CN-122015115-A - Coal-fired unit powder supply control system and method based on small powder bin

CN122015115ACN 122015115 ACN122015115 ACN 122015115ACN-122015115-A

Abstract

The invention belongs to the technical field of coal-fired unit pulverizing and pulverized coal conveying systems, and particularly relates to a coal-fired unit powder supply control system and method based on a small powder bin. According to the invention, through setting a plurality of powder supply modes of powder taking through the powder pipe, powder taking through the grinding outlet and combined switching of the powder taking through the powder pipe and the powder taking through the grinding outlet, and providing the matched operation control method of powder taking amount adjustment, branch equalization, material level interlocking, backflow prevention, blockage removal and on-line switching, the intelligent and controllable on-line powder supply switching, powder blockage disposal and backflow protection are realized, and the safety, reliability and engineering applicability of the coal-fired unit powder supply are improved.

Inventors

XIANG JUN
JIANG LONG
WANG YI
SU SHENG
HU SONG
CHEN DEZHI
LI JUNMENG
YANG YIQING
CHEN LEI
LIN BOWEN
XU JUN
DENG WEI
XU KAI

Assignees

华中科技大学

Dates

Publication Date: 20260512
Application Date: 20260204

Claims (10)

1. The coal-fired unit powder supply control system based on the small powder bin is characterized by comprising a coal mill, the small powder bin, a controller, a powder pipe powder taking module, a coal mill outlet powder taking module, a combination switching module and a return powder supply and mixed access module; The controller is a DCS or auxiliary control controller and is used for executing mode management, closed loop adjustment, interlocking protection, blocking removal and on-line switching logic; the powder tube powder taking module comprises a powder tube powder taking interface, a powder tube powder taking branch, a branch isolation valve, a branch regulating valve, a branch differential pressure measuring point, a branch check valve, a branch powder taking main pipe, a branch flow equalizing structure, a purging interface and a small powder bin powder inlet connecting section; The coal mill outlet powder taking module comprises a public powder taking interface, a public powder taking branch, a public powder taking isolating valve, a public powder taking regulating valve, a public powder taking differential pressure measuring point, a public powder taking check valve, a public powder taking flow equalizing structure and a public powder taking main pipe; the combined switching module comprises a switching valve group, a switching monitoring differential pressure measuring point and a common powder collecting main pipe and a small powder bin powder inlet connecting section; The return powder supply and hybrid access module comprises a metering powder supply device, a return pipeline, a return isolation valve, a regulating valve, a check valve, a return differential pressure measuring point, a hybrid access point, a hybrid section flow equalizing structure and a dual backflow preventing structure.
2. The powder supply control system according to claim 1, wherein the powder pipe powder taking interface is arranged in a powder pipe horizontal stabilizing section, a lining abrasion-resistant structure is arranged, the powder taking direction is consistent with a main flow, the branch powder taking main pipe is used for collecting powder pipe powder taking branch coal powder, an abrasion-resistant lining is arranged on the inner wall of the branch powder taking main pipe, the branch current equalizing structure is arranged in a branch powder taking main pipe collecting section and used for equalizing the entering speed field of each branch, the purging interface is arranged between the branch isolation valve and the branch regulating valve and is connected with a compressed air or steam source and provided with a purging valve and a check structure, and the small powder bin powder inlet connecting section comprises a quick-closing isolation valve, the check structure and a bin front differential pressure measuring point.
3. The powder supply control system according to claim 2, wherein the common powder taking interface is arranged in a pressure stable section between an outlet of the coal mill and the powder pipe distributor, the common powder taking and flow equalizing structure is arranged at the common powder taking interface and used for improving air powder distribution uniformity, and the common powder taking main pipe is used for receiving common powder taking branch coal powder and accessing the powder inlet of the small powder bin.
4. The powder supply control system according to claim 3, wherein the switching valve group is respectively arranged at the powder taking interface of the powder pipe and the common powder taking interface, and comprises a switching isolation valve and a regulating valve, the switching monitoring differential pressure measuring points are arranged before and after the switching valve group and used for monitoring the stability of the switching process, and the common powder taking main pipe and the powder inlet connecting section of the small powder bin are used as a converging and conveying channel of two paths of powder taking corresponding to powder taking of the powder pipe and powder taking of the outlet of the coal mill.
5. The powder supply control system according to claim 4, wherein the metering powder supply device is arranged at the downstream of the small powder bin and used for accurately controlling the powder discharge amount, the mixing access point is positioned at a mixing section before a primary air main pipe enters a powder pipe distributor, the return pipeline is connected with an outlet of the metering powder supply device to the mixing access point, the mixing section flow equalizing structure is used for promoting the return pulverized coal and the primary air to be fully and uniformly mixed, and the dual backflow preventing structure comprises a return pipeline check valve and a small powder bin side check device and is used for preventing the primary air or the pulverized coal from flowing backwards.
6. A coal-fired unit powder supply control method based on a small powder bin, which is implemented based on the powder supply control system according to claim 5, and is characterized by comprising the following steps: S1, system initialization and state monitoring; Collecting and processing the following input signals in real time, namely the material level of a small powder bin, the differential pressure of a common powder taking main pipe, the differential pressure of each powder taking branch pipe, the running state of a coal mill, the fluctuation of the pressure of a mill outlet, the differential pressure of a powder pipe, the state of a purge valve, the opening degree of all valves, the state feedback of all valves, the state of a check valve and the differential pressure of a return passage, wherein the system initially enters a shutdown isolation state or a standby preparation state; s2, judging and selecting an operation mode; According to the current working condition and the equipment state, the controller selects one of three modes of powder taking from the powder pipe, powder taking from the grinding outlet and combined switching to enter; step S3, executing powder taking amount adjustment and material level closed-loop control; If the small powder bin material level is lower than the lower limit H low , increasing the opening of the corresponding powder taking regulating valve to improve the powder taking capacity until the small powder bin material level is higher than H low ; If the small powder bin material level is higher than the upper limit H high , reducing the opening of the regulating valve until the small powder bin material level is closed to stop powder taking or until the small powder bin material level is lower than H high ; If the material level is in the target interval [ H low ,H high ], maintaining the current valve position, and finely adjusting the valve position according to the differential pressure of the common powder taking main pipe to ensure that the valve position is stabilized at a set value DP set ; all the opening changes of the regulating valves are constrained by limiting (u min ≤u≤u max ) and slope limit (du/dt less than or equal to Ru); s4, performing balance control during multi-branch powder taking; When the powder tube is used for taking powder or the multi-branch is started: The differential pressure of each branch is used as feedback, and each branch regulating valve is independently finely adjusted, wherein the differential pressure is turned off when the differential pressure is higher, and turned on when the differential pressure is lower, so that the differential pressure is kept in a set range; the total powder taking amount is uniformly maintained by a common powder taking main pipe or main control logic, and the branch circuit is only responsible for distributing proportion; if the valve position of a certain branch valve reaches the upper limit and still cannot reach the standard, marking the valve position as 'insufficient capacity', and reducing the distribution weight; If the differential pressure of a certain branch is abnormally increased, marking the differential pressure as 'suspected blockage', and switching to a blockage removal treatment process; step S5, monitoring the reflux risk in real time and executing interlocking protection; S6, diagnosing the blocking powder and starting a blocking clearing strategy; s7, performing on-line switching, and switching between a powder taking mode of a powder pipe and a powder taking mode of a grinding outlet; s8, performing exception handling and system recovery; and after the fault elimination, manual confirmation or automatic reset conditions are met, returning to a standby state, and re-entering a normal control cycle.
7. The method according to claim 6, wherein in the step S2, If the conditions are met simultaneously, the coal mill is stable, the differential pressure of the powder pipe is normal, the powder taking direction is correct, the material level is lower than the target value, the selected branch valve and the measuring point are normal, and the powder pipe powder taking mode is entered; if the conditions are met simultaneously, the coal mill is stable, the differential pressure of the mill outlet section is normal, the common powder taking direction is correct, the material level is lower than the target value, and the common powder taking passage is normal, the mill outlet powder taking mode is entered; If both paths are available and a switching instruction is received and the pressure fluctuation is within the allowable range, a combined switching mode is entered.
8. The powder supply control method according to claim 7, wherein in the step S5, when any one of the following fault conditions occurs, namely, abnormal powder taking differential pressure direction, bin mouth back pressure, check valve fault, back flow path differential pressure reversal, the back flow prevention interlock is triggered immediately: (1) Closing the fault branch regulating valve; (2) Closing the fault branch isolation valve; (3) Closing all the powder collecting main pipe quick closing isolation valves; (4) Sending out an alarm and recording an event; And simultaneously executing powder taking and returning interlocking, namely prohibiting parallel operation of the powder taking and returning interlocking and stopping powder taking according to the sequence of stopping and returning before stopping and taking if the bin pressure or the returning differential pressure or the non-return state is out of limit.
9. The powder supply control method according to claim 8, wherein in the step S6, when the powder blocking criterion is satisfied, the bypass differential pressure is continuously exceeded, the material level is not increased, and the valve position is not matched with the response, the block clearing sequence is executed: S6.1, limiting the powder taking valve position to a safe position; s6.2, opening a branch purging valve and executing pulse purging; S6.3, periodically disturbing the regulating valve to break powder accumulation; S6.4, recovering the original valve position after the blockage is cleared, and observing differential pressure fall and material level rise; S6.5, if the differential pressure is still high and the material level is not recovered, the branch is closed and is switched to the standby branch, and if the standby branch is not available, the grinding outlet powder taking mode is switched to and the abnormal alarm state is entered.
10. The method according to claim 9, wherein in the step S7, the mode conversion precondition is that two paths corresponding to the powder taking of the powder pipe and the powder taking of the outlet of the coal mill are normal, the pressure fluctuation is in an allowable range, the material level is safe, and the valve feedback is effective; The switching flow is as follows: s7.1, opening a new passage isolation valve, and slowly opening the regulating valve to a pre-opening position; s7.2, increasing the powder taking capacity of the new passage according to the slope; s7.3, synchronously reducing the powder taking capacity of the old passage according to the slope, and keeping the total powder taking quantity continuous; s7.4, after the old passage is completely closed, closing an isolation valve of the old passage, and enabling the new passage to enter stable operation; s7.5, recording key parameters of the whole switching process; If any monitoring quantity of two channel states, pressure fluctuation, material level and valve feedback in the switching process exceeds the limit, immediately stopping the switching, returning to the valve position combination before switching, entering an abnormal returning state and giving an alarm.

Description

Coal-fired unit powder supply control system and method based on small powder bin Technical Field The invention belongs to the technical field of coal-fired unit pulverizing and pulverized coal conveying systems, and particularly relates to a coal-fired unit powder supply control system and method based on a small powder bin. Background Under the background that the deep peak regulation and the flexibility operation demands of the thermal power generating unit are increasingly enhanced, the problems of response lag, low load stability and the like of the traditional direct-fired pulverizing system are difficult to meet the requirement of rapid load change. In order to improve the dynamic regulation capability of the fuel supply system, the industry generally explores to realize decoupling of the pulverizing and combustion process by adding a small powder bin as a buffer link. Chinese patent CN121338910a discloses a high-flexibility pulverizing system based on adding small powder bin and its control method, setting small powder bin system as middle buffer link, setting split pipeline at the downstream of primary air-powder mixing pipe, using the open-close combination of direct-blowing valve and in-bin valve to implement three modes of direct-blowing powder supply, medium-storage powder supply or double-source powder supply, decoupling pulverizing process of coal mill from boiler powder demand, using quick-speed regulation capability of coal feeder to compensate response lag characteristic of coal mill system, so as to raise response speed of whole fuel supply system to boiler load change. Meanwhile, the scheme introduces a exhaust gas recirculation system, maintains the wind speed in the mill by adjusting the recirculation air quantity, and improves the low-load operation stability. However, this prior art solution still has the following three disadvantages: (1) The on-line powder supply switching lacks general logic, namely, although the switching of a double-source powder supply mode is supported, a valve position operation sequence, a rate control and disturbance suppression strategy in the switching process are undefined, and powder taking interruption or abrupt change of the pressure of a grinding outlet/powder pipe is easy to cause; (2) The system is not provided with a powder blocking diagnosis mechanism and an active blocking clearing means, and once a powder taking pipeline is blocked, the system can be stopped for treatment only to influence continuous operation; (3) The coal dust backflow risk is high, and the small powder bin can form reverse pressure difference when the powder is filled or the pressure fluctuates, so that the coal dust flows back into the coal mill or the primary air system, and the backflow protection measures are not arranged in the prior art, so that potential safety hazards exist. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a coal-fired unit powder supply control system and method based on a small powder bin, which realize intelligent and controllable powder supply on-line switching, powder blocking treatment and backflow protection through standardized structural design and intelligent control logic so as to improve the safety, reliability and engineering applicability of the coal-fired unit powder supply. The core idea of the invention is to set a plurality of powder supply modes of powder taking of a powder pipe, powder taking of a grinding outlet and combined switching of the powder taking pipe and the grinding outlet, and provide a matched operation control method of powder taking amount adjustment, branch equalization, material level interlocking, backflow prevention, blockage clearing and on-line switching, wherein the adopted technical scheme is as follows: The coal-fired unit powder supply control system based on the small powder bin comprises a coal mill, the small powder bin, a controller, a powder pipe powder taking module, a coal mill outlet powder taking module, a combined switching module and a return powder supply and mixed access module; The controller is a DCS or auxiliary control controller and is used for executing mode management, closed loop adjustment, interlocking protection, blocking removal and on-line switching logic; the powder tube powder taking module comprises a powder tube powder taking interface, a powder tube powder taking branch, a branch isolation valve, a branch regulating valve, a branch differential pressure measuring point, a branch check valve, a branch powder taking main pipe, a branch flow equalizing structure, a purging interface and a small powder bin powder inlet connecting section; Preferably, the powder pipe powder taking interface is arranged at the horizontal stable section of the powder pipe, the lining is of a wear-resistant structure, and the powder taking direction is consistent with the main flow; the branch powder collecting main pipe is used for collecting powder from