Increasing CO2 carrying capacity of dolomite by means of thermal stabilization by triggered calcination

Abstract

The high-temperature, solid chemical looping for CO2 capture is a promising technology to mitigate greenhouse gases emission. The choice of a high-performance sorbent is a fundamental need to improve the CO2 uptake in solid regeneration systems. Calcium-based sorbents have demonstrated a good compromise between cost, performance and environmental impact. In particular, calcined dolomite is selected as CO2-acceptor in pre-combustion processes due to its good experimental capacity for CO2 uptake. Moreover, among the solid acceptors investigated in scientific literature, naturally occurring sorbents (e.g. calcite and dolomite) are not considered as potentially hazardous substances, as they are not toxic either to the environment or to humans. This work presents the effect on CO2 carrying capacity of different compositions of the calcination atmosphere, from 100% N2 to 50/50% CO2–N2, as well as a novel pre-treatment (here called triggered calcination) by means of half-calcination in CO2 with subsequent flash N2 calcination. This new decomposition method improves CO2 capture up to 24% in prolonged carbonation/calcination cycling (over 150 cycles). Other factors have been studied such as heating rate, CO2 concentration and carbonation time, as well as other pre-treatments. Increased and sustained rates of CO2 uptake can be explained as a result of changes in the internal structure of sorbent particles. In order to explain them, a study of the surface area has been carried out by means of an indirect method based on TGA experiments.