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Focusing on the research, development, and application of energy-saving and emission-reduction technologies, with deep expertise in energy efficiency and consumption reduction within the ventilation and drying segments of the paper-making industry.
Yankee hood drying principle | Why high-speed crescent‑shaped tissue paper machines are standardly equipped with a Yankee hood
Release date:
2026-10-23
Source:
The Yankee cylinder itself relies on contact heat transfer, which has an inherent limit to its heat‑transfer efficiency; the higher the machine speed, the more pronounced this limitation becomes. The Yankee hood, by contrast, employs forced‑convection hot‑air drying. Once temperature and humidity are properly set, the hot air is directed through nozzles onto the wet paper web adhered to the cylinder surface. At high speeds, the hot air stream breaks through the saturated vapor film on the paper surface, reducing resistance to moisture evaporation and thereby accelerating the drying process. Unlike conventionals, the airflow in a Yankee hood is configured to conform to the curved surface of the drying cylinder, flowing smoothly along the cylinder wall without random turbulence, thus preventing thin tissue paper from being blown about by the airstream.
The entire hot-air circulation process is actually quite straightforward. Fresh air first passes through a heat exchanger to be heated to the process‑required temperature, then enters a pressure‑equalizing plenum for stabilization before being sprayed onto the paper web via nozzles. As the moisture in the paper evaporates, it mixes with the airflow, forming a high‑humidity exhaust stream that is removed by the exhaust section. A portion of this moist, hot air is routed to a heat recovery unit, where its thermal energy is captured to preheat the incoming fresh air, significantly reducing steam consumption; the remaining moisture is discharged directly. Ventilation in the felt zone is typically designed in conjunction with the hood system to balance airflow on the front and back sides of the paper web. Many on‑site issues—such as paper drift and uneven wrinkling—stem from improper airflow control, a factor that becomes especially critical on high‑speed winder machines operating at speeds around 1600 m/min.
On low-speed tissue paper machines, heat transfer from the Yankee cylinder alone is usually sufficient to meet drying requirements. However, as machine speed increases, the amount of furnish passing through per unit time grows significantly, sharply raising the dewatering load; relying solely on Yankee cylinders then becomes inadequate. The advantages of composite drying are substantial: it enables higher production rates, allows for precise control of drying uniformity, and improves the consistency of basis weight and creping performance in tissue paper. Conversely, if the airflow design is poorly executed, localized variations in moisture content can easily occur, leading to defects such as streaks and color differences.
Here, it is worth noting that the Yankee hood is primarily designed for use with crescent‑shaped tissue paper machines. It operates on the curved surface of the Yankee dryer cylinder and differs from the operating conditions of hot‑air drying ovens used in coating processes or other enclosed hoods; therefore, they should not be conflated.
Ultimately, the core value of the Yankee hood lies in leveraging controlled convective drying to overcome the limitations of heat conduction in the dryer cylinder. Whether for new projects or energy‑saving retrofits of existing lines, details such as nozzle arrangement, sealing, and airflow simulation all have a significant impact on subsequent energy consumption and operational stability. Zhengding Environment We have successfully supported numerous new crescent‑type paper machines with varying web widths and high speeds, and can provide integrated solutions for Yankee hood systems, hot air drying, and dust collection.
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