What are the Factors Influencing the Drying Technology?

1/3/2014 3:27:30 PM

For a long time, the rotary dryer used in various industries in our country has adopted L-shaped lifting board structure, and the dryer machine is always in the state of low working efficiency: low output, high coal consumption, low heat efficiency, high water content of the discharged materials and difficulty in the control of water content. The factors influencing the drying process of rotary dryers can be classified into two types:

 one is the factors caused by the rotary dryer itself, including the lifting board, the rotation speed of the drying machine and the heat insulation of the dryer cylinder and the other one is the drying technology, including the flow speed of the air, the temperature of the hot air, hot blast heater, feeding granularity and the uniformity of the material feeding, the structure and property of the materials and the operation of the drying equipment. Dryer machine is a main energy-consuming machine so that we should try our best to make it reach high quality, high output and low energy consumption. Here Hongxing Machinery will talk about the factors influencing the drying effect.

(1) The flow velocity of hot air

From the heat transfer and mass transfer theory, we can know that improving the flow velocity of dry air will directly improve the heat transfer coefficient and mass transfer coefficient. Increasing the drying speed can timely change the hot air, which is conducive to the external diffusion process.

(2) The temperature of hot air

The higher the temperature of hot air is, the higher the rate of heat transfer and mass transfer will be; and on the condition of the same moisture evaporation capacity, the amount of hot air can be reduced, which will reduce the waste air hot loss. However, at present the temperature of the inlet hot air of the dryer machine used in many cement plants is very low, and even the temperature of downstream drying equipment is only about 700℃, for this reason, in a permitted range of the cylinder, greatly improving the inlet temperature of the hot air is not practicable.

(3) The feeding granularity and the uniformity of the material feeding

On the condition that the drying speed is definite, the bigger the contact area of the materials and the hot air is, the better the total drying effect will be. The smaller the granularity of the materials is, the smaller the internal diffusion resistance will be, which is conducive to improving the drying efficiency. However, this is not true of big-sized materials as they will form a film layer which will hold back the heat transfer and mass transfer of internal materials, for this reason, when drying materials, the materials should be first crushed. In addition, even material feeding is the premise of realize the flow equalization of materials, which, on one hand, can ensure the stability of the thermal load and thermal regulation of the dryer machine, and on other hand, can make the tail gas easy mastered and controlled.

(4) Hot blast heater

At present there are three types of hot blast heaters that are widely used in cement plants. In the production process, the customers should choose blast heater with high heat efficiency and stable operation according to the local resources.

(5) The structure and property of the materials

As materials with different structure and property will have different combination modes with water; and on the same drying condition, the drying efficiency will be different.

(6) The operation of the drying equipment

The stable operation temperature will be conducive to the implementation of the drying process. If the heat supply is not stable, the heat efficiency will be low.