Pinchuk V. Development of scientific basis of coal-water fuel combustion and working out of methods of it activating to improve combustion efficiency

The dissertation is devoted to the study of properties and processes of ignition and combustion of coal-water fuel which was produced from high-ash and/or low-reactive coal and to the development of the fuel pre-activation methods and devices for efficient replacement of natural gas at power plants. The dependencies of thermal conductivity and thermal capacity values of coal-water fuel, which produced from coal of different metamorphosis stages, on percentage parts of water and coal phases in fuel suspense and the amount of mineral impurities, are deducted in experimental research within temperature range 40…200 C. It is shown, that thermal conductivity coefficient varies from 0.4 to 0.8 W/m K, and thermal capacity varies from 3.6 to 6.5 kJ/kg K. The regularities of influence of various physical and chemical parameters (i.e. the temperature range of combustion chamber was 550…1000 °C, volume of water phase in the fuel was 25…50 %, range of mineral impurities amount was 0.5…60 %, fuel drops diameter varies from 0.5…5 mm, etc) on the combustion process characteristics (i.e. heating rate and time, parameters of volatiles burning process, rate and time of afterburning the coke residue) are established by experimental research. The empirical equations for physical and chemical processes, which are presented at each stage of coal-water fuel combustion, are obtained The method has been developed, with the help of which the estimation of power potential of Ukrainian coals has been carried out. The correlations between coal formation enthalpy and values of mineral impurities and water, contained in the coal, are obtained. These correlations involve features of organic structure of coal. This allowed to determine the effective ways for coal activation. It is established, that coal formation enthalpy varies from -4000 kJ/mol (-1859 kJ/kg) for brown coal (lignite) to +250 kJ/mol (+117kJ/kg) for anthracite.The regularities of particular and complex influence of thermal, chemical and electro-magnetic coal-water fuel activation parameters on time-temperature characteristics of fuel ignition and burning processes are obtained in the experiment. It is established that the ignition time decreases by 5…35 %, firing drop temperature increases by 5…20 %, burn-up degree raises by 5…22 %. At the same time ignition and burning processes are stable. Electrical properties of coal-water fuel produced from coals of different metamorphosis stages are obtained experimentally. The method for definition of optimal electromagnetic field parameters for effective activation and mixing of fuel is developed. Effective technical and technological solutions for pre-activation and thermal preparation of coal-water fuel are carried out on the basis of obtained results. These solutions allowed using maximum value of physical and chemical fuel potentials. The solutions, which were proposed, are used in industry. A method and equipment for an integrated activation of coal-water fuel before to combustion were developed. These method and equipment were implemented into the process of coal-water fuel preparation. A cyclone pre-furnace with capacity of 1 MW was developed, and operational parameters for the combustion of coal-water fuel in it were proposed. Recommendations and operation lists for the process of fuel change from natural gas and/or fuel oil to coal-water fuel combustion at steam boilers of low and medium power capacity were worked out and implemented in a boiler room.