Due to the different requirements for chemical products, the type of
Drying Equipment is also different. At present, in chemical production, there are more than a dozen types of drying equipment that are used, and there are nearly 100 specifications. The commonly used types of dryers are: box type, tunnel type, belt type, air flow, spray, fluidized bed and vibrating fluidized bed, fluidized bed spray granulation, rotary, roller, vertical packed bed, vacuum rake, Vacuum double cone rotation, paddle type, microwave and far-infrared dry hunger, and the organic combination of the above two methods. Selection of Drying Equipment There are so many kinds of drying machines. How to choose it? A selection reference table is recommended here for reference. When selecting drying equipment, the following points should be noted. (1) Unless it has been proven in production, this type of
Dryer is suitable for the drying of the product. Otherwise, laboratory tests must be carried out and it is proved by tests that this kind of drying hunger is applicable. (2) When several dryers are applied at the same time, it is necessary to compare the equipment costs and operating costs, and choose the best one. (3) When a dryer can not meet the drying requirements, first of all think of a combination of drying methods, that is, combining two or three drying methods to complete the drying task. Such as air drying + fluidized bed drying; spray drying + fluidized bed drying (built-in) + fluidized bed drying + cooling (external); spray drying + belt drying; drum drying + fluidized bed drying; rotation rapid drying + Air drying and so on. Multi-stage drying can reduce the outlet temperature of the dryer and can save energy. two. Environmental protection issues During the drying process, the discharged gas or liquid may sometimes cause environmental pollution, and measures can be taken to eliminate the pollution. (1) Entrainment of dust in gas emitted by dust pollution may exceed environmental protection standards and cause environmental pollution. In this
Case, a two-stage dust-removal method can be used, namely a cyclone separator for the first stage and a bag filter for the second stage, and the dust removal efficiency can reach 99%. If the second stage is used for wet dust removal, such as Venturi tube, foam tower, spray tower, etc., when the washing liquid reaches a certain concentration, it can be sent back to the spray drying tower for spraying, or recrystallization, filtration, and then drying. In this way, there is no liquid pollution problem. (2) Gas pollution Sometimes the discharged gas has an odor. At this time, the second stage can use wet dedusting to wash (absorb) the odor of the gas. Or use a semi-closed loop method, where 15% of the total combustion exhaust is discharged, and the remaining 85% is recycled in the system, which can reduce the amount of exhaust gas treatment. (3) Noise pollution In a drying system, such as a rotary atomizer for spray drying, the noise generated by the friction between the high-speed rotating atomizer and the air is very large and may exceed 95 dB, therefore, the installation of atomization When the device is installed, sound insulation devices should be added. For large-scale installations, the noise of the blower and induced draft fan should not be ignored. The soundproof room should be equipped with a fan to reduce the noise in the environment. three. The energy-saving problem of drying operation In chemical production, the drying process is a unit operation that consumes a lot of energy. How to save energy is still a subject worthy of study. In the drying operation, the following measures can be taken to achieve the effect of energy saving. (1) Increase the air temperature at the inlet of the dryer. As far as the drying process permits, increase the inlet air temperature as much as possible. (2) Reduce the air temperature at the outlet of the dryer The lower the outlet temperature, the higher the thermal efficiency. But it is limited by the moisture content of the product. (3) Increasing the solid content and reducing the evaporation load This is the most effective way to improve the economics of drying. If the liquid solid content increases from 30% to 32%, the yield and thermal efficiency increase by about 9%. (4) Preheat the feed solution. (5) Reduce the leakage of air from the joint. (6) Preheat dry air with system waste heat (exhaust heat and product heat). (7) Use secondary or tertiary drying. (8) The internal heat exchanger is installed in the dryer to reduce the air consumption and reduce the operating cost. (9) Use part of the exhaust gas cycle. (10) Direct heat source heating, such as drying, is permitted. Flue gas can be directly used as drying gas to save energy. (11) Keep the drying equipment dry and reduce heat loss. In short, the quality of drying operations is directly related to the cost of chemical products and sanitary conditions in the production environment. It should be improved, transformed, and developed to make it more suitable for production needs and to better serve production.
