7 Photo: Christina Brandin Englund, Svenskt Trä PRINCIPLE The timber is dried during transport through the various climates in a drying channel that has 2 separate zones. Once loaded on trolleys, the timber is fed into the channel from a buffer track at the kiln’s input end. A fully automatic feed system carries the wood through the stainless steel kiln and out through its output end. Via heat coils, axial fans in each zone blow circulation air through the timber. In the first zone, the air is blown in the opposite direction to timber travel. In the second zone, it is blown in the same direction as timber travel. Advantages of this kiln type 2-zone kilns offer both improved quality and greater capacity. In principal, the first zone acts like a short 1-zone continuous kiln where the air is humidified more quickly. This reduces surface drying and thus the risk of checks at the input end. The second zone acts as a balancing zone to reduce moisture content variation. Capacity and drying economy By collaborating closely with researchers and customers, we have developed 2-zone models that ensure the optimum use of capacity and the very best drying economy. To their advantage, the kilns can also be equipped with a heat recovery system. Everything from the building's structure to technical solutions and the control system is based on a combination of expertise, experience and advanced international research (see Technical Solutions on page 14-15). Lumber types and capacity Valutec’s 2-zone kilns were especially developed for small- dimension lumber and center lumber and have an annual capacity of up to 100,000 m3 (42.5 MMBF) and a target moisture content down to approx 8–18%. Drying takes place in two separate zones in the 2-zone continuous kiln. This type of kiln is also known as FB (Feedback), as the climate in zone 2 is fed back to zone 1, where general ventilation takes place.
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