Cleaner power from coal
High-ash coals have been widely used for generating power and industrial steam in India and Turkey, and this is likely to continue for the foreseeable future. Unfortunately, burning coal directly to produce steam for a turbine produces high levels of pollution, including greenhouse gas emissions. Coal gasification is an alternative to its direct combustion, providing cleaner power. The EU-funded project OPTIMASH (Optimizing gasification of high-ash content coals for electricity generation) optimised a relatively new technology called integrated gasification combined cycle (IGCC) to improve the properties of Indian and Turkish coals' ash content. The initiative's aim was to enhance the operating conditions of IGCC technology. The consortium found that fluidised bed gasification technology was particularly suited to converting high-ash coals. Indirect and direct fluidised bed gasification processes were therefore evaluated and tested. Project partners characterised the ash content by conducting chemical, thermal and petrographic analyses. They also carried out particle size distribution and heavy liquid tests on coal samples. Using thermal analysis and mass spectroscopy methods, researchers also studied pyrolysis, combustion and gasification kinetics. This work was supported by computational fluid dynamics models. Results showed that the 1 thermal megawatt OPTIMASH demonstration plant provided sufficient data for scaling up gasification plants for a range of power levels and applications. Simulation results indicated that the modelling was successful and suitable for analysing the effects of the key operation on the gasification results. The supply of steam was found to have positive effects by increasing the hydrogen yield and the proportion of hydrogen content in the produced syngas. It also had positive effects on the higher heating value of the syngas and the efficiency of gasification. In addition, the selective absorption of hydrogen sulphide and ammonia components in IGCC plants helped to reduce the emission of sulphur oxides and nitrogen oxides from the gas turbine. As a low-carbon coal technology, the OPTIMASH pilot gasification system will contribute to reducing harmful emissions from power plants. IGCC is a particularly attractive choice given that it can be combined with technology for capturing carbon dioxide and sequestering it underground.
Keywords
Power plants, high-ash coals, OPTIMASH, electricity, fluidised bed gasification
