CN-122015121-A - Coal-fired unit depth peak shaving and combustion stabilizing control system and method based on small powder bin

CN122015121ACN 122015121 ACN122015121 ACN 122015121ACN-122015121-A

Abstract

The invention belongs to the technical field of depth peak regulation operation and combustion powder preparation cooperative control of a coal-fired generator set, and particularly relates to a depth peak regulation and combustion stabilization control system and method of a coal-fired generator set based on a small powder bin. The invention constructs a combustion stability criterion of multi-parameter fusion of a combustion side and a powder making side based on flame signals, CO, hearth negative pressure, coal powder concentration equivalent quantity and the like, is driven by measurable parameters and clear criteria, actively intervenes low-load stable combustion, and realizes preventive stable combustion.

Inventors

XIANG JUN
JIANG LONG
WANG YI
SU SHENG
HU SONG
CHEN DEZHI
CHEN LEI
LI JUNMENG
YANG YIQING
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 depth peak regulation and combustion stabilization control system based on the small powder bin is characterized by comprising a combustor, a main powder supply path, a small powder bin powder supply path, a switching and isolating component, a measuring unit and a controller; The main powder supply path comprises a coal mill, a powder supply device, a main powder supply conveying pipeline and a primary air pipe, wherein a mixing point is arranged on the primary air pipe; the small powder bin powder supply path comprises a small powder bin, a powder discharging and metering device, a small powder bin conveying device and a branch pipeline, wherein the branch pipeline is connected with a mixing point arranged on the combustor or the primary air pipe; The switching and isolating component comprises an electric valve, a pneumatic valve, a check valve and a quick-opening valve which are arranged at the front and back of the outlet of the branch pipeline of the small powder bin and the mixing point; the measuring unit is used for feeding back the material level of the small powder bin, the operation of a powder outlet executing mechanism of the small powder bin, the detection of the main powder supply amount or the powder supply amount, the primary air quantity, the operation of a coal mill or the tripping state, and the detection of combustion stability parameters, wherein the combustion stability parameters comprise flame detection signals, hearth temperature, hearth negative pressure, O 2 and CO parameters; The controller is used for executing state machine control of standby preparation, operation, emergency continuous supply, cooperative stable combustion, smooth back switching and resetting according to the load, the powder supply state, the combustion stability parameter and the interlocking state.
2. The stable combustion control system of claim 1, wherein the small powder bin conveying device is a pneumatic conveying device or an injection device.
3. The stable combustion control system of claim 2, wherein the controller is a crew DCS or an auxiliary control system.
4. A coal-fired unit depth peak shaving steady burning control method based on a small powder bin, which is implemented based on the steady burning control system according to any one of claims 1-3, and is characterized by comprising the following steps: step S1, pre-filling powder and checking, and triggering a small powder bin standby preparation logic by a controller before a coal-fired unit enters a deep peak-shaving low-load working condition or in low-load operation; Step S2, monitoring criteria are obtained, wherein the controller obtains the following indexes in a fixed period of 1S-5S: (1) The main powder supply state is a coal mill operation or tripping signal, a main powder supply amount, a main powder supply fluctuation range and a main powder supply lower limit margin; (2) Combustion stability parameters, namely flame stability indication, hearth temperature or burner outlet temperature, hearth negative pressure fluctuation, O 2 and CO parameters; (3) Primary air pulverized coal concentration equivalent index. Step S3, when any one of the following criteria is met, the controller operates the powder supply path of the small powder bin: (1) Flame stability indication is lower than a threshold value, hearth temperature downlink overrun, hearth negative pressure fluctuation increase, CO rise or burner outlet temperature fluctuation overrun; (2) The main powder supply risk criterion of the powder making side comprises that the main powder supply quantity reaches the minimum stable combustion powder supply quantity, the fluctuation of the main powder supply exceeds the limit, the running stability margin of the coal mill is insufficient, and the unit load is lower than a set threshold; (3) The tripping criterion is that a tripping signal of the coal mill is detected; S4, tripping and emergency, namely executing a tripping and emergency continuous supply strategy by the controller when the tripping signal of the coal mill is monitored; s5, cooperative stable combustion, namely executing primary air and powder supply cooperative control by a controller during powder supply of the small powder bin; and S6, smooth back cutting and resetting, wherein when the main powder supply path is recovered and the back cutting condition is met, the controller executes smooth back cutting resetting.
5. The steady burning control method according to claim 4, characterized in that in step S1, it comprises: S1.1, pre-filling powder to enable the material level of a small powder bin to reach a set target; s1.2, checking availability, wherein the availability comprises that the material level of a small powder bin is not lower than a low limit, a powder outlet valve is in an actionable state, a powder feeding executing mechanism is fed back normally, a conveying pipeline is subjected to pressure difference or blockage diagnosis, no abnormality exists, and the interlocking meets the operation condition; S1.3, self-checking and setting, namely setting a small powder bin control state as standby, and recording available inventory and maximum continuous powder supply capacity.
6. The stable combustion control method according to claim 5, wherein in the step S2, the obtained primary air pulverized coal concentration equivalent index calculation formula is: , Wherein C eq is the primary air powder concentration, Q Main unit is the main powder supply quantity, Q Small powder bin is the powder supply quantity of the small powder bin, and V PA is the primary air quantity.
7. The stable combustion control method according to claim 6, wherein in the step S3, the operation of the powder supply path of the powder delivering small powder bin includes: (1) Opening a small powder bin branch valve to a pre-opening position; (2) Starting a powder feeding and metering executing mechanism; (3) The powder supply amount of the small powder bin is increased from 0 to the target powder supply amount according to the slope limit; (4) And recording the operation time and entering a low-load auxiliary state.
8. The steady burning control method according to claim 7, wherein in the step S4, the skip grinding emergency follow-up strategy includes: (1) The small powder bin powder supply is rapidly increased from the current value to the emergency target powder supply amount, and the powder supply at the side of the burner is ensured not to be lower than the minimum stable combustion powder supply amount within the set response time; (2) And judging the broken powder and correcting the closed loop, namely if the flame stability indication continues to descend or the CO abnormally ascends, further improving the powder supply quantity of the small powder bin or triggering stronger stable combustion measures, wherein the stronger stable combustion measures comprise limiting the primary air ascending and temporarily and slightly increasing the stable fuel.
9. The stable combustion control method according to claim 8, wherein in the step S5, the primary air and the powder supply cooperative control includes: (1) On the premise of ensuring that the primary air quantity meets the safety lower limit of the burner, C eq is raised or maintained in a target zone by improving the powder supply quantity preferentially; (2) If the primary air quantity is smaller than the safety lower limit and the primary air is still higher than the minimum lower limit, reducing the primary air quantity or limiting the primary air increment, and if the primary air quantity reaches the lower limit, improving the C eq by only improving the powder supply quantity of the small powder bin; (3) And taking the flame stabilizing indication as an outer ring feedback, and controlling the powder supply quantity of the small powder bin to fall back to an economic target value when the flame stabilizing indication is restored to a safe interval and continuously stabilized for a set time.
10. The stable combustion control method according to claim 9, wherein in the step S6, the back-cut condition is that the coal mill is resumed and the main powder supply amount is resumed to the target margin, and the combustion stability parameter is continuously stabilized for the set time of 30S-300S; The smooth loop-back reset includes: (1) Smooth connection, namely, main powder supply is increased according to a set slope, and powder supply in a small powder bin is decreased according to the set slope; (2) And (3) withdrawing and resetting, namely closing a small powder bin branch valve when the powder supply quantity of the small powder bin is reduced to an withdrawing threshold value and stably reaches a set time, stopping the operation of the small powder bin branch valve to the powder executing mechanism, and returning the small powder bin to standby stock, wherein the state returns to hot standby or standby.

Description

Coal-fired unit depth peak shaving and combustion stabilizing control system and method based on small powder bin Technical Field The invention belongs to the technical field of depth peak regulation operation and combustion powder preparation cooperative control of a coal-fired generator set, and particularly relates to a depth peak regulation and combustion stabilization control system and method of a coal-fired generator set based on a small powder bin. Background With the increase of the new energy duty ratio in the electric power system, the coal-fired unit needs to be quickly and frequently adjusted within a wider load range, and the deep peak shaving and long-time low-load operation are gradually normalized. Under the low load working condition, the thermal load of a hearth is reduced, the combustion stability margin is reduced, the unit is more sensitive to the continuity of coal powder supply and the stability of coal powder concentration, once powder supply fluctuation occurs, flame swing, burnout deterioration and even fire extinguishing risks are easily caused, the conventional coal-fired unit usually takes a coal mill and a powder supply system as main powder supply channels, and under the deep peak shaving low load condition, the coal mill is always in a low-output, low-ventilation or frequent start-stop state, and the conditions of skip grinding or powder breakage are easily caused, so that the fuel supply of the coal-fired unit is severely fluctuated to cause fire extinguishing of a boiler. In order to solve the problems, chinese patent CN110645588B discloses a boiler system which comprises a boiler and a pulverizing unit, wherein the boiler is provided with at least one burner, the pulverizing unit comprises at least one coal mill, the outlet of each separator of each coal mill is connected with at least one powder feeding pipeline leading to the burner, the outlet of each separator of each coal mill is also connected with an auxiliary powder pipe, the auxiliary powder pipe is connected with a powder storage bin, when the coal mill trips or breaks coal, a control device controls the powder storage bin to be communicated with the powder feeding pipeline to enable the powder storage bin to start powder feeding, and the powder feeding pipeline serves as an air duct to blow coal powder to the burner to maintain the fuel supply of the burner, so that fire extinguishment of the boiler is avoided. Chinese patent CN117109024A discloses a coal-fired unit ultra-low load stable operation pulverizing system and a control method, which are used for modifying a medium-speed mill direct-fired pulverizing system, connecting a coal powder bin in series on a coal mill powder outlet pipeline connected with a bottom layer combustor, modifying the coal mill direct-fired pulverizing system into a middle storage type pulverizing system, supplying powder only by using the system under ultra-low load, improving the concentration of wind powder, improving the distribution uniformity of the wind powder, reducing the influence of the instability of coal mill pulverizing on low-load stable combustion of a boiler, retaining direct firing of other coal mills, and taking full load into consideration. Chinese patent CN117190170a discloses a middle powder bin combustion powder feeding system for boiler low-load stable combustion, comprising a coal mill, a powder feeding unit and a hearth, wherein the middle powder bin, a powder feeder and a mixer are arranged, and can supply powder to a burner independently of the coal mill, support the single powder supply mode of the coal powder bin storage and the powder bin, and realize path isolation through the switch of a plugboard door. The prior art introduces a powder storage bin or an intermediate powder bin in structure, has a certain powder supply buffering or independent powder supply capacity, reduces the coupling degree of a coal mill and a boiler, can realize the emergency continuous powder skip grinding or the low-load stable combustion capacity of the boiler, but has a certain defects in practical application, firstly, the prior art scheme lacks comprehensive combustion stability criteria, passively responds to a tripping signal of the coal mill or switches according to a manual judgment working condition, cannot actively promote a stable combustion margin before powder breakage, is easy to cause combustion fluctuation or response delay, secondly, the stable combustion control of the prior art scheme triggers the starting of a powder feeder based on a single skip grinding, or the manual switching working condition of an inserting plate door, or powder level control, does not form complete control logic and closed loop control flow, cannot be integrated with the prior DCS, thirdly, the prior art scheme highly depends on a main primary air pipe as a conveying channel, does not form double redundancy of an air source and a powder source, and has a large risk of failure in th