One-dimensional model of entrained-flow carbonator for CO2 capture in cement kilns by calcium looping process

In this work, a 1D model of an entrained-flow carbonator of a Calcium looping process for cement plants is presented and the results of a sensitivity analysis on the main governing process parameters is discussed. Several design and operating parameters have been investigated through a wide sensitivity analysis, namely: adiabatic vs. cooled reactor, high gas velocity gooseneck reactor vs. low velocity downflow reactor, solid-to-gas ratio, sorbent capacity, reactor inlet temperature and solids recirculation. The effect of these design and process parameters on the CO2 capture efficiency and on Calcium looping process heat consumption is assessed.
The results of the calculations showed that with a proper combination of solid-to-gas ratio in the carbonator and sorbent carbonation capacity (e.g. about 10 kg/Nm3 and 20% respectively), carbonator CO2 capture efficiencies of about 80% (i.e. total cement kiln CO2 capture efficiencies higher than 90%) can be obtained in a gooseneck-type carbonator with a length compatible with industrial applications in cement kilns (about 120 to 140 m). Further experimental investigations on this reactor concept, especially about fluid-dynamic behavior and the chemical properties of raw meal as CO2 sorbent, are needed to demonstrate the technical feasibility of the proposed process.