Exergoenvironmental analysis of a combined heat and power system for district heating using coal water slurry

The combined heat and power (CHP) system using clean fuel coal water slurry has been regarded as a high-efficiency alternative for conventional coal-fired district heating systems. However, there is a lack of quantitative evaluation of the environmental performance of such systems, and the previous research is mostly based on the simulation model. In this paper, taking an actual running CHP system for district heating as an example, the thermodynamic and environmental performances are quantitatively evaluated by means of exergoenvironmental analysis. From the two levels of system and equipment, the performance level and improvement potential are determined. The results show that the environmental impacts per unit exergy of thermal and the power of the system are 5 434 mPts/GJ and 3 617 mPts/GJ, respectively. The exergy destruction of system components is the dominant source of total environmental impacts, and the improvements in the environmental performance should focus on enhancing components’ exergy efficiency. The coal water slurry boiler and the steam-water heat exchanger have greater potential to improve environmental performance.