Modeling the Performance, Emissions, and Costs of Texaco Gasifier-Based Integrated Gasification Combined Cycle Systems

Abstract

Integrated Gasification Combined Cycle (IGCC) systems are an advanced power generation concept with the flexibility to use coal, heavy oils, petroleum coke, biomass, and waste fuels to produce electric power as a primary product. IGCC systems typically produce sulfur as a byproduct. IGCC systems are characterized by high thermal efficiencies and lower environmental emissions than conventional pulverized coal-fired plants. This study deals with the development and application of new systems models for estimating the performance, emissions, and cost of entrained-flow gasification-based power generation systems, including characterization of uncertainty in the estimates. The study focuses on modeling and assessment of three Texaco gasifier-based systems using ASPEN, a steady-state chemical process simulator. The first model is a coal-fueled IGCC system with a radiant and convective high temperature gas cooling design. The second and third models use a total quench high temperature gas cooling design with one of them using coal as fuel and the other using heavy residual oil as fuel. ASPEN-based performance models were developed for all three cases by substantially modifying a performance model previously developed by the U.S Department of Energy's Federal Energy Technology Center. New models for auxiliary power loads, emissions, and capital, annual, and levelized costs were developed for all three systems. The system models incorporate details regarding key process areas, such as mass and energy balances for the gas turbine and gasifier. The gas turbine process area performance model was calibrated to published data for operation on natural gas and also to data for operation on syngas. Example case studies were done on each of the IGCC system models and the results obtained were compared with each other. The models developed captured the critical interactions between the various process areas of the IGCC systems. The radiant and convective-based system has higher plant thermal efficiency of 39.4 percent, higher total capital cost of $/kW 1732, and higher cost of electricity of 50.88 mills/kWh than the total quench based-system models. The coal-fueled total quench model has lower plant efficiency of 35.0 percent when compared to that of 39.3 percent of the heavy residual oil-fueled total quench-based system model. However, the total capital cost of $/kW 1540 and cost of electricity of 47.67. mills/kWh of the former are higher when compared to those of the latter which are $/kW 1129 and 26.96 mills/kWh respectively. Since the IGCC systems are in the early stages of development, there are inherent uncertainties in the performance and cost parameters. Probabilistic performance models were developed for each of the IGCC systems using a probabilistic modeling capability previously developed for ASPEN. Probabilistic analysis provides a systematic framework for the evaluation of technological risks such as possibility of poor performance, high emissions, and high costs compared to more conventional technologies. The probabilistic analysis techniques were applied to case studies to evaluate and identify the key uncertainties in the inputs of the IGCC system models. The probabilistic analysis indicated that the range of the plant thermal efficiency of the radiant and convective coal-fueled model (38.0 - 39.5 percent) and that of the total quench heavy residual oil-fueled (37.9 - 39.5 percent) is higher than that of the total quench coal-fueled model (33.5 - 35.1 percent). However, the range of cost of electricity of radiant and convective coal-fueled model (45.4 - 55.6 mills/kWh) and that of total quench coal-fueled model (46.5 - 51.9 mills/kWh) are significantly higher than the range of cost of electricity of the total quench heavy residual oil-fueled model (27.0 - 32.2 mills/kWh) The probabilistic analysis reduced the total number of uncertainties from 40 to 16 in the coal-fueled cases and to 12 in the heavy residual oil-fueled case. The uncertainties in costs can be further reduced by providing detailed cost estimates and the need for the same has to be evaluated. The models can be utilized as benchmarks for comparison with more advanced power generation technologies.