填充床介质阻挡放电脱除气化燃气中苯的研究

Experimental study on benzene removal of fuel gas in a packed-bed dielectric barrier discharge reactor

以生物质气化焦油典型组分——苯作为模型物,采用填充床介质阻挡放电(DBD)对气化燃气氛围中的苯进行脱除。考察了燃气组成、填充物种类、反应温度及催化剂还原方式对苯脱除的影响。结果表明,反应温度200℃时,空气气化燃气与水蒸气气化燃气氛围内的苯脱除率比较接近,但燃气中存在少量O_2会导致脱除率明显下降。并且,提高放电能量密度,使用高介电常数、高比表面积及孔容积的填充物能提高苯脱除率。采用传统还原和等离子体还原两种方式分别制得Ni/γ-Al_2O_3(C)、Ni/γ-Al_2O_3(P)催化剂,以Ni/γ-Al_2O_3(C)为DBD填充物,反应温度在230-330℃时,苯脱除率随温度升高而下降,330℃时达到最低脱除率11. 6%;温度高于330℃,苯脱除率随温度急剧上升且在430℃达到最大值85. 4%。等离子体还原可制得大比表面积及高分散性的Ni/γ-Al_2O_3(P),其苯脱除率随温度变化的趋势与Ni/γ-Al_2O_3(C)一致,但在430℃时达到更高的脱除率90. 0%。苯脱除过程中燃气的甲烷化可提高出口燃气中CH_4浓度,但燃气的热值略有下降。

A packed-bed dielectric barrier discharge(DBD)reactor was developed to investigate the removal of biomass tar in fuel gas atmosphere,and benzene was used as the tar surrogate.The effects of fuel gas composition,packing materials,reaction temperature and reduction methods of catalysts on the removal efficiency of benzene were investigated.The results indicate that the benzene removal efficiency of airgasification fuel gas is close to that of steam-gasification fuel gas at lowtemperatures,but the presence of O2 in the fuel gas leads to a large drop in the removal efficiency.In addition,the enhancement of the plasma discharge power and the use of packing materials with higher permittivity,specific surface area and pore volume can improve the benzene removal efficiency.For the plasma-catalytic process,the combination of DBD plasma and Ni/γ-Al2O3(C)shows a significant benzene removal potential.The benzene removal efficiency decreases with temperature from 230-330℃,reaching a minimum value of 11.6%,and then notably increases to 85.4%at430℃.Furthermore,the combination of plasma and Ni/γ-Al2O3(P),which is reduced by plasma under H2 atmosphere,has a similar tendency of benzene removal behavior within the temperature range of 230-430℃,reaching a maximum removal efficiency of 90.0%at 430℃due to higher specific surface area and nickel dispersion of Ni/γ-Al2O3(P).Moreover,the increased CH4 concentration induced by the methanation of the fuel gas and the slightly decreased heating value of the fuel gas are obtained in the plasma-catalytic process.