Establishment and solution of heat recovery and dust removal model of the upperspraying device attached to a mine fan diffuser

Mine exhaust air contains a large amount of low-temperature heat and dust.Using the spraying device attached to a mine fan diffuser,the heat energy of mine exhaust can be recovered and the dust in the exhaust can be captured.Aiming at the heat and mass transfer problems among air exhaust, rising droplets and falling droplets, as well as the problem of dust removal by droplets in the upper spraying device attached to a mine fan diffuser, a heat recovery model and a dust removal model were constructed and validated.Using the fourth-fifth-order Runge-Kutta algorithm on the MATLAB platform, the constructed models were solved, and the distributions of air temperature, humidity, droplet temperature, droplet velocity, Reynolds number, heat transfer coefficient, mass transfer coefficient and dust concentration along diffuser height were determined.Also, the trajectories of dusts of different diameters around a single droplet were determined.The research results show that the heat transfer coefficient and mass transfer coefficient of rising droplets first decrease and then increase during the droplet ascending process, while the heat transfer coefficient and mass transfer coefficient of falling droplets gradually increase and become stable during the droplet falling process.The temperature change, heat transfer coefficient and mass transfer coefficient of rising droplets are smaller than those of falling droplets, indicating that the contribution of rising droplets to heat recovery is less than that of falling droplets.The heat and mass transfer above nozzles is better than that below nozzles, so to improve thermal performance, the heat transfer area above nozzles should be extended.When the relative velocity between gas and liquid increases, the dust removal efficiency of a single droplet increases.Owing to the influence of the relative velocity between gas and liquid, the contribution of falling droplets to dust removal is greater than that of rising droplets.The smaller the dust diameter, the faster the dust concentration variation rate near the maximum droplet rising height.The dust removal efficiency increases with the increase of dust diameter.The dust removal efficiencies of 2.5, 5.0 and 10.0 μm dusts are 29.2%, 73.4% and 87.6%, respectively (air velocity 4 m/s, droplet diameter 1.7 mm, droplet initial velocity 6.5 m/s, liquid to gas ratio 0.56).The establishment and solution of the model build a theoretical foundation for the performance evaluation, characteristic analysis, parameter design, and operation management of the upper spraying device attached to a mine fan diffuser.