J.L. Ayastuy

Intercooled Double-Bed Reactor for LTWGS Reaction with Catalyst Poisoning by Chlorine: Inlet Temperatures for the Maximization of the Production

An intercooled double-bed reactor for industrial Low Temperature WGS reaction, subject to catalyst deactivation by irreversible chlorine chemisorption is modelled and optimised.Decline of the catalyst activity due to poisoning by chlorine decreases the reactor CO outlet conversion. After some time of operation, the lowest targeted CO conversion is reached, and further operation is inefficient. The reactor Efficient Production (EP) is calculated as the total amount of CO converted until the CO outlet conversion falls below the permissible minimum value, namely 0.85, which occurs at the operation time called the Catalyst Lifetime (CLT).Deactivation kinetics was assumed to be first order to chlorine partial pressure, and both the chlorine adsorption and deactivation rate constants were considered independent of temperature. For computation, spatio-temporal discretization of the reactor was adopted, and maximum CLT of 26 kh has been assumed.As the operation temperature is determining the overall reactor performance, two inlet temperature strategies for both reactors have been employed to maximise the EP: (a) isothermal and (b) time-trajectory.For a base case, optimum inlet isothermal temperatures for the first and second reactors of 483 and 458 K were found, respectively, at which 972.0 kmol of CO were converted within the CLT of 25.584 kh, being the EP of 958.6 kmol of CO. The maximum EP of 971.0 kmol was achieved for 483 and 462.3 K, for the first and second reactor, respectively. Varying the inlet temperature for both reactors along the time, higher production and EP were achieved.In comparison to the EP obtained for the single-bed reactor, the intercooled double-bed reactor allows to achieve higher EP, for both strategies.Also a sensitivity study to other operational variables, such as steam to gas ratio and total inlet flow, was carried out, in order to investigate their influence on optimal inlet temperatures.