We generally drink tea in three ways: First, brew refined dry tea with hot water and drink it slowly. This method is still dominant in our country. Secondly, extract and mix the tea leaves into canned tea, open the lid and drink. Third, the active ingredients of tea are extracted, concentrated, and dried to make instant tea powder, which can be brewed and drank immediately to meet people's modern high-efficiency and fast-paced life needs.
The spray drying process for making instant tea powder: 1. Crush dry green tea: Crush the tea leaves with a grinder to obtain tea powder of about 40 mesh for later use. 2. Extract a certain amount of tea powder, and then add 0.5% β-cyclodextrin and 0.025% EDTA to prevent the loss of active ingredients. Then add a certain proportion of distilled water and perform extraction at a certain temperature and time. 3. Vacuum concentration: Filter the extract with filter cloth, then concentrate, and perform vacuum concentration at a vacuum degree of 0.95MPa until the dry matter content is about 20%. 4. Spray drying: Homogenize in a homogenizer to form an emulsion. During spray drying, the air inlet temperature is 200-220°C and the air outlet temperature is 85-90°C. Our company specializes in the production of spray dryers, high-speed centrifugal spray dryers, traditional Chinese medicine extract spray dryers, and pressure spray dryers.
Spray dryer is a drying equipment for processing solutions, suspensions or slurry materials. It uses a spray method to turn the material into mist droplets dispersed in the hot air. The material and the hot air contact each other in a co-current, counter-current or mixed flow manner, so that the water evaporates quickly to achieve the purpose of drying. Using this drying method, unit operations such as concentration, filtration, and crushing can be omitted, and granular products of 30 to 500 μm can be directly obtained. The drying time is very short, generally 5~30s. It is not only suitable for drying high-temperature resistant materials, but also suitable for heat-sensitive materials and materials that are easily decomposed during the drying process of the liquid material. It can effectively improve the fluidity and instant performance of the product.
The contact surface area of the gas and solid phases in the mist dryer is large, and the two phases flow in dilute phase, so the volume heat transfer coefficient is small, generally 100~400kJ/(m3⋅h⋅∘C). The hot air inlet temperature is 150~500℃ in parallel flow operation and 150~300℃ in countercurrent operation. The thermal efficiency of industrial-scale spray dryers is generally 30% to 50% (the thermal efficiency of spray dryers with waste heat recovery can reach 70%). However, this equipment only makes economic sense when the production capacity is greater than 100kg (water)/h and the exhaust gas temperature exceeds 100°C.
The basic process of spray drying is that the material liquid passes through the atomizer to form mist droplets dispersed in the hot air flow. The air is sent to the air heater for preheating through the blower, and then enters the spray dryer to be dried in contact with the mist droplets. Part of the product falls into the bottom of the tower and is separated from the gas, while the other part is sucked into the cyclone separator by the induced draft fan and then emptied after separation.
The products of spray drying are fine particles. In order to meet the requirements of environmental protection, sometimes it is not enough to use a cyclone separator in the system to separate the products and purify the exhaust gas. Generally, a bag dust collector is used for purification. Keep the dust content in the exhaust gas below 50mg/Nm3 (gas). Or use a wet scrubber to reduce the dust content in the exhaust gas to 15~35mg/Nm3 (gas).