CN-116025891-B - Air distribution control method for inhibiting coking of burning high-alkali coal four-corner tangential boiler

CN116025891BCN 116025891 BCN116025891 BCN 116025891BCN-116025891-B

Abstract

The invention discloses an air distribution control method for inhibiting coking of a high-alkali coal four-corner tangential boiler for combustion, which comprises the steps of controlling the opening degrees of a secondary air door, an overfire air door and a peripheral air door by taking a condition I to a condition III as a control principle, wherein the differential pressure of the condition I, the secondary air door and a boiler furnace is 0.4 KPa-0.95 KPa, the operating oxygen amount is 3.0% -6.5%, the secondary air accounts for 60% -70%, the overfire air accounts for 25% -35%, the peripheral air accounts for 4% -5%, the opening degrees of multiple layers of secondary air doors sequentially arranged along the boiler furnace from bottom to top form a two-section double-beam-waist air distribution mode, and the opening degrees of the multiple layers of overfire air doors arranged at the top of the boiler furnace are in regular triangle distribution. The air distribution control method can improve the oxygen content of the main combustion area, increase the residence time of coal powder particles in the hearth, reduce the flame center, strengthen the burnout characteristic of coal powder, inhibit the coking of a heating surface and improve the blending combustion proportion of high-alkali coal.

Inventors

CAI CHUANQI
GUO WANGUI
ZHU PAN
YANG ZEXIN
Lv Weizhi
HE XIANG
TAO LI
LI DETANG

Assignees

中电投新疆能源化工集团五彩湾发电有限责任公司
上海发电设备成套设计研究院有限责任公司

Dates

Publication Date: 20260512
Application Date: 20230210

Claims (6)

1. An air distribution control method for inhibiting coking of a high-alkali coal-fired four-corner tangential boiler, wherein a boiler furnace of the four-corner tangential boiler is provided with a plurality of layers of secondary air doors for providing secondary air, a plurality of layers of overfire air doors for providing overfire air and a plurality of layers of perimeter air doors for providing perimeter air, and the secondary air, the overfire air and the perimeter air are all sourced from a secondary air bellow, and the air distribution control method is characterized by comprising the steps of controlling the opening degrees of the plurality of layers of secondary air doors, the plurality of layers of overfire air doors and the plurality of layers of perimeter air doors by taking the following conditions I to III as control principles: The differential pressure of the secondary air bellow and the boiler furnace is 0.4 KPa-0.95 KPa, the operating oxygen amount is 3.0% -6.5%, the secondary air accounts for 60% -70%, the overfire air accounts for 25% -35%, and the peripheral air accounts for 4% -5%; The multi-layer secondary air door sequentially arranged from bottom to top along the boiler furnace is divided into an upper group and a lower group, each group comprises a plurality of layers of secondary air doors, and the opening degree of the plurality of layers of secondary air doors of each group adopts a beam waist type air distribution mode with two high ends and a low middle part to form a two-section double beam waist type air distribution mode; and under the condition III, the opening degree of the multi-layer overfire air door arranged at the top of the boiler furnace is gradually reduced from bottom to top, so that the opening degree of the multi-layer overfire air door is distributed in a regular triangle.
2. The air distribution control method according to claim 1, wherein the boiler furnace is provided with a plurality of layers of coal dust nozzles, the plurality of layers of perimeter air doors are in one-to-one correspondence with the plurality of layers of coal dust nozzles, each layer of coal dust nozzles is connected to a coal mill, and the opening degree of each layer of secondary air doors is specifically regulated and controlled according to the following manner on the basis of meeting the control principles of the conditions I to III: determining the opening base number of the secondary air door; and correcting the opening base according to the coal quantity of the coal mill corresponding to the secondary air door and the coal quantity of the coal mill adjacent to the secondary air door, and determining the opening of the secondary air door.
3. The air distribution control method according to claim 2, wherein the determining the opening base of the secondary air damper includes: acquiring a functional relation between the boiler load and the opening of the secondary air door; and determining the opening base number of the secondary air throttle valve based on the boiler load input value and the functional relation.
4. The air distribution control method according to claim 2, wherein the correcting the opening degree base according to the coal amount of the coal mill corresponding to the secondary air door and the coal amount of the coal mill adjacent thereto includes: Acquiring a first correction function relation between the coal quantity of the coal mill corresponding to the secondary air door and the opening of the secondary air door, and acquiring a second correction function relation between the coal quantity of the coal mill adjacent to the secondary air door and the opening of the secondary air door; And calculating to obtain a first correction value based on the coal quantity input value of the corresponding coal mill and the first correction function relation, calculating to obtain a second correction value based on the coal quantity input value of the adjacent coal mill and the second correction function relation, and correcting the opening base according to the first correction value and the second correction value.
5. The air distribution control method according to any one of claims 2 to 4, wherein on the basis of the control principles satisfying the conditions I to III, the opening degree of the overfire air damper is specifically controlled in the following manner: Acquiring a functional relation between the boiler load and the concentration of NO x at the outlet of the hearth, and determining a target concentration value of NO x based on the boiler load input value and the functional relation; and (3) inputting the NO x concentration deviation set value, the actual measurement value of the concentration of the NO x at the hearth outlet and the target concentration value of the NO x which are input by an operator into a PID controller, and calculating and outputting the opening of the over-fire air door by the PID controller.
6. The air distribution control method according to claim 5, wherein on the basis of the control principles satisfying the conditions I to III, the opening degree of the perimeter air damper is specifically controlled in the following manner: The opening degree of the perimeter air damper is set to be adjusted along with the operation mode of the corresponding coal mill, wherein the opening degree of the perimeter air damper is 4% -6% when the corresponding coal mill is operated, and the opening degree of the perimeter air damper is 18% -22% when the corresponding coal mill is not operated.

Description

Air distribution control method for inhibiting coking of burning high-alkali coal four-corner tangential boiler Technical Field The invention belongs to the technical field of operation of coal-fired power station boilers, and particularly relates to an air distribution control method for inhibiting coking of a high-alkali coal-fired tetragonal tangential boiler. Background The four corner tangential coal-fired boiler is generally designed with primary air, secondary air, overfire air and peripheral air. The secondary air is hot air fed into the hearth through a separate channel of the burner, and is gradually mixed with the primary air after entering the hearth. The secondary air provides oxygen for the combustion of the pulverized coal, can strengthen the disturbance of air flow, promote the backflow of high-temperature flue gas, promote the mixing of combustible materials and oxygen, and provide conditions for complete combustion. The over-fire air is used for reducing the generation of NO x, and the hot air is independently fed into the upper part of the main burner in a staged air supply mode in the hearth so as to further burn out combustible matters in the later stage. The peripheral wind mainly forms an air curtain around the primary wind flow, and the primary wind port is cooled, so that pulverized coal torch is prevented from being stuck to the wall and pulverized coal is prevented from being separated from the flow, a small amount of secondary wind can be timely supplied after the pulverized coal flow catches fire, and the development of the combustion process is facilitated. In actual boiler operation, secondary air, over-fire air and peripheral air are all derived from the large secondary air bellows, parameters such as distribution proportion, flow characteristics and rigidity among the three are mainly regulated by means of the opening degree of an air door, and different distribution characteristics influence combustion working conditions in a hearth. The control scheme of the opening degree of the secondary air damper is that the opening degree of the damper is set to follow the differential pressure between the windbox and the hearth, and the differential pressure setting is changed along with the boiler command (fuel quantity setting). The control scheme for the opening of the overfire air damper is typically open loop control, i.e., the damper opening is set to follow the total air volume change. The control strategy is suitable for a conventional coal-fired boiler, can ensure synchronous change of the opening of the air door and fuel and enhance combustion response, but for the boiler burning high-alkali coal, the main burner area is easily caused to be lack of oxygen, the flame center moves upwards, and then the heating surface is caused to be coked in a large area, so that the safe and stable operation of the unit is greatly influenced. Disclosure of Invention In view of the defects in the prior art, the invention provides an air distribution control method for inhibiting coking of a high-alkali coal fired tetragonal circular boiler, so as to solve the problem of coking of a heating surface of the conventional high-alkali coal fired tetragonal circular boiler. In order to solve the problems, the invention adopts the following technical scheme: An air distribution control method for inhibiting coking of a high-alkali coal-fired four-corner tangential boiler, wherein a boiler furnace of the four-corner tangential boiler is provided with a plurality of layers of secondary air doors for providing secondary air, a plurality of layers of overfire air doors for providing overfire air and a plurality of layers of perimeter air doors for providing perimeter air, and the secondary air, the overfire air and the perimeter air are all sourced from a secondary air bellow, and the air distribution control method comprises the steps of controlling the opening degrees of the plurality of layers of secondary air doors, the plurality of layers of overfire air doors and the plurality of layers of perimeter air doors by taking the following conditions I to III as control principles: The differential pressure of the secondary air bellow and the boiler furnace is 0.4 KPa-0.95 KPa, the operating oxygen amount is 3.0% -6.5%, the secondary air accounts for 60% -70%, the overfire air accounts for 25% -35%, and the peripheral air accounts for 4% -5%; The multi-layer secondary air door sequentially arranged from bottom to top along the boiler furnace is divided into an upper group and a lower group, each group comprises a plurality of layers of secondary air doors, and the opening degree of the plurality of layers of secondary air doors of each group adopts a beam waist type air distribution mode with two high ends and a low middle part to form a two-section double beam waist type air distribution mode; and under the condition III, the opening degree of the multi-layer overfire air door arranged at the top of the