基于化学链燃烧的合成氨原料气脱碳过程的研究

The Decarburization of Raw Gas for Synthesizing Ammonia by Chemical-looping Combustion Technology

基于化学链燃烧的原理,利用固定床反应器,以铁触媒为催化剂和载氧剂,CaO为吸附剂,研究了化学链燃烧法净化合成氨原料气的可行性。系统考察了还原阶段CaO、汽气比、温度、CaO与铁触媒质量比等因素对原料气脱碳效果的影响,以及氧化阶段温度对铁触媒氧化和CaCO3热分解效果的影响。结果表明,在还原阶段,铁触媒既是CO变换反应的催化剂又是过程的载氧剂,而吸附剂CaO的存在,不仅能快速吸附CO2,而且能有效促进CO的变换反应,同步脱除CO和CO2,且适宜的还原条件为:汽气比8.0左右、温度500～550℃、CaO与铁触媒质量比3:1。在氧化反应阶段,当操作温度为800℃时,还原态的铁触媒Fe3O4可迅速被氧化为Fe2O3,CaO可完全再生,铁触媒的氧化反应热能有效促进CaCO3的热分解。

Based on the mechanism of chemical-looping-combustion（CLC）,the decarburization process of raw gas for synthesizing ammonia was investigated by using a fixed-bed reactor with the iron catalyst as catalyst and oxygen carrier,and the CaO as sorbent.The influence factors of reduction stage,such as steam to gas ratio,temperature,mass ratio of sorbent CaO to iron catalyst,on the decarburization of raw gas were studied;and at oxidation stage,the influence of temperature on the effects for the oxidation of iron catalyst and the decomposition of CaCO3 was also studied.The results show that,in the reduction stage,the iron catalyst can act as a catalyst for the shift reaction of CO as well as an oxygen carrier for CLC.It was found that the shift reaction of CO is so apparently promoted by adding sorbent CaO to rapidly adsorb CO2 produced from the shift reaction as to cause the CO and CO2 can be removed simultaneously.The appropriate conditions of reduction stage were determined as follows：the steam to gas ratio is 8.0,the temperature is 500～550℃ and the mass ratio of absorbent to iron catalyst is 3：1.In oxidation stage,when temperature is 800℃,the deoxidized iron catalyst Fe3O4 can be rapidly oxidized to Fe2O3,and the CaO is regenerated entirely.At the same time,the oxidation reaction heat of iron catalyst can effectively promote the thermal decomposition of CaCO3.