Principles for selecting dryers in the pharmaceutical industry Chinese raw materials and pharmaceutical intermediates(hereinafter referred to as active pharmaceutical ingredients) hold an important position in the international market due to their low prices. China's accession to the WTO has brought both opportunities and new challenges to the pharmaceutical industry. For various purposes, in the past two years, importing countries of raw materials have put forward higher requirements for the production process and social responsibility of pharmaceutical companies in China. Therefore, various certifications have been rapidly launched in the pharmaceutical industry, and at the same time, China's Good Manufacturing Practice (GMP) certification work is also accelerating. The focus of these certifications is on the precision, drying, and packaging positions for active pharmaceutical ingredients, and the reasonable selection of dryers is particularly important. The drying device must comply with GMP requirements to ensure the rationality of the drug production process, uniform product quality, no accumulation of materials, and meet the requirements of online cleaning. The drying device used for sterile raw materials must also meet the requirements of online sterilization. At present, there are many types of API dryers in China, including vacuum drying oven, vacuum rotary dryer, three in one, airflow dryer, spray dryer, fluidized bed, fluidized bed, freeze dryer, etc. Below are brief discussions on their respective characteristics and applicable conditions. Vacuum drying oven is an older drying device, which is divided into several layers by heating plates inside the oven. Hot water or low-pressure steam is introduced into the heating plate as the heating medium. The tray containing the medicine to be dried is placed on the heating plate, the box door is closed, and a vacuum pump is used to create a vacuum inside the box. The heating plate heats the medicine to the specified temperature through the circulating flow of the heating medium, and the moisture begins to evaporate and gradually be evacuated with the vacuum. This device is easy to control and can condense and recover evaporated solvents. During the drying process, drugs are not easily contaminated and can be used for drug drying, packaging sterilization, and heat treatment. In the 1980s, this equipment was commonly used as the main dryer in the raw material pharmaceutical industry. However, due to the difficulty of online cleaning and sterilization of the material tray, the drying speed was slow, the labor intensity of workers was high, and in order to achieve drug uniformity, it had to be mixed by a powder mixing device after drying. Nowadays, it is rarely used in large-scale production of raw materials and is mostly used for medium and small-scale trial production or packaging material heat treatment. Vacuum rotary dryer is derived from a double cone mixer, which is mostly cylindrical in body and conical at both ends, also known as a double cone dryer. There are two hollow suspension shafts in the middle of the cone, which are used for equipment rotation support and channels for vacuum and hot water. The medicine rotates while drying in the dryer, ensuring good uniformity of the entire batch of medicine. The heat medium enters the jacket through a hollow tube at one end, and the hot air inside the device is discharged through the exhaust pipe in the hollow tube at the other end, and the evaporated solvent is recovered through condensation. There are currently many domestic manufacturers. Later on, similar products such as single axis rotary dryers, multi-dimensional rotary dryers, and inclined rotary dryers emerged. The supporting equipment of this device includes vacuum system, solvent recovery system, cleaning and sterilization system, etc. Due to its simple operation, easy adjustment for intermittent production, and the ability to perform online cleaning and sterilization, this device has become a drying machine for small and medium-sized antibiotic raw material enterprises, such as penicillin, lincomycin, streptomycin, etc. When selecting equipment, the main considerations are the concentricity of the two hollow shafts and the sealing of the hollow shafts. To ensure smooth operation of the equipment, the concentricity requirement is that the shaft end runout is less than 0.01mm. The sealing effect of the hollow shaft is mainly to prevent lubricant or filler from contaminating the medicine. Three in one equipment refers to combining the three processes of filtration, washing, and drying in one device, which is very representative in the pharmaceutical industry. This type of equipment has developed rapidly and can be divided into several types such as belt type, tank type, centrifugal type, etc. There are two types of belt type three in one: step type and continuous type. The main difference is that the advancing mode of the filter belt is different, and the workflow is completely the same. The material is evenly spread on the filter belt by the feeder, and the filter belt is dragged by the transmission device to move inside the dryer. Wash the solvent in the washing and filtration section, and recover the solvent mother liquor by vacuum cold suction; Hot air enters the drying section, is evacuated and condensed to recover the solvent. Used for large-scale mass production, suitable for drying granular materials with good breathability, the finished product dries evenly, and is widely used in the vitamin C and penicillin industries in China. Due to the relatively poor airtightness of this equipment, online cleaning and sterilization cannot be arranged well, so it is only suitable for drying non sterile raw materials and pharmaceutical intermediates. The feeder and filter belt correction device of this equipment play a key role in the normal operation of the equipment. In addition, supporting facilities such as heaters and vacuum systems also have a significant impact on the equipment yield. The equipment used in the pharmaceutical industry is mainly imported or assembled with imported main components. Domestic equipment of this type is only used in industries such as chemical, food, and traditional Chinese medicine. In recent years, some companies have also replicated it in the pharmaceutical machinery industry, but successful applications in the pharmaceutical industry are not common. Three in one tank type, the tank body is similar to a large suction filter, with a metal sintered plate filter screen, support plate, and heating plate combined as the chassis. The tank body has a jacket for heating and cooling, and there is a stirrer that can move up and down inside the tank. The stirrer is a hollow structure that is filled with medium for heating and cooling, and plays a major role in the drying stage. After the material enters the equipment, it is filtered and soaked in washing medium for a certain period of time. It is then filtered by cold suction or pressure suction to a certain extent. The mixing, chassis, and jacket are simultaneously heated with heating medium, and vacuum is applied for drying. Based on experience and qualified sampling, drying is stopped and the material is discharged from the outlet. The mixing seal and sintering plate of this equipment are key, and the supporting equipment includes hydraulic system, vacuum system, heating and cooling unit, etc. Due to the fully enclosed nature of this equipment, if an automatic discharge system is added, the equipment can fully achieve online cleaning (CIP) and online sterilization (SIP), making it very suitable for the production of sterile raw materials. In recent years, such equipment has been widely used in the production of penicillin sodium salt and semi synthetic antibiotics. In the 21st century, with the acceleration of GMP certification, China's pharmaceutical machinery industry vigorously develops or imitates similar imported equipment. However, due to differences in processing accuracy and process control, domestically produced three in one equipment is mainly used in the production of non sterile raw materials. The centrifugal three in one system adds the function of hot air drying on the basis of the vertical filtration centrifuge. It has various forms such as filter bags or metal filter plates. The production process is basically the same as the tank three in one system, except that the centrifugal spin drying is changed from vacuum drying to centrifugal spin drying, which can greatly reduce the production time of a single batch of materials. However, due to the limited capacity of the centrifuge silo, the production capacity of a single batch is limited, making it more suitable for the production and use of small and medium-sized sterile raw materials. Due to the fact that this equipment can place the silo and transmission device separately inside and outside the sterile room, equipment maintenance does not require entering the sterile room, making production and use very convenient. In recent years, joint ventures in the domestic raw material pharmaceutical industry have introduced such equipment, and counterfeit products have also emerged in China. Airflow drying device is suitable for easily dehydrated granular and powdery materials, and can quickly remove material moisture (mainly surface moisture). In airflow drying, the quality of the dried product is controlled due to the short residence time of the material in the dryer. Wet materials are thoroughly mixed with hot air flow through a feeder, and while drying, they are further uniformly dried in a drying tube by being attracted by wind. Wet and heavy particles that cannot be attracted by wind continue to be impacted, crushed, and dried in the dryer until they can be sucked up by the wind and enter the drying tube, which ends in a cyclone separator. This device is mainly used in the pharmaceutical industry for the production of tetracycline and some other substances. Spray dryer The drying process of this equipment is similar to airflow drying. After initial filtration, the air is heated by a heater, and the generated hot air is filtered through several stages (selected according to the drug grade). Then, a uniform rotating airflow is generated by a hot air distributor in the volute channel at the top of the drying chamber and enters the drying chamber. The material is filtered through a centrifugal atomization disc or pressure nozzle, producing dispersed and fine material mist. The material mist comes into contact with the swirling hot air, and the moisture evaporates rapidlyThe material is dried in a short period of time. This device is suitable for drying liquid materials with good fluidity such as solutions, emulsions, suspensions, and pastesOur company has been using this equipment to produce streptomycin since the 1950s. Nowadays, this equipment can be used for the drying of streptomycin, gentamicin, and various biological extracts in the raw material pharmaceutical industry. Boiling bed is a device where drugs are added from the top of the bed, hot air is blown from the bottom, and passes through a porous distribution plate to come into contact with a certain thickness of material layer. The material is in a fluidized and boiling state, flipping up and down, mixing and colliding with each other in the airflow. The contact area between gas and solid is large, and intense heat and mass transfer occurs, greatly improving the drying speed and efficiency. It is an ideal drying equipment. For some wet materials, they can be dried in one go to achieve the required moisture index. The fluidized boiling state has high thermal efficiency. The residence time can be adjusted, making it easy to obtain low moisture finished products. Particles of different sizes can be classified on the bed surface, coarse particles can be discharged from the bed, and fine powder can be discharged from the dust collector. For some materials, bag dust collectors can be installed inside the main unit (built-in), saving floor space, having a simple structure, and requiring less investment. This equipment is suitable for drying powder, granules, silk, and strip materials. The equipment is fully enclosed and can be cleaned and sterilized online. It is widely used in the production of antibiotics and semi synthetic antibiotics in the pharmaceutical industry. Fluidized bed equipment includes fluidized bed and vibrating fluidized bed. Due to the influence of fluidity, vibrating fluidized bed is mostly used for drug drying. The dryer generates excitation force from a vibration motor to make the machine vibrate. The material jumps forward under the excitation force in a given direction. At the same time, hot air is input from the bottom of the bed to make the material in a fluidized state. The material particles fully contact with the hot air and undergo intense heat and mass transfer processes, resulting in thermal efficiency. The upper chamber is in a slightly negative pressure state, with moist air drawn out by the induced draft fan and dry material discharged through the discharge port, thus achieving the desired drying effect. This device has uniform fluidization, no dead corners, uniform temperature distribution, and high thermal efficiency. Suitable for drying granular, powdered, linear, and filamentous materials, such as starch, glucose, and many pharmaceutical intermediates produced in large quantities. Freeze dryer vacuum freeze dryer is suitable for drying heat sensitive or easily oxidizable drugs, commonly known as freeze-drying machine, mainly including freeze-drying box, vacuum system, heating system, refrigeration system, etc. According to the shelf area, it can be divided into small experimental freeze-drying machines, medium-sized production freeze-drying machines, and large industrial production freeze-drying machines. There are many freeze-drying machines used for drying raw materials and formulations. The main requirements are high reliability, complete sterilization function, and a temperature difference of no more than 1.5 ℃ between the same shelf and the layers. This also requires good flatness of the shelf. When using this equipment to dry raw materials, a powder mixer is added to ensure the uniformity of the product. Ampicillin, large amounts of blood products, artificially cultivated drugs, antibodies, vaccines, etc. mostly use freeze-drying machines& nbsp; In the past 20 years, with the process of reform and opening up, the pharmaceutical industry has developed rapidly, and at the same time, the pharmaceutical machinery industry has also shown a flourishing situation. Due to work reasons, the author has had the opportunity to apply the above drying devices. Due to limited knowledge, there are still many good dryers that have not been introduced, such as disc dryers, fluidized bed dryers, flash dryers, microwave series dryers, etc. When selecting a dryer, it should be based on the characteristics of the drug and the ideal state that the finished product should achieve, especially considering the material and sterility assurance of the sterile raw material drying equipment. China's pharmaceutical drying equipment has developed rapidly in the Jiangsu area, with many drying equipment factories. Their products have both universality and unique characteristics, which provides conditions for the localization of imported equipment for drying raw materials and the selection of ideal dryers that comply with the Good Manufacturing Practice (GMP) for drug production.