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Paper drying is a highly energy-intensive and complicated multivariate process. The dryer section plays an important role in the energy consumption of a paper machine, especially of thermal energy. A comprehensive method for assessing the energy performance of the dryer section was investigated in this study to improve energy efficiency. This method was divided into three component processes: energy and evaporation load audit, field test and observation, and energy flow analysis and energy efficiency estimation. In a case study, we found that the method could, in addition to analyzing the key factors that restrict drying efficiency, also depict the details of energy consumption clearly. At the same time, several significant energy-saving measures were suggested to improve the energy efficiency of the paper-drying process. [ABSTRACT FROM PUBLISHER]

A general, dynamic model describing the drying mechanisms of paper has been developed. The model includes shrinkage and predicts temperature, moisture, and pressure profiles. It has been evaluated against steady-state as well as dynamic measurements on a multicylinder paper dryer. The results revealed critical sections where low web strength and maximum gas pressure occur. Measurements of the outer cylinder temperature provide reliable information on the accuracy of the predicted moisture profile since they show the position where the paper surface is dry. [ABSTRACT FROM AUTHOR]

This article examines dynamic behavior of impingement drying. Dynamic relations between the drying variables and the paper moisture are determined and interactivity between the process variables is defined. According to the results, impingement drying is interactive and therefore an advanced control strategy is developed which is based on multivariable model predictive control. The performance of the proposed control strategy is studied by simulation and the simulation results are compared with the simulation results of the present control scheme. [ABSTRACT FROM AUTHOR]

Based on the earlier studies the most common empirical correlations in the literature predict the impingement heat transfer coefficients rather well at low (close to 100°C) temperatures, but get inaccurate at higher temperatures. Impingement temperatures used in paper drying applications are typically 300 to 700°C, and there has been a need to improve the existing heat transfer correlations at high temperature area. This study presents experimental results of impingement heat transfer measurements with a laboratory-scale heat transfer test rig. Five nozzle configurations were measured. The parameters varied in the investigation were nozzle-to-plate distance, nozzle open area, nozzle diameter, impingement velocity and impingement air temperature. Regression model of heat transfer was developed based on the measurement data. A correction factor including the impingement and heat receiving surface temperatures is proposed. The correction factor can be used to improve the existing correlations at large jet to heat receiving surface temperature differences. [ABSTRACT FROM AUTHOR]