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In 2010, generation of electricity and heat were responsible for 41% of the world’s CO2 emissions. Amine scrubbing is a mature technology being adapted for capturing CO2 from combustion flue gas, but its high cost and environmental and health concerns leave the door open for viable alternatives. Dr. Arturo Macchi is leading a research team investigating two promising gas-solid technologies which show potential for sustainable, efficient CO2 capture when integrated into a single process: calcium looping (CaL) and chemical looping combustion (CLC).
CaL captures CO2 from a gas mixture using CaO (lime), followed by combustion of a gas or biomass by pure oxygen to supply heat, regenerating the sorbent and producing a concentrated CO2 stream. In CLC, a metal oxide such as CuO transfers oxygen from air to the fuel, releasing heat and producing a flue gas of concentrated CO2. If the heat generated by CLC could supply the energy needed for the regeneration step of CaL, the need to separate O2 from air is eliminated, and pure CO2 is produced.
CanmetENERGY showed the potential integration of CaL and CLC at lab scale, and their research forms the heart of this innovation. This project will clarify its technical and economic feasibility, focusing on the integrity of the solid material under realistic operating conditions and over hundreds of process cycles, optimizing CO2 capacity and minimizing sintering and attrition.
$500,000/3 years; Awarded 2012
Recent Canadian CO2 emission limits may present challenges for older coal-fired facilities and stimulate the adoption of new capture technologies if they can be implemented affordably. Integrated CaL-CLC can be retrofitted onto existing processes to potentially capture all CO2, significantly improving greenhouse gas and acid gas emissions from Canadian production of electricity. If biomass is regarded as CO2 neutral and is primarily exported, this approach may enhance CO2 credits via net reduction in anthropogenic CO2 production.
In addition to potential benefits for existing power production processes using combustion, CaL-CLC can be employed for high-yield hydrogen production via steam gasification of reactive fuels or steam-methane reforming, resulting as well in a purer CO2 stream for sequestration. Numerous industries can use this hydrogen, notably bitumen upgrading which is expected to require as much as 3 megatonnes per year by 2023.
CanmetENERGY pioneered experimental testing of the integrated CaL-CLC concept and is working with the project team on optimizing the sorbent material for high conversion and longer cycle life. The Canadian Clean Power Coalition, an association of electricity producers, has expressed support for CanmetENERGY’s research. Future partnerships may be useful in the development and implementation of the new technology.
The goal of this research is to investigate a novel integrated approach to CaL and CLC as a new class of CO2 capture processes using composite pellets containing CaO (lime) and CuO together with a binder such as calcium aluminate cement or bauxite. Specific objectives are to investigate various sorbent formulations and test their sustained CO2 capture capacity, with respect to conversion and attrition resistance, over multiple cycles in realistic gaseous environments and gas-solid contacting patterns. Reactor modelling and process simulation will indicate the process technical and economic feasibilities.
This project seeks to develop sorbents for pre- and post-combustion carbon capture processes as well as in sorbent-enhanced reforming at scales in-line with the feedstock fuel, although experimental and modelling work will be primarily directed towards post-combustion CO2 capture.
Preliminary experiments have shown that a CaO/CuO looping cycle potentially extends sorbent useful life and avoids the individual disadvantages of CaL and CLC, i.e., the relatively expensive and harsh sorbent regeneration conditions in CaL and the challenges to using solid fuels in CLC.