Energy Efficiency and Capital Cost Estimation of Superheated Steam Drying Processes Combined with Integrated Coal Gasification Combined Cycle

抄録

The Integrated coal Gasification Combined Cycle (IGCC) is one of the clean coal technologies because of its excellent low environmental impact and its high thermal efficiency. In recent years, IGCC plants tend to use low-rank coals (LRC), which contain a large amount of moisture. A drying process based on self-heat recuperation (SHR) technology has been developed to greatly reduce the energy consumption because of its capability of recuperating the latent and sensible heat of water and dried coal. It has been shown that the SHR drying process uses less energy than the mechanical vapor recompression (MVR) drying process. For the commercialization of the SHR drying process, the energy consumption and cost are important. In this study, the thermal efficiency and capital cost of superheated steam drying processes (MVR, original SHR (SHR-A), and simplified SHR (SHR-B)) of LRC (sub-bituminous coal and lignite) combined with the IGCC plant were evaluated by using a commercial process simulator, ASPEN Plus ver. 7.2. The results show that the energy consumption of the SHR-B drying process was smaller than that of MVR and the SHR-A processes when the air flow ratio was small. The reduction of thermal efficiency in the IGCC plant due to drying in these processes was less than only 1.4%. It was found that the cost of a compressor and heat exchangers were the major contributors to capital cost in these drying processes, and that overall heat transfer coefficient in the heat exchanger is a critical factor to determine total capital cost. The estimated fixed capital investment of the SHR-B drying process is in the range of 25.6–66.9 million US$ for sub-bituminous coal and 28.7–75.3 million US$ for lignite when the air flow ratio was 0.02. These values were only 1.79–4.68% of the IGCC plant total capital cost of sub-bituminous coal and 1.86–4.86% of that of lignite.