Quasi-hot spraying of coal-water slurries with pyrogenetic water additives

Abstract

Experimental results of the influence of thermal preparation of coal-water slurries on their rheological properties and spraying characteristics are presented. The slurry density was found to increase by 14% at a temperature of 293 K with the substitution of water in coal-water fuel with a similar by weight amount of pyrogenetic water (no more than 25%). Preliminary thermal preparation of coal-water slurries up to 333 K reduces its density by 7%. The experimental results showed that the greatest influence of thermal preparation of the studied slurries on their dynamic viscosity is characteristic of the temperature range from 293 to 323 K. At such temperature values, a decrease in the slurry viscosity is by 17–20% in comparison with two-component coal-water fuel. Preheating of slurries before spraying, in the temperature range from 293 to 333 K, makes it possible to increase the jet spraying angle by 21–29% compared to conventional two-component coal-water fuel at a temperature of 293 K. The velocity of droplets of the investigated coal-water fuels in the range of changes in their initial temperature from 293 to 333 K varies slightly. The difference is no more than 5%. Increase in the pyrogenetic water concentration in coal-water fuel of more than 25% by weight is impractical for lignite due to the dramatic increase in its viscosity. In the studied range of the third component concentration of the slurry, increase in the average size of fuel droplets is about 8%. Preheating of CWF before spraying can significantly reduce the average size of the droplets. The changes are 5–9% in comparison with coal-water slurry at a temperature of 293 K. Thermal preparation of slurries, according to the results of thermal imaging studies of coal-water fuel jet, affects the thermal contour of the jet and the geometry of its temperature zones.