Amalgam separation

Details Amalgam separation Amalgam separation

2000-07-13

2002-06-25

Hopkins, Robert A. (Department: 1724)

Gas separation: processes

Deflecting

Centrifugal force

C055S349000, C055S421000, C055S431000, C055S459100, C055S467000, C433S092000

Reexamination Certificate

active

06409803

ABSTRACT:

BACKGROUND AND SUMMARY OF THE INVENTION
Environmental awareness and protection is becoming an ever more important topic in today's industrial society. While the impact of large quantity environmental polluters has long been realized and regulated, the regulation of smaller scale contributors is becoming increasingly fundamental. The dental arena is no exception to this rule, and is currently being targeted for its hazardous waste production.
A common dental procedure involves the reconstruction of decayed tooth cavities with amalgam, a metal alloy typically comprising approximately 50% mercury and 50% silver, copper, and nickel, collectively. During these routine restoration procedures, as well as amalgam restoration removals, amalgam particles become entrained in dental clinic waste streams. When introduced to the environment, the high concentration of mercury in the amalgam chemically reacts with living bacteria. Products of this methlyization reaction include monomethyl mercury and dimethyl mercury, which are both powerful neurotoxins. These toxic materials can be introduced to the ground water supply and eventually accumulate in the food chain.
As such, the amalgam particles must be removed from the waste streams and disposed of using appropriate hazardous waste procedures. While the United States, as a whole, does not currently regulate the release of amalgam from dental clinics, methods of management are being actively discussed. Many countries, however, have regulatory procedures in place; Germany for example, requires that all dental offices remove 95% of all amalgam particles from their waste.
In doing so, two separation techniques are currently being utilized for the capture of fugitive amalgam. Centrifuge separators and large sedimentation separators are the common filtration techniques in use. These are typically cumbersome, expensive, and maintenance intensive devices that are placed near the end of the waste system, after the refuse from all operating rooms combine into a common header. Another system for multiple operatories is shown in U.S. Pat. No. 5,017,135 (incorporated by reference herein).
According to the invention it is preferred to provide a device and method that efficiently accomplish the separation of amalgam, and related sludge, from the waste stream discharged from each individual operating room. Thus, the separator and separation procedure will satisfy the environment concerns related to the release of amalgam while protecting waste system piping from corrosion and particle build-up and ultimately from disposal concerns. The constraints imposed on this device require a small, inexpensive, and operator friendly device that cannot be accomplished with currently used separation techniques. The equipment can be made of any conventional suitable materials that are capable of withstanding the action of the waste stream flows.
The design specifications for amalgam separation according to the invention include separation efficiency, pressure loss, size, and energy constraints needed for an entirely effective device. Additionally, the operator interface and shipping and handling requirements related to separator design are taken into account, as well as compliance with all applicable laws and codes. These specifications are outlined in Table 1.
TABLE 1
Design Objectives
Separation
95% of 5 micron and larger particles
Air Flow
Less than 3.175 mmHg @ 0.21 m
3
/min
Head Loss
Size
Fit conveniently under chair toe or in sink cabinet
Energy
No outside source, passive operation
Requirements
Installation
No special tools
Ease
Splice into 5/8″ hose between solids Separator and j-box
Shipping/
Self storing caps
Handling
Water-tight, courier shippable
Operator
No tool switchover
interface
“Full” indicator
Exchange for clean, empty replacement
Safety
Complies with OSHA Bloodborne Pathogen Standards
Environmental
Exchange with EPA Certified contractor
Hygiene
A primary purpose of the separation device and procedure of the invention is to capture hazardous waste material and provide for transporting the waste to an appropriate contractor, using a reusable or recyclable component that meets the standards established by OSHA, EPA, FDA, UPS, and Fed-Ex, and that can be shipped via parcel mail.
According to one aspect of the present invention there is provided a method of separating particles from at least one dental operatory effluent line, comprising: (a) Subjecting fluid including gas, liquid, and entrained particles, from a dental operatory to centrifugal separation so that at least the majority of the mass of the particles and liquid are discharged at a first location and the majority of the gas at a second location so that substantially effective separation of the particles from the gas occurs. (b) Filtering the liquid discharged at the first location to collect the majority of the particles therein. And, (c) disposing of the collected particles in an environmentally sound manner.
The method may further comprise (d) combining the filtered water from (b) with a gas flow from the second location. In a preferred embodiment (d) is practiced by causing the liquid to collect in a pool; passing a conduit containing the gas from the second location through the pool, and causing the liquid to selectively penetrate the conduit so as to be entrained by the gas. In a preferred embodiment, (a)-(d) are practiced by subjecting the fluid from the dental operatory to the force of a dental vacuum pump, which provides the motive force for effecting centrifugal separation and for passing the gas through the conduit.
According to the invention (a) may be practiced using a dental vacuum pump (already conventionally provided in association with a dental operatory) to provide the motive force for separation (acting with gravity to effect separation). For example (a) may be practiced using gravity and the dental vacuum pump as substantially the only motive forces for effecting separation.
The invention can be cost-effective and not only practical in a situation where (a)-(c) are practiced using a fluid stream solely from a single dental operatory. Also preferably (a)-(c) are practiced so as to separate and dispose of at least about 95% of the particles in the fluid having a dimension of 4 microns or more, and typically (a)-(c) are practiced with an air flow head loss of less than 0.125 inches mercy at about 0.21 cubic meters/min.
In the preferred embodiment of the invention (a) is practiced by subjecting the fluid to a plurality of parallel centrifugal separation operations, and combining the filtered liquid and second location gas from the plurality of separation operations.
According to another aspect of the present invention there is provided a particle-containing fluid handling system, comprising: A housing having a particle-containing fluid inlet, and at least one outlet. A plurality of parallel centrifugal separators mounted in the housing each including a tangential inlet, a bottom outlet, and a top outlet. A common discharge conduit connected to the top outlets and the at least one housing outlet. The housing fluid inlet connected to the separator tangential inlets. And, a particle filter mounted in the housing below the separator outlets.
In a preferred embodiment of the invention, the at least one housing outlet is connected to a dental vacuum pump and the housing inlet is connected to a single dental operatory. The system preferably further comprises a liquid collecting tray disposed below the filter which collects and directs liquid that has passed through the filter. For example the at least one housing outlet consists essentially of a single housing outlet; and the liquid collecting tray causes a pool of liquid to form adjacent to where the conduit connects to or forms the housing outlet, and the system further comprises an opening in a bottom portion of the conduit at the pool which allows liquid from the pool to pass through the opening into the conduit to be entrained by gas flowing in the conduit.
The particle filter may comprise a polypropylene mesh filte

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