阅读说明：本技术 前后墙对冲锅炉精细化燃烧配风控制系统及方法 (Front-rear wall opposed firing boiler refined combustion air distribution control system and method ) 是由 高林 周俊波 郑清瀚 王嘉寅 惠文涛 王明坤 赵章明 于 2021-09-14 设计创作，主要内容包括：本发明公开了一种前后墙对冲锅炉精细化燃烧配风控制系统及方法,该系统包括核心的控制器及其三类采集输入回路和两类控制输出回路,采集的四类传感器信号,包括煤质在线监测系统输出的在线煤质信号、来自给煤机的给煤量信号、安装在一次风粉管道上的一次风粉在线监测装置输出的一次风粉流量、风速信号、安装在二次风风道上的层二次风流量计输出的空气流量信号,输出两类控制指令,包括每一层燃烧器对应的层二次风箱两侧二次风风道上安装的层二次风箱两侧总风门的开度指令、每一层燃烧器对应的层二次风箱出口控制每个燃烧器二次风量的二次风箱小风门开度。本发明基于当前煤质在线与风粉在线测量技术,实现配风燃烧控制的精细化。(The invention discloses a front-rear wall opposed boiler refined combustion air distribution control system and a method, the system comprises a core controller, three types of acquisition input loops and two types of control output loops, four types of acquired sensor signals comprise an online coal quality signal output by a coal quality online monitoring system, a coal feeding quantity signal from a coal feeder, a primary air-powder flow and air speed signal output by a primary air-powder online monitoring device arranged on a primary air-powder pipeline, an air flow signal output by a layer secondary air flow meter arranged on a secondary air duct, and two types of control instructions are output, the opening instruction of the total air doors on two sides of the secondary air bellow arranged on the secondary air channels on two sides of the secondary air bellow corresponding to each layer of combustor and the opening of the small air doors of the secondary air bellow for controlling the secondary air quantity of each combustor by the outlet of the secondary air bellow corresponding to each layer of combustor are included. The invention realizes the refinement of air distribution combustion control based on the current coal quality on-line and air-powder on-line measurement technology.)

1. The utility model provides a preceding back wall hedging boiler wind control system that becomes more meticulous in burning which characterized in that: the controller (11) comprises a core, four types of acquisition input loops and two types of control output loops; the four-type acquisition input loop comprises a coal quality online monitoring system (13) connected with the input end of a controller (11), a coal feeding quantity signal of a coal feeder (8) connected with the input end of the controller (11), a primary air-powder online monitoring device (9) connected with the input end of the controller (11) and arranged on a primary air-powder pipeline (12), and a layer secondary air flow meter (10) connected with the input end of the controller (11) and arranged on a secondary air duct (4); four types of sensor signals acquired by an input loop are acquired, wherein the four types of sensor signals comprise an online coal quality signal output by a coal quality online monitoring system (13), a coal feeding quantity signal from a coal feeder (8), a primary air powder flow and a wind speed signal output by a primary air powder online monitoring device (9) arranged on a primary air powder pipeline (12), and an air flow signal output by a layer secondary air flow meter (10) arranged on a secondary air duct (4); the two types of control output loops comprise layer secondary air box two-side main air doors (5) arranged on secondary air channels (4) at two sides of a layer secondary air box (6) corresponding to each layer of combustor (3) connected with the output end of the controller (11), and secondary air box small air doors (7) for controlling the secondary air quantity of each combustor at the outlet of the layer secondary air box (6) corresponding to each layer of combustor (3) connected with the output end of the controller (11); the two types of control output circuits output two types of control instructions, including opening instructions of main air doors (5) at two sides of the secondary air bellow, which are arranged on secondary air channels (4) at two sides of the secondary air bellow (6) corresponding to each layer of combustor (3), and opening of small air doors (7) of the secondary air bellow, which are used for controlling the secondary air quantity of each combustor, at an outlet of the secondary air bellow (6) corresponding to each layer of combustor (3).

2. The control method of the front-rear wall opposed firing boiler refined combustion air distribution control system of claim 1, characterized in that: the method comprises the steps of firstly calculating the air quantity required by theoretical combustion of unit coal quantity corresponding to the coal quality of each layer of combustor entering a furnace, then calculating the total secondary air quantity control target of each layer of combustor according to a coal feeding quantity signal output by a coal feeder (8), further controlling the total secondary air quantity of each layer of combustor through opening adjustment of the total air doors (5) on two sides of the secondary air channel (4) of each layer of secondary air channel (6) corresponding to each layer of combustor (3), and finally controlling the opening of the small air door (7) of each secondary air channel corresponding to each combustor according to the primary air powder flow and the air speed signal output by a primary air powder online monitoring device (9), thereby completing the refined air distribution control of the front-wall and rear-wall opposed firing boilers.

3. The control method according to claim 2, characterized in that: the method for calculating the theoretical combustion air quantity required by the unit coal quantity corresponding to the coal quality of each layer of the combustor as fired comprises the following steps: calculating the oxygen demand for theoretical combustion according to the coal element content and the chemical reaction equation output by the coal online monitoring system (13), and further calculating the air quantity; if the coal quality on-line monitoring system (13) does not contain the element content measurement result but only contains the industrial analysis result, different methods are divided according to the volatilization division of the coal quality: for coal with less than 15% of volatile components, neglecting the influence of the air quantity required by the combustion of non-carbon elements and the oxygen content of the coal, namely directly calculating the air quantity required by theoretical combustion by using the carbon content; for coal quality with a volatile matter higher than 20%, multiplying a correction coefficient, which is estimated from an average ratio of an actual operating air amount to an air amount required for calculating theoretical combustion from a carbon content, on the basis of calculating the air amount required for theoretical combustion from the carbon content; for coal quality with 15% to 20% of volatile matter, it is determined manually whether or not correction is necessary according to a method of calculating the amount of deviation between the actual operating air amount and the theoretical combustion air amount from the carbon content, and the amount of deviation is higher than 20% of the volatile matter, that is, the high volatile matter coal quality.

4. The control method according to claim 2, characterized in that: the method for calculating the total secondary air volume control target of each layer of combustor comprises the steps of obtaining the total air volume required by theoretical combustion of each layer of combustor according to the obtained air volume required by theoretical combustion of unit coal volume corresponding to the coal quality of each layer of combustor entering the furnace and multiplying the obtained signal of coal feeding volume output by a coal feeding machine (8), wherein the total air volume required by the theoretical combustion of each layer of combustor needs to be multiplied by 90% first, then the primary air volume used by a coal grinding machine (1) for conveying coal powder is reduced, and then the control target of the secondary air volume corresponding to the combustor is formed.

5. The control method according to claim 2, characterized in that: the control method of the secondary air box small air door corresponding to each combustor comprises the following steps that firstly, a controller (11) controls the opening degree of the total air doors (5) on two sides of a layer secondary air box installed on secondary air channels (4) on two sides of the layer secondary air box (6) corresponding to each layer of combustor (3) according to the total secondary air quantity control target of each layer of combustor, and the total amount of the inflow air quantity on two sides of the layer secondary air box (6) is kept equal to the control target; on the basis, according to the concentration ratio or the flow ratio of pulverized coal in the pulverized coal pipes of each burner output by a primary air-powder online monitoring device (9) arranged on a primary air-powder pipeline (12), the opening degree of a secondary air box small air door (7) of secondary air quantity of each burner at the outlet of a layer of secondary air box (6) corresponding to each layer of burner (3) is controlled, so that the air quantity flowing through the secondary air box small air door (7) of each burner is in direct proportion to the powder quantity.

Technical Field

The invention relates to the technical field of automatic control of power station boiler combustion, in particular to a refined combustion air distribution control system and method for a front-wall and rear-wall opposed-flushing boiler.

Background

The boiler is one of core hosts of a modern thermal power station, but for a long time, the control of air distribution combustion is relatively extensive, the control and optimization of macroscopic parameters such as smoke and oxygen contents are mainly used, the local refined automatic control of air distribution combustion is difficult to realize, and great challenges are brought to pollutant generation control, high-temperature corrosion prevention, energy conservation and high-efficiency operation and the like.

The front-back wall opposed firing boiler is one of the most common burner arrangement forms of the modern high-power coal-fired boiler. A plurality of rows (three rows are common in a high-power unit) of burners are respectively arranged on the front wall and the rear wall of a boiler furnace, and the number of the burners in each row can be linearly expanded according to the increase of the boiler capacity, so that the design of a boiler with larger capacity is relatively simple.

The air distribution control of the front-wall and rear-wall opposed firing boilers generally controls the primary air quantity carrying pulverized coal according to the fuel quantity corresponding to each layer of burner; simultaneously controlling the opening degree of an air door at the inlet of each layer of secondary air box, thereby controlling the total secondary air quantity of the layer of burners; there is generally no difference in air distribution strategy between different layer burners and between the same layer burners, or the air distribution strategy is optimized through expert experiments and then fixed. Because the fuel of each layer of combustor comes from different coal mills and has natural difference of coal quality, the theoretical air quantity required by the fuel combusted by the different layer of combustor has certain deviation, and the fuel quantity distribution among pipelines has non-uniform requirement on the combustion air quantity due to the difference of pipeline arrangement and the like of the same layer of combustor. The deviation changes to different degrees along with the migration of coal quality, load working conditions and time, which is one of the common problems existing in the combustion control of the front-wall and rear-wall opposed boiler.

Disclosure of Invention

In view of the above problems, the invention provides a front-rear wall opposed firing boiler refined combustion air distribution control system and method, which realize the refinement of air distribution combustion control based on the current coal quality online and air-powder online measurement technology.

In order to achieve the purpose, the invention adopts the following technical scheme:

a front-rear wall opposed firing boiler refined combustion air distribution control system comprises a core controller 11, four types of acquisition input loops and two types of control output loops; the four-type acquisition input loop comprises a coal quality online monitoring system 13 connected with the input end of a controller 11, a coal feeding quantity signal of a coal feeder 8 connected with the input end of the controller 11, a primary air-powder online monitoring device 9 connected with the input end of the controller 11 and arranged on a primary air-powder pipeline 12, and a layer secondary air flow meter 10 connected with the input end of the controller 11 and arranged on a secondary air duct 4; four types of sensor signals collected by the input loop are collected, including an online coal quality signal output by a coal quality online monitoring system 13, a coal feeding quantity signal from a coal feeder 8, a primary air powder flow and air speed signal output by a primary air powder online monitoring device 9 arranged on a primary air powder pipeline 12, and an air flow signal output by a layer secondary air flow meter 10 arranged on a secondary air duct 4; the two types of control output loops comprise layer secondary air box two-side main air doors 5 arranged on secondary air channels 4 at two sides of a layer secondary air box 6 corresponding to each layer of combustor 3 connected with the output end of the controller 11, and secondary air box small air doors 7 for controlling the secondary air quantity of each combustor at the outlet of the layer secondary air box 6 corresponding to each layer of combustor 3 connected with the output end of the controller 11; the two types of control output circuits output two types of control instructions, including an opening instruction of a main air door 5 at two sides of the secondary air bellow arranged on a secondary air duct 4 at two sides of a secondary air bellow 6 corresponding to each layer of combustor 3, and an opening of a small air door 7 of the secondary air volume of each combustor controlled by an outlet of the secondary air bellow 6 corresponding to each layer of combustor 3.

The control method of the refined combustion air distribution control system of the front-rear wall hedging boiler comprises the steps of firstly calculating the air quantity required by theoretical combustion of unit coal quantity corresponding to the coal quality of each layer of combustor, then calculating the total secondary air quantity control target of each layer of combustor according to a coal supply quantity signal output by a coal supply machine 8, further controlling the total secondary air quantity of each layer of combustor through the opening degree adjustment of the total air doors 5 on two sides of the layer secondary air box arranged on the secondary air channels 4 on two sides of the layer secondary air box 6 corresponding to each layer of combustor 3, and finally controlling the opening degree of the small air door 7 of the secondary air box corresponding to each combustor according to the primary air powder flow and the air speed signal output by a primary air powder online monitoring device 9, so that the refined air distribution control of the front-rear wall hedging boiler is completed.

The method for calculating the theoretical combustion air quantity required by the unit coal quantity corresponding to the coal quality of each layer of the combustor as fired comprises the following steps: calculating the oxygen demand for theoretical combustion according to the content of coal elements output by the coal quality online monitoring system 13 and a chemical reaction equation, and further calculating the air quantity; if the coal quality on-line monitoring system 13 does not include the result of measuring the element content but only includes the result of industrial analysis, different methods are divided according to the volatility of the coal quality: for coal with less than 15% of volatile components, neglecting the influence of the air quantity required by the combustion of non-carbon elements and the oxygen content of the coal, namely directly calculating the air quantity required by theoretical combustion by using the carbon content; for coal quality with a volatile matter higher than 20%, multiplying a correction coefficient, which is estimated from an average ratio of an actual operating air amount to an air amount required for theoretical combustion calculated from a carbon content, on the basis of calculating the air amount required for theoretical combustion from the carbon content; for coal quality with 15% to 20% of volatile matter, it is determined manually whether or not correction is necessary according to a method of calculating the amount of deviation between the actual operating air amount and the theoretical combustion air amount from the carbon content, and the amount of deviation is higher than 20% of the volatile matter, that is, the high volatile matter coal quality.

The method for calculating the total secondary air volume control target of each layer of combustor comprises the steps of obtaining the total air volume required by theoretical combustion of each layer of combustor according to the obtained air volume required by theoretical combustion of unit coal volume corresponding to the coal quality of each layer of combustor entering the furnace and multiplying the obtained signal of coal feeding volume output by a coal feeder 8, wherein the total air volume required by the theoretical combustion of each layer of combustor needs to be multiplied by 90% first, then the primary air volume used by a coal mill 1 for conveying pulverized coal is reduced, and then the control target of the secondary air volume corresponding to the combustor is formed.

The control method of the secondary air box small air door corresponding to each burner comprises the following steps that firstly, the controller 11 controls the opening degree of the total air doors 5 on two sides of the secondary air box arranged on the secondary air channels 4 on two sides of the secondary air box 6 corresponding to each layer of burner 3 according to the total secondary air quantity control target of each layer of burner, and the total inflow air quantity on two sides of the secondary air box 6 is kept equal to the control target; on the basis, according to the pulverized coal concentration ratio or the pulverized coal flow ratio in each burner pulverized coal pipe output by the primary air-powder online monitoring device 9 arranged on the primary air-powder pipeline 12, the opening degree of the secondary air box small air door 7 of each burner secondary air quantity at the outlet of the layer secondary air box 6 corresponding to each layer of burner 3 is controlled, so that the air quantity flowing through the secondary air box small air door 7 of each burner is in direct proportion to the powder quantity.

The system and the method have the following characteristics that the system and the method can be obviously distinguished from other similar technologies.

(1) The system simultaneously comprises a primary air-powder online monitoring device and a coal quality online monitoring system. Because the air quantity required by coal combustion is related to the coal quality and the coal quantity, the refined air distribution of the coal combustion can be really realized only by simultaneously comprising the two online measuring devices;

(2) the conventional combustion air distribution technology cannot distinguish the difference of the air quantity required by each layer of combustor, so the air distribution optimization premise is to assume that the coal quality burnt by all the combustors is similar, which is far away from the actual situation of most power station boilers in China. This inevitably causes the lack of oxygen in the combustor requiring a large amount of air, resulting in increased incomplete combustion loss and poor economical efficiency of operation; the combustor with a small amount of air needs to be over-oxidized, so that the amount of NOx produced is increased, and the environmental performance is poor.

(3) According to the conventional combustion air distribution technology, small air doors corresponding to a plurality of burners on each layer lack the basis of optimal control, an opening difference is often fixed only according to the influence of side walls and middle burners on water-cooled wall corrosion or ash deposition coking, and combustion air distribution cannot be carried out according to the uneven distribution of actual powder tubes.

Drawings

FIG. 1 is a schematic view of a refined combustion air distribution control system of a front-wall and rear-wall opposed firing boiler according to the present invention.

In the figure: 1-a coal mill; 2-a boiler; 3-a burner; 4-secondary air duct; 5-main air doors on two sides of the secondary air box; 6-layer secondary air box; 7-secondary air box small air door; 8-coal feeder; 9-primary air powder on-line monitoring device; 10-layer secondary air flow meter; 11-controller; 12-primary air powder duct; 13-coal quality on-line monitoring system.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the utility coal-fired boiler generally feeds the coal into a coal mill 1 through a coal feeder 8, grinds the coal into a coal powder of sufficient fineness in the coal mill 1, and carries the coal powder to a corresponding burner 3 through a primary air-powder pipeline 12 by using air, and the coal powder enters a boiler 2 to be combusted and released heat, thereby providing energy for a power generation system. The other air is sent into a layer of secondary air box 6 corresponding to each layer of combustor 3 through two secondary air channels 4 and a main air door 5 on two sides of the layer of secondary air box, and then the air flow entering each combustor is controlled through a secondary air box small air door 7 corresponding to each combustor 3, and the air flow is called secondary air. The primary air is used for carrying pulverized coal to enter the boiler 2, and the secondary air is used for supplementing air required by fuel combustion, so that the high efficiency, environmental protection and stability of combustion are finally guaranteed.

The invention relates to a refined combustion air distribution control system of a front-back wall opposed firing boiler, which comprises a core controller 11, four types of acquisition input loops and two types of control output loops. The four-type acquisition input loop comprises a coal quality online monitoring system 13 connected with the input end of a controller 11, a coal feeding quantity signal of a coal feeder 8 connected with the input end of the controller 11, a primary air and powder online monitoring device 9 connected with the input end of the controller 11 and arranged on a primary air and powder pipeline 12, and a layer secondary air flow meter 10 connected with the input end of the controller 11 and arranged on a secondary air duct 4; four types of sensor signals collected by the input loop are collected, including an on-line coal quality signal output by a coal quality on-line monitoring system 13, a coal feeding quantity signal from a coal feeder 8, a primary air and powder flow, wind speed and concentration signal output by a primary air and powder on-line monitoring device 9 arranged on a primary air and powder pipeline 12, and an air flow signal output by a layer secondary air flow meter 10 arranged on a secondary air duct 4. The two types of control output loops comprise layer secondary air box two-side main air doors 5 arranged on secondary air channels 4 at two sides of a layer secondary air box 6 corresponding to each layer of combustor 3 connected with the output end of the controller 11, and secondary air box small air doors 7 for controlling the secondary air quantity of each combustor at the outlet of the layer secondary air box 6 corresponding to each layer of combustor 3 connected with the output end of the controller 11; the two types of control output loops output two types of control instructions, including an opening instruction of a main air door 5 at two sides of the secondary air bellow installed on the secondary air channels 4 at two sides of the secondary air bellow 6 corresponding to each layer of combustor 3, and an opening of a small air door 7 of the secondary air bellow, which controls the secondary air quantity of each combustor, at an outlet of the secondary air bellow 6 corresponding to each layer of combustor 3.

The invention relates to a refined combustion air distribution control method for a front-wall and rear-wall opposed boiler, which comprises the steps of firstly calculating the air quantity required by theoretical combustion of unit coal quantity corresponding to the coal quality of each layer of combustor, then calculating the total secondary air quantity control target of each layer of combustor according to a coal feeding quantity signal output by a coal feeder 8, further regulating the opening degree of total air doors 5 on two sides of a layer of secondary air box arranged on secondary air channels 4 on two sides of a layer of secondary air box 6 corresponding to each layer of combustor 3, controlling the total secondary air quantity of each layer of combustor, and finally controlling the opening degree of a small air door 7 of the secondary air box corresponding to each combustor according to a primary air powder flow, air speed and concentration signal output by a primary air powder online monitoring device 9, thereby completing the refined air distribution control of the front-wall and rear-wall opposed boiler.

The method for calculating the air quantity required by theoretical combustion of unit coal quantity corresponding to the coal quality of each layer of combustor entering the furnace can calculate the oxygen quantity required by theoretical combustion according to the coal element content output by the coal quality on-line monitoring system 13 and a standard chemical reaction equation, and further calculate the air quantity. If the coal quality on-line monitoring system 13 does not include the measurement result of the element content but only includes the calorific value, the carbon content, the ash content, the volatile matter, the sulfur content and the moisture content of the industrial analysis result, different methods are divided according to the volatile matter of the coal quality. For the coal quality with the volatile component less than 15%, the influences of the air quantity required by the combustion of non-carbon elements and the oxygen content of the coal quality can be considered to be ignored, namely the air quantity required by theoretical combustion is calculated by directly utilizing the carbon content; for coal quality with volatile content higher than 20%, a correction coefficient is added on the basis of calculating the air amount required for theoretical combustion according to the carbon content. The correction coefficient may be estimated from an average ratio of the actual operating air amount to the air amount required for calculating the theoretical combustion from the carbon content. For coal with 15% to 20% of volatile components, it can be determined manually whether or not to correct the coal with high volatile components, i.e. the volatile components are higher than 20%, according to the deviation between the actual operating air quantity and the theoretical combustion air quantity calculated according to the carbon content.

The method for calculating the total secondary air volume control target of each layer of combustor comprises the steps of obtaining the total air volume required by theoretical combustion of each layer of combustor according to the obtained air volume required by theoretical combustion of unit coal volume corresponding to the coal quality of each layer of combustor entering the furnace and multiplying the obtained signal of coal feeding volume output by a coal feeder 8, wherein the total air volume required by the theoretical combustion of each layer of combustor needs to be multiplied by 90% first, then the primary air volume used by a coal mill 1 for conveying pulverized coal is reduced, and then the control target of the secondary air volume corresponding to the combustor is formed.

The control method of the secondary air box small air door corresponding to each burner comprises the steps that firstly, the controller 11 controls the opening degree of the total air doors 5 on two sides of the secondary air box arranged on the secondary air channels 4 on two sides of the secondary air box 6 corresponding to each layer of the burner 3 according to the total secondary air quantity control target of each layer of the burner, and the total inflow air quantity on two sides of the secondary air box 6 is kept equal to the control target. On the basis, according to the concentration ratio (or the flow ratio) of pulverized coal in the pulverized coal pipes of each burner output by the primary air-powder online monitoring device 9 arranged on the primary air-powder pipeline 12, the opening degree of the secondary air box small air door 7 of the secondary air quantity of each burner at the outlet of the layer secondary air box 6 corresponding to each layer of burner 3 is controlled, so that the air quantity flowing through the secondary air box small air door 7 of each burner is in direct proportion to the powder quantity.