Accurate ammonia spraying anti-blocking system for SCR denitration of coal-fired unit

Abstract

The invention discloses a coal-fired unit SCR denitration accurate ammonia spraying anti-blocking system which is characterized in that a whole denitration flue is divided into a plurality of ammonia spraying blocks, each group of ammonia spraying blocks comprises an ammonia spraying main pipe and a plurality of ammonia spraying branch pipes which are communicated with each other, and the ammonia spraying branch pipes are further connected with a purging pipeline; and the flow of one ammonia spraying branch pipe is compared with the average flow value of all the ammonia spraying branch pipes of the whole block, a deviation value delta is obtained, and the valve on the corresponding purging pipeline is adjusted to be opened and closed according to the range of the deviation value. The flow sensor is used for measuring the flow of the ammonia spraying branch pipe, the ammonia spraying flow in the ammonia spraying branch pipe is judged, the flow of the ammonia spraying branch pipe is compared with the average flow value of the whole partitioned ammonia spraying branch pipe, whether the branch pipe is blocked or not is judged according to the comparison deviation value, compressed air in the corresponding purging pipeline is used for purging, and therefore the ammonia spraying branch pipe is prevented from being blocked; the uniformity of ammonia spraying is ensured, and over-spraying of partial areas in the denitration flue can be effectively prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired boiler denitration, and in particular to a SCR denitration precision ammonia injection anti-blocking system for a coal-fired unit. Background Art

[0002] As the proportion of renewable energy power generation increases, it is imperative to increase the adjustable range of thermal power units. Most units increase the adjustable range of units by flexible peak-shaving transformation. As the load is further reduced and more flexible, higher performance requirements are placed on denitrification equipment. Therefore, more and more coal-fired units are starting to put into operation precise ammonia injection denitrification systems.

[0003] Since most precision ammonia injection denitrification systems use block ammonia injection, that is, the entire denitrification flue is divided into several blocks, each of which is composed of an ammonia injection main pipe and several ammonia injection branch pipes. The precision ammonia injection denitrification system generally only automatically controls the ammonia injection amount of the ammonia injection main pipe, and cannot effectively control the ammonia injection amount of the ammonia injection branch pipe in the block. When the inner wall of the ammonia injection branch pipe is adhered by fly ash and hydrolyzed urea crystals, the resistance of the ammonia injection branch pipe will increase. When the manual valve opening of the ammonia injection branch pipe in the block is consistent, the ammonia injection amount in the block denitrification flue will be uneven, causing overspray in some areas of the block denitrification flue. Ammonia will form ammonium bisulfate with sulfur dioxide and oxygen. Ammonium bisulfate is a viscous substance. When ammonium bisulfate is deposited in the tail flue of the boiler, it will cause the tail flue to be blocked, affecting the safety of the unit operation. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to provide a system for preventing blockage of precise ammonia injection in the SCR denitrification flue of a coal-fired unit.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A coal-fired unit SCR denitration precise ammonia injection anti-blocking system, which divides the entire denitration flue into a number of ammonia injection blocks, each group of ammonia injection blocks includes an ammonia injection main pipe and a number of ammonia injection branch pipes, wherein the ammonia injection main pipe is connected to a number of ammonia injection branch pipes through an ammonia injection grid, and the ammonia injection branch pipes are also connected to a purge pipeline;

[0007] A flow sensor is provided at the inlet of the ammonia injection branch pipe;

[0008] The flow rate of an ammonia injection branch pipe is compared with the average flow rate of all ammonia injection branch pipes in the entire block to obtain a deviation value δ. According to the range of the deviation value, the opening and closing degree of the valve on the corresponding purge pipeline is adjusted.

[0009] The present invention sets a flow sensor at the inlet of the ammonia spray branch pipe. The flow sensor measures the ammonia flow of the ammonia spray branch pipe, which is used to determine the flow of the ammonia spray amount in the ammonia spray branch pipe, compare the flow of the ammonia spray branch pipe with the average flow of the ammonia spray branch pipe in the entire block, and use the comparison deviation value to determine whether the branch pipe is blocked, and then use the compressed air in the corresponding purge pipe to purge it, so as to dredge it. The above design can accurately determine whether the branch pipe is blocked, and can timely dredge the blocked ammonia spray branch pipe, ensure the uniformity of ammonia spray in the block, and effectively prevent overspray in some areas of the denitrification flue.

[0010] As a further solution of the present invention: the i-th ammonia injection branch pipe of the first sub-block A1 on the A side is A i , another ammonia spray branch pipe A i The flow rate in the tube is q i ;

[0011] Then the calculation formula for the average flow rate Q1 of all ammonia injection branches in the block is:

[0012]

[0013] Then q i The calculation formula for the deviation value δ from Q1 is:

[0014] δ=(q i -Q1) / Q1*100 (2).

[0015] As a further solution of the present invention: when the flow deviation value δ of the ammonia injection branch pipe is greater than 20%, the ammonia injection branch pipe A i Reduce the valve opening on the corresponding purge pipeline;

[0016] When the flow deviation value δ of the ammonia injection branch pipe is less than minus 20%, the ammonia injection branch pipe A i The valve opening on the corresponding purge pipeline increases;

[0017] When the absolute value of the flow deviation value δ of the ammonia injection branch pipe is less than 10%, the ammonia injection branch pipe A i The main pipe valve on the corresponding purge pipeline is closed.

[0018] As a further solution of the present invention: when the absolute value of the flow deviation value δ of the ammonia injection branch pipe in the A1 block is less than 10%:

[0019] The average flow rate of the ammonia injection branch pipe in the A1 block Q1 is compared with the average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue Q s Make a comparison and get the deviation value X;

[0020] C that exports A1 in blocks NOx1 The concentration value and the average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue CNOxi Make a comparison and get the deviation value Y;

[0021] According to the range of the deviation value X and the deviation value Y, adjust the opening and closing of the valve on the corresponding purge pipeline.

[0022] As a further solution of the present invention: the average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue is Q s The calculation formula is:

[0023]

[0024] In the formula, Q i is the average flow rate of the ammonia injection branch pipe in the i-th block.

[0025] As a further solution of the present invention: the calculation formula of the deviation value X is:

[0026] X=(Q1-Q s ) / Q1*100 (4).

[0027] As a further solution of the present invention: the calculation formula of the deviation value Y is:

[0028] Y=(C NOx1 -C NOxi ) / C NOxi *100 (5).

[0029] As a further solution of the present invention: when the average flow rate Q1 of the ammonia injection branch pipe in the A1 block is less than the average flow rate Q1 of the ammonia injection branch pipe in all blocks s Value, when the deviation value X is less than 20%;

[0030] And A1 block exit C NOx1 The concentration value is greater than the average flow rate of the ammonia injection branch pipe in all blocks C NOxi When the Y value is greater than 20%, it is judged that all ammonia spray branch pipes in the A1 block area on the A side are blocked, then open the main pipe valve of the purge pipeline corresponding to the A1 ammonia spray branch pipe, and fully open the branch pipe valve of the purge pipeline;

[0031] When the deviation value X and the deviation value Y do not meet the above requirements, the valve opening of the ammonia injection branch pipe and the purge branch pipe is maintained unchanged.

[0032] As a further solution of the present invention: the purge pipeline includes a compressed air purge branch pipe and a compressed air purge main pipe, wherein the compressed air purge branch pipe is provided with a plurality of groups, which are respectively connected to the corresponding ammonia injection branch pipes through the ammonia injection grid, and the other end of the compressed air purge branch pipe is connected to the compressed air purge main pipe;

[0033] A compressed air purge branch pipe valve is installed in each of the compressed air purge branch pipes; a compressed air purge main pipe valve is installed in the compressed air purge main pipe.

[0034] As a further solution of the present invention: the outlet pressure of the compressed air purge branch pipe is 0.6-1.0 MPa.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] First, the present invention sets a flow sensor at the inlet of the ammonia spray branch pipe. The flow sensor measures the ammonia flow rate of the ammonia spray branch pipe, which is used to determine the flow rate of the ammonia spray amount in the ammonia spray branch pipe. The flow rate of the ammonia spray branch pipe is compared with the average flow rate of the entire block ammonia spray branch pipe, and the comparison deviation value is used to determine whether the branch pipe is blocked, and then the compressed air in the corresponding purge pipe is used to purge it for unblocking. The above design can accurately determine whether the branch pipe is blocked, and can timely purge with compressed air to reduce the blockage degree of the ammonia spray pipeline, ensure the uniformity of ammonia spray, and further prevent the phenomenon of overspray in some areas of the denitrification flue;

[0037] Secondly, when the flow deviation value between a certain ammonia injection branch pipe in a specific block and the ammonia injection branch pipe of the entire block is lower than a certain level, it is necessary to further compare the average ammonia injection flow rate of the entire block with the average ammonia injection flow rate of all separate areas in the entire area to obtain the corresponding deviation value. If the deviation value is within the corresponding range, normal purge is maintained; if it is not within the corresponding range, the purge valve of the entire block is further adjusted to achieve accurate judgment of the blocked ammonia injection branch pipe and corresponding purge treatment, thereby ensuring the accuracy of ammonia injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a structural schematic diagram of a coal-fired unit SCR denitration precision ammonia injection anti-blocking system according to an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of an ammonia injection grid and an ammonia injection branch pipe according to an embodiment of the present invention;

[0040] Figure 3 A1-A are several blocks on the A side of the embodiment of the present invention. N Schematic diagram of the structure;

[0041] Explanation of the accompanying reference numerals: 1. Ammonia injection main pipe; 2. Ammonia injection grid; 3. Ammonia injection branch pipe; 4. Compressed air purge branch pipe; 5. Compressed air purge branch pipe valve; 6. Compressed air purge main pipe; 7. Compressed air purge main pipe valve; 8. Ammonia injection main pipe valve. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Reference Figure 1 A coal-fired unit SCR denitration precise ammonia injection anti-blocking system divides the entire denitration flue into a plurality of ammonia injection blocks, each group of ammonia injection blocks includes an ammonia injection mother pipe 1 and a plurality of ammonia injection branch pipes 3, wherein the ammonia injection mother pipe 1 is connected to the plurality of ammonia injection branch pipes 3 through an ammonia injection grid 2, each ammonia injection branch pipe 3 is connected to a compressed air purge branch pipe 4, and then the plurality of compressed air purge branch pipes 4 are connected to the compressed air purge mother pipe 6;

[0044] Furthermore, an ammonia injection main pipe valve 8 is installed in the ammonia injection main pipe 1 , and the ammonia injection main pipe valve 8 is used to adjust the ammonia injection flow rate of the ammonia injection main pipe 1 .

[0045] Furthermore, a flow sensor is provided at the inlet of each ammonia injection branch pipe 3, and the flow sensor can detect the flow of the ammonia injection branch pipe to determine the flow of the ammonia injection amount in the ammonia injection branch pipe.

[0046] Furthermore, a compressed air purge branch pipe valve 5 is installed in each compressed air purge branch pipe 4, and the compressed air purge branch pipe valve 5 is used to adjust the purge flow of the compressed air purge branch pipe 4. It should be noted that the outlet pressure of the compressed air purge branch pipe 4 is 0.6-1.0MPa.

[0047] Furthermore, a compressed air purge main pipe valve 7 is installed on the compressed air purge main pipe 6 , wherein the compressed air purge main pipe valve 7 is used to adjust the purge flow of the compressed air purge main pipe 6 .

[0048] The present invention uses the compressed air of the coal-fired unit as the gas source. At the beginning of the system operation, the manual valves of the compressed air spray branch pipe 3 and the spray main pipe 1 are opened. The flow rate of the ammonia spray branch pipe 3 is detected by the flow sensor, the blockage of the ammonia spray branch pipe 3 is determined, and the signal is fed back to the control center. The control center of the present invention controls the valve opening of the spray branch pipe 3, and the blocked ammonia spray branch pipe is sprayed and swept by compressed air to improve the uniformity of ammonia spray.

[0049] The working principle of the present invention is as follows:

[0050] Taking the first block A1 on the A side as an example, let the i-th ammonia injection branch pipe in A1 be A i , calculate the ammonia injection branch pipe A i The flow rate in the tube is qi , and then calculate the average flow rate Q1 of all ammonia injection branches in block A1:

[0051]

[0052] After calculating q i Deviation value δ from Q1:

[0053] δ=(q i -Q1) / Q1*100 (2)

[0054] Then the deviation value δ is input to the control center, which performs analysis and calculation, and then controls A i The valve opening of the electric regulating valve for compressed air spraying in the ammonia spray branch pipe.

[0055] Specific:

[0056] First, keep the branch pipe valve opening on the purge pipeline corresponding to the ammonia injection branch pipe Ai at 70% opening position, and the main pipe valve of the purge pipeline is in the fully closed position.

[0057] When the precise ammonia injection device is put into operation, and the flow deviation value δ of the ammonia injection branch pipe is greater than 20%, the main pipe valve of the compressed air purge pipeline is opened, and the branch pipe valve on the purge pipeline corresponding to the ammonia injection branch pipe Ai is closed by 5%. The flow deviation value δ is measured every 10 minutes. When the absolute value of the deviation value δ is less than 10%, the branch pipe valve of the compressed air purge pipeline is kept unchanged and its main pipe valve is closed.

[0058] When the precise ammonia injection device is put into operation, and the flow deviation value δ of the ammonia injection branch pipe is less than minus 20%, the main pipe valve of the compressed air purge pipeline is opened, and the valve opening on the purge pipeline corresponding to the ammonia injection branch pipe Ai is increased by 5%, and the flow deviation value δ is measured every 10 minutes. When the deviation value δ is greater than -10%, the branch pipe valve of the compressed air purge pipeline is kept unchanged and its main pipe valve is closed.

[0059] When the absolute value of the flow deviation value δ of the ammonia injection branch pipe is less than 10%, the main pipe valve on the purge pipeline corresponding to the ammonia injection branch pipe Ai is closed.

[0060] Furthermore, when the absolute value of the flow deviation value δ of the ammonia injection branch pipe in the A1 block is less than 10%, the average flow rate Q1 of the ammonia injection branch pipe in the A1 block is compared with the average flow rate Q1 of the ammonia injection branch pipe in all blocks of the denitrification flue. s By comparison, the deviation value X is obtained; the average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue is Q s The calculation formula is:

[0061]

[0062] X=(Q1-Q s ) / Q1*100 (4)

[0063] In the formula, Q i is the average flow rate of the ammonia injection branch pipe in the i-th block.

[0064] C that exports A1 in blocks NOx1 The concentration value and the average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue C NOxi Make a comparison and get the deviation value Y;

[0065] Y=(C NOx1 -C NOxi ) / C NOxi *100 (5).

[0066] When the average flow rate of the ammonia injection branch pipe in the A1 block Q1 is less than the average flow rate of the ammonia injection branch pipe in all blocks Q s value, the deviation value X is less than 20%; and the C of the A1 block outlet NOx1 The concentration value is greater than the average flow rate of the ammonia injection branch pipe in all blocks C NOxi When the deviation value Y is greater than 20%, it is judged that all ammonia spray branch pipes in the A1 block area on the A side are blocked, then open the main pipe valve of the purge pipeline corresponding to the A1 ammonia spray branch pipe, and fully open the branch pipe valve of the purge pipeline at the same time;

[0067] When the deviation value X and the deviation value Y do not meet the above requirements, the valve opening of the ammonia injection branch pipe and the purge branch pipe is maintained unchanged.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coal-fired unit SCR denitrification precise ammonia injection anti-blocking system, characterized in that: The entire denitrification flue is divided into a plurality of ammonia injection blocks, each group of the ammonia injection blocks comprises an ammonia injection main pipe (1) and a plurality of ammonia injection branch pipes (3), wherein the ammonia injection main pipe (1) is connected to the plurality of ammonia injection branch pipes (3) through an ammonia injection grid (2), and the ammonia injection branch pipes (3) are also connected to a purge pipeline; A flow sensor is provided at the inlet of the ammonia injection branch pipe (3); The flow rate of an ammonia injection branch pipe is compared with the average flow rate of all ammonia injection branch pipes in the entire block to obtain a deviation value δ. According to the range of the deviation value, the opening and closing degree of the valve on the corresponding purge pipeline is adjusted.

2. According to claim 1, a coal-fired unit SCR denitrification precise ammonia injection anti-blocking system is characterized by: Let the i-th ammonia injection branch of the first block A1 on the A side be A i , calculate the ammonia injection branch pipe A i The flow rate in the tube is q i ; Then the calculation formula for the average flow rate Q1 of all ammonia injection branches in the block is: Then q i The calculation formula for the deviation value δ from Q1 is: δ=(q i -Q1) / Q1*100 (2).

3. According to claim 2, a coal-fired unit SCR denitrification precise ammonia injection anti-blocking system is characterized by: When the flow deviation value δ of the ammonia injection branch pipe is greater than 20%, the ammonia injection branch pipe A i Reduce the valve opening on the corresponding purge pipeline; When the flow deviation value δ of the ammonia injection branch pipe is less than minus 20%, the ammonia injection branch pipe A i The valve opening on the corresponding purge pipeline increases; When the absolute value of the flow deviation value δ of the ammonia injection branch pipe is less than 10%, the ammonia injection branch pipe A i The valve on the corresponding purge pipeline is closed.

4. According to claim 3, a coal-fired unit SCR denitrification precise ammonia injection anti-blocking system is characterized by: When the absolute value of the flow deviation δ of the ammonia injection branch pipe in the A1 block is less than 10%: The average flow rate of the ammonia injection branch pipe in the A1 block Q1 is compared with the average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue Q s Make a comparison and get the deviation value X; C that exports A1 in blocks NOx1 The concentration value and the average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue C NOxi Make a comparison and get the deviation value Y; According to the range of the deviation value X and the deviation value Y, adjust the opening and closing of the valve on the corresponding purge pipeline.

5. According to claim 4, a coal-fired unit SCR denitrification precise ammonia injection anti-blocking system is characterized by: The average flow rate of the ammonia injection branch pipe in all blocks of the denitrification flue Q s The calculation formula is: In the formula, Q i is the average flow rate of the ammonia injection branch pipe in the i-th block.

6. According to claim 4, a coal-fired unit SCR denitrification precise ammonia injection anti-blocking system is characterized by: The calculation formula of the deviation value X is: X=(Q1-Q s ) / Q1*100 (4)。 7. According to claim 4, a coal-fired unit SCR denitrification precise ammonia injection anti-blocking system is characterized by: The calculation formula of the deviation value Y is: Y=(C NOx1 -C NOxi ) / C NOxi *100 (5)。 8. According to claim 4, a coal-fired unit SCR denitrification precise ammonia injection anti-blocking system is characterized by: When the average flow rate of the ammonia injection branch pipe in the A1 block Q1 is less than the average flow rate of the ammonia injection branch pipe in all blocks Q s Value, when the deviation value X is less than 20%; And A1 block exit C NOx1 The concentration value is greater than the average flow rate of the ammonia injection branch pipe in all blocks C NOxi , when the deviation value Y is greater than 20%, it is judged that all ammonia spray branch pipes in the A1 block area on the A side are blocked, then open the main pipe valve of the purge pipeline corresponding to the A1 ammonia spray branch pipe, and at the same time fully open the branch pipe valve of the purge pipeline; When the deviation value X and the deviation value Y do not meet the above requirements, the valve openings of the ammonia injection branch pipe, the purge branch pipe and the main pipe are maintained unchanged.

9. The SCR denitration precise ammonia injection anti-blocking system for coal-fired units according to claim 1 is characterized by: The purge pipeline comprises a compressed air purge branch pipe (4) and a compressed air purge main pipe (6), wherein the compressed air purge branch pipe (4) is provided with a plurality of groups, which are respectively connected to the corresponding ammonia injection branch pipe (3) through the ammonia injection grid (2), and the other end of the compressed air purge branch pipe (4) is connected to the compressed air purge main pipe (6); A compressed air purge branch pipe valve (5) is installed in each of the compressed air purge branch pipes (4); and a compressed air purge main pipe valve (7) is installed in the compressed air purge main pipe (6).

10. A coal-fired unit SCR denitration precise ammonia injection anti-blocking system according to claim 9, characterized in that: The outlet pressure of the compressed air purge branch pipe (4) is 0.6-1.0 MPa.

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