Infrared Radiant Heating Tubes for Directing Drying of Single-Layer Wood Panels to Solve Plywood Warping Issues?

Plywood or laminated wood is formed by pressing multiple layers of veneer bonded together. Veneers are obtained by rotary cutting wood logs into thin slices, typically about 1.5mm thick. After rotary cutting, the veneers undergo drying, cutting, sorting, pretreatment, adhesive application, and finally pressing into plywood. However, the drying of veneers consumes a lot of energy and limits the continuous production capacity and quality of plywood due to low yields.

Modern veneer drying has evolved from intermittent convection heating kilns to continuous production hot air belt dryers, roller dryers, and recently developed high-speed jet impingement roller dryers. The latter includes the latest jet impingement drum veneer dryer designed and manufactured domestically in China with technology imported from Germany, achieving a thermal efficiency of up to 38%. In contrast, heavy-duty belt veneer dryers currently produced in China typically have a thermal efficiency of less than 15%. To improve energy efficiency, reduce initial investment costs, and increase plywood production, there is a need to develop new types of veneer dryers.

As early as the 1990s, Canadian researchers chose medium-wave infrared heating tubes for veneer drying to compensate for the decreased performance of veneer dryers due to low-pressure steam from factory wood waste, increasing the overall thermal efficiency, drying rate, reducing space requirements, and facilitating temperature control. Combining conventional belt dryers with infrared dryers can effectively improve moisture diffusion, increase production yields, reduce energy consumption, and enhance thermal utilization efficiency. Chinese researchers have also studied the use of directional infrared heating tubes in conjunction with wood drying machines, achieving thermal efficiencies of up to 60%.

Firstly, it is essential to confirm the infrared absorption spectrum of veneers. Due to their thin thickness (1.5mm) and large exposed surface area, a significant number of capillaries are severed during veneer cutting, facilitating rapid moisture evaporation. Therefore, veneers can be radiated with high-temperature carbon fiber heating tubes to forcibly remove free water from cell lumens, reducing initial moisture content from 120% to 40%. Subsequently, drying the wood from 40% moisture content to 10% is accomplished using medium-wave carbon fiber heating tubes.

High-temperature carbon fiber heating tubes operate with a 1.5KW directional radiation scheme, achieving surface temperatures of 650℃ to 700℃, while medium-temperature carbon fiber heating tubes operate at 800W. High-temperature directional radiation rapidly dehydrates free water in the veneers, preventing surface circumference and warping. Therefore, in actual production processes, roller conveyors are used to transport veneers, enabling conductive and convective heat transfer, simultaneous drying, and flatness adjustment to ensure smooth, even, and aesthetically pleasing veneers post-drying.

Infrared drying of veneers using carbon fiber heating tubes exhibits a 58% higher thermal efficiency than comparable known equipment, with drying energy consumption per unit weight being only one-fourth of that of similar equipment. Specially designed roller dryers can also correct veneer warping caused by rapid drying, ensuring smooth, flat products. The overall equipment structure is compact, with high production efficiency, low investment, energy savings, and reduced pollution.

GlobalQT specializes in providing advanced infrared heating solutions to address challenges in wood panel drying. For more information, visit our website or contact us at: contact@globalquartztube.com.