Optimal post-combustion conditions for the purification of CO2-rich exhaust streams from non-condensable reactive species

The presence of a significant amount of oxygen and/or other non-condensable species in flue gases of CO 2-capture-ready combustion systems is a relevant issue to be solved to avoid problems in CO 2 sequestration and storage processes. More specifically, oxygen, as well as other non-condensable species, increases the compression work required for the liquefaction of CO 2. Furthermore, residual oxygen in CO 2 streams used for EOR (Enhanced Oil Recovery) operations reacts with hydrocarbons in oil field both causing an overheating at the injection point and a higher oil viscosity increasing extraction cost.Post-oxidation process is a feasible and economical possibility to reduce oxygen and non-condensable/oxidizable species (such as H 2 and CH 4) concentration to one digit ppm (or ppb) levels and obtain high purity CO 2 streams that can be used for sequestration or EOR.This paper presents a numerical study on the post-oxidation processes of a CO 2 rich gas stream, with composition typical of a CO 2-capture-ready system, aimed to outline operative conditions useful to achieve a significant reduction of the gas contaminants below the minimum required level allowing for a useful use of the resulting CO 2 stream for storage or EOR purposes. Attention was focused on output streams of oxy-combustion plants.High temperatures and elevated levels of dilution of inlet streams make such a post-combustion process work in conditions typical of MILD combustion. Characteristic kinetic times and key species concentrations at steady state were evaluated in order to study the evolution and the completion of the oxidation process.Such parameters were correlated to main variables that influence the post-oxidation process such as inlet temperature system, composition of feed mixture, fuel and nature of diluent species