Increasing Energy Efficiency of Thermal Power Plants Based on Exergic Analysis and Optimization of Heat Recovery Systems

The study objective is to analyze existing heat recovery systems (HRS) of power plants, demonstrate the possibilities of exergic method for their evaluation and optimization, as well as feasibility study for their implementation. The main task is to apply a thermodynamic approach based on the second law (exergic analysis) to identify and minimize irreversible energy efficiency losses in HRS per day, which allows to move from a quantitative to a qualitative assessment of their effectiveness. Methods and solutions include exergic method, mathematical modeling, and system analysis. Constructive and technological solutions are considered: modular HRS for internal combustion engines with recovery boilers, combined steam-to-gas cycle (SGC) and cascade systems with an organic Rankine cycle (ORC). The novelty of the work is in the integrated application of exergic approach for comparative analysis and optimization of different types of HRS, as well as in the generalization of data on commercially available equipment for thermodynamic and feasibility studies. Main results and conclusions: Exergic analysis made it possible to localize the key sources of irreversibility – the combustion chamber and the zones of high-temperature heat exchange. It is shown that the HRS introduction especially in combined cycles increases the total efficiency of installations to 80-90% with a payback period of 2-5 years. Optimization according to exergic criteria leads to lower fuel costs, emissions and an increase in the sustainability index. Cascade heat utilization, ORC integration, and control system intellectualization are recognized as promising areas.