mercury in cement n.
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  1. MERCURY IN CEMENT Autor (es): John Kline Charles Kline Compañía: Kline Consulting

  2. Importance of Mercury The World Health Organization states: “Mercury is recognized as a chemical of globalconcern 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.”

  3. Regulations

  4. United Nations Mercury Treaty

  5. 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

  6. 139 Countries AgreeLegally 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

  7. Mercury Limits in LATAM * Includes Cd & Hg Source: FICEM

  8. 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

  9. 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.

  10. Global Picture

  11. Mercury Emissions by Region

  12. Cement Hg Emissions - LATAM

  13. Cement Hg as % of National

  14. Mercury in the Environment

  15. 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…)

  16. Atmospheric mercury deposition Wyoming's Upper Fremont Glacier over the last 270 years Note: both local and global influences

  17. 33 % 33 % 33 %

  18. Mercury in Cement Manufacture

  19. Cement – 9 % Plus a portion of Fossil Fuel for Power

  20. Raw Materials Max Mercury Concentrations in PPM Mean Min

  21. Fuel Sources Mean Values 0.035 – 0.095

  22. And materials can vary over time Monthly mass balance Hg contributions by raw material (Linero, Read, and Derosa, 2008)

  23. Mercury Cycles

  24. 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

  25. Mercury Cycles in Cement Kiln Feed 330 oC Stack 1000 oC Fuels From Kiln & Precalciner 90 oC Raw Mill Coal Mill BH Catch Source: "Fate and transport of mercury in Portland cement manufacturing facilities", J.K. Sikkema. Theses and Dissertations. Paper 11907.

  26. Mercury Cycles

  27. Mercury Emissions Raw Mill Off + Raw Mill On Scale Change Schreiber & Kellett 2009

  28. Mercury States & Oxidation

  29. 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

  30. Mercury oxidation occurs Influencing Factors Temperature Cl Available O Available SO3 Available

  31. 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

  32. Mercury Emissions Averages All Cement Kilns Surveyed Good Generalization but each case is specific Schreiber & Kellett 2009

  33. Mercury Measurement

  34. 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

  35. 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

  36. APPROVED CEMS(CEMs) German UBA - EPA -

  37. Mercury Abatement

  38. 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

  39. 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

  40. 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

  41. Wet Scrubber Systems (5 – 60%) Dry Kiln System with SOx Problem 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 • Capex intensive $50 mn to $250mn + • Can only scrub oxidized mercury • 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)

  42. 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

  43. 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

  44. Estimates of Mercury Capture Efficiency 2 – 35% 2 – 40% 5– 60% 25– 75% 50– 90% 85– 99% Source: FLSmidth

  45. Estimated Operating Costs 0% 100% 200% 300% 400% Mercury Reduction Required Source Adapted from: Gore, Kolde and Knotts 2012

  46. 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

  47. 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

  48. 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)