Van Tongeren offers third-stage cyclone systems complete with underflow lines and fourth-stage cyclones with lock out hopper arrangement.  These systems are employed in expander turbine protection. When an FCC uses an expander turbine to recover the power from the gases exiting the regenerator, a third-stage cyclone system must be placed upstream of the turbine to protect the blades against erosion from the fine catalyst particles present in the flue gas.

• Our systems use large-diameter high-efficiency tangential entry cyclones that are erosion resistant and not prone to plugging like smaller swirl-tube cyclones.
• Lower velocities result in lower pressure loss and reduced rates of erosion.
• Cyclones are generally located inside a pressure vessel that has an inlet plenum to distribute the gases and particles evenly between the cyclones and an outlet plenum to collect the cleaned gas.
• Collection efficiency on TSS is over 80% on particles 10 µm and larger
• An underflow system is frequently utilized to promote cooling of gas and transport catalyst prior to collection in the fourth stage cyclone
• Underflow uses only 2-3% of TSS gas flow to maximize power recovery from the expander turbine
• The fourth-stage cyclone is a high efficiency characteristic ASME (or other) code pressure vessel design used to remove the catalyst collected by the third stage from the underflow system.
• The fourth-stage cyclone is lined with thin-wall refractory for erosion resistance.
• A Lockout hopper system is employed under the fourth-stage cyclone to facilitate removal of the collected fines from the FCC.

Fourth-Stage Cyclones are designed as very high efficiency cyclones as they collect a concentrated load off most of the regenerator losses in 3% of the gas.  They work at substantially cooler temperatures than the third-stage cyclones due to the cooling the gas in the Van Tongeren design underflow pipe.  A lockout hopper system allows the fines to be removed while maintaining the underflow system at its operating pressure.

Catalyst hopper cyclones are used in catalyst handling service to offload fresh catalyst into storage hoppers, for removal of catalyst from the unit either during unit shut-down or for withdrawal of catalyst from the unit. These cyclones are used intermittently and are usually unlined small diameter units frequently designed as pressure vessels.