Desarrollo de reactores de lecho fluidizado para la captura de CO2 con CaO

Resumen

[EN] CO2 emission levels have experienced a sharp increase in recent years mainly due to the use of fossil fuels to meet the increasing global energy demand. This phenomenon has promoted changes in the behaviour of the climate system and has contributed to what is known as climate change. This is the main reason why we need options that allow CO2 emissions to be reduced to levels that are assumable and compatible with the climate system. However, all predictions clearly indicate that fossil fuel consumption will increase over the next few decades, and this will entail a substantial increase in CO2 atmospheric concentration unless other measures are adopted. One of the alternatives proposed for the short and medium term consists in decoupling CO2 emissions from fossil fuels usage by developing CO2 capture processes. The objective of these processes is to separate the CO2 present in the gas streams produced in large stationary emission sources for its permanent storage. To this end, CO2 capture by means of carbonation-calcination cycles is one of the proposed technologies and constitutes the subject of study of the present Doctoral Thesis. The work conducted for this Thesis has been focused on the development of the CO2 capture technology at high temperature using CaO as sorbent in some of its main process routes as a step towards its implementation at industrial scale. For this purpose, several pilot-scale experimental tests were carried out, as well as studies related to the modeling of the reactors involved in the system and the incorporation of improvements to the process. Specifically, this dissertation consists of the two sections outlined below. The first section comprises the experimental tests performed at a postcombustion CO2 capture pilot plant which uses real flue gases from an industrial power plant and also includes the experimental campaigns carried out in a pilot plant of simultaneous combustion and in situ CO2 capture. The results obtained under different operating conditions are presented for both cases. A study of the influence of the key process variables and the validation of available reactor models using the experimental data are also provided. The second section of this Thesis comprises a series of in-depth studies into some of the aspects of CO2 capture processes based on the carbonationcalcination technology. First, a hydrodynamic study of the interconnected circulating fluidized bed reactors used in this technology is presented. Moreover, the effects of the presence of inerts (sulfur and ashes) on the characteristics of the circulating solids and CO2 capture efficiency are evaluated. The final part of this Thesis is focused on a novel sorbent reactivation strategy: recarbonation. For this purpose, a kinetic study of the recarbonation reaction has been carried out under different operating conditions and the information obtained has been used for the modeling and preliminary design of a recarbonation reactor.