Drying of particles

Example 19 Drying of Particles A convective dryer is to be used to dry 720 kg/h (0.2 kg/s) of particulate material from 0.2 to 0.02 kg/kg moisture content (all flows and moistures on dry basis), using air at 180°C and 0.005 k kg humidity. Estimate the required air flow rate and dryer size for a fluidized-bed dryer (0.5 m/s inlet velocity) and a pneumatic conveying dryer (20 m/s inlet velocity). Assume outlet RH is approximately 20 percent. What is the effect of 10 percent heat losses ... 

Hosseinalipour, S.M. and Mujumdar, A.S. 1996. A model for superheated steam drying of particles in an impinging stream dryer. In Mathematical Modeling and Numerical Techniques in Drying Technology (I.W. Turner and A.S. Mujumdar, Eds.), Marcel Dekker, New York. 

Used for drying of particles Air/combustion gas as drying medium... 

FIG. 39 Various structures obtained by drying of particle monolayers (a) the two-dimensional liquid-solid interface (latex particles/mica) (b) the caterpillar structure (latex particle/mica) (c) the labyrinth structure (melamine latex particles/mica). 

Mescher, A., Kamplade, J., Walzel, P. (2013). Spray drying of particles with narrow PSD by LAMROT atomizer and optimized gas distributor. In 25th Annual Conference on Liquid Atomization and Spray Systems HASS, September 1-4,2013, Chania, Greece. 

The thickness of dry developer s layer is substantially smaller in a zone imbibed by a penetrant due to the process of particles sedimentation. Reduced thickness h of imbibed zone can be 80% smaller than the thickness h of dry one. It must be taken into account in the calculations of PT characteristics in the frame of the theory [1-3]. 

The circular cross section of the polymer blobs does not prove that the polymer existed in solution as a tangled coil (although this is the case). The shape displayed by the particles in the photograph is probably due in part to surface tension occurring during the drying of the sample. 

Plant capacity is a function of feed size distribution and Hberation. Separators can accept a size range as wide as 50—1000 p.m. Capacities are typically 1000 2500 kg/(h-m) based on rotor length which could be up to 3 m and have dia 150—250 mm. The feed should be as dry as possible because moisture interferes seriously with separation. Heaters are usually provided before the feed enters the charged field. Final cleaning is often conducted in electrostatic-type separators. Electrostatic shape separation, a newer form of ion bombardment separation, involves separation of particles based on shape and density without consideration to conductivities (37). 

The availabihty of spray-dried lactose, microcrystaUine cellulose, and other excipients allows for the use of granular rather than powdered phases. This eliminates some of the problems of particle segregation according to size (demixing) and even flow to the die. Direct compression eventually may be the preferred method of tablet preparation. 

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