Kemija u Industriji (Sep 2013)
Reduction and Analysis of Low Temperature Shift Heterogeneous Catalyst for Water Gas Reaction in Ammonia Production
Abstract
In order to obtain additional quantities of hydrogen after the reforming reactions of natural gas and protect the ammonia synthesis catalyst, it is crucial to achieve and maintain maximum possible activity, selectivity and stability of the low temperature shift catalyst for conversion of water gas reaction during its lifetime. Whereas the heterogeneous catalyst comes in oxidized form, it is of the utmost importance to conduct the reduction procedure properly. The proper reduction procedure and continuous analysis of its performance would ensure the required activity, selectivity and stability throughout the catalyst’s service time. For the proper reduction procedure ofthe low temperature shift catalyst, in addition to process equipment, also necessary is a reliable and realistic system for temperature measurements, which will be effective for monitoring the exothermal temperature curves through all catalyst bed layers. For efficiency evaluation of low shift temperature catalyst reduction and its optimization, it is necessary to determine at regular time intervals the temperature approach to equilibrium and temperature profiles of individual layers by means of "S" and "die off" temperature exothermal curves. Based on the obtained data, the optimum inlet temperature could be determined, in order to maximally extend the service life of the heterogeneous catalyst as much as possible, and achieve the optimum equilibrium for conversion of the water gas. This paper presents the methodology for in situ reduction of the low temperature shift heterogeneous catalyst and the developed system for monitoring its individual layers to achieve the minimum possible content of carbon monoxide at the exit of the reactor. The developed system for temperature monitoring through heterogeneous catalyst layers provides the proper procedure for reduction and adjustment of optimum process working conditions for the catalyst by the continuous increase of reactor inlet temperature. The applied system provides maximum catalytic activity, selectivity and stability, as well as enables prediction of the catalyst's performance, which can be the basis for a proper decision on its timely replacement, and significant reduction of production costs.
