Study On The Application Of Pressure Fluctuation In The Fluidized Bed Based On The Welch Spectrum Estimation

The fluidized bed boiler has the characteristics of low NOXemission, highcombustion efficiency, good fuel adaptability and large adjustable load. So the fluidizedbed boiler is the preferred boiler of coal cleaning and burning. At present, the constructionand operation of fluidized bed boiler has reached more than1000units, and the capacity ofthe boiler turbine generator assembly accounted for more than8%of the total installedcapacity of our country. The energy structure of our country is mainly coal. Developing thetechnology of low pollution and high-efficiency fluidized bed boiler is very important.Relevant statistics show that the application of the fluidized bed boiler will keep thegrowth rate of18%in the next few decades, so it will be the period of the fast developmentof the combustion technology of the fluidized bed boiler.In the operation process of the fluidized bed boiler, the gas-solid two-phase flow inthe furnace is complex, so the flow state and the running state of the fluidized bed boilerare difficult to detect. Researchers think that the fluctuation of fluidized bed furnacepressure reflects the dynamic characteristics in a fluidized bed gas-solid two-phase flow. Itcan also reflect the geometry structure of device, the nature of gas particle and the propertyof operational status. The fluctuation of the fluidized bed pressure is convenient to collectand the cost is low. So the information of pressure fluctuation in the fluidized bed isstudied as the object. The signal of fluidized bed pressure fluctuation is random signal andit needs to predict the power density of the signal random in the analysis. In spectralestimation, Welch spectrum estimation method, the more sub sections signal acquisitionsequence divided into, the smoother spectrum estimation is and the lower frequencyresolution is in terms of fixed length x (n). The Welch spectrum estimation method issimple and easy to use. The method is widely used that the resolution meets most projects.The Welch spectrum estimation method is applied to study the pressure fluctuation ofthe fluidized bed in three aspects based on the experimental system of the bubbling fluidized bed.(1)The other parameters are same, while the material quantities of fluidizedbed furnace are different. We collect the pressure fluctuation signal of the same pressurepoint in the fluidized bed. The pressure fluctuation signal of different material quantities isanalyzed. The changing of material quantity in the fluidized bed furnace cause the changeof the signal component intensity of the6Hz band in the fluctuation signal of the airchamber in the fluidized bed.(2) The other parameters and the material quantities are same.We collect the pressure fluctuation signals of different positions in the fluidized bed. Wecompare the pressure fluctuation signals of the different pressure measurement points inthe fluidized bed. The signal of the0~5Hz in the fluid pressure fluctuation signal isobtained and reflects the intensity of the pressure fluctuation in the fluidized bed.(3) Weapply the Welch spectrum estimation method to study the fault detection and diagnosis offluidized bed cap. We find that the11Hz spectrum band in distribution map can test anddiagnose the fault of fluidized bed cap.