Experimental Investigation And Numerical Simulation On Cold Gas Flow Field In Multi-Venturi CFB-FGD

Flue-gas desulfurization technology with circulating fluidized bed (CFB) has been developed and put in early commercial application stage in the world recently, and single-Venturi tube is commonly used in most of existing distributors of CFB. With the development of CFB-FGD technology, a novel design of multi-Venturi distributor is put forward. Three kinds of reformative configuration were considered for CFB-FGD of a 150MW boiler to improve the flow field in CFB-FGD main body combined with multi-Venturi distributor. In order to provide the basis on inlet configuration optimization to reveal gas-solid two phase flow, mass/heat transfer and desulfurization in CFB, the effects of inlet configuration of a multi-Venturi distributor on distribution characteristics of velocity field in multi-Venturi distributor and CFB-FGD main body were studied and numerical simulations were performed in the paper.According to simulation theory, a cold model test facility of multi-Venturi circulating fluidized bed was designed and built. Through the experiment with advanced Particle Image Velocimetry (PIV), the gas flow field in CFB-FGD main body and the air flux in multi-Venturi distributor were measured and the concept of flux warp was used to analyze and discuss the experiment results. And pressure drops across the test setup under different geometric configurations were measured. The results show that uniformity of air flux distribution among seven multi-Venturi tubes was badly affected by side inlet duck and this would bring on the poor velocity field in the CFB-FGD main body. By adding the various guiding blades at the entrance of the test setup or optimizing diameter distribution of the Venturi tube group, the flow field of CFB was improved obviously. The streamline guiding blades and optimizing diameter distribution not only make the gas flow rate in multi-Venturi distributor well-proportioned, but also prevent from the visible increase in the pressure drop of the desulfurization reactor.FLUENT was selected for the numerical simulation of fluid dynamics in fluidized bed because of the advantage of computation method and stabilization, astringency of computation of this software. Grid in computation zone was drawn by preprocessing software GAMBIT, hexahedron grid was adopted in the calculating zone, the control equations of computational model were dispersed using the finite volume method (FVM) and pressure-velocity couple was solved by Phase Coupled SIMPLE method. By the comparison of the numerical simulation results and experimental data, k -εmodel was validated for the experimental mechanism. Three different types of CFB were designed and numerical simulation of those bodies was made with the help of k -εmodel. The better CFB type was put forward based on the experiment and numerical simulation results.