Amine unit antifoam

Introduction

Chemicals that cause instability and break the formed foams are known as defoamers, foam suppressants, or anti-foams. These materials are used to prevent foam production in various industries. In the chemical industries, anti-foam (defoamer) is used in the production of paper, paint, food, textiles, and pharmaceuticals. In other industries, anti-foams are important additives in production processes. Anti-foams not only help eliminate foam formation on the surface but also improve processes such as filtration, washing, extraction, distillation, evaporation, dehydration, drying, and separation.

In the oil, gas, and petrochemical industries, the removal of acid gases is of high importance. These gases are usually separated using physical or chemical solvents in absorption towers through the absorption process. The most common alkanolamines used in the absorption process are:

• Diethylene glycol amine
• Methyl ethanol amine
• Diethanol amine
• Methyl diethanol amine

Anti-Foam in Gas Sweetening Units

In a gas sweetening unit, impurities such as carbon dioxide and hydrogen sulfide (referred to as acid gases or sour gases) must be removed from natural gas. These gases cause corrosion of pipelines and equipment, making it essential to separate them from natural gas. This separation process is carried out in absorption towers using solvents like alkanolamines (such as methyl ethanol amine, diethanol amine, and methyl diethanol amine). Each molecule of these amines contains at least one hydroxyl group and one amino group, which aid in the absorption of acid gases.

Problems of Foam Formation in Gas Sweetening Processes

One of the main challenges in gas sweetening using amine compounds is foam formation. Foam is defined as the dispersion of gas in a liquid such that the majority of the environment is filled with gas, and the liquid exists as very thin layers between gas bubbles. Some of the key factors contributing to foam formation include:

• Suspended solid particles in amine
• Presence of organic acids in the incoming sour gas stream
• Injection of corrosion inhibitors in gas wells
• Hydrocarbons dissolved in amine
• Degradation products of amine, such as thiosulfates and volatile acids
• Soap-based greases used in refinery valves

The occurrence of foaming in a gas sweetening unit can lead to various known problems, such as amine loss, filter element replacement, and unplanned shutdowns. These issues can significantly impact the operational efficiency of an industrial unit and, consequently, its revenue.

Solution: Use of Anti-Foam to Reduce Foam

To prevent the problems caused by foaming, continuous injection of anti-foam into the amine solvent is a common solution in refineries. This material effectively helps reduce foaming intensity and is capable of breaking and collapsing foam within a short period. The industrial research company Abrizan, utilizing scientific expertise and high-quality raw materials, has developed and designed an anti-foam agent based on block copolymers of polyether glycols. This anti-foam agent has high thermal stability, is easy to apply and dilute, and prevents the formation of residue while enhancing the gas separation process.

Conclusion

To prevent foam production and reduce foaming tendency, anti-foam is continuously injected into the circulating amine system. Anti-foams are generally mixtures of liquids and solid particles and are categorized based on their primary structure into the following groups:

• Non-polar oils:Mineral oils and silicones
• Polar oils:Fatty alcohols, fatty acids, alkyl amines, and alkyl amides
• Solid particles incompatible with water:Refined silica, aluminum oxide, and polypropylene

Factors such as solubility, droplet size, presence of water-incompatible particles, environmental forces, repeated foaming, chemical competition of components, surface concentration of materials, types of soluble salts, and their concentration can affect the performance and efficiency of the anti-foam.