Waste Heat Integration of Coating Paper Machine Drying Process

Abstract

The paper sheet drying process consumes about 70% of the total energy required in coated papermaking, and almost all the thermal energy used in the process can be found in the exhaust air; thus, it has significant potential to recover the heat. With the aim of saving energy, the recovered energy is usually used to heat different process streams instead of steam.

This article examines the drying process of an operating coating paper machine to demonstrate an optimization method. To study the possibility of improving energy efficiency, thermodynamic analysis was conducted. The reasons why there is so much heat lost during drying were investigated. Based on the results of the energy and exergy analysis, a new waste heat integration scheme is presented. Furthermore, the performance of the proposed scheme has been evaluated. The results of the case study show an energy efficiency improvement of 7.3% and a specific energy consumption reduction of 4.6% with profitable investments.

Keywords:

• Coating paper machine
• Drying process
• Energy saving
• Waste heat

ACKNOWLEDGMENTS

The authors are grateful for the financial support provided for the project under Project No. 20070109–2 by the Guangdong–Hong Kong Key Field Researching Fund. They also are grateful for the valuable comments of the reviewers and editor, which improved the quality of the article. This study would not have been possible without the cooperation and assistance of Jingjiang Jia and the personnel at Gold East Paper Mill.

Notes

Note. The metrical data were tested using Testo 400 (Lenzkirch, Germany) multifunction test equipment, Fluke Ti40 (Everett, WA) thermal infrared imaging viewer, and Q2 Fluke 574 infrared thermometer. The pressure of the middle-pressure steam, low-pressure steam, and natural gas were 1.6, 0.6, and 3 MPa, respectively.

Note. The pressure of middle-pressure steam, low-pressure steam, and natural gas were 1.6, 0.6, and 3 MPa, respectively.