Moisture control of spray-dried products
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Experienced experts, please give us some advice. Our pressure spray dryers are used to produce animal protein, and the moisture content has always been between 3-4%, with values as low as 2% and as high as 5%. However, our customers require that the moisture content be below 8%, which reduces our profit margin and increases energy consumption. Especially with the hot weather lately, a large amount of protein powder is discharged from the exhaust fan outlet, which is significantly more than before.
Spray drying operates on the principle of flash evaporation. The degree of drying of the material depends mainly on the control of the inlet air temperature. After operating for a while, the moisture content of the material and the output volume remain within a certain range – typically between 2% and 5%, as you mentioned. Generally, the moisture content of the material produced by spray drying is relatively low; it’s difficult to achieve a moisture content of 8%. The material tends to stick to the air ducts, which reduces the production volume and increases energy consumption. By lowering the inlet air temperature, increasing the exhaust air volume, and keeping proper records, it’s possible to find the most suitable settings. This requires trial and adjustment on-site. Additionally, the presence of material in the exhaust fan, as you mentioned, is abnormal; it indicates that the bag filter ahead isn’t functioning properly. It’s necessary to perform backwashing or cleaning of the bags at appropriate times
In my opinion, the exhaust volume should be reduced and the outlet air temperature lowered in order to increase the moisture content of the product; a high moisture content in proteins can cause them to stick to the walls.
1. Control of inlet air temperature. 2. Feed temperature and solid content. Feed rate. 3. Energy consumption is divided into two main parts: power and heat energy. Increasing the moisture content of the finished product reduces the energy consumption per unit. 4. If the secondary dust removal system uses bag filters and there is a sudden increase in dust emissions, it may be that some of the bags are damaged.
Your problem is most likely that the cloth bag is damaged. Our equipment was upgraded only last year