Because of their advantages of high efficiency and low cost,numerical research methods for large-scale circulating fluidized bed(CFB) apparatus are gaining ever more importance.This article presents a numerical study of gas-solid flow dynamics using the Eulerian granular multiphase model with a drag coefficient correction based on the energy-minimization multi-scale(EMMS) model.A three-dimensional,full-loop,time-dependent simulation of the hydrodynamics of a dense CFB apparatus is performed.The process parameters(e.g.,operating and initial conditions) are provided in accordance with the real experiment to enhance the accuracy of the simulation.The axial profiles of the averaged solid volume fractions and the solids flux at the outlet of the cyclone are in reasonable agreement with experimental data,thereby verifying the applicability of the mathematical and physical models.As a result,the streamline in the riser and standpipe as well as the solids distribution contours at the cross sections is analyzed.Computational fluid dynamics(CFD) serves as a basis for CFB modeling to help resolve certain issues long in dispute but difficult to address experimentally.The results of this study provide the basis of a general approach to describing dynamic simulations of gas-solid flows.
为确定燃烧解耦双流化床气化的气化反应条件和气化反应器的设计.在直径60 mm 和高700 mm的小型流化床反应器中,采用粒径8 mm 以下的锅炉烟煤以间歇气化方式在1133 K 的条件下,研究了进料方式、气化剂中水蒸汽和 O_2含量、以及煤料粒径等因素对煤气化生成燃气反应过程的影响.重点考察了各因素对煤转化速率的作用规律。综合各因素对 C 转化为燃气的速度、最大 C 转化率及生成气热值的影响趋势,确定了适宜的煤气化操作条件为:从流化颗粒表面附近加料.气化剂中 O_2体积分率5%、水蒸汽体积分率35%,煤粒径小于5 mm。在该条件下。实现60%的 C 转化为燃气所需要的停留时间大致为600 s。
