Drying and gas or vapor contact with solids – Process – Diverse types of drying operations
Reexamination Certificate
2000-05-03
2002-10-29
Esquivel, Denise L. (Department: 3744)
Drying and gas or vapor contact with solids
Process
Diverse types of drying operations
C034S444000, C034S486000, C034S488000
Reexamination Certificate
active
06470597
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to processes for dewatering and/or drying a variety of materials. More particularly, the present invention is concerned with dewatering and/or drying of various material using oscillatory flow-reversing gaseous media.
BACKGROUND OF THE INVENTION
Pulse combustion technology is a known and viable commercial method of enhancing heat and mass transfer in thermal processes. Commercial applications include industrial and home heating systems, boilers, coal gassification, spray drying, and hazardous waste incineration. For example, the following U.S. Patents disclose several industrial applications of pulse combustion: U.S. Pat. No. 5,059,404, issued Oct. 22, 1991 to Mansour et al.; U.S. Pat. No. 5,133,297, issued Jul. 28, 1992 to Mansour; U.S. Pat. No. 5,197,399, issued Mar. 30, 1993 to Mansour; U.S. Pat. No. 5,205,728, issued Apr. 27, 1993 to Mansour; U.S. Pat. No. 5,211,704, issued May 18, 1993 to Mansour; U.S. Pat. No. 5,255,634, issued Oct. 26, 1993 to Mansour; U.S. Pat. No. 5,306,481, issued Apr. 26, 1994 to Mansour et al.; U.S. Pat. No. 5,353,721, issued Oct. 11, 1994 to Mansour et al.; and U.S. Pat. No. 5,366,371, issued Nov. 22, 1994 to Mansour et al., the disclosures of which patents are incorporated by reference herein for the purpose of describing pulse combustion. An article entitled “Pulse Combustion: Impinging Jet Heat Transfer Enhancement” by P. A. Eibeck et al, and published in
Combustion Science and Technology,
1993, Vol. 94, pp. 147-165, describes a method of convective heat transfer enhancement, involving the use of pulse combustor to generate a transient jet that impinges on a flat plate. The article reports enhancements in convective heat transfer of a factor of up to 2.5 compared to a steady-flow impingement.
It is believed that the oscillatory flow-reversing impingement can also provide significant increase in heat and mass transfer in a variety of dewatering and/or drying processes. In particular, it is believed that the oscillatory flow-reversing impingement can provide significant benefits with respect to increasing machine rates in processes using moving conveyer belts for supporting the material being dewatered or dried. In addition, it is believed that the oscillatory flow-reversing impingement may enable one to achieve a substantially uniform drying of the differential-density materials or materials having a non-uniform thickness. It is now also believed that the oscillatory flow-reversing impingement may be successfully applied to dewatering and/or drying of materials, alone or in combination with other water-removing processes, such as through-air drying, steady-flow impingement drying, infra red drying, microwave drying, and drying-cylinder drying where applicable.
Examples of the materials that could be subjected to the impingement flow-reversing drying/dewatering in accordance with the present invention include, without limitation: papers, textiles, plastics, agricultural and food products, biotechnology products, pharmaceutical products, and building materials. The suitable materials may be in either continuous form (for example: plastic, webs), or discontinuous form (for example: sand, granular materials, pellets).
Accordingly, the present invention provides a process and an apparatus for removing water or other liquids from a variety of materials, using the oscillatory flow-reversing impingement gas. The present invention also provides an apparatus comprising a gas-distributing system allowing one to effectively control the distribution of the oscillatory flow-reversing gaseous media (such as air or gas) throughout the surface of the material being dewatered or dried. The present invention provide a gas-distributing system that creates a controlled application (for example, a substantially uniform application) of the oscillatory flow-reversing air or gas onto the material being dewatered or dried.
SUMMARY OF THE INVENTION
The present invention provides a novel process and an apparatus for removing water or other liquids from a variety of materials, such as, for example, papers, textiles, plastics, agricultural, biotechnology, food products, pharmaceutical products, and building materials, by using oscillatory flow-reversing air or gas as an impinging medium. The material to be dewatered may have a starting moisture content in a broad range, from about 1% to about 99%.
In its process aspect, the present invention comprises the following steps: providing a material to be dewatered or dried; providing an oscillatory flow-reversing impingement gaseous media (gas or air, or any combination thereof) having a predetermined frequency; providing a gas-distributing system terminating with at least one discharge outlet and designed to deliver the oscillatory flow-reversing impingement gaseous media onto a predetermined portion of the material to be dewatered; and impinging the oscillatory flow-reversing gaseous media onto the material through the gas-distributing system, thereby removing moisture from the material. The oscillatory flow-reversing gaseous media may beneficially be impinged onto the material to be dewatered or dried in a predetermined pattern defining an impingement area of the material.
A water-removing apparatus of the present invention has a machine direction and a cross-machine direction perpendicular to the machine direction. The apparatus of the present invention comprises: a support designed to receive thereon a material to be dewatered or dried and to carry it in the machine direction; at least one pulse generator designed to produce oscillatory flow-reversing air or gas; and at least one gas-distributing system in fluid communication with the pulse generator for delivering the oscillatory flow-reversing air or gas to a predetermined portion of the material to be dewatered or dried. The gas-distributing system terminates with at least one discharge outlet juxtaposed with the support (or with the material when the material is disposed on the support). The support and the at least one discharge outlet form an impingement region therebetween. The impingement region is defined by an impingement distance “Z” formed between the at least one discharge outlet and the support. In the embodiments of the apparatus comprising a plurality of discharge outlets, the discharge outlets are disposed such as to form a predetermined pattern defining an impingement area “E.” The oscillatory flow-reversing gas may be impinged onto the material to provide a substantially even distribution of the gas throughout the impingement area. Alternatively, the oscillatory gas may be impinged onto the material to provide an uneven distribution of the gas throughout the impingement area, thereby allowing control of moisture profiles throughout the surface of the material to be dewatered or dried.
According to the present invention, the pulse generator is a device which is designed to produce oscillatory flow-reversing air or gas having a cyclical velocity/momentum component and a mean velocity/momentum component. A cyclical pressure generated by the pulse generator is converted to a cyclical movement/velocity of large amplitude, comprising negative cycles alternating with positive cycles, the positive cycles having greater momentum and cyclical velocity relative to the negative cycles.
In one embodiment, the pulse generator comprises a pulse combustor, generally comprising a combustion chamber, an air inlet, a fuel inlet, and a resonance tube. The tube operates as a resonator generating standing acoustic waves. The resonance tube is in further fluid communication with a gas-distributing system. As used herein, the term “gas-distributing system” defines a combination of tubes, tailpipes, blow boxes, etc., designed to provide an enclosed path for the oscillatory flow-reversing air or gas produced by the pulse generator, and to deliver the oscillatory flow-reversing air or gas to a pre-determined impingement region (defined herein above), where the oscillatory flow-reversing air or gas is impinged onto the materia
Esquivel Denise L.
Institute of Paper Science and Technology, Inc.
Jones Melvin
Vitenberg Vladimir
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