The hydrogen-rich gas stream produced in the isothermal reactor must be scrubbed to remove carbon monoxide and carbon dioxide, which would otherwise contaminate the ammonia synthesis catalyst. With LACTM.L1, this is achieved using another technology developed by Linde known as pressure swing adsorption. During this step, the gas stream is passed at high pressure through an adsorption material comprising, for example, a molecular sieve and active carbon. The material efficiently traps components such as CO, CO2
and any remaining methane from the natural gas. The hydrogen, however, passes through and flows on to the ammonia synthesis reaction. “The adsorption material has to be regenerated at regular intervals. To do this, we reduce the pressure in optimized cycles, allowing desorption of the gas molecules that have been retained,” explains Wawrzinek. In contrast, conventional processes require an energy-intensive CO2
scrubbing and another catalytic step (methanization) to reduce CO and CO2
to the required levels. “Our concept eliminates the need for three catalytic steps in total, which means it consumes around fifty percent less catalyst material than conventional processes,” says the Linde expert.