Thermal drying of materials with internal pores is always a time-consuming and energy-intensive step within a production process. For chemical and pharmaceutical mass products and, in particular, for wood as an important raw material it is desirable to reduce the water content before thermal treatment by mechanical operations. The wood-processing industry, facing a rising stress of competition, is forced more than ever to offer high-quality products at lowest prices. Today, drying of timber is mostly done by air drying or by technical drying in kiln dryers. In any case, drying is necessary to prevent deterioration in quality by shrinkage, formation of cracks, discoloration or infestation. A new process of dewatering wood by combining mechanical and thermal means has been developed at the University of Karlsruhe. Compared to conventional drying processes, short drying times and a low residual moisture content can be achieved and, thus, energy consumption and costs can be reduced. In industrial wood drying only thermal processes (e.g., convective kiln drying, vacuum drying, etc.) have been established because so far no method has been known for removing liquid by mechanical force without significant change in wood structure. With the new I/D process chances for alternatives to conventional thermal drying or for mechanothermal applications are offered. Motivation and ObjectivesWood is one of the most extensive natural resources of the world, with 3.5 billion cubic meters of yearly turnover [1]. In the last years a strong stress of competition has come from former Eastern bloc countries tending to lower price levels on the wood market. Statistical data show a drop in turnover and a changing structure in the wood-processing industry in Germany. Though numbers of production companies are decreasing, the cutting quantities are increasing. The structural change in this branch seems to be just like in the chemical or automotive industries years before: the small traditional family business is changing towards large industrial enterprises. This market development forced many companies to examine the economical potential in order to reduce costs in production lines. Industry must open up to innovations in line with market requirements. Drying is one of the most important steps in the production process to preserve wood quality and stability of dimensions. To increase productivity in wood processing, heating and drying plants have to be improved because these plants are consuming the greatest amounts of energy.Market interests especially aim to reduce drying times and, closely bound up with that, to save energy required for heaters and fans. This is why vacuum drying and high-temperature drying are increasingly used [6].A new mechanical drying process for dewatering has been developed to overcome the drawbacks well known from conventional thermal drying processes. This new process is called ªI/D processº (incubation-decompression process) and uses compressed air. The effect and influence of process parameters like pressure l...
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