甲烷化反应器催化剂积炭过程的模拟研究

Simulation of carbon deposition processes on catalysts in a methanation reactor

针对固定床甲烷化反应器内催化剂积炭问题,采用离散元方法(DEM)建立小管径比随机堆积球形催化剂床层,计算流体力学(CFD)方法模拟催化剂外层到内层的积炭形成过程,探讨入口氢气占比、温度、流速和催化剂温度对积炭的影响。结果表明:反应初期积碳最严重,0~4 000 s平均孔隙率值下降了0.34,4 000~8 000 s平均孔隙率值下降了0.075;从催化剂外层到内层,积炭程度呈圆环状减小;入口氢气占比从0~40%、催化剂温度从850~770K,催化剂平均孔隙率值增大0.27、0.22;入口流速从0.015~0.005 m·s^-1、温度从500~400 K,催化剂中心孔隙率值减小0.01、0.005。结论可为固定床反应器和甲烷化积炭效应研究提供参考。

A random stacked spherical catalyst bed with a small length-diameter ratio was created by a discrete element method(DEM) in order to solve carbon deposition problems in a fixed-bed methanation reactor.Computational fluid dynamics(CFD) was used to simulate the carbon formation process from the outer layer to the inner layer of the catalyst.The effects of hydrogen ratio,temperature,flow rate and catalyst temperature on carbon deposition were discussed.The results show that the most obvious carbon deposition happened at the beginning of reaction.From 0~4 000 s the average porosity value decreased by 0.34 and from 4 000~8 000 s the average porosity value decreased by 0.06.The degree of carbon deposition was in an annular shape from the outer layer to the inner layer.When the inlet hydrogen was from 0~40% and the catalyst temperature was from850~770 K,the catalyst average porosity was increased by 0.27 and 0.22.When the inlet flow rate was from0.015~0.005 m·s^-1 and temperature was from 500~400 K,the catalyst center porosity value was decreased by0.01 and 0.005.This study is helpful for the investigation of fixed-bed reactors and carbon deposition during methanation.