CN-121557508-B - Air-powder balanced distribution method and device for coal-fired unit pulverizing system

Abstract

A method for uniformly distributing the wind powder of pulverizing system of coal-fired unit includes such steps as connecting M wind powder pipelines to outlet of coal mill, dividing each pipeline into n sub-pipelines, regulating the wind resistances of sub-pipelines to become approximate equal, merging the direct-connection burners at the tail ends of sub-pipelines, setting on-line primary wind quantity detector and wind quantity regulator, receiving the detection signals by wind quantity controller, and controlling regulator to make the wind quantity of merging pipelines equal. The air and powder flows are recombined through the splitting-merging pipeline, and the self-adaptive balanced distribution of the pulverized coal is synchronously realized only by controlling the final air quantity balance without detecting the concentration of the pulverized coal in real time. The invention has the advantages of strong load/coal disturbance resistance, high response speed, no spoiler, small windage loss, simple structure and easy reconstruction and implementation. The invention is suitable for the flexible peak regulation scene of the coal-fired unit of the direct-fired pulverizing system.

Inventors

• ZHANG TING
• NIU YUGUANG
• DU MING
• DANG LU
• Han Peida
• HAN XIANGYU
• WU ZEYU
• WANG ZEZHONG
• WANG YIFEI

Assignees

• 华北电力大学

Dates

Publication Date

20260508

Application Date

20250812

Claims (7)

1. 1. The wind-powder balanced distribution method for the coal-fired unit pulverizing system is characterized by comprising the following steps of: step 1, acquiring the number M of air powder pipelines at the outlet of a coal mill and the number N of corresponding burners, wherein the numbers of the air powder pipelines at the outlet of the coal mill are M 1 ,m 2 ,…m m respectively, and the subscript m=M; Step 2, each wind powder pipeline at the outlet of the coal mill is divided into N pipelines with the number of M x n 1 ,m x n 2 ,…m x n n , wherein x is more than or equal to 1 and less than or equal to M, the subscript N is less than or equal to N, M groups of pipelines are generated, and the numbers of the pipelines in each group are as follows: Step 3, merging the tail ends of the pipelines m 1 n 1 ,m 2 n 1 ,…m m n 1 in the N 1 columns into 1 pipeline N 1 ,n 2 column and merging the tail ends of the pipelines m 1 n 2 ,m 2 n 2 ,…m m n 2 into 1 pipeline N 2 until the tail ends of the pipelines m 1 n n ,m 2 n n ,…m m n n in the N n columns are merged into 1 pipeline N n ,N 1 , N 2 ,…N n , wherein the tail ends of the pipelines are respectively connected with a burner; Step 4:m, the pipelines of each group are adjusted according to the pipeline structure of the on-site pulverizing system, and the wind resistance of each pipeline in each group is ensured to be equal by adjusting the path and the length of each pipeline in each group; Step 5, installing a primary air quantity on-line detection device and an air quantity adjustment device on the merging pipeline N 1 , N 2 ,…N n , and connecting an air quantity control device; And 6, when the device runs, the primary air quantity Q N1 ,Q N2 ,…Q Nn of each pipeline is obtained through the air quantity on-line detection device and is sent to the air quantity control device, the air quantity control device calculates an air quantity adjusting signal according to Q N1 ,Q N2 ,…Q Nn and sends the air quantity adjusting signal to the air quantity adjusting device, and the air quantity adjusting device adjusts the air quantity of each pipeline to ensure that the primary air quantity in the N 1 , N 2 ,…N n pipeline is equal.
2. 2. The method of claim 1, wherein the wind resistance balancing is performed by designing an isometric bent pipe path in step 4.
3. 3. The method of claim 1, wherein when the outlet of the coal mill has only 1 pipeline, the outlet of the coal mill is divided into m pipelines uniformly, and then the steps 2-6 are performed.
4. 4. The method of claim 1, wherein when the pipe diameter of the outlet pipeline is too large, the outlet pipeline is split into k secondary pipelines, then divided into N sub-pipelines, and N 1 -N n is generated through multistage combination.
5. 5. The method of claim 1, wherein the air volume control device outputs the adjustment signal with a minimum variance of Q N1 -Q Nn as a target by using a PID controller.
6. 6. The method according to claim 1, wherein the primary air volume online detection device is any one of a Pitot tube flowmeter, a uniform velocity tube flowmeter, an orifice plate flowmeter or a venturi tube flowmeter.
7. 7. The method of claim 1, wherein the air volume adjusting device is any one of an adjustable shrinkage cavity, a valve or a baffle plate.

Description

Air-powder balanced distribution method and device for coal-fired unit pulverizing system Technical Field The invention discloses a method and a device for uniformly distributing air and powder in a coal-fired unit pulverizing system, and particularly relates to a method and a device for uniformly distributing primary air and powder in a coal-fired unit pulverizing system. Background For a coal-fired generator set adopting a direct-fired pulverizing system, the same coal mill generally provides primary air and coal dust for a plurality of burners, and when the set participates in flexible peak shaving, the air-powder distribution balance of the pulverizing system is very critical to the influence of the flame combustion stability of a hearth under low load. The temperature of a hearth is rapidly reduced under low load, the combustion speed of coal dust is reduced, the primary air and coal dust of a coal pulverizing system are unevenly distributed, so that the combustion states of all burners are obviously different, the temperature distribution of main combustion areas of all burners is uneven, the combustion supporting effect of the main combustion areas and adjacent burners is influenced, and the phenomena of unstable combustion, partial combustion of the hearth, increase of NOx concentration and the like are generated, so that the method is an important influencing factor for limiting the peak regulation depth of a unit. The output of the coal mill is reduced during the peak-shaving operation of the unit, the coal feeding rate of part of the coal mill is far lower than the rated output, the leveling mechanism is difficult to ensure the balance of the primary air quantity and the coal feeding quantity of each burner under low load under rated load, the randomness exists in the coal quality change such as the uneven granularity, the water content or the viscosity change of the coal powder in the long-time operation process, and the air-powder distribution balance of the coal powder making system can be influenced by the pipeline resistance change caused by the abrasion of the coal powder pipeline elbow and shrinkage cavity. The current powder making system wind-powder balance adjusting mode mainly comprises: 1) The method only can meet the requirement of air-powder balance of each pipeline under the condition that the output of the coal mill is rated load by adjusting the primary air quantity of the powder making system through adjustable shrinkage holes arranged on each primary air-powder pipeline, when the output of the coal mill is far lower than a design value, an air-powder mixing mechanism in the coal mill fails, and the concentration of the coal powder in each pipeline is different, and at the moment, the adjusting function of the air-powder balance cannot be achieved by controlling the primary air quantity only through the adjustable shrinkage holes; 2) The static separator at the upper part of the coal mill achieves the aim of rapidly separating coarse-particle coal powder by increasing rotational flow, has a certain balanced regulation effect when the output of the coal mill is higher and the flow speed of wind powder in the coal mill is faster, but when the output of the coal mill is far lower than rated load, the turbulence control direction in the static separator is almost perpendicular to the outlet direction of the coal mill, so that the wind powder concentration of each wind powder pipeline at the outlet of the coal mill is difficult to influence. The dynamic separator has the main function of further regulating the fineness of the pulverized coal by utilizing the centrifugal force of the pulverized coal with different particle diameters, and has a certain uniform mixing effect on primary air at the outlet of the coal mill and the pulverized coal to a certain extent; 3) The air-powder balance distributor is arranged at the outlet of the coal mill, such as a compact coal powder distributor designed by the company Gu Bo of the Western An thermal institute, and the like, the coal powder in each primary air pipeline is redistributed in a mode of changing the flow track of the coal powder by a spoiler in the distributor, meanwhile, the wind resistance of a coal pulverizing system is increased, when the output of the coal mill is changed, because of complex coupling effect of primary air quantity and coal powder concentration, an on-line coal powder concentration detection device is required to be arranged on each primary air pipeline, and an air quantity regulating valve and a coal powder concentration regulating valve on each air powder pipeline are repeatedly regulated, so that the air-powder balance regulation can be realized, the on-site requirement of frequently changing the output of the coal mill is difficult to adapt, and the running, installation and maintenance costs of the on-line coal powder concentration detection device in the primary air pipeline are increased, so that the popula