Steam calcination of lime for CO2 capture

A process to achieve carbon capture from limestone calcination in a steam atmosphere generated by the combustion of hydrogen and oxygen has been developed and analysed. This process allows the capture of carbon dioxide by condensing the steam from the exhaust gases which avoids the need for the energy intensive step of separation of carbon dioxide from combustion products that is otherwise needed in conventional plants. These results are compared with a standard calcination cycle using fossil fuels with carbon dioxide capture based on oxyfuel combustion. A process model is used to estimate the capture efficiencies as being 98.6% for the carbon dioxide and 90.7% for the water, which can be recycled. This novel approach adds negligible energy cost except for the carbon dioxide compression unit which is an essential unit for all capture technologies. A techno-economic analysis of both processes, namely, steam calcination and natural gas with oxyfuel combustion, estimates that cost parity is achieved when the price of hydrogen reaches the range between US$1/kg – US$2/kg, relative to the current and projected price for natural gas. With hydrogen production costs projected to reach these values in the future, this approach appears to offer good potential once demonstrated at a reasonable scale. Furthermore, the cost of carbon dioxide transport and storage is estimated to be reduced by 23.9% for the steam calcination process, by avoiding the need to sequester any combustion products. •Steam calcination avoids energy-intensive CO2 separation.•Steam calcination has comparable capture efficiency to oxyfuel combustion.•Steam calcination is cheaper than oxy-fuel for H2 at cost-parity with natural gas.•Steam calcination delivers benefits owing to the lower reaction temperature in steam.