Amine reclaimer technologies

Abstract

Carbon dioxide (CO2) capture in post-combustion by the use of amines is one of several technologies known to reduce the release of CO2 to the atmosphere when burning fossil fuels.One of the problems related to the amine process is amine degradation, which leads to accumulation of degradation products. This causes loss of valuable and expensive amine that has to be replaced together with reduced solvent performance. To prevent these degradation products to accumulate, and to regain lost solvent, a reclaimer can be used to purify the contaminated amine solution. The most effective techniques used to purify amine solutions include distillation (thermal reclaiming), ion exchange and electrodialysis.

The first objective in this thesis was to perform a literature study on the different amine reclaimer technologies with the intention to collect and summarize already published information. The technologies were compared and evaluated. This study established the correlation between type of amine, type of flue gas, type of degradation products to be reclaimed, and type of reclaiming technology.

The second objective was to develop a model of a thermal reclaiming process for monoethanolamine (MEA). Based on vapor-liquid equilibrium (VLE) data, mass and energy balances, a model to reclaim MEA was made. Improvements of the model are suggested.

The third objective was to simulate the reclaimer process model using MATLAB. An ordinary differential equation (ODE) solver was used to solve the set of differential equations. Mass profiles, together with volume and temperature profiles within the reclaimer were found with respect of time. Simulated data was compared to real reclaimer data to test how well the model explains the conditions in a thermal reclaimer. Even though the simulated data did not fit the curves from the real data accurately, the simulations are believed to present the conditions in a reclaimer well. The model still needs some improvements.

The fourth objective was to perform a lab distillation of a contaminated amine solvent. A sample from ACC’s mobile test unit (MTU) at Longannet was collected and distilled in the laboratory. Concentration and temperature profiles were obtained.

Key words: carbon capture and storage, degradation of amines, heat stable salts, reclaimer technologies, MEA, reclaimer waste