Design And Experimental Study On The Pastes In The Paddle Dryer System

A paddle dryer is an indirect drying equipment. Firstly, the operational principle and applied characters were introduced and the research progress about the paddle dryer technology at home and abroad was summarized. Based on that, some problems like lack of specific experimental data and more empirical for the equipment design were pointed out.Combined with these problems, a paddle dryer drying system with an area of3m2was designed, including the power part, the thermal dynamic part, the measurement part and so on. With it study on paddle dryers was conducted further through the experiments, providing the qualification for the next experiments.Drying experiments of municipal sewage sludge, textile dyeing sludge and polyethylene particles were carried out in a paddle dryer in the laboratory separately. During the drying experiments of municipal sewage sludge with the initial moisture content of80.8%, some important parameters, like the oil temperature, the speed of the paddle dryer, additives were discussed.It was concluded that with the increase of oil temperature, the drying effect was enhanced. When the speed of the paddle dryer was22.5r/min, the moisture content of the products of municipal sewage sludge as oil temperature was120℃、160℃、180℃、210℃in experiments was finally76.99%、67.73%、48.85%、39.38%separately. Within a certain range, sewage sludge had a longer period for drying at the lower speed of the paddle dryer. When the oil temperature was180℃, the moisture content of the products of municipal sewage sludge as the speed of the paddle dryer was37.5r/min、22.5r/min、7.5r/min、3.75r/min in experiments was finally51.69%、48.84%、40.84%、23.17%separately. Therefore, the products out of the paddle dryer got lower moisture contents and the smaller particles. In addition, when oil temperature was180℃, and the speed of the paddle dryer was7.5r/min, the moisture content of the products of municipal sewage sludge after drying process with mass ratio5%was36.58%, lower than40.84%without additives. And the bulk density was0.7144g/mL, higher than0.5918g/mL without additives. It was demonstrated that a better effect of drying and heat transferring was achieved by some proportion of the rice husk additives put in during the drying process from the view of definition.The drying experiments for textile dyeing sludge was performed, showing that when oil temperature was180℃, and the speed of the paddle dryer was7.5r/min, the initial sample with the moisture content84.97%was dryed to12.77%. Through the drying experiment of textile dyeing sludge, it was proved the paddle dryer was available for the drying of textile dyeing sludge. Combined with the experiments of municipal sludge sewage, it was given the instruction of the pastes drying process in the paddle dryer.The thermal and flow properties of the melt polyethylene was observed in the paddle dryer. With a good performance on thermal and flow properties, it provided another way for the use of a paddle dryer.An idea of utilizing the solar energy to heat the oil and assist the drying process was proposed. Then a parabolic trough solar collectors drying system assisted drying was designed. According to average radiation intensity in every season in Nanjing, the utilization of solar energy and the energy saving in ideal condition were calculated analyzed finally.