Electric heating – Microwave heating – Waveguide applicator
Reexamination Certificate
1999-07-16
2001-03-27
Walberg, Teresa (Department: 3742)
Electric heating
Microwave heating
Waveguide applicator
69, C034S420000
Reexamination Certificate
active
06207941
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method and device for the rapid drying of coated materials by the application of microwave energy. The invention may be used for the removal of water or organic solvents from coated materials, especially, but not limited to, continuous webs.
2. Brief Description of the Related Art
A variety of industrial products are manufactured in the form of long thin webs which are coated or printed. Examples of these products include wall coverings (e.g., wallpaper), plastic and paper packaging, published materials, textiles, photographic films, plastic transparencies, magnetic media and adhesive tapes. Typically, the coating of these products is performed with the use of a volatile organic compound (VOC) or water. Examples of VOCs that may be used in these processes include methyl ethyl ketone, acetone, toluene, alcohols, and chlorinated solvents. After the web material has been processed, the solvent used is typically removed, thus leaving the desired coating or printing on the web. The removal of these solvents from web materials is typically accomplished through a heating process.
All manufacturers of printed and coated web products are strongly affected by new provisions of the Clean Air Act, which mandate strict controls on the emission of VOCs to the atmosphere. The costs for a VOC emission control system tend to be strongly dependent on the degree of dilution of VOCs in an air stream. Since coated web material is conventionally dried by exposure to hot air streams, air dilution of the VOCs is normally inherent in the drying process. This dilution tends to create large volumes of air which typically need to undergo treatment before the air is released into the atmosphere.
Contaminated air streams are typically treated by either incineration or passage of the air through an adsorbent material. In a typical incineration procedure, the stream is heated to about 600° C. to decompose the VOCs. If the concentration of organics is too dilute, natural gas is typically added such that sufficient combustion may be achieved. It is therefore desirable that the stream of organic contaminants be concentrated before incineration, to lower the amount of additional fuel needed to effect destruction of organics. The use of an air stream with a higher concentration of VOCs requires less additional fuel and, therefore, less overall cost.
Alternatively, adsorbent materials may be used to remove the VOCs from the air. The contaminated air stream may be transferred to an adsorbent column. As the contaminated stream is passed through the column, the VOCs are removed. After the process is completed or when the adsorbent materials become saturated, the VOCs are typically removed from the adsorbent. The purification of the adsorbent is typically accomplished by heating the adsorbent materials to remove the VOCs from the adsorbent material. The removal of the VOCs from the adsorbent tends to be performed such that the VOCs are removed to form an air or inert gas stream containing a relatively high concentration of VOCs. An air or inert gas stream containing a relatively high concentration of VOCs is typically more economical to treat.
An alternate method of treatment of contaminated streams is by recovery of the VOCs from the air stream. To recover the VOCs, the air stream is typically passed through a cooling system which allows the VOCs to condense out of the air stream. The efficiency of recovering solvents in this manner tends to be dependent on the concentration of the VOCs within the air stream. To achieve an economically viable recovery system the VOCs typically need to be relatively concentrated.
In general, water-based coatings, while desirable due to the low toxicity of the solvent, are much harder to evaporate than volatile organic materials. A typical hot air drying system may require seconds to minutes to dry a coated web which has been treated with water. This may require relatively large heating systems which generate large amounts of relatively dilute contaminated air streams. It would be desirable to create a system which would allow a more rapid drying of water-coated web materials, thus creating a more concentrated contaminated air stream.
It is therefore desirable to create a system by which solvents, such as water or VOCs, may be evaporated from coated materials such that the solvents are carried from the materials in an air stream containing a relatively high concentration of the solvent. Additionally, it is further desirable that the drying be accomplished in a relatively short time span. By rapidly drying coated materials to form an air stream containing a relatively high concentration of solvent, both heating costs and waste treatment costs may be reduced.
SUMMARY OF THE INVENTION
The rapid drying of coated or printed materials may be accomplished by the use of microwaves propagated in a resonant chamber. The chamber may provide a uniform irradiation of microwave energy across the coated or printed material or an irradiation pattern tailored to the geometry of the product. In the context of this patent, “microwaves” are defined to be relatively short electromagnetic waves (e.g., electromagnetic waves having a wavelength of less than about one meter).
In an embodiment, a chamber for drying coated materials is formed from a body, a front wall, and a rear wall. The chamber, in one embodiment, has an elongated member made of a non-conductive material disposed in the central portion of the chamber. The body is, in one embodiment, formed from a substantially electrically conductive material. The inner surface of the body may be lined with a layer of an electrically conductive material. This layer of conductive material, in one embodiment, has a higher electrical conductivity than the material used for the body.
The chamber may have at least one slot, preferably two slots, formed in the body of the chamber to allow passage of a coated material. The slots may be oriented such that a coated material may be passed through a portion of the chamber. The slots are also may be configured to allow air to pass into the chamber at a controlled rate so that the concentration of combustible vapors within the chamber is maintained either above the upper explosive limit or below the lower explosive limit. The lower explosive limit is herein defined as the minimum concentration of a flammable gas or vapor in which an explosion may occur upon ignition in a confined area. The upper explosive limit is herein defined as the maximum concentration of a flammable gas or vapor in which an explosion may occur upon ignition in a confined area. Together, the lower and upper explosive limits define a range of concentrations in which an explosion may occur upon ignition.
The elongated member may be configured to be rotatable within the chamber and oriented so as to guide the passage of a coated material through the regions of highest electric field intensity. The elongated member may be positioned in the cavity such that the movement of the coated material against the outer surface causes the elongated member to rotate. In this manner the coated material may be passed through along the outer surface of the elongated member without causing frictional heat or electrostatic charge to build up along the outer surface.
The chamber may include an opening to allow microwave radiation to enter the chamber. The opening may be positioned in the center of the body. The opening may be positioned at any point along the longitudinal axis of the chamber. The opening may be configured to match the size and shape of a waveguide. The opening may be rectangular in shape. The broadwalls of the opening may be orientated perpendicular to the longitudinal axis of the chamber to allow the incoming microwave radiation to have the proper orientation to form the transverse magnetic resonance mode.
The chamber may be formed in two sections. The two sections may be separated to allow access to the interior of the chamber. This provides a convenient
Blessing Tyler
Davis John H.
Schmidt Philip S.
Conley Rose & Tayon PC
Meyertons Eric B.
Pwu Jeffrey
The University of Texas System
Walberg Teresa
LandOfFree
Method and apparatus for rapid drying of coated materials... 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 apparatus for rapid drying of coated materials..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for rapid drying of coated materials... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2465764