Simultaneous Optimisation and Integration of Igcc Plant Using Graphical Method

Abstract

As a promising green technology, Integrated Gasification Combined Cycle (IGCC) plant is more efficient and low-pollution electricity generation choice than conventional thermal power plants. Its process is mainly consist of the gasifier, the air separation unit and the combined cycle unit. Going through those key blocks, the fuel, such as coal and biomass, could be converted to syngas and further combusted for power generation. In order to be a viable technology, the bottleneck is located on the high energy production cost, which could be overcame by improving the plant efficiency through process optimisation and Integration. The opportunity and challenge are given by the complicated configuration and extreme operation conditions, which also demands a flexible and robust IGCC plant simulation to complete deep process analysis. In this work, a novel simplified IGCC mathematical model is proposed considering thermodynamics constraints with energy and mass conservation. The gasification is simulated based on the principle of Gibbs free energy minimisation, which holds the good feature of avoiding potential bi-level optimisation problem. The proposed gasification model results in syngas composition similar to the experimental data provided in literature. Meanwhile, the cryogenic air separation unit is selected with the double distillation column configuration, which is simulated considering the novel simplification of thermal coupled distillation columns. What is more, the combined cycle unit is simulated with isentropic assumption plus efficiency to complete the process. To validate the novel simplified IGCC model, one base case is built and compared with literature data. Another highlight of this work is the simultaneous optimisation and integration methodology instead of conventional sequential one, which gives more guarantee for achieving global optimal solution. If the ideal property assumptions are occupied, a graphical approach could be generated for the simultaneous optimization and integration of IGCC plant. The best material and energy integration scheme in proper operation condition could be selected considered with respect to the overall thermal efficiency of the IGCC plant. The good performance is shown by about 10 % power increment compared with the base case in the case study.