High-purity vitamin C crystal filtration, washing and drying in one

Vitamin C, also known as ascorbic acid, is a substance that the human body cannot synthesize by itself but is essential. It is closely related to human health. China is a major producer of vitamin C. Of the global demand of 80,000 tons per year of vitamin C, China's supply accounts for more than 50%. Vitamin C is a high-energy-consuming product. With the sharp drop in the price of vitamin C in the international market, reducing the energy consumption in the production of vitamin C (especially the energy consumption in the drying process of vitamin C - which accounts for more than 30% of the total energy consumption in vitamin C production) has become the key to the survival of production enterprises. Drying is a very important step in the production of vitamin C. Previously, double-cone rotary vacuum dryers were often used for drying, but this type of dryer has disadvantages such as inability to produce continuously, uneven heating of materials, high energy consumption, and complex operation.

Analysis of the Conventional Refining Process for Vitamin C Production

The current common methods for the production of vitamin C are the sulfuric acid acidification method and the ion exchange method. Among them, the sulfuric acid acidification method has been basically phased out, and the ion exchange method has become the main production process at present. Generally, the ion exchange process involves dissolving sodium vitamin C in water, passing the solution through cation exchange resin to remove sodium ions and generate vitamin C solution. After vacuum concentration, cooling and crystallization, crude vitamin C is obtained through centrifugal separation, and then refined and crystallized to obtain the finished vitamin C. The use of cation exchange resin consumes a large amount of tap water and discharges a large amount of waste acid and waste alkali. This method causes serious environmental pollution and does not meet the requirements of clean production. Meanwhile, the concentration of the vitamin c solution produced by this dissociation method is relatively low (15-20%), and it requires a large amount of evaporation and concentration to produce crude vitamin C. This results in a long entire process cycle, easy product deterioration, poor quality of crude vitamin C, low yield, high energy consumption, high equipment investment and high cost.

结晶过滤洗涤干燥四合一精制提纯维生素C 工艺设计

  结晶过滤洗涤干燥四合一精制提纯维生素C工艺以维生素C钠为原料，采用全自动多功能过滤洗涤干燥机进行制备高纯度维生素C的新方法，以克服现有技术存在的不足。具体工艺步骤为：
  (1) 酸化反应步骤：按照维生素C钠和水的重量比为1:0.341～0.894制成维生素C钠水溶液，维生素C钠水溶液在搅拌状态下加入盐酸或者通入HCl气体，其中VcNa:HCl按折纯重量比为1:0.175～0.215，使其充分反应，得酸溶液；在所得酸溶液中加入活性炭，加入比例为1L酸溶液加入2～10g活性炭，然后升温至65～70℃脱色再保温过滤,生成净化的酸溶液。
  (2) 结晶分离步骤：对酸化反应后的酸溶液边搅拌边降温，酸溶液降温至-5～5℃,并保持1～3小时，使维生素C从酸溶液中析出，过滤得粗品维生素C和析出维生素C后的酸溶液；
  (3) 除盐过滤步骤：取结晶分离析出粗品维生素C后的酸溶液，减压浓缩至维生素C含量在50～60%,使维生素C处于65～70℃温度下的近饱和状态，温度控制在65～70℃保温过滤，除去氯化钠，得到滤液；
  (4) 粗品结晶过滤步骤：对步骤3所述的滤液利用冰水和冰甲醇洗涤再降温降温至-5～5℃，并保持2～10小时，结晶、过滤得回收品粗品维生素C；采用真空抽滤，得到的粗品维生素C和回收品维生素C。
  (5) 高纯度维生素C精制步骤：将粗品维生素C和回收品维生素C加入无盐水中溶解后脱色过滤，降温、结晶、分离、烘干既得成品维生素C。高纯度维生素C含量99.8%，旋光=+21°，消光值为0.038，其他指标均符合药典2000版二部标准。

The four-in-one process of crystallization, filtration, washing and drying for refining and purifying vitamin C takes advantage of the difference in solubility of sodium chloride and vitamin C with temperature. Sodium vitamin C is directly acidified with hydrochloric acid to generate a water solution of vitamin C and sodium chloride. By using thermal filtration, cooling and concentration methods, the separation of vitamin C and sodium chloride is gradually achieved, and crude vitamin C and by-product sodium chloride are prepared. Crude vitamin C is refined and recrystallized to obtain finished vitamin C. After inspection, all the indicators of the finished vitamin C product met the standards of the second part of the 2000 Edition of the Pharmacopoeia. The new production process can significantly reduce water, acid and alkali consumption, lower energy consumption, solve environmental pollution problems, shorten the production cycle, reduce production costs, increase product yield and finished product quality. It is an economical and effective method for preparing vitamin C.

On-site photos of the four-in-one process of crystallization, filtration, washing and drying for the refined purification of vitamin C