Process Evaluation of Flue Gas Treatment for Pressurized Oxy-fuel Combustion Systems

Abstract

Pressurized oxy-fuel combustion with carbon capture allows for fossil fuel use with low greenhouse gas emissions. In order to avoid corrosion and emission of harmful species other impurities in the pressurized flue gas should be minimized. There is therefore an interest in the potential of simultaneous NOx and SOx removal by absorbtion into water under high pressure conditions. The treatment alternatives for the resulting liquid solution from such an absorption process is the main focus of this thesis. The thesis compares the experimental work by Stanger et al. with the detailed reaction mechanism developed by Ajdari et al. through modelling [2], [1]. The model is validated by the experimental work and is thereafter used to evaluate the behaviour of the liquid, which was not measured during the experimental work. The results show that releasing the liquid phase into a waste water pound would result in almost 40% of the nitrogen molecules being released as N2O to the air, which is not desired as N2O is a powerful greenhouse gas. It was also found that isolating the liquid phase would further increased the N2O formation. TheliquidphasealsohasalowpHvaluewhichneedstobetakenintoconsideration. OvertimeitwoulddecreasethepHvalueinthewastewaterpound. LowerpHvalue would also lead to increased N2O formation. Use of a buffer solution to keep the pH value in the waste water pound stable could be a potential solution.