CFD Modeling as an IT-Support Tool for NOx Emission Reduction at Coal-Fired Thermal Power Plants

In recent years, a sharp increase in coal-based power generation has been observed in a number of countries. Coal-fired thermal power plants remain the main source of harmful emissions in the energy sector of many countries, including Kazakhstan. This creates a strong need for the development of effective methods to reduce pollutant emissions at thermal power plants. The aim of the present study is to perform a numerical investigation of the effectiveness of staged combustion technology with secondary air injection (Over-Fire Air, OFA) applied to three boilers—PK-39, BKZ-160, and BKZ-75—which differ in design, capacity, and furnace configuration. CFD modeling was carried out using the FLOREAN package, adapted to the conditions of the Kazakh energy sector, which relies on high-ash coal (more than 40%) for coal-based power generation. Model validation was performed against experimental data obtained from operating thermal power plants. It was found that air injection through OFA injectors intensifies turbulent mixing, reduces peak temperatures in the main combustion zone, and ensures a more uniform distribution of heat release along the furnace height, thereby suppressing thermal NOx formation. It is shown that the spatial structure of NO concentration fields at the furnace outlet strongly depends on the design features of each boiler. The results demonstrate the high efficiency of staged combustion technology in reducing nitrogen oxide emissions and improving the environmental performance of pulverized-coal boiler units. The obtained results can be used in the design of new and the modernization of existing thermal power plants utilizing coal-based power generation.