Drying and gas or vapor contact with solids – Process – With contacting of material treated with solid or liquid agent
Reexamination Certificate
1999-12-06
2001-05-08
Wilson, Pamela (Department: 3749)
Drying and gas or vapor contact with solids
Process
With contacting of material treated with solid or liquid agent
C034S358000, C034S473000, C034S491000, C034S071000, C034S080000, C055S299000, C055S299000, C095S120000, C095S121000, C095S126000, C096S145000, C096S144000
Reexamination Certificate
active
06226888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for drying a gas by means of adsorption on a desiccant able to be regenerated, according to which method a gas is sent through a first amount of this desiccant, while a portion of the dried gas is sent through a second amount of already used desiccant for regenerating it, this gas portion for the regeneration being heated and after having taken up moisture is evacuated, whereby, after regenerating the second amount of desiccant, the gas flow is inverted so that the gas to be dried is sent through the regenerated second amount of desiccant, while a portion of the dried gas is now sent through the first amount for regenerating.
2. Discussion of the Related art
Methods of this kind are used amongst others for drying compressed gas, mostly compressed air. The compressed gas leaving the compressor has a relatively high moisture content. Part of the moisture is separated by cooling this air. The remaining moisture may be disadvantageous for the conducts and is undesirable for some applications.
A known method of this kind is disclosed amongst others in EP-A-0.419.433. The compressed air to be dried is dried in a first column, while the wet desiccant is regenerated in a second column by a portion of the dried compressed air. This portion is introduced, at half-height of the column, in the lower end of a tube mounted axially in the column and containing an electrical heating element. The gas is heated in the tube and flows in the wet desiccant at the top of the column, flows downward and leaves, charged with moisture, the column at the bottom.
It is evident that this heated gas causes a heating of the desiccant. Heated desiccant is however less effective than cold desiccant and therefore the regenerated desiccant is normally cooled before being used again for drying. If the desiccant is too hot when it is used for drying, a regeneration will start instead of drying. Cooling is also necessary to avoid dew point pikes during drying.
In said known method, this cooling is obtained by turning off the electrical heating while a portion of the dried compressed air is still sent through the desiccant.
In this way, the cooling can only take place after the complete regeneration of the desiccant and consequently the complete regeneration and cooling process is time-consuming. Moreover, an additional amount of already dried air is required for the cooling and is lost for consumption. This increases the energy consumption.
SUMMARY OF THE INVENTION
The invention seeks to provide a method for drying a gas avoiding said disadvantages and permitting to minimalize the energy consumption for regenerating the desiccant.
In accordance with the invention, this object is accomplished by heating the gas portion used for the regeneration in at least two successive steps, said steps being performed in different zones situated successively in the flow direction of the gas portion through the regenerating desiccant and by stopping the heating in a zone as soon as the desiccant in this zone is regenerated, so that this zone may already cool down by the gas portion for regeneration while a successive zone is still regenerated by the heated gas.
It is obvious that the first zone to be regenerated will be the zone where the gas portion for regeneration is entered as this gas portion has not yet taken up much moisture.
This is especially the case if the gas portion for regeneration is sent through an amount of desiccant in the opposite direction as the gas to be dried was sent when this amount was used for drying.
In this case said first zone is the zone which has taken up the less of moisture during drying.
The number of heating steps and consequently zones during regeneration may be higher than two.
Heating of the zones of the amount of desiccant which is regenerated may be performed in several ways, for example by electrical heating elements, but a very effective way of heating is by means of microwaves.
The invention also relates to a device which is especially suitable for applying the method according to either one of the preceding embodiments.
The invention concerns consequently a device for drying gas by adsorption, comprising an inlet pipe for the wet gas, an outlet pipe for the dried gas en between them at least two vessels mounted in parallel filled with a desiccant able to be regenerated, means for connecting the inlet pipe alternately with the inlet of one of the vessels and the inlet of the other vessel for drying the wet gas, means for returning a portion of the dried gas to the vessel which is not connected to the inlet pipe, for the regeneration of the desiccant and heating means in both vessels, said heating means comprising at least two heating elements which are situated successively in different zones in the flow direction of the gas through the vessel and which can be switched in or off separately, characterized in that the device comprises means for measuring directly or indirectly the moisture content in each zone and a control device connected to said means for commanding the heating elements individually in function of the moisture contents measured by said means.
Further prior art
U.S. Pat. No. 5,485,686 discloses a drying device with two vessels filled with desiccant able to be regenerated, a two heater coils being mounted in each vessel, one above the other. Only the bottom heater coil is switched on in a vessel when the air is dried therein, for heating the dried air to the optimal temperature for the use of the air, this is the drying of thermoplastics. During regeneration of the desiccant in a vessel, both heater coils are switched on.
According to the invention, preferably, the heating elements are microwave sources.
REFERENCES:
patent: 4127395 (1978-11-01), McKey et al.
patent: 4971610 (1990-11-01), Henderson
patent: 5123277 (1992-06-01), Gray et al.
patent: 5485686 (1996-01-01), Sears, Jr.
patent: 5581903 (1996-12-01), Botich
patent: 0 100107 (1984-02-01), None
Atlas Copco Airpower, Naamloze vennootschap
Bacon & Thomas PLLC
Wilson Pamela
LandOfFree
Method and device for drying a gas does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for drying a gas, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for drying a gas will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2553902