Dispersion Characteristics of the Plug Flow Hazardous Waste by Multiple Gas Jets

Abstract

In cement kilns co-processing hazardous solid wastes, the material is transported to the calciner for incineration via pipelines. When the viscous material enters the calciner in the form of plug flow, the CO and NOx emitted by the cement kiln fluctuate greatly as a result of insufficient combustion. In order to improve the dispersion of materials, avoid accumulation and make the combustion more sufficient, an experimental system was established to study the influence of nozzle system i, distance d, and pushing speed v on the dispersion characteristics.The slump test showed that the material with a sludge mass fraction of 35~40% had good fluidity. Moreover,the shape of the dispersion area was V-shape when the dispersion length was less than 4~6m and became a rectangle when the dispersion length was more than 6m. Finally,the results showed that i = 3 yielded the best effect, followed by i = 5, and i = 2 had the worst effect. In addition, d = 160 mm yielded the best effect, followed by d = 240 mm, and d = 80 mm had the worst effect. As the pushing speed v increased, the dispersion effect gradually worsened. The material that was 2 m away from the spray gun accounted for about 50% of the total. (1) The mixture containing 20%, 30%, 40%, 50% and 60% of sludge mass fraction is prepared respectively. The measured calorific value and chemical elements are studied, and their calorific values meet the minimum allowable calorific value of 11MJ/kg of hazardous waste as an alternative fuel. The slump test showed that materials with a sludge mass fraction of 35–40% had good fluidity. (2) A spray gun dispersion characteristic test system based on free turbulent jet was established.The standard flow rate of the atomizing gas source measured by the flowmeter is 1700Nm3/h, and the air working temperature reaches 100 °C. The calculated flow rate at the outlet is 96-116m/s.According to the zone of flow establishment length 86.8 mm, d is designed as 80mm, 160mm and 240mm. v is consistent with that of the piston pump, and the speeds are 33mm/s, 48mm/s, 71mm/s, 88mm/s and 105mm/s respectively. (3)The dispersion area distribution results showed that the diffusion angle was 70°. Within 4-6m from the spray gun, the shape of the dispersion area was the same as that of the single free turbulent jet, showing a V-shape. When the material was more than 6m away from the spray gun, the shape of the dispersion area became a rectangle.At the same distance and pushing speed, the dispersion lengths were the same. In addition, the half dispersion width and the distribution area of the three-nozzle system were the largest. (4) The influences of different nozzle systems i, different distances d, and different pushing speeds v on the dispersion area distribution, mass distribution, and area density distribution were studied. The results showed that i = 3 produced the best dispersion effect, followed by i = 5, and then i = 2. In addition, the effect of d = 160 mm was the best, followed by d = 240 mm, and then d = 80 mm. As the pushing speed increased, the dispersion effect gradually worsened.