Method and apparatus for the combined use of dual density measurements to achieve a fast and accurate density measurement in pneumatically transported solids

Abstract From the Canadian patent

The suspension density of a pneumatically transported solid such as coal, is obtained by using a combination of a radial gamma ray densitometer and a second, fast-response density metre. The combination is required to get the desired combination of accuracy and response time. The second measurement is used for its fast response time and may be used to control operating conditions of a gasifier. The slower, but more accurate radial radiation measurement , is used to recalibrate the second measurement approximately every 10 seconds and correct for drift thereof. The drift in the second measurement is sufficiently slow that high accuracy can be maintained by the recalibration technique.