Hydraulic and earth engineering – Subterranean waste disposal – containment – or treatment – Waste barrier – containment – or monitoring
Reexamination Certificate
2000-10-20
2002-08-20
Shackelford, Heather (Department: 3673)
Hydraulic and earth engineering
Subterranean waste disposal, containment, or treatment
Waste barrier, containment, or monitoring
C405S129950, C405S129450, C405S129550, C241S023000
Reexamination Certificate
active
06435770
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions producing a synthetic cap for bulk material piles, including waste and soil, including soil erosion control, using a powder derived from recycled gypsum wallboard and a process to make the powder. Constituents for the cap include liquid and powder. These constituents are mixed to form a slurry, which is distributed over a material pile. The cover will harden to minimize water infiltration, nuisance fugitive dust, odor, and affinity to birds, flies and other insects. Inert fillers and fiber can be added to the slurry mixtures.
BACKGROUND OF THE INVENTION
Gypsum wallboard is made of a sheet of gypsum, which is covered on both sides with paper facing and paperboard backing. The wallboard is composed of approximately 93% gypsum and 7% paper, by weight. More than four million tons of gypsum waste is generated every year by wallboard manufacturing and installation and building demolition. Only a small portion of the scrap is being recycled for agricultural purpose or new wallboard; most is sent to landfills. It is very difficult to separate the paper from gypsum to recycle wallboards. Current technology produces recycled gypsum that contains about 1.75% paper, a concentration which is too great and limits the amount of recycled gypsum allowable in new drywall, since the paper content affects the product's fire rating. However, the paper content can remain for some uses such as soil stabilization.
During shipping, processing, or storage, bulk materials may concentrate in a particular area or site. Bulk materials concentrated into piles must be covered to minimize or prevent blowing dust; water damage; odor; prevent fires; or movement or erosion of material; or prevent vectors such as birds, flies, and/or other insects from feeding thereon. Typically bulk materials are covered by spreading a synthetic material such as a tarp or foam over exposed portions of the pile. For example, in power plants, piles of coal may be covered by spreading an elastomeric geomembrane thereon; the thickness and construction of the membrane depends on the length of time the pile is to remain covered and the expected climatic conditions.
United States Gypsum Company has been marketing a product called Airtrol Plaster®, which is mixed with cellulose fiber mulch and water to form a slurry and is sprayed for a landfill cover or erosion control. Airtrol Plaster® is made from industrial grade gypsum and must be mixed with cellulose fiber mulch to form a cover.
Kramer et al, describes a hardenable plastic foam cover which is formed by spraying over waste materials. Similarly, companies such as 3M Environmental Protection Products of St. Paul, Minn., Chubb Environmental Security of Exton, Pa., and Russmer of Westchester, Pa., all have developed synthetic foams which can be sprayed to function as a daily cover. The foam spray solution is expensive, typically 12 to 15 cents per square foot, substantially more expensive than soil.
Another disadvantage of the daily foam cover substitutes is that they cannot be easily formulated from recycled materials. The increasing sensitivity towards the environment by the general population has greatly increased the demand for recycled products. State and municipal environmental officials, who operate or regulate most landfills, have been especially active in encouraging use of recycled products. Among the advantages of recycling is the fact that the waste material is converted into useful products rather than taking up rapidly vanishing landfill space. Hence, such officials are making great efforts to integrate recycled materials into operations under their control, including landfill operations.
Another alternative to using earthen material as a daily cover is disclosed in U.S. Pat. Nos. 4,909,667 to DeMello and 4,927,317 to Acosta. DeMello and Acosta disclose a geotextile or sheet-like member, such as canvas and the like, which is laid over the working face of a landfill at the end of the operating day. A key disadvantage of geotextile covers is their expense which may be as high as $2.25 per square yard. In addition, geotextiles are subject to mechanical damage, such as tears, punctures, requiring replacement or repair. Moreover, these covers are difficult to apply in inclement weather.
A daily cover system and method for production of a cover system has been disclosed in U.S. Pat. No. 5,161,915 issued Nov. 10, 1992, and US Pat. No. 5,525,009 issued Jun. 11, 1996 to Hansen. The cover disclosed system primarily uses cement kiln dust or Portland cement and flyash, or Portland cement crushed stone dust as a binder, and is limited since the ingredients may be costly, inefficient, and perhaps may even be an environmental hazard, and therefore defeating the aim of the invention, i.e. to cover waste piles and prevent them from being hazard. The disclosed ingredients can be highly caustic and a potential environmental hazard.
Cement kiln dust is not widely available. In August 1999, the U.S. Environmental Protection Agency (USEPA) proposed new regulations for management of cement kiln dust, which was designated as “high-volume, low toxicity” special wastes requiring individualized treatment under the Resource Conservation and Recovery Act (RCRA). Although the proposed rule does not limit the beneficial use of cement kiln dust in a commercial landfill, the handling and transportation regulations could potentially pose difficulties for customers and haulers. In most cases when cement kiln dust is used as a binder, it may take a long time for the slurry to harden. If a mixture of Portland cement and flyash, or a mixture of Portland cement and aggregate dust is used for binding, the result may be expensive. A binder using a small concentration of Portland cement is slow to harden.
SUMMARY OF THE INVENTION
In view of the above stated difficulties for using recycled gypsum wallboard and limitations and shortcomings of sprayable covers there still exists a need in the art to develop new better performing applications for recycled gypsum wallboard and an alternative to sprayable cover which uses inexpensive, widely available, and environmentally friendly recycled materials.
More specifically, it is a purpose of this invention to provide a method of processing recycled gypsum wallboard and applications for processed recycled gypsum wallboard.
More specifically, it is a purpose of this invention to provide a method of manufacturing for sprayable cover which uses widely available recycled materials or by-products as a binder.
A further objective of this invention is to be able to provide a sprayable cover that has minimal environmental hazards.
A further objective of this invention is to be able to provide a sprayable cover that can form and harden within a short period of time.
The aforementioned objectives are achieved by a sprayable cover in accords with the present invention.
This invention provides a method for converting recycled gypsum wallboard to a useful powder and compositions for a sprayable mixture, which consists of the powder made from recycled gypsum wallboard, inert filler, and liquid.
Recycled gypsum wallboard can be very large in size. Large gypsum wallboard, including the paper facing, should be crushed into small pieces then pulverized into a powder with 90% particles passing a No. 30 sieve. The powder virtually consists of approximately 93% gypsum and 7% cellulose fiber. Depending on the end application, a portion of paper facing can be easily screened out during the crushing and pulverizing processes.
The powder is then heated to form a hemi-hydrate or anhydrate to obtain cementitious properties. Pulverized recycled gypsum is heated between 120° C. to 300° C. to obtain a hemi-hydrate, and is heated over 300° C. to obtain anhydrate. Alpha-hemyhydrate is formed when gypsum is heated in an autoclave between 120 to 200° C., and beta-hemihydrate is generated when gypsum is heated in a dry furnace between 1200C to 3000C. Alpha-hemihydrate and beta-hemihydrate have different morphologies and alpha-hemihydrate has
Advanced Material Technologies LLC
Hodgson & Russ LLP
Mitchell Katherine
Shackelford Heather
LandOfFree
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