Guangzhou Taixin Auto parts Trading Co., Ltd. , https://www.taixinspareparts.com
Rotary drum dryers are currently used for the drying of pesticides. There is a slanted angle between the horizontal and the horizontal placement, and the rotary cylinder dryer is the material added to the main machine, and is also a continuous drying device. The material is conveyed by the inclination of the cylinder and the gas.
The wet material is fed into the dryer through one end of the dryer through a feeder, and is heat-dried through the contact of hot air or a heated wall in the drum. There are two types of heating: direct heating and indirect heating. Direct heating is divided into parallel flow, counterflow, cross flow and other heat transfer methods. Generally, convection heat transfer is the main form, and hot air and flue gas are often used as the heat transfer medium. Indirect heating means that heat is transferred to the material through the wall surface. The heat transfer medium mainly includes steam, heat transfer oil, and hot water. In the actual production process, two kinds of heating forms are often used at the same time to form a third heat transfer type drying machine, which is a double-heating rotary dryer. A part of the heat of this kind of dryer is transmitted to the material through the wall through conductive heat transfer, and the other part is transferred by the hot air of convective heat transfer to the material. At the same time, the moisture in the material is taken away. It is conductive heat transfer and The combination of flow heat transfer and therefore higher thermal efficiency.
The main features of the rotary dryer are large production capacity, wide application range, small fluid resistance, large operation flexibility, and easy operation. However, the equipment is large and complex and covers a large area. One-time investment is higher, and transmission agencies need frequent maintenance. It has been widely used for the drying of pesticides and fillers such as white carbon black, kaolin, and bentonite.
2.6 Rotary Fast Dryer
Rotary flash dryers are ideal drying equipment for handling pasty materials. Since the introduction of China in the late 1980s, it was first used in the dye industry. Its advantages are quickly recognized by users, and this technology is quickly digested and absorbed. It is also currently used for the drying of pesticides.
As we all know, the safety of pesticide production is very critical, and the advantages of the rotary rapid dryer determine that it is suitable for drying some paste pesticides. However, it is also a kind of dry convection drying. The mixture of materials and air makes the gas-solid separation process inevitable in the later stage of operation. However, it is inevitable that a small amount of pesticides will be emitted from the exhaust gas. Therefore, the process is often designed as a part of the exhaust cycle, direct-fired, self-inert or semi-closed process. The tail gas is removed by high-temperature treatment or open fire to remove harmful components to avoid the harmful substances contained in the exhaust gas. It has been successfully used in the drying of the insecticide list.
3 Development Trend of Pesticide Drying Equipment
According to the development status of the drying technology and the equipment level of the pesticide industry, it can be said that the types of domestic dryers are basically complete and can meet the needs of pesticide drying. The future development of dryers may be concentrated in the following aspects:
3.1 The finalization and serialization of drying equipment
For dryers that have been used for many years and are still very mature, in order to facilitate the promotion and use, the finalization and serialization work should be carried out. The corresponding standards should be formulated to facilitate the use of plant selection.
3.2 Larger drying equipment
Although the types of dryers in China are relatively complete, the scale of production is relatively small. It is understood that there are few dryers with a evaporative water volume above 1000kg/h in the pesticide plant, and there is also a lack of technical practice in designing large-scale dryers. Small dryers have an adverse effect on the stability of the product quality, and the operating costs are also high. From the perspective of improving product quality, dryers should be developed in the direction of large-scale production.
3.3 Operating System Automation
The automation of drying equipment is the future direction of development. The main operating parameters are automatically controlled to eliminate human factors to the maximum extent.
Pesticide drying system has many variable factors during operation. If the system is fluctuating during production, it will easily affect product quality. Improve the level of automation of the equipment and use advanced computer control systems to reduce or eliminate human factors and ensure product stability.
3.4 Improve dryer thermal efficiency
Increasing the thermal efficiency of the dryer is the main task for the development of the drying technology in the future. The improvement of thermal efficiency at home and abroad is mainly based on the following aspects:
1 Increasing the heat-resistance temperature of pesticides Increasing the temperature difference at the inlet and outlet of dryers is the main method for improving thermal efficiency. However, lowering the outlet temperature will cause the product moisture content to exceed the specified standard, and increasing the inlet temperature will be limited by the heat resistance of the material. In other words, there is a tendency for pesticides to increase their concentration at the inlet temperature. However, the heat resistance can be improved by studying the processing formula, which is also one of the important tasks of pesticide processing workers.
2 Using a Combined Dryer It has been said that drying technology has developed for many years and there has been no new change in the basic type of dryer, and there has been no new breakthrough in the drying mechanism, but only a change in the structure of the dryer. Use existing dryers for optimal combinations such as spray air flow, spray fluidized drying. The use of multi-stage drying makes it possible for different types of dryers to exert their respective advantages, which is also one of the methods for improving thermal efficiency and saving energy.
3 The heat recovery technology convection heat transfer dryer, the thermal efficiency is generally relatively low, most of the heat is taken away from the exhaust, there are examples to prove that exhaust heat away about 34% of the total, the thermal efficiency is very low. The methods for recovering heat from exhaust gas in foreign countries are mainly semi-closed loop, heat pipe and heat pump technology. Domestically, this technology is also being developed. If it is put into industrialization, it will have important economic significance.
3.5 Development of a dedicated dryer
For the needs of new formulations of pesticides, special drying equipment was developed to meet the needs of special dosage forms. In the coming period, hot air circulation ovens, spray dryers, rotary rapid dryers, rake dryers, air dryers, and paddle dryers are still the main drying equipment for pesticide plants, and their technology should be further studied. Research on the large-scale research of spray dryers, structural studies of rotary fast dryers, research on classification efficiency, research on the structure of rake dryers, serialization and large-scale research of hollow blade dryers are all urgently needed for pesticide production.
4 Design points of pesticide drying equipment
4.1 If a certain economic scale can be achieved, the continuous drying method should be used as far as possible to reduce the labor intensity on the one hand, and on the other hand to reduce the pollution to the environment and also reduce the loss of the product.
4.2 The design of the dryer must first determine the temperature of the heat-sensitive pesticides, to prevent over-temperature drying affect the suspension rate.
4.3 For some non-water-soluble pesticides should be wet crushing before drying, should pay attention to the choice of processing formula, in order to adapt to the drying process, should choose better heat resistance additives. At the same time wet crushing must meet the required fineness requirements.
4.4 For convective drying equipment, the gas-solid separation must pay attention to the emission of pesticide dust in the tail gas. On the one hand, it is necessary for environmental protection, and on the other hand, it is also the need for farmland protection near the production area. The treatment of exhaust gas in the system should be seriously addressed, otherwise it will cause pollution and even production accidents.
4.5 In order to prevent the exhaust gas discharged from convection dryers from exceeding the standards, if the production plant is qualified to obtain combustible gases, a semi-closed loop process may be adopted to incinerate part of the dusty gases in the tail gas to reduce the dust emission. In addition, the dry gas can be made inert by this method. When the oxygen content is less than 8%, it is safer to dry the solvent-containing pesticide.
Agricultural Drying Equipment Status and Future Trends (2)
2.5 Rotary cylinder dryer