Comparison of techniques for measuring CFB solids circulation rates at low and high temperatures

Abstract

The solids circulation rate between two reactors is a key parameter in circulating fluidized bed reactor processes. This paper reports on attempts to establish the reliability of a novel thermal-tracing technique to provide useful solid circulation information for industrial-scale systems. A novel butterfly valve technique was developed to test the thermal-tracing technique at high temperatures. Closing the valve causes solids to accumulate in the downcomer of a pilot gasifier. The level of the bed top surface was tracked with high-temperature capacitance sensors. The circulation rates were also estimated using two indirect techniques, the firsts based on a pressure balance between the riser and the bubbling bed, and the second utilizing a balance of all input and output energy streams to and from the bubbling bed reactor. Agreement among the solids circulation rates from these four independent techniques is encouraging, given the difficulty in obtaining accurate measurements.