Transcript Presentación de PowerPoint

MERCURY IN
CEMENT
Autor (es): John Kline
Charles Kline
Compañía: Kline Consulting
Importance of Mercury
The World Health Organization states:
“Mercury is recognized as a chemical of
global concern due to its ability to travel long
distances in the atmosphere; its persistence
in the environment; its ability to accumulate
in ecosystems, including in fish, and its
significant negative effect on human health
and the environment.”
REGULATIONS
United Nations Mercury Treaty
Geneva – January 19, 2013
“ Today in the early hours of 19 January 2013 we
have closed a chapter on a journey that has
taken four years of often intense but ultimately
successful negotiations and opened a new
chapter towards a sustainable future. This has
been done in the name of vulnerable
populations everywhere and represents an
opportunity for a healthier and more
sustainable century for all peoples”.
Fernando Lugris, the Uruguayan chair of the
mercury treaty negotiations
139 Countries Agree
Legally Binding Treaty on Mercury
The Minamata Convention Calls for …
“A wide range of controls and reductions
across a range of products, processes
and industries where mercury is used,
released or emitted”
Cement industry is specifically identified
Excerpt from the UNEP Press Release
Mercury Limits in LATAM
Country
Limit
Conditions
Notes
Argentina
0.03 mg/Nm3
10% O2, Dry, 0 C
Hazardous wastes
Brasil
0.05 mg/Nm3
7% O2, Dry, 0 C
Wastes
Colombia
0.05 mg/m3
11% O2, 25 C
Hazardous wastes
Costa Rica
0.28 mg/m3*
7% O2, Dry, 25 C
Alternative fuels
Chile
0.10 mg/Nm3
10% O2, Dry, 25 C
Co-incinerators
Ecuador
0.08
7% O2, Dry
Hazardous wastes
Honduras
0.05 mg/Nm3
7% O2, 0 C
Mexico
0.07 mg/m3
7% O2, Dry, 25 C
Nicaragua
0.28 mg/m3*
7% O2, Dry, 25 C
Waste Oils
Panama
<0.1 mg/m3
7% O2, Dry, 25 C
Hazardous wastes
Puerto Rico
0.12 mg/m3
7% O2, Dry 20 C
Hazardous wastes
Uruguay
<0.05 mg/Nm3 0 C
* Includes Cd & Hg
Source: FICEM
Wastes
US - Three New Regulations
• National Emission Standards for Hazardous Air Pollutants
(NESHAP) for the Portland Cement Manufacturing
Industry and Standards of Performance for Portland
Cement Plants
– Final Rule published on February 13th
• Commercial and Industrial Solid Waste Incineration Rules
(CISWI) also revised for kilns firing solid waste fuels
– New definition of waste introduced
• Mercury and Air Toxics Standards (MATS) rule will regulate
mercury monitoring and reductions from the US coal and
oil fired power industry
– Final Rule Published on February 16, 2012
European Union
• EU directive 96/61/EC on Integrated Pollution
Prevention and Control (IPPC)
• Best Available Technology (BAT) and achieving
Associated Emission Levels (AELs) below 0.050
mg/Nm3.
• BAT Reference Document (BREF) for the cement
and lime industries that was approved in 2009.
• Cement kilns are expected to utilize BAT
technologies to reduce emission levels however
the allowable emission target is somewhat
flexible.
GLOBAL PICTURE
Mercury Emissions by Region
Cement Hg Emissions - LATAM
Cement Hg as % of National
MERCURY IN THE ENVIRONMENT
Earth’s Crust
• Average of 50 ppb in earth’s crust
• Concentrated in areas of volcanic
activity
– Precipitates in new crust HgS (requires
pressure and temperature)
• Historically, cinnabar mined in volcanic areas
– Released to the atmosphere or surface
water, precipitates to background levels,
and is ultimately returned to earth’s crust
through organic matter (limestone, coal…)
Atmospheric mercury
deposition
Wyoming's Upper
Fremont Glacier over the
last 270 years
Note: both local and global
influences
33 %
33 %
33 %
MERCURY IN CEMENT
MANUFACTURE
Cement – 9 %
Plus a portion of
Fossil Fuel for Power
Raw Materials
1
Limestone
Clay
Mercury Concentrations in PPM
Max
0.1
Mean
0.01
0.001
Min
Shale
Sand
Flyash
Bottom Mill Scale
Ash
Fuel Sources
Mean Values 0.035 – 0.095
And materials can vary over time
Monthly mass balance Hg contributions by raw material (Linero, Read, and Derosa, 2008)
MERCURY CYCLES
Mercury Cycles
• Mercury is a volatile element similar to
chlorine and alkalis, but with a lower
condensation temperature
• Virtually all the mercury in the kiln system is
volatilized before or in the burning zone
• Virtually all of the mercury leaves the
preheater in a gaseous form
• However, much of that mercury is caught and
returned to the system
Mercury Cycles in Cement
Kiln Feed
330 oC
Stack
1000 oC
Fuels From Kil
& Precalciner
90 oC
Raw Mill
BH Catch
Coal Mill
Source: "Fate and transport of mercury in Portland cement manufacturing facilities", J.K. Sikkema. Theses and Dissertations. Paper 11907. http://lib.dr.iastate.edu/etd/11907
Mercury Cycles
1000%
900%
800%
700%
Plant A Mill On
600%
Plant A Mill Off
500%
Plant B Mill On
Plant C Mill On
400%
Plant D Mill On
Plant E Averaged
300%
200%
100%
0%
Raw Coal
As Fired
Fuel
Raw Mill
Feed
Kiln Feed
Preheater
Exit
Raw Mill
Product
CKD
Stack
Mercury Emissions Raw Mill Off + Raw Mill On
Scale Change
Schreiber & Kellett 2009
MERCURY STATES & OXIDATION
Factors that impact oxidation
• Temperature Profile
– Time
– Temperature
• Level of Oxygen in gas
• Level of moisture in gas
• Amount of halogens in gas
– Cl, F, Br, I
• Chemicals that interact with halogens
– K, Na, SO2 / SO3
Mercury oxidation occurs
Influencing
Factors
Temperature
Cl Available
O Available
SO3 Available
Oxidation
• Oxidized mercury is water soluble
• Oxidized mercury is easier to capture
• Oxidized mercury becomes easily particle
bound
• Elemental mercury is none of the above
• Therefore, we like mercury to be oxidized
Mercury Emissions Averages All Cement Kilns Surveyed
Good
Generalization but
each case is specific
Schreiber & Kellett 2009
MERCURY MEASUREMENT
Sorbent Trap Monitoring Systems
•
•
•
Known volumes of flue is pulled through a sorbent.
Vapor phase Hg is collected on the sorbent.
Typical sorbent medium is halogenated carbon
Paired sorbent traps are used for quality-assurance purposes
and to ensure measurement precision
A pair of sorbent traps is typically used for 24 to 168,
before being removed and analyzed.
Less expensive, but only good if emissions are steady
36
Continuous Emissions Monitors
(CEMs)
• Measure emissions continuously
• Expensive to install and operate
• Give a continuous signal, many differentiate
between oxidized and elemental
• Good for investigations and plants with
variable emissions patterns
– In-line raw mills
– High variability in inputs
APPROVED CEMS(CEMs)
• German UBA http://www.umweltbundesamt.de/luft/mess
einrichtungen/e_quecksilber.pdf
US EPA - http://www.epa.gov/etv/vtams.html#mcem
MERCURY ABATEMENT
Dust Wasting (2 – 35%)
Taking the baghouse dust out of the kiln feed
Advantages
• Low Capex Requirement
• Dust can often be shuttled to cement
• Adjustable to needs
Disadvantages
• Low reduction potential
• Capture depends on particle bound mercury
• Can be ineffective when in-line raw mill is off
Dust Roasting (25 – 75%)
Removing the mercury captured on the dust by heat
treating the dust and recapturing the mercury in a
concentrated stream
Advantages
• Can use the dust as raw feed or product
• Relatively low Capex
Disadvantages
• Can only roast what is captured, so limited capture
• Need a sorbent or other system to trap the mercury
• Hazardous waste to remove from plant
Chemical Fixers (5 – 50%)
Chemicals that are added to the gas stream to “fix” mercury,
usually as a sulphur compound
Advantages
• Avoid the issues associated with activated carbon
• Little Capex required, may be able to use existing equipment
Disadvantages
• Not proven
• Chemicals may be expensive
• Limited temperature range to work within
• May cause “problems” in cement kilns
Wet Scrubber Systems (5 – 60%)
Using a wet scrubber to remove water soluble (oxidized) mercury
from the flue gas
Advantages
• May already be installed or required for SOx control
Disadvantages
Dry Kiln
• Capex intensive $50 mn to $250mn +
System with
• Can only scrub oxidized mercury
SOx Problem
• Need oxidizer system to produce gypsum
• Can have re-emission of mercury from liquid
– Typically 20% and will be in elemental form
• Mercury trapped in liquids will need cleaning
• Mercury trapped in gypsum, may make it unusable in cement
(waste to land fill)
Dry Sorbent Injection (50 – 90%)
Using a dry sorbent (most likely activated carbon) to capture
gaseous emissions
Advantages
• Low capital costs to install
• Easy to operate
• Sorbent rate can be varied according to needs
Disadvantages
• Baghouse dust must be removed from the kiln feed
• Sorbent may impact cement properties (air entraining) if dust
and sorbent is added to cement
• Therefore, may require off-site disposal
Semi Dry Scrubber (85 – 95%)
Using low temperature, sorbents and particle contact to capture Hg in a
partial or full exhaust stream.
Advantages
• Less Capex than FGD (less than half)
• Can take a partial gas stream
• Can use multiple sorbents
• Simpler to operate
• No waste liquids to treat
• Solid product maybe usable in cement
Disadvantages
• Requires a particulate collection device after it
• Higher Capex than AC and existing / new baghouse
Estimates of Mercury Capture Efficiency
2 – 35%
2 – 40%
5– 60%
25– 75%
50– 90%
Source: FLSmidth
85– 99%
Estimated Operating Costs
0%
100%
200%
300%
Mercury Reduction Required
400%
Source Adapted from: Gore, Kolde and Knotts 2012
Summary and Conclusions
• 2013 Will be the year in which mercury
emissions will come under a global treaty
• Many countries are already controlling
mercury emissions
• The cement industry accounts for
approximately 9% of the global emissions
• Mercury measurement and abatement
will be coming to the global cement
industry
Summary and Conclusions
• In preparation:
• Know your mercury balance
– Measure all inputs on a regular basis
– The higher the variability the more frequent the
testing
• Confirm your emissions
– Long wet and dry kilns can use Hg traps
– Kilns with inline raw mills should use CEMs
Summary and Conclusions
• Reduce your emissions now
– Eliminate high Hg inputs (fuel and raw
materials)
– Remove baghouse dust from the kiln feed and
add to the cement
– Consider using oxidizers to enhance mercury
capture
• Plan abatement strategy (<0.05 mg/Nm3)
Appendix