Membrane contactors are a hybrid technology that enable efficient carbon capture from industrial flue gas. Pilot plant trials were conducted at the Vales Point Power Station in NSW using the flue gas of the coal fired power plant.

Membrane gas-solvent contactor pilot plant trials at Vales Point Power Station

Membrane gas-solvent contactors are a hybrid technology in which traditional solvent absorption occurs within a membrane module. The technology involves the transfer of CO2 from the flue gas and through a hollow-fibre membrane, where it is chemically absorbed into the solvent. This takes advantage of the highly selective nature of solvent absorption technology, while the membrane acts to physically separate the solvent and gas phases. The process enables more CO2 to be quickly transferred into the solvent phase requiring significantly reduced equipment sizes when compared with conventional CO2 absorption systems using packed beds.

At the Vales Point power plant in NSW, the research team conducted a world’s first continuous pilot scale demonstration of capturing carbon dioxide using membrane gas-solvent contactor technology, while simultaneously undertaking carbon dioxide (CO2) capture and solvent regeneration.  The project clearly identified commercially available membrane contactors that can be successfully implemented for CO2 capture from flue gas using conventional solvents, as well as the subsequent solvent regeneration at elevated temperature.  The pilot plant campaign determined the optimal operational conditions, especially for solvent regeneration, that enabled efficient carbon capture operation over an extended period.

The membrane was designed to process 3 – 5 kg/hr of flue gas, utilizing 30 wt% MEA circulating with a flowrate of 0.1-0.12 L/min through both membrane contactors. Solvent regeneration was achieved through a steam sweep (2 – 5 kg/hr), that heated the solvent to high temperature as well as reduced the partial pressure of CO2 on the permeate side of the membrane, promoting CO2 liberation.

The research aims included:

  • Commissioning and trialling membrane contactor systems for solvent absorption from flue gas, utilising commercially available membrane modules.
  • Trialling membrane contactor systems for solvent regeneration, utilising commercially available membrane distillation modules.
  • Operation of the membrane contactor process in full continuous mode, with solvent absorption and regeneration occurring together for extended periods of time.
  • Achieving the performance of the pilot plant with overall mass transfer coefficient for absorption >0.08 cm/s and for regeneration >0.05 cm/s.
  • Detailed analysis of process performance to enable scale up design leading to future commercialisation of the membrane contactor process.

 

Resulting Publications

Scholes, C.A., S.E. Kentish, and A. Qader, Membrane gas-solvent contactor pilot plant trials for post-combustion CO2 capture. Separation and Purification Technology, 2020. 237: p. 116470.
Link to publication

Project Outcomes:

The trials exceeded the expected outcomes in terms of mass transfer coefficients, which relates to higher flux/permeability across membranes. Two successful campaigns on the pilot plant identified that poly-dimethyl siloxane {PDMS) based hollow fibre membrane modules, supplied by Airrane (South Korea), were the most suited for both absorption and regeneration process operations. This was due to the high overall CO2 mass transfer across the membrane achieved in both process operations, combined with the resilience of the membrane/module to process conditions. Critically, mass transfer performance targets for both process operations were achieved, when operating at higher solvent Reynolds Numbers. Performance also closely matched laboratory results, indicative of an optimized process. The solvent regeneration stage involved a steam sweep. It was determined that the steam flowrate control was critical to the overall process energy duty, as the steam provided the thermal energy to liberate CO2, but also crossed the membrane and diluted the MEA solvent.

This technology has the potential to be a cheaper option in carbon capture than the conventional technologies. However, further works are required before it can be adopted in commercial application including operating the pilot plant with the next generation of CO2 solvents which are more efficient and environmentally benign; increasing the throughput of the pilot plant to improve process efficiency and reduce thermal loss, as well as developing a solvent regeneration control scheme to better utilise the membrane module for both mass and energy transfer in the solvent regeneration process operation.

membrane_absorption
Schematic of the membrane gas-solvent absorption process

The technology combines the advantages of solvents and membranes to deliver a compact and potentially lower-cost carbon capture process.

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