Fixed-bed Reactor
Fixed-bed reactors have long been used in process industries. They contain catalyst, typically in pellet form, packed in a static bed. The syngas is then passed through the bed, where the reactions are induced as the gases contact the catalyst. Originally, fixed-bed reactors were the only commercially viable reactor type due to technological limitations. However, they also presented drawbacks mainly in the constraints existing in access to the catalyst material. Since the gas has to pass over the material the reaction is limited by the available surface area. This problem can be reduced by allowing more than one "bed" in the reactor for the gas to pass over, under, and/or through. The catalysts in fixed-bed reactors do not need to be as resilient, as they do not move in the bed. For the common situation encountered when a reaction process is exothermic, fixed-bed reactors demand cooling of the bed. If the excess heat is not dissipated from the reactor bed, it could eventually lead to deterioration and deactivation of the catalyst material. Fixed-bed reactors can be equipped with internal tubes where a heat transfer fluid, such as boiler feed water, can circulate inside the tubes to control the temperature rise in the reactor.