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How the CO2CRC aims to reduce the cost of capture

I recently had the pleasure of attending the annual CO2CRC symposium. When the CO2CRC commenced operating in 2003, it set itself an ambitious target to reduce the costs of capture by more than half. I used this opportunity to talk to some of the CO2CRC researchers on the progress against this target. There are three work packages that will need to come together to reach this target. The UNO technology, heat integration, and novel construction of units.

UNO Mk3

CO2CRC has patented a number of different variants of their UNO technology. This is a patented technology by CO2CRC that builds on the Benfields process commonly used for separating COfrom industrial gas streams. Currently, they are progressing with Mk3 of their patented technology. The main feature of this process is that it uses a potassium carbonate solvent system instead of an amine solvent system. Noted advantages of this system are:

  • low cost
  • low energy
  • environmentally benign
  • can remove other impurities like SOx and NOx
  • the potassium can be recycled from global carbon markets
  • can be used in both pre- and post-combustion applications.

Currently the CO2CRC assesses that their technology is at the Technical Readiness level of 4 and that this will proceed to level 5 when the pilot plant with a capacity of 1t COcaptured per day is commissioned in late 2012. They have an ambitious plan of scaling up this technology to levels 8 and 9 by the 2020-2025 time frame. This is a scale up of 5,000–12,500 times. Some of the challenges that need to be addressed at the pilot-scale facility include:

  • identifying suitable rate promoters to increase the absorption rate so that it is on par or better than amine based solvents
  • assessing the impacts of the solid that can be precipitated in the columns
  • demonstrating the lower energy requirement for regenerating the solvent.

Heat integration

The CO2CRC has completed a number of studies to develop more energy efficient ways of combining a capture plant into a power plant. These studies combine pinch analysis of hot gas streams from the power station and match these to the energy requirements for the capture plant. The research shows that the energy penalty can be reduced by diverting steam from the low pressure turbine to provide the heat required but also by increasing the temperature for the high pressure turbine which will increase the capacity of the plant. A lot of this work is about promoting energy efficiency within the power plant and integrating the heat flows between the capture plant and the power plant.

Improved construction

The CO2CRC has also developed concepts for reducing the capital cost of capture facilities. This work includes combining both an absorber and re-generator in a single unit and another option is to construct this equipment using concrete instead of steel. While these concepts have not been demonstrated for a capture facility, power stations are familiar with large concrete towers in the form of cooling towers. The research shows that these additional materials can reduce the capital costs.

Overall cost reductions

The CO2CRC has estimated the cost reductions from adopting these technologies and compared it to a basic MEA capture process. The 'waterfall' diagram below illustrates how the different technology improvements can make significant reductions to capture. The basis is that the MEA process incurs a cost of $120/ tonne COavoided and that this can be reduced to less than $40/ tonne COavoided. Capture cost reductions of this magnitude may be a game changer for CCS and bring forward commercial deployment.

Technology developers will likely maintain a watching brief on these developments and assist bringing them to market should they be able to address the technical challenges identified earlier.

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