Measures to reduce energy consumption during the use of a dryer

Measures to reduce energy consumption during the use of a dryer

Drying is a chemical unit device that consumes a lot of heat. During the drying process, the thermal efficiency varies greatly, with a drying thermal efficiency of 20 to 50 percentage points in the general chemical industry. The main measures to improve the thermal efficiency of the drying process of the dryer are as follows:

(1) Strengthen thermal management for existing dryers. To prevent leakage of the drying medium, ensure complete combustion in the combustion furnace, and maintain a large circulating air volume as much as possible for dryers with hot air circulation.

(2) Improve the insulation of equipment. Generally, a dryer loses three to thirty percent of its heat. On the basis of measuring the heat dissipation of the dryer, measures are taken to improve the insulation of the equipment and reduce heat loss.

(3) Prevent excessive drying of the product. During the drying process, the product should be strictly controlled within the required moisture content range to avoid excessive drying and increase energy consumption.

(4) Reduce the initial moisture content of the dried material. If the dried material is a solution, the film evaporator can be used for concentration before spray drying; If the material being dried is a suspension, it can be filtered to remove most of the moisture before drying. This can reduce the thermal energy consumption per unit mass of product.

(5) Recovering the heat carried away by exhaust gas. When the inlet temperature of a convection dryer is not too high, the ratio of the heat carried away by the exhaust gas to the total heat is very large, and some can account for 40% of the total heat. The use of heat exchangers to recover the heat carried away by exhaust gases has been implemented in industry. For example, using air at 10 degrees Celsius, it is heated to 84 degrees Celsius through a waste heat recovery heat exchanger At 7 degrees Celsius, the exhaust gas can be reduced from 150 degrees Celsius to 70 degrees Celsius, recovering a quarter of the heat in the exhaust gas and saving 23 percentage points of fuel. The investment in the waste heat recovery heat exchanger can be recovered within two years. The use of "heat pipes" to recover heat from exhaust gases is also a promising method.

(6) Raise the air inlet temperature of the dryer. If the material being dried is non heat sensitive, the air temperature entering the dryer can be increased to over 650 degrees Celsius; For heat sensitive materials, it is also possible to use a higher inlet temperature of the dryer gas as much as possible while ensuring product quality. Because the higher the temperature of the gas used, the higher the thermal efficiency of the dryer.

(7) Using superheated steam drying. The drying method of using superheated steam as the drying medium and utilizing the sensible heat reduction of steam is called superheated steam drying. The steam used for drying can be recycled to reduce heat loss and improve the thermal efficiency of the drying process. In addition, the specific heat capacity of steam at constant pressure is twice that of air. Under the same drying heat load, the amount of water vapor used is only half that of air, thus improving the production capacity of the drying device. It is suitable for drying materials that emit odor during drying, materials with explosive hazards, materials containing organic solvents, and radioactive waste.