Tunnel Dryer

Tunnel dryer: 

Tunnel dryer is a direct continuous type of dryer. It is a largest scale dryer.

Principle: In this dryer, the materials to be dried are sent to the air heated tunnel for drying purpose. The material is entered at one end and the dried material is colleted at the other end of the tunnel. The outgoing material met the incoming air to ensure maximum drying and the out going air contacted the wettest material so that the air was as nearly saturated as possible.

 Mechanism of action: One of the doors of the tunnel is opened and the materials to be dried are placed to the trolleys and trucks are pushed slowly in the tunnel and then door is closed. Hot air is circulated and passed through the rail truck and perforated trolleys. The hot air then followed are recirculated with the help of fans and the material becoming dried. The moist air is passed out through the exhaust after completion of drying. The door is opened and the trolleys are taken out of the funnel and some new trolleys with the wet materials are introduced into the trucks and the process is repeated.

Application:

1. In research laboratories and QC department for drying glass wires and small apparatus.
2. In drying of packaging materials plastic caps, spoons, injectable vials, glass containers, etc.
3. In sterilization of containers.

Advantages:

1.    Comparing with the compartmental dryers tunnel dryers has the advantage of continuous operation.

2.    A large amount of materials can be dried.

3.    Tunnel dryers are used for drying of paraffin wax, gelatin, soap, pottery, etc.

Disadvantages:

1. High labor cost for loading and unloading.
2. Thermolabile substances can’t be dried.
3. Drying rage is slow, so time consuming.
4. It is not suitable for small scale production.
5. It is a non-agitated process.
6. Drying of liquid materials is not possible.
7. There is a chance of accident when doors are opened before stopping the hot air circulation.