Issues related to the use of activated carbon and defoamers in MDEA systems
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In the acid gas removal unit for syngas, the MDEA removal process is typically used. In this process, an activated carbon filter and a cartridge filter are installed ； During operation, an antifoaming agent needs to be added based on the tower pressure difference. I have the following questions for the experts: 1. What is the function of a activated carbon filter? Some descriptions state that it is “used to adsorb entrained hydrocarbons, amine degradation products, free iron, and antifoam agents”. It is also said that thermally stable amine salts can be removed. What I would like to ask is, what are hydrocarbons? Will the residual methane in syngas be adsorbed? What are the amine degradation products? How to determine if activated carbon has become ineffective (analysis of the solution composition before and after (which components should be analyzed? ), differential pressure trend monitoring? ） ； If activated carbon becomes ineffective, can it be reactivated online? How to activate? 2. The addition of defoamers is primarily based on the pressure difference in the absorption tower and desorption tower, as well as the trend of residual CO2 in the syngas. But is there a concentration requirement for each addition? For example, how many ppm. Furthermore, will the added antifoam degrade to form impurities in the system? Besides leading to significant loss of the defoamer, are there any other adverse effects from adding an excess amount?
The recommended addition level of defoamers is generally 10–50 ppm, as this amount is sufficient to control foam formation. When selecting a defoamer, it is important to consider its compatibility with the system, as the defoamer will remain in the MDEA absorption solution. Using an excessive amount of defoamer does not cause any adverse effects, provided that a product with good compatibility is chosen. Dow Chemical offers a product for this purpose; it is used in systems around the world, and many ammonia synthesis plants in China have adopted this product. Feel free to contact me if you need more information~