Fourth stage cyclones are applied in the underflow from a third stage and are used to collect solids that have already been separated in the third stage. Solids separated in the third stage are transported to the fourth stage using a small percentage of the flue gas as the median for transportation of the catalyst, which is controlled by an orifice normally located downstream of the fourth stage cyclone. There are many different configurations for the underflow and fourth stage cyclone system, which must also be designed to accommodate unloading of the solids from the fines collection hopper. Our fourth stage cyclone systems, which are typically designed and fabricated to pressure vessel standards and are supported by the fines hopper vessel, have been supplied for many third stage separator systems.
