TABLE OF CONTENTS David E. Earls
Chevron Lummus Global
Richmond, California
In processing less expensive, high-metal feeds, the need for frequent catalyst change-outs can make conventional fixed-bed residuum hydrotreating technology uneconomical. Chevron Lummus Global (CLG) developed on-stream catalyst replacement (OCR) to remove metals from feed before it is hydrotreated in fixed-bed residuum desulfurization (RDS) units. The ability to add and withdraw catalyst from the high-pressure, moving-bed OCR reactor while it is onstream gives refiners the opportunity to process heavier, high-metal feeds or to achieve deeper desulfurization while maintaining fixed-bed run lengths and improving product properties.
Development of the OCR process started in 1979 as part of the research on new reactor concepts which might be applied to synthetic fuels and heavy oil upgrading. Most of these alternative fuels are difficult to upgrade to transportation fuels. Typically high in nitrogen, sulfur, and metals, they tend to deactivate catalyst very rapidly. Consequently, conventional fixed-bed hydrotreating processes can not upgrade these feedstocks economically. CLG determined that if fresh catalyst could be continually moved through a reactor, then catalytic activity could be maintained without shutting down the unit. Theoretically,...
