Design and Experimental Study on the Pulverized Coal Concentration Sensor Based on Gamma-Ray Absorption Method

The device was developed to accurately measure the Concentration of pulverized coal in the pneumatic conveying pipe. The sensor assembly was composed of γ-ray source, tube of the sensor, ionization chamber fill with inert gas electrometer and lead cannon tube shield. The γ point source was fixed at the cross-section centre of the pipe, the collimation exit portal was vertical to the axis line of the conduct, in which the outgoing beam of the γ rays was assumed at the plane 360 degrees; the profile of the ionization chamber was designed ring cross section, independent mult-cavity. The γ-ray from the source penetrated the gas-solid two phase flow and the single tube wall, arrived at the corresponding independent cavity. The inert gas filled in the cavity was ionized by the γ-ray, the ions was collected by the high voltage plates, the ionic stream was converted into direct voltage by the electrometer in the cavity, as the output of the cavity. The concentration of the corresponding sector in the tube could be determined according to the law of γ-ray mutual effect with the matter. The arithmetic mean of the output voltages from the electrometers in the cavities of the ionization chamber was taken as the measured value of volume concentration of the pulverized coal in the tube. The proving trial shows that the input-output character of the sensor assembly was the phase distribution; the measuring accuracy was superior 2%, the γ-ray radioactivity requirement was reduced obviously as only single tube wall was required to be penetrated by γ-ray.