Innovation and Development of Vertical Closed Circulation Dryer

Some synthetic drugs are usually crystallized in organic solvents and contain a considerable amount of organic solvents. If these organic solvents are directly discharged into the atmosphere, they will seriously pollute the environment and cause energy waste. Drying and recycling various solvents for reuse are not only in line with the requirements of environmental protection, but also the requirements of the company's own development. Therefore, for the drying of these drugs and APIs, it is more appropriate to choose a closed-circuit drying system, which can effectively achieve economical, Effective unification of environmental and social benefits.

In recent years, when drying anaerobic materials or materials containing flammable and explosive organic solvents, and the organic solvents can be recycled and cannot be discharged into the atmosphere, closed-circuit dryers are generally used for drying of these special materials. , using nitrogen as the drying medium, the nitrogen is heated and circulated in the drying system, the nitrogen in the circulating flow process takes out the organic solvent in the material, and the gaseous organic solvent is condensed into a liquid state by the condenser in the drying system, and It is recycled by the recycling system to achieve the purpose of drying the material. At the same time, due to the injection of nitrogen in the drying system, the oxygen content is reduced. When the oxygen content is reduced to the specified value, anaerobic materials can also be safely dried. Based on these advantages, this vertical closed-circuit Dryer is currently in comparison. Special pharmaceutical products, chemical products and other industries are widely used. In the process of use, there are also some prominent problems. In response to these problems, After many technical and process demonstrations, our company has summarized the following problems and proposed solutions

Problem 1: The dust removal method of closed-circuit Drying Equipment is not environmentally friendly

For the dust removal method of closed-circuit drying equipment currently used by many pharmaceutical companies, pulse backflushing is mainly used for dust removal, some materials will adhere to the surface of the filter cartridge. In order to make the material on the surface of the filter cartridge fall off, the backflushing system needs to backflush the inner wall of the filter cartridge, and the gas used for backflushing is nitrogen. Backflushing into the equipment system causes the positive pressure in the system to increase rapidly and the oxygen content to decrease. When the positive pressure in the system reaches a certain level, the automatic pressure relief port begins to release pressure, and the frequency of pressure relief is very fast. During the pressure relief process The nitrogen and the organic solvent in the nitrogen will be released from the pressure relief port, which will consume a large amount of nitrogen, and the recovery of the organic solvent will be much less.

Problem 2: The surface area of the filter cartridge affects the production efficiency

In the process of backflushing and dust removal, due to the relatively large surface area of the filter cartridge, the pressure and flow of backflushing nitrogen are not enough to blow back all the materials attached to the surface of the filter cartridge, so that the material on the surface of the filter cartridge will accumulate more and more. The resistance on the surface of the filter cartridge will become larger and larger, resulting in poor material boiling state, or even no boiling, which seriously affects the production efficiency and product yield.

Problem solving

Based on the problems raised above, combined with the specific production process of the user's materials, the process flow 2 shown in Figure 2 is a good solution. Its main process principle is the same as process one, using the traditional air cylinder shaking bag dust removal method, combined with the structural characteristics of the closed-circuit drying equipment system with high airtightness requirements, the dust removal cloth bag is made of smooth anti-static cloth with good air permeability. The cylinder adopts a double-stroke cylinder structure. The long stroke is used for disassembling and assembling the cloth bag or for maintenance and repair, and the short stroke is used for the up and down shaking of the cloth bag. Because the cloth bag shakes up and down under the action of the cylinder, the material attached to the surface of the cloth bag is easily shaken off, and the cylinder is shaken up and down using compressed air, which has nothing to do with the mixture of nitrogen and air circulating in the system. It saves a lot of nitrogen, and the pressure in the system will not increase frequently and is automatically released to the atmosphere, which is conducive to the requirements of environmental protection, and is also conducive to the complete recovery of organic solvents in materials, and also greatly improves production efficiency.

Comparison of advantages and disadvantages of new and old processes

Compared with the first process, the main advantages of the second process are as follows: ① It can recover the organic solvent better and more effectively, and reduce the production cost; ② It can save a lot of nitrogen; ③ It can better shake the bag for dust removal and improve the production efficiency; ④ It can better Avoid the pollution of organic solvents to the environment; ⑤ The operation procedure is simpler, more convenient and easier to maintain. The main disadvantage is that the height of the user's room is higher, or the user is required to open a hole on the ceiling (top plate) of the room to facilitate the installation of the double-stroke cylinder.