There are various drying methods in freeze dryers, such as sun-drying, boil-drying, drying, spray drying and vacuum drying, etc., but ordinary drying methods are usually carried out at temperatures above 0°C or higher. The dried products generally have the problems of reduced volume and hard texture. Most of the volatile components will be lost. Some heat-sensitive materials will be denatured and deactivated, and some materials may even be oxidized. Therefore, there is a big difference in the properties of the dried product compared to the one before drying. The freeze-drying method is basically carried out under 0℃, that is, when the product is frozen, and only when the residual moisture content of the product is reduced in the later stage, the product is allowed to rise to a temperature above 0℃, but generally not more than 40 ℃. In the freeze dryer under vacuum conditions, when the water vapor is directly sublimated, the medicine remains in the frozen ice shelf, forming a sponge-like loose porous structure, so its volume after drying is almost unchanged. Before using it again, just add water for injection and it will dissolve immediately.
The low-temperature drying of the freeze dryer is to freeze the material with a lot of water in advance to reduce the temperature and freeze it into a solid state, and then sublime the water vapor immediately under the standard of the vacuum pump, and the material itself is left in the ice shelf during freezing and cleaning. Therefore, its volume will not change after drying. The loose porous structure needs to digest and absorb heat when subliming. This will cause the product’s own temperature to decrease and slow down the sublimation rate, so as to increase the sublimation rate and reduce the dry time. Carry out moderate heating. All dryness is carried out at a lower temperature.
Is the freeze dryer capable of drying liquid raw materials?
The amount of water vapor in the compressed air of the freeze dryer is determined by the temperature of the compressed air: under the condition that the working pressure of the compressed air remains unchanged, reducing the temperature of the compressed air can reduce the water vapor content in the compressed air. The necessary water vapor will solidify into a liquid. The freeze dryer uses this basic principle to select industrial refrigeration dry compressed air. Therefore, the refrigeration dryer is equipped with a refrigeration unit. The refrigeration unit of the freeze dryer belongs to the reduced-type refrigeration, which is composed of four basic components such as the refrigeration unit, the cooler, the air-conditioning evaporator, and the air-conditioning expansion valve. They are connected with pipelines to produce a closed system software.
The purpose of the freeze dryer is to freeze the material with moisture content into a solid, and then sublime the water in it from the solid to a vapor state to remove the water and store the material. Simply put, it is a dry whole process based on refrigerated raw materials. The freeze dryer has an LCD screen, a Chinese page, and a test sample dry curve graph; it has an imported refrigeration compressor and a heat exchanger, which expands the cooling capacity of the air conditioner and improves the water catching capacity; The trap has a large opening, no internal fan coil, and pre-freezing function for the sample. In addition, the pre-cooling rack can be used as a drainage barrel to accelerate the drying rate. The cold trap and the actual operating surface are all stainless steel plates, which are corrosion-resistant and easy to be smooth. Transparent bell jar. It is this kind of personality that makes freeze dryers more common in daily applications.
Although small and medium freeze dryers cannot dry the liquid raw materials immediately, large and medium freeze dryers can completely guarantee this.