Chemical scavenging of hydrogen sulfide and mercaptans

Chemical scavenging of hydrogen sulfide and mercaptans

Keywords
Hydrogen sulfide, mercaptans, hydrogen sulfide scavengers, mercaptan scavengers
gas-liquid reaction engineering, gas solid reaction engineering, triazine H₂S scavengers, glyoxal H₂S scavengers.

Hydrogen sulfide (H₂S) and mercaptans are toxic and corrosive contaminants of natural gas and crude oil. For safe operation, it is important to remove these impurities. The impurities are often removed using processing methods where the chemicals are regenerated during operation. In other instances, chemicals that react with H₂S or mercaptan to form an irreversible reaction product are used. Both liquids and solids are applied to scavenge H₂S and mercaptans. Different contacting procedures are used to react scavengers with H₂S and mercaptans efficiently. Solid formation and inefficient mass transfer complicate the cost-effective removal of H₂S and mercaptans. There are several solutions to mitigate these complications. The best practices for cost-effective operation will be collected. New developments in the industry will then be presented along with the remaining challenges.

Natural gas sweetening

Keywords
Natural gas, hydrogen sulfide, carbon dioxide, Amine, adsorbent, membrane, sulfur recovery.

Natural gas can deliver cleaner energy than other fossil fuels, such as coal and liquid hydrocarbons, due to its lower CO₂ emissions per kWh. It is considered bridging energy from a time of high usage of fossil fuels toward a time where sustainable energies will be predominant. Natural gas has a major role to play in this transitional period by supplying a cheap high-density energy form, flexible to shave peaks in electricity demand, and complements intermittent sources, like those derived from solar and wind. Before being a feedstock or a fuel, natural gas must undergo several purification steps to remove contaminants, heavy hydrocarbons, and water. This chapter aims to provide an overview of one of these steps: the sweetening of sour natural gas. A sour natural gas refers to a natural gas that contains hydrogen sulfide (H₂S). In the oil and gas industry, natural gas is a mixture of alkanes or saturated hydrocarbons and various compounds that originates from a natural gas reservoir or is associated with crude oil production. The most stringent regulation within the natural gas processing applies to the sweetening process, which aims at removing all or part of the acid gases to satisfy the sales gas specification. Typically, the H₂S content shall be reduced to ≤4 ppm. CO₂ content is generally reduced by ≤3% such that the gas meets the required heating value. The stringent requirement for H₂S removal is derived from its toxicity and corrosiveness. After a review of the predominant technologies for H₂S removal and disposal, some of the developments for sour gas sweetening will be introduced along with the applicable technologies for CO₂ capture at gas plants.