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