Title: Control of leachable mercury in mercury vapor discharge lamps
Abstract: A method and apparatus for preventing the formation of leachable mercury in mercury arc vapor discharge lamps is provided which comprises providing in the lamp structure an effective amount of a silver compound, gold compound, or combination thereof.
Patent Number: 6,853,118 Issued on 02/08/2005 to Haitko, et al.
| Inventors:
|
Haitko; Deborah Ann (Schenectady, NY);
Buddle; Stanlee Teresa (Gloversville, NY);
Dietrich; David Key (Schenectady, NY);
Foust; Donald Franklin (Scotia, NY)
|
| Assignee:
|
General Electric Company (Niskayuna, NY)
|
| Appl. No.:
|
847198 |
| Filed:
|
May 3, 2001 |
| Current U.S. Class: |
313/318.08; 252/520.3; 313/318.01; 313/490; 313/639 |
| Intern'l Class: |
H01J 017/20; H01J005/48 ; 489 |
| Field of Search: |
313/571,577,639,568,490,562,564,550,483,484,638-640,318.01,318.08,624,625,565
174/17.07,50.61,50.62
65/59.1,59.4,59.24
428/209,432,434
252/500,518.1,520.3
|
References Cited [Referenced By]
U.S. Patent Documents
| 2873510 | Feb., 1959 | Duran et al. | 228/124.
|
| 3302961 | Feb., 1967 | Franklin | 403/272.
|
| 3755065 | Aug., 1973 | Chvatal | 428/408.
|
| 3858378 | Jan., 1975 | Allen et al. | 403/30.
|
| 4319157 | Mar., 1982 | De Vrijer | 313/642.
|
| 4469980 | Sep., 1984 | Johnson | 313/25.
|
| 4559470 | Dec., 1985 | Murakami et al. | 313/487.
|
| 5229686 | Jul., 1993 | Fowler et al.
| |
| 5229687 | Jul., 1993 | Fowler et al.
| |
| 5409522 | Apr., 1995 | Durham et al. | 75/670.
|
| 5460643 | Oct., 1995 | Hasenpusch et al. | 95/134.
|
| 5599515 | Feb., 1997 | Misra et al. | 423/101.
|
| 5801483 | Sep., 1998 | Watanabe et al. | 313/485.
|
| 5821682 | Oct., 1998 | Foust et al.
| |
| 5952780 | Sep., 1999 | Forsdyke et al. | 313/565.
|
| 5972442 | Oct., 1999 | Anderson et al. | 428/34.
|
| 5986405 | Nov., 1999 | De Maagt et al. | 313/637.
|
| 6043603 | Mar., 2000 | Weinhardt | 313/566.
|
| 6224446 | May., 2001 | Dietrich et al. | 445/2.
|
| 2001/0020823 | Sep., 2001 | Dietrich et al. | 313/640.
|
| Foreign Patent Documents |
| 61240526 | Oct., 1986 | JP | .
|
| 04245162 | Sep., 1992 | JP | .
|
Primary Examiner: Patel; Nimeshkumar D.
Assistant Examiner: Colon; German
Attorney, Agent or Firm: Vo; Toan P., Patnode; Patrick K.
Claims
What is claimed is:
1. A low-pressure mercury vapor discharge lamp comprising an end cap that
is attached to a glass enveloped with a sealing composition that consists
of a silver compound, a gold compound or combination thereof.
2. A low-pressure mercury vapor discharge lamp comprising an end cap that
is attached to a glass envelope with a sealing composition that comprises
a silver compound, a gold compound or combination thereof, wherein said
silver compound comprises silver carbonate, silver halide, silver sulfide,
silver acetate, or combinations thereof.
3. The low-vapor pressure mercury vapor discharge lamp of claim 2, wherein
said silver compound, gold compound, or combination thereof is present in
a range between about 10 milligrams and about 30 milligrams per lamp.
4. The low-pressure mercury vapor discharge lamp of claim 2, wherein
elemental mercury in said lamp is substantially incapable of interacting
with ferric and cupric compounds present in said lamp to produce soluble
mercury in a presence of said silver compound, gold compound, or
combination thereof.
5. A fluorescent lamp comprising an amount of silver carbonate in a range
from about 0.1 milligram to about 30 milligrams.
6. A fluorescent lamp comprising an amount of gold compound in a range from
about 0.1 milligram to about 30 milligrams, said gold compound comprising
gold carbonate, gold halide, gold oxide, gold sulfide, gold acetate, or
combinations thereof.
7. A mercury vapor discharge lamp comprising an amount of silver carbonate
in a range between about 10 milligrams and about 30 milligrams per lamp to
substantially prevent the interaction of elemental mercury with ferric and
cupric compounds which oxidize elemental mercury to a soluble form.
8. A method for preventing the formation of leachable mercury compounds in
a mercury vapor discharge lamp, said method comprising providing a sealing
composition between an end cap and a glass envelope of said lamp, said
sealing composition comprising a silver compound, gold compound, or
combination thereof; wherein said silver compound is selected from the
group consisting of silver carbonate, silver halide, silver sulfide,
silver acetate, and combinations thereof.
9. The method of claim 8, wherein said silver compound, gold compound, or
combination thereof is present in a range from about 10 milligrams to
about 30 milligrams per lamp.
10. The method of claim 8, wherein elemental mercury in said lamp is
substantially incapable of interacting with ferric and cupric compounds
present in said lamp to produce soluble mercury in a presence of said
silver compound, gold compound, or combination thereof.
11. A method for preventing the formation of leachable mercury compounds in
a mercury vapor discharge lamp, said method comprising providing a sealing
composition between an end cap and a glass envelope of said lamp, said
sealing composition consisting of a silver compound, gold compound, or
combination thereof, wherein said silver compound comprises silver
carbonate, silver chloride, silver oxide, silver sulfide, silver acetate,
or combinations thereof.
12. A method for preventing the formation of leachable mercury compounds in
a mercury vapor discharge lamp, said method comprising providing, in a
structure of said lamp, between about 0.1 milligram and about 30
milligrams of silver carbonate.
13. A method for preventing the formation of leachable mercury compounds in
a mercury vapor discharge lamp, said method comprising providing, in a
structure of said lamp, between about 0.1 milligram and about 30
milligrams of a gold compound that comprises gold carbonate, gold halide,
gold oxide, gold sulfide, gold acetate, or combinations thereof.
14. A method for preventing the formation of leachable mercury compounds in
mercury vapor discharge lamps comprising providing an amount of silver
carbonate in a range between about 10 milligrams and about 30 milligrams
per lamp to substantially prevent the formation of ferric and cupric
compounds which oxidize elemental mercury to a soluble form.
15. A mercury vapor discharge lamp comprising a material selected from the
group consisting of silver compounds, gold compounds, and combinations
thereof; said material being encapsulated and disposed at a location
selected from the group consisting of a base of said lamp and an interior
of said lamp; wherein said silver compounds are selected from the group
consisting of silver carbonate, silver halide, silver sulfide, silver
acetate, and combinations thereof.
16. A mercury vapor discharge lamp comprising a material selected from the
group consisting of silver compounds, gold compounds, and combinations
thereof; said material being disposed at a base of said mercury vapor
discharge lamp; wherein said silver compound is selected from the group
consisting of silver carbonate, silver halide, silver sulfide, silver
acetate, and combinations thereof.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for preventing the
formation of leachable mercury in mercury arc vapor discharge lamps.
Mercury arc vapor discharge lamps, otherwise commonly known as fluorescent
lamps, are standard lighting means. The mercury arc vapor discharge lamp
consists of metallic components such as lead wires, connector pins and end
caps. The lead wires and portions of the end cap and connector pins are
surrounded by a glass enclosure. The interior of the glass enclosure is
typically coated with phosphor. Elemental mercury is added to the mercury
arc vapor discharge lamp and typically, the elemental mercury adheres to
the phosphor. In certain conditions, it has been found that when elemental
mercury comes in contact with the metal components in a lamp such as
copper and iron containing lead wires, brass pins, or other associated
metallic mount components, the elemental mercury is transformed into a
leachable form.
In order to address the growing concern that mercury from disposal of
fluorescent lamps might leach into surface and subsurface water, the
Environmental Protection Agency has established a maximum concentration
level for mercury at 0.2 milligrams of leachable mercury per liter of
extract fluid. The concentration level for mercury is generally determined
by a standard analysis known as the Toxicity Characteristic Leaching
Procedure (TCLP), a well known test procedure implemented in 1990 by the
Environmental Protection Agency.
When carrying out the TCLP test, test lamps are pulverized to form lamp
waste material similar to that which would result from lamp disposal in
land fills or other disposal locations. The ambient conditions in disposal
locations may be such as to promote formation of leachable mercury. The
TCLP test conditions themselves tend to allow for formation of leachable
mercury in amounts greater than the established limit of 0.2 milligrams
per liter.
During the disposal of the lamp, and in the TCLP test, the glass enclosure
of the lamp is broken. Elemental mercury that is contained in the lamp is
then exposed to the metal components in an aqueous environment. Elemental
mercury, when exposed to both the metal components and the aqueous
environment, is oxidized to leachable mercury. The metal components in the
lamp provide the source of oxidizable iron and oxidizable copper that
promotes the formation of leachable mercury.
Several techniques have been developed which prevent the formation of
mercury that can leach into the environment. The methods currently used
are concerned with a method of delivering a chemical agent or metal upon
disposal of a lamp or during the TCLP test. For instance, Fowler et al.
(U.S. Pat. No. 5,229,686 and U.S. Pat. No. 5,229,687) describe methods
that incorporate chemical agents in the lamp in either a glass capsule or
the basing cement. These chemical agents include various salts such as
bromide anions, chloride anions, iodide anions, iodate anions, periodate
anions, and sulfide anions, to name a few. Other chemical agents include
powders such as iron powder, copper powder, tin powder, and titanium
powder.
In U.S. Pat. No. 5,821,682, which has been assigned to the assignee of the
present invention, Foust et al. describe the addition of a mercury
antioxidant for superior TCLP test performance. Mercury antioxidants
include, for example, ascorbic acid, sodium ascorbate, and sodium
gluconate. These materials have been found to reduce or prevent the
formation of leachable mercurous and mercuric compounds resulting from the
oxidation of elemental mercury. Unfortunately, manufacturing processes
typically use a separate dispensing step to introduce the mercury
antioxidant.
Generally, any modification of the lamp components is driven by the need to
decrease the amount of leachable mercury. Methods and materials are
constantly being sought which decrease the leachable mercury values upon
performance of the TCLP extraction test.
SUMMARY OF THE INVENTION
The present invention provides a mercury vapor discharge lamp comprising an
effective amount of a silver compound, a gold compound or combination
thereof.
The present invention further provides a method for preventing the
formation of leachable mercury compounds in mercury vapor discharge lamps
comprising providing in the lamp structure an effective amount of a silver
compound, a gold compound or combination thereof.
DETAILED DESCRIPTION
The incorporation of a silver compound, a gold compound, or combination
thereof has been found to have a significant effect on preventing mercury
compounds from leaching during the TCLP test. Accordingly, the formation
and dissolution of soluble ferric and cuprous ions from the mercury vapor
arc discharge lamp components is diminished or prevented resulting in
reduction or prevention of leachable mercury compounds.
Lead wires are typically made of iron or copper and connector pins are
typically made of brass. The lead wires and connectors pins are the source
of elemental iron (Fe.sup.0) and copper (Cu.sup.0) which is oxidized in
the presence of oxygen and an aqueous environment to ferric (Fe.sup.+3)
and cuprous (Cu.sup.+1) ions. Ferric and cuprous ions can then dissolve in
aqueous solution. The presence of ferric and cuprous compounds has been
found to lead to the formation of leachable mercury.
"Leachable mercury" as used herein refers to elemental mercury (Hg.sup.0)
which has been oxidized. Oxidized mercury reacts with oxygen to form
compounds such as mercuric oxide (HgO). Once the lamp has been broken and
the elemental mercury can oxidize to leachable mercury, the leachable
mercury can be carried via groundwater, rivers and streams.
Suitable silver compounds include, for example, silver carbonate, silver
halides, silver oxide, silver sulfide, silver acetate, or combinations
thereof. Suitable gold compounds, include, for example, gold carbonate,
gold halide, gold oxide, gold sulfide, gold acetate, or combinations
thereof. Typically, silver carbonate is used in the present invention.
To prevent the spurious formation of leachable mercury upon disposal of
mercury vapor discharge lamps and to improve the reliability of the TCLP
test, an effective amount of a silver compound, gold compound, or
combination thereof is incorporated in the lamp structure, for example
within the glass envelope exterior to the plasma discharge, in an end-cap,
or in the base of the lamp. An effective amount of the silver compound,
gold compound, or combination thereof is that amount which will
substantially prevent the interaction of elemental mercury with ferric and
cuprous compounds that can oxidize elemental mercury to a soluble form. In
general, an effective amount of the silver compound, gold compound, or
combination thereof will be enough for the TCLP test results to show the
presence of less than about 0.2 parts per million of leachable mercury per
lamp. Typically, the silver compound, gold compound, or combination
thereof is present in a range between about 0.1 milligrams and about 10
grams per lamp, and more typically, in a range between about 10 milligrams
and about 30 milligrams per lamp.
The silver compound, gold compound, or combination thereof is typically
incorporated in the basing cement of the lamp that holds the aluminum cap
to the leaded glass portion of the end of the lamp. The basing cement
generally comprises about 80 weight % marble flour (limestone-CaO), and
the balance shellac a phenolic resin binder, a solvent for blending, and a
dye used to color the cement. The cement is dispensed through a feeder
into the base and heated to cure once assembled with the lamp. The curing
drives off the solvent and solidifies the cement. The silver compound,
gold compound, or combination thereof is blended with the cement
components and incorporated into a lamp manually or by automated
manufacturing equipment. The silver compound, gold compound, or
combination thereof is released only when the lamp is destroyed or crushed
in preparation for TCLP testing. In this method, the silver compound, gold
compound, or combination thereof is always exterior to the positive column
of the lamp. The positive column is a typically under vacuum and is a
portion of the lamp that includes the interior of the stem press (inner
leads and cathode) which is filled with phosphor and inert gases that fill
the lamp. Inert gases that fill the lamp typically include argon and
krypton. By incorporating the silver carbonate, gold carbonate, or
combination thereof within the basing cement of the end cap, no separate
dispensing step to introduce the silver compound, gold compound, or
combination thereof is necessary.
The silver compound, gold compound, or combination thereof can also be
formulated into a thermally curable adhesive or binding composition which
is soluble in acidic aqueous solutions. Such compositions generally
include an inert filler material, a binder such a polyvinymethacrylate,
and a processing solvent such as denatured alcohol. The alcohol will
evaporate and the composition will cure when the basing cement is cured.
These ingredients are similar to the usual components of basing cements
used to secure the glass envelope to the aluminum base or end cap. Gums
and gelatins have also been used as such adhesives and binders. The nature
of the gums and gelatins is that they adhere to surfaces when heated. The
composition containing the antioxidant material can be placed on the inner
surface of the aluminum end cap as a ring or discrete button. When the
lamp is crushed and exposed to an aqueous environment or placed in the
TCLP solution, the aqueous soluble binder allows the silver compound, gold
compound, or combination thereof to be released quickly.
Typical fillers include marble flour (calcium oxide). The binder material
can be shellac, rosin synthetic resins such as phenolic resin. Processing
solvents are generally lower alcohols such as ethyl, propyl, butyl, or
amyl alcohol.
The silver compound, gold compound, or combination thereof can also be
incorporated in the lamp by encapsulation of the material in a glass
capsule that can be placed either in the base of the lamp between the
aluminum cap and flare of leaded glass, or placed within the positive
column of the lamp. Since the silver compound, gold compound, or
combination thereof is enclosed in a glass capsule, it could be present in
the inside of the positive column of the lamp without affecting lamp
function.
The invention is illustrated by testing of mercury vapor arc discharge
lamps via the TCLP test in which silver carbonate was added to the lamp
components. These examples are to be regarded as non-limiting.
All TCLP test data was obtained by the test procedure prescribed on pages
26987-26998, volume 55, number 126 of Jun. 29, 1990 issue of the Federal
Register.
Briefly, lamps being tested with the TCLP test were pulverized into
particulate form having the prescribed particle size which is capable of
passing through a 3/8 inch sieve. The test material was then extracted
with a sodium acetate-acetic acid buffer at a pH of about 4.93.
Varying amounts of silver carbonate were added to the TCLP test to
determine the effectiveness of the silver salt on reducing the amount of
leachable mercury formed during the TCLP test. The data in Table 1 shows
that levels as low as 10 milligrams of silver carbonate per lamp reduced
leachable mercury to below the regulatory limit of 0.2 parts per million
per lamp when either a F32T8SCSP35 lamp or F40T12 Cool White WattMiser
lamp (both available from GE Lighting) was mercury dosed at 20 milligrams
per lamp. One of the most important advantages of using silver carbonate
is the fact that the milligram quantities of silver carbonate required can
be easily incorporated within the basing cement of the end cap. No
separate steps were required to add silver carbonate to the basing cement.
TCLP test results using silver carbonate within the basing cement are
shown in Table 1.
Undosed F32T8SCSP35 lamps (hereinafter referred to as "F32") and F40T12
(hereinafter referred to as "F40") Cool White WattMiser lamps were used
for screening the additives. Technical grade and 99% silver carbonate
(Ag.sub.2 CO.sub.3) were purchased from Aldrich Chemicals and were not
purified prior to use. Standard TCLP protocol was followed with
modifications for lamp testing made according to the Scientific
Applications International Laboratory's study of fluorescent lamp/TCLP
testing commissioned by the Environmental Protection Agency as described
in "Analytical Results of Mercury in Fluorescent Lamps," by SAIC, EPA
Contract No. 68-WO-0027, May 15, 1992. Results of various amounts of
silver carbonate (Ag.sub.2 CO.sub.3) added to the 20 milligram mercury
(Hg) dosed F40 and F32 lamps can be seen in Table 1.
TABLE 1
Amount Ag.sub.2 CO.sub.3 Leachable Hg for Leachable Hg for F32
Sample # added (mg) F40 (ppb) (ppb)
1 50 <25
2 10 60
3 5 70
4 50 <25
5 20 <25
6 10 33
7 5 40
8 0 441
9 0 512
As seen in Table 1, 5 milligrams of silver carbonate reduced the amount of
leachable mercury in the F40 and F32 lamps by more than one-sixth and
one-twelfth respectively compared to when silver carbonate was not added
to the lamps. In addition, 50 milligrams of silver carbonate effectively
reduced the amount of leachable mercury for both lamps to less than 25
parts per billion (ppb) per lamp.
While embodiments have been shown and described, various modifications and
substitutions may be made thereto without departing from the spirit and
the scope of the invention. Accordingly, it is to be understood that the
present invention has been described by way of illustration and not
limitation.
*
