At present, there are two types of drying equipment used in China's dye industry: the first type is the drying equipment imported from abroad in the early years, and the second type is the domestically designed drying equipment and the drying equipment left behind in the early years. The technical level of the drying equipment of the older dye factory is quite different, and there are both advanced equipment and relatively backward. The newly built dye factory equipment is generally better. From the perspective of development, since China's accession to the WTO, the export volume of textiles will increase significantly, and the output of dyes will continue to increase. In addition, dye manufacturers are decreasing year by year, but the output is getting larger and larger, which indicates that the production scale of single-type dyes is expanding, which leads to the development of drying equipment. Taking spray drying as an example, most of the evaporation water volume was less than 200kg/h ten years ago, and the diameter of the dryer was no more than 3m. Now, the diameter of the equipment can reach more than 6m, and the evaporation water volume is about 1000kg/h. The diameter of the flash dryer is also 1.4m, and the amount of evaporated water is above 800kg/h. The formation of monopolized monochromatic production of dyes and the continuous expansion of production scale have also objectively promoted the development of drying equipment in the direction of large-scale.
In recent years, the development of drying equipment has been focused on the development of combined dryers, and efforts have been made to optimize the combination of existing dryers to take advantage of each dryer. Combined multi-stage dryers have the following advantages over single-stage dryers:
1 combination dryer is easier to save energy;
2 combination dryer is easier to ensure product quality, the drying process can be grading, pulverizing and other operations at the same time, the heat sensitive material can be cooled in time after drying;
3 The operation is more flexible, and the various dryers can be scientifically combined according to the specific law of material drying.
The combination of dryers has the following aspects:
1 combined dryers combining various drying methods, such as spray-fluidization dryers;
2 combined dryers combined with various heat transfer processes, such as film-fluidized bed dryers;
3 multi-stage dryers of the same type, such as multi-stage air dryers.
However, there are many problems in the manufacture of drying equipment, mainly due to the fact that equipment manufacturers do not understand the processing technology of dyes. Dye drying is a highly technical process, with a wide variety of raw dyes and complex commodity specifications. In recent years, dye drying has become more and more difficult. For example, in the past, most of the disperse dye strength of the product required 100%, and now 200% is required, which means that the amount of the additive added is reduced and the heat resistance of the dye is also decreased. If the quality of the processing formula is not good, the drying will be more difficult.
Drying equipment factories often need dye factories to provide physical and chemical indicators of the materials to be dried. If the dye factory has no corresponding experience, the parameters provided are difficult to guarantee. This causes troubles in the design and manufacture of the dryer. The author has seen some unsuccessful examples. On the surface, it is a device problem. The essence is that the designer does not understand the process parameters of the dye drying process. The research on the drying process should be strengthened.