The limestone forced oxidation process (LSFO) is a wet process which can produce wallboard grade gypsum.  The process is based on the reaction bewteen a limestone suspension and the flue gases. Technologies and scrubber desingers intend to promote maximum gas-liquid surface area and residence time in order to perform high removal efficiencies (up to 99%).

The sulfur containing slurry is then oxidized to produce solid FGD-gypsum which is removed from the slurry by physical separation (filter, decanter...).

Large number of wet scrubber designs have been used in wet FGD systems, including spray towers (the most used), venturis, plate towers, and mobile packed beds. Because of scale buildup, plugging, or erosion, which affect FGD dependability and absorber efficiency, the trend is to use simple scrubbers such as spray towers instead of more complicated ones. The configuration of the tower may be vertical or horizontal, and flue gas can flow cocurrently, countercurrently, or crosscurrently with respect to the liquid. The chief drawback of spray towers is that they require a higher liquid-to-gas ratio requirement for equivalent SO₂ removal than other absorber designs.

Flowchart illustrates a LSFO system equipped with a traditionnal spray tower.

This process, as all FGD processes, has some advantages and disadvantages. As shown here under, all the reactions required by the process are done in the scrubber, the physical separation is the only step required outside the absorber.

Main advantages of LSFO process

Main disadvantages of LSFO process

See also: