Boiling dryers are often the equipment of choice in the production of solid formulations. Boiling drying has the advantages of good heat transfer effect, large production capacity, uniform temperature distribution, various operation modes, adjustable material residence time, low investment cost and small maintenance workload. After more than 30 years of use and improvement in China, it has shown its unique position in the field of drying, and it is now increasingly playing an important role in pharmaceutical, chemical, food and other aspects. 1. The working principle of boiling dryer is boiling drying, also known as fluidized bed drying. It uses the filtered clean air and the convective heat transfer through the heat exchanger to raise the air temperature to a certain value and enter the main engine air duct. Distribute into the boiler and the wet material enters the dryer from the feeder. Due to the wind pressure, the material forms a boiling state in the dryer, so that the hot air is in full contact with the material, thereby enhancing the heat and mass transfer process, and promoting the evaporation and separation of the moisture in the material in a short period of time. After the material is dried, it is discharged from the discharge port, and the exhaust gas is discharged from the top of the boiling bed. After the solid powder is recovered by the cyclone dust collector and the bag filter, it is emptied. 2. The working material of the boiling dryer is transported to the boiling bed by the skip, and sealed by the sealing ring and the boiling bed under the action of the cylinder lifting. Then, under the action of the induced draft fan, the air is purified by the filtering device, heated by the radiator, and then distributed into the boiling bed (drying chamber) through the air distribution plate (screen). The material in the hopper forms a boiling state (ie, fluidization) under the action of hot air and agitation. In the large-area gas-solid two-phase contact, the moisture (or solvent) inside the material evaporates in a short time and discharges with the air. Take away and the material is dried. 3. Technical characteristics of boiling dryer (1) Good heat transfer effect, uniform temperature inside the bed, high heat capacity coefficient (or volumetric heat transfer coefficient), large production capacity; (2) due to temperature inside the fluidized bed Uniform distribution, can avoid any local overheating of the product, so it is especially suitable for the drying of some heat sensitive materials (such as grinding, polyacrylamide, etc.); (3) continuous operation in the same equipment, can also be intermittent operation (4) The residence time of the material in the dryer can be adjusted as needed, so the product moisture content is stable; (5) Independent electrical cabinet and PLC human-machine interaction operation control, integrated all drying parameter settings, safe and convenient operation; 6) The drying device has few mechanical transmission components, the investment cost of the equipment is low, and the maintenance workload is small. 4. Suggestions for improvement of boiling dryer After long-term application and development, the boiling dryer has obvious improvement in structure and performance, and the quality is also constantly improved, but there are still some problems. Recommendations: 4.1 Improvements in inadequate use of thermal energy The boiling dryer is formally an air convection drying device. Compared with conductive drying equipment, the energy consumption is indeed greater, but if some measures are taken, it can be achieved. Very good energy saving effect. Suggestions: (1) Strengthen the sealing effect of the equipment. At present, most of the boiling dryer hoppers and the equipment body are connected by flat flanges, and the sealing effect is poor. It is recommended to use the concave-convex flange connection when designing; the imported pump (2) dryers use steel tube winding fins for heat exchange. Although the steel pipe can save material cost, but the heat transfer effect is not good, it is recommended to use copper pipe; (3) increase insulation measures. Add insulation to the outer casing of the heat exchanger to reduce heat loss. 4.2 Improvements on the air distribution plate (screen) It is suggested that the air distribution plate in the boiling dryer has two functions, one is to support the material layer, and the other is to make the gas distribution uniform. The size, shape, distribution potential, and opening ratio of the opening of the distribution plate all have a crucial influence on the distribution of the fluid. Uneven gas distribution will cause a "circulation" in the bed, which tends to cause "channeling" in some parts of the bed, while the rest is a deadbed. At this time, most of the gas follows the bed. Some of the channels are short-circuited through the bed in the form of "channeling", which makes the gas-solid contact greatly deteriorated, which should be avoided. A good distribution plate design should be able to suppress the occurrence of unevenness in the bed. That is, when the pressure drop is lowered and the airflow speed is increased in some parts of the bed, the resistance generated by the distribution plate should suppress the increase of the airflow, thereby suppressing The deterioration of fluidization. At present, most of the boiling air dryers use a single airflow distribution plate, and most of them use vertical perforated plates or mat-shaped mesh plates. The materials are prone to fluidization unevenness or dead angles during fluidization, and cannot be ensured in the particles. The uniformity of the drug, while the single opening form can not meet the production process requirements of different drugs. On the other hand, in order to reduce the leakage loss of the drug, a multi-layer mesh structure is generally used at present, and the airflow distribution plate and the boiling bed body are mostly fixed by a large number of bolts, which is inconvenient to disassemble, difficult to clean and cause residual pollution and cross-contamination. Suggestion: Using computer fluid dynamics model, heat transfer and mass transfer model, aerodynamic and thermodynamic simulation calculation and verification of parameters such as hole spacing, aperture and opening ratio in the design of air distribution plate to meet the production of different materials. Process requirements. In the installation mode, the connection method is made detachable to ensure quick installation and thorough and complete cleaning. 4.3 Suggestions for improvement of control system At present, the operating parameters of fluidized bed equipment are generally set by the experience of the operator, but it can be fully intelligent, and the process parameters can also be traced. This is for the fluidized bed. The electrical control system of the class of equipment puts forward higher requirements. In the electrical control system, it is necessary to have a series of devices for detecting temperature, humidity, pressure, differential pressure, wind speed, operating time, dust concentration, etc., and obtain basic data, which is then transported and stored in the touch screen through the transmitter, and the data is touched by the touch screen. Intelligent control can be achieved by performing a storage analysis and then developing a suitable routing. 4.4 Temperature Control Commonly used hot air heating control mode adopts simple “on†and “off†modes. When the temperature reaches the set value, the steam is stopped, but the heat exchanger still has residual heat to keep the air temperature rising, and vice versa. Causes excessive temperature fluctuations, affecting the dry quality of the equipment. Suggestion: By controlling the steam flow to maintain the temperature of the inlet air, the steam flow is increased when the temperature starts to rise, so that the inlet air temperature is close to the set value as soon as possible, and then the steam is automatically adjusted to slowly approach the set value. Maintaining a steady amount of steam keeps the inlet air temperature stable.
This paper starts with the working principle of boiling dryer, combines the process operation parameters to summarize some problems in the production process, and briefly puts forward suggestions for the improvement of such equipment. It is hoped that equipment manufacturers can develop more products to meet pharmaceutical production in the future. Pharmaceutical drying equipment with advanced process requirements, advanced performance parameters, operability, environmental protection, energy saving and advanced economic and technical indicators.
Vitamins:
Vitamin A: Retinol. Carotene compounds responsible for transmitting light sensation in the retina of the eye. Deficiency leads to night blindness.
Beta carotene: An antioxidant which protects cells against oxidation damage that can lead to cancer. Beta carotene is converted, as needed, to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. Excessive carotene in the diet can temporarily yellow the skin, a condition called carotenemia, commonly seen in infants fed largely mushed carrots.
Vitamin B1: Thiamin, acts as a coenzyme in body metabolism. Deficiency leads to beriberi, a disease of the heart and nervous system.
Vitamin B2: Riboflavin, essential for the reactions of coenzymes. Deficiency causes inflammation of the lining of the mouth and skin.
Vitamin B3: Niacin, an essential part of coenzymes of body metabolism. Deficiency causes inflammation of the skin, vagina, rectum and mouth, as well as mental slowing.
Vitamin B6: Pyridoxine, a cofactor for enzymes. Deficiency leads to inflammation of the skin and mouth, nausea, vomiting, dizziness , weakness and anemia.
Folate (folic acid): Folic acid is an important factor in nucleic acid synthesis (the genetic material). Folate deficiency leads to megaloblastic anemia.
Vitamin B12: An essential factor in nucleic acid synthesis (the genetic material of all cells). Deficiency leads to megaloblastic anemia, as can be seen in pernicious anemia.
Vitamin C: Ascorbic acid, important in the synthesis of collagen, the framework protein for tissues of the body. Deficiency leads to scurvy, characterized by fragile capillaries, poor wound healing, and bone deformity in children.
Vitamin D: A steroid vitamin which promotes absorption and metabolism of calcium and phosphorus. Under normal conditions of sunlight exposure, no dietary supplementation is necessary because sunlight promotes adequate vitamin D synthesis in the skin. Deficiency can lead to osteomalacia in adults and bone deformity (rickets) in children.
Vitamin E: Deficiency can lead to anemia.
Vitamin K: An essential factor in the formation of blood clotting factors. Deficiency can lead to abnormal bleeding.
Nutritions:
For the treatment of nutritional disease, any of the nutrient-related diseases and conditions that cause illness in humans. They may include deficiencies or excesses in the diet, obesity and eating disorders, and chronic diseases such as cardiovascular disease, hypertension, cancer, and diabetes mellitus. Nutritional diseases also include developmental abnormalities that can be prevented by diet, hereditary metabolic disorders that respond to dietary treatment, the interaction of foods and nutrients with drugs, food allergies and intolerances, and potential hazards in the food supply. All of these categories are described in this article. For a discussion of essential nutrients, dietary recommendations, and human nutritional needs and concerns throughout the life cycle, see nutrition, human.
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