Plastic and nonmetallic article shaping or treating: processes – Formation of solid particulate material directly from molten... – Coated particles
Reexamination Certificate
2000-08-03
2002-07-09
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Formation of solid particulate material directly from molten...
Coated particles
C264S109000, C588S256000
Reexamination Certificate
active
06416691
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a synthetic aggregate and a process for producing the synthetic aggregate. More particularly, the process of the invention is directed at converting a waste material into the synthetic aggregate utilizing a molten sulphur binder. The invention also relates to a process for immobilizing environmental contaminants and converting them into a physical state wherein they are non-hazardous to the environment.
BACKGROUND OF INVENTION
Numerous waste products or materials are generated by a variety of industries. These waste products include contaminated sand and soil, metallurgical slag, ash, saw dust, wood shavings and various other mineral and organic by-products generated by industries such as the oil and gas, petrochemical, mining, pulp and paper, timber and construction industries. Costly solutions are often required to address the treatment and disposal problems presented by such waste materials in order to ensure that such treatment or disposal occurs in a safe and effective manner.
Several options currently exist for dealing with these types of waste materials. First, the waste materials may be disposed of in sanitary landfills. However, this solution tends to be costly and may be environmentally undesirable due to the potential for the leaching of the wastes into the surrounding soil and groundwater. Second, these wastes may undergo washing or some form of chemical treatment aimed at de-contamination of the waste. This solution also tends to be costly and may result in the production of some amount of contaminated by-products, such as waste water, which similarly requires treatment prior to disposal. As well, the decontaminated waste, such as decontaminated soil waste, may have no use and therefore must typically be stockpiled in some fashion, taking up land space.
Finally, the waste material may be encapsulated using a Portland cement binder in order to produce a concrete-like mass. However, the use of Portland cement as a binder tends to be costly due to the materials used and the necessary processing requirements for Portland cement. In addition, the use of Portland cement may present difficulties when actually using the encapsulated materials for construction due to the relatively short time which is typically available for the delivery of the concrete to a potential construction site prior to the commencement of the setting of the concrete. In addition, environmental concerns continue to be raised with respect to the use of contaminated waste materials in Portland cement concrete when being used for construction purposes. Thus, such concrete is usually restricted by environmental regulations to industrial construction sites.
The treatment of sulphur-rich petroleum oil and natural gas products, as well as some ores, produces a voluminous amount of sulphur as a by-product. While there are available uses for sulphur, such as the manufacture of fertilizers, there has tended to be a substantial oversupply of sulphur resulting from the ever increasing desulphurization of primary products such as petroleum oil, natural gas and ores. As a result of environmental concerns due to potential contamination by sulphur stock-piled on site, safe, effective and cost efficient solutions are similarly required for the treatment or disposal of such sulphur.
One use of this sulphur has been the development of sulphur cements and concretes. Sulphur concretes are materials in which aggregate is bound together by elemental sulphur. The concretes are typically cast in the molten state and bonding occurs upon cooling of the molten mass as the sulphur crystallizes. It has been found that on solidifying from the molten state that elemental sulphur tends to be a relatively good binder for conventional aggregates such as sand, gravel and stone. The physical properties of the elemental sulphur have an effect upon the properties of the resulting sulphur concrete. Generally speaking, these properties tend to be superior to the properties found in Portland cement concrete. For instance, sulphur concrete typically displays rapid strength development, high strength (tensile, compressive, flexural and fatigue), low permeability, low thermal conductivity, low electrical conductivity and high corrosion and wear resistance. Further, these properties may be modified and improved by the inclusion of various modifiers or plasticizers in the sulphur cement or concrete to produce what is referred to as modified sulphur cements and concretes.
For instance, U. S. Pat. No. 4,134,775 issued Jan. 16, 1979 to Schwoegler describes the production of shaped articles from a dry blend composition containing “sulphur and a particulate solid additive inorganic material.” The dry blend is heated to fuse the sulphur and then formed into the desired shape by extrusion or pelletization. The purpose of the Patent is produce a dry blend that does not settle or stratify during shipping and storage, thereby obviating the need for re-mixing of the blend when required to be used by the consumer. The dry blend maintains its uniformity until use by the consumer. U. S. Pat. No. 5,004,799 issued Apr. 2, 1991 to Kohls et. al. also describes the formation of modified sulphur concrete into discrete self-sustaining pellets which can be shipped and stored for indefinite periods and re-melted to yield usable concrete.
The purpose of these Patents is to render the sulphur or modified sulphur concrete more amenable to transport and storage. The Patents do not deal with the treatment or disposal of waste materials nor do they deal with the production of a synthetic aggregate from the compositions. U. S. Pat. No. 5,569,153 issued Oct. 29, 1996 to Mallow et. al. does describe a method of immobilizing toxic waste material by forming concrete shapes. However, the process and the resulting concrete shape require the use of hydraulic or Portland cement.
Specifically, a synthetic aggregate is first created from a pozzolana, a calcium hydroxide containing material, hydrothermal cement reactant, hydraulic cement and the toxic waste material. The waste material must be admixed with a liquid and used as a waste slurry in the mixture or sufficient water must be added to provide a moldable consistency of the mixture. The mixture is permitted to cure and is then formed into the aggregate by any typical grinding technique. The synthetic aggregate is then mixed with a modified sulphur cement, a pozzolana and sand to form a concrete product. As a result, the synthetic aggregate and process of this Patent tend to be costly and involve other disadvantageous features as discussed above due at least in part to the use of hydraulic cement therein.
U. S. Pat. No. 4,428,700 issued Jan. 31, 1984 to Lennemann describes the use of a modified sulphur cement or concrete as a barrier or backfill material for the containment of waste materials. In particular, a container of waste material, which is placed within an excavation, is surrounded by modified sulphur cement or concrete which has been placed in the molten state into the excavation around the container and then allowed to cool or harden. The Patent does not discuss or deal with the formation of a composition comprising the sulphur cement and the waste material, nor does it deal with the formation of a synthetic aggregate therefrom.
Therefore, there remains a need in the industry for a process for treating or otherwise dealing with waste materials in a relatively cost effective and environmentally safe manner as compared to conventional processes. In addition, the process preferably permits the utilization of sulphur which is presently produced in an abundant supply by various industrial processes. More particularly, there remains a need in the industry for a process for converting a waste material into a synthetic aggregate and a need for a synthetic aggregate so produced which man be used in the construction and other industries. Further, the process for converting the waste material into the synthetic aggregate preferably utilizes sulphur as a binder. Finally, there is
Kuharchuk Terrence N.
Rodman & Rodman
Theisen Mary Lynn
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