Drying and gas or vapor contact with solids – Process – Gas or vapor pressure is subatmospheric
Patent
1997-02-26
1998-10-13
Doerrler, William
Drying and gas or vapor contact with solids
Process
Gas or vapor pressure is subatmospheric
34 92, F26B 504
Patent
active
058194363
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method for vacuum drying of a material, particularly timber or the like. The apparatus using the method comprises a drying chamber, a vacuum producing unit connected with the same, a cooler structure, and a compression unit.
BACKGROUND OF THE INVENTION
The present invention relates substantially to vacuum drying of a material, particularly timber. The process itself is generally known, wherein the pressure of the drying chamber is lowered in order to make evaporation of water effective in as low a temperature as possible, in view of power consumption, quality of dried wood and time needed for completing the drying process. A steam atmosphere as pure as possible is created in the drying chamber. Normally, drying is conducted by an ordinary vacuum pump. The drying process can also be made more effective particularly in the beginning by heating up the timber e.g. by blowing steam, particularly superheated steam into the drying chamber. For maintaining the steady condition of the drying process after the preheating stage, steam prevalent in the drying chamber is usually superheated by supplying heat to the drying chamber and by discharging steam from the drying chamber, whereby evaporation of water from the timber or the like can be continued. The drying chamber is externally connected to a condenser and a collector, where the steam removed from the drying chamber is condensed. The condensed liquid is removed from the collecting chamber e.g. by a conventional pump. The drying process can be accelerated, as mentioned above, by supplying supplementary energy to the drying chamber from the outside, e.g. by using heat exchangers placed inside the drying chamber, and also by cooling the condenser. In a conventional drying process, heat from the condenser is useful for a secondary purpose but its direct utilization in the actual drying process is impractical, because the temperature of the heat released by the condenser is lower than the temperature in the drying chamber.
In respect of prior art, reference is also made to the patents U.S. Pat. No. 4,753,016 and U.S. Pat. No. 4,194,296 disclosing solutions for raising the temperature of the steam released from the drying chamber in order to re-use heat energy discharged from the process in the drying process.
In U.S. Pat. No. 4,753,016, vacuum drying is developed in a manner that in addition to the actual vacuum pump used for producing a vacuum, the steam channel comprises upstream a separate compressor or a steam pump for raising the pressure and temperature of the steam coming from the drying chamber. Further, using a separate water circulation and a heat exchanger, the heat from the driving motors of the vacuum pump and the compressor is utilized by feeding the return water from the water circulation into an annular water pump used as the vacuum pump. When the drying process is effective and has a good operating efficiency, both compressors must be continuously operating and the liquid evaporated in the drying chamber must pass primarily through both compressors, whereafter the collected heat energy is re-used in the drying process.
The publication U.S. Pat. No. 4,194,296 discloses a vacuum pump producing steam sucked from the drying chamber, the heat of the steam being collected into a heat exchanger placed downstream from the vacuum pump, wherein a heat transfer medium used for heating the drying chamber is conveyed to the heat exchanger.
SUMMARY OF THE INVENTION
It is an aim of the present invention to improve the process of vacuum drying further in a manner that the heat energy of the steam produced in the drying process of a material, particularly timber, can be utilized efficiently. Consequently, the primary aim of the present invention is to raise the standard of technology in the field. For achieving these aims, the method according to the invention is primarily characterized in that steam is discharged from the drying chamber through a compression unit, that the pressure and temperature of the steam are ra
REFERENCES:
patent: 3574949 (1971-04-01), Farnsworth
patent: 3909957 (1975-10-01), Passey
patent: 4027401 (1977-06-01), Fairbanks, Jr.
patent: 4194296 (1980-03-01), Pagnozzi et al.
patent: 4260335 (1981-04-01), Marchal
patent: 4343095 (1982-08-01), Rosen et al.
patent: 4467532 (1984-08-01), Drake
patent: 4621437 (1986-11-01), Grande et al.
patent: 4644664 (1987-02-01), Bradshaw
patent: 4753016 (1988-06-01), Eichholz
Doerrler William
High Speed Tech Oy Ltd.
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