Study On Drying Characteristics Of Metallurgical Dust Ash Pellets And The Drying Numerical Simulation Of Chain Dryer

Carbon pellet rotary hearth furnace direct reduction technology is the disposal technology of metallurgical dust is more reasonable,and is dry pellets into rotary hearth furnace reduction before the indispensable link,the drying process of pellets,directly affect the quality of the pellets and output at the same time,the drying process is the main energy of pellet production link,therefore,to improve the pellet drying process is advantageous to realize the energy saving of pellet production process,improve the yield and quality of the product.In this paper,by adopting the combination of experiment and numerical simulation methods,studying the characteristics of pellet drying and the influence factors of chain dryer drying process,the pellet chain dryer design,debugging and production has practical significance.Metallurgical dust ash pellets containing carbon of some factory as the research object,and established a single carbon pellet drying process mathematical model.Considered in the model the pellet drying in the process of heat transfer,mass transfer,porosity,and the change of physical parameters,and has set up a platform carbon pellet drying experiment,experiment of weightlessness carbon-containing pellets were measured,the experimental results and the model calculation are in good agreement,shows that the mathematical models of single ball is reliable.The calculation results show that the pellet drying characteristics is shown as: pellet drying process is mainly divided into rise rate drying and falling rate drying in two stages,has not been constant speed drying stage,and shorter acc drying stage.At the same time analyzed the air temperature,wind speed,pellet moisture content and pellet diameter on the influence of pellet drying,found for pellet drying air temperature,wind speed,air temperature is higher,the pellet drying rate,the greater the shorter drying time,air temperature from 150 ℃ to 150 ℃,the drying time nearly in half,blast temperature above 200 ℃,wind speed more than 1 m/s,the pellet drying effect is good;And pellet diameter and moisture content while also affect the drying process,but because in the process of pellet production,moisture content is too high or too low,the diameter is too big or too small are not conducive to into a ball,the pellet diameter and the moisture content change is not big.Therefore,the actual drying process generally by adjusting wind speed and wind temperature to shorten the drying time,improve the efficiency of drying.In material layer in the chain dryer were analyzed in detail,on the basis of drying process,with a single carbon pellet drying mathematical model as the foundation,set up a chain dryer drying process of multiple layers in mathematical model.In the model not only considers the carbon-containing pellets drying process of heat transfer,mass transfer,porosity,and the change of physical parameters,also considering the machine speed and pellet layer between the moisture condensation,heat dissipation and other factors.Discrete implicit difference method is used to control equation,the discrete equation of solving the alternating direction implicit algorithm,and use the pellet factory to provide the actual production data of the model is verified,the results showed that the paragraphs of the maximum error between simulated values and production values in not more than 10%,that model is suitable for the actual production.The chain dryer model shows that the blast segment,material layer temperature decreases with the increase of the height,the humidity decreases gradually with the decrease of the height;Convulsions segment,the bed temperature increases with the increase of altitude,humidity,decreases gradually with the increase of the bed height,and to convulsions section at the end of the dry basically completed the task.And the drying air temperature,wind speed and movement speed chain grate bed dryer parameters are optimized,the optimization of rear drum wind before pelletizing temperature and optimization is relatively close,and convulsions section 53 K pellets temperature,the drying rate increased by 12.5%.