Zhejiang Forest United Paper’s PM 6: Pioneering OptiDry Coat double-pass air drying technology

Taizhou, China – Zhejiang Forest United Paper has successfully started up its PM 6 board machine featuring the world’s first OptiDry Coat double-pass air drying technology, supplied by Valmet.

The PM 6 machine, commissioned in February 2025, was installed to address a capacity gap in coated white lined chipboard production. The new line produces a range of board grades, including gray-back white lined chipboard, kraftliner, and coated kraftliner, with basis weights from 230–240 g/m² up to 340–390 g/m².

Valmet’s delivery included four headboxes, a top forming unit, four coating stations, and multiple air dryers, including the OptiDry Coat double-pass system. This new technology combines three air drying stages—high-intensity drying, non-contact web turning, and moisture stabilization—into a compact solution.

According to the company, the double-pass system has improved drying efficiency, operational stability, and product quality while reducing machine length and civil construction costs. The system has also addressed board curling issues, resulting in improved flatness and positive customer feedback.

“The paper web runs through very smoothly, and drying performance is excellent,” said Xiaobin Chen, Deputy Production Director at Zhejiang Forest United Paper, noting gains in efficiency and machine compactness.

Automation plays a key role in the operation of PM 6. The Machine Control System (MCS) automatically adjusts process parameters such as web positioning and pressure, ensuring stable production and ease of use for operators.

In addition, the supplied OptiFlo headboxes have enabled high levels of surface smoothness and printability, supporting consistent performance across multiple printing methods.

The project reflects close cooperation between the two companies, with Zhejiang Forest United Paper citing timely delivery, efficient commissioning, and responsive service throughout the implementation process.