Development of Advanced Amine Systems with Accurate Vapour-liquid Equilibrium Measurement
Creators: name: Tong, Danlu
Publisher: name: Imperial College London
Year: 2012

description: Imperative pressure on containing anthropogenic greenhouse gas (GHG) emissions, particularly CO2, has led to the development and deployment of low-carbon technologies across the globe. Carbon capture and storage (CCS) is widely considered as an indispensible part of the technology portfolio alongside energy efficiency, renewables and nuclear. Due to its operational flexibility and technology maturity, post-combustion capture (PCC) is most likely to be one of the first adopted capture processes. However, the associated capital expenditure (CAPEX) and operating cost (OPEX) of the current state-of-the-art PCC process are seemed as the major barriers for its commercialisation. This thesis investigated the relationship between the chemical structure of the amines and their CO2 cyclic loading capacity through solubility measurements with two types of apparatuses: a static-analytical apparatus and a static-synthetic setup. The former was first validated by measuring the solubility of CO2 in 30 mass% aqueous monoethanolamine (MEA) solutions at = T (313 and 393) K and a total pressure range between (11 and 415) kPa. After successful validation of the apparatus, new CO2 solubility data for a sterically-hindered amine, 2-Amino-2-Methyl-1-Propanol (AMP) were obtained at temperatures between (313 and 393) K and a total pressure range of (23 to 983) kPa. CO2 solubility data for a tertiary amine, 2-Dimethylaminoethanol (DMMEA) were also measured with the analytical apparatus from T = 313 K to T = 393 K and a total pressure of (6 to 616) kPa. Apart from the three single amines studied, this work investigated the blended amine systems and the influence of an activator (piperazine or PZ) on the promoted amines. For AMP + PZ blends, solubility measurements of CO2 in 25 mass% AMP + 5 mass% PZ and 20 mass% AMP + 10 mass% PZ were conducted from (313 to 393) K; while for the DMMEA + PZ mixture, 25 mass% DMMEA + 5 mass% PZ system was studied. The static-synthetic setup employed in this work was first validated through measuring the solubility of CO2 in water from (313 to 393) K. A calculation algorithm implemented in Microsoft Excel as VBA was used to convert the experimental data to Henry‘s constants which were then compared with literature data. After the validation, CO2 solubility of 25 mass% MDEA was measured at 313 K. Another aspect of this work involved building quasi-chemical thermodynamic models to interpret the experimental data obtained in both apparatuses. This work used two different methods including Deshmukh-Mather model based on activity (γ)-fugacity (φ) approach and a more simplified Kent-Eisenberg model to represent the single and mixed amine systems respectively. Despite the compromise in the correlation quality compared to the γ- φ approach, Kent-Eisenberg model has received wide popularity due to its simplicity. In this work, the correlation results from the two models were compared. The applications of the models to predict solution phase speciation and CO2 solubility behaviour not measured in this work were also discussed.