Study On Gas-solid Flow Characteristics Of Internal Circulating Fluidized Based On J Type Loop Seal

The internal circulating fluidized bed had been used for biomass gasification and liquefaction sequentially.With our country further promoting development of clean energy and energy conservation and emission reduction,demand for energy conversion efficiency and production methods had been raised,which needed to be optimized and updated by structures of internal circulating fluidized bed.The gas-solid flow are multiphase flow,nonlinear and strong coupling in new internal circulating fluidized beds,the calculation methods of minimum fluidization velocity,solid particle circulation described for gas-solid flow characteristics and Two Fluid Model for numerical simulation are very difficult to be adapted continually.Therefore,new calculation methods of minimum fluidization velocity and solid particle circulation and improved Two Fluid Model and its applications in numerical simulation were focused on in the paper.The regulation characteristics of J-Loop Seal were studied on emphasis,and its feasibility for bed material circulating device was discussed,which could provide important basis for configuration,operation and control of fluidized bed.A cold experimental device was built for minimum fluidization velocity and its measurement method was given in the paper.Measurement of minimum fluidization velocity was given for four different particle diameters of silica sand in the cold experiment under normal temperature and pressure.The results showed that minimum fluidization velocity increased with particle diameters increasing;and it had nothing to do with height of the bed.These were verified by Ergun equation.Compared experimental results with common calculations of empirical or semi empirical formulas in literature for minimum fluidization velocity.The results showed that there was a bigger error between calculation values by empirical formulas and experimental values.Accordingly,a new calculation method was given.Its prediction values were in good agreement with the experimental results,its maximum relative error was 9.5%.It was proved that new calculation method was feasible,and laid a foundation for further research of gas-solid flow characteristics.J-Loop Seal was designed and used for internal circulating fluidized bed.A cold experimental device of two chambers internal circulating fluidized bed based on J-Loop Seal was built,and the key parameters of fluid mechanics describing gas-solid flow characteristics were measured.Mathematical model was set up by analysis for structure of J-Loop Seal.Solid particles circulation was regulated by J-Loop Seal,which was studied based on layer height difference and dynamic head and resistance coefficient three local parameters.A new calculation method of solid particles circulation was given,and its feasibility was verified by the experiment.The important factors affecting three local parameters were analyzed,and the experiments was carried out for them.The cold experiments were designed for influences of left and right lateral blow and particle diameter that had on three local parameters,and revealed their relationships respectively.The height difference was linear relationship with lateral blow approximately,and it increased as particles diameter increased.The dynamic head was only linear relationship with the left lateral blow approximately,was hardly affected by the right lateral blow,and it increased as the particles diameter increased.The relationship between the resistance coefficient and the right lateral blow was exponential function,and the resistance coefficient almost was not affected by particle diameter.Predictive values for minimum fluidization velocity based on Syamml-O Brien drag model was calculated,it was much smaller than the experimental values for minimum fluidization velocity.Therefore,Syamml-O Brien drag model was modified.The solution process of SIMPLE algorithm was analyzed.The numerical solution of two-dimensional unsteady flow problem would diverged.So SIMPLE algorithm was improved.The experimental device of two chambers internal circulating fluidized bed based on J-Loop Seal was simulated,which adopted for Modified Syamml-O'Brien drag model and SIMPLE algorithm improved.The results showed that simulation and experimental values were in good agreement in a certain range of error,could correctly reflect the actual gas-solid hydrodynamic behavior.It was verified that modified Syamml-O'Brien drag model and SIMPLE algorithm improved was effective and reliable.It provided a new method for structure design and theory research of fluidized bed.