Drying equipment drying rate influencing factors and drying equipment classification

Abstracts:

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 initial period: a short period of time, for the adjustment of the material to the same situation as 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 film is still in, and maintained at the wet bulb temperature.

I. 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 period: 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 large period, the material surface evaporation of water, the internal just enough to supplement, so the surface of the water film is still in, and maintained at the wet bulb temperature.

(3) Deceleration of a period of time: at this time the evaporation of water, the internal can not be completely replenished, so the surface water film began to rupture, the drying rate also began to slow down, the material at this point is called the critical point, the water contained at this time, 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, and the water film on the surface is completely gone in the second period, so the water diffuses to the surface in the form of water vapor.

II. Factors affecting the rate of constant speed drying

1. the temperature of the air: if increase the temperature, the diffusion rate of sweat water evaporation rate are increased. 2. the humidity of the air: at lower humidity, the water evaporation rate becomes larger.

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

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

4. Shrinkage and surface hardening: these two phenomena will affect drying.

III. Classification of drying equipment

Materials should be removed as much as possible from excess water before entering the equipment.

1. Dryer for solids and pastes

(1) Disc dryer

(2) Sieve transportation dryer

(3) Rotary dryer

(4) Screw conveyor dryers

(5) Ride-on dryers

(6) Stirring dryers

(7) Rapid evaporation dryers

(8) Cylinder dryer

2. Drying of solution and slurry water by thermal evaporation

(1) Drum dryer

(2) Spray dryer