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Dilute aqueous ammonia (NH3) process is considered as one of the alternative post-combustion carbon dioxide capture (PCC) technologies. However, the energy consumption for solvent regeneration is quite high, about 0.15–0.25 MWh/ton CO2 captured as equivalent work consumption. Therefore, reducing this valuable energy duty is still the major technica...
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Citations
... Le et al. [27] reported the energy performance of a lean vapor recompression system for the ammonia-based CO 2 capture process. Further, an advanced flash stripper process was proposed to reduce the regeneration duty as low as 1.86 MJ/kg CO 2 using higher stripper pressure and 10.2 wt% NH 3 concentration [21]. ...
Carbon-based fuels contribute majorly towards global energy demand; however, it results in global warming. The increasing energy demand and climate change highlights the need to develop cost-effective carbon sequestration schemes. Amine-based CO2 scrubbing have been widely used for their high selectivity and production of pure CO2. However, a challenge in implementing amine-based technology is high energy consumption with a low capture ratio. The energy penalty can be reduced either by introducing new solvents, optimizing parameters, or through process modifications. Recently, ammonia has tempted attraction in place of amines. In this present work, a Radfrac model in Aspen Plus is developed involving heat integration and absorption enhancement to overcome the barriers. The heat integration is performed with a rich solvent split and absorption enhancement is done with split flow arrangement. Further, the model is evaluated at different split ratios by performing heat integration between different streams of the flowsheet. Moreover, the process configurations used in this system is compared with MEA based process modifications concerning energy reduction. A competitive reduction in regeneration duty was observed which was 36% less than the reference NH3 and 47% less than the MEA process. This evaluated modification will result in maximum efficiency, a maximum level of CO2 capture, and a reduction in the reboiler duty. The rich solvent split and split flow process reduced the reboiler duty by 15.8% and 32.8%, respectively. The split flow process also indicated an increase of 17.2% in rich loading to recover 90% CO2.
In this work, we have developed advanced process configurations for solvent-based CO2 capture processes that use aqueous ammonia as absorbent. In total, ten different advanced configuration concepts have been optimized and analysed, aiming at: (i) achieving in spec NH3 emissions in a controlled way; (ii) minimizing capital costs by avoiding redundant process components; (iii) minimizing the energy demand of the capture process by minimizing the requirements of high temperature steam and by maximizing the possibilities for the use of excess heat from the CO2 point source. As a result, we propose a new benchmark configuration for NH3-based capture processes that, with proper tuning of the process operating conditions, allows to minimize the specific energy consumption while enhancing the flexibility of the capture process with respect to the type and to the features of the electricity and steam available at the CO2 point source, at the minimum consumption of chemicals and process water. This new benchmark configuration for NH3-based capture processes is built upon the Chilled Ammonia Process, avoids the formation of solids and includes: (i) a multi-pressure desorber with recycled vapour compression that is able to decrease the high temperature steam requirements for solvent regeneration, i.e. at ca. 140–160 °C, to values as low as 1.1 MJthkgCO2captured−1, (ii) a vacuum integrated stripper for the recuperation of the solvent that is able to use low temperature steam instead, i.e. below 100 °C, and (iii) a flue gas water-wash column that is able to reduce the NH3 concentration in the CO2-depleted flue gas to values below 10 ppmv without the need of an acid-wash column before the stack.
Post-combustion carbon capture (PCC) using a chemical solvent is the most mature and well-proven technology to mitigate carbon dioxide (CO2) emission. However, substantial energy consumption for solvent regeneration is still a critical challenge for widespread deployment of this PCC. In this study, a novel low-energy, combined rich and lean vapor recompression (RLVR) process for the CO2 capture process using dilute aqueous ammonia (NH3) solvent was developed and optimized by integrating of rich vapor recompression (RVR) and lean vapor recompression (LVR) approaches. A parametric study showed that the minimum total equivalent work can be obtained when CO2 loading and NH3 concentration of lean solution are 0.275 mol CO2/mol NH3 and 5.0 wt%, respectively and the pressures of stripper, rich and lean solvent flash drums are maintained at 10.5 bar, 4.62 bar and 6.93 bar, respectively. Under such operation conditions, the total equivalent work required for a CO2 capture plant was remarkably reduced to 0.123 kW h/kg of CO2 captured, which is equivalent to about 10% energy penalty. This amounts to 26∼54% reduction from recent literature reports. Furthermore, this combined RLVR process can completely eliminate the need of reboiler, leads to improving the flexibility of the capture plant since it can be separated from power plant steam systems.
