The multi-channel cylinder dryer (MCD) is designed to improve heat transfer. Although there are numerous research studies on the pressure drop, heat transfer characteristics, and flow pattern in static state of MCD, there is little research on the flow pattern in the rotating state. In this paper, the distribution of flow pattern in MCD under different rotating speeds and steam mass flow rates is studied. Furthermore, the logistic regression method (LR) is used to predict the flow pattern diagrams. The results show that in the front section of the flow channel, the flow pattern is basically annular flow, which is not affected by mass flow rate and rotating speed. On the other hand, wavy flow, vortex flow, slug flow, and bubble flow can be observed when the fluid enters the middle and the end section. The higher the rotating speed and the steam mass flow rate, the more the flow pattern tends to be an annular and wavy flow. At the end of the passage, the flow pattern is mainly slug flow. The predicted flow pattern diagrams are in good agreement with the experimental result, and to obtain an effective flow pattern in the middle and the end section of the flow channel, the influence of increasing rotating speed is greater than that of increasing steam mass flow rate. However, the specific rotating speed, steam mass flow rate, and other parameters should still be set by combining with the actual situation. This work can provide some references for the further study of MCD flow characteristics. © TAPPI Press 2023.

With the purpose of improving molded pulp product (MPP) drying process, the present work investigated the microwave drying performance of MPP under the power level of 500 W and compared that with the convective drying method. The drying kinetics, the effective moisture diffusivity, and the energy consumption of the two drying methods were evaluated respectively. It was found that the drying time was shortened from 22.0 min for convective drying to 16.0 min for microwave drying due to 27% of drying rate enhancement, and the effective moisture diffusivity was increased from 3.01×10-10 to 4.49×10-10 m2/s. Additionally, 88% of energy consumption could be saved in the microwave drying process. An artificial neural network (ANN) was employed to predict the moisture removing kinetics of MPP. The results revealed that the ANN modeling could be used to predict the drying kinetics of MPP effectively and then determine the moisture content in the drying process. © 2023 Korean Technical Assoc. of the Pulp and Paper Industry. All rights reserved.

造纸作为典型的资源和能源密集型产业一直以来是产业优化升级和节能减排所关注的热点,而干燥作为能源消耗最高、碳排放密度最大的操作单元则是实现造纸过程节能降耗的关键,同时也是影响纸张物理性能的重要工序。纸张干燥特性及其动力学的研究对于实现造纸过程提质增效和节能减碳有着重要的意义。本文以不同打浆度和浆料配比抄造的定量为60g/m2的纸张为研究对象,采用差示扫描量热分析（DSC）和热重分析（TGA）方法,通过干燥过程中水分分布和孔隙分布的定量分析,对纸张的干燥特性和动力学开展了以下几方面的研究:采用DSC技术对纸张干燥过程不同类型水分分布特性进行了探究。结果表明,根据不同状态水分的热力学特性,可将纸张内部水分划分为非结合水、冷冻结合水和非冷冻结合水;随着打浆度的升高,或在低打浆度（20±3°SR）条件下添加阔叶木纤维,纸张中非冷冻结合水的占比逐渐升高,冷冻结合水的占比则逐渐下降;而在高打浆度下（80±3°SR）,非冷冻结合水与冷冻结合水的占比均随阔叶木纤维含量的增加而减小,不同工艺参数对水分分布的影响变化幅度均在20%以内。基于DSC技术研究了干燥过程纸张内部孔隙分布情况。结果表明,18°SR纯针叶木浆抄造的纸张孔隙中水分总量在干燥过程中逐渐减少,由0.6893降至0.0538g水/g纤维,并且伴随着孔径缩小,孔径为28.42～81.26nm孔隙的占比约减少58%;打浆度和纤维种类是影响纸张孔隙结构的重要因素,研究发现当打浆度由18°SR升高至77°SR时,孔隙总量明显减少;当浆料中阔叶木浆与针叶木浆配比为40:60时,孔隙总量最少。采用TGA技术对纸张在不同温度（80～120℃）下的等温干燥特性和动力学进行了研究。结果表明,纸张等温干燥过程包括升速、恒速和降速三个阶段;温度对纸张干燥过程影响明显,当由80℃升高至120℃时,干燥时间约缩短56%;打浆度或阔叶木浆占比越高,干燥速率越小,所需干燥时间越长;基于常见的8个干燥动力学模型,提出了与实验数据拟合度最高的新模型,可以用来描述纸张等温干燥过程水分的变化情况;计算得到纸张等温干燥平均活化能为23.997～26.638kJ/mol,且随着含水率的降低干燥活化能由21.896kJ/mol升高至54.094kJ/mol;另外,打浆度主要影响非冷冻结合水干燥阶段活化能大小,浆料配比则对冷冻结合水与非结合水干燥阶段影响更大。应用TGA-DSC技术对纸张在不同升温速率（5、10、15K/min）下的非等温干燥特性和动力学进行了研究。结果表明,纸张非等温干燥过程包含升速和降速两个干燥阶段;当升温速率由5K/min提高至15K/min时,可缩短约58%的干燥时间,并节省约8%的干燥能耗;相同升温速率条件下,打浆度越高、阔叶木浆占比越高,所需干燥时间越长,干燥能耗就越高;Midilli and Kucuk模型可较为准确地描述非等温干燥过程中纸张内部水分的变化规律;分析发现F1模型可用于表达纸张非等温干燥过程失重特性,在实验条件下,纸张干燥过程降速阶段干燥活化能明显高于升速阶段,15K/min升温速率下18°SR的纯针叶木浆纸张升速阶段干燥活化能约为47.993kJ/mol,降速阶段则为63.997kJ/mol,并且随着升温速率降低至5K/min、打浆度提升至77°SR或者阔叶木纤维含量的升高至80%,干燥活化能呈现上升的趋势。本文基于热分析方法对纸张等温和非等温过程的干燥特性及动力学展开了研究,揭示了干燥过程中纸张内部水分分布和孔隙分布的变化特性,研究了干燥条件和浆料工艺参数对纸张干燥特性和动力学的影响,可以为建立合理的干燥模型提供科学依据。

The transport characteristics and kinetics of moisture in hot‐pressing are crucial to con-trolling 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 val-ues 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. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

The product could not be effectively expanded and the puffing temperature was too high, which usually occurred during the explosion puffing drying process of fruits and vegetables. CO2 high-pressure and low-temperature explosion puffing drying technology was investigated as potential means for the production of apple snack food. The samples were pre-dried with hot air to a moisture content of 15% to 20% (w.b.). The process factors including puffing pressure difference (0.86–1.54 MPa), puffing temperature (53–87 °C), and vacuum drying time (28–62 min) were investigated using response surface methodology with central composite design. The optimum CO2 high-pressure and low-temperature explosion puffing drying conditions were puffing pressure difference, puffing temperature, and vacuum drying time of 1.25 MPa, 74 °C, and 33 min, respectively. At this optimal condition, expansion ratio, rehydration ratio, and crispness were found to be 1.7, 2.23 g/g, and 29.3, respectively. Apple crisps obtained under optimal processing conditions have a highly porous structure from SEM micrographs. © 2020, © 2020 Taylor & Francis Group, LLC.

项目主要以纸张(纸板或浆板)为研究对象，研究在干燥过程中发生在其内部的水分迁移蒸发特性和热质耦合传递机理。主要研究了纸张内水分分布形态及其孔隙结构变化特性，建立了描述水分迁移的传质本构关系；实验确定纸张干燥过程的动力学特性，并对其动力学模型进行了综合分析；通过结合传统的纸张不同干燥方式，建立热质耦合传递模型，考察了不同干燥因素的影响规律，研究阐明了干燥过程中纸张孔隙结构特性决定的水分传递机制；建立了造纸干燥实际过程的能量模型，实现了对造纸干燥过程的数值模拟；根据纸机干燥部实地测试数据，对比分析了数值模拟结果与实验结果的差距，验证了热质传递模型，通过模型仿真，研究了干燥部结构和操作参数对造纸干燥性能和能效水平的影响，阐明了某些关键变量对纸页干燥过程性能的影响，为指导实际纸张干燥过程的节能降耗工作提供了理论支持。

The drying characteristics of unbleached Kraft pulpboard have been studied in convective drying equipment under different hot air temperatures and velocities. In this work, the drying experiments were conducted in the range of 80-100 degrees C and 1.87-2.48m/s, respectively. The results indicated that high air temperature and velocity are beneficial to increasing drying rate and decreasing drying time. Ten thin-layer drying models were evaluated to describe the drying kinetic of unbleached Kraft pulpboard for its suitability. Based on the statistical analysis, the Yun model could predict the pulpboard drying kinetic better than others in terms of fitting performance. Through calculation and fitting, the effective moisture diffusivity varied from 2.077. 10-10 to 3.631. 10-10m(2)/s over the investigated temperature range and the average activation energy for moisture diffusion was 22.818kJ/mol.