Fourth Stage System and Critical Orifice

The Cyclone Vessel, which is the common hopper for the cyclone catalyst discharge, is designed to hold the catalyst collected over several days. However, normally the catalyst from the Cyclone Vessel is continuously conveyed to the 4th Stage Cyclone by a small amount of gas, usually from 1 to 3% of the gases entering the cyclones.

During the travel through the uninsulated line and the 4th Stage Cyclone, a considerable amount of heat is lost from the catalyst and gases.

Additional cooling of the catalyst occurs in the Fines Collection Vessel. The gases from the 4th Stage Cyclone pass through a critical orifice where the gas pressure is reduced for discharge through the stack. When the Fines Collection Vessel is to be emptied into a closed truck for transport to a land fill, the valve above the vessel is closed, a vent valve is opened to relieve the pressure, and the valve beneath the vessel is opened so that the catalyst may discharge into the truck.