Impact of Hydrodynamic Cavitation on the Properties of Coal-Water Fuel: An Experimental Study

It is common to use coal as raw material in heat power engineering. A number of shortcomings of coal such as ignitability cannot be easily eliminated. The use of water-slurry-based coal-water fuel instead of coal eliminates this problem. The coal-water fuel (CWF) is liquid fuel, which means that the main line of investigation is to study its sedimentation and rheological properties responsible for the transport and atomization in the boiler and thermal-physical properties which determine the expedience and efficiency of its application. The paper shows that the final performance properties of suspended coal fuel can be determined at the stage of CWF preparation by hydrodynamic treatment of aqueous coal slurry. The rheological and sedimentation properties and combustion parameters of water-coal fuel, ignition time of the drop, its completeness of combustion, and amount of man-made emissions, have been studied. Studies have been carried out on coals from the Kansk-Achinsk coal basin (Russia). The studies were performed under laboratory conditions with a hydrodynamic rotary mixer, making it possible to attain cavitation effects in the processed medium. Two CWF types have been considered: the first was produced by cavitation dispersion of the solid coal fraction in distilled water, and the second was produced in analogy, but the dispersion medium was water pretreated by cavitation. The paper shows that the cavitation method of producing CWF improves the rheological and sedimentation properties of the end-use fuel, reduces hazardous emissions in combustion, and affects the combustion parameters.