Influence of cavitation treatment on the properties of coal-water slurries with pyrogenetic liquid and characteristics of their atomization by a pneumatic nozzle

Abstract

Experimental studies were conducted to investigate the rheological properties and atomization characteristics of coal-water slurries sprayed by a pneumatic nozzle with addition of pyrogenetic liquid. The research object was coal-water slurries prepared on the basis of long-flame coal using a rotary hydrodynamic cavitation generator. The dynamic viscosity of samples was investigated using a Reotest-2 rotary viscometer. The droplet size of atomized slurries was determined by the interferometric particle imaging method. A pneumatic nozzle designed for spraying of coal-water slurry fuels was used. The calorific value of coal-water slurry compositions was estimated by a theoretical method using Mendeleev's equation for calculating the lower heating value of combustion of organic substances with a certain elemental composition. It was found that cavitation treatment of a two-component coal-water fuel for 90 s leads to a 48% decrease in its viscosity. It was shown that substitution of water with a similar amount of pyrogenic liquid (5 to 20%) leads to an increase in the viscosity of coal-water fuels. The cavitation treatment of such slurries reduces the viscosity of the respective three-component coal-water fuels by 27–45%. According to the results of static sedimentation studies, coal particles start to precipitate 24 h after the onset of cavitation treatment. The treatment of the slurries under consideration for 27 and 90 s in a rotary hydrodynamic cavitation generator was established to reduce the average droplet size in the jet after spraying with a pneumatic nozzle by 5.5% and 6.5%, respectively. The introduction of pyrogenetic liquid into the composition of coal-water fuels increases their calorific value by 6.9%. It can be concluded that the use of pyrogenetic liquid in the composition of coal-water slurry fuels followed by their treatment in a rotary hydrodynamic cavitation generator can solve the problem of low reactivity of coal-water slurries.