Technical status and future development trend of drying equipment

With the joint efforts of engineering and technical personnel in drying industry, drying equipment in China has made great progress in recent years The structure and performance of the dryer have been improved obviously, and the quality is also improving constantly Some models have been sold abroad In this paper, the technical progress of drying equipment in China in recent years is described, and the existing problems are also pointed out This paper analyzes the development of production technology in various industries in the future, puts forward suggestions on how to meet the production demand of drying equipment, looks forward to the future trend of drying equipment, and provides reference for technology and equipment development 1 The technical status of drying equipment in recent years, with the rapid development of China's industrial and agricultural production, the demand for drying equipment is growing, and the overall level of drying equipment is also constantly improving Conventional drying equipment can basically meet the needs of production, and some models are exported to foreign countries These gratifying achievements are the result of the long-term efforts of the majority of engineering and technical personnel The progress of drying equipment is shown in the following aspects: (1) processing quality of drying equipment From the manufacturing process of drying equipment, the processing quality of drying equipment is restricted by technical level and application industry There are many application industries of drying equipment, and the pharmaceutical industry has high requirements for equipment quality Due to the particularity of the pharmaceutical industry, there are specific requirements for the material, structure and processing quality of the drying equipment used, so the equipment provided by the manufacturing industry is required to have high processing quality Secondly, the food industry has strict requirements on the drying equipment and drying system, so the equipment structure and steel processing standards are high The relatively low quality requirements are part of the equipment in the production of chemical industry In all industries, the chemical industry is more complex in terms of equipment consumption and type It should be said that the drying equipment in the chemical industry has special requirements, but it is slightly lower than the above two industries Judging from the total quality of Zui drying equipment in recent years, most of the equipment steel plates have been polished, argon arc welding (stainless steel) has been used for the weld, and the weld has also been treated Some factories use automatic or semi-automatic welding for straight weld and girth weld to ensure the quality of the equipment In the visited factories, Changzhou Daming Pharmaceutical Equipment Co., Ltd and Changzhou Qile Machinery Equipment Co., Ltd have good processing quality (2) With the introduction of drying equipment in China and the international technical exchange, the structure of drying equipment in foreign countries is constantly affecting our country Zui's new models and structures in recent years are mainly as follows: 1 Internal heat pipe type fluidized bed dryer: this kind of dryer has changed the way that the heat of the fluidized bed was all brought in by the hot air in the past Through the internal heat transfer tube, part of the heat came from the conduction and heat transfer of the heat medium in the tube, thus greatly improving the thermal efficiency According to the data, the thermal efficiency of the traditional fluidized bed is 39.7%, while that of the internal heat pipe is 72.5% Under the same production, the bed area is reduced from 72.5 ㎡ to 14.42 ㎡ Sulzer company in Switzerland and Nara Machinery Manufacturing Institute in Japan have such equipment The heat medium is generally steam, heat-transfer oil, etc ② Tube bundle dryer: the shell and transmission mode of tube bundle dryer are very similar to that of rotary dryer, but 1-5 layers of tube bundles are arranged concentrically inside The tube bundle passes through the whole length of the dryer and is filled with water vapor or other heat medium for conduction and convection heat transfer It has high thermal efficiency and the total heat transfer efficiency can reach 80% - 90% It is especially suitable for drying materials with temperature below 150 ℃ ③ Flash dryer: as a drying equipment introduced into China in 1989, it has the ability to process viscous filter cake materials and can directly obtain powder materials It is suitable for drying some low viscosity mineral filter cake and chemical intermediates ④ Paddle dryer: in 1990, paddle dryer was first introduced into China by Beijing dye factory for drying indigo dyes The main type of paddle dryer is traditional heat transfer The big advantage of Zui is high heat transfer efficiency and continuous production ⑤ Disc dryer: in the early 1980s, Shanghai Chemical Equipment Institute began to develop this technology, but due to various reasons, the equipment was not widely used In recent years, a number of domestic drying enterprises have begun to develop this technology, which is basically mature up to now, and there is some progress in theoretical research of this type of machine ⑥ Vibrated fluidized bed dryer: this type of dryer increases the structure of controlling the running speed of materials, the distribution of hot air is more reasonable, and can effectively prevent material leakage Compared with the ordinary vibrated fluidized bed, the area evaporation intensity is greatly improved ⑦ Tank type agitation dryer: Japan limamoto Iron Works Co., Ltd was developed earlier In the tank type dryer, the structure of the original agitation material is composed of pipe fittings which are connected with steam, so that the material can be stirred and the heat can be transmitted ⑧ Through flow rotary dryer: in a rectangular box, a porous rotary cylinder is installed In the cylinder, there are multiple plates in the circumferential direction The plates also have small holes to process materials of certain shape The feeding method is similar to that of rotary cylinder dryer The hot air passes through the cylinder and the material layer from the bottom of the cylinder After moisture loading, the dryer is discharged through the upper part, which has the characteristics of both rotary cylinder dryer and fluidized bed ⑨ Rotary air dryer: the earlier application is Hearst company in Germany, which is used for PVC drying The basic principle of the dryer is that the main body of the dryer is composed of a cylinder with a jacket The hot gas flow carries the materials in a spiral upward movement in the dryer The hot gas flow carries heat and mass transfer with the materials, and at the same time is conducted by the jacket heat transfer and radiation heat transfer, so the thermal efficiency is higher than that of the convective heat transfer air dryer 2 The equipment scale is the unit equipment in the production, and the dryer aims to meet the production requirements With the expansion of production scale in various industries, the scale of drying equipment has been continuously expanded At present, the diameter of flash dryer equipment produced in China can reach 1.6m (there are few application cases beyond this scale), and it works well The heat transfer area of the paddle dryer can reach 160 ㎡, which can pass through various heat-carrying media The large heat transfer area of the disk dryer Zui has reached 180 ㎡ The mechanical centrifugal spray dryer can reach 45t/h The electro-mechanical centrifugal atomizer also reaches the scale of 5t/h The mechanical problem of the atomizer is well solved The diameter of the centrifugal spray dryer has reached 8 meters, with a total height of more than 50 meters, and the processing capacity is 4t/h The diameter of rotary cylinder dryer can reach 2.5 meters, up to more than 30 meters The area of belt dryer is also more than 140 square meters 3 The equipment level of horizontal drying equipment mainly refers to the control level of drying system, the equipment of auxiliary equipment, the convenience degree of operation and safety level, etc Throughout the equipment level of drying equipment in China, great progress has been made This is especially true for large drying systems Mainly in the following aspects: ① control system configuration Automatic and semi-automatic control systems are widely used to reduce labor intensity and stabilize product quality ② Application of computer technology Most of the large-scale systems use computer technology to collect, process and control the system parameters, so that the operating conditions of the system can reach Zui optimal ③ Humanized design At the same time of equipment design, consider the habits of operators and the convenience of maintenance ④ Safety design The system has the functions of safety alarm and danger elimination, especially for the drying of inflammable and explosive materials ⑤ Ancillary equipment The auxiliary equipment in the system also tends to be reasonable, and the matching relationship between the heating, feeding, gas-solid separation, product packaging equipment and the host reaches Zui optimization 4 Experimental conditions the design of the dryer needs the relevant process parameters of specific materials, many important parameters must be obtained through the experiment, the design of the dryer is highly dependent on the experiment Therefore, the experimental conditions are the key to design the dryer accurately