The energy use of fossil fuels is accompanied by toxic gaseous components of combustion products contaminating the environment. The current legislation in the field of environmental protection prescribes observing the emission standards both in new construction and in improvting the energy equipment. The results of a comprehensive approach to solving the problem of reducing the harmful effects through modernizing the power boiler through introducing the low-temperature vortex combustion method. We have developed a technique, an algorithm, and a calculation scheme for substantiating the possibility of efficient coal-burning ensuring low pollutant concentrations in exit gas from the boiler. We have also conducted a quantitative assessment of the emission level and a comparison between the calculation results and the experimental data obtained at a modernized facility.