Evenly dry throughout

At its headquarters in Coniolo/IT, the Italian company I-Pan, a subsidiary of Gruppo IBL, is currently constructing a new OSB plant with a capacity of 120,000 m³/year (about 400 m³/day). It is planned to use poplar wood as the main feedstock which will partially be sourced from short rotation poplar plantations in Piedmont (10,000 ha). The annual demand is estimated to be 164,000 tons. The wood of the planted poplar will bring down the weight of the OSB by up to 30% compared to normal strandboards and will therefore be marketed as "LSB" – light strand board. For strand drying, Stela Laxhuber has installed a low-temperature belt dryer 1/6200-43,5 on the site. This will guarantee optimum treatment prior to the glueing process.

Benefiting from waste heat

Usually, drum dryers are used in OSB plants. They utilize hot waste gas from on-site firing systems. In Coniolo located in the Alessandria province, the case is somewhat different. In cooperation with Turboden, Brescia/IT, I-Pan installed a biomass ORC system Turboden 10 HR with an output of 999 kW_el. At only 85 °C, the waste heat of the system is, however, much too low for a standard drum dryer. "You have the same problem with tube bundle dryers – they require a much higher temperature as well", says CEO Thomas Laxhuber. The belt dryer is the only system that can operate at temperatures starting at 60 °C, he adds. Since the waste heat is available for free, Laxhuber expects the investment to pay off in less than three years' time.

Yet other benefits included

The strands are dried down with the belt dryer to a residual moisture content of less than 3%. "This is not a great challenge", says Laxhuber – and continues to point out other advantages of the technology: "You reach a levelled final moisture content throughout the strands in the belt dryer, since there is a clearly defined residence time – unlike in the drum with a static 'chance' which tends to put lighter parts faster and heavier parts slower through the machine. Band drying ensures complete and consistent drying which is enhanced by turning and mixing facilities."
In addition, the risk of fire is significantly lower as it is an indirect drying system using drying temperatures below 100 °C. "There are companies that consider one occurance of fire a year in drum dryers as normal. This is no joke, but a sad reality", says the managing director of Stela Laxhuber addressing a widespread problem. Also, there was no need to introduce Atex zones in the actual drying area because the dust concentration there is well below the explosion limit. According to Laxhuber, dust emissions are significantly lower as the band also acts as a dust filter. This renders cyclones or filters obsolete. Even the so-called "blue haze effect" does not exist at low temperatures like these. Below 150 °C, lignin vaporization and odor emission along with it do not occur." An intensive maintenance routine is usually required only once a year," says Laxhuber. This ensures complete and consistent drying results over a long period of time.

FACTS & FIGURES

STELA Laxhuber
Founded: 1922
Location: Massing/DE
Managing Director: Thomas Laxhuber
Employees: 90
Products: tower- and low-temperature belt-dryers, CHP waste heat utilization, feed-and-turn dryer, air heater, dust separator