Specialized and Custom Designed Dryers
Direct, indirect and combination systems for special applications can be accommodated within the range or by custom design.
The technology behind microwave drying relies on the polarity of the moisture molecule. Water which is a dipolar molecule (and perhaps the most common asymmetrically charged molecule) reacts to the microwaves, while non polar molecules do not. Microwaves also penetrate to the center of the product, being unaffected by shadows or product density. The molecules react by trying to to align themselves to the electromagnetic charge. Because the microwaves’ electromagnetic field reverses at an enormously high frequency (as much as a couple billion times per second), the dipolar molecules continually change alignment, producing energy that is converted into heat. In effect, the water molecules heat themselves until the product becomes so hot that the water evaporates. Microwave dryers can be incorporated into a number of standard configurations, such as cabinet, conveyor and tray type systems. Vapors formed by the process must evolve and not be 'trapped' or they will 'explode' out. The evolved vapors need to be able to be extracted from the system.
In freeze drying one usually requires to sustain some property of the feed for final product. Therefore one needs to freeze the product to stabilize its structure. The product is frozen to the temperature of the lowest constituents freezing point and then the drying chamber is evacuated to promote sublimation (the changing of a solid to a vapor without going into the liquid stage). The vapor is expelled through the vacuum pump.
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