The effect of coal-water slurries spraying method on the characteristics of gas-droplet jets

The results of experimental studies on the influence of coal-water slurry spraying methods and nozzle geometry on the characteristics of gas-droplet jets are presented. The experiments employed nozzles with internal, external, and combined mixing of the coal-water slurry and the atomizing agent, along with several variants of nozzle channel cross-sectional geometries. Two types of coal-water slurry were used. As a third component, nanodispersed carbon black was added to the slurry in the amount of 2% by mass. The difference in viscosity between the slurries was 54%. It was demonstrated that when spraying slurries using a nozzle with internal mixing, the average droplet size in the jet registration area ranges from 69.5 to 145.3 µm. For a nozzle with external mixing of the slurry and atomizing agent, the average droplet size varies from 111.2 to 144.3 µm. With the combined spraying method, the average droplet size ranges from 91.1 to 123.6 µm. The cross-shaped and three-petal nozzle channel geometries significantly affect the characteristics of the gas-droplet jet. Their use results in an average droplet size that is 17% larger compared to nozzles with round, elliptical, and rectangular cross-sections. Studies of the droplet velocities of coal-water slurries showed minimal influence of the spraying method and nozzle type. On average, for the three studied spraying methods, two slurry compositions, and six nozzles of different geometries, the velocity of the majority of identified droplets ranges from 28 to 38 m/s. The spray angle of the gas-droplet jets varies from 27° to 29°, which is typical for all three studied spraying methods of coal-water slurry.