Long-term pilot testing of the carbonate looping process in 1 MWth scale

Abstract

The carbonate looping (CaL) process is an efficient post-combustion carbon capture technology to reduce the amount of CO2 released by fossil fuelled power and industrial plants. This work presents the results gained in long-term pilot tests performed in a 1MWth CaL pilot plant at Technische Universität Darmstadt. The experimental data were obtained from continuous operation under realistic CaL process conditions, i.e. coal originated flue gas from a coal fired furnace to be decarbonized in the carbonator and oxy-fuel conditions in the calciner. Steady-state conditions, achieved while parameters were not changed during periods up to 60h, delivered reliable experimental data to scale up the CaL process to industrial size. The feasibility of the CaL process in semi-industrial size was proven by steady-state CO2 absorption for more than 1200h with absorption rates in the carbonator higher than 90% and overall capture rates higher than 95% under a wide range of operating parameters, e.g. type of fuel, flue gas composition or reactor temperatures. Exemplary operation to achieve steady-state conditions is presented to show the evolution of the carbonator absorption efficiency and solid properties, such as conversion from CaO to CaCO3 by carbonation and to CaSO4 by sulphation. The carbonator performance was assessed by reasonably closing the carbon balances and applying the active space time as a key parameter to interpret the trends observed.