The advantage of superheated steam drying
1 Energy saving effect is remarkable
    The use of superheated steam as the drying medium energy saving effect has been confirmed by many scholars. Swedish scholar with a 0.2-0.5MPa pressure superheated steam drying of pulp per tonne of energy 0.4-0.5GJ, but with ordinary flash dryer was 3-3.5GJ, the cost per tonne of pulp $ 19 down to $ 10 by the UK's Thomas with superheated steam drier disc ceramic powder dyes dyes steam consumption per 1t spend from 20 pounds down to two pounds, saving up to 90%. Germany developed the high pressure superheated steam drier beet pulp, dried solids content of from 30% to 90% of the heat consumption, compared with the ordinary hot air drying is only reduced by the 5000kG/kg 2900kJ/kg. Niro developed a commercial company in 1985 with a pressure fluid bed dryer for drying granular or slurry tests proved compared with ordinary drum drying saving up to 90%, and non-polluting, product quality has been improved. Ireland and the former Soviet Union, the application called Peco superheated steam drier peat, unit energy consumption compared with conventional hot air drying dropped from 3000 a 40000kJ/kg 1700-1800kJ/kg. Sweden developed a superheated steam dryer for peat soil evaporation unit energy consumption of only ordinary hot-air drying of 1/6-1/7.
(2) can take advantage of the latent heat of steam, high thermal efficiency
    British scholars believe that, in general, water vapor around 84% of total energy latent heat, 16% of sensible heat. Traditional hot air dryers use a lot of dry material away from the evaporated water, the exhaust air contains a large latent heat of steam is difficult to recycle at a useful temperature. For example, the continuous paper. Most dryer, the exhaust gas containing 15% of water vapor, this saturation temperature of the exhaust gas 53 ℃. In order to recover this part of the latent heat required to cool to 40 ℃, or even lower. Most plants can not use such waste heat temperatures. The use of superheated steam drying, the exhaust air is still steam temperature was maintained at l00 ℃ above, may pass through condensation, compression and multi-stage drying to recover its latent heat.
    Superheated steam as drying heat recycling, thermal efficiency is very high, while the gas loss is zero leopard.
3 good quality dry products
    Using the superheated steam drying Another major reason is that the product quality is significantly improved. On the use of superheated steam drying improve product quality and grades, there are many reports abroad. 1920, Karor proved by experiments with superheated steam drying cabbage and forage products, colors remain bright. 1963 YoshNa and Hyodoo that acetate was dried with superheated steam, its strength as compared with the conventional drying methods have greatly improved. 1950, Kollmarm with superheated steam dryer for wood to be more are magic moisture content, drying in superheated steam drying textiles can avoid significant dye migration phenomenon. Tests showed that one kinds of coal with superheated steam drying 1/3-l/2 can extract the salt, as compared with the hot air drying, the coal in the combustion furnace to reduce fouling, thereby improving the level of coal. Salin relatively hot air with superheated steam and dried timber found that the former has a lower moisture content in addition, the bending strength and tensile strength are superior to the latter. Most of the material was dried in a hot air to form the hard shell.
And Tombiro Nomura and Tsutomov Hyodo superheated steam drying studies show no surface hardening, which is advantageous to heat and mass transfer. Them through air drying with superheated steam and - found that the former kind of instant noodles to form a porous structure is quickly softened in hot water, while the latter is relatively hard.
4 superheated steam heat transfer coefficient
    Superheated steam has a higher heat transfer coefficient. Potter and Keogh in a fluidized bed dryer for drying coal derived superheated steam heat transfer coefficient of 200-500W / (mmK), while stirring hot air dryer the heat transfer coefficient is only 20-50W / (mmK).
5 drying medium is steam, the mass transfer resistance
    Superheated steam drying, the entire environment there is only one gas component, evaporation of water from the material surface diffusion moves rather than by a qualitative difference in fluid pressure as a driving force generated by the volume flow, studies have shown that the 1mm diameter droplets 150 ℃ superheated steam only a very low differential pressure for the steam to provide sufficient driving force for diffusion. Therefore, in the actual process of steam removed from the particle surface resistance can be ignored. Superheated Steam Drying Genki film mass transfer resistance.
6 Specific heat capacity of superheated steam big steam with less
    Specific heat capacity of air is known as 1.005kJ / (kg · K), and the specific heat capacity of the steam 1.968kJ / (kR · K). A higher ratio of steam heat capacity, therefore, a certain amount of heat transfer desired mass flow rate less. Meanwhile, it can also help reduce the size and cost of the device. To reduce the mass flow of exhaust gas purification is very beneficial. Lane and stern such superheated steam in the discussion disc that continuous drying machine in the same conditions, as compared with the hot air drying, for reducing the volume of steam, dust reduction treatment, purification of exhaust gas used in the bag filter surface area is significantly reduced.
7 no explosion and fire hazard
    Superheated steam drying in the drying medium without the presence of oxygen, no oxidation and combustion reactions. Therefore, the high-temperature drying of coal and other combustible materials for no fire or explosion. Some can not be used for hot-air drying of food materials, can be dried with superheated steam. Up to - point hot air drying can not be compared.
8 superheated steam drying help protect the environment
    With the development of society, it is increasingly recognized the importance of the control environment. Superheated steam drying in confined conditions, for - some dry material does not pollute the environment. For example, with superheated steam drying of coal and pulp can reduce emissions of carbon dioxide and sulfur, dust content in the air is greatly reduced. Moreover, dried in hot air will be issued stench municipal waste, sludge and waste. With superheated steam drying odors are eliminated.
9 with superheated steam sterilization effect
    Superheated steam drying operation temperature of the material than 100 ℃. In this temperature for - these requirements sterilized food and medicine can not only dry, and can destroy bacteria and other toxic microorganisms.
In addition, because there is superheated steam extraction effect on some products can also be recovered from the condenser some useful chemicals. For example, some researchers reported drying of wood can be easily separated from the condenser turpentine.

 

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