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During all egg carton manufacturing process, 3.5~4 kg moisture content is dehydrated from every kilogram of finished product and lowered to 10%~12%. Therefore, drying process covers the major ratio in production cost and improvement of dry efficiency is the key measure to benefit.
Apart from taking advantage of natural condition such as sunshine and wind, adoption of hot air convection is another common drying method in pulp molding factory. To increase drying efficiency, the most effective method are improvement of drying facility condition and rational control of drying technology. No matter brick or steel cabinet, egg tray drying line is supposed to have good insulating layer to reduce thermal losses, and make sure uniform temperature inside. Temperature, humidity and flow velocity (flow rate) of hot air are three main parameters, which must be controlled logically.
1）Usually, temperature of hot air is controlled at 130~200°C, over-high temperature may improve drying efficiency to some extent, but lead to thermal degradation of plant fiber, and cause excessive shrinkage strain of molded pulp products
2）Humidity level exerts a tremendous influence on drying procedure. As the moisture carrier, hot air absorb and drain off moisture evaporated from wet products by the action of concentration difference of moisture between hot air and wet products. It’s favorable for improvement of drying efficiency by maintaining lower humidity in hot air. Generally stable humidity in hot air can be basically achieved by continuous fresh hot air supply and timely discharge of waste hot air.
3）During drying process, enough hot air is required to blow toward molded pulp products. It’s important to control flow speed of hot air rationally entered into drying facility. Usually 5 m/s should be maintained, and over-high speed will increase energy consuming while over-low decrease efficiency.