Compositions: ceramic – Ceramic compositions – Composed of waste material
Reexamination Certificate
1998-07-29
2001-03-20
Marcheschi, Michael (Department: 1755)
Compositions: ceramic
Ceramic compositions
Composed of waste material
C501S109000, C501S111000, C501S119000, C501S153000, C501S108000, C106S690000, C106S691000, C588S010000, C588S012000, C588S252000, C588S256000, C588S901000
Reexamination Certificate
active
06204214
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pumpable/injectable ceramic, and more particularly this invention relates to a ceramic composition that maintains low viscosity for extended periods of time to allow the composition to be pumped or injected into hard to reach geologic or manmade locations.
2. Background of the Invention
Disposal of hazardous waste, low-level radioactive waste or benign waste continues to present problems. Landfill space is becoming more scarce so that only nonrecyclable material or nonbiodegradable material is often considered the only candidates for land filling.
When hazardous material is land filled, care must be taken to prevent destabilization of the material, so that leaching will not occur.
Aside from land filling, efforts have been made to combine to-be-disposed-of-material with cement so as to form solid monoliths or waste forms for burial or for use as structural products. For example, U.S. Pat. No. 4,432,666 to Frey et al., discloses using cement and other water repellant binders to dispose of waste thought to be damaging to the environment. However, cement is unstable in many situations, for example when attempts are made to encapsulate halogenated materials.
U.S. Pat. No. 3,093,593 to Arrance discloses a method for vitrifying silicate materials to encapsulate radioactive waste. However, temperatures of up to 1,400° C. are required to produce final waste forms.
In U.S. Pat. No. 5,645,518, awarded to the instant Assignee, a method to stabilize low-level mixed wastes, such as radioactive medical wastes and other such materials, is provided, wherein phosphate ceramics physically and chemically stabilize the waste at ambient temperatures. However, in such endeavors, final waste forms rapidly set. This rapid-setting feature causes various degrees of unworkability to the process, particularly in situations where low viscosity and long operational times are required. Such situations include where the material is to be blown, poured or injected into deep wells or crevices, in-situ stabilization of buried wastes, remediation at nuclear-accident and waste spillage sites, and pumpable refractory applications.
In addition to the drawbacks of the above-mentioned processes, commercially supplied materials for use as components (particularly the oxides) of the above processes are in forms adverse to formulating flowable mixtures. As a result, exothermic reactions become uncontrollable, leading to thicker slurries, with the final product lacking homogeneity. Also, the resulting rapid setting time of the ceramic does not provide adequate working time.
A need exists in the art for a formulation and a waste encapsulation process to accommodate stabilization of a myriad of waste materials in a myriad of deposition scenarios. The formulation and process should provide waste liquors having protracted, workable consistencies or viscosities to accommodate currently available pump- injection-, or spray application-equipment. The process should also provide a protocol for selecting and preparing components of the formulation so as to tailor the formulation for situations requiring varying degrees of viscosity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a formulation comprising waste and waste-encapsulation material that overcomes many of the disadvantages of the prior art.
It is another object of the present invention to provide a method for using waste as a bulk-component in pumpable hardening agents. A feature of the invention is the use of additives to slow the reaction between components of the hardening agents. An advantage of the invention is the extension of time of workability. Another advantage is the employ of heretofore unusable waste.
Still another object of the present invention is to provide a means for converting commonly available oxides into a component in pumpable hardening agents. A feature of the invention is calcining the oxides and then mixing the calcined oxides with coating agents. An advantage of the invention is the reduction in reaction rate of the calcined oxide in relation to the other components of the hardening agents, leading to extended workability time of the hardening agent prior to curing.
Yet another object of the present invention is to provide selection criteria for oxides to be used in the production of pumpable ceramic hardening formulations. A feature of the invention is the use of solubility, porosity and morphology characteristics of the oxides to differentiate acceptable oxides from unacceptable oxides. An advantage of the invention is that the characteristics are determinable prior to mixing or forming of waste forms. Another advantage is that oxides having the desired characteristics can be produced via calcination.
Briefly, the invention provides pumpable ceramic composition comprising an inorganic oxide, potassium phosphate, and an oxide coating material.
Also provided is a pumpable ceramic-based waste formulation comprising 7 to 14 weight percent MgO, 25 to 40 weight percent KH
2
PO
4
, 15 to 50 weight percent ash, 1 to 4 weight percent boric acid, 0.5 to 2 weight percent lignosulfonate, and 15 to 25 weight percent water.
The invention also provides a method for preparing pumpable ceramic-based waste forms comprising selecting inorganic oxides based on solubility, surface area and morphology criteria; mixing the selected oxides with phosphate solution and waste to form a first mixture; combining an additive to the first mixture to create a second mixture; adding water to the second mixture to create a reactive mixture; homogenizing the reactive mixture; and allowing the reactive mixture to cure.
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Jeong Seung-Young
Perry Lamar
Singh Dileep
Wagh Arun S.
Cherskov & Flaynik
Marcheschi Michael
University of Chicago
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