Basis for the design scheme of spray dryer (I)

Basis for the design scheme of Spray Dryer (I)

Properties of feed liquid

The properties of feed liquid are very important to the design of spray dryer.

(1) The maximum solid content of the raw material under the available pump delivery.

(2) Surface tension.

(3) Liquid viscosity. The viscosity of materials involves the transportation method, atomizer form and other aspects. The three atomizers currently used are different in their viscosity.

(4) Thermal fluidity. Some materials are paste or paste at normal temperature; However, when heated to a certain temperature, good fluidity will appear. In case of such nature, heating equipment or thermal insulation equipment shall be added to the system. It may also be heat tracing pipe of material pipeline.

(5) Thixotropy. Some materials are also in paste form when they are still, but they will flow when they are stirred, so they can be transported smoothly. Add beating equipment or mixing equipment to the system.

(6) Type of solvent (moisture content). The moisture content of most materials is water, but there are also some chemical reagents under special circumstances, which plays an important role in the scheme of which gas is used to carry heat and moisture, or the treatment method (evacuation or recovery) of moisture content in the gas.

(7) Chemical characteristics. Special attention should be paid to the corrosivity, flammability, explosiveness, or toxic and odorous characteristics of materials and moisture before the drying scheme is determined. The determination of the system operation scheme depends largely on the chemical characteristics of materials.

(8) Material status. Whether the material to be dried exists in the form of solution or suspension determines whether it needs to be filtered before entering the atomizer to ensure normal atomization.

(9) The existing form of moisture content. The water in the material (water is the most common, take water as an example) includes combined water, crystal water or mechanical water. The energy consumed by evaporation of these water is different, and more attention should be paid when the product moisture content is strict.

(10) Liquid temperature.

(11) The heat sensitive temperature of the material. From the perspective of heat transfer, the higher the operating temperature of spray drying is, the more economical it will be. High temperature operation makes the equipment investment and operating costs more economical. However, most materials have the highest allowable temperature. The inlet temperature and outlet temperature of hot air have an impact on product quality. It is the most economical to work at the allowable temperature, which is the main basis for process design.