Removal of H2S and SO2 by CaCO3-Based Sorbents at High Pressure

The theoretical and experimental investigation of the mechanism of SO2 and H2S removal by CaCO3 -based sorbents (limestones and dolomites) in pressurized uidized-bed coal combustors (PFBC) and high pressure gasi#12;ers, respectively, is the main objective of this study. It is planned to carry out reactivity evolution experiments under simulated high pressure conditions or in high pressure thermogravimetric and, if needed, uidized- bed reactor (high pressure) arrangements. The pore structure of fresh, heat-treated, and half-calcined solids (dolomites) will be analyzed using a variety of methods. Our work will focus on limestones and dolomites whose reaction with SO2 or H2S under atmospheric conditions has been studied by us or other research groups in past studies. Several theoret- ical tools will be employed to analyze the obtained experimental data including a variable di#11;usivity shrinking-core model and models for di#11;usion, reaction, and structure evolution in chemically reacting porous solids. During the six months of this reporting period, work was primarily done on the study of the behavior of the sul#12;dation of limestones under sequential calcination conditions in the presence of small amounts of oxygen and the development of a stochastic simulation code for determining the extent of pore volume trapping (formation of inaccessible pore space) in gas-solid reactions accompanied by pore volume reduction such as the sulfation and sul#12;dation of calcined limestones and dolomites. The incentive for carrying out sul#12;dation experiments in the presence of oxygen was provided by the observation that some sul#12;dation experiments that were conducted as oxygen was accidentally leaking into the feed mixture of the reactor showed completely di#11;erent behavior from that obtained in the absence of oxygen. Experiments were carried out in the thermogravimetric analysis system that we developed for studying gas-solid reactions at atmospheric or subambient pressures. The two CaCO3 solids (Greer limestone and Iceland spar) that we employed in our previous experiments were used in the sulfidation