Hydrogen sulfide, removal

Process selectivity indicates the preference with which the process removes one acid gas component relative to or in preference to another. For example, some processes remove both hydrogen sulfide and carbon dioxide, whereas other processes are designed to remove hydrogen sulfide only. Thus it is important to consider the process selectivity for hydrogen sulfide removal compared to carbon dioxide removal, ie, the carbon dioxide-to-hydrogen sulfide ratio in the natural gas, in order to ensure minimal concentrations of these components in the product. 

One of the principal aspects of refinery gas cleanup is the removal of acid gas constituents, ie, carbon dioxide, CO2, and hydrogen sulfide, H2S. Treatment of natural gas to remove the acid gas constituents is most often accompHshed by contacting the natural gas with an alkaline solution. The most commonly used treating solutions are aqueous solutions of the ethanolamines or alkah carbonates. There are several hydrogen sulfide removal processes (29), most of which are followed by a Claus plant that produces elemental sulfur from the hydrogen sulfide. 

The simplest way of removing hydrogen sulfide is to scrub the hydrocarbon mixture with an aqueous solution of a strong base, such as sodium hydroxide. The hydroxide reacts with the HjS, which is a weak acid, and the hydrogen sulfide removal is quantitative even in a single contact stage. Spent caustic from this operation cannot be regenerated economically. 

Residual refinery gases, usually in more than one stream, which allows a degree of quality control, are treated for hydrogen sulfide removal, and gas sales are usually on a thermal content (calorific value, heating value) basis, with some adjustment for variation in the calorific value and hydrocarbon type (Rawlinson and Ward, 1973 McKetta, 1993 Speight, 1993 Johansen, 1998 Cranmore and Stanton, 2000). For fuel uses, gas as specified above presents little difficulty used... 

Figure 13 Chevron WWT process. Acid is used in first stage to enhance hydrogen sulfide removal. Caustic is used in second stage to enhance ammonia removal. (From Ref. 20.)...

T0341 Geo-Microbial Technologies, Inc., Hydrogen Sulfide Removal T0518 Met-Chem, Metal Kleen A... 

The Bio-FGD process converts sulfur dioxide to sulfur via wet reduction (10). The sulfur dioxide gas and an aqueous solution of sodium hydroxide are contacted in an absorber. The sodium hydroxide reacts with the sulfur dioxide to form sodium sulfite. A sulfate-reducing bacteria converts the sodium sulfite to hydrogen sulfide in an anaerobic biological reactor. In a second bioreactor, the hydrogen sulfide is converted to elemental sulfur by Thiobacilh. The sulfur from the aerobic second reactor is separated from the solution and processed as a sulfur cake or liquid. The process, developed by Paques BV and Hoogovens Technical Services Energy and Environment BV, can achieve 98% sulfur recovery. This process is similar to the Thiopaq Bioscrubber process for hydrogen sulfide removal offered by Paques. 

The char would be gasified under pressure with steam and oxygen, and the resulting gas after hydrogen sulfide removal would be used as raw material for the Fischer-Tropsch synthesis. 

High-Temperature Hydrogen Sulfide Removal Using a Regenerable Iron Oxide Sorbent... 

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