Abstract
It was aimed to simulate a conventional dual-stage Selexol process for removing CO2 and H2S simultaneously from a synthesis gas (syngas) originated from a typical Integrated Gasification Combined Cycle (IGCC) power plant driven by a dry-coal fed gasifier using Honeywell UniSim R400. The solubilities of syngas components on Selexol were predicted by temperature-dependant Henry’s law constants being newly evaluated in this study based on the experimental data in Xu et al. (1992). The operating conditions of the dual-stage Selexol unit were determined so as to meet simultaneously various performance targets, such as 99+% H2 recovery, 90% CO2 recovery, 99+% H2S recovery, and less than 20ppm H2S in CO2 product. By and large the resulting energy consumptions of the Selexol process were in good agreement with those reported in DOE NETL (2010) that this study was based on. It was shown that the integrated dual-stage Selexol unit could achieve 95% carbon capture rate as well as 90% by simply changing the operating conditions. By contrast a CO2 removal Selexol process having not an input of lean solvent generated by thermal regeneration could not achieve 95% carbon capture rate due to a pinch point formed at the top of the CO2 absorber.
Highlights
Anthropogenic CO2 emissions into the air have long been thought to be the most important agent to give rise to global warming and climate change
The acid gas removal unit for H2S removal in Integrated Gasification Combined Cycle (IGCC) can operate at a higher pressure and with a less volumetric gas flow than the Flue Gas Desulphurisation (FGD) unit for SO2 removal in PC-fired boiler power plants being applied to the flue gas after combustion
Bhattacharyya et al (2011) implemented a comprehensive process simulation of an entire IGCC power plant integrated with a dual-stage Selexol process for 90% overall carbon capture efficiency
Summary
Anthropogenic CO2 emissions into the air have long been thought to be the most important agent to give rise to global warming and climate change. (1999) studied a Selexol process to recover 90% CO2 from a shifted syngas They concluded that the addition of a Selexol process for carbon capture would result in 5–7% reduction in the LHV-based power efficiency and around 40% increase in the cost of electricity. DOE NETL (2002) investigated CO2 capture from oxygen-blown, Destec and Shell-based IGCC power plants at the scale of a net electrical output of 400 MWe. In the study, a dual-stage Selexol process was integrated for capturing CO2 from IGCCs at an overall capture efficiency of 87%. Cormos and Agachi (2012) performed case studies on 400–500 MWe net power IGCCs integrated with acid gas removal processes using several physical solvents including Selexol for 90–92 % carbon capture efficiency. Bhattacharyya et al (2011) implemented a comprehensive process simulation of an entire IGCC power plant integrated with a dual-stage Selexol process for 90% overall carbon capture efficiency. The power and thermal energy consumptions of various designs of dual-stage Selexol processes could be estimated accurately by performing their process simulation using a process flow sheeting simulator (UniSim R400)
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