Suppression of Natural Limestones Deactivation During Cyclic Carbonation
Abstract The paper reviews sorption properties of limestones with varied levels of calcium carbonate. The sorption capacities change in cyclic calcinations as well as carbonations were studied using a laboratory apparatus with vertical quartz reactor. The use of suitable limestones and conditions of processing provided the capacity to last for that could reach 11kg CO2 per 100 kg limestone. Methods of reactivation of waste limestone using a gas saturated by water vapor was suggested to eliminate decreasing of the capacity of the carbonate looping process. I. INTRODUCTION This study focuses on the utilization of limestones for high temperature separation of CO2 from flue gases within the carbonate looping technique. Post-combustion combustion capture of CO2 from coal-fired power plants and district heat-plants was thought to be the most appropriate application for carbonate looping. A simplified scheme of the process, based on research literature [1], is illustrated in Fig. 1. For more detail please visit>>> Carbonate looping, though yet to be incorporated into industrial use but there are a few pilot units operated around the globe. Alonso et al. presented the main findings of the operation of the pilot plant that utilized CaO looping, which was integrated into the facility that combusts biomass within a fluidized bed reactor]. Utilization of CaO -based sorbents for the separation of CO2 at high temperatures by industrial processes is the focus of relatively many studies. Their economic accessibility and affordability of materials makes them attractive candidates for solving problems with suppression of CO2 emissions into the atmospheric air. A major hurdle to the application of CaO-based sorbents within the industrial context is a slow decline in capacity of sorption. This is manifested by the repeated cycles of the process of calcination (i.e. the process of thermal carbonation) along with carbonation. Based on experimental data Abanades proposed an equation (1) that describes the relationship of the conversion from CaO to CaCO3 depending on how many cycles are in the process [3(3. In (1) the sense of the symbols are as follows: xN is conversion in N-th cycle, fm and fw are constants. This formula showed good consistency to the experimental data over various conditions however its validity has been limited to just 20 cycles. In their research, Wang and Anthony have therefore proposed a different equationthat is valid for a wide range of cycles. They considered a mixture of thermal sintering and other irreversible processes like crystal growth and the reaction in CaO with impurities within the gas, to be key factors in the decline of the efficiency of CaO-based absorbents. They also suggested that the amount of degradation occurs significantly dependent on experimental conditions [44.

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