DEVELOPMENT OF A PROCESS MODEL FOR THE PREDICTION OF ABSORBENT DEGRADATION DURING CAPTURE

Abstract

Fossil fuels are used widely for energy production and are likely to continue to play a major role world wide for many years to come. Much work has been done on the technology for capturing CO₂ from gaseous industrial e ffluent. For large-scale applications like coal or natural gas-fired power plants, using amine solvents to capture post-combustion CO₂ is the most mature CO₂ capture technology. This technique can be used to retro fit existing plants by treating the flue gas after combustion. This thesis contains a dynamic mathematical model for the absorber column that can be used to include more detailed reaction chemistry for the absorption of CO₂ into an amine in the presence of O₂ as it becomes available. The dynamic model is constructed from first principles and, while it is built using MEA as the absorbent to remove CO₂, it can be adjusted to cater for the removal of different industrial gases with various absorbents. The model is solved using a commercial solver, MATLAB Ode15s when reduced to a system of ODE's by finite difference in the spatial dimension. The flux of MEA, CO₂, O₂ and H₂O across the phase interface in either direction has been included and more components can be added as required. The loss of MEA through oxidative degradation has been quantified which is currently not available using commercial packages. Reaction rate kinetics have been employed to predict the accumulation of oxidation products which is limited by the incomplete knowledge of the dominant reactions between O₂ and MEA. When research has produced more detailed information about the products formed during this oxidation, it can be inserted easily into the model. Validation has been performed using data from the CSIRO PCC pilot plant at AGL Loy Yang. A limited parametric study of the impact of operating conditions on oxidation was performed.