Traditionally reactors have used axial flow designs. This allows for simple design but as pressure drop is of some concern it can lead to large diameter vessels. Increasing the diameter of the reactor results in thicker walls and restricts the number of suppliers. Accordingly Johnson Matthey has developed alternative designs.
Axial flow Radial flow
Radial flow reactors have a much lower pressure drop and are less susceptible to fouling. The vessels have more complex internals but the vessel diameter is reduced. Contra-flow designs can be retrofitted into existing flow designs.