Abstract
The objective of this paper is to present a single equation format for quantifying the net carbon balance (NCB) in the evaluation of CO2 capture technologies, and to discuss the benefits of this approach. The equation must take into account indirect emissions, especially the contributions from utility generation systems (heating, cooling and electricity), making use of efficiency values and emission factors. The idea is to synthesize, in a single expression, the quantification of the environmental footprint of a technology, in a practical way so that it could be used as an efficient metric in technical evaluation studies, or as objective function/constraint in optimization problems. It also facilitates demonstrating the relationship between capture efficiency and environmental performance, as well as the contribution of each term to total emissions, and to compare different technologies in terms of time, location and available energy sources. To illustrate the application of the proposed NCB formulation, two processes were compared in two different scenarios: post-combustion and pre-combustion capture with MEA absorption, in a Base Case formulated with literature premises and an NCB Zero Case meaning carbon neutrality. A process simulator - Aspen HYSYS - was used to solve the mass and energy balances associated with each process, providing the necessary information for NCB calculation, whose parameters were obtained from the technical literature and were discussed in relation to their importance to the proposed analysis.