PHASED CONSTRUCTION OF INTEGRATED COAL GASIFICATION COMBINED-CYCLE POWER PLANTS (GAS TURBINES, STEAM TURBINES)

An integrated coal gasification combined-cycle (IGCC) power plant is a combined-cycle plant fueled by synthetic fuel gas produced by gasifying coal. It can be constructed in several phases, operating first as a combined-cycle power plant fueled by natural gas. A coal-gasification facility is added later to supply the fuel. The problem is how to design a plant to operate in such a manner most efficiently.; A computer-based simulation model was developed to predict the performance of IGCC power plants under steady-state operation, both at the design point and under off-design conditions. The ASPEN flowsheet simulator serves as the framework for the calculations. Detailed models were developed for critical components; two of these models are the Stanford Turbine Evaluation Program (STEP), which uses correlations based on turbine test data and engineering analyses to predict design-point, part-load, and off-design performance of steam turbines, and a heat exchanger model based on the effectiveness-NTU methodology and experimental data collected for various heat-transfer surfaces. Outputs from the complete system model include net power production and efficiency, as well as the temperature, pressure, composition, and mass flow rate of each stream in the plant.; In this study, various initial and final plant designs representing different phased-construction scenarios were investigated and the performance of the plant at each stage analyzed. Those situations requiring modifications in the standard plant operation and control strategies were identified, and the effects of these modifications on overall plant performance were examined. The results show that if a plant were designed for IGCC operation, but operated as a natural-gas-fired combined-cycle plant, many components would be oversized, but the efficiency would remain relatively high, ranging from 40.5% to 43.0%. If the plant were designed for natural-gas firing, but operated as an IGCC facility, many components would be undersized and special operating techniques would be required. The efficiency and power output of such an IGCC plant would be considerably poorer than that for the optimized, base-case IGCC design.