United States Office of Air Quality EPA-453/R-94-018
Environmental Protection Planning and Standards February 1994
Agency Research Triangle Park NC 27711
Air
EVALUATION OF MERCURY
EMISSIONS FROM FLUORESCENT
LAMP CRUSHING
control
technology center
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EPA-453/R-94-018
EVALUATION OF MERCURY
EMISSIONS FROM FLUORESCENT
LAMP CRUSHING
CONTROL TECHNOLOGY CENTER
Sponsored by
Emission Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Air and Energy Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
February 1994
U.S. i- ' . ,-'• ;••>-,u-, Agency
Regi:o , -,•-)
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EPA-453/R-94-018
February 1994
EVALUATION OF MERCURY
EMISSIONS FROM FLUORESCENT
LAMP CRUSHING
Prepared by
William Battye
Una McGeough
Calvin Overcash
EC/R Incorporated
3101 Petty Road, Suite 404
Durham, NC 27707
EPA Contract No. 68-D1-0119
Work Assignment No. 1/026
Project Manager
Robert J. Blaszczak
Emission Standards Division
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Prepared for
Control Technology Center
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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DISCLAIMER
This report has been reviewed by the Control Technology
Center (CTC) established by the Office of Research and
Development (ORD) and the Office of Air Quality Planning and
Standards (OAQPS) of the U.S. Environmental Protection Agency
(EPA) , and has been approved for publication. Approval does riot
signify that the comments necessarily reflect the views and
policies of the EPA, nor does mention of trade names,
organization names, or commercial products constitute endorsement
or recommendation for use.
11
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PREFACE
This project was funded by EPA's Control Technology Center
(CTC) and prepared by EC/R Incorporated. The CTC was established
by EPA's Office of Research and Development (ORD) and Office of
Air Quality Planning and Standards (OAQPS) to provide technical
assistance to State and local air pollution control agencies.
Several levels of assistance are provided by the CTC. First, a
CTC HOTLINE is available to provide telephone assistance on
matters relating to air pollution control technologies. Second,
more in-depth engineering assistance is provided when
appropriate. Third, the CTC can provide technical guidance by
designing technical guidance documents, developing personal
computer software, and presenting workshops on technology
matters. The CTC also serves as the focal point for the Federal
Small Business Assistance Program, maintains the Reasonably
Available Control Technology/Best Available Control
Technology/Lowest Achievable Emission Rate (RACT/BACT/LAER)
Clearinghouse, and provides access to the Global Greenhouse Gases
Technology Transfer Center. Information concerning all CTC
products and services can be accessed through the CTC Bulletin
Board System (BBS) which is part of the OAQPS Technology Transfer
Network (TTN).
This report is the result of a request for technical
assistance from the Florida Department of Environmental
Protection. Florida was concerned about potential mercury
emissions and control options for a proposed facility that would
crush fluorescent lamps for recycling. This report presents an
evaluation of mercury emissions from the crushing of fluorescent
light bulbs. Background information on mercury-containing
fluorescent lamps and their disposal is also presented. _These
light bulbs are crushed as the first step in recovery of mercury,
or disposal of the bulbs in a landfill or incinerator. Three
iii
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different crushing systems are described in detail, and
variations on these systems are also discussed. The report
describes the air pollution controls on each system, and
emissions of mercury from the crushing process are estimated.
This information provides the basis for evaluating the potential
for mercury emissions from the crushing of fluorescent light
bulbs, and the efficacy of available air pollution controls in
limiting these emissions.
IV
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TABLE OF CONTENTS
Section Page
PREFACE iii
1.0 INTRODUCTION 1
1. 1 PROJECT GOAL 1
1.2 OVERVIEW OF DOCUMENT 1
2.0 BACKGROUND INFORMATION ON FLUORESCENT LAMPS 2
2. 1 LAMP USAGE 2
2.2 DESCRIPTION OF FLUORESCENT LAMPS 2
2.3 DISPOSAL OF LAMPS 4
2.4 MERCURY_EMISSIONS 7
3.0 LAMP CRUSHING PROCESSES 8
3.1 BASIC CRUSHING SYSTEM 9
3.1.1 Crusher Design 9
3.1.2 Air Pollution Controls 9
3.1.3 Emission Points and Estimates 10
3.2 MRS CRUSHING SYSTEM 12
3.2.1 Crusher Design 12
3.2.2 Air Pollution Controls 13
3.2.3 Emission Points and Estimates 15
3.3 MERCURY TECHNOLOGIES CRUSHING SYSTEM 16
3.3.1 Crusher Design 16
3.3.2 Air Pollution Controls 17
3.3.3 Emission Points and Estimates 17
3.4 OTHER VARIATIONS 18
3.4.1 Transfer Operations 19
3.4.2 Removal of Endcaps 19
3.4.3 MRT AB Mercury Recovery Systems 20
4.0 MERCURY RECOVERY 20
5.0 DISCUSSION AND CONCLUSIONS 21
6.0 REFERENCES 24
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LIST OF TABLES
Table Page
1. Elemental Analysis of Used Fluorescent Lamp Powder. ... 3
2. Mercury Content of Used Fluorescent Lamps 5
3. Mercury Content of New Fluorescent Lamps 6
4. Airborne Mercury Levels Associated with Fluorescent
Lamp Compaction Unit 11
5. Comparison of Calculated and Measured Emissions from
Different Crushing Systems 23
VI
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1.0 INTRODUCTION
1.1 PROJECT GOAL
This project is sponsored by the Control Technology Center
(CTC) of the U.S. Environmental Protection Agency (EPA), Research
Triangle Park, North Carolina. The purpose of this project is to
evaluate the processing of spent fluorescent lamps, and
technology for the control of mercury emissions from this
process. The procedure involves crushing fluorescent light
lamps, which results in mercury emissions, either in liquid or
vapor form. The lamps are crushed as the first step in
reprocessing. Subsequent to crushing, the broken lamps are
either landfilled, incinerated, or recovered. This study
addresses emissions from the crushing of fluorescent lamps and
the initial handling of the resulting crushed material. The
study does not cover subsequent mercury recovery and refining
operations.
1.2 OVERVIEW OF DOCUMENT
This document provides brief background information on the
use and disposal of fluorescent lamp tubes. The major emphasis
of the document is on the lamp crushing process and associated
mercury emission control devices. Three different crushing
processes are discussed, as well as the air pollution controls in
practice, and the resulting air emissions. This provides the
basis for an evaluation of the effectiveness of various crushing
methods and the efficacy of different air pollution controls.
Some relevant variations on these crushing processes are also
described, along with their potential for emissions. This
document does not address the retorting of mercury-containing
material for the recovery and recycling of elemental mercury, or
the disposal of mercury-containing wastes, resulting from
crushing operations, in landfills. However, these operations are
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mentioned incidentally throughout the document, as they are
closely associated with crushing operations.
2.0 BACKGROUND INFORMATION ON FLUORESCENT LAMPS
2.1 LAMP USAGE
Fluorescent lamps are widely used in businesses, as they
provide an energy-efficient source of lighting. The commercial
and industrial sectors dominate usage of fluorescent lamps,
accounting for over 90 percent of total usage.1 Approximately
five hundred million lamps were manufactured in 1991.: It is
possible that this number will increase substantially, as the EPA
promotes the use of fluorescent lighting as part of its Green
Lights program, which is designed to reduce energy consumption.
Each lamp has a lifetime of three to four years under normal use.
Fluorescent lights are designed so that approximately half of
them will operate after 20,000 hours of operation.1 Where these
lamps are being used on a small scale, they are generally
replaced as they burn out, one at a time. However, in large
companies and industries, this method is not practicable, and,
therefore, group relamping is done on a regular basis.
Typically, group relamping is performed at 15,000 hours, or 75
percent of the lamp's rated life.1 This translates to
replacement every two years for continuous operations, and every
three to five years for noncontinuous operations, which are much
more common. Approximately 20 percent of all lamps are currently
replaced annually.1 Group relamping operations generate large
quantities of lamps to be disposed of at a single time.
2.2 DESCRIPTION OF FLUORESCENT LAMPS
A typical fluorescent lamp is composed of a sealed glass
tube filled with argon gas at a low pressure (2.5 Torr), as well
as a low partial pressure of mercury vapor, thus the tube is a
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partial vacuum.1'2 The inside of the tube is coated with a powder
composed of various phosphor compounds. The composition of this
powder is shown in Table I.1 Tungsten coils, coated with an
electron emitting substance, form electrodes at either end of the
tube. When a voltage is applied, electrons pass from one
electrode to the other. These electrons pass through the tube,
striking argon atoms, which in turn emit more electrons. The
electrons strike mercury vapor atoms and energize the mercury
Table l: Elemental Analysis of Used Fluorescent Lamp Powder1
Element
Aluminum
Antimony
Barium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Sodium
Zinc
Concentration
(mg element/kg phosphor
powder)
3,000
2,300
610
1,000
170,000
9
2
70
1,900
75
1,000
4,400
4,700
130
140
1,700
48
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vapor, causing it to emit ultraviolet radiation. As this
ultraviolet light strikes the phosphor coating on the tube, it
causes the phosphor to fluoresce, thereby producing visible
light. Thus, the mercury in these lamps is critical to the
production of light. The life of the lamp is determined by the
life of the electron producing coating on the cathode, which
diminishes as the lamp is operated.2 The most commonly used
fluorescent lamp is the 40 watt, 4 foot long tube, although
smaller, larger and differently shaped lamps are also used.1
The amount of mercury in fluorescent lamps varies
considerably with manufacturer, and even possibly within
manufacturers.2 Tables 2 and 3 show the mercury content of used
and new fluorescent lamps made by various manufacturers. These
results are from a study conducted by Science Applications
International Corporation for the EPA.2 The National Electric
Manufacturers Association (NEMA) estimates that in 1990, the
average fluorescent lamp contained 41 mg of mercury per lamp.
NEMA predicts that this will decrease to 27 rag by 1995.1
2.3 DISPOSAL OF LAMPS
In a study report prepared for EPA Office of Solid Waste by
Research Triangle Institute (RTI) entitled "Management of Used
Fluorescent Lamps: Preliminary Risk Assessment," it is estimated
that approximately 600 million lamps are disposed each year.
Currently, the largest fraction of lamps are disposed in the
waste stream; 82 percent of lamps are landfilled, 16 percent are
incinerated, and only 2 percent are recycled.1 RTI estimates,
based upon Department of Commerce data and industry information,
that the total amount of mercury entering the U.S. municipal
solid waste system annually (1989) is 643 Mg.1 The contribution
from fluorescent lamps is approximately 24.4 Mg, or 3.8 percent.1
The amount.of mercury emitted from a spent lamp depends on
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Table 2: Mercury Content of Used Fluorescent Lamps2
Manufacturer
Mercury Concentration
(mg of mercury/lamp)
Westinghouse
Westinghouse
Westinghouse
Westinghouse
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
Dayton
Phillips
General Telephone & Electric
Minimum
Maximum
Average
Standard Deviation
21.0
16.6
17.2
61.5
24.4
23.1
0.72
36. 1
115.0
27.2
22.5
17.5
48.0
0.72
115.0
33 . 14
28.91
the way the lamp is handled after it is changed. Discarded lamps
may be transported in two ways: in garbage trucks as household or
commercial trash, or in closed vans or trailers as part of a bulk
relamping program. In the former case, used lamps are simply
disposed in a dumpster, which is then transported to the landfill
by a garbage truck. It is assumed that all of the lamps in
garbage trucks are broken and that vaporized mercury in these
trucks finds its way to the atmosphere.1 In the case of bulk
relamping programs, the discarded lamps are packed in corrugated
containers from which the new lamps were taken and are then
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Table 3: Mercury Content of New Fluorescent Lamps'
Manufacturer
Mercury Content
(mg of mercury/lamp)
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
General Electric
Minimum
Maximum
Average
Standard Deviation
35.8
40.2
29.3
33.0
18.8
15.1
14.3
15.7
19.1
20.5
44.8
15.7
14.3
44 .8
25. 19
10.87
loaded into enclosed vans or trailers for removal to a landfill.
In this case, it is assumed that few lamps are broken and
practically all of the mercury is retained in the landfill.1
In any case, recovery of the mercury in lamps appears to be
desirable, in that the net amount of mercury ultimately released
to the environment is reduced. The recovery process begins with .
the crushing of lamps to extract the white phosphor powder, which
contains the bulk of the mercury. This powder is then put into a
mercury retort to recover elemental mercury.
There are presently few mercury recycling facilities in the
country. Most facilities are located in California or Minnesota.
The State of Minnesota is now enforcing a requirement passed, by
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the Minnesota Pollution Control Agency (MPCA) on May 8, 1992 that
declares used fluorescent and high intensity discharge lamps with
specified levels of mercury are hazardous waste, and as such must
not be landfilled if a recycling option is available.3 The State
of Minnesota is also requiring that businesses store their spent
lamps until such a facility is available to them.3 This has
provided a substantial impetus to development of recycling and
recovery operations in Minnesota.3
2.4 MERCURY EMISSIONS
The disposal of mercury-containing fluorescent lamps and the
potential for emissions therefrom is of concern because mercury
is a highly toxic heavy metal, which bioaccumulates through the
food chain.1 Mercury also has a vapor pressure of 2X1CT3 mm
(25°C) and is volatile at room temperature. Emissions of mercury
in liquid or vapor form, therefore, need to be considered. The
volatilization pathway is especially significant with respect to
human health concerns, as it results in ambient concentrations of
mercury that can be absorbed through various pathways.1 These
include direct inhalation, or ingestion through the consumption
of contaminated food products, particularly fish. Estimates on
global and national mercury emission vary widely.
EPA's estimates of U.S. anthropogenic mercury emissions are
somewhat incomplete, but indicate levels around 309 Mg/yr.4
Coal-fired power plants, municipal solid waste combustors and
industrial sources account for 110 Mg, 58 Mg, and 32 Mg per year,
respectively (note that this is a worst-case estimate for coal-
fired power plants; i.e., all mercury in the coal is emitted).4
Based upon air emission and mass balance information received
from the MRT AB mercury recovery system, RTI estimates that only
0.005 Mg of mercury are emitted each year from all recycling
plants combined.1 This number may have increased somewhat,
because there are more recycling plants operating now than there
were at the time of the study.
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3.0 LAMP CRUSHING PROCESSES
The crushing of fluorescent lamps to separate the glass from
the phosphor powder in the lamp is commonly the first step in
recycling of mercury; although some companies use other methods,
such as removal of the phosphor powder by air vortex or by
flushing with hydrochloric acid.1 Although separation of the
phosphor powder and, hence, the mercury, from the glass and metal
endcaps is necessary for recycling and recovery of mercury, it is
not done only to facilitate this process. Crushing of mercury-
containing fluorescent lamps is also done in order to reduce the
volume of the lamps being disposed in landfills.
In this section, several different systems used for the
crushing of fluorescent lamps are described. Information was
gathered from RTI's "Management of Used Fluorescent Lamps: A
Preliminary Risk Assessment,"1 and through conversations with
different individuals involved in the processing of fluorescent
lamps. These individuals were from both recycling companies''6'7'8
and State agencies.3'9
Three different crushing systems are described in detail in
the following sections. These are: (i) the basic crushing
system; (ii) the MRS crushing system; and (iii) the Mercury
Technologies crushing system. The basic system used to crush the
fluorescent lamps is quite similar in many cases, and is a
relatively simple process. Most of the differences between
crushing systems reside in the air pollution controls they have
in place to control mercury emissions from the crushing process.
Thus, in the discussion of each system, particular attention will
be paid to the controls in place, and, where data are available, •
the efficacy of those controls in reducing or eliminating mercury
emissions into the environment.
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3.1 BASIC CRUSHING SYSTEM
3.1.1 Crusher Design
The simplest of crushers is essentially a single unit, with
a crusher mounted on top of a barrel, usually a 55-gallon drum.
This system is used in many industrial facilities to crush their
fluorescent lamps as a means to reduce the solid waste volume
before disposing the material in a landfill.10 In this version,
light lamps are hand-fed to a feeder chute of variable length and
diameter. This chute is not necessarily longer than the lamps
being fed into it. The lamps pass to the crushing unit,
typically consisting of motor-driven blades, which implode and
crush the lamps. From here, the crushed powder drops into the
barrel below the crusher.
3.1.2 Air Pollution Controls
In the simplest of these systems, there are no air pollution
controls on the device.10 The crushed lamps are collected in
drums until they are full, and then the full drums are
transported to one of several facilities. The crushed material
may then be separated into glass, metal, and powder components.
Typically, the untreated powder is then deposited in a landfill.
This is currently the most common method of disposing these
lamps.1 Alternatively, the barrels may be transported to a
mercury recovery facility, which will separate the mercury-
containing phosphor powder from the crushed glass and aluminum
endcaps, and recycle all the materials.
A more sophisticated version of this barrel-mounted crusher
utilizes a negative air exhaust system to draw the crushed debris
and prevent it from reemerging through the feeder tube.11 The
drawn air is then passed through a High Efficiency Particulate
Air (HEPA) filter to remove particulate matter from the exhausted
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air flow. The crushed material is then disposed in one of the
manners discussed above.
3.1.3 Emission Points and Estimates
In the simplified crushing systems discussed above, there
are several emission points.10 The feeder tube itself is a
potential emission point. The length of this tube, as well as
the length of the lamps being crushed, affects the magnitude of
emissions from the feeder tube. Additionally, the juncture
between the crushing unit and the receiving barrel below is a
possible emission point, depending on how well the connection is
sealed. Finally, an emission point of concern is the collection
barrel itself. Whenever this barrel is removed from the crushing
unit for disposal at another facility, the open area of the
barrel constitutes a potential emission point. All these points
are relevant when there are no air pollution controls in place.
In the modified case, where negative air is employed, emissions
through the feeder tube may be reduced or eliminated entirely,
depending upon the strength of the air flow.
In many cases, actual emission estimates have not been
determined; rather, occupational exposure estimates have been
derived from ambient air measurements taken in the workplace.10
For the case of the simplified system discussed above, Kirschner,
et. al., conducted a workplace study of mercury emissions from a
similar fluorescent lamp compaction unit. In this case, the
compaction was performed to reduce volume prior to landfilling.
This unit consisted of a crusher mounted on top of a 30 gallon
drum, with a feeder tube of an unspecified length. When the
study was undertaken, no air pollution controls were in place on
this device. The scientists observed significant dust emissions
from the mouth of the feeder tube, and the juncture between the
crusher and the collection drum. Indoor ambient air monitoring
revealed ambient mercury levels that varied widely with different
lamp inputs (possibly due to manufacturer variability).
10
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Nonetheless, the measurements indicated levels of mercury near
to, as well as above the Occupational Safety and Health
Administration (OSHA) limits of 0.05 mg/m3.10'12 Results of this
study are shown in Table 4. During the test, 300 lamps were
crushed in a 20 minute period, yielding an average operational
crushing rate of 15 lamps per minute.10 The researchers
concluded that such uncontrolled fluorescent lamp crushers should
be considered emitters of mercury.10
Several controls were put in place in the crusher to
determine if mercury emissions could be reduced: 1) gasketing was
applied to seal the area around the connection between crusher
and drum; 2) the crushing unit was housed entirely within a shed
which allows fluorescent lamps to be fed in from outside; and
3) a 55 gallon disposable barrel was substituted for the
collection barrel. In the third control, the disposable barrel
Table 4: Airborne Mercury Levels Associated with
Fluorescent Lamp Compaction Unit (mg/m3)10
Sample
Distance (ft.)
Background
Trial 1
Trial 1, Time
Area Samples
ABC
5 20 50
0.0002 0.0010 0.0006
0.31
Personnel
Samples
D E
15 20
0.54 0.65
0.02 0.03
OSHA
Limit
0.05
0.05
0.05
Weighted
Average
Trial 2
Trial 2, Time
Weighted
Average
3.00 0.09 0.10 2.23 1.82 0.05
0.12 0.10 0.05
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became the final waste receptacle. When filled it was disposed
directly to the company's sanitary landfill, rather than being
emptied into a dumpster, thus eliminating one step in the
transfer process, and reducing employee exposure to mercury
emissions.
Preliminary tests indicated that all these measures were
useful in reducing emissions.10 Nonetheless, the authors
concluded that fluorescent lamp crushing units should be
considered emitters of mercury unless ventilation and adsorbent
capabilities, such as carbon filters, are added.10
A further example of the problems with uncontrolled crushing
devices is illustrated in the case of Quicksilver Products.1
This company, located in California, briefly entered the business
of fluorescent lamp crushing. Their lamps were crushed outside
in a unit mounted on top of a 55 gallon drum. An air separation
system was used to remove the phosphor powder and mercury from
the glass. This facility was closed down for violations of s;afe
operating practices. Extensive contamination was found around
the facility; high concentrations of mercury were measured in the
soil, rinse water, and on a nearby roof.
3.2 MRS CRUSHING SYSTEM
3.2.1 Crusher Design
Mercury Recovery Services (MRS) is a mercury recycling plant
located in California. The information about their crushing
process presented below was provided by the company.7 The
fluorescent lamp crushing apparatus operated by MRS is more
sophisticated than the basic system described above, particularly
in terms of the air pollution controls. The process currently in
operation is described in detail here. However, the company is
in the process of developing a new design which will be patented,
thus, specific information on the new design is proprietary and
is not included in this report. MRS did indicate that the new
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system will include a self-loading apparatus where lamps will be
deposited for delivery to the crusher, and a totally enclosed
operation to separate the glass, endcaps, and phosphor powder
within the system.
The current crusher operated by MRS is a hand fed apparatus
with two feeder chutes. One chute is 5 feet long, to accommodate
4 foot lamps, and the other tube is 9 feet, in order to
accommodate 6 to 8 foot lamps. Each chute is placed at an angle,
and has a 9 inch by 12 inch opening, which can accommodate
several lamps at a time. The lamps are delivered down this
angled tube onto a motor driven blade made of heavy gauge
hardened steel rotating at 2700 rotations per minute. The
rotating blades implode and crush the lamps as they arrive. The
crushing unit has an operating capacity of 62.5 lamps per minute.
A vacuum system collects air from beneath the crusher,
preventing mercury laden air from exiting through the feed tube.
Material collected in the vacuum system first passes through a
cyclone separator. This removes glass particles, which drop into
the drum. Air from the cyclone separator contains phosphor
powder and some mercury vapor. These are removed by further
controls, as discussed below.
At the end of the process, the glass and aluminum are sent
to recyclers. The phosphor powder is sent to a mercury recovery
company for retorting and recovery of the mercury.
3.2.2 Air Pollution Controls
After passing through the cyclone, the air is pulled through
to a baghouse, where 9 fabric filters trap particulate matter in
the air stream. Every 45 seconds, these fabric filters are
cleaned with a reverse pulse of air. The air leaving the
baghouse is typically composed only of air and mercury vapor.
This air and mercury vapor mixture continues through several more
particulate matter filters and HEPA filters, to ensure that all
particulates have been removed. From here, the exhaust is
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delivered to two 250-pound activated carbon beds, which trap the
mercury vapor. These carbon beds are replaced at saturation,
typically after two years. The airflow is then directed through
yet more particulate matter filters to trap any carbon that may
have been carried along from the activated carbon beds.
At this point in the air pollution filter chain, a five to
ten horsepower pump exhausts the air flow into a mediator
(essentially an area where air from the different sources is
mixed prior to discharge into the warehouse area). Air is also
being pumped from the containment room through the mediator on a
continuous basis," and subsequently to another series of
particulate filters and more activated carbon. Therefore, air
from the crushing unit and the containment room is mixed, after
filtration, and discharged into the warehouse area. Thus, in
addition to cleaning the exhaust air from the crushing unit, the
system cleans the air in the containment room six times per hour.
Air flow through the filter chain is 25 cubic meters per minute
(900 cubic feet per minute), on average. The entire crushing
system and filter chain is enclosed within a containment room,
which is itself within a warehouse. After all air has passed
through the entire filter system and been cleaned, it is pumped
into the containment room and to the warehouse, essentially a
closed loop system. The only exchange of air with outside
ambient air would occur incidentally in the warehouse, such as
when doors are open and closed, or at points in the warehouse
that are not airtight.
The entire process is vacuum sealed and monitored
continuously for leaks and to ensure that air in the containment
area is in compliance with OSHA regulations. In the case of a
leak, work ceases until the leak is repaired, and then resumes.
Effectively, the only time where levels of mercury in the
workplace may approach the OSHA limit of 0.05 mg/m3, is when
lamps have been dropped and broken.7 No efficiencies of control
devices are cited; rather, MRS monitors constantly and bases
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their determination of adequacy on measured mercury levels in the
workplace.
3.2.3 Emission Points and Estimates
This crusher is designed to ensure that there is no leakage
of air from the system.1 The opening through which the lamps are
fed is a potential emission point, but strong negative air flow
pulling on the crushing apparatus prevents emissions from
resulting. Additionally, the negative air flow ensures that the
entire filter process is vacuum sealed. The entire system is
continuously monitored for leaks.
No emission estimates are available for this particular
process, because the company monitors constantly for compliance
with OSHA as its standard and bases their determination of
control device adequacy on measured ambient mercury levels in the
workplace. As noted above, the MRS crusher is controlled by a
combination of fabric filtration and carbon adsorption.
To provide a basis for estimation of control device
effectiveness in the fluorescent lamp crushing process, EC/R
investigated other industries where carbon adsorbers are used to
control mercury emissions. In the chlor-alkali industry, carbon
adsorbers applied to mercury vapor streams attain outlet
concentrations under 50 parts per billion (ppb), and sometimes as
low as 1 ppb.13 Although outlet concentrations have not been
measured for a lamp crushing operation, it is reasonable to
assume that comparable concentrations could be attained if the
carbon adsorption system is well designed and operated.
Therefore, using outlet concentrations from the chlor-alkali
plants and the reported airflow for the MRS unit, mercury
emissions would range from 0.2 to 10 mg per minute. [According
to Bob Roberts, president of MRS, monitoring indicates ambient
mercury levels-well below the OSHA limit of 0.05 mg/m3. ]
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3.3 MERCURY TECHNOLOGIES CRUSHING SYSTEM
3.3.1 Crusher Design
Mercury Technologies of Minnesota is one of only three
companies in the United States using this particular technology.6
The original developer of this technology was Mercury
Technologies Corporation, a company that operates a mercury
recycling and recovery facility in Hayward, California. The
system is a completely enclosed design that feeds fluorescent.
lamps in one end" to a crusher, passes the exhaust through an
extensive filtering system, and delivers the powder to a thermal
reduction unit (TRU), which recovers the mercury from the
phosphor powder.6 Thus, this system carries out the entire
mercury recycling process, from the crushing of fluorescent light
lamps to the retorting and reclamation of mercury from phosphor
powder.
Lamps are hand-fed into feeder tubes of different lengths,
depending upon the size of the lamps being processed. If 4-foot
lamps are being processed, they are fed into a tube that is 5
feet long, and if 8-foot lamps are being processed, they are fed
into a 9 foot feeder tube. The lamps are fed to the crusher,
which implodes and crushes the lamps into small fragments. The
operating capacity of the unit is 60 lamps crushed per minute.
As with the MRS operation, the entire process is conducted
under negative airflow. The crushed debris is exhausted first to
a cyclone, where the larger particles, such as crushed glass and
aluminum endcaps are separated out. At this point, much of the
phosphor powder drops out into a cyclone hopper. From this
collection hopper, the phosphor powder, containing mercury, is
transferred to the TRU via an enclosed auger conveyer, as
described in the following section.
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3.3.2 Air Pollution Controls
After the cyclone, the airflow proceeds to a baghouse, where
fabric filters continue to remove particulate matter from the
airstream. The fabric filters are cleaned with a reverse pulse
mechanism, and the powder that drops out here is also routed to
the cyclone hopper. The air stream leaving the baghouse proceeds
to a HEPA filter, and then to a potassium iodide-impregnated
carbon filter. This removes the mercury vapor, by precipitating
it in the form of mercuric iodide (no removal efficiencies were
cited). The air in the building that houses the self-contained
unit is also under continual negative air pressure. Thus, all
this air is drawn through the entire filter system as well.
There is no exhaust to the outdoors. Rather, all air is
recirculated back into the workplace. Air flow through the
system is approximately 18 cubic meters per minute (650 cubic
feet per minute).
From the cyclone hopper, the powder, which consists mainly
of 6 to 12 /xm particles, is auger-conveyed to the TRU. An auger
conveyor is a tube with a 6-inch diameter, and a screw or helix-
like component that pushes the powder up through the tube to the
TRU. Here, the powder is retorted to recover separate fractions
of elemental mercury and phosphor powder.
3.3.3 Emission Points and Estimates
Because of the design of this mercury recycling and recovery
system, there is virtually no leakage of air from the lamp charge
chute. As with the MRS system described above, the entire
process is carried out under negative air pressure, which
prevents emissions from the mouth of the feeder tube.
Furthermore, because recovery of the mercury is carried out in
the same self-contained unit as lamp-crushing, there is no point
where the transfer of phosphor powder to a subsequent processing
device can result in emissions.
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Mercury Technologies of Minnesota monitors their indoor air
regularly, and the company consistently operates with indoor
levels of mercury of approximately 0.005 mg/m3, which is an order
of magnitude lower than the OSHA limit.6 The plant is shut down
if levels reach 0.01 mg/m3.
No information is available regarding the particular
effectiveness of different control devices; instead, the facility
relies upon its workplace monitoring to ensure that emissions are
restricted or eliminated. As previously stated, carbon adsorbers
applied to mercury vapor streams in other industries typically
achieve outlet mercury concentrations under 50 ppb, and sometimes
as low as 1 ppb.13 If it is assumed that these levels are
attained by the Mercury Technologies system, then using these
outlet concentrations and the reported air exhaust rate for the
crusher, mercury emissions would range from 0.14 to 7 mg per
minute.
3.4 OTHER VARIATIONS
The crushing systems discussed above demonstrate the range
of available technology, and are generally representative of the
fluorescent lamp reduction and recycling industry. After the
most simple crushing units have been expanded upon, most of the
differences between crusher systems result from differences in
pollution control devices. Several industry representatives
contacted during this study articulated the feeling that the
basic crushers mounted on top of barrels are inadequate methods
and pollute excessively.6'7'8 This is due to the fact that,
although most of the mercury is contained in the phosphor powder,
a considerable percentage of the mercury is in vapor form, and
therefore will not be removed by particulate capture methods.
This leads to an environmental problem in the form of mercury
emissions.
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3.4.1 Transfer Operations
Removal of the collection barrel (55-gallon drums) from the
collection device (e.g., cyclone separator, baghouse) and placing
the seal and lid on it constitutes a potential emission point.
The 55-gallon drums are Department of Transportation-approved
vessels, and are sealed as soon as they are removed from the
crushing device. USALights of Minnesota said that this procedure
is carried out very rapidly to minimize emissions.8 The workers
involved in this operation all wear respirators and protective
clothing during the operation to minimize their exposure to
mercury. USALights replaces its barrels about once every two
weeks.
Typically, when facilities do not recover mercury on-site,
they must ship it elsewhere for further processing. In
Minnesota, this is done under a hazardous waste manifest, and all
mercury is shipped with a licensed hazardous waste transporter.8
3.4.2 Removal of Endcaps
An operation which is not discussed in detail here, because
it does not involve crushing of the light lamps, is carried out
by a company called Lighting Resources.1 Lighting Resources
received a variance for treatment of used fluorescent lamps in
California in January 1991. The variance allows operation of
equipment as a prototype unit to determine optimal treatment
conditions.
Instead of crushing the lamps, this company's process cuts
off the endcaps, thereby releasing the vacuum in the lamp, and
then removes the phosphor powder with an air vortex. The
phosphor powder is then collected in a cyclone separator. The
process is operated at a low temperature (actual temperature
value was not reported) in the process room to reduce
volatilization of mercury.1
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3.4.3 MRT AB Mercury Recovery Systems
MRT AB, a company based in Sweden with worldwide operations,
has one of the more refined mercury reclamation operations in the
world.1 The operation is a full scale system for the recovery of
mercury from fluorescent lamps, batteries and other mercury-
containing waste. They use a batch distillation retort to
reclaim the mercury, and have developed a modular design that
allows their plants to handle widely varying numbers of inputs
(lamps). The smallest of their units is a single lamp crusher
with a distilling unit that can handle up to 200,000 lamps per
year.
The entire system is enclosed and operated under negative
pressure to minimize fugitive emissions. The system vents to
carbon filtration units for mercury emission control. MRT AB
closely monitors emissions from all their systems. Based on
measurements downstream of all their charcoal filters, MRT states
that air emissions from their crush/sieve unit has an average
mercury concentration of 0.5 /ig/m3, resulting in annual emissions
of 1 g/year.1 Emissions from the crush/sieve ventilation room
are also 0.5 /xg/m3, yielding 5.25 g/year in annual emissions.1
The differences are due to differences in operating hours. No
inlet concentrations or control device efficiencies were
reported. The MRT system is used successfully by RecycLights of
Minnesota.5
4.0 MERCURY RECOVERY
After crushing of fluorescent light lamps, mercury recovery
is often the next step taken in the recycling process. Most
commonly, crushed lamps that are not. landfilled undergo retorting
or roasting.1 These processes recover mercury by distillation
(i.e., heating the material to vaporize the mercury and
subsequently collecting it by cooling the offgas stream to
condense liquid elemental mercury). Different versions exist,
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but in each, the material is heated to vaporize the mercury and
recover it as a liquid. This can be accomplished in closed
vessels (retorts) or in open-hearth furnaces, ovens, or rotary
kilns (roasting).1 Recovery of the vaporized mercury can be done
with condensers and separators or with a venturi scrubber and
decanter, followed by an air pollution control system.1
Retorting generally gives higher recovery rates than does
roasting, and is also well-suited to wastes containing volatile
forms of mercury (e.g., elemental, oxidized species). Thus
retorting is generally the recovery method of choice for
fluorescent lamps T1
Generally, the mercury-containing wastes are placed in a
retort, and heated for four to twenty hours to a temperature
above the boiling point of mercury (357°C) but below 550"C.1
Vaporized material from this process is condensed in the scrubber
or condenser, and then it is collected in a collector or
decanter. This collected mercury may require additional
treatment, such as nitric acid bubbling, to remove impurities.1
The potential emission points from a retort process include
the condenser or scrubber vent and the handling areas for waste
feed and recovered mercury.1 Fugitive emissions from these
points may be controlled by enclosing the entire system and
operating it under negative pressure, similar to the system at
MRS AB, as previously described. There may also be mercury
emissions from scrubber wastewater. Final treatment of these
wastes has been shown to be achieved with activated carbon, with
the used carbon being disposed at a hazardous waste landfill.1
5.0 DISCUSSION AND CONCLUSIONS
A typical four-foot fluorescent lamp contains about 41 mg of.
mercury, although this value is expected to decrease to 27 mg by
1995. The maximum measured concentration is found in the white
phosphor powder on the inside surface of the glass. The vapor in
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the lamp would contain about 0.04 rng of mercury at room
temperature (assuming the vapor is saturated with mercury).
The amount of mercury emitted from a spent lamp depends on
the way the lamp is handled after it is changed. In one extreme,
used lamps are simply broken into a dumpster and transported to
the landfill in a garbage truck. It is assumed that all of the
lamps in garbage trucks are broken and that vaporized mercury in
these trucks finds its way to the atmosphere.1 In the other
extreme, the discarded lamps are packed in corrugated containers
from which the new lamps were taken and are then loaded into
enclosed vans or_trailers for removal to a landfill. In this
case, it is assumed that few lamps are broken and practically all
of the mercury is retained in the landfill.1
In any case, recovery of the mercury in lamps appears to be
desirable, in that the net amount of mercury ultimately released
to the environment is reduced. The recovery process begins with
the crushing of lamps to extract the white phosphor powder, which
contains the bulk of the mercury. This powder is then put into a
mercury retort to recover elemental mercury.
Lamps can be crushed either by a mobile crushing unit at the
point of collection, or by a centralized stationary crushing
unit. Both of these operations generally use small lar.p crushing
units which fit on the top of a 55 gallon collection drum.
Industrial hygiene measurements around these drum-mounted
crushers have shown that, even in a well-covered crusher, some
mercury escapes from the lamp feed tube, causing concentrations
of about 0.3 mg/m3. This is well in excess of the OSHA limit of
0.05 mg/m3.
Two well-controlled crusher systems were identified. Both
of these use a vacuum collection system to prevent release of
mercury from the lamp feed system. In both cases, the air is
passed through a cyclone, a HEPA filter, and a carbon adsorber
before being exhausted. The cyclone removes glass particles; the
HEPA filter removes the phosphor powder, which contains most of
the mercury; and the carbon adsorber captures mercury vapor.
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Typically, depending upon the specific operation and the degree
of mercury contamination, the glass particles, HEPA filters, and
carbon adsorbers are either processed to recover the mercury or
disposed of in a hazardous waste landfill.
These controls reduce mercury levels near the crusher to
well below the 0.05 mg/m3 OSHA limit. This implies an emission
reduction of at least 90 percent. Table 5 compares calculated
and measured mercury emissions and concentrations from different
crushing systems.
Table 5: Comparison of Calculated and Measured Emissions
from Different Crushing Systems
Resulting
Mercury
Concentration
(mg/m3)
Estimated Emissions
(mg/min)
(mg/lamp)
Amount of mercury
in the vapor in a
lamp (4 foot)
prior to breakage
(for comparison)
Simple covered
system with no
add-on control
MRS
Mercury
Technologies
0.04'
0.3D
<0.05C
<0.05C
0.2-10°
0.14-7C
0.003-0.16d
0.002-0.117d
aMercury in the vapor phase, calculated based on the vapor
pressure of elemental mercury.
bMeasured five feet from crusher.
°Rough estimate using the reported air flow rate and typical
exhaust characteristics from a carbon adsorber controlling
mercury vapor emissions.
Calculated using the reported rate of lamp-crushing.
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6.0 REFERENCES
1. Truesdale, R.S., S.M. Beaulieu, T.K. Pierson. Management of
Used Fluorescent Lamps: Preliminary Risk Assessment.
Prepared by Research Triangle Institute, Research Triangle
Park, North Carolina, for the Office of Solid Waste, U.S.
Environmental Protection Agency. Revised May 1993.
2. Science Applications International Corporation. Analytical
Results of Mercury in Fluorescent Lamps. Prepared by
Science Applications International Corporation, Falls
Church, Virginia, under Contract No. 68-WO-0027 for the
Office of Solid Waste, U.S. Environmental Protection Agency,
Washington, D.C. May 1992.
3. Brist, Jim. Minnesota Pollution Control Agency,
Minneapolis, Minnesota. Personal communication. August
1993.
4. National Emissions Inventory of Mercury and Mercury
Compounds: Interim Final Report. EPA-453/R-93-048.
December 1993.
5. Boerjan, Dale. Recycling Coordinator, RecycLights,
Minneapolis, Minnesota. Personal communication. August
1993.
6. Kite, Ray. Mercury Technologies of Minnesota, Pine City,
Minnesota. Personal communication. August 1993.
7. Roberts, Bob. President, Mercury Recovery Services,
Monrovia, California. Personal communication. August L993.
8. USALights, Roseville, Minnesota. Personal communication.
August 1993.
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9. Nickel, Eric. California Department of Health Services,
Toxic Substances Control Program, Alternative Technology
Division, Sacramento, California. Personal communication.
August 1993.
10. Kirschner, D.S., R.L. Billau, and T.J. MacDonald.
Fluorescent Light Tube Compaction: Evaluation of Employee
Exposure to Airborne Mercury. Applied Industrial Hygiene
Vol. 3, No. 4: pp. 129-131. April 1988.
11. Flynn, Mike. Vice President, Intersol, in letter to Florida
Department of Environmental Regulation. 1992.
12. American Conference of Governmental Industrial Hygienists.
Threshold Limit Values and Biological Exposure Indices for
1987-88. Pg. 25. 1987.
13. Anastas, M.Y. Molecular Sieve Mercury Control Process in
Chlor-Alkali Plants. EPA-600/2-76-014, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina.
January 1976.
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