Study On Erosion And Deposition Characteristics Of Heating Surface Based On Gas-Solid Two-Phase Flow

Coal is the main fossil energy source in China.Fly-ash particles entrained in the flue gas from boiler furnaces in coal-fired power plants or waste heat boiler can cause serious erosive wear on steel surfaces along the flow path,thereby reducing the operational life of the mild-steel heat transfer tube,which also lead to tube blast emergency of boilers.Fly ash deposition can increase thermal resistance and reduce heat transfer efficiency.Both of erosion and deposition are not conducive to safe,efficient and stable operation of the equipment.Based on a series of erosion and depositions models proposed by researchers,a simulation of erosion and deposition on heat transfer tubes caused by fly-ash particles entrained in the flue gas is studied to provide a certain reference for the boiler heating surface design and operation.The main work is as follows:1.Based on the Euler-Lagrangian discrete-phase model,a numerical model for the fly-ash particles entrained in the flue gas was established,including single-tube,aligned tube bundles,and novel aligned cross-flow heating surfaces.The wear and deposition model of each scholar summarized,a wear and deposition model suitable for convective heating surface is selected to be written into a user-defined function(UDF).2.The wear characteristics of the ash swept single tube and elliptical tube were numerically simulated.The simulation results were compared with the experimental and simulation results of other scholars to verify simulation accuracy.Differences in the wear characteristics of the two kinds of heat transfer tubes were compared at different flue gas flow rates and particle sizes.The particle collision and wear patterns along the circumferential direction of the heat transfer tubes were obtained.3.Based on the Tabakoff Erosion model,the wear characteristics of a new novel aligned cross-flow heating surfaces were analyzed.The flow and heat transfer characteristics of the heated surface obtained by numerical simulation are compared with experiments.Under the premise of accurate flow and heat transfer prediction,the maximum flow rate of flue gas and the average fly ash particle size under the operating conditions of the heated surface are investigated.Finally,corresponding anti-wear recommendations are put forward.4.Based on the deposition models of various scholars,the deposition characteristics of a single pipe and aligned arrangement bundles are simulated.The accuracy of heat transfer and flow model was verified by empirical equation.On the basis of that,the deposition characteristics of tube bundles under different flue gas velocity and particle size were investigated.