The Experimental Survey on the Rotary Dryer Performance: Drying of Wetted Salt from Effluent Bio Wastewater

The drying is a basic operation of enormous commercial importance in all industrial applications ranging through the food, agricultural, mining and even manufacturing sectors [1]. Modern societies need better product quality, enhanced safety practices and more environmentally benign operations as well as higher productivity, better energy yield and reduced material wastage, also [2]. As drying is certainly one of the most energyintensive stages in factories, and as most dryers operate at low thermal yield, the development of experimental investigations offers an opportunity to improve dryer operation and efficiency consequently. The investigation of various types of dryers is very difficult due to the long time delay, which means that accidental variations in the input variables can damage the process for long periods of time before they are affected in the output variables [3,4]. So, many surveys are required to remove such disturbances at an early stage [5,6]. The majorities of investigations are experimental and deal with the average hold-up and drying time for the particle movement. Other types of particle movement take into account the cascade motion resulting from the lifting action of flights and the kiln action, simultaneously [7-9]. In the some literatures the amount of size distribution of effluent NaCl crystals [5] and the air velocity of hot air [6] and ratio of feed per inlet hot air [8] is investigated. Thus the mechanistic models of rotary dryer distinguish between the flow of sodium chloride crystals in the dense phase and in the airborne phase. These later models forecast the drying time of solid crystals in each phase as well as its ideal throughput between over and under-loading conditions. On a factorial scale, after washing and centrifugation, salt crystals are dried, in most instances, in a counter-current stream rotary dryer. Transport of the salt crystals through the rotary dryer is affected by the slowly rotating shell. The slope of the rotary dryer helps the axial movement [10,11]. Within the rotary dryer, the salt grains are lifted and showered through the hot air bulk by flights. The shape and appearance of which is adapted to the material being dried. Because of the complexity and variety of the movement of salt particles within the drum, the design or scaleup of rotary dryers is often a subject of skill and experience. The published manuscripts about drying process of salt crystals are so limited [12,13]. Figure 1 shows rotary dryer as final stage in chemical process, schematically.