Experimental investigation of the carbonation reactor in a tail-end Calcium Looping configuration for CO2 capture from cement plants

Abstract

The calcium looping process is a high temperature post-combustion CO2 capture technology that is expected to be especially suitable for cement plants. Both processes rely on CaCO3 as common feedstock, enabling the reutilisation of purged calcium looping sorbent in the cement clinker manufacturing process. Thus, setting new boundary conditions for the calcium looping process. So far, calcium looping CO2 capture has been demonstrated at semi industrial scale for fossil fuelled power plants but not yet for cement plants. In this work, results obtained from University of Stuttgart's 200 kW calcium looping pilot plant investigating the so called tail-end calcium looping cement plant integration are presented focusing on the carbonation reactor. Different integration levels between the cement plant and the calcium looping process were assessed investigating make-up ratios up to 0.9 mol mol−1 and CO2 concentrations up to 0.33 m3m−3. Operation at high sorbent make-up rates or high integration levels enhanced the sorbent's CO2 carrying capacity whereas for low integration levels the sorbent activity converged towards its residual CO2 carrying capacity. For high sorbent make-up flows, CO2 capture was limited by the carbonation equilibrium yielding CO2 capture rates as high as 98% in the carbonator at carbonation temperatures around 600 ∘C, whereas for low integration CO2 capture was limited by the active amount of CaO being fed to the carbonator. The active space time carbonator model was applied with satisfactory agreement to the conducted experiments indicating the model's validity for calcium looping CO2 capture from cement plant. The obtained results emphasise the suitability of calcium looping CO2 capture for the decarbonisation of the cement sector.