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Sustainable Use of Steel Slag in North America

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Presentation on theme: "Sustainable Use of Steel Slag in North America"— Presentation transcript:

1 Sustainable Use of Steel Slag in North America
Workshop: Sustainability of Brazilian Steel Sector Steel Slag – From Generation in Steelworks to Environmentally Sustainable Utilization

2 Agenda Sustainable plan for steel slag in Canada
Agricultural liming standard & certification Risk assessment from US steel slag coalition Properties and sustainable uses of SS in US Phosphorus removal Conclusion

3 Environmental Authority in Quebec, Canada
Ministry of Sustainable Development, Environment & Park Adopt the Rio declaration from 1992 UN conference in Rio Urgency of reconciling economic and social development Environmental protection Conservation of natural resources

4 Residual material in Quebec
Non-hazardous material generated in Quebec = 20 Tonnes per minutes. Quebec Residual Materials Management Policy has goal to reclaim 65% of them by year 2008. For helping, use of laws, regulations, guidelines, R&D, directives, fact sheets, guides and standards. For steel slag tool was: R&D :Bioavailability Evaluation of Heavy Metal Inbound in Industrial Inorganic Residual Materials Guide to reclaim Industrial Residual Material, non-hazardous and inorganic as construction material

5 Evaluation of the material
Description of the process generating Representative sampling Checking if it is non-hazardous Gradation (Sieve analysis) Physical properties Organic matter Capability to neutralize the acid Sulfur contents = acidic generator Total component Leaching tests, neutral and acid

6 Reclaim Agreement for Steel Slag
Agreement between Minister of Environment and the steel Mill which generate the steel slag (SS) Minister facilitate and encourage such value added while ensuring that it is done in a manner that does not harm the quality of the environment SS is not consider soil in the meaning of Soil Protection and Sites Rehabilitation Policy The use of SS is associated with structures and not mingling with soils Contract to set out the terms and conditions governing the interventions, actions, and activities with respect to the recycling

7 Obligation for marketing Steel Slag
Inform purchaser of the potential uses and restriction Proceed periodically to the analysis of SS Present a report specifies the quantity of SS received and the quantity processed and for each category of aggregate, specifies the quantities marketed, stored or disposed Invest part of the benefit from SS sales for R&D Produce & distribute a brochure (approved) intended to Inform customers of the nature of SS Promote the use of SS for authorized uses Subsequent to a dismantling of the work at the end of its useful life, reuse possible (same as permit)

8 Decision-making diagram for aggregate categorization

9 Usage authorized according to category
Category of materials I II III IV V 1. Construction or repair of roadways, roads and streets (including those in residential, municipal and agricultural sectors) Sub-base x Base – paved roads Paved road shoulder Base – unpaved roads Unpaved road shoulder Backfill Mineral filler Manufactured sand Surface treatment Hot and cold mix asphalt Aggregate for slurry seal Filling concrete

10 Usage authorized according to category
Category of materials I II III IV V 2.Winter anti-skid for roads x 3.Residential driveway for automobile 4.Other residential uses 5.Construction on municipal land 6.Construction on commercial or industrial land 7.Coating for landfill sites 8.Sandblast aggregate 9.Railroad Ballast The reuse of SS dismantled from a structure shall be done in accordance with those one

11 Slag sales scale ticket
Usage permitted

12 Slag uses

13 Slag uses

14 Slag uses

15 Slag uses

16 Slag uses

17 Liming material for agricultural use
BNQ is a standards development body accredited by the Standards Council of Canada (SCC) Authorized to develop consensual normative documents (Standards) up to the national level and to participate into regional and international standardization activities In 1998, a committee of 20 persons from different industries and government agencies elaborate the specification: #NQ /1998 Liming Materials from Industrial Processes The certification to have recognized, on an ongoing basis, the conformity of ladle furnace slag according to this specification Certification bring : authenticity, safety of the product and technical info

18 Requirement for certification
BNQ 2 visits and sampling per year Production and sales report to submit Size 100% < 14mm Size 95% < 12,5mm Water content > 1% (CaO) Neutralizing value (CCE) > 25% (our value 85%) Causticity (Ca+Mg)/(Na+K) > 2,5 Marking of the product should be on the scale ticket Efficiency is obtained by comparing the effect of pH increase with pure ACS grade CaCO3 Metal content depend of CCE

19 Metal limit in lime material
Metal (ppm) Dry basis CCE 25% 50% 75% 100% As 37 75 Cd 10 20 30 Co 150 225 300 Cr 530 1 060 1 590 2 120 Cu 378 757 1 135 1 500 Hg 2,5 5,0 7,5 Mn 6 250 12 500 18 750 25 000 Mo 40 Ni 90 180 270 360 Pb 250 500 Se 7,0 14 21 28 Zn 926 1 850 2 778 2800

20 US Geological Survey-2005 Ferrous slags are valuable co-products of ironmaking and steelmaking. In 2005 about 21 million tons of domestic iron and steel slag, valued at about $326 million (f.o.b.) was consumed. There were 29 slag-processing companies servicing iron and/or steel companies or reprocessing old slag piles at about 130 locations: iron slag at about 40 sites in 14 States and steel slag at about 90 sites in 32 States.

21 Risk assessment from US Slag Coalition
In 1998, group of 63 US Steel producers and/or Slag processor companies commissioned ChemRisk for: Comprehensive study of chemical composition of 3 slag types; BF, BOF, EAF : potential human health & ecological risk associated with possible exposure to such slag Study utilized worse-case exposure assumptions in risk calculations Conclusion: “Slag pose no meaningful threat to human health or the environment when used in a variety of residential, agricultural, industrial and construction applications” Steelmaking slag: A safe and valuable product

22 Steelmaking slag composition
Chemically, steelmaking slag is a complex matrix structure consisting primarily of oxides of calcium, iron, silicates, aluminum, magnesium, and manganese in complexes of calcium silicates, aluminosilicates and aluminoferite. These compounds are similar to those found in the natural environment. Typical furnace temperatures of about 1600oC fuses the oxidized components captured in slag. The matrix tightly binds metals found in slag and they are not readily liberated from the particles. Metals in slag are not easily leached. Matrix

23 Physical properties Cubical, vesicular surface
Excellent frictional properties High stability Interlocking High angle of repose

24 Major uses of steelmaking slag aggregates
Bituminous applications: pavement surfaces, surface treatments, asphalt, seal coats, slurry coats and cold patch Concrete aggregate Raw feed for Portland Cement manufacturing Anti-skid (snow and ice control) Stabilization: shoulders, banks, erosion control, gabions and riprap Base and sub-base Unpaved driveways, surface roads, walkways, trails Neutralization: acid mine drainage Agricultural applications: soil remineralization, liming agent, fertilizer Controlled granular fill, structural fill, pipe and tank backfill, berms Fluxing agent for steel mills Landfill cover material Landscaping Trench / drain fields Sand blast grit Roofing granules Bulk filler (paint, plastics, adhesives) Soil stabilization Mineral wool All purpose construction aggregate

25 Risk Assessment Process
To quantify potential threats to human health or the environment Three phases Dose-response assessment Exposure assessment Risk characterization Results demonstrated BF, BOF and EAF slags are safe for use in a broad variety of applications and pose no significant risks to human health or the environment

26 Risk Assessment Conclusion
BF, BOF and EAF slags are a safe sustainable material Steelmaking slag is an environmentally safe product Unique physical structure out-performs natural aggregates Superior construction, industrial and agricultural aggregate A safe, useful and valuable product – not a “solid waste” Emphasis on State and Federal regulatory systems in recognition of the value of steelmaking slag as a product Conserves natural resources

27 Sustainable Utilization of Steel Slag in the US
Bituminous Applications Stone matrix asphalt Superpave Asphalt Chip and Seal Slurry Seal Cold patch Advantages: frictional properties hardness soundness angularity

28 Indianapolis Speedway

29 Sustainable Utilization of Steel Slag in the US
Slag as raw feed in Portland Cement Reduction in CO2 emissions and energy cost Slag has already undergone calcination (clinker) Melts at a lower temperature Improved clinker production 100% yield of cement clinker vs. limestone as low as 60% Chemically compatible CaO SiO2 Al2O3 Fe2O3 Reduce or replace: Iron ore Mill scale Bauxite Clay Sand Fly ash Shale Methods of introduction: Inter-ground in existing raw mill Feed directly into the back end of the kiln (a patented process in the US)

30 Feed into the back end of kiln

31 Sustainable Utilization of Steel Slag in the US
Base Applications Unpaved surfaces Roads and road shoulders Access roads for heavy equipment Parking lots and lay-down yards Driveways Pathways / walkways Equestrian rings / trails Berms Embankments Advantages: Durability Compaction Cementitious properties

32 Unpaved Applications in Arkansas, Mississippi and Utah

33 Sustainable Utilization of Steel Slag in the US
Stabilization Bank stabilization Erosion control High angle of repose Durability Gabions and riprap Dikes and barriers Soil stabilization Current research being performed by the School of Civil Engineering, Purdue University– joint cost sharing between MultiServ and Levy as industry, and the Indiana Department of Transportation

34 Oyster beds in Maryland (2), Wildlife Bird Refuse in Utah and Soil Stabilization in Michigan

35 Gabion basket with steel slag
Rectangular wire mesh basket filled with coarse size (50 to 100mm) Steel Slag To shore up creek bank and control water flow Angular shape and high density provide stability Protection against erosion

36 Sustainable Utilization of Steel Slag in the US
Other Applications Rail ballast Anti-skid for snow and ice control Dark color – absorbs heat from the sun Stays in place Landscape rock Daily Landfill cover Aggregate for septic systems Acid mine drainage Agricultural soil re-mineralization, liming agent, fertilizer

37 Ag-lime in North Carolina

38 Acid mine drainage treatment
SS generate exceptionally high levels of alkalinity over extended periods (several hundred times more than limestone) SS has a high neutralization potential Design and sizing can provide a low-to-zero maintenance No leaching even in acidic condition

39 Requirements vary by State
State regulations EPA regulations Test Methods for materials ASTM AASHTO Environmental testing TCLP Total metals Chemical analysis General testing Sieve analysis (gradation) Specific gravity Absorption Unit weight Moisture density (proctor) LA abrasion Soundness Calcium carbonate Equivalent (CCE) for agricultural applications

40 Analytical Test Methods
U.S. Environmental Protection (EPA) approved test methods Total metals Toxicity Characteristic Leachate Potential (TCLP) pH parameters American Society of Testing Materials (ASTM) distilled water leachate tests for certain metals Bioaccessibility of certain metals Particle size distribution

41 Comparisons TCLP and ASTM leaching tests to determine if any metals in slag would potentially affect groundwater and surface water. Results compared to appropriate TCLP drinking water quality standards and EPA Ambient Water Quality Criteria.

42 EAF Slag for phosphorus removal
Phosphorus = Phosphate (P), a nutrient that may cause lake eutrophication and toxic blue green algae Tests on dairy farm waste water and fish farm Conclusion proved that phosphorus filter with EAF significantly reduced dissolve reactive P (DRP) Removed over 70% of DRP during the first 269 days Need to use wetland pre-treatment to remove suspended solid and prevent clogging EAF can be reuse after treatment as aggregate for farm road.

43 Phosphorus retention mechanism
Steel slag

44 University of Waterloo research
BOF Slag: sorption and co-precipitation removal of phosphate and arsenic and selenium Excellent removal of arsenic to very low levels Effective removal of E-Coli Elevated pH provides environment that eliminates bacteria Elevated pH is buffered by soils and sediments upon release to subsurface

45 Phosphate removal with BOF
North Bay System: Phosphate Versus Time Days of Operation 200 400 600 800 1000 1200 1400 1600 Phosphate-P (mg/L) 5 10 15 20 Raw Phosphate Sand Filter Phosphate BOF Chamber Phosphate From: David Smyth Department of earth sciences, University of Waterloo, Waterloo, Canada

46 Batch Removal Rates with BOF
As(III) + As(V) Se(VI) 1000 1000 800 800 As total (mg/L) 600 600 Se(VI) (mg/L) 400 400 200 200 2 4 6 8 2 4 6 8 Time (h) Time (h) Time (h) Time (h) From: David Smyth Department of earth sciences, University of Waterloo, Waterloo, Canada

47 Montreal Biodome research project
Closed marine system 3000 m3 (large marine aquarium) Home to about 100 seabirds, 600 fishes, 2000 invertebrates from gulf of St-Lawrence Contained 20 mg P/L (60 kg P) Pilot unit of 9.5T remove 7 kg P (0.75 g P/kg slag) lasted 93 days, the flow rate = 3 to 9 L/min During test some animals breed, that showed the good quality of the water Efficiency limited by the formation of a bacterial biofilm

48 Conclusion Reputation Co-product
Quality control of this resource is important Slag processor = aggregate processor SS has more advantage than disadvantage Sustainability = conservation of natural resource

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