With the improvement of the level of medical drugs, the […]
With the improvement of the level of medical drugs, the application of semi-synthetic antibiotics has become more widespread, which has also promoted the development of the semi-anti-industrial industry and has become one of the main development directions of the pharmaceutical industry. In the half-anti-production process, some process reactions are required to be carried out in an ultra-low temperature environment below 50 °C. In order to ensure the reaction conditions, the reaction system is often cooled to -70 ° C or even lower, and the corresponding cooling and cooling measures must be taken. At present, the commonly used deep cryogenic refrigeration methods are: liquid nitrogen evaporative refrigeration and ultra-low temperature unit refrigeration. After comparing the two refrigeration methods, the cascaded ultra-low temperature unit has more advantages in the production process of semi-antibiotics.
The refrigeration unit is divided into single-stage refrigeration and cascade refrigeration according to the number of refrigeration cycle stages. Single-stage refrigeration systems use a medium-temperature refrigerant. When the evaporation temperature of the refrigerant in operation is lower than -70 °C, the evaporation pressure of the refrigerant is very low, and the specific volume of steam increases. The gas transmission coefficient is reduced, the compressor suction is difficult, and the working efficiency of the unit is greatly reduced. Therefore, when the single-stage refrigeration system provides the ultra-low temperature when the evaporation temperature is lower than -70 °C, the scale is difficult to be large and the economy is very low.
The cascade refrigeration system consists of a high temperature part and a low temperature part. The low temperature part provides the required ultra-low temperature capability, and uses low temperature refrigerants such as R13 and R23, but the condensation temperature of such refrigerants is very low, and it is difficult to condense them with cooling water under the same pressure. The high temperature portion uses a medium temperature refrigerant cycle, which functions to condense the low temperature refrigerant, and the high temperature portion and the low temperature portion share an evaporation condenser and "fold" to form a cascade refrigeration cycle using the two refrigerants. The production process requires a reaction temperature of -50 ° C, so the ultra-low temperature unit can fully meet the large-scale cooling requirements of the process requirements.