Pressure swing adsorption

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Category: Carbon capture (mature) Subcategory: Physical adsorption Combustion type: Post

DESCRIPTION

Pressure swing adsorption (PSA) is a cyclic adsorption and desorption process allowing continuous separation of gas streams. It is the most used technology based on adsorption at an industrial scale for CO₂ capture.¹ A PSA process may consist of several columns, steps, and different cycle times to achieve a certain performance. A basic PSA configuration has two beds and comprises four steps, namely pressurization using a compressor, CO₂ adsorption at high pressure, blowdown countercurrently by depressurization to atmospheric pressure, and purge using a portion of purified gas. Each PSA system uses specialised adsorbent materials such as zeolites, molecular sieves, activated carbon, etc. For a post-combustion process, zeolites are considered the natural candidates for a PSA process.² In the MAP-IT CCU project, pressure swing adsorption (PSA) is distinguished from other adsorption technologies by the assumption that the PSA feed operates at high pressure, while the PSA product stream is delivered at atmospheric pressure. In contrast, the vacuum swing adsorption (VSA) feed operates at atmospheric pressure , while the VSA product stream is delivered at vacuum pressures. More details on VSA are given in alternate processes section.

TECHNICAL ASPECTS (all % are volume-based)

Point sources: Iron and steel industry (blast furnace off-gases)³, steam-methane reforming³, cement and lime⁴, natural gas sweetening.⁵

CO₂ concentration range: min. 10%³

CO₂ capture efficiency: > 90%⁶, max. 99%⁴

CO₂ purity: 95%³

Min. feed gas pressure: 8 bar³

Max. feed gas temperature: 40 °C⁷

Typical scale: Small to Large (3,650 – 1,825,000 tCO₂/yr)⁴

Primary energy source: Electricity

Impurity tolerance: SOx = 10 ppm⁷

FUNCTION IN CCU VALUE CHAIN

Capture CO₂ from higher concentration flue gases.
Adsorbents such as zeolites are highly affected by the presence of water in feed gas, requiring an upstream dehydration step.⁸
Highly affected by flue gas impurities such as SOx and NOx, requiring appropriate pre-treatment steps.⁸

LIMITATIONS

High energy requirement due to feed gas compression, especially at lower CO₂ concentrations.
CO₂ purity is lower than the chemical absorption systems, likely requiring post-capture purification steps to achieve the high purities required in certain applications.
The physical size of PSA units can be quite large compared to the amine-based CO₂ scrubbers, which may not be feasible for all industrial applications.⁶
Adsorbent material may degrade over time, reducing overall capture efficiency.
Higher capital cost due to larger beds and longer cycle times.

ENERGY

Electricity is used by the compressor to pressurize the feed gas.

CONSUMABLES

Cooling water may be required to cool the feed gas after compression.
Adsorbents, in particular non-zeolite or carbon materials, have lifetimes of about 5 years and are replaced.
No chemicals are used.

Energy and Consumables
Parameter	Value
Electricity (kWh/tCO₂) *	210^a – 321^{b 9}
Cooling water (t/tCO₂)	-NA-
Adsorbent (kg/tCO₂)	-NA-
* Depends on feed pressure and CO₂ concentration, zero electricity if feed gas is already pressurized to the desired pressure. ^{a & b} 10 bar feed pressure with 20% CO₂. More information is given below in the COSTS section.

COSTS

CAPEX: 3^a – 4^b €/tCO₂ ⁹

Main CAPEX: adsorption column and compressor

OPEX: 23^a – 35^b €/tCO₂ ₉

Main OPEX: electricity and adsorbent

CO₂ capture cost: 26^a – 39^b €/tCO₂ ⁹

Depends on scale, CO₂ concentration, and purity requirements.

⁹ Cement plant; PSA two column configuration; CO₂ concentration – 20%; 8000 hr/yr; adsorption column lifetime – 10 yrs; adsorbent life – 5 yrs; interest rate – 5%; 2020 euros; electricity price – 110 €/MWh.

^a CO₂ capture capacity – 0.6 MtCO₂/yr; adsorbent – pillared clay; adsorbent price – 500 €/t; CO₂ purity – 76.6%; recovery – 72.1%.

^b CO₂ capture capacity – 0.42 MtCO₂/yr; adsorbent – zeolite 13X; adsorbent price – 1650 €/; CO₂ purity – 50%; recovery – 36.6%.

Note: Cost data on commercial adsorbents such as zeolite is not publicly available. The costs shown above are for the low-purity and low-recovery case. Higher purity and recovery are achievable by commercial PSA systems and thus will have higher CO₂ capture costs.

CO₂ avoidance cost: ±28 €/tCO₂ avoided ⁹ **

**same conditions as above but now with 6-column configuration; CO₂ purity – 78 %; recovery – 71.3 %.

ENVIRONMENTAL

CO₂ footprint: 128¹⁰ – 181¹¹ kgCO₂eq/tCO₂ captured (estimated for zeolites, 11-14% CO₂)

Spatial footprint: 13,320 m² for 4.6 MtCO₂/yr ⁶

Two-stage PSA process (first stage: 1 bar to 0.1 bar, second stage: 2 bar to 1 bar); includes only spatial footprint of columns, assuming maximum column diameter of 8m;⁶ depends on feed pressure and adsorbent capture capacity.

(MEA amine scrubber columns footprint = 674 m²) ⁶

Environmental issues: Disposal or recycling of spent adsorbents¹² (less issue than the solvents since zeolites have a lower environmental impact).

ENGINEERING

Maturity: Commercial (TRL 9)⁴

Proven technology.

Retrofittability: Feasible

Compatible with wide CO₂ concentration range; electricity is the only energy source; phased implementation due to modular nature; can be hybridized with other capture systems.^3,13

Challenges due to large spatial footprint requirements and effective pre-treatment steps are essential to handle impurities.

Scalability: High⁴

Well suited for capturing CO₂ at a wide capture rate range due to its modular nature.

Process type: Solid stationary adsorbent-based without chemical reactions.

Deployment model: Centralized only.

Each column with adsorbent undergoes cyclical CO₂ adsorption and desorption.

Technology flexibility: Hybridization with other capture technologies is feasible. It can be used to increase CO₂ concentration.

MAIN TECHNOLOGY PROVIDERS

HIPURE^® CC by LINDE, Ireland (PSA; 95% purity)
PolyCapture by PolyCapture, United Kingdom (PSA; polymer adsorbent; >95% purity)
CARBOGEN by ALLISON, United Kingdom (VPSA; 99.9% purity; OPEX <150 kWh/tCO2)
POLYBED™ PSA by HONEYWELL UOP, United States (Adsorbent)
CO2SORB by CO2CRC, Australia (Adsorbent)
MUF-16 by CAPTIVATE TECHNOLOGY, New Zealand (Adsorbent)
MOF-based VPSA by NUADA, Northern Ireland

ALTERNATE PROCESSES

Vacuum swing adsorption (VSA)¹⁴

VSA segregates CO₂ from flue gas at near ambient pressure; the process then swings to a vacuum to regenerate the adsorbent material. This configuration avoids the expensive and energy-intensive feed gas compression. However, a vacuum pump is required to maintain the required vacuum pressures during desorption.

Process: 6-step¹⁴ [4-step]¹⁵ VSA cycle with UTSA-16 MOF adsorbent.

Evacuation pressure: 0.2 bar¹⁴ [0.1 bar]¹⁵

Point sources: Iron and steel industry (blast furnace off-gases), steam-methane reforming¹⁵, coal-based power plant, integrated gasification combined cycle, cement and lime, (petro)chemical, oil and gas, natural gas sweetening.

CO₂ concentration: 15 mol.% (7.5%)¹⁴ [20%]¹⁵

CO₂ purity: 94.5% (93.9%)¹⁴ [95%]¹⁵

CO₂ capture efficiency: 91% (89%)¹⁴ [90%]¹⁵

Power: 174 (339)¹⁴ [300]¹⁵ kWh/tCO₂ captured.

CAPEX: 22 (47)¹⁴ [27]¹⁵ €/tCO₂

OPEX: 38 (73)¹⁴ [38]¹⁵ €/tCO₂

¹⁴ Electricity is ~34% of OPEX with price – 68 €/MWh, economic lifetime – 15 years, discount rate – 9%.

¹⁵ Electricity is ~34% of OPEX with price – 58 €/MWh, economic lifetime – 25 years, discount rate – 8%.

Technology providers: CarboPac-C by Bright, The Netherlands; VSA using MOFs by Nuada CO₂, UK.

Apart from alternate regeneration processes, new adsorbent materials and structures are currently being developed for pressure-based adsorption processes to achieve high CO₂ recovery and purity.

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

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3. Linde. HISORP CC - Adsorption-Based Carbon Capture and CO2 Recovery | A Linde Company. 2024

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

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9. Tingelinhas J, Saragoça C, Al Mohtar A, Mateus M, Pinto ML. Pillared Clays as Cost-Effective Adsorbents for Carbon Capture by Pressure Swing Adsorption Processes in the Cement Industry. Ind Eng Chem Res. 2023;62(13):5613-5623.

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Infosheet on Pressure Swing Adsorption