MEA based chemical absorption

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Category: Carbon capture (mature) Subcategory: Chemical absorption Combustion type: Post

DESCRIPTION

Primary amines for CO2 capture are most widely used for chemical absorption processes having one alkyl group on the nitrogen atom resulting in stoichiometry of 1:2  (the capture of 1 mole of CO2 requires 2 moles of amine). The most widely used primary amine is monoethanolamine (MEA) due to its commercial availability, relatively low cost, fast absorption rate, and rich experience in industrial applications. Due to its high viscosity and corrosive nature, a 30 wt.% aqueous MEA is generally used.1 Flue gas is cooled before feeding it to the absorption column where it reacts with the down-coming solvent. The rich solvent from the bottom is fed to the stripping column where the CO2 is liberated while the lean solvent is recycled to the absorption column after exchanging heat in the main heat exchanger.

MEA-based Chemical Absorption Process

TECHNICAL ASPECTS (all % are volume-based)

Point sources: Power generation, Cement production, Refineries, Iron and steel, Process heaters, Combined heat and power.

CO2 concentration range: 4-20%2 (typical)

CO2 capture efficiency: 95%3

CO2 purity: 99.8%1

Min. feed gas pressure: 1.1 bar

Max. feed gas temperature: 50 °C4

Typical scale: Large (> 1,000,000 tCO2/yr)

Primary energy source: Thermal (steam)

Impurity tolerance: NOx = 20 ppm, SOx = 10 ppm, O2 = minimum possible or use of O2 inhibitors.5

FUNCTION IN CCU VALUE CHAIN

  • Capture CO2 from flue gases.
  • Highly affected by flue gas impurities requiring several pre-treatment steps depending on the impurity.

LIMITATIONS

  • High energy requirement due to solvent regeneration
  • Solvent degradation in the presence of O2, SOx, and NOx
  • Equipment corrosion
  • Environmental impact due to solvent emissions
  • High CAPEX due to low CO2 loading resulting in large absorber size.

ENERGY

  • Steam is used in solvent regeneration and amine purification units.
  • Electricity is used in a blower to overcome the pressure drop in the absorption column and solvent pumping.

CONSUMABLES

  • Primary amine is used to capture CO2 from flue gas.
  • Cooling water is used in the stripping column to condense entrained water and solvent.
Energy and Consumables
Parameter Value (range)
Solvent make-up (kg/tCO2) 1.5 (0.5-3.1)6
Cooling water makeup (t/tCO2) 0.8 (0.5-1.8)6
Heat (GJ/tCO2) 3.37 – 3.88
Electricity (kWh/tCO2) 1927
7 FLUOR Economine FG Plus

COSTS

CAPEX: 4 - 8 €/tCO2*

Main CAPEX: absorption column, stripping column, and main heat exchanger.

OPEX: 61 - 66 €/tCO2*

Main OPEX: steam, electricity, cooling water, and amine make-up.

CO2 capture cost: 65 - 74 €/tCO2*

                                 35 – 58 €/tCO2 9

Depends on scale, CO2 concentration, flue gas pretreatment, amine purification, etc.

* VITO study in CAPTIN project; lower range - Coal power plant; 13 vol.%; 2.85 MtCO2/yr; upper range – NGCC; 4.6 vol.% CO2; 1.67 MtCO2/yr; electricity price = 100 €/MWh; steam price = 25 €/t; lifetime = 30 yrs; WACC = 4.1%, 2020 euros; excluding compression and purification. Please note that 20-25 years lifetime is more common for an industrial project.

9 Lower range – coal plant; upper range – NGCC; 2013 euros; excluding compression and purifications.

CO2 avoidance cost: 47 - 66 €/tCO2 avoided 9

                                       65-110 €/tCO2 avoided 10

9 Lower range – coal plant; upper range – NGCC; 2013 euros.

10 Cement plant; Electricity - 80 €/MWh; NG - 6 €/GJ; 0.8 MtCO2/yr; discount rate - 8%; lifetime - 25 yrs; including compression and purifications.

ENVIRONMENTAL

CO2 footprint: 232 kgCO2e/tCO2 11

Spatial footprint: 37,500 m2 (250x150) for 2.56 MtCO2/yr12 (including compression system)

Environmental issues: Solvent emissions, heat stable salt disposal1

ENGINEERING

Maturity: Commercial (TRL 9)

The most widely used method for CCS and CCU.13

Retrofittability: Challenging

CO2 avoidance cost for retrofit systems is generally higher than for new plants mainly due to the higher energy penalty resulting from less efficient heat integration, as well as site-specific difficulties typically encountered in retrofit applications.1

Scalability: High

Well suited for capturing large amounts of CO2 from large point sources.

Process type: Liquid solvent-based with chemical reactions.

Deployment model: Centralized or Decentralized.

Decentralized CO2 absorption at point sources with centralized desorption.

Technology flexibility: Hybridization with other capture technologies is feasible. Other technologies such as membranes or PSA can be used upstream to increase CO2 concentration.

TECHNOLOGY PROVIDERS

INNOVATIONS

MEA-based primary amine scrubbing technology serves as the benchmark for all CO2 capture technology due to its wider applications and high commercial readiness. Advancements are being made to reduce energy consumption and capture costs.

Vortex technology

Vortex reactor replacing scrubber and stripper to improve mass transfer during absorption and stripping. Reduction in absorber volume and subsequently in spatial footprint.

Aerosol reactor

Aerosol reactor replacing scrubber to improve mass transfer during absorption. Enables use of high concentration of solvents reducing the thermal energy consumption and equipment size.

CONTACT INFO

Mohammed Khan (mohammednazeer.khan@vito.be)

Miet Van Dael (miet.vandael@vito.be)

ACKNOWLEDGEMENT

This infosheet was prepared as part of the MAP-IT CCU project funded by VLAIO (grant no. HBC.2023.0544).

REFERENCES

1.    Rao AB, Rubin ES. A Technical, Economic, and Environmental Assessment of Amine-Based CO2 Capture Technology for Power Plant Greenhouse Gas Control. Environ Sci Technol. 2002;36:4467-4475.

2.    Maddox RN, Morgan DJ. Gas Conditioning and Processing. 4th ed. John M. Campbell and Company; 2006. Accessed April 11, 2022. https://books.google.ca/books/about/Gas_Conditioning_and_Processing.html?id=i6VLAAAACAAJ&redir_esc=y

3.    Barlow H, Shahi SSM. State of the Art: CCS Technologies 2024.; 2024.

4.    Wang M, Lawal A, Stephenson P, Sidders J, Ramshaw C. Post-combustion CO2 capture with chemical absorption: A state-of-the-art review. Chem Eng Res Des. 2011;89(9):1609-1624.

5.    Adams D. Flue Gas Treatment for CO2 Capture. IEA Clean Coal Centre; 2010.

6.    IECM. Amine-Based Post-Combustion CO2 Capture.; 2019. Accessed April 22, 2024. www.iecm-online.com

7.    Abu-Zahra MRM, Niederer JPM, Feron PHM, Versteeg GF. CO2 capture from power plants. Part II. A parametric study of the economical performance based on mono-ethanolamine. Int J Greenh Gas Control. 2007;1(2):135-142.

8.    Gorset O, Knudsen JN, Bade OM, Askestad I. Results from Testing of Aker Solutions Advanced Amine Solvents at CO2 Technology Centre Mongstad. Energy Procedia. 2014;63:6267-6280.

9.    Rubin ES, Davison JE, Herzog HJ. The cost of CO2 capture and storage. Int J Greenh Gas Control. 2015;40:378-400.

10.  IEAGHG. Deployment of CCS in the Cement Industry.; 2013.

11.  Grant T, Anderson C, Hooper B. Comparative life cycle assessment of potassium carbonate and monoethanolamine solvents for CO2 capture from post combustion flue gases. Int J Greenh Gas Control. 2014;28:35-44.

12.  IEA. Retrofit of CO2 Capture to Natural Gas Combined Cycle Power Plants.; 2005.

13.  Yamada H. Amine-based capture of CO2 for utilization and storage. Polym J 2020 531. 2020;53(1):93-102.

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