CN115099171A - Method for obtaining flue gas flow field distribution characteristics of catalyst layer flue section of SCR system - Google Patents
Method for obtaining flue gas flow field distribution characteristics of catalyst layer flue section of SCR system Download PDFInfo
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 239000003546 flue gas Substances 0.000 title claims abstract description 55
- 239000003054 catalyst Substances 0.000 title claims abstract description 51
- 238000000034 method Methods 0.000 title claims abstract description 35
- 239000000523 sample Substances 0.000 claims abstract description 17
- 239000000779 smoke Substances 0.000 claims abstract description 16
- 238000005259 measurement Methods 0.000 claims abstract description 15
- 238000005192 partition Methods 0.000 claims abstract description 12
- 238000000638 solvent extraction Methods 0.000 claims abstract description 9
- 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
- 238000004088 simulation Methods 0.000 claims abstract description 6
- 238000011160 research Methods 0.000 claims abstract description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 12
- 238000012360 testing method Methods 0.000 claims description 8
- 229910021529 ammonia Inorganic materials 0.000 claims description 6
- 238000002347 injection Methods 0.000 claims description 6
- 239000007924 injection Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 3
- 238000000827 velocimetry Methods 0.000 claims description 3
- 230000003068 static effect Effects 0.000 claims description 2
- 238000011077 uniformity evaluation Methods 0.000 claims description 2
- 230000002349 favourable effect Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 240000004282 Grewia occidentalis Species 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 206010022000 influenza Diseases 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G06F30/28—Design optimisation, verification or simulation using fluid dynamics, e.g. using Navier-Stokes equations or computational fluid dynamics [CFD]
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Abstract
The invention relates to a method for acquiring flue gas flow field distribution characteristics of a catalyst layer flue section of an SCR system, which comprises the following steps: measuring the smoke flow velocity of discrete measuring points in the cross section of a small flue at the front end of the SCR system under a plurality of groups of constant load working conditions by a rectangular grid point distribution mode based on a speed measuring instrument; step two: constructing a geometric model, developing CFD simulation research based on an inlet boundary and an outlet boundary, and predicting to obtain the distribution characteristics of flue gas flow fields of the flue sections of the catalyst layers under a plurality of groups of constant-load working conditions; step three: based on a flow coupling physical partitioning method, partitioning a plurality of groups of flue sections under a constant load working condition; step four: and analyzing the flow velocity change rule in each flue section partition under the constant/variable load working condition to form a smoke speed measuring probe arrangement scheme. The method provides a feasible method for accurately obtaining the distribution characteristics of the flue gas flow field of the cross section of the catalyst layer flue of the SCR system, has the favorable characteristic of low-cost distributed speed measurement, and is helpful for assisting in diagnosing the denitration performance of the SCR system.
Description
Technical Field
The invention relates to the technical field of heat energy and power engineering, in particular to a method for acquiring distribution characteristics of flue gas flow field of a catalyst layer flue section of an SCR system.
Background
The distribution of the flue gas flow field of the coal-fired equipment has important guiding significance for the optimized operation of the coal-fired equipment. The flue structure of a large coal-fired power plant is complex, the cross section of the flue is large, the flue flow field inside the flue is disordered, the position of a stable point which can represent the average flow velocity of the cross section inside the flue is difficult to determine, and the cost can be greatly increased by greatly increasing the number of measuring points.
In recent years, researchers propose to perform partition measurement of flue gas flow field distribution characteristics in a flue of a catalyst layer of an SCR system, but how to partition regions and arrange measuring points depends on accumulation of experience, and a uniform and feasible method is not available.
Currently, a Selective Catalytic Reduction (SCR) denitration system is widely applied to flue gas denitration engineering of coal-fired equipment due to excellent denitration performance, and is particularly directed to a large-sized coal-fired generator set. The flue section of the large-scale coal-fired generating set is extremely large, the size of the flue section of the SCR system reactor of the conventional 660 MW-level coal-fired generating set can reach about 15m multiplied by 1 m, in the large flue section, the accuracy of the result cannot be ensured only by means of the existing flue gas emission continuous detection system or by carrying out simple single-point or multi-point measurement on the flow velocity of flue gas in the flue, and the multi-point measurement cost is high and is lack of rationality.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for acquiring the distribution characteristics of the flue gas flow field of the cross section of the catalyst layer flue of the SCR system, which solves the problems of inaccurate measurement result and high measurement cost of the flue gas flow velocity in the cross section of the catalyst layer flue of the SCR system of coal-fired equipment, and realizes the accurate and low-cost acquisition of the distribution characteristics of the flue gas flow field of the cross section of the catalyst layer flue of the SCR system.
The invention is realized by the following technical scheme:
the method for acquiring the flue gas flow field distribution characteristics of the cross section of the catalyst layer flue of the SCR system comprises the following steps:
the method comprises the following steps: directly measuring to obtain the flue gas flow velocity of discrete measuring points in the section of a small flue at the front end of the SCR system under a plurality of groups of constant load working conditions by a rectangular grid point distribution mode based on a speed measuring instrument; wherein:
the rectangular grid distribution takes a connecting line of the positions of the temporary test holes of the flue as an X axis, and the grid distance in the direction is determined by the positions of the temporary test holes; a straight line perpendicular to the X axis in this cross section is taken as the Y axis, and the grid pitch Δ Y in this direction follows the following principle:
in the formula: l is s The size of the cross section of the small flue in the Y-axis direction; i is the number of the measuring points arranged along the Y-axis direction;
step two: constructing a geometric model of the front-end small flue section to the end layer catalyst layer flue section, wherein the geometric model comprises an ammonia injection grid, a rectification grid, a static mixer and a guide plate internal component, and on the basis, developing CFD simulation research based on reasonable inlet boundary and outlet boundary to predict and obtain the flue gas flow field distribution characteristics of the catalyst layer flue section under a plurality of groups of constant-load working conditions;
step three: dividing the flue sections under a plurality of groups of constant load working conditions into a high-speed area, a medium-speed area, a low-speed area and a mixed flow velocity area based on a flow coupling physical partitioning method;
wherein:
physical partitioning: dividing the flue section of the final catalyst layer into m multiplied by n small areas in an equal area mode, and equally dividing the section into m parts along the X-axis direction and n parts along the Y-axis direction;
the value principles of m and n are as follows:
if the boiler matched with the SCR system is a four-corner tangential boiler, m is 3;
if the boiler matched with the SCR system is a front-wall and rear-wall opposed boiler, m is 5;
if the boiler matched with the SCR system is other types of boilers, taking m as 4;
in the formula: l is x The size of the cross section of the flue of the final catalyst layer in the X-axis direction; l is y The size of the cross section of the flue of the final catalyst layer in the Y-axis direction; m is the number of equal parts of the section along the X-axis direction; xi is an empirical coefficient, and 0.75 is taken; r2]Rounding to an integer function;
flow coupling:
setting the mark numbers of the high-speed area, the medium-speed area, the Low-speed area and the mixed flow velocity area as Hig, Mid, Low and Mix respectively, and the classification judgment principle based on the regional flue gas flow velocity characteristic is as follows:
in the formula: v is the average flow velocity of the flue gas in each small region with equal area;
the average flow velocity of the flue gas in the flue section of the final catalyst layer; c v The relative standard deviation of the index is judged for uniformity, and the relative flow rate in the cross section isThe ratio of the standard deviation to the mean;
step four: analyzing the flow velocity change rule in each flue section subarea under the constant/variable load working condition to form a representative fixed or movable smoke velocity measurement probe arrangement scheme, and accurately acquiring the smoke flow field distribution characteristics of the flue section of the catalyst layer through discrete point subarea smoke velocity measurement.
Further, in the first step, the speed measuring instrument is one of an L-shaped pitot tube, an S-shaped pitot tube or an electrostatic flow velocity sensor.
Further, in the step one, the multiple groups of constant load conditions refer to three constant load conditions of 100% BMCR, 75% BMCR and 50% BMCR.
Furthermore, in the step one, the section of the front-end small flue is positioned from the horizontal flue behind the economizer to the front of the ammonia injection grid, the section area is minimized as a preferential selection principle, the section is provided with a temporary test hole, and the size of the short side of the section is less than or equal to 4.5 m.
Further, in the second step, the combination of the infinitesimal areas represented by the discrete measuring points is used as an inlet boundary, infinitesimal area division is realized by aiming at the quartering of the rectangular grid in the first step, the flue gas flow velocity measurement value with the spatial position closest to the discrete measuring points is taken as the speed average value of the infinitesimal areas, and the inlet boundary adopts a speed inlet boundary condition.
Furthermore, in the second step, the flue section of the final catalyst layer is used as an outlet boundary, and a free flow outlet boundary or a pressure outlet boundary condition is adopted.
Further, when analyzing the flow speed change rule in each flue section subarea under the constant/variable load working condition, firstly, integrating three groups of constant load working condition operation characteristics and respectively determining the mark code numbers of m multiplied by n small areas; for any small area, taking the mark code with the highest repetition degree in the three groups of working conditions as the standard mark code; if the mark codes of the three groups of working conditions of a certain small area are different, the mark code of the working condition closest to the average load of the unit is taken as the standard mark code.
Further, the average load of the unit is that the real-time load of the unit with a continuous measuring period of not less than 168 hours is taken as historical operation data, and the time interval of the taken historical operation data is not less than 15 seconds.
Furthermore, in the fourth step, each flue section partition under the constant/variable load condition refers to a plurality of connected or isolated flue section partitions formed by combining adjacent small areas with the same standard mark code in m × n small areas.
Furthermore, in the fourth step, when a fixed or movable smoke speed measuring probe arrangement scheme is formed, for the low-speed area, the medium-speed area and the high-speed area, the side which is closest to the X axis and the Y axis and has the shortest length is taken from the sides parallel to the X axis and the Y axis, the sides are respectively taken as the center lines of the two sides, and a fixed speed measuring probe is arranged at the intersection point of the two center lines; for the mixed flow velocity area, the distance between the movable speed measuring probe and the X axis and the distance between the movable speed measuring probe and the Y axis from the leftmost upper part of the area are both L y Starting at/3 n, the region is followed by a distance region profile L y The/3 n straight line is moved in a clockwise cycle at a rate of 0.5-0.8 m/s.
The invention has the beneficial effects that:
compared with the prior art, the method obtains the flue gas flow field distribution characteristics of the flue section of the catalyst layer under the working conditions of multiple groups of constant loads based on CFD simulation research on the basis of directly measuring the flue gas flow speed in the small flue section at the front end of the SCR system, further designs a flow coupling physical partitioning method, partitions the flue section under the working conditions of multiple groups of constant loads according to the method, and finally analyzes the flow speed change rule in each flue section partition under the working conditions of constant/variable loads to form a representative fixed or movable flue gas velocity measurement probe arrangement scheme, thereby accurately obtaining the flue gas flow field distribution characteristics of the flue section of the catalyst layer.
The method provides a feasible method for accurately acquiring the distribution characteristics of the flue gas flow field of the catalyst layer flue section of the SCR system, has the beneficial characteristics of low cost and distributed speed measurement, and is helpful for assisting in diagnosing the denitration performance of the SCR system.
Drawings
FIG. 1 is a block flow diagram of the present invention.
FIG. 2 is a diagram of a CFD simulation based on reasonable entrance and exit boundaries in an embodiment of the present invention.
Fig. 3 is a diagram of the partitions and the symbol numbers under three constant conditions obtained based on the flow coupling physical partitioning method in the embodiment of the present invention.
Fig. 4 is a standard sign plot of 3 × 3 small regions in an embodiment of the present invention.
Fig. 5 is a sectional view of a plurality of connected or isolated flues formed by combining adjacent small areas with the same standard mark number in 3 × 3 small areas according to the embodiment of the invention.
Fig. 6 shows the arrangement scheme and the movement track of the fixed or movable smoke velocimetry probe in the embodiment of the invention.
FIG. 7 shows the flue gas flow velocity distribution of discrete measuring points in the section of a small flue at the front end of an SCR system under the 100% BMCR working condition.
FIG. 8 shows the flue gas flow velocity distribution of discrete measuring points in the section of a small flue at the front end of an SCR system under the 75% BMCR working condition.
FIG. 9 is a smoke flow velocity distribution of discrete measuring points in a small flue section at the front end of an SCR system under a 50% BMCR working condition.
Detailed Description
In order to clearly illustrate the technical features of the present solution, the present solution is explained below by way of specific embodiments.
The embodiment is applied to an SCR system of a 660MW coal-fired generator set, and the method for acquiring the distribution characteristics of the flue gas flow field of the cross section of the catalyst layer flue of the SCR system comprises the following specific steps:
the method comprises the following steps: based on a speed measuring instrument, the smoke flow velocity of discrete measuring points in the section of a small flue at the front end of the SCR system under the working condition of multiple groups of constant loads is directly measured in a rectangular grid point distribution mode. The speed measuring instrument can select one of an L-shaped pitot tube, an S-shaped pitot tube or an electrostatic flow velocity sensor to measure the flow velocity of the flue gas in the section of the small flue.
Three constant load working conditions of 100% BMCR, 75% BMCR and 50% BMCR are selected as a sample to carry out measurement and analysis, and the flow rate of the smoke is measured on the small flue section at the front end of the SCR system in a rectangular grid point distribution mode. And a connecting line of the positions of the temporary test holes of the flue is taken as an X axis, and the grid distance in the direction is determined by the positions of the temporary test holes. A straight line perpendicular to the X axis in this cross section is taken as the Y axis, and the grid pitch Δ Y in this direction follows the following principle:
in the formula: l is s The size of the cross section of the small flue in the Y-axis direction; i is the number of stations arranged in the direction of the Y axis.
The length of the small flue section at the front end of the SCR system in the Y-axis direction is 3 meters, 3 measuring points are arranged, and the grid distance delta Y is 0.75 m.
On the basis of constructing a geometric model, taking the combination of the infinitesimal areas represented by the discrete measuring points as an inlet boundary, realizing infinitesimal area division by aiming at the quartering of a rectangular grid with a small section of a flue, and taking the flue gas flow velocity measurement value (shown in figures 7, 8 and 9) with the spatial position closest to the discrete measuring points as the speed mean value of the infinitesimal areas; the flue section of the final catalyst layer is taken as an outlet boundary.
As shown in fig. 2, based on the boundary conditions, a CFD simulation study is performed, and the distribution characteristics of the flue gas flow field of the cross section of the catalyst layer flue under a plurality of groups of constant-load conditions are predicted.
Based on a flow coupling physical partitioning method, dividing the cross section of a flue of a final catalyst layer into m multiplied by n small areas in an equal area mode, and equally dividing the cross section into m parts along the X-axis direction and n parts along the Y-axis direction; the value principle of m and n is as follows:
in the formula: l is x The size of the flue section of the final catalyst layer in the X-axis direction; l is y The size of the flue section of the final catalyst layer in the Y-axis direction; m is the number of equal parts of the section along the X-axis direction;xi is an empirical coefficient, and 0.75 is taken; r2]Rounding to an integer function.
In the embodiment, the boiler matched with the SCR system is a four-corner tangential boiler, and m is 3; the length of the flue section of the final catalyst layer in the X-axis direction is 15m, the length of the flue section in the Y-axis direction is 12m, and n is 3.
Dividing the 3 x 3 small area into a high-speed area, a medium-speed area, a Low-speed area and a mixed flow rate area under three constant load working conditions of 100% BMCR, 75% BMCR and 50% BMCR, wherein the mark numbers are Hig, Mid, Low and Mix respectively, and the division result is shown in figure 3.
The classification judgment principle based on the regional flue gas flow velocity characteristics is as follows:
in the formula: v is the average flow velocity of the flue gas in each small area with equal area;
the average flow velocity of the flue gas in the flue section of the final catalyst layer; c v The relative standard deviation of the uniformity evaluation index is the ratio of the relative standard deviation of the flow rate in the cross section to the mean value.
And after the division is finished, the standard mark code number of the 3 multiplied by 3 small region is determined by integrating the operating characteristics of the three groups of constant load working conditions. For any small area, the mark code with the highest repetition degree in the three groups of working conditions is taken as the standard mark code; if the sign code numbers of a certain small region in the three groups of working conditions are different, the sign code number of the working condition closest to the average load of the unit is taken as the standard sign code number of the small region, and finally the result of the small region partition is shown in the attached figure 4.
And combining the adjacent small areas with the same standard mark code in the 3 x 3 small areas to form a plurality of communicated or isolated flue section subareas, as shown in fig. 5. And analyzing the flow velocity change rule in each flue section partition under the constant/variable load working condition to form a representative fixed or movable smoke speed measuring probe arrangement scheme. For the low-speed area, the medium-speed area and the high-speed area, selecting the side which is closest to the X axis and the Y axis and has the shortest length from the sides parallel to the X axis and the Y axis, respectively making central lines on the two sides, and arranging a fixed speed measuring probe at the intersection of the two central lines; for a mixed flow velocity area, starting from a position where the distance between the leftmost upper part of the area and the X axis and the distance between the leftmost upper part of the area and the Y axis are both 1.33m, and performing clockwise cyclic movement in the area along a straight line which is 1.33m away from the outline of the area; the moving speed is 0.5-0.8 m/s. The arrangement scheme and the motion trail of the finally formed fixed or movable smoke speed measuring probe are shown in the attached figure 6.
The flue gas flow field distribution characteristics of the flue section of the catalyst layer are accurately obtained by the discrete point regional flue gas velocity measurement method.
The embodiment can show that the method for accurately obtaining the distribution characteristics of the flue gas flow field of the catalyst layer flue section of the SCR system can realize low-cost accurate measurement of the distribution characteristics of the flue gas flow field of the catalyst layer flue section of the SCR system by substituting the numerical values of corresponding parameters in the formula, further obtain accurate quantification of the regional ammonia injection amount and the total ammonia injection amount of the flue section of the SCR system, and provide a data basis for the operation optimization and adjustment of a subsequent system.
Of course, the above description is not limited to the above examples, and the undescribed technical features of the present invention may be implemented by or using the prior art, which is not described herein again; the above embodiments and drawings are only for illustrating the technical solutions of the present invention and not for limiting the present invention, and the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that changes, modifications, additions or substitutions within the spirit and scope of the present invention may be made by those skilled in the art without departing from the spirit of the present invention, and shall also fall within the scope of the claims of the present invention.
Claims (10)
1. A method for obtaining flue gas flow field distribution characteristics of a catalyst layer flue section of an SCR system is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: directly measuring to obtain the flue gas flow velocity of discrete measuring points in the section of a small flue at the front end of the SCR system under a plurality of groups of constant-load working conditions by a rectangular grid point distribution mode based on a speed measuring instrument; wherein:
the rectangular grid distribution takes a connecting line of the positions of the temporary test holes of the flue as an X axis, and the grid distance in the direction is determined by the positions of the temporary test holes; a straight line perpendicular to the X axis in this cross section is taken as the Y axis, and the grid pitch Δ Y in this direction follows the following principle:
in the formula: l is s The size of the cross section of the small flue in the Y-axis direction; i is the number of the measuring points arranged along the Y-axis direction;
step two: constructing a geometric model of the front-end small flue section to the end layer catalyst layer flue section, wherein the geometric model comprises an ammonia injection grid, a rectification grid, a static mixer and a guide plate internal component, and on the basis, developing CFD simulation research based on reasonable inlet boundary and outlet boundary to predict and obtain the flue gas flow field distribution characteristics of the catalyst layer flue section under a plurality of groups of constant-load working conditions;
step three: dividing the flue sections under a plurality of groups of constant load working conditions into a high-speed area, a medium-speed area, a low-speed area and a mixed flow velocity area based on a flow coupling physical partitioning method;
wherein:
physical partitioning: dividing the section of a flue of the final catalyst layer into m multiplied by n small regions in an equal area, and equally dividing the section into m parts along the X-axis direction and n parts along the Y-axis direction;
the value principles of m and n are as follows:
if the boiler matched with the SCR system is a quadrangle tangential boiler, m is 3;
if the boiler matched with the SCR system is a front-wall and rear-wall opposed boiler, taking m as 5;
if the boiler matched with the SCR system is other types of boilers, taking m as 4;
in the formula: l is x The size of the cross section of the flue of the final catalyst layer in the X-axis direction; l is y The size of the cross section of the flue of the final catalyst layer in the Y-axis direction; m is the number of equal parts of the section along the X-axis direction; xi is an empirical coefficient, and 0.75 is taken; r2]Rounding to a rounding function;
flow coupling:
setting the mark numbers of the high-speed zone, the medium-speed zone, the Low-speed zone and the mixed flow velocity zone as Hig, Mid, Low and Mix respectively, and based on the classification judgment principle of the regional flue gas flow velocity characteristics, the classification judgment principle is as follows:
in the formula: v is the average flow velocity of the flue gas in each small area with equal area;
the average flow velocity of the flue gas in the flue section of the final catalyst layer; c v The relative standard deviation of the uniformity evaluation index is the ratio of the relative standard deviation of the flow velocity in the cross section to the mean value;
step four: analyzing the flow velocity change rule in each flue section subarea under the constant/variable load working condition to form a representative fixed or movable smoke velocimetry probe arrangement scheme, and accurately obtaining the distribution characteristics of the catalyst layer flue section smoke flow field through discrete point subarea smoke velocimetry.
2. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: in step one, the speed measuring instrument is one of an L-shaped pitot tube, an S-shaped pitot tube or an electrostatic flow velocity sensor.
3. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: in the first step, the multiple groups of constant load conditions refer to three constant load conditions of 100% BMCR, 75% BMCR and 50% BMCR.
4. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: in the first step, the section of the front small flue is positioned from the horizontal flue behind the economizer to the front of the ammonia injection grid, the section area is minimized as a preferential selection principle, the section is provided with a temporary test hole, and the size of the short side of the section is less than or equal to 4.5 m.
5. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: in the second step, the combination of the infinitesimal areas represented by the discrete measuring points is used as an inlet boundary, infinitesimal area division is realized by aiming at the quartering of the rectangular grid in the first step, the velocity mean value of the infinitesimal areas is the flue gas flow velocity measurement value with the spatial position closest to the discrete measuring points, and the inlet boundary adopts a velocity inlet boundary condition.
6. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: in the second step, the flue section of the final catalyst layer is taken as an outlet boundary, and a free flow outlet boundary or a pressure outlet boundary condition is adopted.
7. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: when analyzing the flow velocity change rule in each flue section subarea under the constant/variable load working condition, firstly, integrating the operating characteristics of three groups of constant load working conditions and respectively determining the mark codes of m multiplied by n small areas; for any small area, the mark code with the highest repetition degree in the three groups of working conditions is taken as the standard mark code; if the mark codes of the three groups of working conditions of a certain small area are different, the mark code of the working condition closest to the average load of the unit is taken as the standard mark code.
8. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 7, is characterized in that: the average load of the unit is that the real-time load of the unit with a continuous measuring period of not less than 168 hours is taken as historical operating data, and the time interval of the taken historical operating data is not less than 15 seconds.
9. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: in the fourth step, each flue section partition under the constant/variable load working condition refers to a plurality of connected or isolated flue section partitions formed by combining adjacent small areas with the same standard mark code in m × n small areas.
10. The method for acquiring the flue section flue gas flow field distribution characteristics of the SCR system catalyst layer according to claim 1, is characterized in that: in the fourth step, when a fixed or movable smoke speed measuring probe arrangement scheme is formed, for a low-speed area, a medium-speed area and a high-speed area, the side which is closest to the X axis and the Y axis and has the shortest length is taken from the sides parallel to the X axis and the Y axis, the sides are respectively taken as the center lines of the two sides, and a fixed speed measuring probe is arranged at the intersection point of the two center lines; for the mixed flow velocity area, the distance between the movable speed measuring probe and the X axis and the distance between the movable speed measuring probe and the Y axis from the leftmost upper part of the area are both L y Starting at/3 n, the region is followed by a distance region profile L y The/3 n straight line moves in a clockwise cycle at a speed of 0.5-0.8 m/s.
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