Abstract: Aiming at the defects of the original centrifugal spray dryer, on the basis of improving the process flow and drying tower structure of the original centrifugal spray dryer, a “melt-proof spray dryer” was developed, which can effectively prevent the material from melting. The occurrence of the phenomenon solves the problem of material sticking to the wall.
Key words: dryer; centrifugal spray; melting; sticking to the wall; traditional Chinese medicine extract
Most traditional Chinese medicines are extracted from the roots, stems and leaves of plants. The preparation method is to steam and boil the raw materials of traditional Chinese medicines to form extracts (usually called traditional Chinese medicine extracts). There is a lot of water in the traditional Chinese medicine extracts. , it must be dried into granules (or powder) and poured into capsules, and then subjected to process operations such as tableting or pill making, and finally a Chinese patent medicine is formed, which is convenient for people to take.
How to better complete the drying of traditional Chinese medicine extract has always been a difficult problem that the pharmaceutical equipment industry needs to solve. After long-term research and reference to many domestic and foreign relevant materials, we finally developed the “anti-melting spray dryer”, which is suitable for drying materials that are easy to melt, contain a lot of sugar and are easy to absorb moisture, and can effectively solve the stickiness of materials. It is extremely suitable for drying of traditional Chinese medicine extracts.
In the past, traditional Chinese medicine extracts were mostly dried by vacuum drying equipment and microwave dryers, but these two types of equipment have the following shortcomings: (1) The output is small and the drying time is long, which cannot meet the needs of large-scale production of traditional Chinese medicines;
(2) The products formed after drying are all cake-like, and processes such as crushing and sieving are also required, which is cumbersome to operate.
Later, the “Special Centrifugal Spray Dryer for Traditional Chinese Medicine Extract” produced appeared. Although it can greatly increase the output and the wall sticking phenomenon in the drying tower is also significantly reduced, there is still a biggest defect. That is, a set of purging device is installed in the tower body, and compressed air is used to blow off the fine powder adsorbed on the inner wall of the tower body, but the purging device itself will also have accumulated materials that cannot be removed in time. In the high temperature area, it may turn yellow, coke, and deteriorate, and it may fall into the product and cause pollution to the material. In severe cases, the product may even be scrapped, causing great waste.
Under the premise of better solving the problem of material sticking to the wall, centrifugal spray dryer & two-fluid spray dryer is currently the most suitable drying equipment for drying traditional Chinese medicine extracts. To this end, our company has renovated the original centrifugal spray dryer, which not only improves the drying process, but also innovates the structure of the drying tower.
The original centrifugal spray dryer process
The process flow of the original centrifugal spray dryer is roughly divided into the following two ways:
(1) Parallel flow: wet material and hot air enter the drying tower from the top of the tower and flow to the bottom of the tower together. During the flow, the wet material and the hot air are fully contacted, and the exchange process of heat and mass transfer is completed, so that the material dry.
(2) According to the discharge method of exhaust gas and dry material, it can be divided into two categories: the first type, the combination of bottom discharge and cyclone discharge, that is, there is a discharge port at the bottom of the cone at the bottom of the drying tower, Most of the materials are discharged from here and enter the barrel, and the exhaust gas is discharged from the exhaust pipe located in the middle of the cone. There is a certain amount of material in the exhaust gas, which is collected in the cyclone and discharged into the barrel. This way The disadvantage is that it is easy to accumulate material above the exhaust pipe installed horizontally in the cone, and it is difficult to remove, and the accumulated material will turn yellow and deteriorate over time. The second type, the exhaust gas and the material are discharged together through the pipeline at the bottom of the cone at the lower part of the drying tower, and the gas-solid separation is carried out by the cyclone separator. In this way, two-stage cyclone separation is generally designed.
The drying process of the above centrifugal spray dryer can not solve the problem of material melting. To this end, the process improvement of the “anti-melt spray dryer” developed by our company is as follows:
In the lower part of the cone, the dehumidified cold air is introduced into the tower body, and it flows in the opposite direction with the material, so that the hot material after drying is exchanged with the cold air, and the temperature of the material is reduced to below the softening point of the material, so as to avoid material softening, The occurrence of stickiness. The dried material is discharged from the bottom of the tower, the tail gas is evenly discharged around the junction of the cylinder and the cone of the main tower, and a small amount of material entrained in the tail gas is collected and discharged by the cyclone separator.
The advantages of the anti-melting spray dryer: (1) It avoids the occurrence of material melting and solves the problem of material sticking to the wall.
(2) The temperature of the dried material decreases and can be directly packaged. (3) Cone No pipes exist, and there is no problem of material accumulation.
The process flow of anti-melting spray dryer is shown in Figure 1
In order to meet the needs of the new drying process, the anti-melt spray dryer has improved the tower structure of the original centrifugal spray dryer. The main tower structure of the original centrifugal spray dryer, the upper part is a cylinder, the lower part is a cone, and the two sections are directly butt welded together. The anti-melting spray dryer increases the diameter of the upper end of the cone, inserts the cylinder into the cone, and connects it with a ring and a screw.
The structural features of the improved tower body: (1) The air outlet is set on the ring at the top of the cone with an enlarged diameter, and the 4 air outlets are evenly distributed to make the air exhaust and pressure distribution in the tower evenly distributed; ( 2) The diameter of the upper end of the cone is increased, which reduces the wind speed there, which is convenient for material settlement, reduces the material entrained in the exhaust gas, and improves the separation efficiency of the cyclone separator; (3) The exhaust pipe is eliminated in the cone, It reduces the possibility of material accumulation and effectively guarantees the quality of the product.
The main tower structure of the anti-melt spray dryer is shown in Figure 2
The anti-melting spray dryer introduced in this paper innovates the tower structure of the original centrifugal spray dryer and improves the drying process. At the same time, the use of ventilation and cold air technology prevents the occurrence of material melting, avoids material sticking to the wall, and solves the problems of easy melting, high sugar content and easy moisture absorption when the material is dried. It is an excellent equipment for drying extracts in traditional Chinese medicine preparations. .
Solving the problem of material sticking to the wall in the drying process of traditional Chinese medicine extract is beneficial to reduce the cleaning and cleaning times of the dryer and increase the running time of the equipment. For pharmaceutical manufacturers, it can increase the output, reduce the drying cost and improve the economic benefits of the enterprise.