(188b) Removal of Hydrogen Sulfide in Coal Gases Using a Monolithic Catalyst Reactor

Removal of hydrogen sulfide (H₂S) from coal gas
and sulfur recovery as elemental sulfur are key steps in the development of
advanced power plants that employ coal and natural gas, and produce electric
power and clean transportation fuels.  The conventional method of sulfur
removal and recovery employing amine scrubbing, Claus, and tail-gas treatment
involves a number of steps and is energy intensive.  A novel process called
Single-Step Sulfur Recovery Process (SSRP) is under development at various research
groups. In this process, the H₂S in the coal gas is selectively
oxidized in a single step to elemental sulfur using sulfur dioxide (SO₂)
or oxygen (O₂) in the presence of alumina-or-carbon-based catalyst pellets
in a packed/fluidized bed.

A monolithic catalyst reactor (MCR) for the development of
a single-step sulfur recovery process is used to remove H₂S from a
simulated coal gas in this study. Sulfur dioxide is used as an oxidizer to
convert H₂S into liquid element sulfur at 125 to 155^oC.  The
monolith catalyst is wash-coated with gamma alumina oxide. A special flow
regime (Taylor flow) in a monolithic catalyst channel removes the liquid
elemental sulfur formed at the catalyst surface thereby regenerating the
catalyst in-situ, whereas catalyst pellets deactivated with liquid sulfur in a
packed/fluidized reactor are regenerated  periodically. 

The monolithic catalyst has the potential to convert
selectively H₂S to elemental sulfur by wetting the interface between
the solid catalyst surface and gas phase with a thin liquid sulfur film, which
is developed with the aid of a special flow pattern (Taylor flow) in parallel
catalyst channels.  A performance of the monolithic catalyst is presented in terms
of H₂S removal capacity, deactivation, and selectivity of COS with
various catalyst promoters at various reactor operation conditions.