At present, among many drying equipments, spray dryers are one of the widely used dryers, and are drying equipment for treating solutions, suspensions or mud materials. It can be directly dried from a liquid into a powder, which is a great advantage of the spray dryer; low thermal efficiency, large volume, low productivity, and high investment are its disadvantages. Spray drying is widely used in chemical, light industry, food and other industries because of its special advantages in powdery products with uniform composition from solution or suspension. In the chemical industry, it is widely used in the dye industry.
The working principle of the spray dryer is: spraying the material into droplets by spraying to disperse in the hot air, and the materials are in contact with the hot air in a cocurrent, countercurrent or mixed flow manner, so that the water is quickly evaporated to achieve the purpose of drying.
By using this drying method, unit operations such as concentration, filtration, and pulverization can be omitted, and a granular product of 30 to 500 μm can be obtained. Moreover, the drying time is short, and the drying time is generally 5 to 30 s. Spray drying is suitable for the drying of easily dispersible materials in high heat sensitive materials and liquid concentration process, and the product has good fluidity and fast solubility.
In the spray dryer, the gas-solid two-phase contact surface area is large, but since the gas-solid two phases flow in a dilute phase, the volumetric heat transfer coefficient is small, generally 20~100kcal/m3·h·°C, and the hot air inlet temperature is cocurrently operated. The time is 250~500°C, and the countercurrent operation is 200~300°C. Industrial scale spray dryers typically have a thermal efficiency of 30% to 50%. Spray drying with waste heat recovery abroad can achieve a thermal efficiency of 70%, but this equipment is economically significant only when it has a production capacity of more than 100kg (water) / h.
The flow of the spray dryer is: the feed liquid passes through the atomizer, and the spray mist is dispersed in the hot air flow. The air is sent to the air heater by a blower to heat, then enters the spray dryer and is dried in contact with the droplets. Part of the product falls into the bottom of the tower, and part of it is sucked into the first-stage cyclone by the first-stage induced draft fan. After separation, the exhaust gas is vented. The products from the bottom of the tower and the products collected by the cyclone are taken out by a secondary blower and separated by a secondary separator.
The products of the spray dryer are fine particles. In order to meet the requirements of environmental protection, the spray drying system only uses a cyclone to separate the products. It is not enough to purify the exhaust gas. Generally, it is also purified by a bag filter to make the dust in the exhaust gas. Below 50mg/m3, or with a wet scrubber, the dust content of the exhaust gas can be reduced to 15~35mg/m3.
The working principle of the spray dryer is: spraying the material into droplets by spraying to disperse in the hot air, and the materials are in contact with the hot air in a cocurrent, countercurrent or mixed flow manner, so that the water is quickly evaporated to achieve the purpose of drying.
By using this drying method, unit operations such as concentration, filtration, and pulverization can be omitted, and a granular product of 30 to 500 μm can be obtained. Moreover, the drying time is short, and the drying time is generally 5 to 30 s. Spray drying is suitable for the drying of easily dispersible materials in high heat sensitive materials and liquid concentration process, and the product has good fluidity and fast solubility.
In the spray dryer, the gas-solid two-phase contact surface area is large, but since the gas-solid two phases flow in a dilute phase, the volumetric heat transfer coefficient is small, generally 20~100kcal/m3·h·°C, and the hot air inlet temperature is cocurrently operated. The time is 250~500°C, and the countercurrent operation is 200~300°C. Industrial scale spray dryers typically have a thermal efficiency of 30% to 50%. Spray drying with waste heat recovery abroad can achieve a thermal efficiency of 70%, but this equipment is economically significant only when it has a production capacity of more than 100kg (water) / h.
The flow of the spray dryer is: the feed liquid passes through the atomizer, and the spray mist is dispersed in the hot air flow. The air is sent to the air heater by a blower to heat, then enters the spray dryer and is dried in contact with the droplets. Part of the product falls into the bottom of the tower, and part of it is sucked into the first-stage cyclone by the first-stage induced draft fan. After separation, the exhaust gas is vented. The products from the bottom of the tower and the products collected by the cyclone are taken out by a secondary blower and separated by a secondary separator.
The products of the spray dryer are fine particles. In order to meet the requirements of environmental protection, the spray drying system only uses a cyclone to separate the products. It is not enough to purify the exhaust gas. Generally, it is also purified by a bag filter to make the dust in the exhaust gas. Below 50mg/m3, or with a wet scrubber, the dust content of the exhaust gas can be reduced to 15~35mg/m3.
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