Hydrogen Sulfide (H₂S) is an extremely potent, toxic, and dangerous gas that needs to be not only isolated but also removed from other gas and fluid streams. We have long faced the mammoth challenge of eradicating this harmful gas from the planet, which has prompted us to develop tools that can help accelerate the process.

The oil and Gas Industry is shifting its focus towards the production of sustainable, lower-emission clean fuels. This means that H₂S has to be limited or phased out.

What is Hydrogen Sulfide (H₂S)?

Hydrogen Sulfide is a fairly potent, colorless gas that has a pungent and distinct smell of rotten eggs. It is found naturally and released as a byproduct of some industrial operations as well. H₂S is naturally formed when organic substances start decaying.

It is found in multiple other environments, like agricultural waste, landfills, etc. H₂S forms an acidic solution when brought in contact with water. These acidic solutions bring about a multitude of problems for machines and personnel. 

Why is the removal of Hydrogen Sulfide from our environment important?

Hydrogen Sulfide is an extremely toxic and poisonous gas; even at low concentrations, it causes irreparable damage to man and machine alike, leading to safety and environmental hazards and loss of life as well. Some of the reasons are explained.

• H₂S, due to its toxic nature, irritates the eyes and causes breathing issues after unwarranted exposure, even at 5ppm, while inducing fatal effects around 1000-2000ppm.
• H₂S disrupts the heating capabilities of the fuels and gases and severely decapacitates the catalyst lifecycle, while in combination with water, it oxidises and causes rusting and corrosion in metal pipes and equipment.
• H₂S even creates a hindrance in the performance of machines, hugely impacting the quality and quantity of the product achieved.
• Every year, it costs billions in sewer assets losses to governments; it creates an immeasurable concern in terms of the safety and health of people working or even living in the vicinity of its disposal.
• Hydrogen Sulfide mixed with contaminated water is extremely harmful to natural cycles as well. This combination, when combusted, gives out sulfur dioxide and other harmful Sulfur components that are directly linked with acid rain.

What are the methods used for the removal of Hydrogen Sulfide?

Hydrogen Sulfide in any form of matter is dangerous for the survival of living beings around it. H₂S is mainly found or emitted from three key areas: water, indigenous or biogases, and natural and industrial gases. The removal processes for the above-mentioned disruptors are discussed below.

Water

Hydrogen Sulfide is mostly found in groundwater. Toxic and dangerous bacterial growth of sulfur has also been found in certain private water supplies that are known to make the water taste bad and cause stomach distress if consumed frequently. It is also to be noted that hot water disposal in houses can also sometimes give way to the growth of Sulfur Bacteria.

There are multiple processes to remove this harmful substance from our surroundings and household water bodies.

• Chlorination: Chlorine is an excellent deterrent to Hydrogen  Sulfide problems as chlorine reacts with sulfur to form compounds that do not react or give out foul odour in drinking water. It is also offered in automatic dispensing systems that can prevent future issues.
• Manganese filter: This specialised filter can mitigate all the harmful Sulfur contents owing to its special coating, which, once in the vicinity of Sulfur, reacts and forms solid Sulfur particles which are then separated with the help of a filter. This filter works in combination with greensand, which regenerates with Potassium permanganate after the Manganese is exhausted.
• Catalytic Carbon: It is an activated carbon that separates all the sulfur from the compounds with the help of oxidation. It can convert all the sulfur particles to neutral particles. It offers full control over oxidation, which allows users to manage the sulfur water.

Natural Gases and Industrial Excretions

Hydrogen Sulfide is obtained as a byproduct from a variety of industries. Stringent rules dictate that industries focus on greener and more sustainable efforts, thus making industries work on methods to mitigate the harmful and toxic effects of Hydrogen Sulfide in the environment.

Sulfur is a high-value raw material in a lot of industries; therefore, the industries are now focusing on removing and recovering the sulfur from these compounds so it can be reused and sold to the right buyers.

Industries are currently employing different processes to extract Sulfur from these harmful compounds:

• Chemical Absorption: industries make use of water rich in amines to absorb H₂S from the gas streams. When those gases are brought in contact with the amine in the water, it causes the H₂S molecules to attach to the amines. This is further separated and heated to remove amines and bring them back to use, while the H₂S that is left behind can be safely disposed of.
• Dry Scrubbing: This chemical process requires the gases to pass through particles coated with iron oxide. The iron immediately reacts with H₂S and forms a solid compound. This deposit of iron oxide and Hydrogen Sulfide mixed compounds is then frequently cleaned out after saturation. It is mostly installed in small-scale industries like natural gas treatment.
• Liquid Scrubbing: This process is used in industrial plants. This requires the gases containing H₂S to pass through a liquid that contains a high concentration of oxidising agents. These oxidizing agents react with sulfides and convert them into non-reactive and non-toxic compounds, which can later be collected and disposed of on demand.
• Sulfur Recovery: Gas treatment and other industries use this method to reuse and dispose of the collected H₂ The gas is partially heated in a furnace, and then it is passed through a certain reactor that houses the catalyst that reacts with the partially burnt H₂S gas to provide solid sulfur, which is then sold as a raw material

Indigenous Growth and Biogas

Indigenous growth comes from natural wetlands and geothermal geysers that produce a mild amount of Hydrogen Sulfide gas. Biogas is different from natural gas as it is not a fossil fuel; it is formed by the decaying foliage of plants, animal carcasses, manure, or sewage. Biogas gives out a substantial amount of Methane (CH4), which is highly sought after for electricity production.

There are multiple ways of dealing with the H₂S residue after methane. If it is in lower concentration, it can be brought down to 10ppm with the help of iron chloride and small doses of oxygen, while for exponential quantities, other neutralization methods are employed.

• Scrubbing: although this process is similar to that for natural gases but it makes use of different reacting agents to carry out the reaction. The H₂S present in the biogas reacts with the reagent and forms solid compounds that are later extracted and disposed of.
• Biofilters: This is an advanced biological method that relies on bringing in specific bacteria that feed upon H₂S gas as a source of energy. The gas is passed through a filter bed where the bacteria are induced that consume the H₂S gases. This is a fairly new process and requires a lot of critical conditions at all times, but it does offer a cost-effective and low-chemical-based approach