Skip to main content

Acid Gas Treatment

Acid gas treating, also known as gas sweetening and sour gas treating, refers to a group of processes that use various aqueous solvents such as Amines, Hot Potassium Carbonate, Sodium Hydroxide etc, to remove hydrogen sulfide (high toxicity) and carbon dioxide (lack of heating value) from gases. It is a very common unit process used in Gas Processing plant, Refineries, petrochemical plants, Coal Fired Power Plant and other industries.

Principle Separation Technologies are listed below:

  • Solvent Separation
  • Adsorption
  • Membrane Separation
  • Cryogenic Distillation

Solvent Separation: Figure below shows a general schematic of the CO2 removal using a sorbent.  

Acid Gas Removal using amine treating

Solvent separation process uses liquid absorbent or solid sorbent. It consists two steps - the absorption step and the regeneration step. In the contactor vessel, the CO2 - containing gas is brought into contact with regenerated solvent which captures the CO2. The rich solvent, loaded with CO2, is then transported to a re-generator vessel, where CO2 is released after being heated. The re-generator sorbent is recycle back to the contactor to capture more CO2. A sorbent makeup stream is always required due to losses of water or degeneration of sorbent. Some of the processes, sorbent is not circulated between the contactor and re-generator because sorption and regeneration is achieved by the cyclic changes in the pressure or temperature in the vessel where the sorbent is contained.


The separation process is based on the reversible reaction between the CO2 and the sorbent. In the absorption, heat is released (exothermic) while in the regeneration the same amount of heat is added (endothermic) to revers the reaction.  Since the heat release occurs at lower temperature, this heat can be utilized. The consequence of this is that heat added to the re-generator at higher temperature is lost and causes a energy penalty. Lower the regeneration temperature, lower the energy penalty.

Some of the solvent separation processes are listed below:

  • Amine Process
  • Methanol Based Process
  • Hot Potassium Carbonate Solution (BenfieldTM process)

Adsorption: Adsorption is a process by which gaseous components are adsorbed on solids because of their molecular interactions to the solid surface.  The quantity of desired gas (e.g. H2S) adsorbed is directly proportional to the solid surface and due to this adsorbents are usually granular porous solids with large surface area. The following is a partial list of solid adsorbents used for acid gas removal:

  • Natural sorbents (e.g. clays)
  • Processed Sorbents (Silica, Zeolites, Molecular Sieves)
  • Coal, Char, and Carbon 

Following are the some of the solid adsorption processes:

  • Pressure Swing Adsorption (PSA)
  • Thermal Swing Adsorption (TSA)
  • Solid Scavenger Bed

Membrane Separation: The principle of membrane separation is based on solution-diffusion through a nonporous membranes. In this process, first feed gas dissolves to the membrane and then diffuses through it. Since acid gases (e.g. CO2, H2S) and water vapor permeate faster than the other constituents (e.g. CO, N2, CH4, C2H6) they get selectively removed. 

Note:This process is not based on the molecular wright since these membranes do not have any pores.

Figure below shows a general schematic of the CO2 removal using a membrane:  



Labels:

Comments

Post a Comment

Popular posts from this blog

Green Urea: A Sustainable and Eco-Friendly Fertilizer for Agriculture

Fertilizers are an essential component of modern agriculture, providing the nutrients necessary for plants to grow and produce high yields. However, the production of traditional fertilizers is often associated with significant environmental impacts, including greenhouse gas emissions and pollution of waterways and soil. Green urea is a new type of fertilizer that offers a more sustainable and eco-friendly alternative to traditional urea. What is Green Urea? Green urea is a type of fertilizer that is produced using renewable energy sources and sustainable production methods. Unlike traditional urea, which is primarily made from non-renewable fossil fuels, green urea is made using carbon dioxide captured from industrial emissions or directly from the atmosphere, and hydrogen generated from renewable energy sources such as solar, wind, or hydropower. The production process of green urea involves the electrochemical reduction of carbon dioxide to form carbon monoxide and hydrogen, followe
Post a Comment
Read more

Difference between the AEM and PEM electrolyzers

AEM (Anion Exchange Membrane) and PEM (Proton Exchange Membrane) electrolyzers are both types of electrolysis devices that use electricity to split water into its constituent parts, hydrogen and oxygen. However, there are some key differences between these two types of electrolyzers. Technical Difference The main technical difference between AEM (Anion Exchange Membrane) and PEM (Proton Exchange Membrane) electrolyzers lies in the type of membrane used and the resulting electrochemical reactions that occur. Membrane Material: AEM electrolyzers use an anion exchange membrane that selectively allows negatively charged ions (such as hydroxide ions) to pass through, while blocking positively charged ions (such as hydrogen ions). In contrast, PEM electrolyzers use a proton exchange membrane that selectively allows only positively charged ions (protons) to pass through. Electrolyte: AEM electrolyzers use an alkaline electrolyte (such as potassium hydroxide), while PEM electrolyzers use an a
Post a Comment
Read more

Haber-Bosch Process: List of Catalysts

The Haber-Bosch process is an important industrial process for the production of ammonia, which is used as a fertilizer and a key raw material for the production of various chemicals. The process involves the reaction of nitrogen gas and hydrogen gas in the presence of a catalyst to produce ammonia. Over the years, several catalysts have been developed for the Haber-Bosch process . In this article, we will discuss some of the most widely used catalysts for this process. Iron-Based Catalysts: Iron-based catalysts were the first catalysts used in the Haber-Bosch process and remain the most widely used today. These catalysts are typically composed of iron oxide (Fe 2 O 3 ) or iron carbide (Fe 3 C) supported on a high surface area material such as alumina. These catalysts typically operates at temperatures between 400°C and 550°C and pressures ranging from 150-300 bar. The feed gas, which consists of nitrogen and hydrogen, is introduced to the catalyst bed at a ratio of 1:3.  Iron-based c
Post a Comment
Read more