Axial Flow Reactor Internals
Axial flow pattern is an internals layout which allows the flow direction to be alongside the vessel axis. The active catalyst bed is filled in the vessel to a given height. The flow is crossing this total height before being collected. Flow can be either upwards or downwards. Alternate flow directions exist when the same catalyst is being regenerated with counter flow direction.
Vessel axis is generally vertical. However, horizontal reactors also feature similar internals with vertical flows and are part of the same group.
Support grids with beams assembly or outlet collectors are key components retaining catalyst and ceramic balls. Feed diffuser is ensuring flow spreading from inlet nozzle towards the catalyst bed. Other accessories are required for easy operation and handling.
Main Advantages
The main advantage of axial flow pattern is its versatility. To some extent, it can easily handle flow variations, in quantity and quality (two phases liquid and gas, high pressures and temperatures) as well as in direction. In two phase flow, liquid distributor trays ensure tight flow mixing, as well as quench mixing trays when temperature control requires quench injection. It can withstand high duty operation provided that the internals are designed to fit the purpose.
In upflow conditions, some provisions have to be taken in order to avoid bed fluidization and catalyst carryover to the downstream equipment.
Applications
Axial flow technology is applied by several process licensors and engineering companies: Badger, Shell, Haldor Topsoe, JGC, Axens, UOP, Chevron, Merichem, etc.
