In this research, using the three-dimensional modeling method, computational experiments were carried out to introduce two-stage combustion technology inviting the example of the combustion chamber of the BKZ-75 boiler at the Shakhtinskaya TPP, burning high-ash Karaganda coal. Computational experiments were carried out on the implementation of twostage fuel combustion technology under various modes of supplying additional air through OFA injectors: 0% (basic version, traditional combustion), 5%, 10%, 15%, 18%, 20%, 25% and 30% from the required total air volume. It has been shown that the technology of two-stage fuel combustion allows optimizing the process, improving ignition and combustion conditions and minimizing emissions of harmful substances.