CN-117358450-B - Spray gun sequential control method of denitration system

CN117358450BCN 117358450 BCN117358450 BCN 117358450BCN-117358450-B

Abstract

The invention discloses a spray gun sequential control method of a denitration system, which relates to the field of denitration and comprises the steps of adjusting air pressure and urea solution in a spray gun and determining atomization effect, determining the opening of a flow regulating valve of the spray gun according to the emission of nitrogen oxides in a start-stop stage of a machine set, adjusting the opening of the flow regulating valve in real time according to the difference between the current emission of the nitrogen oxides and a preset target emission of the nitrogen oxides, determining the exceeding time length of the nitrogen oxides with exceeding standard discharge capacity according to the fluctuation range of loads in the start-stop process of the machine set after the machine set is started and stopped for a period of time, judging whether the exceeding standard time length meets the preset exceeding standard time length, adjusting and adjusting the delay time of the flow regulating valve of the spray gun according to the difference between the exceeding standard time length and the preset exceeding standard time length, judging whether to put the spray gun and determine the needed put-back quantity according to the opening condition of the flow regulating valve of the spray gun, and determining the put-back time point of the spray gun according to the temperature of a catalyst. The discharge capacity of the nitrogen oxides is effectively prevented from exceeding the standard at the start-stop stage of the unit, and the utilization rate of urea is improved.

Inventors

SHA HAO
Zhu Guquan
ZHANG ZHIPENG
Bao Jixiong
ZHENG YONGFENG
FENG XIAOHUA
XU HUI
ZHU YOUHONG
LI ZHIHUA
PAN YUE
YANG QUN

Assignees

华能苏州热电有限责任公司

Dates

Publication Date: 20260505
Application Date: 20230919

Claims (8)

1. A spray gun sequential control method of a denitration system, the method comprising: Adjusting the air pressure of compressed air and urea solution in the spray gun, and determining the corresponding atomization effect; In the start-stop stage of the unit, detecting the emission amount of nitrogen oxides in the running process of the unit in real time, determining the flow regulating valve opening of the spray gun according to the emission amount of the nitrogen oxides, and adjusting the flow regulating valve opening of the spray gun in real time according to the difference value between the current emission amount of the nitrogen oxides and the preset target emission amount of the nitrogen oxides; After the unit is started and stopped for a period of time, determining the corresponding exceeding start and end time when the nitrogen oxide discharge capacity exceeds the standard according to the fluctuation range of the load in the unit starting and stopping process, and calculating the exceeding duration; judging whether the exceeding time length meets the preset exceeding time length, if the exceeding time length is longer than the preset exceeding time length, calculating the delay time for adjusting the flow regulating valve of the spray gun according to the difference between the exceeding starting time corresponding to the exceeding of the nitrogen oxide discharge and the adjusting time of the flow regulating valve of the spray gun; Calculating the difference value between the exceeding time length and the preset allowable exceeding time length, and adjusting the delay time of the flow regulating valve of the regulating spray gun according to the difference value between the exceeding time length and the preset allowable exceeding time length; judging whether to throw the spray gun or not according to the opening condition of the spray gun flow regulating valve and determining the quantity of the spray guns required to throw the spray gun or not; And detecting the temperature of the catalyst in the reaction process in real time, determining the switching time point of the spray gun according to the temperature of the catalyst, and switching the spray gun in time according to the switching time point.
2. The spray gun sequential control method of a denitration system according to claim 1, wherein adjusting the air pressure of compressed air and urea solution in the spray gun and determining the corresponding atomization effect comprises: The method comprises the steps that different compressed air and air pressure of urea solution in a spray gun correspond to different atomization effects, the air pressure of the compressed air and the air pressure of the urea solution in the spray gun are adjusted, when the atomization effects reach preset requirements, a unit is started to operate, when the temperature of flue gas at an inlet of a boiler reaches the temperature required by sequential control starting of the spray gun, a flushing water valve of the spray gun is sequentially closed, and a switching valve and a flow regulating valve of the spray gun are started.
3. The spray gun sequential control method of a denitration system according to claim 1, wherein determining the flow rate valve opening of the spray gun according to the discharge amount of nitrogen oxides comprises: Determining a corresponding urea injection amount according to the emission amount of nitrogen oxides generated in the boiler and the reaction proportion of the nitrogen oxides and urea, determining a corresponding spray gun flow regulating valve opening according to the urea injection amount, and regulating the flow regulating valve of the spray gun in real time based on the spray gun flow regulating valve opening.
4. The spray gun sequential control method of a denitration system according to claim 1, wherein determining an over-standard start-end time corresponding to when the discharge amount of nitrogen oxides exceeds standard according to a fluctuation range of a load in a start-stop process of a unit and calculating an over-standard time interval comprises: detecting the fluctuation range of unit load in the unit start-stop process, detecting the fluctuation range of nitrogen oxide discharge capacity in the fluctuation range of unit load, judging whether the discharge capacity of nitrogen oxide exceeds the standard in the fluctuation range of nitrogen oxide discharge capacity, if the discharge capacity of nitrogen oxide exceeds the standard, recording the corresponding exceeding start-end time when the discharge capacity of nitrogen oxide exceeds the standard, and calculating the exceeding duration according to the exceeding start-end time.
5. The spray gun sequential control method of a denitration system according to claim 4, wherein calculating the delay time for adjusting the spray gun flow rate regulating valve according to the difference between the exceeding start time corresponding to the exceeding of the nitrogen oxide discharge amount and the adjusting time of the spray gun flow rate regulating valve comprises: The corresponding out-of-standard starting time is set to be T1 when the discharge capacity of the nitrogen oxides is out of standard, the out-of-standard ending time is set to be T2, the adjusting time of the spray gun flow regulating valve is set to be T0, the delay time of the spray gun flow regulating valve is set to be T', T′=T0-T1; The exceeding time length is set to be L1, the allowable exceeding time length is set to be L2, L1=T2-T1。
6. The spray gun sequential control method of a denitration system according to claim 5, wherein calculating a difference between the exceeding time period and the preset allowable exceeding time period, and adjusting the delay time of the spray gun flow regulating valve according to the difference between the exceeding time period and the preset allowable exceeding time period comprises: setting the time difference between the exceeding time length and the preset allowable exceeding time length as L', L′=L1-L2; The method comprises the steps that the emission amount of nitrogen oxides is S in the duration difference L', and the emission amount S of the nitrogen oxides is the difference value between the actual exceeding standard displacement and the allowable exceeding standard displacement of the nitrogen oxides in the start-stop process of a unit; And determining the emission quantity S of the nitrogen oxides corresponding to the time length difference L ' according to the time length difference L ', and adjusting the delay time T ' of the flow regulating valve of the regulating spray gun according to the emission quantity S of the nitrogen oxides.
7. The spray gun sequential control method of a denitration system according to claim 1, wherein judging whether to throw back spray guns and determining the number of required throw back spray guns according to the opening condition of a spray gun flow rate valve adjusting comprises: Presetting a first threshold value of the opening of a spray gun flow regulating valve and a second threshold value of the opening of the spray gun flow regulating valve, exiting the spray gun when the opening of the spray gun flow regulating valve is lower than the first threshold value of the opening of the spray gun flow regulating valve, and determining the quantity of the spray gun to be exited according to the difference between the injected urea quantity in the boiler and the actual required urea quantity at the moment; and when the opening of the spray gun flow regulating valve is higher than a second threshold value of the preset spray gun flow regulating valve, the spray guns are put into the spray gun, and the quantity of the spray guns required to be put into is determined according to the difference between the injected urea quantity in the boiler and the actual required urea quantity.
8. The spray gun sequential control method of a denitration system according to claim 7, wherein the method for determining the time point of the spray gun to be put back according to the temperature of the catalyst and timely putting back the spray gun according to the time point of the spray gun to be put back comprises the following steps: A preset catalyst temperature threshold, wherein when the catalyst temperature reaches the preset catalyst temperature threshold, a time point when the catalyst temperature reaches the preset catalyst temperature threshold is taken as an input time point of the spray gun, and when the catalyst temperature is lower than the preset catalyst temperature threshold, a time point when the catalyst temperature is lower than the preset catalyst temperature threshold is taken as an exit time point of the spray gun; And on the basis of the time point of the throwing and the withdrawing of the spray guns and the quantity of the spray guns required to be thrown and withdrawn, when the spray guns need to be withdrawn, sequentially closing a flow regulating valve of the spray guns, opening a flushing water valve of the spray guns to flush the spray guns, and closing a switching valve of spray gun solution.

Description

Spray gun sequential control method of denitration system Technical Field The application relates to the technical field of denitration, in particular to a spray gun sequential control method of a denitration system. Background The nitrogen oxide treatment technology mainly comprises a low nitrogen oxide combustion technology, an SNCR (selective non-catalytic reduction) technology, an SCR (selective catalytic reduction) technology, an oxidation method and a mixed powder technology. The current SCR denitration technology is the most widely applied denitration technology of a coal-fired power plant, and the principle of the technology is that ammonia gas or urea is sprayed into a boiler by using a spray gun to be mixed with NOx in flue gas, oxidation-reduction reaction occurs under the action of a catalyst, N2 and H2O are generated, so that the aim of ultralow emission of nitrogen oxides is fulfilled. However, for the gas turbine unit, because the load peak regulation task is carried, the start and stop of the unit are relatively frequent, during the start and stop of the unit, the load fluctuation of the unit is large, the NOx emission can fluctuate along with the change of the load and the operation condition of the unit, during the process, because the manual adjustment has the condition that the adjustment of the flow rate adjusting valve of the urea solution of the spray gun is not timely, the time node and the number of the start and stop of the urea spray gun system are not clear, the condition that the nitrogen oxides exceed the standard and the urea solution is wasted still occurs during the start and stop stage of the unit. Therefore, how to timely adjust the flow regulating valve of the spray gun and timely throw and withdraw the spray gun in the start-stop stage of the unit so as to prevent the discharge of nitrogen oxides from exceeding the standard and improve the utilization rate of urea is a technical problem to be solved at present. Disclosure of Invention The invention provides a spray gun sequential control method of a denitration system, which is used for solving the technical problems of exceeding of nitrogen oxide emission and low urea utilization rate caused by untimely regulation of a spray gun flow regulating valve and untimely throwing and retreating of a spray gun in the unit start-stop process of the denitration system in the prior art. The method comprises the following steps: Adjusting the air pressure of compressed air and urea solution in the spray gun, and determining the corresponding atomization effect; In the start-stop stage of the unit, detecting the emission amount of nitrogen oxides in the running process of the unit in real time, determining the flow regulating valve opening of the spray gun according to the emission amount of the nitrogen oxides, and adjusting the flow regulating valve opening of the spray gun in real time according to the difference value between the current emission amount of the nitrogen oxides and the preset target emission amount of the nitrogen oxides; After the unit is started and stopped for a period of time, determining the corresponding exceeding start and end time when the nitrogen oxide discharge capacity exceeds the standard according to the fluctuation range of the load in the unit starting and stopping process, and calculating the exceeding duration; Judging whether the exceeding time length meets the preset exceeding time length, if the exceeding time length is longer than the preset exceeding time length, calculating the delay time for adjusting the flow regulating valve of the spray gun according to the difference between the exceeding end time corresponding to the exceeding of the nitrogen oxide discharge and the adjusting time of the flow regulating valve of the spray gun; Calculating the difference value between the exceeding time length and the preset allowable exceeding time length, and adjusting the delay time of the flow regulating valve of the regulating spray gun according to the difference value between the exceeding time length and the preset allowable exceeding time length; judging whether to throw the spray gun or not according to the opening condition of the spray gun flow regulating valve and determining the quantity of the spray guns required to throw the spray gun or not; And detecting the temperature of the catalyst in the reaction process in real time, determining the switching time point of the spray gun according to the temperature of the catalyst, and switching the spray gun in time according to the switching time point. In some embodiments of the application, adjusting the air pressure of the compressed air and urea solution in the spray gun and determining the corresponding atomization effect comprises: The method comprises the steps that different compressed air and air pressure of urea solution in a spray gun correspond to different atomization effects, the air pressure of the compressed air and the air pres