Natubhai V. Patel College of Pure & Applied Sciences (N. V. P. A. S.) Baria Nikunj S. Roll No. – 338. T.Y B.Sc. IC

 INTRODUCTION  FACTORS  TYPES OF DRYER  WORKING

Drying is commonly the last stage in a manufacture process. Drying is the final removal of water from material (usually by heat) Purposes of drying 1. To avoid or eliminate moisture which may lead to corrosion. 2. To improve or keep the good properties of a material. 3. To reduce the cost of transportation of large volume material 4. To make the material easy or more suitable for handling.

Gas velocity : the rate of gas velocity increase than the rate of drying will increase. Humidity of gas: lesser the humidity higher the rate of drying. Area of drying surface : rate of drying increase than the area of drying surface expose to the hot water. Temprature : if you increase the temprature driving force increase.

Drum dryer Rotary dryer Tray dryer Tunnel dryer Spray dryer Flash dryer

It consists of a drum of up to 1.5 m in diameter and 2-4 m in length, heated internally, usually by steam, and rotated on its longitudinal axis. Operation: The liquid is applied to the surface and spread to a film, this may be done in various ways, but the simplest method is that shown in the diagram, where the drum dips into a feed pan. Drying rate is controlled by using a suitable speed of rotation and the drum temperature. The product is scraped from the surface of the drum by means of a doctor knife.

Here, in rotary dryer feed is continuously passed to the drum and from other side fresh air is inleted this air is heated by heater which is kept to the inner side of the drum. After it feed is directly contacts with this hot air and this hot air exerts the water molecule from feed. Then air becomes moistured again. This moistured air then goes to the outside from outlet. And dryed product goes to the tank which is jointed with drum.

Tray dryer: In Fig. of tray dryer, Air flows in direction of the arrows over each shelf in turn. The wet material is spread on shallow trays resting on the shelves. Electrical elements or steam-heated pipes are positioned as shown, so that the air is periodically reheated after it has cooled by passage over the wet material on one shelf before it passes on the next.

Here in fig of tunnel dryer it is shown that the heavy vehicles like truck or trays are passed from the tunnel. Material which we have to dry is putted on the surfaces of these trays. This material than contacts with the heated air so it removes the moisture content of material and we can get the dried material at other side.

We conclude the purpose of drying, factors of drying and types of dryer as we ll as it’s working.