In this paper, the fuel oil-water-air system at a wide temperature range (T=500-3000K) was studied and the ratio of gas-liquid flows (water content in fuel oil 5-15%) at the maximum entropy of the system and the formation of soot in flue gases was revealed. To reduce the concentration of soot in flue gases, a fuel oil-water emulsion was used. The particle sizes of the fuel oil-water emulsion were determined by sedimentation analysis. It is shown that they have a polydisperse character (diameter from 8.96 to 59.02 μm). The water content in fuel oil during the preparation of fuel oil-water emulsion in the boiler room was controlled by a capacitive sensor. The water flow was automatically maintained by an ejector-dosing device. The thermodynamic parameters of the system (entropy, enthalpy, internal energy) were calculated and their comparative characteristics were obtained. The concentration distribution of hydrogen, carbon, nitrogen, sulfur and oxygen containing molecules, particles and condensed phases in the gas phase has been established. During the combustion of the fuel oil-water emulsion, the concentration of soot in the gas phase decreased due to an increase in hydrogen-containing particles in the gas phase, i.e. an increase in the H/C ratio, as well as a change in the concentration of condensed carbon (mol/kg): (fuel oil without water C(c) = 63.3 mol/kg); fuel oil with water: 5% H2O, C(c) = 54.96; 10% H2O, C(c) = 50.45; 15% H2O, C(c) = 46.3. It is noted that the H/C ratio in the case of burning fuel oil -water emulsion is 2.26 times higher. A technological scheme for the preparation and combustion of fuel oil in the form of fuel oil-water emulsions in industrial boilers of the E-1/9-M(3) type of the Bridge Construction Detachment of the Kyrgyz Railway, Bishkek, has been developed. It has been established that when burning fuel oil-water emulsions in boiler units, the soot content in flue gases is reduced by 75% due to the developed contact surface of the interacting phases and more complete combustion of particles of fuel oil-water emulsions.