Chemicals Based
Technologies - Removal of Hydrogen Sulfide from
Gas Streams
Introduction
A Netherlands based company through
its Indian associate is offering technology for removal
of hydrogen sulfide (H2S) from gas streams. A significant
number of scrubbers desulfurizing sour gas or biogas
are operated. In conjunction with shell global solutions
this process was demonstrated for the removal of H2S
from natural gas and syn-gases. In the process H2S is
absorbed and oxidized into elemental sulfur. The removal
efficiency of this biological method is very high at
low operational costs. H2S has to be removed for obvious
reasons.
Sulfides are:
Corrosive.
Malodorous, a smell like rotten
eggs.
Toxic, even at very low levels
it can cause headache and nausea.
Sulfur dioxide emission when the
gas is used as a fuel gas.
The process is flexible and has the
ability for high performance. An example is found in
the pulp and paper industry where mills, primarily driven
by environmental regulations, operate with zero discharge.
For closed water circuits it is important to prevent
the accumulation of organics and salts. The scrubber
is successfully used to desulfurize the produced biogas
and to remove any sulfate from the process cycle.
The combination of an anaerobic water
treatment system and a scrubber prevents accumulation
of both sulfate salts and organics and makes a zero
discharge process feasible. The gas enter a wet scrubber,
typically a packed column, and are desulfurized with
a slightly alkaline fluid. A demister section prevents
carry-over of fluid. The cleaned gases leave the scrubber
at the top.
The spent scrubber liquid is collected
in the bottom of the scrubber and directed to the bioreactor.
In the reactor air is dispersed at the bottom in order
to enable the biomass to convert the dissolved sulfide
into elemental sulfur, thereby regenerating caustic
soda. The sulfur is separated as a solid and the sulfur
slurry can optionally be pumped into a sulfur recovery
unit. In this unit the slurry can be dewatered and discharged
as a cake for further use. The liquor is returned to
the reactor. The bioreactor effluent is recycled to
the scrubber for renewed removal of H2S. From the system
a small bleed stream is taken in order to prevent any
built up of formed salts.
Areas of Application
Remove sulfur compounds from water,
air and gaseous streams. Environment Management
Advantages
Very high removal efficiencies
for hydrogen sulfide from process gases.
High biological activity, so that
peak loads and other variations in the production
processes are dealt with effectively.
Most odor causing components are
removed.
Short system start-up time.
Simple process control for stable
operation.
Operation at ambient or elevated
pressures, as well as at various temperatures.
Very low operational costs due
to recovery of caustic soda (>93% savings on caustic
soda use compared to caustic scrubbers for oxygen
free gas streams).
No need for discharge of sulfide
containing waste steam.
No need for use of chelating compounds
(chemical RedOx processes) and no subsequent production
of hazardous bleed streams.
Production of elemental sulfur
as re-usable by product.
Virtually no risk of clogging.
The same desulrurization principle
can be used for the removal of H2S from gases like biogas,
natural gas, gasification gases, process gases and (ventiliation)
air. Thus far, the process has successfully been applied
for biogas, refinery sour gas, natural gas and ventilation
air.
Stage of Development
Commercialised including in India
Economic Data
Will depend on application
Transfer Forms:Know-how,
Turnkey execution, Technical assistance
Main Application:
Chemical Industry
For further information please
contact :
Technology Bureau for Small Enterprises
APCTT Building, Qutub Institutional Area
P.O. Box - 4575
New Delhi - 110016
Tel: 91-26864501, 26856276, 2696619/521
Fax: 91-11-26856274
E-mail : tbse@apctt.org
Web: www.techsmall.com
