Performance of MEA and amine-blends in the CSIRO PCC pilot plant at Loy Yang Power in Australia

Chemical reactive liquid absorption in post-combustion carbon capture (PCC) has sparked an interest of many researchers for improvement in creating high CO2 absorption capacity and minimising the reboiler heat duty for regeneration. This paper discusses results from performance trials on different solvents: mono-ethanolamine (MEA-baseline), a mixture of MEA with 2-amino-2-methyl-1-propanol/AMP (Blended Amine 1) and Blended Amine 2 (a propietary solvent developed by Research Institute of Innovative Technology for the Earth (RITE), Japan). The trials were carried out in CSIRO's PCC pilot plant at Loy Yang Power. The pilot plant receives flue gas from this 2.2 GW brown coal-fired power station in the Latrobe Valley, Victoria. The study has shown the benefits of using blended solvents for CO2 capture in terms of CO2 recovery and reboiler duty for solvent regeneration. The correlation of CO2 recovery and process parameters, i.e., liquid and gas (L/G) ratio and lean loading, has been established for the range of solvents tested. The results show that, in general, an increase of L/G ratio increases the CO2 recovery. It is also noted that a solvent at higher lean loading requires a greater solvent (recycle) flow rate, or vice versa, in order to capture a given amount of CO2. The effect of reducing the stripper's bottom temperature from 115 to 112 degrees C reduced the CO2 recovery of both MEA and Blended Amine 1 as their solvent lean loadings are raised. The same temperature change, however, did not significantly decrease CO2 recovery of Blended Amine 2, as it also shown by insignificant changes in solvent lean loadings. The results also indicate that the reboiler heat duty is dependent upon L/G ratio, solvent lean loading and blending solvent type. For the MEA-115 degrees C, a minimum reboiler heat-duty as a function of L/G ratio is clearly observed and the Blended Amine 1-112 degrees C has also shown a similar pattern. In contrast, Blended Amine 1-115 degrees C showed excessive energy duty, which indicates unfavourable condition for this solvent. This is not the case for Blended Amine 2. It is observed that the reboiler heat duty decreases as stripper bottom temperature decreases, which in turn raises the lean loading for both MEA and Blended Amine 1. On the other hand, the lean loading of Blended Amine 2 in the temperature range examined did not affect the reboiler heat duty changes. The investigation also found that the magnitude of reboiler duty is decreasing following the order MEA > Blended Amine 1 > Blended Amine 2. In order to obtain CO2 recovery of 85%, the Blended Amine 2-115 degrees C (L/G = 3.60) has similar reboiler duty relative to that of MEA-115 degrees C with L/G ratio of 4.12. For the Blended Amine 1 (L/G = 3.04), however, the reboiler heat duty increased by 51% at a similar temperature. The temperature reduction to 112 degrees C decreased the reboiler heat duty of both Blended Amines 1 and 2 by 11% (L/G = 4.01) and 14% (L/G = 3.60) respectively. Further raising the CO2 recovery to 90-95%, in comparison to that of MEA at 115 degrees C with L/G ratio of 4.20, the reboiler heat duty of Blended Amine 1 has risen by 49% (L/G = 3.95) and of Blended Amine 2 dropped by 5% (L/G = 3.52) under a similar temperature. At 112 degrees C, the reboiler heat duty of Blended Amine 1 decreased by 18% (L/G = 5.02). Blended Amine 2 may give a similar reboiler heat duty if run at a larger L/G ratio. Overall, the result of the MEA baseline and blending solvents has shown different behaviours of CO2 stripping. The distribution of the components of reboiler heat duty may explain this difference. For MEA, the condenser heat, which equals the heat needed for water evaporation, is a major contributor to the reboiler duty. For both Blended Amine solvents, the magnitude of sensible heat and the heat of CO2 desorption are more pronounced than the condenser heat. At the minimum reboiler duty reached by MEA and Blended Amine 1, the condenser heat share is lower than the other reboiler duty components. Therefore, further works involve optimisation of the PCC process with blended Amines and other blends. (C) 2012 Elsevier Ltd. All rights reserved.