claims abstract description 99
- 239000007924 injection Substances 0.000 title claims abstract description 99
- 238000000034 method Methods 0.000 title claims abstract description 34
- 238000005457 optimization Methods 0.000 title claims abstract description 28
- 230000000007 visual effect Effects 0.000 title claims abstract description 16
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 44
- 239000003546 flue gas Substances 0.000 claims abstract description 44
- 239000003054 catalyst Substances 0.000 claims abstract description 32
- 238000006243 chemical reaction Methods 0.000 claims abstract description 30
- 239000011159 matrix material Substances 0.000 claims abstract description 27
- 238000013178 mathematical model Methods 0.000 claims abstract description 24
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 claims abstract description 22
- 238000004088 simulation Methods 0.000 claims abstract description 17
- 238000005192 partition Methods 0.000 claims abstract description 10
- 230000008878 coupling Effects 0.000 claims abstract description 8
- 238000010168 coupling process Methods 0.000 claims abstract description 8
- 238000005859 coupling reaction Methods 0.000 claims abstract description 8
- 238000004364 calculation method Methods 0.000 claims description 14
- 238000004458 analytical method Methods 0.000 claims description 8
- 238000005070 sampling Methods 0.000 claims description 4
- 230000003068 static effect Effects 0.000 claims description 4
- 238000011478 gradient descent method Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 238000005507 spraying Methods 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- AVXURJPOCDRRFD-UHFFFAOYSA-N Hydroxylamine Chemical class ON AVXURJPOCDRRFD-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 231100000045 chemical toxicity Toxicity 0.000 description 1
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- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
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- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000012800 visualization Methods 0.000 description 1
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Abstract
The invention discloses a visual ammonia injection optimization method and device based on SCR outlet NOx concentration, wherein the method comprises the following steps: measuring to obtain field flue gas flow field data; according to field flue gas flow field data, a CFD model is established, and influence factors corresponding to different partitions in the SCR system are obtained; establishing an SCR reaction mathematical model, and obtaining ammonia nitrogen molar ratio distribution of each subarea at the catalyst inlet by taking the optimal concentration distribution uniformity of the NOx at the outlet as a target; and coupling, namely establishing a matrix equation based on the influence factors, and solving to obtain the optimal ammonia injection amount. According to the method, the ammonia injection quantity of the optimized ammonia injection subarea which enables the concentration distribution of the NOx at the outlet of the SCR to be the most uniform is obtained through simulation by taking the concentration distribution of the NOx at the outlet of the SCR as an optimization target, so that the problems of large concentration deviation of the NOx at the outlet and large local ammonia escape caused by the current SCR denitration method are effectively solved, and the debugging efficiency of the ammonia injection control regulating valve under different working conditions can be improved by establishing reaction models under different working conditions.
Description
Technical Field
The invention relates to the technical field of SCR denitration, in particular to a visual ammonia injection optimization method and device based on SCR outlet NOx concentration.
Background
In order to reduce the emission of the flue gas NOx of the coal-fired power plant, the mainstream denitration technology of the domestic coal-fired power plant adopts Selective Catalytic Reduction (SCR) for denitration treatment. Most of current researches focus on SCR denitration systems mainly on ammonia spraying optimization aiming at the most uniform ammonia nitrogen molar ratio distribution at the inlet of a first-layer catalyst, but the concentration of NOx at the outlet of the catalyst is not only related to the ammonia nitrogen molar ratio at the inlet of the catalyst, but also related to factors such as the temperature, the speed and the activity of the catalyst at the inlet of the catalyst, and the catalyst layer is easily subjected to physical abrasion, chemical toxicity and the like during field operation, so that the activity of the catalyst in each subarea is not consistent, so that the purpose of the most uniform concentration distribution of the NOx at the outlet cannot be achieved only by realizing the most uniform ammonia nitrogen molar ratio distribution at the inlet, and the problems of large deviation of the concentration of the NOx escaping from the outlet, large local ammonia and the like still exist after optimization.
Disclosure of Invention
The invention provides a visual ammonia injection optimization method and device based on SCR outlet NOx concentration, which can effectively solve the problems of large outlet NOx concentration deviation and large local ammonia escape caused by the current SCR denitration method.
In order to solve the technical problem, an embodiment of the present invention provides a visualized ammonia injection optimization method based on an SCR outlet NOx concentration, including the following steps:
measuring an inlet of the SCR system under a constant load to obtain field flue gas flow field data;
establishing a CFD model of the SCR system according to the field flue gas flow field data;
acquiring an ammonia injection influence factor of the SCR system according to the CFD model;
establishing an SCR reaction mathematical model corresponding to the SCR system, and calculating to obtain ammonia nitrogen molar ratio distribution of each subarea at the catalyst inlet by combining the SCR reaction mathematical model with the aim of optimizing concentration distribution uniformity of outlet NOx; the SCR reaction mathematical model is used for outputting a mathematical relation between the concentration of outlet NOx and inlet influence factors;
and establishing a matrix equation by coupling ammonia injection influence factors of the SCR system according to the ammonia nitrogen molar ratio distribution of each subarea, and solving the matrix equation to obtain the optimal ammonia injection amount so as to optimize the SCR system.
Further, the measuring of the inlet of the SCR system under constant load to obtain on-site flue gas flow field data specifically includes: measuring the flue gas flow field characteristics of the inlet measuring section of the SCR system by using measuring equipment to obtain a velocity field, a concentration field and a temperature field of the inlet measuring section, and providing inlet parameters for CFD numerical simulation.
Further, establishing a CFD model of the SCR system according to the field flue gas flow field data specifically includes: and modeling the whole structure of the CFD model of the SCR system by adopting CFD flow field analysis.
Further, after the CFD model of the SCR system is established, the method further includes: and verifying the CFD model of the SCR system and simulating the visual analysis of a flow field, specifically comprising the following steps:
measuring according to the inlet of the SCR system under the constant load to obtain field flue gas flow field data, and reasonably setting simulated inlet boundary conditions; performing numerical calculation in Fluent, comparing a calculation result with the field flue gas flow field data after calculating and determining flow field convergence, and verifying the reliability of the CFD model of the SCR system;
simulation of flue gas and NH with a component transport model3The CFD model of the SCR system is verified by combining the field flue gas flow field data, the trace flow rule of the ammonia gas is analyzed, the actual flue gas flow of the SCR system is reflected, and the simulation flow fields under different working conditions can be visually analyzed.
Further, the SCR reaction mathematical model is used to output a mathematical relationship between outlet NOx concentration and inlet influencing factors, specifically: cNO,out＝f(α,T,v,CNO,in)；
Wherein C isNO,outIndicates the outlet NOx concentration, CNO,inRepresenting inlet NOx concentration, alpha representing inlet ammonia to nitrogen molar ratio, T representing inlet temperature, v representing inlet flue gas velocity.
Further, the influence factor quantitatively analyzes the influence of the ammonia spraying amount at the inlet on the ammonia concentration at the inlet of the first-layer catalyst by means of Fluent flow field simulation of the CFD model, the section of the inlet of the catalyst is divided into 12 areas, and the sampling quantity is gridded corresponding to the NOx at the outlet;
the influence factor is defined as follows:
αi: influence factors of different partitions, ri: individual zoned ammonia injection affects the ammonia concentration, R, in a zonei: the ammonia concentration in a certain area is influenced when the ammonia is uniformly sprayed.
Further, the SCR system includes: the device comprises an inlet flue, an outlet flue, an ammonia injection grid, a guide plate, a static mixer, a rectification grid and a catalyst layer; the ammonia injection grid has 21 groups in total and is provided with 84 nozzles.
Further, the matrix equation is defined as:
for the 21 sets of ammonia injection grids, aiTo liSolving a 21 x 12 matrix equation for the influence factors of each group of ammonia injection grids on 12 areas of the catalyst inlet; y isiRepresenting the optimization target quantity of each partition; xiThe amount of ammonia injection to be required for each section is indicated.
Further, the solving the matrix equation to obtain the optimal ammonia injection amount to optimize the SCR system specifically includes:
and solving the matrix equation by adopting a gradient descent method of matlab software to obtain the optimal ammonia injection amount of the subareas under different working conditions so as to optimize the subarea ammonia injection amount of the SCR system under different working conditions.
Further, the invention also provides a visual ammonia injection optimization device based on the concentration of NOx at the outlet of the SCR, which comprises: the system comprises a field data acquisition module, a CFD model establishing module, an influence factor acquisition module, a calculation module and an optimization module;
wherein: the field data acquisition module is used for measuring an inlet of the SCR system under a constant load to acquire field flue gas flow field data;
the CFD model establishing module is used for establishing a CFD model of the SCR system according to the field flue gas flow field data;
the influence factor acquisition module is used for acquiring an ammonia injection influence factor of the SCR system according to the CFD model;
the calculation module is used for establishing an SCR reaction mathematical model corresponding to the SCR system, and calculating the ammonia nitrogen molar ratio distribution of each subarea of the catalyst inlet by combining the SCR reaction mathematical model with the aim of optimizing the concentration distribution uniformity of the NOx at the outlet; wherein the SCR reaction mathematical model is used for outputting a mathematical relationship between outlet NOx concentration and inlet influencing factors;
and the optimization module is used for establishing a matrix equation by coupling ammonia injection influence factors of the SCR system according to the ammonia nitrogen molar ratio distribution of each subarea, solving the matrix equation and obtaining the optimal ammonia injection amount to optimize the SCR system.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: according to the embodiment of the invention, the outlet NOx concentration distribution is most uniform as an optimization target, the ammonia injection amount of the optimized ammonia injection subarea which enables the SCR outlet NOx concentration distribution to be most uniform is obtained through simulation, and the problems of large outlet NOx concentration deviation and large local ammonia escape caused by the current SCR denitration method can be effectively solved.
Drawings
FIG. 1 is a schematic flow diagram of an embodiment of a method for visually optimizing ammonia injection based on SCR outlet NOx concentration distribution provided by the present invention;
FIG. 2 is a schematic three-dimensional overall view of an SCR system in an embodiment of the present invention;
FIG. 3 is a flow cloud of an ammonia trace for a zoned ammonia injection in an embodiment of the present invention;
FIG. 4 is a CSTR model schematic in an embodiment of the present invention;
FIG. 5 is a schematic view of an ammonia injection grid in an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of an embodiment of an ammonia injection device optimized based on the visualization of the SCR outlet NOx concentration distribution provided by the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present protection.
Example one
Referring to fig. 1, an embodiment of a method for visually optimizing ammonia injection based on SCR outlet NOx concentration distribution provided by the present invention includes steps 11 to 15, where each step specifically includes the following steps:
step 11: measuring an inlet of the SCR system under a constant load to obtain field flue gas flow field data;
step 12: according to field flue gas flow field data, establishing a CFD model of the SCR system;
step 13: according to the CFD model, obtaining ammonia injection influence factors of the SCR system;
step 14: establishing an SCR reaction mathematical model corresponding to the SCR system, and calculating to obtain ammonia nitrogen molar ratio distribution of each subarea at the catalyst inlet by combining the SCR reaction mathematical model with the aim of optimizing the distribution uniformity of the concentration of NOx at the outlet; the SCR reaction mathematical model is used for outputting a mathematical relation between the concentration of outlet NOx and inlet influence factors;
step 15: and establishing a matrix equation by coupling ammonia injection influence factors of the SCR system according to the ammonia nitrogen molar ratio distribution of each subarea, and solving the matrix equation to obtain the optimal ammonia injection amount so as to optimize the SCR system.
Further, the measuring of the inlet of the SCR system under constant load to obtain on-site flue gas flow field data specifically includes: measuring the flue gas flow field characteristics of the inlet measuring section of the SCR system by using measuring equipment to obtain a velocity field, a concentration field and a temperature field of the inlet measuring section, and providing inlet parameters for CFD numerical simulation.
It should be noted that the average speed of the inlet of the SCR system is 2.6m/s, the ammonia injection flow rate of each nozzle is calculated to be 0.0410kg/s, and the volume fraction of ammonia is 2.35%.
Further, establishing a CFD model of the SCR system according to the field flue gas flow field data specifically includes: and modeling the whole structure of the CFD model of the SCR system by adopting CFD flow field analysis.
Specifically, as shown in fig. 2, the modeling of the overall structure of the CFD model of the SCR system includes: the device comprises an SCR denitration system inlet 1, an ash bucket 2, a guide plate 3, an ammonia spraying grid 4, a static mixer 5, a guide plate 6, a rectifying grid 7, a catalyst layer 8, a guide plate 9 and an SCR system outlet 10.
Further, after the CFD model of the SCR system is established, the method further includes: and verifying the CFD model of the SCR system and simulating the visual analysis of a flow field, specifically comprising the following steps:
measuring according to the inlet of the SCR system under the constant load to obtain field flue gas flow field data, and reasonably setting simulated inlet boundary conditions; performing numerical calculation in Fluent, comparing a calculation result with the field flue gas flow field data after calculating and determining flow field convergence, and verifying the reliability of the CFD model of the SCR system;
simulation of flue gas and NH with a component transport model3The CFD model of the SCR system is verified by combining the field flue gas flow field data, the trace flow rule of the ammonia gas is analyzed, the actual flue gas flow of the SCR system is reflected, and the simulation flow fields under different working conditions can be visually analyzed.
It is noted that the simulation of flue gas and NH by the component transport model3The mixing process of (1) involving NO and NH3、H2O、CO2、O2And N2Mixing and conveying six components; the finite rate reaction model calculates the chemical reaction related to the SCR system and truly reflects the actual flue gas flow of the SCR system; the 3 catalyst layers were set as porous media zones and the drag coefficients were set by actual pressure drop calculations.
The CFD model of the SCR system is subjected to simulation flow field visual analysis, the flow field visual analysis can be performed on the ammonia gas flowing out of different ammonia injection grids, for example, as shown in figure 3, the ammonia gas is an ammonia trace flowing cloud picture of ammonia injection in a certain subarea, the ammonia gas can be seen to be mixed through entrainment of main stream smoke after being injected, and the ammonia flow diffusion range of each subarea is limited due to the limited mixing distance. When the on-site ammonia injection valve is debugged, when the deviation of NOx in a certain region from the average value is large, the ammonia injection valve influencing the region is found out through the ammonia flow diagram, and the on-site ammonia injection valve can be correspondingly adjusted, so that the debugging efficiency is improved.
Further, the SCR reaction mathematical model is used to output a mathematical relationship between outlet NOx concentration and inlet influencing factors, specifically: cNO,out＝f(α,T,v,CNO,in)；
Wherein C isNO,outIndicates the outlet NOx concentration, CNO,inRepresenting inlet NOx concentration, alpha representing inlet ammonia to nitrogen molar ratio, T representing inlet temperature, v representing inlet flue gas velocity.
It should be noted that, as shown in fig. 4, the SCR reaction mathematical model is a Continuous Stirred Tank Reactor (CSTR) model, which is also commonly called a mixed flow reactor model, and is a reactor with complete and uniform stirring; there is no spatial dependence on the temperature and concentration of the reactants within the reactor, so the exit stream composition from the reactor has the same characteristics as the fluid within the reactor. A CSTR can be described by its material balance, and ideally, the output conditions of one CSTR unit can be used as input conditions for the next unit, and n CSTR units connected end-to-end can simulate the continuous reaction of the reducing agents ammonia and nitroxide in one SCR segment.
The SCR reaction mathematical model is used for outputting a mathematical relation C of outlet NOx concentration and inlet influence factorsNO,out＝f(α,T,v,CNO,in) Obtained from the SCR reaction CTSR model represented by 6 sets of highly nonlinear coupled differential equations of table 1.
TABLE 16 sets of highly nonlinear coupled differential equations
Further, the influence factor quantitatively analyzes the influence of the ammonia spraying amount at the inlet on the ammonia concentration at the inlet of the first-layer catalyst by means of Fluent flow field simulation of the CFD model, the section of the inlet of the catalyst is divided into 12 areas, and the sampling quantity is gridded corresponding to the NOx at the outlet;
the influence factor is defined as follows:
αi: influence factors of different partitions, ri: individual zoned ammonia injection affects the ammonia concentration, R, in a zonei: the ammonia concentration in a certain area is influenced when the ammonia is uniformly sprayed.
It should be noted that a visual ammonia injection optimization method based on the SCR outlet NOx concentration distribution at 100% load is described, and the method is also applicable to other working conditions. The relative deviation of the catalyst inlet speed under 100% load is about 11.4%, which indicates that the flow field of the SCR system is relatively uniform, and the internal flow guide device is reasonably arranged to meet the design requirement of the flow field; the inlet ammonia nitrogen molar ratio relative deviation is 9.3 percent and is more than 5 percent, so that the relative deviation of the outlet NOx concentration is larger, which shows that the problems of poor ammonia nitrogen mixing uniformity, large outlet NOx concentration relative deviation, excessive local ammonia escape and the like exist when an even ammonia spraying mode is adopted, and therefore, the ammonia spraying grid needs to be subjected to subarea ammonia spraying optimization to improve the outlet NOx concentration uniformity.
The influence of the ammonia injection amount at the inlet on the ammonia concentration at the inlet of the first-layer catalyst is quantitatively analyzed by virtue of Fluent flow field simulation, the section of the inlet of the first-layer catalyst is divided into 12 areas named as C11, C12 … … C42 and C43, and the 12 areas correspond to 12 areas of outlet NOx gridding sampling. The definition of the impact factor is:
calculating the ammonia concentration r of a certain area affected by single partition ammonia injectioniInfluencing the ammonia concentration R in a certain region during the uniform ammonia injectioni。
Further, the SCR system includes: the device comprises an inlet flue, an outlet flue, an ammonia injection grid, a guide plate, a static mixer, a rectification grid and a catalyst layer; the ammonia injection grid has 21 groups in total and is provided with 84 nozzles.
It should be noted that 21 groups of the ammonia injection grid are meshed as shown in fig. 6, unstructured grids are adopted at the ammonia injection grid, the guide plate and the mixer, the positions of the nozzles are encrypted, and structured grids are adopted in other regular areas.
Further, the matrix equation is defined as:
for the 21 sets of ammonia injection grids, aiTo liSolving a 21 x 12 matrix equation for the influence factors of each group of ammonia injection grids on 12 areas of the catalyst inlet; y isiRepresenting the optimization target quantity of each partition; xiIndicates each one to be solvedThe ammonia injection amount of each partition.
Further, the solving the matrix equation to obtain the optimal ammonia injection amount to optimize the SCR system specifically includes:
and solving the matrix equation by adopting a gradient descent method of matlab software to obtain the optimal ammonia injection amount of the subareas under different working conditions so as to optimize the subarea ammonia injection amount of the SCR system under different working conditions.
It should be noted that, with the goal of optimal distribution uniformity of outlet NOx concentration, inlet ammonia nitrogen molar ratio distribution is calculated, a matrix equation based on ammonia injection influence factors is coupled to obtain a simulated optimal ammonia injection amount in matlab software, and the optimal ammonia injection amount under a 100% load working condition is taken as a relative value to be converted, so as to obtain the opening degree of the ammonia injection valve. The valve opening ranges from 0 to 100, and as can be seen from table 2, the maximum opening of 21 valves is 90.1, and the minimum opening is 34.0.
TABLE 221 relative opening degree of ammonia injection valve
After the opening degrees of the 21 ammonia injection valves under a certain working condition are obtained through calculation, the ammonia injection valves can be adjusted by combining the debugging experience of the on-site ammonia injection valves and the grid measurement result of the concentration of the NOx at the outlet. When the load changes, the same method is adopted to solve the simulated optimized ammonia spraying amount under the corresponding working condition, the corresponding valve opening is obtained, and finally the average opening of each valve is taken to realize the optimized ammonia spraying of the SCR system and improve the distribution uniformity of the concentration of the NOx at the outlet.
In summary, the invention provides a visual optimized ammonia injection method based on SCR outlet NOx concentration distribution influence factors, a SCR reaction model is established to obtain mathematical relations of catalyst outlet NOx concentration and inlet ammonia nitrogen molar ratio, temperature, speed and the like, the inlet ammonia nitrogen molar ratio distribution is calculated by taking the outlet NOx concentration distribution as the most uniform target, the ammonia injection amount of each ammonia injection subarea is calculated by coupling a matrix equation based on the ammonia injection factors, and the problems of large outlet NOx concentration deviation and large local ammonia escape caused by the current SCR denitration method can be effectively solved.
As shown in fig. 6, a visual optimized ammonia injection device based on SCR outlet NOx concentration distribution according to an embodiment of the present invention includes: the system comprises a field data acquisition module, a CFD model establishing module, an influence factor acquisition module, a calculation module and an optimization module;
wherein: the field data acquisition module is used for measuring an inlet of the SCR system under a constant load to acquire field flue gas flow field data;
the CFD model establishing module is used for establishing a CFD model of the SCR system according to the field flue gas flow field data;
the influence factor acquisition module is used for acquiring an ammonia injection influence factor of the SCR system according to the CFD model;
the calculation module is used for establishing an SCR reaction mathematical model corresponding to the SCR system, and calculating the ammonia nitrogen molar ratio distribution of each subarea of the catalyst inlet by combining the SCR reaction mathematical model with the aim of optimizing the concentration distribution uniformity of the NOx at the outlet; wherein the SCR reaction mathematical model is used for outputting a mathematical relationship between outlet NOx concentration and inlet influencing factors;
and the optimization module is used for establishing a matrix equation by coupling ammonia injection influence factors of the SCR system according to the ammonia nitrogen molar ratio distribution of each subarea, solving the matrix equation and obtaining the optimal ammonia injection amount to optimize the SCR system.
The visualized optimized ammonia injection device based on the concentration of the NOx at the outlet of the SCR provided by the embodiment of the present invention can perform the visualized optimized ammonia injection method based on the concentration of the NOx at the outlet of the SCR provided by the embodiment of the method of the present invention, can perform any combination of the implementation steps of the embodiment of the method, and has the corresponding functions and beneficial effects of the method.
The above-mentioned embodiments are provided to further explain the objects, technical solutions and advantages of the present invention in detail, and it should be understood that the above-mentioned embodiments are only examples of the present invention and are not intended to limit the scope of the present invention. It should be understood that any modifications, equivalents, improvements and the like, which come within the spirit and principle of the invention, may occur to those skilled in the art and are intended to be included within the scope of the invention.
Claims (10)
1. A visualized ammonia injection optimization method based on SCR outlet NOx concentration is characterized by comprising the following steps:
measuring an inlet of the SCR system under a constant load to obtain field flue gas flow field data;
establishing a CFD model of the SCR system according to the field flue gas flow field data;
acquiring an ammonia injection influence factor of the SCR system according to the CFD model;
establishing an SCR reaction mathematical model corresponding to the SCR system, and calculating to obtain ammonia nitrogen molar ratio distribution of each subarea at the catalyst inlet by combining the SCR reaction mathematical model with the aim of optimizing concentration distribution uniformity of outlet NOx; wherein the SCR reaction mathematical model is used for outputting a mathematical relationship between outlet NOx concentration and inlet influencing factors;
and establishing a matrix equation by coupling ammonia injection influence factors of the SCR system according to the ammonia nitrogen molar ratio distribution of each subarea, and solving the matrix equation to obtain the optimal ammonia injection amount so as to optimize the SCR system.
2. The visualized ammonia injection optimization method based on the SCR outlet NOx concentration according to claim 1, wherein the on-site flue gas flow field data is obtained by measuring the inlet of the SCR system under a constant load, and specifically comprises the following steps: and measuring the flue gas flow field characteristics of the inlet measuring section of the SCR system by using measuring equipment to obtain a velocity field, a concentration field and a temperature field of the inlet measuring section, and providing inlet parameters for CFD numerical simulation.
3. The visualized ammonia injection optimization method based on the SCR outlet NOx concentration according to claim 1, wherein the CFD model of the SCR system is established according to the field flue gas flow field data, and specifically comprises the following steps: and modeling the whole structure of the CFD model of the SCR system by adopting CFD flow field analysis.
4. The method of claim 1, after establishing the CFD model of the SCR system, further comprising: and verifying the CFD model of the SCR system and simulating the visual analysis of a flow field, specifically comprising the following steps:
measuring according to the inlet of the SCR system under the constant load to obtain field flue gas flow field data, and reasonably setting simulated inlet boundary conditions; performing numerical calculation in Fluent, comparing a calculation result with the field flue gas flow field data after calculating and determining flow field convergence, and verifying the reliability of the CFD model of the SCR system;
simulation of flue gas and NH with a component transport model3The CFD model of the SCR system is verified by combining the field flue gas flow field data, the trace flow rule of the ammonia gas is analyzed, the actual flue gas flow of the SCR system is reflected, and the simulation flow fields under different working conditions can be visually analyzed.
5. The method for optimizing visualized ammonia injection based on the SCR outlet NOx concentration according to claim 1, wherein the SCR reaction mathematical model is used for outputting a mathematical relationship between the outlet NOx concentration and the inlet influencing factors, and specifically comprises the following steps: cNo,out＝f(α,T,c,CNO,in)；
Wherein C isNO,outIndicates the outlet NOx concentration, CNO,inShowing inlet NOx concentration, alpha inlet ammonia nitrogen molar ratio, T inlet temperature, v inlet flue gas velocity.
6. The visualized ammonia injection optimization method based on the SCR outlet NOx concentration according to claim 1, wherein the influence factors quantitatively analyze the influence of the inlet ammonia injection amount on the inlet ammonia concentration of the first-layer catalyst by means of Fluent flow field simulation of the CFD model, the inlet section of the catalyst is divided into 12 areas, and the grid sampling number of the outlet NOx is corresponded;
the influence factor is defined as follows:
αi: influence factors of different partitions, ri: individual zoned ammonia injection affects the ammonia concentration, R, in a zonei: the ammonia concentration in a certain area is influenced when the ammonia is uniformly sprayed.
7. The method for visual ammonia injection optimization based on the SCR outlet NOx concentration according to any one of claims 1 to 6, characterized in that the SCR system comprises: the inlet and outlet flue, the ammonia injection grid, the guide plate, the static mixer, the rectification grid and the catalyst layer; the ammonia injection grid has 21 groups in total and is provided with 84 nozzles.
8. The method of claim 7, wherein the matrix equation is defined as:
for the 21 sets of ammonia injection grids, aiTo liSolving a 21 x 12 matrix equation for the influence factors of each group of ammonia injection grids on 12 areas of the catalyst inlet; y isiRepresenting the optimization target quantity of each partition; xiIndicating the amount of ammonia injection to be required for each partition.
9. The method for optimizing visualized ammonia injection based on the concentration of NOx at the outlet of SCR according to claim 8, wherein the matrix equation is solved to obtain the optimal ammonia injection amount to optimize the SCR system, specifically:
and solving the matrix equation by adopting a gradient descent method of matlab software to obtain the optimal ammonia injection amount of the subareas under different working conditions so as to optimize the subarea ammonia injection amount of the SCR system under different working conditions.
10. A visual ammonia injection optimization device based on SCR outlet NOx concentration, characterized by comprising: the system comprises a field data acquisition module, a CFD model establishing module, an influence factor acquisition module, a calculation module and an optimization module;
wherein: the field data acquisition module is used for measuring an inlet of the SCR system under a constant load to acquire field flue gas flow field data;
the CFD model establishing module is used for establishing a CFD model of the SCR system according to the field flue gas flow field data;
the influence factor acquisition module is used for acquiring an ammonia injection influence factor of the SCR system according to the CFD model;
the calculation module is used for establishing an SCR reaction mathematical model corresponding to the SCR system, and calculating the ammonia nitrogen molar ratio distribution of each subarea at the catalyst inlet by combining the SCR reaction mathematical model with the aim of optimizing the concentration distribution uniformity of the NOx at the outlet; wherein the SCR reaction mathematical model is used for outputting a mathematical relationship between outlet NOx concentration and inlet influencing factors;
and the optimization module is used for establishing a matrix equation by coupling ammonia injection influence factors of the SCR system according to the ammonia nitrogen molar ratio distribution of each subarea, solving the matrix equation and obtaining the optimal ammonia injection amount so as to optimize the SCR system.
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