The Numerical Simulation And Experimental Study Of The Secondary Air's Jet Track And Its Influence In CFB

Circulating Fluidized Bed (CFB) burning technology is one of the most significant clean coal burning technologies, and it is developing rapidly in China for these years. However, the penetrate ability of secondary air (SA) in CFB nowadays is limited, which leads to inefficient burning. This problem restricts the development of CFB burning technology. So it is very important to study on the spread track of SA in CFB and get the rule for the designation of SA spout and the selection of the jet speed parameters.In this paper, the author studied the field, track of SA and its effect to the gas-solid flow by numerical simulation and experimental research. In chapter 2, the author introduced the different theoretical models in numerical simulation and discussed the advantages/disadvantages of all models respectively and finally decided which to use to simulate the gas-solid flow model.In chapter 3, the author used software to simulate the CFB and studied how the running parameters affect the penetrability of SA and the mixture of gas and solid. The author got the result as the penetrate deepness of SA is proportional to diameter of nozzle and jet speed,and inversely proportional to particle concentration and density and diameter. The simulation result also shows that the temperature of PA and SA and the position of nozzle will impact the penetrate deepness too.In Chapter 4, the author used simplified physical model to study the vertical into the horizontal jet stream flow and mass transfer problems, and established SA jet trajectory's physical model, in order to get the center track of the jet momentum differential equations and the mass flow rate variation rule. At the same time build a test bed to obtain the mass exchange coefficient between jet and primary jet in theoretical model. The prediction of jet track by theoretical model matches with the experimental results.In Chapter 5, the author discussed the effects of SA to dynamic field and economic impact and safety impact of boiler. The author focused on the relationship among the SA speed and the PA/SA on the furnace gas-solid mixing, the nuclear ring structure, gas and particle velocity, gas and particle concentration distribution, and relative erosion, and on this basis, analyzes the impact of the allocation of SA and distribution of the gas-solid mixture. Simulation results can provide theoretical reference for large-scale CFB boiler's design and operation.