Optimization of Two-Stage Compression Process for Coal-Fired Carbon Dioxide Power System

In comparison with coal-fired steam generating set, high-parameter coal-fired carbon dioxide power generation system is such a new type of power generation system, which possesses potential advantages in efficiency, equipment volume and material selection. The optimization of the compression and cooling process in the coal-fired carbon dioxide power generation system was researched. Taking total power consumption and system efficiency of the compressor as evaluation indicators, the EES software was adopted to perform the simulation analysis. Firstly, the power consumption in the compressor and the change rule of compressor’s outlet temperature of conventional coal-fired carbon dioxide power generation system were analyzed. On this basis, according to the principle of energy cascaded utilization, an optimization system was proposed. Computation results show that total power consumption of the compressor first decreases and then increases along with the increase of pressure ratio of low-pressure (abbr. LP) compressor, i.e., there exists an optimal pressure ratio for LP compressor. By this time, the main steam parameter is 30MPa/600°C, the optimal pressure ratio of LP compressor is 1.66, and the system efficiency is 44.1%. The outlet temperature of LP compressor increases with the increase of the pressure ratio of LP compressor, however the variation trend of the outlet temperature of high pressure compressor was opposite. Based on the principle of energy cascaded utilization and optimizing the compression and cooling process, the system efficiency is improved and increases with the inlet temperature and the pressure ratio of the LP compressor. When the inlet temperature of LP compressor is 160°C and the system efficiency is 46.2%, the optimal compression ratio is 1.325.