Research On On-line Measurement Of Velocity And Pulverized Coal Concentration Of Primary Air Using Ultrasonic Method

The accurate measurement of flow velocity and pulverized coal concentration of the primary air is one big technological challenge that call for immediate solution in improving the performance of power station boilers. With advantages in the area of thermotechnical measurement such as non-contact and self-cleaning, the ultrasonic method can be used to measure pulverized coal concentration and flow velocity and enjoys broad application prospects.The purpose of this research is to develop an on-line measurement device of velocity and pulverized coal concentration of primary air based on the ultrasonic method. To achieve this purpose, the research is conducted in the following steps.(1) Some of pulverized coal’s property parameters are measured using experimental method, and calculation on the velocity and sound attenuation of ultrasonic propagating in the gas-solid medium are made with the existing theoretical model. The effects of property parameters on the predictions are also analyzed.(2) Comprehensive design for the measurement device of velocity and pulverized coal concentration of the primary air are made. Suitable ultrasonic sensors, signal driving and receiving equipment are applied, a test bench for powder feeding, another test bench for imitating working condition of primary air and protection physical struction for the sensors are designed, supporting software are developed, the measurement device is successfully set up. and then the first engineering prototype is developed based on these work,(3) On the simulation experiment table, the feasibility of measuring the velocity of primary air using ultrasonic correlation method is verified. The result of this experiment shows that the test outcome using ultrasonic correlation method matches that of the pitot tube.(4) Based on the research on the basic properties of ultrasonic sensors, experiments on the sound attenuation of ultrasonic wave in air-pulverized coal medium are conducted. The formula between sound attenuation and pulverized coal concentration is obtained after slight rectification. The feed concentration of the experiment table is thus successfully detected using the aforementioned fitted formula.