Postcombustion CO2 capture with CaO. Status of the technology and next steps towards large scale demonstration

AbstractPostcombustion CO2 capture using CaO requires a large scale circulating fluidized bed (CFB) reactor as CO2 absorber, operating between 600–700 °C. In addition, a large scale oxy-fired CFBC must be interconnected to this reactor to allow for the decomposition of CaCO3 formed in the carbonator. This allows for a continuous regeneration of the CaO sorbent and the production of a CO2 rich stream suitable for final purification and compression. Despite the known limitations associated to this technology (mainly sorbent deactivation, solid attrition, and high energy requirements in the calciner) clear operating windows have been identified at which the process could be implemented in practice using the know-how on CFBC technology. Theoretical studies on the thermal integration of a carbonation-calcination loop in new and existing power plants have shown that the technology has the potential to achieve a substantial reduction (around 30%) in capture cost and energy penalties with respect to stand-alone oxy-fired systems. Since the solid materials and operating conditions in the CFB units are similar to those present in existing large scale CFBCs, the prospects for a rapid scaling up of the technology are very promising. A rapid development is taking place in recent years by demonstrating the key concepts in laboratory scale test rigs of 10 s of kW. However, it is essential to move on to the next phase of pilot testing and validate the results in conditions fully comparable with those expected in large scale units. We describe here the design of a 1 MW th pilot plant to capture 70–95% of the CO2 contained in the flue gas from a 1/150 side stream emitted by an existing 50 MWe CFB power plant. The pilot is made up of two interconnected CFB reactors of 15 m height. The construction of the pilot has been initiated and is expected to enter into full operation in the first half of 2011, providing the necessary experimental results to decide on the launching of an aggressive development programme that aims to demonstrate the technology at large scale well before 2020