Soot & Byproduct Removal

Particulate matter (PM) in the syngas stream is typically made up of ash, unreacted carbon char, and condensed chlorine and alkali compounds. The need for PM removal depends primarily on the downstream use of the syngas. For use in direct firing (boilers, HRSGs, thermal oxidizers, etc.), PM can generally be tolerated and is typically restricted by emissions limits (i.e. the effect on the exhaust gases emanating from the burner). The PM limits are progressively more stringent when the syngas is used for downstream conversion processes or for use in reciprocating engines and gas turbines. PM can be removed using various dry or wet PM removal systems.

Particulate removal processes include:

Syngas from pyrolysis reactors and gasifiers that operate at relatively low temperatures typically contain unreacted carbon in the form of tars. Tars comprise a wide spectrum of organic compounds, generally consisting of several aromatic rings. Tars have a tendency to deposit, forming sticky deposits in locations that can significantly impair equipment performance, and they are difficult to remove. Tars can be roughly grouped into “heavy” tars and “light” tars, and the method for removing them varies. Tar removal processes include:

The removal of mercury is often required in order to meet environmental permits limits when the syngas is combusted, as well as when the syngas must be purified for downstream systems that include sensitive catalysts or if the syngas will be converted to food substances, i.e. synthetic sweeteners. The standard for mercury removal from syngas is the use of sulfur-impregnated activated carbon. This technology has been proven with a wide range of gasifier types and syngas. Mercury removal typically occurs after PM and tar removal, and prior to sulfur and CO₂ removal.