Optimisation thermo-economique et environnementale du cycle de vie d'un procede de capture de dioxyde de carbone dans une centrale thermique.

摘要

The research hypothesis outlined in this dissertation advances that a process design decision taken post-optimization with life cycle assessment (LCA), as compared to the decision taken without LCA, brings a long-term economic and environmental benefit with a measurable expectation, at least when environmental constraints have not been internalized in input prices yet, but will be internalized between the design phase and the construction phase.;The case study involves the preliminary design of a post-combustion CO 2 capture process in a natural gas combined cycle power plant. The closed-loop process puts cold flue gas in contact with an aqueous chemical absorbent that reacts with the CO2, after which the absorbent is heated to release concentrated CO2 that can later be injected into a saline aquifer at sea. The environmental impacts of the process stem in majority from the stripper consumption of steam that would otherwise produce more electricity. Additional impacts are generated by make-up absorbent production and by sequestration leaks, as well as by the infrastructure, the machinery and the energy required to compress, dry out, recompress, transport and inject the CO2.;Part of the originality of the approach is that it concurrently explores several absorbent flow and heat exchanger configurations using the unique capabilities of the platform. A secondary research objective is therefore to contribute to the state of the art in CO2 capture process design, especially as it pertains to thermal integration with the power plant steam cycle.;However, the originality of the approach is mainly driven by the fact that it compares decisions made by considering several ways of measuring the environmental impacts, with and without LCA, thus making it possible to assess the contribution of LCA itself for decision-making as well as the significance of the environmental impacts specific to each input (e.g. natural gas, steel, absorbent, or CO2 transport and sequestration services), or specific to each substance emitted (e.g. CO2, other greenhouse gases, or other pollutants).;The main results of the research are that the CO 2 capture costs, per unit of avoided global warming potential, increase by approximately 3% when considering impacts in a life cycle perspective and that it is the CO2 released by natural gas producers and CO 2 transporters that largely contribute to the increase. LCA can therefore lead to better decision-making in several circumstances by fostering energy efficiency and the substitution of biogenic fuels such as synthetic natural gas from wood gasification as well as by choosing to incite suppliers to reduce their emissions. In the specific case in which an anticipated CO2 tax is just enough to give the impression that capture is profitable while a detailed assessment of the same tax as paid by suppliers indicates that it is not, LCA will support the decision to pay the tax rather than capture the CO2, for a net gain of some ;This dissertation’s main contribution to scientific knowledge consists in a new life cycle optimization methodology that combines life cycle assessment and life cycle costing, making it possible to optimize a process design while considering that suppliers will also optimize their emissions themselves because of future taxes or voluntarily through a procurement policy to be determined at a later date. Its originality is based on a method for weighting supply-chain emissions according to the avoidance cost of an optimal combination of prevention and compensation measures. According to the theoretical demonstration set out in the dissertation, this methodology is the only approach that makes it possible to determine a globally optimal design, and it is suggested that its validity extends to all design decision-making in general. (Abstract shortened by UMI.).