An Experimental Study of Sulfur and Chlorine Stripping from Cement Hot Meal

This work explores the feasibility of developing a new process, as an alternative to the current bypass system, for stripping S, Cl and K from cement hot meal. Laboratory scale stripping experiments have been conducted in a horizontal tube reactor. The effect of the process conditions (gaseous atmosphere, temperature, time) on the removal of S, Cl and K from a cement hot meal collected from a full-scale plant has been investigated. It was hypothesized that sulfur removal can be enhanced in reducing conditions, by converting CaSO4(s) to SO2(g), while Cl (and K) removal is mainly due to evaporation of KCl. Experiments were carried out in the temperature range of 800 – 1100 °C and at residence times 10 – 60 minutes. The gaseous atmosphere used was either air, or 1 – 1.8% CH4 (with N2 for balance). During the experiments, a gas analyzer was used to monitor the release of SO2 during the sample conversion. After the experiments, the solid residues were collected and analyzed by, e.g., ICP-OES / IC for elemental composition, and XRD for determination of crystal phases. The experimental results revealed that a reducing atmosphere promotes the release of S from the hot meal. Substantial release of S (~40%), Cl (~40%) and K (~20%) from the hot meal was obtained at 900 °C, 30 minutes and 1% CH4 conditions. At higher temperatures, deviation of S release calculated from integration of SO2 and ICP-OES, respectively, indicated that other forms of sulfur (e.g. SO3 or H2S) released. Increasing the CH4 concentration from 1% to 1.8% slightly decreased S release from the hot meal at 900-1100 °C, probably due to over-reduction forming solid phase CaS(s)