Study On CO₂Capture Technology Based On IGCC Power Generation System

To carry out the the CO2capture and geological storage from coal fire power plant is an important measure to reduce the CO2emission of our country. However, the low carbon benefit is often on the condition that system efficiency decreases significantly and the the energy consumption of CO2capture is huge. Comparing to the CO2capture technology used in conventional coal fire power plant, the CO2capture technology based on IGCC(integrated gasification combined cycle) power plants provides a new technological path for CO2reduction of coal fire power system.Pre-combustion CO2capture is very suitable to IGCC system because of the technical features of IGCC power plant itself. A pre-combustion CO2capture process with MDEA acid gas removal and wet oxidation sulfur recovery is studyed to fit in an IGCC plant. The technical feasibility is validated by process simulation. By combining the pre-combustion CO2capture process with the IGCC system, the overall IGCC efficiencies with and without pre-combustion CO2capture are calculated in comparisons. Calculation shows that pre-combustion CO2capture makes the total efficiency decline about10%. Three factors:steam consumption, fuel chemical energy loss and newly increased auxiliary power which cause the IGCC system efficiency drop are discussed in details with potential optimization approaches being presented.In order to systematically analyzed the effect of pre-combusion CO2capture on the energy efficiency performance of IGCC systems with different gasifiers, four cases of IGCC systems have been designed, simulated and compared, including one wet feed IGCC systems with CWS (Coal Water Slurry) gasifier, one dry pulverized coal feeding IGCC systems with a two-stage dry feed entrained flow bed gasifier, both of which have one case with CO2capture and another case without CO2capture. The results indicate that, without CO2capture, the overall energy efficiency of dry feed gasifier IGCC system is3.03percentage points higher than that of the CWS gasifier IGCC system, depending on the integration mode. When CO2capture is added, the overall energy efficiencies of the two IGCC systems both have a certain level of decline, of which the energy efficiency of dry feed IGCC system decreases more. This leads to the energy efficiency of the two IGCC systems with different gasifiers get closer, however that the efficiency of IGCC system with dry feed gasifier is still slightly higher.The CO2capture system based on IGCC needs to remove two kinds of acid gas including CO2and H2S simultaneously. The acid gas removal methods based on Selexol and based on MDEA are the two most prevalent and typical methods. The comparison of merit and demerit of the two acid gas removal methods used in IGCC CO2capture system on different respects, including operating principle, process complicacy, energy consumption, and acid gas removal results, has been done by simulation study and analysis. The study indicates that the two methods both perform well in acid gas removal rate, and the energy consumption is similar. However, the method based on MDEA is more simplified in technological process than the other one, and so it has obvious superiority on system complexity.