(141d) Uc Sulfur Recovery Process – An Integrated Multi-Contaminant Removal Process

The University of California
Sulfur Recovery Process (here after referred to as UCSRP-HP) testing addresses
the development of an integrated multi-contaminant removal process in which H₂S,
NH₃, HCl and heavy metals including Hg, As, Se and Cd present in a coal-derived
syngas are to be removed to parts-per-million (ppm) or in some cases
parts-per-billion (ppb) levels in a single process step. H₂S is
converted directly into elemental sulfur at 275^oF to 300^oF
and at the given sour gas pressure by reaction with sulfur dioxide in the
liquid phase. Prior to this, the other contaminates such as NH₃, HCl
and trace contaminants are removed in a separate section of the same reactor
column.  This is accomplished by the solvent absorbing H₂S, NH₃,
HCl  and trace metals from the feed gas.  NH₃ and HCl form a highly
soluble NH₄Cl salt and the absorbed heavy metals As, Cd and Hg
precipitate out as their very insoluble sulfides. The Se trace metal, present
in the syngas as H₂Se, forms a highly soluble (NH₄)₂Se
under these conditions and remains in the solvent.  The proposed process is
tightly integrated and is expected to be significantly more economical both in
terms of capital and operating costs because it replaces the sulfur removal
processes, acid-gas removal, Claus and SCOT, as well as the trace components
used or proposed in conventional schemes by one single unit.

This paper will include an  (i)
investigation of long-term (i.e., 1000 hrs) solvent stability by exposure of
the solvent to a simulated Illinois coal #6 gas containing all the contaminants
that may be present in the feed to UCSRP reactor, (ii) investigation of metal
corrosion related issues for selecting suitable material of construction for
UCSRP reactor, (iii)  investigation of the removal of the trace metal
components from the syngas by the selected solvent, (iv) development of an
Aspen-Plus based computer simulation model, and (v) techno-economic evaluation
of the process applied to syngas cleanup.