Economical evaluation of the carbonation-calcination system for capturing CO2

Abstract

The cost of the CO2 capture using carbonation-calcination cycles as a technological option of the CO2 capture in post combustion is the sum of several terms: sorbent costs, capital costs related to the capture plant, the new operation and maintenance processes, the cost of the additional fuels necessary to compensate the penalty in the efficiency due to the capture, and the cost of the CO2 compression. The required conditions for the sorbents are that they have to be either very goods or very cheap. The cost of the sorbent flow can’t be higher than 1-3 € per separated CO2 ton. In the case of utilisation of CaCO3 as a sorbent, it has been calculated that the cost per separated CO2 ton is 2,5 €. The problem of this sorbent is that its deactivation is quick, but this is compensated by its high abundance in the nature. Apart from this, it has to be into account other terms in order to obtain the global cost. It has supposed a generation plant of 360 MW with a fluidized bed reactor. It has been estimated that it can be reached a realistic capture up to 78% in the carbonator using CaO as a sorbent, as well as a 100% of the CO2 generated in the calcinator, resulting capture rates of 85% approximately. The assumptions for the operation and maintenance are that the carbonators require a molar relation Ca/C of 4 for an effective CO2 capture, a 30% of the fuel is burned in the calcinators and the rest in the combustor, the capacity of the CaO to capture CO2 decreases with the number of cycles, the recuperation rate of CaO is 92,5%, the global efficiency of the plant is 40,7%, the fuel is petroleum coke or anthracite. Furthermore, taking also into account the capital costs and the compression of the CO2, it has been calculated that the global cost is 15,5 € for a life of 30 years of the plant. Therefore, a priori it seems to be a reasonable cost compared with the technological options of CO2 capture that are in operation nowadays, specially those which use amines