Ammonia reactor is a facility where synthesis gas at high pressure goes through individual layers of catalyser causing exothermic chemical reaction where a part of hydrogen and nitrogen reacts to ammonia. In the most contemporary ammonia reactors almost whole heat from the reaction is passed to the synthesis gas (adiabatic reactors).

„RAR-II“ labels a generation of upgraded Czechoslovak reactors which was designed and developed by ROEZ, s.r.o. company and which significant for its modularity. Design or replacement of the reactor has a possibility of choosing the number of catalytic layers, catalyser granularity, type of reactor cooling, type of flowing through catalytic layer as well as possibility emptying of the catalyser and other possibilities.