Drying equipment drying rate influencing factors and drying equipment classification

Drying equipment drying rate influencing factors and drying equipment classification

I. Drying equipment drying rate 1. Drying equipment drying rate

1. Unit time and unit area, the weight of the material lost, known as the drying rate. 

2. drying process

(1) the beginning of the period: the time is short, for the material will be adjusted to the same situation with the dryer.

(2) Constant speed period: this is the drying rate ^ a period of time, the material surface evaporation of water, the internal just enough to replenish, so the surface of the water

(3) Deceleration of a period of time: at this time of evaporation of water, the internal can not be completely replenished, so the surface of the water film began to rupture, the drying rate began to slow down, the material is called the threshold in this point, the water contained at this point, known as the critical water.

(4) Deceleration of the second phase: only dense materials in this phase, because the water is not easy to come up; but the porous material is not. The evaporation of water in the first period is mostly carried out on the surface, the water film on the surface of the second period is completely gone, so the water is diffused to the surface in the form of water vapor.

II. Factors affecting the rate of constant speed drying

1. Air temperature: If the temperature is increased, the rate of diffusion and the rate of evaporation of water are increased. 2.

2. Humidity of air: at lower humidity, the evaporation rate of water becomes larger. 3.

3. velocity of air flow: the faster the velocity, the better the effect of mass and heat transfer.

4. Shrinkage and surface hardening: both phenomena affect drying.

III. Classification of drying equipment

Excess water should be removed as far as possible before the material enters the equipment.

1. Dryers for solids and pastes

(1) Plate dryer

(2) Sieve transport dryer

(3) Rotary dryer

(4) Screw transporter dryer

(5) Ride-on dryer

(6) Stirring dryer

(7) Rapid evaporation dryer

(8) Cylinder dryer

2. Solutions and slurry water using thermal evaporation to complete drying

(1) Drum dryer

(2) Spray dryer