甲烷部分氧化制合成气反应中热点位置的研究

STUDY ON THE HOT SPOT IN PARTIAL OXIDATION OF METHANE TO PREPARE SYNTHETIC GAS

将热电偶插入La2 O3 Ni/MgAl2 O4 催化剂反应床层 ,通过移动热电偶详细考察了反应炉温、空速、原料气组成和加入水蒸气对甲烷部分氧化制合成气反应床层温升的影响。结果表明 ,反应热点位于催化剂床层入口处 ,而且热点位置不受上述反应因素的影响。但是 ,其温升值随空速的增大而升高 ,随反应炉温的升高而降低。反应中引入水蒸气可以降低反应热点的温度 ,但同时使产物中CO2 含量增大。根据反应热计算了燃烧重整机理和直接转化机理的绝热温升 ,与实验结果的对比表明 ,反应床层的温升主要来自于部分氧化反应的放热 ,即甲烷部分氧化制合成气可能是按直接转化机理进行的。极高空速时低甲烷转化率下合成气的选择性并未发生明显的变化 。

The hot spot of partial oxidation of methane to prepare synthetic gas were measured by moving the thermocouple in the catalyst bed during the reaction. It is found that the hot spot is at the point of catalyst bed inlet. The position of the hot spot is not affected by gas hourly space velocity (GHSV), oven temperature, the compostion of mixed gas with steam, but the temperature difference between the hot spot and the oven is strongly affected by these factors and increases with GHSV augment while it decreases with the increase of oven temperature. The added steam in the mixed gas can decrease the value of temperature difference between the hot spot and the oven and raise the yield of CO 2 significantly. The contrast of the adiabatic increase in temperature calculated with the measured values shows that the hot spot is mainly caused by direct oxidation of methane, and the reaction for partial oxidation of methane to prepare synthetic gas goes by direct oxidation mechanism. The high selectivity of CO and H 2 with lower conversion of CH 4 at extreme GHSV strongly supports the viewpoint of above conclusion.