| Due to the increasingly shortage of coal resources in our country,and the protection of the environment which is the demand for the development of the current era,our country has vigorously developed new-type clean energy power generation industries such as wind energy,solar energy,hydropower energy and nuclear energy.In recent years,due to the increasing scale of renewable energy grids and renewable energy power generation fluctuations,resulting in thermal power units to strengthen the depth of peaking capacity.For example,in the season of wind power generation,in order to reduce the rate of abandonment,thermal power units need to reduce the load of power generation,then thermal power units need to be under 50% of the ultra-low load operating conditions.When the utility boiler is operating under the condition of ultra-low load,lead to boiler combustion instability occurs,the combustion temperature of the hearth to be low,fire extinguishing of the hearth and more serious explosion of the hearth.Therefore,it is the premise to ensure the boiler's safe and stable operation under the ultra-low load and the important guarantee to implement the boiler combustion control system optimization.The combustion stability is the most critical part of the stable operation of the entire unit.After a large number of experimental analysis,boiler's oxygen signal,hearth's pressure,air volume and other parameters affected the stability of the combustion of the boiler.However,the fire detection of the FSSS system is only based on the presence or absence of the flame detection signal.If the signal detection of the fire detection is not allowed,the misjudgment and the leakage judgment may be caused.In response to this problem,this paper presents a combustion stability judgment method based on the D-S evidence theory.In response to this problem,this paper presents a combustion stability judgment method based on the D-S evidence theory.In this paper,D-S evidence theory can make full use of the characteristics of multiple sensor information,selected the parameters that affect the stable combustion of the boiler as evidence,obtained these parameters in the boiler under a load condition stable operation of the data as a typical sample,extracted the combustion characteristics of these signals,normalized these data.According to the distribution formula of reliability function,the reliability function assignment value of each evidence in fire mode and fire extinguishing mode is calculated.Then according to the joint rules of D-S evidence theory,let these data fusion,finally,got the judgment result.The experimental results show that the method is consistent with the historical records,which proves the correctness of the method.According to boiler thermal calculation formula,the boiler combustion control system model is established.This paper analyzes the impact of the coal quality changes,start and stop the different ways and different air excess coefficient on boiler operating parameters.The experimental results can provide operational guidance to operators to ensure the safe and stable operation of the boiler.The experimental results shows:(1)With the increase of moisture and ash content in coal,the theoretical combustion stability decreases and the smoke temperature at the furnace outlet increases.(2)When the bottom grinding halt the furnace outlet smoke temperature is highest.(3)With the increase of excess air system,the flue gas temperature at the furnace outlet gradually increases.In Inner Mongolia JingKe Power Plant conducted the ultra-low load put into operation experiment,Accorded to the above theoretical analysis and experimental results,for different operating conditions to make the appropriate combustion optimization adjustment,makes Jingke power plant's 330 MW boilers can be safe and stable operation at 30% load conditions.The experiments to achieve the desired results,and proved the practicality and accuracy of the method discussed in this article. |
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