Refrigeration based dehydration

DESCRIPTION

Refrigeration and condensation is a purification step in carbon capture processes aimed at removing water vapor from CO₂-rich gas streams to prevent water from freezing during the liquefaction phase.  In this process, the CO₂ stream at high pressure is cooled by reducing its pressure using a Joule-Thomson valve and a gas-to-gas heat exchanger. A knock-out drum is used to remove the water that may have condensed. The CO₂ gas is then passed through a Joule-Thomson valve, where the temperature is further reduced by reducing the pressure. Another knock-out drum is used to remove the rest of the water. The cooled CO₂ stream is passed through the gas-to-gas heat exchanger to cool the incoming hot and pressurized CO₂ stream.

REMOVED COMPONENTS

• Water vapor (H₂O) is the primary target component.

FUNCTION IN CCU VALUE CHAIN

• Purification – this is crucial to prevent corrosion and hydrate formation, which can block pipelines or damage equipment.
• Ensuring process efficiency – high purity CO₂ is required for many CCUS applications.
• Facilitating transport and storage to prevent water from freezing during the compression or liquefaction of CO₂.

LIMITATIONS

• Energy requirements due to cooling and compression of the gas stream.
• High capital costs, especially for multi-stage (large-scale) refrigerant systems.

ENERGY

• Electricity is used to power refrigeration compressors and cooling systems.

CONSUMABLES

• Refrigerants in a closed-loop system may need some make-up.

COSTS

Dehydration costs depend on the water concentration in the CO₂ stream. Higher water levels require more energy for purification, increasing overall costs.

Total purification cost: 2.7 – 4.8 €/tCO₂ ¹*

*includes both oxygen and water removal; lower range for coal-fired case and upper range for NGCC case; use CO₂ stream compositions from the table below to convert the values to per ton of water.

1 Oxygen limit – 10 ppmv; water limit – 50 ppmv; palladium catalyst cost – 600,000 €/m³; catalyst lifetime – 5 yrs; hydrogen – 23 €/kg; plant lifetime – 25 yrs; operating hours – 7446 hr/yr; discount factor 8%; CFR 0.0937; electricity price 38 €/MWh; cooling water price – 0.24 €/m³; 2012 euros.

TECHNOLOGY PROVIDERS

• Joule-Thomson effect gas conditioning modules by Flargent, Argentina
• Joule-Thomson system by GPR, United States
• Joule-Thomson plant for natural gas by CROFT, United States
• Joule Thomson skid package for natural gas by Rushton, Canada

ALTERNATIVE TECHNOLOGIES

• Absorption process: Water vapor is absorbed into a liquid desiccant, such as triethylene glycol (TEG). The saturated desiccant is then regenerated by heating to remove water and the TEG to be recycled.^2,3
• Adsorption process: This process uses solid adsorbents, such as zeolites, to adsorb water molecules. Regeneration is done by heat or pressure swing.^2,3

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.    Abbas Z, Mezher T, Abu-Zahra MRM. CO2 purification. Part II: Techno-economic evaluation of oxygen and water deep removal processes. Int J Greenh Gas Control. 2013;16:335-341.

2.    Abbas Z, Mezher T, Abu-Zahra MRM. CO2 purification. Part I: Purification requirement review and the selection of impurities deep removal technologies. Int J Greenh Gas Control. 2013;16:324-334.

3.    Bilsbak V. Conditioning of CO2 Coming from a CO2 Capture Process for Transport and Storage Purposes. Norwegian University of Science and Technology; 2009. http://www.diva-portal.org/smash/get/diva2:348870/FULLTEXT01.pdf