Dryer model

There are a number of hot-air dryer models, devices inspired by modem technology. In principle, these dryers apply hot air to expel moisture from the kernels. Since smoke does not come in contact with the kernels, the product is a cleaner and whiter copra. 

For example, Buchi minispray dryer, model 190, liquid feed rate 60ml/min, inlet air temperature 180°C, air throughput 2.4m /min, and nozzle air pressure 800kPa (116psi). 

Operating currently available freeze-dryer models is less labour-intensive also, modern equipment affords the implementation of some initial production stages. Once the few sample (melting point) and protocol data (final tray temperature) required is input by the operator following insertion of the product, the apparatus conducts an entire freeze-drying... 

General Principles Models and calculations on dryers can be categorized in terms of (1) the level of complexity used and (2) the purpose or type of calculation (design, performance rating, or scale-up). A fully structured approach to dryer modeling can be developed from these principles, as described below and in greater detail by Kemp and Oakley (2002). 

Levels of Dryer Modeling Modeling can be carried out at four different levels, depending on the amount of data available and the level of detail and precision required in the answer. 

As an example of the typical numbers involved, Matchett and Baker [J. Sep. Proc. Technol., 9 5 (1988)] used their correlations to assess the data of Saeman and Mitchell for an industrial rotary dryer with D = 1.83 m and L = 10.67 m, with a slope of 4°, 0.067 m/m. For a typical run with UG = 0.98 m/s and N = 0.08 r/s, they calculated that UPl = 0.140 m/s, VPy= — 0.023 m/s, UPl = 0.117 m/s, and Up2 = —0.02 m/s. The dryer modeled was countercurrent and therefore had a greater slope and lower gas velocity than those of a cocurrent unit for the latter, UPl would be lower and UPl positive and larger. The ratio Ts/tg is approximately 12 in this case, so that the distance traveled in dense-phase motion would be about twice that in the airborne phase. 

Kieviet, RG. and Kerhof, P.J.A.M. Air flow, temperature and humidity patterns in a co-current spray dryer modelling and measurement. Drying TechnoL, 15,1763, 1997. 

Before starting with constructing and solving a specific dryer model it is recommended to classify the methods, so typical cases can easily be identified. We will classify typical cases when a solid is contacted with a heat carrier. Three factors will be considered ... 

FIGURE 3.12 Solution of a two-dimensional cross-flow dryer model for cooling of granular solid with hot air. Solid flow enters through the front face of the cube, gas flows from left to right. Upper surface, solid temperature lower surface, gas temperature. 

FIGURE 3.18 Solution of a batch oven dryer model—solid dry mass is 90 kg, internal heater power is 20 kW and air ventilation rate is 0.1 kg/s (dry basis) external air humidity is 2 g/kg and temperature 20°C (a) moisture content X (solid line) and air humidity Y (broken... 

It is the objective of this chapter to present step-by-step procedures in order to allow application of various dryer models into the Excel environment. This chapter refers to two main topics. The principles for solution of a process design problem are presented first and then the principles for Excel implanentation are described. 

Steps 1-3 of Section 5.2 are applied and the dryer model is created on the spreadsheet process as shown... 

FIGURE 5.5 Dryer model implementation in the Process spreadsheet. 

Dynamic drum dryer models that have been developed so far can only predict the final temperature and moisture content. " These models cannot predict other important quality parameters and are only useful for steady process operation. With the advent of improved infrared technology, the moisture content can be measured by inference using infrared temperature sensors. ... 

The equation system describing the dryer model for a given elementary layer of the bed [25,125,131] is as follows moisture mass balance for the material. 

---