Investigation And Development On Quartz Sand Drying System Of Fluidized Bed With Inner-Bag Filter

Quartz sand is one of the most important industry materials, which has been widely used to manufacture glasswork, television screen, ceramic, computer and refractory materials, etc. For example, mixed with a set of other materials and melted, dried quartz sand can be used to make shell of the monitor. The drying of quartz sand is one of the most important procedures among various industrial processes, and the quality of dried quartz sand has a fatal impact on the quality of screen. In television screen producing process, different drying process has different effects on environment, also yields different economic benefits.At present, pneumatic drying and rotary drying are the main drying process for the dewatering of quartz sand. Pneumatic dying has some disadvantages, such as low drying capacity, high requirement of the dedusting system, serious abrasion of the pipe, etc. There also exist some serious disadvantages of the rotary drying method, such as large space and floor area occupation, high capital investment, long construction period, low volumetric thermal efficiency and serious abrasion of rotating parts. To solve above mentioned problem, this paper brings forward a new drying process, the fluidized bed with inner-bag filter which realized the drying process of quartz sand with high thermal efficiency and lower capital investment. Based on the extensive experimental investigation, this paper analyses the drying characteristics, hydrodynamic characteristics, heat and mass transfer characteristics, confirms the optimal operating parameters for industry scale system design, such as fluidization velocity, inlet temperature, bed temperature, pressure drop of gas distributor and drying time.The experiments show that moisture of quartz sand is mainly surface moisture which is easier to remove. The drying curve of quartz sand presents obvious three stages of preheating, constant drying rate and falling drying rate period, and the constant rate drying period is longer. Because the dominance of the constant drying rate period, heat and mass transfer coefficient are high, so quartz sand can be dried by higher temperature and lower humidity drying media in a short time. For fluidized bed drying, the determined value of the optimal fluidization velocity is about 0.8-1.2m/s, the residence time in fluidized bed is about 8-12min. Adopting special high temperature resistant gas distributor with 4%-5% of perforated ratio, the fluidization is good and the pressure drop is low. This paper also optimized the material of inner bags and its arrangement mode, the feasible operating velocity is 1.0-1.5m/min.m2, entirely meet the requirements of the dedusting.The author develops a calculation method for inner bag filter fluidized bed drying system taking Henan Anyang project ( undertaken by Shandong Tianli Drying Equipment Co. Ltd.) as the reference project, the author also carries out the system process and equipment design and model selection to validate the built method.The operating parameters from the industrial application show that the process presented by this paper has obvious advantages in the aspect of capital investment, floor area, operation cost. This developed technology will yield better social and economic benefits.