Hydrocarbon Processing - December 2022 - 48

Process
Optimization
J. LEWIS, Worley Comprimo, Brentford, England, UK;
F. E. JENSEN, Topsoe, Lyngby, Denmark; and
H. NJUGUNA, Worley Comprimo, Brentford, England, UK
New state-of-the-art in sulfur recovery?-Part 1
It is widely accepted that state-of-theprocessa
based on proven technology,
art sulfur recovery technologies utilize
the modified Claus process as well as
some extension technology on the tail
gas. To achieve the highest sulfur recovery,
the extension technology converts all
tail gas sulfur species to hydrogen sulfide
(H2
S) by hydrogenation and hydrolysis,
which is subsequently captured in an
amine absorber and recycled to the Claus
thermal reactor. The industry has developed
amine solvents of increased H2
S
selectivity, with the most selective often
regarded as the best available technology.
One of the more interesting challenges
to the tail gas treatment technology described
above is the direct conversion to
sulfuric acid-after all, that is the destination
of much of the recovered sulfur.
However, the logistics of that approach
are complex, primarily with respect to
local sulfuric acid demand. Technically,
conversion to sulfuric acid can provide
better economics and decreased environmental
impact, if there are no transportation
restrictions.
Worley Comprimo and Topsoe have
developed a proprietary sulfur recovery
whereby sulfuric acid produced in a wet
gas sulfuric acid (WSA) tail gas treating
unit (TGTU) is recycled back to the Claus
thermal reactor. With fewer equipment
items and demonstrable high reliability,
coupled with an energy balance benefit
evidenced by operating plants and studies,
the new flow scheme challenges for
the position of best available technology.
A series of three articles presented
here and in two subsequent
Hydrocarbon Processing cover all aspects
of the technology. The first covers the
technological aspects and development,
while the second and third articles cover
environmental and economic aspects, respectively.
Case studies covering a range
of Claus plant acid gas feed streams are
used for the economic comparisons.
By way of introduction to the technology,
six key points of the sulfur recovery
processa
configuration should be stated:
* The WSA TGTU is robust
against variations in Claus tail
gas composition and can process
ammonia containing sour water
stripper (SWS) offgases, which can
be routed directly to the WSA unit.
* The equipment count is
lower than that in a Claus/
hydrogenation/hydrolysis/amine
configuration, and the Claus
plant equipment is smaller.
issues of
* The overall sulfur recovery is
equivalent to that achieved in a
Claus/hydrogenation/hydrolysis/
amine configuration, with sulfur
dioxide (SO2
150 mg/Nm3
) emissions of
, or whatever is
required at the location of the plant.
* Thermal efficiency is high
with high-pressure (HP) steam
exported from the WSA, and
little cooling is needed.
* There are no waste streams.
* No chemicals are required.
While the combined technology is
new, its components are well-established
in industry: the Claus process, the WSA
process and the handling of sulfuric acid.
Current industry trends include:
* Sulfur continues to be a
significant byproduct from
oil and gas upgrading
* Most new oil and gas fields are sour
* Tightening of sulfur emissions
standards will continue
* Operators are looking to reduce
their carbon footprint
* Operators are striving to
meet emissions standards at
minimum CAPEX and OPEX
with optimized technology.
Although sulfur is a product and conFIG.
1. Claus tail gas treatment options.
48 DECEMBER 2022 | HydrocarbonProcessing.com
tinues to be a significant byproduct from
oil and gas upgrading in both refining,
gas plants and various other processes,
it is-for many in the oil and gas industry-often
regarded as a waste product.
This is not going to change fundamen
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