Study On Relationship Between Particle Flow Patterns And Pressure Fluctuations Signals In The Conveying Inclined Standpipe

As an essential component of most circulating fluidized bed systems,the inclined standpipe is mainly used in particle conveying between two parallel containers or transfering solids collected in the cyclone back to the dense fluidized bed by gravity.In addition,it maintians the pressure balance of circulating system.The inclined standpipe is a nonlinear complicated system which is difficult to be predicted and optimized operation without an accurate theoretical model.However,pressure fluctuations signals,which emerge in gas-solid two phase flow,include abundant information on particle flow in the inclined standpipe which could reflect flow patterns and flow stability.In the two sets of experimental system,the pressure fluctuations signals were investigated with different signal processing methods to effectively distinguish flow patterns,as well as understanding its conveying mechanism and instructing practice for basic research and industrial application.The mian conclusions are as follows:To investigate flow patterns and flow stability in the 45° inclined standpipe of 150-mm diameter by adopting two kinds of valve control mechanism,the pressure fluctuations were systematically measured.The experimental results show that as the open rate of the butterfly valve increases,the flow patterns successively display creeping flow,undulated flow,gas-solid stratified flow and fluidized flow;As the open rate of the plate valve increases,the flow patterns are creeping flow,dense-phase fluidized flow,dilute-phase fluidized flow in sequence.The characteristic values of pressure fluctuations signals were well correlated with flow patterns by means of using various signal processing methods,such as standard deciation,power spectral density function,probabiltity density function.These methods described above are relatively simple which could effectively identify flow patterns and reflect flow stability.To inspect the displacement value in the inclined standpipe,different flow patterns possess different vibration strength which is induced gas-solid two phase flow.The displacement of vibration was most severe when the flow pattern was in dilute-phase fluidized,because of bubble coalescence and bubble breakup.In addition,this thesis also investigate flow patterns and flow their variability in the 80-mm diameter inclined standpipe fitted with plate valve under different incination of the pipe.The experimental research demonstrates that as the inclined angle increases,paiticle flow patterns exist significantly different and draw an operation phase diagram which can conveniently and accurately obtain flow patterns in the inclined standpipe.Meanwhile,pressure signals were measured and analysis particle flow characteristics in a standpipe set at 30°,45° and 60° to the horizontal.Particle flow patterns and pressure fluctuation characteristics were comparatively analyzed at different parts of the 45° inclined standpipe.Flow patterns above the plate valve are creeping flow,dense-phase fluidized flow,dilute-phase fluidized flow in sequence,while there is only gas-solid stratified flow below the plate valve.By using signal processing methods,the flow patterns could be obviously recognized and flucuation characteristics of the flow patterns could be understanded.