Hydrogen Sulfide Control

Hydrogen Sulphide (H2S) is commonly associated with the smell of rotten eggs. It’s a colourless, heavier-than-air, poisonous and corrosive gas.

 

Hydrogen sulphide is commonly created by bacterial decomposition of organic matter such as septic tank debris and faecal material. This process is conducted by sulphate-reducing bacteria (SRBs) in the absence of oxygen. In the presence of water, it is acidic and is known as hydrosulphuric acid. This is the cause of the corrosion in sour gas or sour oil processing equipment.

 

Hydrogen sulphide is lethal by inhalation at concentrations of 500ppm; it can quickly kill animals and humans at this concentration. The odor associated with hydrogen sulphide can be detected at concentrations as low as < 1 ppb. Hydrogen sulphide is an olfactory desensitizer, meaning that short exposure to even low concentrations of the gas stops your ability to smell the chemical.

H2S Control with FQE H2S Scavenger

 

FQE H2S is a water-based, proprietary polymeric product used for control of hydrogen sulphide. There are four critical issues associated with any H2S scavenger:

 

yellow-bulletRapid rate of reaction
yellow-bulletNon-reversible reaction path (no reversion to H2S)
yellow-bulletCost efficiency per mole of H2S
yellow-bulletPrevention of solids formation, specifically dithiazine

 

FQE H2S meets all above conditions. It efficiently works in both liquid and steam phases.

 

Due to the active materials, FQE H2S will not form insoluble solids. The reaction products are water soluble and are removed with the produced water. The customer will not have to routinely and mechanically clean plugged towers or pipelines when using our product.

 

The reaction of FQE H2S with Hydrogen Sulphide is nearly immediate and is non-reversible. It is advised that the client have good chemical dispersion equipment to optimize the use of the product. As with all competitive products, this is a contact dependent reaction.

 

Applications

 

This product has utility in refinery operations, oil and gas production, wastewater treatment operations and any industry where H2S is a concern.

FQE H2S is a water-based, proprietary polymeric that works nearly immediately, is non-reversible, and prevents the formation of hazardous solids in valves, pipelines, contactors, treater towers, and other essential equipment.

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Industry Practices

Alkaline Neutralization

Since H2S is acidic, one practice to remove the hazard and corrosive nature of Hydrogen Sulphide is through alkaline neutralization of the acidic protons present within H2S. This process is an effective, rapid method to negate the concerns of H2S and involves the formation of a salt. The reaction of forming a salt with many alkaline products such as caustic soda results in the possibility of the reversion of the salt to hydrogen sulphide gas under acidic pH conditions or in elevated temperatures. It is this reversion of the salt back to release hydrogen sulphide that makes neutralization an unacceptable process.

Metal Sulphide Formation

One inexpensive process for Hydrogen Sulphide removal from gas streams is to pass the gas through a bed of hydrated iron oxide. The iron (or a similar cation) will replace the hydrogen atoms in the H2S molecule to form a metallic sulphide and water. This is a common practice for packed, fixed-bed reactors where iron oxides are the standard metal used. While this is a cheap process, the packed beds must be replaced when the iron ceases to be active. The iron sulphide formed can be regenerated by flooding the iron sulphides with water and aerating the metal. This process produces elemental sulphur.

 

Note that the iron sulphide created in the packed beds can be pyrophoric and may create H2S if the metal is exposed to acidic pH conditions.

Aldehyde/Amine Reaction

Another common practice for the removal of H2S is through reaction with various amine or aldehyde compounds. Glyoxal (an aldehyde) is frequently used to control H2S. The advantage of the aldehyde reaction is that it can be completed under strong acidic pH conditions, where salt formation, metallic sulphide reaction, and most amine reactions will not be possible.

 

The disadvantage of the Glyoxal process is the high cost of Glyoxal and its slow rate of reaction with Hydrogen Sulphide. The reaction kinetics are such that the aldehydes can take a prolonged time to scavenge the H2S. This slow reaction time is detrimental and creates potential for safety hazards.

 

When it comes to amine reaction products, the industry currently uses many different type of amines. Most of the amine-type chemistries are either triazine-based or an alkanolamine product.

 

Alkanolamines like monoethanolamine (MEA) and diethanolamine (DEA) are the products used in the refinery Sulphur Reduction Units (SRU). Under the conditions of refinery application, H2S is converted to elemental sulphur. These products are also used in oil field gas production operations to mitigate H2S. They are functional, but less cost effective, as they only react on a single molar basis.

 

Triazine–based products are varied in their structures depending on the starting materials. They are functionally superior, because 2 moles of hydrogen sulphide can be controlled per mole of the chemical. However, in reaction with H2S, the triazine product typically forms an insoluble solid precipitate called dithiazine. This solid is the cause of much concern in the oil field, as the dithiazine particles plug valves, coat pipelines, contactors, and treater towers, stopping the flow. If this problem begins in pipelines and the deposits cannot be pigged out, it will eventually lead to pipeline replacement—at a very high cost.

 

Triazines are cheaply made and therefore are bordering on commodity products. As they are inexpensive, you will find them in everywhere in the oil field for H2S control.

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