In the 1960s, China began developing vacuum freeze-drying equipment, primarily for use in the pharmaceutical sector. As part of efforts to expand its applications, the country also introduced large-scale vacuum freeze-drying systems, aiming to apply them in health products and agricultural processing. However, due to limited domestic demand during that time, the industry faced a decline in the late 1960s and early 1980s, leading to stagnation.
Starting from 1998, the market for vacuum freeze-drying equipment began to improve, with increased sales and a more stable industry environment. Currently, large-scale vacuum freeze-drying systems used in food, healthcare, and pharmaceutical sectors are mostly imported from overseas, which makes them expensive. Although some domestic companies have started producing similar equipment, they face challenges related to technology, quality, and performance. Key issues include uneven heating and insufficient vacuum levels, which can slow down the drying process. The critical vacuum level for sublimation drying is around 4.7 mmHg at 0°C, and any deviation from this can significantly impact efficiency.
Microwave vacuum freeze-drying equipment has been available in China for over a decade, but most of it is small-scale. The production of such equipment remains technically challenging, limiting its widespread adoption. One of the main technical difficulties in manufacturing microwave vacuum freeze-drying systems is the discharge of low-pressure gas. When the vacuum is too low, adding external energy can cause high-frequency discharges. This phenomenon not only hinders the transmission of microwave energy into the material but also leads to serious reflections, damage to the sealing window, and ultimately the loss of the vacuum inside the chamber. These issues continue to hinder the development and commercialization of microwave-based vacuum freeze-drying technology in China.
Sodium chloride (NaCl), with a white crystalline appearance, is mainly derived from seawater and is the main component of table salt. Easy to dissolve in water and glycerol, slightly soluble in ethanol and liquid ammonia; Insoluble in concentrated hydrochloric acid. Slightly hygroscopic in the air. It has good stability and is used in industry to manufacture SODA ASH, CAUSTIC SODA, and other chemical products. It is also used in ore smelting and can be used as a seasoning in daily life.
SODIUM CHLORIDE
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