载体孔道密度对天然气催化燃烧的影响

制备了不同载体孔道密度的Pd/γ-Al_2O_3和六铝酸盐蜂窝催化剂,在自行设计的催化燃烧实验装置上进行了天然气催化燃烧实验。考察了载体孔道密度、空燃比和燃气流量对催化燃烧效果的影响。结果表明,载体孔道密度影响孔道内壁面反应和气相反应变化以及燃烧流体孔道内的流动及燃烧过程的传热传质,当载体孔道密度为200目时,流速减小,加强了气流与壁面上的浓度边界层中反应物质的交换,温度峰值增大,HC排放少;载体孔道密度为400目,气相反应减少,不会产生局部高温区,NO_x排放小。空燃比影响催化反应炉内各床层轴心温度以及炉内温度峰值的出现位置。随着燃气流量的增加,温度随之上升,1200℃以上时会产生较多的NO_x。

Effects of carrier cell density on catalytic combustion of natural gas

Pd/γ-Al2O3 and hexaaluminate honeycomb catalysts with different cell density were prepared and used as the catalyst for natural gas combustion in a self-designed combustion apparatus. Influence of cell density of the carriers, air/fuel ratio and fuel flow rate on catalytic combustion of natural gas was investigated. The experimental results showed that cell density of the carriers affected reactions on inner wall of the cells, flowing of the combustion stream through the cells and heat and mass transfer during the combustion, and hence of HC and NOx emission. Under cell density of 200 mesh, mass exchange between the gas flow and inner wall was increased due to lower flow rate, resulting in higher peak temperature and hence less HC emission; under cell density of 400 mesh, gaseous reactions was weakened and no local high temperature occurred, resulting in less NOx emission. Air/fuel ratio had influence on axial temperature of the catalyst layers and location where peak temperature appears. The bed temperature increased with flow rate of natural gas and more NOx formed when bed temperature exceeded 1 200 ℃.