Drying equipment, also known as dryer. The equipment used for the drying operation is vaporized by heating to wet the moisture (usually moisture or other volatile liquid components) in the material to obtain a solid content of the specified moisture content. The purpose of drying is for the purpose of material use or further processing. Such as wood in the production of wood mold, wood before the drying can prevent the deformation of the product, ceramic billet in the calcination before drying can prevent the finished product cracking. In addition, the dry material is also easy to transport and storage, such as the harvest of food to a certain moisture content below, to prevent mildew. As the natural drying can not meet the needs of the development of production, a variety of mechanized dryer more and more widely applied.
Since ancient times, humans are accustomed to using natural heat and natural ventilation to dry materials, completely subject to natural conditions, low production capacity. With the development of production, they are gradually replaced by artificial controlled heat sources and mechanical ventilation dehumidification means.
In the early 20th century, dairy production began to use spray dryer, for large-scale dry liquid material provides a powerful tool. From the beginning of the 1940s, with the development of fluidization technology, high-intensity, high-productivity ebullated beds and airflowers have emerged. While the frozen sublimation, radiation and dielectric dryer to meet the special requirements to provide a new means. 60 years began to develop far infrared and microwave dryer.
Drying equipment in the petrochemical enterprises in the application is very common, is for the petrochemical business services, therefore, by the industry economy is relatively large. Petrochemical industry as a whole is not optimistic about the economic operation of the drying equipment industry is a challenge. Really affected by the greater impact of small businesses, large enterprises have not been much affected, and some large enterprises only profit margins narrowed some of the output and did not decline. This shows that the ability to resist the impact of large enterprises stronger than small businesses.
Drying equipment, science and technology content of the first show a leading role. Since 2004, by the national chemical development situation continued to drive, drying equipment market situation is stable, manufacturers generally get a better business performance. Drying equipment services The remarkable feature of the chemical industry is that the role of technology is becoming increasingly prominent. This is mainly different from the past, selling products mainly by price competition. Among them, some high-tech equipment, focusing on the development of new products manufacturers, the benefits of increasing; the contrary, some products with low technological content, new products and new technology development capacity of weak enterprises, efficiency began to decline.
Market reaction shows that the chemical industry is looking forward to drying equipment manufacturing industry in accordance with high quality, low energy consumption, environment-friendly requirements to adjust the product structure, to further strengthen the basic research, reinforce the basis of application development. In the technical aspects, to strengthen the automation, testing, manufacturing process and material design and other aspects of the design. In the application of research and development, it is necessary to pay attention to international exchanges and cooperation, but also pay attention to the protection of intellectual property rights; both to focus on new technologies, new application areas of development, but also focus on traditional crafts and traditional applications of innovation and innovation.
Drying process requires a lot of heat, in order to save energy, some high moisture content of materials, containing solid substances in the suspension or solution generally first mechanical dehydration or heating evaporation, and then dry in the dryer to get dry solids.
In the process of drying, it is necessary to complete the transfer of heat and mass (moisture) at the same time to ensure that the moisture partial pressure (concentration) of the wet surface of the material is higher than that of the moisture in the external space to ensure that the heat source temperature is higher than the material temperature.
The heat is transferred from the high temperature heat source to the wet material in various ways, so that the surface of the material is wet and vaporized and escaped into the external space, resulting in a difference in moisture content between the surface and the inside of the material. The internal wet to the surface diffusion and vaporization, so that the material wet content continues to decrease, and gradually complete the dry material as a whole.
The drying rate of the material depends on the rate of surface vaporization and the diffusion rate of internal moisture. The drying rate and the surface temperature of the material are kept stable as long as the dry external conditions are constant. This stage is called constant speed drying stage; when the wet content of the material is reduced to a certain The rate of diffusion of the internal moisture to the surface decreases and is smaller than the rate of surface vaporization. The drying rate is mainly determined by the internal diffusion rate and decreases with the decrease of the wet content. This stage is called the deceleration drying stage.
In addition, technological progress will also reverse the current domestic export situation of drying equipment. China's drying equipment has not yet formed the scale of exports, export volume is less than 5% of the total, and mainly sold to Southeast Asia. However, according to authoritative forecast, with the development of technology, China's exports of dry equipment in the next few years the proportion of total output will be increased from 5% to 10%, export market will also expand from Southeast Asia to Europe and the United States. Domestic large-scale drying equipment manufacturing and international level there is a big gap between the situation is expected to improve.