Sulfation rates of cycled CaO particles in the carbonator of a Ca‐looping cycle for postcombustion CO₂ capture

Abstract

in Wiley Online Library (wileyonlinelibrary.com).Calcium looping is an energy-efficient CO 2 capture technology that uses CaO as a regenerable sorbent. One of the advantages of Ca-looping compared with other postcombustion technologies is the possibility of operating with flue gases that have a high SO 2 content. However, experimental information on sulfation reaction rates of cycled particles in the conditions typical of a carbonator reactor is scarce. This work aims to define a semiempirical sulfation reaction model at particle level suitable for such reaction conditions. The pore blocking mechanism typically observed during the sulfation reaction of fresh calcined limestones is not observed in the case of highly cycled sorbents (N > 20) and the low values of sulfation conversion characteristic of the sorbent in the Ca-looping system. The random pore model is able to predict reasonably well, the CaO conversion to CaSO 4 taking into account the evolution of the pore structure during the calcination/carbonation cycles. The intrinsic reaction parameters derived for chemical and diffusion controlled regimes are in agreement with those found in the literature for sulfation in other systems.

Investigation of SO2 Capture in a Circulating Fluidized Bed Carbonator of a Ca Looping Cycle

“…Regarding the reaction term, we have shown in a previous work 32 that the layer of CaSO 4 is able to grow around the particle surface of cycled CaO without experiencing any geometrical restrictions for low conversion and that the sulfation conversion can be described adequately using a homogeneous model as the random pore model.…”

“…To determine k sulf ϕ SO2 only those points with an E Sulf CB below 1 were used. In order to calculate the value of ϕ SO2 , we employed a value of k sulf from the experimental data presented by Arias et al 32 for Compostilla limestone which has a value of 3.78 s -1 at a temperature of 630 ºC (average temperature for the experimental data obtained in this work). This yields a ϕ SO2 value of 0.85 which indicates that SO 2 capture in the carbonator in the presence of CO 2 is mainly controlled by the sulfation reaction rate of the particles in the bed.…”

Modelling of the kinetics of sulphation of CaO particles under CaL reactor conditions

“…The effect of the different variables on the sulphation rates in the CaL reactors have been studied previously [19,56,61,62], including an investigation of the sulphation of the purges from a pilot [19], with the samples being taken from the calciner of the CaL.…”

“…The structural parameters at different cycle numbers were calculated following a method similar to that presented in previous works [54,56]. This methodology allows the structural parameters of cycled sorbents to be estimated as a function of those corresponding to the fresh calcined limestone and the maximum CO 2 conversion after cycling.…”

“…One of the most widely used pore models is the model developed by Bhatia and Perlmutter [52,53]: the random pore model (RPM), which assumes that the particle is traversed by random size cylindrical pores with intersecting and overlapping surfaces as reaction proceeds. This model was applied successfully to gas solid reactions [54] including the carbonation and sulphation of CaO [33,[54][55][56][57].…”