CO2 removal from Natural gas in Ammonia Plant

CO2 removal unit in Ammonia Plant

The raw material for the ammonia plant is natural gas. but unfortunately, many gas wells contain CO2 so that CO2 gas is very disturbing the process of making ammonia. In general, CO2 gas is discharged at the front of a factory or known as the front end process. Natural Gas will enter the CO2 removal unit. in this unit, an MDEA liquid will remove the CO2 gas from the natural gas stream.

CO2 removal unit from natural gas
CO2 removal unit from natural gas

In general, there are 2 high vessels or columns which are the core part of this CO2 removal unit. On the left side, that is yellow is a CO2 absorber vessel. The function of this vessel is to capture or absorb CO2 gas from Natural Gas then CO2 gas will be carried by MDEA solution. MDEA solution which is rich in CO2 gas is channeled to the green right vessel. Here, CO2 gas will be released or separated from the MDEA solution.

CO2 removal unit from natural gas
CO2 absorber

corrosion problem in CO2 removal unit

there are some common corrosion problem in this CO2 removal unit inside the equipment and outside the equipment. CO2 gas is corrosive and erosive. This will create corrosion-erosion in piping especially in the elbow area of CO2 gas piping. A regular inspection program need to be done to monitor this problem. CO2 in MDEA solution will create another problem. Piping contain CO2 rich MDEA solution will get corrosion from inside the pipe. This MDEA piping is insulated to maintain the heat of MDEA solution. this insulation will fail after 5 – 10 years operation and develop a serious corrosion under insulation outside the piping. A coating applied outside the piping will reduce the likelihood of this corrosion.

Inspection program in CO2 removal unit

the corrosion engineer and inspection engineer will work very hard to deal with the corrosion problem in this CO2 removal unit. Some suggested inspection are mentioned below:

  • UT thickness monitoring for MDEA rich solution pipe
  • UT thickness monitoring for CO2 gas pipe
  • Thermograph inspection for CO2 gas pipe especially for the elbow
  • Thermograph inspection for MDEA solution pipe to find corrosion under insulation location
  • the visual inspection inside the vessel

hope this information is useful to the engineering team and inspection team in dealing with CO2 removal unit. If you have any best practice in corrosion monitoring in this section, please share with us.

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