A method for measuring concentration of gassolid twophase flow inside the pipe based on ultrasonic passive receiving principle has been studied. Installing ultrasonic receiver outside the elbow bent pipe of pulverized coal

through receiving ultrasonic signal produced by impact of solid particles in gassolid twophase flow with the wall of elbow bent pipe

the produced signal is transmitted through a gain booster to a computer; after processing the ultrasonic signal by the computer

the concentration of gassolid twophase flow inside the pipe can be obtained on the basis of signal characteristic variation under different solid concentration. Test results show that the online continuous measurement of solid concentration in the gassolid twophase flow can be realized by using the said method. Using rms value of the voltage as ultrasonic signal

the analysis boasts optimal resolving capability.