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Abstract: The thick-wall ECT system applied in high pressure is introduced, and the pipe wall thickness of ECT sensor is 5 mm. To analyse the effect of pipe wall thickness on ECT sensor, radius-electrode ratio is defined as the ratio of inner and outer radius of pipeline. ANSYS and Matlab are combined to simulate sensor characteristic. Linear back projection algorithm is adopted to reconstruct the images of stratified flow, core flow and annular flow with different radius-electrode ratios. The results of simulation indicate that there is a small image error under high radius-electrode ratio, and the images reconstructed from stratified flow are better than those from core flow and annular flow. The independently developed ECT system is applied to identify the flow regime of gas-solid flows in horizontal pipeline with 10 mm inner diameter in a pulverised coal dense- phase pneumatic conveying experimental setup. The pressure is up to 4.0 MPa and the solid-gas ratio is up to 11.73 kg/kg. The experimental results of eight-electrode ECT with thick pipeline sensor, which is used on the pulverised coal dense-phase pneumatic conveying experimental setup, are given. Finally, the Fluent simulation of concentration distribution at the similar condition is introduced to validate the ECT imaging result.
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1 Introduction
Coal gasification technology provides a clean and high- efficient way to utilise coal. The entrained pulverised coal gasification technology is a certain kind of large-scale coal gasification technology. Dense-phase pneumatic conveying of pulverised coal under high pressure is an important technique for entrained pulverised coal gasification [1].
Two-phase (multi-phase) flow is a commix flow mode that existed widely, and its parameter measurement technology takes more and more important role in science research and industrial production. Thus process tomography comes out. Electrical capacitance tomography (ECT) is one of the most mature and promising methods, which measures the absolute capacitance change of multi-electrode sensor owing to the change of dielectric permittivity being imaged, and then reconstructs the cross-section images using the measured raw data with a suitable algorithm. It has characteristics such as low cost, fast response, non-intrusive method, broad application and safety [2, 3].
As shown in Fig. 1, ECT system includes sensor, capacitance measuring circuit and imaging computer. An ECT sensor consists of...