Analyzing Various H2S Removal Methods on a Per Facility Basis

One of the most important aspects of ensuring hassle-free downstream and upstream operations is H2S scavenging. Also known as gas sweetening, there are actually several different methods of H2S removal. Natural gas is typically considered sour if it is found to contain large amounts of hydrogen sulfide, usually 4 parts per million or greater. Sour gas can result due to a number reasons, including the use of enhanced oil recovery methods, such as water injection, and the development of shale oil and gas plays. Significant concentrations of H2S can result in operational safety hazards in produced gas while also increasing the chance of sulfide-stress cracking and corrosion. This can result in lower value export gas. In order minimize such risks, a variety of H2S removal methods may be used.

Selecting an optimal strategy for H2S removal will depend upon a variety of factors, including residence time, H2S concentration, weight and space considerations, and volume of gas that needs to be treated. The selection of treatment strategies will also be based on operation conditions and the location of the application.

Solid scavengers are considered to be highly effective in terms of removing H2S from gas streams to only trace levels. Scavengers can be labor intensive, but they offer the benefit of predictable removal rates and usually do not require additional chemicals to be added. In addition, solid scavengers do not typically impact overboard water or downstream processes.

Liquid scavengers require less weight and space than solid scavengers, but are typically considered to be less efficient. The benefit of liquid scavengers is that they offer more flexibility and options when it is necessary to retrofit an existing facility.

Metal oxides involve the use of a fixed bed that is filled with absorbent metal oxide material, such as copper, zinc, magnesium, or iron. Space consideration is important with this option as the absorbent beds do take up a significant amount of space. Also, it is important to consider the fact that the media used in this method is non-regenerative. This system is known to be quite efficient in terms of H2S removal from gas streams. It is also highly predictable in terms of removal rates, change cycles, and reliability.

Regenerative solid beds are also sometimes referred to as molecular sieves. These beds remove hydrogen sulfide through adsorption rather than chemical reaction. Aluminosilcate crystalline polyers are used for stripping out compounds. It should be noted that this method will also remove water, CO2, sulfides, methanol, mercury, and ammonia to trace levels. This method is particularly effective in terms of removing contaminants. Additionally, the media can be regenerated through the use of a regeneration gas stream.

Although there are many H2S removal methods  available, the choice of the best method for individual facilities will involve analyzing space, demand, and facility considerations. Working with an experienced gas treatment facility can ensure the selection of a cost-effective, efficient, and reliable H2S removal method.