Well, the reaction needs a compressor, followed by a pipe reactor loaded with catalyst, followed by an expander, followed by an ammonia droplet seperator/conden

Well, the reaction needs a compressor, followed by a pipe reactor loaded with catalyst, followed by an expander, followed by an ammonia droplet seperator/condenser. That result is then fed back to the input along with more educts, and side-products are siphoned off slowly to prevent their accumulation. The expander is there because you increase the percentage of ammonia that will condense by both lowering the temperature and lowering the pressure, which an ideal expander is very good at. You'd prefer if that expander can power the compressor, with this setup being essentially a gas turbine with exhaust rebreathing and the combustion chamber replaced with a giant tube reactor filled with catalyst.