FCC Gasoline Post-Treating

Sulfur Removal by Selective Adsorption. The ConocoPhillips S Zorb process uses selective adsorption to remove sulfur from FCC gasoline. The feed is combined with a small amount of hydrogen, heated, and injected into an expanded fluid-bed reactor, where a proprietary sorbent removes sulfur from the feed. A disengaging zone in the reactor removes suspended sorbent from the vapor, which exits the reactor as a low-sulfur stock suitable for gasoline blending. 

The sorbent is withdrawn continuously from the reactor and sent to the regenerator section, where the sulfur is removed as SO2 and sent to a sulfur recovery unit. The clean sorbent is reconditioned and returned to the reactor. The rate of sorbent circulation is controlled to help maintain the desired sulfur concentration in the product. 

Kerosene, jet fuel, and turbine fuel have similar boiling ranges. The key product properties are  

The flash point is the lowest temperature at which a liquid gives off enough vapor to ignite when an ignition source is present. The freezing point is especially important for jet aircraft, which fly at high altitudes where the outside temperature is very low. Sulfur content is a measure of corrosiveness. 

The measurement of smoke point goes back to the days when the primary use for kerosene was to fuel lamps. To get more light from a kerosene lamp, you could turn a little knob to adjust the wick. But if the flame got too high, it gave off smoke. Even today, per ASTM D1322, smoke point is the maximum height of flame that can be achieved with calibrated wick-fed lamp, using a wick of woven solid circular cotton of ordinary quality.  

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