Gas separation: processes – Solid sorption
Reexamination Certificate
2002-06-07
2003-11-11
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Solid sorption
C095S143000, C095S146000, C096S134000, C096S144000, C096S147000, C096S154000, C055S385300, C055S524000, C055SDIG005
Reexamination Certificate
active
06645271
ABSTRACT:
FIELD
The present invention relates to an adsorption element for removing contaminants from a gaseous stream, such as an air stream.
BACKGROUND
Gas adsorption articles or elements are used in many industries to remove airborne contaminants to protect people, the environment, and often, a critical manufacturing process or the products that are manufactured by the process. A specific example of an application for gas adsorption articles is the semiconductor industry where products are manufactured in an ultra-clean environment, commonly known in the industry as a “clean room”. Gas adsorption articles are also used in many non-industrial applications. For example, gas adsorption articles are often present in air movement systems in both commercial and residential buildings, for providing the inhabitants with cleaner breathing air.
Typical airborne contaminants include basic contaminants, such as ammonia, organic amines, and N-methyl-2-pyrrolidone, acidic contaminants, such as hydrogen sulfide, hydrogen chloride, or sulfur dioxide, and general organic material contaminants, often referred to as VOCs (volatile organic compounds) such as reactive monomer or unreactive solvent. Silica containing reactive and unreactive materials, such as silanes, siloxanes, silanols, and silazanes can be particularly detrimental contaminants for some applications. Additionally, may toxic industrial chemicals and chemical warfare agents must be removed from breathing air.
The dirty or contaminated air is often drawn through a granular adsorption bed assembly or a packed bed assembly. Such beds have a frame and an adsorption medium, such as activated carbon, retained within the frame. The adsorption medium adsorbs or chemically reacts with the gaseous contaminants from the airflow and allows clean air to be returned to the environment. The removal efficiency is critical in order to adequately protect the processes and the products.
The removal efficiency and capacity of the gaseous adsorption bed is dependent upon a number of factors, such as the air velocity through the adsorption bed, the depth of the bed, the type and amount of the adsorption medium being used, and the activity level and rate of adsorption of the adsorption medium. It is also important that for the efficiency to be increased or maximized, any air leaking through voids between the tightly packed adsorption bed granules and the frame should be reduced to the point of being eliminated. Examples of granular adsorption beds include those taught is U.S. Pat. No. 5,290,245 (Osendorf et al.), U.S. Pat. No. 5,964,927 (Graham et al.) and U.S. Pat. No. 6,113,674 (Graham et al.). These tightly packed adsorption beds result in a torturous path for air flowing through the bed.
However, as a result of the tightly packed beds, a significant pressure loss is incurred. Current solutions for minimizing pressure loss include decreasing air velocity through the bed by increased bed area. This can be done by an increase in bed size, forming the beds into V's, or pleating. Unfortunately, these methods do not adequately address the pressure loss issue, however, and can create an additional problem of non-uniform flow velocities exiting the bed.
Although the above identified adsorption beds are sufficient in some applications, what is needed is an alternate to a bed that can effectively remove contaminants such as acids, bases, or other organic materials, while minimizing pressure loss and providing uniform flow velocities exiting the filter.
SUMMARY OF THE INVENTION
The present invention is directed to an adsorptive element having a minimal pressure loss therethrough. The adsorptive element has a base body substrate, or matrix, onto which is applied an adsorptive coating. The body can be a honeycomb matrix or other structure having a plurality of cells defining a plurality of passages extending through the body. The adsorptive coating comprises an adsorptive media, such as carbon (usually activated carbon) or ion exchange resin, that is bound by a polymeric adhesive or resin onto the surface of the body. In another embodiment, the coating can comprise a strong oxidizing agent, such as potassium permanganate.
The adsorptive element of the present invention can be used in any variety of applications that desire the removal of chemical contaminants from a fluid (typically gaseous) stream, such as an air stream. Generally, the element can be used in any application such as lithographic processes, semiconductor processing, and photographic and thermal ablative imaging processes. Proper and efficient operation of a fuel cell also desires air (oxidant) that is free of unacceptable chemical contaminants. Other applications where the adsorptive element of the invention can be used include those where environmental air is cleansed for the benefit of those breathing the air. Often, these areas are enclosed spaces, such as residential, industrial or commercial spaces, airplane cabins, and automobile cabins. Personal devices such as respirators or self-contained breathing apparatus are also used to cleanse breathing air. Other times, it is desired to remove contaminants prior to discharging the air into the atmosphere; examples of such applications include automobile fuel system or engine induction system or other vehicle exhaust, exhaust from industrial operations, or any other operation or application where chemical contaminants can escape into the environment.
In one particular aspect, the invention is to a contaminant-adsorbing element or article comprising a body having a thickness of at least 1 centimeter comprising a plurality of passages extending therethrough in a side-by-side array. These passages have a maximum width of no more than about 5 millimeters. A coating substantially covers the passages, the coating comprising a polymeric binder and an adsorbent particulate, such as a carbon particulate. The thickness of the coating (that is, the binder and particulate) is no greater than 0.5 millimeter. The article is substantially free of incidental catalytic activity or any important catalytic activity. Incidental catalytic activity is related to catalysis of reactions not directly related to the removal of a contaminant. These absorptive structures are typically free of catalyst metals such as Pt, Au, Ag, Pd, etc., and catalyst materials used in catalytic converters.
The adsorptive media can be applied to the body or matrix as a melt, a solution or a slurry having the media dispersed therein so that the media is fully imbedded in or covered by the polymeric adhesive. Alternately, the media can be adhered to the body in a manner such that the media is adhered to the surface of the body but is not completely covered by the polymer. Various techniques for applying the adsorptive coating are disclosed.
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Carter Steven Alan
Dallas Andrew James
Ding Lefei
Hoang Brian Nghia
Joriman Jon Dennis
Donaldson & Company, Inc.
Merchant & Gould P.C.
Spitzer Robert H.
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