Hot potassium carbonate process

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

Description

The hot potassium carbonate (HPC) process is a widely used method for CO2 removal from gas streams. The process begins with sour gas entering an absorption column, where it contacts a lean potassium carbonate (K2CO3 at 20 - 30 wt.%1,2 often promoted by diethanolamine 3 wt.%)2 solvent. In this step, CO2 from the gas stream is absorbed by the solvent, forming potassium bicarbonate (KHCO3) and a sweet gas (CO2-lean gas) exiting the top of the column. The absorption column operates at temperatures between 40-120°C and pressures ranging from 20-60 bar.2 The CO2-rich solvent is then pumped to a flash drum (Flash Drum 1) to remove non-condensable gases and impurities. From the flash drum, the rich solvent is preheated and introduced into a stripping column after pressure reduction, suitable for stripping. In the stripping column, heat provided by the reboiler regenerates the solvent by releasing the absorbed CO2. The released CO2 rises to the top of the column, where it is cooled and condensed before being separated in another flash drum (Flash Drum 2). The separated CO2 is then sent for further use or storage. The regenerated lean solvent is recycled back to the absorption column for reuse, maintaining a continuous cycle.

Hot Potassium Carbonate Process

TECHNICAL ASPECTS (all % are volume-based)

Point sources: Power, Steel, Cement, Refining & Petrochemical, Waste to Energy, BECCS, Pulp & Paper, Gas Processing, & Industrial Flue Gases.3

CO2 concentration range: >5%3

CO2 capture efficiency: 80-95%3

CO2 purity: 99%3

Min. feed gas pressure: 20 bar2

Max. feed gas temperature: 120 °C2

Typical scale: Large (> 100,000 tCO2/yr)4

Primary energy source: Thermal (steam) and electricity

Impurity tolerance: Solvents will absorb impurities such as NOx, SOx, and mercury, and form stable salts, resulting in near zero emissions (<100 ppm).5

FUNCTION IN CCU VALUE CHAIN

  • Capture CO2 from flue gases.
  • Removal of H2S, avoiding any additional purification step.
  • SOx and NOx form potassium salts when reacted with K2CO3, which are easily recoverable, avoiding the use the additional flue gas pretreatment steps.

LIMITATIONS

  • High energy consumption due to the regeneration step
  • HPC absorbs CO2 slowly, requiring large absorption columns. Additives help, but don't reduce the size significantly. Increasing CO2 partial pressure can improve efficiency but adds energy-intensive turbomachinery.6
  • Requires pressurized flue gas.
  • Corrosion and solvent degradation issues over time due to impurities.

ENERGY

  • Heat (steam) is primarily used for the regeneration of the solvent in the stripping column.
  • Electricity is mainly used for pumping, fans, and control systems.

CONSUMABLES

  • Potassium Carbonate (K2CO3) is the primary solvent used in the absorption column to capture CO2.
  • Water for preparing the potassium carbonate solution and for controlling the concentration of the solvent.
  • Steam is used in the regeneration step.
Energy and Consumables
Parameter Value
Heat (GJ/tCO2) 2.177 – 2.55
Electricity (kWh/tCO2) 7707
Cooling water (t/tCO2) 34.57 *
K2CO3 make-up (kg/tCO2) 0.128

7 solvent conc. - 40 wt.%; CO2 conc. – 30 %; CO2 capture efficiency – 87%; includes only flue gas compression to 10 bar; excludes CO2 compression.

5 UNO MK 2 technology.

* Cooling water is reused.

COSTS

CAPEX: 24 €/tCO2 9

Main CAPEX: absorption column, strippers, and heat exchanger.

OPEX:  60 €/tCO2 9

Main OPEX: electricity, fixed OPEX.

CO2 capture cost: 84 €/tCO2 9

                                55 €/tCO2 7

CO2 avoidance cost: 104 €/tCO2 avoided9

9 CO2 Capsol technology; CO2 conc. – 5%; CO2 capture efficiency – 85%; 1.92 Mt/yr; operating hours – 7446 hr/yr; 2025 euros; discount rate – 7.8%; lifetime – 25 yrs; electricity – 162 €/MWh; steam – 18 €/MWh; steam for regeneration produced by heat recovery; cost includes flue gas cooling, compression to 9 bar, CO2 capture, compression to 101 bar and purification; 39% share in CAPEX for capture technology.

7 Solvent conc. - 40 wt.%; CO2 conc. – 30 %; CO2 capture efficiency – 87%; includes only flue gas compression to 10 bar; excludes CO2 compression; K2CO3 – 1235 €/t; cooling water – 0.012 €/t; electricity – 47.8 €/MWh.

ENVIRONMENTAL

CO2 footprint: 152 kgCO2e/tCO2 8

(dependent on electricity source, for NGCC electricity = 60 kg CO2e/tCO2)

Spatial footprint: 11,719 m2 for 1.92 MtCO2/yr 9

(land cost – 25.6 €/m2; estimation includes flue gas cooling, compression, CO2 capture, compression and purification)

Environmental issues: Water usage for the aqueous solution, waste disposal.

ENGINEERING

Maturity: Commercial (TRL 9)3

Commercial plants are operational globally.

Retrofittability: Feasible

Compatibility with existing infrastructure that already handles flue gas streams, such as hydrogen production plants, refineries, ammonia synthesis plants, and natural gas processing facilities.

Scalability: High

Suitable for a wide range of industrial applications, particularly for medium to large-scale plants.

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, can be used upstream to increase CO2 concentration.

INNOVATIONS

  • Enzymatic Carbon Capture: Enzymatic carbon capture technology by CO2 Solutionsᵀᴹ (Saipem) efficiently reduces CO2 emissions, meeting regulatory standards. It operates using low-grade residual heat at 85°C, integrating easily with waste heat sources to save costs and minimize environmental impact. The technology uses a non-toxic carbonate solvent, producing minimal hazardous byproducts, ensuring environmental safety.
  • Heat integration: Capsol’s integrated post-combustion carbon capture and heat recovery system uses the efficient and safe HPC (Hot Potassium Carbonate) solvent, simplifying permitting. It is ideal for sectors like cement, biomass, energy-from-waste, and gas turbines.

TECHNOLOGY PROVIDERS

  • Benfield™ by Honeywell, United States.
  • Hot Potassium Carbonate by Sumitomo SHI FW, Finland.
  • UNO MK 3 by KC8 Capture Technologies, Australia (Regeneration energy 2 – 2.5 GJ/tCO2)
  • CapsolEoP® by Capsol Technologies, Norway (Regeneration energy 0.6 – 1.9 GJ/ton CO2 for CO2 concentration 4 – 20%10; 95% capture efficiency; 35 €/tCO2 capture cost; can be fully electric)
  • Hot Potassium Carbonate by K2-CO2, Italy
  • CATACARB® HPC by Andritz AG, Austria (Absorption temperature 80 – 100 °C; 90% capture efficiency; >99% purity)
  • Enzymatic Carbon Capture by SAIPEM, Italy.

BENCHMARK

MEA-based primary amine scrubbing technology serves as the benchmark for all the CO2 capture technology due to its wider applications and high commercial readiness.

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.    Al Rashid MR, Bousmaha B. Operating Experience Of The Benfield Carbon Dioxide Removal System At Ruwais Fertilizer Industries (FERTIL). In: IFA Technical Conference. ; 2004. Accessed February 29, 2024. https://ureaknowhow.com/wp-content/uploads/2014/03/2004-Rashid-Fertil-IFA-Operational-experience-of-the-benfield-CO2-removal-system.pdf

2.    Ngu LWW, Mahmoud A, Sunarso J. Aspen Plus simulation-based parametric study of Benfield process using hot potassium carbonate promoted by diethanolamine. IOP Conf Ser Mater Sci Eng. 2020;778(1).

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

4.    Menmuir D, Florence S, Taylor K. Next Generation Carbon Capture Technology Technology Review.; 2022. Accessed February 17, 2025. https://assets.publishing.service.gov.uk/media/629493dbe90e070396c9f6a0/aecom-next-gen-carbon-capture-technology-technology-review-annex-1.pdf

5.    Anderson C, Harkin T, Ho M, et al. Developments in the CO2CRC UNO MK 3 Process: A Multi-component Solvent Process for Large Scale CO2 Capture. Energy Procedia. 2013;37:225-232.

6.    Navedkhan M, Lakshminarayan J, Biliyok C, Levihn F. Integration of Hot Potassium Carbonate CO 2 Capture Process to a Combined Heat and Power Plant at Värtaverket. In: International Conference on Greenhouse Gas Control Technologies. GHGT; 2022.

7.    Chuenphan T, Yurata T, Sema T, Chalermsinsuwan B. Techno-economic sensitivity analysis for optimization of carbon dioxide capture process by potassium carbonate solution. Energy. 2022;254:124290.

8.    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.

9.    Menmuir D, Berry K. Next Generation Carbon Capture Technology Technoeconomic Analysis.; 2022. Accessed February 17, 2025. https://assets.publishing.service.gov.uk/media/6294923ce90e07039e31b777/aecom-next-gen-carbon-capture-technology-technoeconomic-analysis.pdf

10.  Staggat P. Cost-effective Carbon Capture through HPC technology licenses. In: Rotterdam Conference. ; 2023. Accessed February 17, 2025. https://fortesmedia.com/files/files/Doc_Pack/Industry_CCUS_2023/Rotterdam_Conference_Presentation_v1.pdf

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