The starch material that has been dehydrated usually still contains a large amount of water. According to the nature of the starch material, the water content is generally between 35% and 45%. Dehydrated materials cannot be stored or transported for long periods of time. Drying is also a powdery shape, which has the characteristics of long drying time and not easy drying. In these cases, it is necessary to perform dehydration again. The re-dehydration of wet starch is the drying process in the production process. There are many forms of starch drying. Common methods and equipment are:
1. Natural drying method
Use natural hanging bags to dry the starch to reduce the water content of the starch. The starch dry powder is in the form of granules. The advantage is that the operation method is simple, and there is almost no cost, and it is suitable for small-scale starch drying of farmers. The disadvantage is that the drying time is long, the weather is greatly affected, the sanitary conditions are poor, the secondary pollution is easy, and the labor intensity is large.
2. Drying room drying method
In addition to the natural drying method, the lower cost is also the drying method of the drying room. There are also many ways to heat the drying room. The easiest is to use a hot air oven outside to heat the cleaned air to the room for heating. In this way, the temperature is relatively easy to control and the air is clean. The temperature in the chamber is maintained at 50-55 degrees by hot air delivery. The bracket of the starch tray is reasonably set indoors. The indoor volume can be large or small. At the top of the oven, several exhaust fans are provided to regulate the temperature and humidity in the room. The drying time of the starch in the drying room depends on the dryness and wetness of the starch, but generally does not exceed 15 hours. The advantage of the drying method of the drying room is that the investment is small, and the drying room can be used as a drying room for the noodles. The disadvantages are low production efficiency, long time consumption, high labor intensity, uneven product drying, large indoor temperature change, and easy gelatinization of starch.
3. Belt drying method
The belt drying method uses a stainless steel mesh belt or other material tape to make a conveyor belt, which runs at a low speed. It is dried by hot air in the drying room to reach the specified water content and then output from the tail end of the drying room. This drying method is different from the aforementioned drying oven method in that clean hot air is blown into the drying chamber through a fan. It is usually divided into multiple drying sections, usually three sections. The first section is the low temperature zone, also known as the pre-dry zone. Mainly because the speed of vaporization of free surface moisture of starch drying is not the same as the speed of diffusion of internal moisture (also called outer diffusion). In order to avoid the excessive temperature increase affecting the quality of starch, "moisturizing drying" is adopted. As the delivery temperature of the conveyor belt gradually increases, the moisture of the starch has been reduced a lot, thereby preventing starch gelatinization. In the final stage, the temperature is lowered again, and it is also possible to blow only the cold air to lower the temperature of the starch to complete the entire drying process. The advantage of belt drying is that the investment is small, and it can be operated continuously, and the drying efficiency is relatively high. The disadvantage is that the production capacity is small and the drying room is large.
4. Airflow starch dryer
Airflow dryers commonly used in the starch industry. Airflow drying, also known as "instant drying", is the application of dilute phase transport in solid fluidization for drying. The method is to directly contact hot air with the solid particles to be dried, and suspend the solid particles (starch) to be dried in the fluid. Therefore, the contact area of the two phases is large, and the process of heat and mass transfer is enhanced, and the airflow is applied to the drying unit operation of the bulk material.
The airflow dryer developed by GOODWAY adopts advanced technology such as high-efficiency heat exchanger, digital temperature detection and stepless variable speed fan to adjust the furnace temperature after fully considering various factors such as turbulent motion of airflow, cyclone separation and heat exchange. The device has the following features:
1. The entire system uses automatic control. Through the measurement of the feed moisture and temperature difference, the feed amount and the intake air amount are automatically adjusted to ensure the stability of the product moisture.
2. The heat efficiency is high, the drying time is short, the processing amount is large, and the airflow drying adopts gas-solid two-phase cocurrent operation.
3. The use of variable diameter turbulence technology improves the performance of the equipment and ensures the quality of the starch.
4. The airflow dryer has a simple and compact structure, small volume, large production capacity, and low investment and maintenance costs.
5. The operation is convenient, and the unit processes of drying, pulverizing, sieving, conveying, etc. are jointly operated in the airflow drying system.
6. It has a wide range of applications and can be applied to a variety of powder, flake and granular materials.
Air flow drying range
1. Material status, air flow drying requires powder or granular materials. The particle size of the particles is generally from 0.5 mm to 0.7 mm, and at most not more than 1 mm.
2. It is suitable for the combination of moisture and material. The airflow is dried by using a high-temperature high-speed gas as a drying medium, and the contact time between the gas-solid two phases is short.
3. The equipment is widely used for drying granular materials such as starch and grain.
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