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A spray dryer takes a liquid stream and separates the solute or suspension as a solid and the solvent into a vapor. The solid is usually collected in a drum or cyclone. The liquid input stream is sprayed through a nozzle into a hot vapor stream and vaporized . Solids form as moisture quickly leaves the droplets. A nozzle is usually used to make the droplets as small as possible, maximizing heat transfer and the rate of water vaporization. Droplet sizes can range from 20 to 180 μm depending on the nozzle. There are two main types of nozzles: high pressure single fluid nozzle (50 to 300 bars) and two-fluid nozzles: one fluid is the liquid to dry and the second is compressed gas (generally air at 1 to 7 bars). Spray dryers can dry a product very quickly compared to other methods of drying. They also turn a solution (or slurry) into a dried powder in a single step, which simplifies the process and improves profit margins. In pharmaceutical manufacturing, spray drying is employed to manufacture Amorphous Solid Dispersions, by uniformly dispersing Active Pharmaceutical Ingredients into a polymer matrix. This state will put the active compounds (drug) in a higher state of energy which in turn facilitates diffusion of drug spices in patient body. It is a device that can complete drying and granulation at the same time. According to the process requirements, the pressure, flow rate and the size of the nozzle hole of the liquid pump can be adjusted to obtain the required spherical particles in a certain size ratio. A spray dryer is a type of continuous atmospheric dryer. The liquid material is sprayed into a mist with special equipment, and it is dried by contact with hot air. For drying some heat-sensitive liquids, suspensions and viscous liquids, also for drying fuels, intermediates, soap powder and inorganic salts. Generally, it includes electric heating blast drying oven, vacuum drying oven, high-speed centrifugal spray dryer, and sterile spray dryer. The working principle, basic classification, characteristics, technical parameters, application scope and operation process of the spray dryer are introduced in detail.

Drying equipment, also known as dryer, is a device used for drying operations. The moisture in the material (generally refers to moisture or other volatile liquid components) is vaporized and escaped by heating to obtain solid materials with a specified moisture content. The purpose of drying is for the needs of material use or further processing. For example, drying of wood before making wooden molds and woodware can prevent deformation of products, and drying of ceramic blanks before calcination can prevent cracking of finished products. In addition, the dried materials are also convenient for transportation and storage, such as drying the harvested grains below a certain moisture content to prevent mildew. Since natural drying is far from meeting the needs of production development, various mechanized dryers are more and more widely used. The drying process needs to consume a lot of heat energy. In order to save energy, some materials with high moisture content, suspensions or solutions containing solid substances are generally dehydrated or evaporated by heating, and then dried in a dryer to obtain dry solids. In the drying process, it is necessary to complete the transfer of heat and mass (moisture) at the same time, to ensure that the partial pressure (concentration) of the moisture vapor on the surface of the material is higher than the partial pressure of the moisture vapor in the external space, and to ensure that the temperature of the heat source is higher than the temperature of the material. The heat is transferred from the high temperature heat source to the wet material in various ways, so that the moisture on the surface of the material is vaporized and dissipated to the outside space, so that there is a difference in the moisture content between the surface and the interior of the material. The internal moisture diffuses to the surface and vaporizes, so that the moisture content of the material is continuously reduced, and the overall drying of the material is gradually completed.