Due to the advantages of spray drying, such as short process, ability to handle heat-sensitive materials, and easy enlargement, it has been applied in many fields. After the reform and opening up, a large number of specialized drying equipment enterprises have emerged in our country. In the past ten years, the spray drying technology has made great progress, and the product quality has been comparable to that of world-renowned manufacturers. It not only meets the needs of domestic light chemical industry and environmental protection industries, but also expands to foreign markets.
For a long time, attention to spray dryer devices has generally focused on:
⑴ The choice of atomizer (machine);
⑵ enough air volume and heat configuration;
⑶ powder recovery and discharge.
The design of a successful spray dryer should include the way of hot air inlet and outlet and hot air distribution device that are compatible with the atomizer. The water evaporation rate in the drying tower increases with the relative speed of the mist and hot air.
In the design requirements of the hot air distributor, three important principles are put forward, all emphasizing the importance of hot air distribution for spray drying. In the subsequent installations, it was found that most enterprises still did not pay enough attention to it, but only achieved "similarity" in structure but did not grasp the essence, resulting in the following situations:
⑴ The temperature difference on the same cross-section in the tower is relatively large, resulting in partial sticking of the material to the wall;
⑵ Due to the unreasonable contact between the gas-liquid two-phase, the drying strength is greatly reduced, so the volume of the drying tower is getting bigger and bigger;
(3) In a drying tower whose processing capacity is much smaller than the original design, no attention was paid to the flow velocity range of the hot air distribution, which reduced the drying intensity, and a large amount of materials still stuck to the wall;
⑷ The thermal efficiency is very low, and it is difficult to reduce the wind temperature at the exit of the tower.
Therefore, we believe that whether the design of the hot air distributor is correct or not will directly affect the success or failure of the drying system. This paper intends to propose a reasonable way of gas-liquid two-phase contact on the basis of previous knowledge, in order to have a correct analysis and guidance for the design of the hot air distributor.
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