Abstract
The transport characteristics and kinetics of moisture in hot-pressing are crucial to controlling the insulated paperboard drying process. The effects of operating temperature (110, 120, and 130 °C) on moisture transfer characteristics of an insulated paperboard were investigated. The results showed that the hot-pressing process consists of four successive stages, i.e., the warm-up stage, the boiling-point temperature stabilization stage, the temperature slowly rising stage, and the constant temperature stage. It was observed that a higher temperature mainly affected the medium and later stages of the hot-pressing process. When the operating temperature increased from 110 to 130 °C, the maximum value of the drying rate increased by 16.04%, and the drying time decreased by 62.50% consequently. Furthermore, a new mathematical model used to describe the moisture transfer kinetics for the insulated paperboard hot-pressing was developed in this paper. The results from the proposed new model were evaluated with another eight commonly used models. It showed better predictions and satisfactorily described the moisture transfer kinetics of the insulated paperboard compared with other models under the investigated hot-pressing conditions. The values of R2, χ2, and root mean square error (RMSE) of the new model varied from 0.99961 to 0.99999, 0.00001 to 0.00005, and 0.00120 to 0.00599, respectively.
Highlights
The hot-pressing process of the insulated paperboard can be divided into four stages, i.e., the warm-up stage, the boilingpoint temperature stabilization stage, the temperature slowly rising stage, and the constant temperature stage, as presented in the temperature variation curves
We found that the peak of the drying rate was achieved in the boiling-point temperature stabilization stage
As the operating temperature raised to 130 °C from 110 °C, the maximum value of the drying rate was increased by 16.04%, and the drying time was decreased by 62.50%
Summary
Insulated papers or paperboards are made from cotton, linen, and kraft pulp or a mixture of these pulps [1,2]. Cellulose is the essential component of paper and pressboard [3]. The chief disadvantage of cellulosic material for electrical use is that it is hygroscopic and needs to be processed and maintained dry. The dry-out is worth the effort because dry cellulosic insulation has excellent dielectric properties. The web of wet fiber mats is dried mechanically and thermally between hot heated plates [4]. With the combined action of heat conduction and mechanical pressure, hot-press drying can effectively enhance the drying efficiency and improve the physical properties of the insulated paperboard dramatically
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