Pefrormance Research Of Pulsed Pneumatic Dryer For Coal Fly Ash

Coal fly ash is a kind of residue generated after the completion of pulverized coalcombustion. It has the similar quality with cinerite ash, which has a high use value inengineering. In china, the coal fly ash’s utilization ratio is low, a large amount of them hasbeen accumulated in yards without any attention, so it always be nicknamed the ‘misplacedresources’. At present, the whole society work hard to build a conservation-minded society,people also pay more attention to the reuse of coal fly ash. In practical engineering, peoplealways want to deal the processing, storage or transportation of coal fly ash with the conditionof dry powder, and many comprehensive utilization projects must use dry powder. While thecoal fly ash expel from the smoke are wet ash having a lot of moisture. So the coal fly ashmust be dryed before use. By considered the characteristics of coal fly ash, this topic willapply the pneumatic dryer in coal fly ash drying. The research results can not only optimizethe production of coal fly ash, but also can enlarge the application scope of pneumatic dryers.Pneumatic drying is one of the many dry methods, which is widely used in industrialproduction. Considering the coal fly ash’s characteristics and comprehensive performance ofpneumatic dryers, the pulsed pneumatic dryer was chosen. The pulsed pneumatic dryer wasdeveloped by the older research scholars in china in the1960s based on the straight tubepneumatic drying technology. It not only inherited the merits of the previous dryingequipment, but also can show its own advantages. By using the ranging in diameter tubestructure, the dryer can strengthen the heat transfer process between two-phases inside thedryer, cause an excellent effect on the powder material drying.Contraposing the coal fly ash, this topic designed the pulsed pneumatic dryer for coal flyash. Based on the CFD theory, the simulation and optimization of the gas-solid two-phaseflow and heat transfer process was conducted. First of all, the air flow without particles wassimulated, and the flow characteristics have been gotten. The results showed that the flowfield within the dryer is regular, and the air’s velocity change effect is obvious. Secondly, thecoal fly ash particles were injected into the dryer, the relative velocity and heat transferprocess between the gas-solid two phases have been gotten. The results showed that theranging in diameter tube can reinforce the convection process between air and particle, thefinal average moisture content of the particles is able to achieve the demand of engineeringapplication. Both the effect and the performance of the dryer are satisfactory. The movementof particles injected from different position is uncertain, which can ensure the uniformity ofdrying. Due to the low heat transfer process inside particles, particles with larger diametershow poorer drying effect, though their stay time is longer. Finally, by using indexes includepressure loss and particles’ moisture content to analyze the flow and heat transfercharacteristics, the influence of different structural and operating parameters on the dryingprocess was studied. The results showed that, the pressure loss value increases with theincrease of the ratio of pipe diameter, also increases with the increase of inlet velocity andfeed rate. The effect of the air temperature on the pressure drop value is very small. With theincrease of transition angle and diameter ratio, particles’ final moisture content decreases. The final moisture content also decreases with the increase of air temperature, but increases withthe increase of air velocity and feed rate.