Recycling of Municipal Incinerator Fly Ash by Electric Arc Furnaces of Steel Mini Mills

1. (Adopted from The 2nd World Congress and Expo on Recycling July 25-27, 2016 Berlin, Germany ) ) Gordon C. C. Yang, Tsun-Nan Chuang, Chien-Wen Huang Institute of Environmental Engineering & Center for Emerging Contaminants Research, National Sun Yat-Sen University Kaohsiung 80424, Taiwan Email: gordon@mail.nsysu.edu.tw Recycling of Municipal Incinerator Fly Ash by Electric Arc Furnaces of Steel Mini Mills (Photo adopted from ) 1

2. Contents • Introduction • Materials and methods • Results and discussion • Conclusions • Acknowledgments 1

3. I. Introduction（1/9） Waste Management Hierarchy (Ultimate Goal: Pursuing Zero Waste and/or Zero Emission) (Source: Wikipedia) 2

4. I. Introduction（2/9） 3

5. I. Introduction（3/9） • Disposal of Municipal Solid Waste (MSW) in Taiwan • Incineration& landfilling • Large-scale MSWI Plants: 24 (Year 2016) • Municipal Incinerator Fly Ash (MIFA): (1) ca. 500 MT/day in 2005; (2) over 800 MT/day in 2015 • MIFA is a hazardous waste regulated by Taiwan EPA & Basel Convention due to its contents of heavy metals and dioxins/furans. • Current Treatment Method of MIFA in Taiwan • Solidification/stabilization, followed by landfilling 4

6. I. Introduction（4/9） • Pilot and/or Large-Scale Melting of MIFA • Taiwan: Institute of Nuclear Energy Research (in late 1990s) & National Sun Yat-Sen University (2002-2005; 2015-Present) • Japan:Kobe Steel, Daido Steel, JFE Steel, etc. • Commercial-scale melting of MIFA has been practiced in about 80 Japanese plants for the treatment of MSWI ashes(bottom ash + fly ash), with less than 10 plants solely for MIFA. 5

7. I. Introduction（5/9） The Electric Arc Furnace (EAF) 6 (Source: Wikipedia)

8. I. Introduction（6/9） The main steps in the EAF process 7

9. I. Introduction（7/9） (EAF + LF) steelmaking process 8

10. I. Introduction（8/9） • MIFA contains about 30-40 wt% of lime materialresulting from the injection of calcium hydroxide slurry into the semi-dry scrubbers for air pollution control in MSW incineration plants. • High slag basicity (i.e., high lime content) generally is beneficial to the removal of phosphorus during the melting period of steelmaking. Thus, quicklime is required and charged as a raw material into an electric arc furnace (EAF). 9

11. I. Introduction（9/9） • In normal EAF steelmaking, both EAF slag and LF slag (ladle furnace slag) are categorized as nonhazardous, recyclable materials in Taiwan. Contrarily, EAF dust is a listed hazardous waste. • Research Objective -- To assess the attainability of fulfilling the goal of “zero landfill or zero waste of MIFA” if full-scale recycling for these steelmaking by-products can be implemented 10

12. II. Materials and methods（1/3） • Samples of MIFA were collected from two different large-scale MSW incineration plants in Taiwan, designated MSWI-1 and MSWI-2. Both incineration plants employ Ca(OH)2 slurry in their semi-dry scrubbers for dust collection in the exhausts. • Chemicals used were all reagent grade. 11

13. II. Materials and methods（2/3） • The underlying concept of this practice is using the high temperature of molten iron (ca. 1650 ℃) to melt MIFA so that the contained organic pollutants (e.g., dioxins/furans) could be destructed. • Meanwhile, the lime material contained in MIFA can be reutilized to partially replace quicklime used in steelmaking. • The noncombustible component in MIFA would become EAF by-products (dust and slags). 12

14. II. Materials and methods（3/4） • The test procedures employed are outlined as follows: (1) MIFA is injected into the molten iron after each scrap charge is melt. (2) EAF slag (i.e., oxidized slag) resulting from slag foaming operation in the EAF is allowed to flow over the side-mouth of the furnace. Then a composite sample of EAF slag is collected for analyses. (3) Molten iron is transferred to the ladle furnace (LF) via the teeming ladle for the control of the metallic constituents in the bath and further removals of phosphorous, sulfur, and other impurities from the steel. Again a composite sample of LF slag (i.e., reduced slag) is collected for analyses. (4) EAF dust is collected after each test cycle for analyses as well. • EAF capacity (Danieli Corp., Italy): 70 MT/batch • Tap-to-tap cycle time: about 60 min 13

15. III. Results and discussion（1/15） Table 1. Chemical compositions of MIFA specimens obtained from two MSW incineration plants 14

16. III. Results and discussion（2/15） ∵> 5 mg/L, ∴Hazardous Table 2. Heavy metals of concern in different MIFA specimens leached by TCLP 15

17. III. Results and discussion（3/15） Table 3. Chemical compositions of EAF dust, EAF slag, and LF slag obtained from normal steelmaking operations w/o melting of MIFA LF slag EAF slag 16

18. III. Results and discussion（4/15） ∵Pb> 5.0 mg/L & Cd > 1.0 mg/L, ∴Hazardous Table 4. Heavy metals of concern in EAF dust, EAF slag, and LF slag (obtained from normal steelmaking operations w/o melting of MIFA) leached by TCLP Designated recyclable materials(Waste Code: R-1209 & R-1210, respectively) by the Ministry of Economic Affairs, Taiwan 17

19. III. Results and discussion（5/15） RemainedNonhazardous Table 5. Heavy metals of concern in EAF dust, EAF slag, and LF slag (after melting of MIFA obtained from MSWI-1) leached by TCLP RemainedHazardous 18

20. III. Results and discussion（6/15） Table 6. Heavy metals of concern in EAF dust, EAF slag, and LF slag (after melting of MIFA obtained from MSWI-2) leached by TCLP 19

21. III. Results and discussion（7/15） Table 7. Chemical compositions of EAF dust, EAF slag, and LF slag (EAF steelmaking operations w/ melting of MIFA obtained from MSWI-1) 20

22. III. Results and discussion（8/15） Occurrence and fate of MIFA after melting in a steelmaking EAF • According to World Steel Association (2014), on average the production of one ton of steel results in 200 kg by-products including slags (that represent about 90 wt% of the total by-products), dusts, sludges, and other materials in EAF steelmaking operations. • In Taiwan, generally, about 20-25 kg of dust and 150-200 kg of slags (roughly 85 wt% oxidized slag plus 15 wt% reduced slag) would be generated per metric ton of carbon steel produced in EAF steelmaking operations. 21

23. III. Results and discussion（9/15） Occurrence and fate of MIFA after melting in a steelmaking EAF • When EAF steelmaking operations in conjunction with melting of MIFA (up to 3.77 wt% of scrap charge) was practiced, based on the actual statistics provided by the EAF steel mini-mill it was estimated that on average an increase of 1 wt% of MIFA injected would yield an increase of 2.76 kg of EAF dust and 8.93 kg of (oxidized plus reduced) slags per metric ton of steel billets produced. 22

24. III. Results and discussion（10/15） Occurrence and fate of MIFA after melting in a steelmaking EAF • Presently, there is no solid evidence to show the whereabouts of MIFA injected and melted in steelmaking EAF. • But a rough estimate is that at least 80 wt% of injected MIFA would end up in EAF slag and LF slag and the remainder becomes a fraction of EAF dust. • While concerning the occurrence and fate of MIFA after melting in a steelmaking EAF, the relevant legal considerations must not be ignored as well. 24

25. III. Results and discussion（11/15） Recycling of EAF dust • Although EAF dust is categorized as a hazardous waste in many countries including Taiwan, however, carbon steelmaking EAF roughly contains 11.12-26.9 wt% of zinc(Nyirenda, 1991). Often, zinc would form zinc oxide (ZnO) and zinc ferrite (ZnFe2O4) in EAF dust (Machado et al., 2006). • Globally, the pyrometallurgical Waelz process is the most often applied technology for the recycling of EAF dust. • Taiwan Steel Union (Changhua, Taiwan): using the Waelz kiln process to recover crude ZnO • Katec Creative Resources Corporation (Taoyuan, Taiwan): using EAF melting technology supplied by JFE Steel in Japan to generate crude ZnO, slag, and iron-nickel-chromium alloys 25

26. III. Results and discussion（12/15） The Typical Waelz Kiln Process Process temperatures are in the range of 1000–1150 °C, waste gas temperatures approx. 1200 °C. (Source: Global Steel Dust) 26

27. III. Results and discussion（13/15） Recycling of slags from EAF steelmaking • According to World Steel Association (2014), approximately 50% of the recovered steelmaking slags (including EAF operations) is used primarily for road construction (e.g., as an aggregate in bituminous pavements or as a binding agent in base courses). Nonetheless, some barriers for the use of steel slags exist. One of the main barriers for construction applications is their high content of free lime in steelmaking slags. • In recent years new technologies have been expanded to improve the slags recovery and use in different fields of application, such as in agriculture, allowing to reduce the amount of slags landfilled and to preserve natural resources. 27

28. III. Results and discussion（14/15） Recycling of slags from EAF steelmaking • Regulations concerning the recycling of steel slags have been enacted in many countries around the world. But several laws and regulations, including the Kyoto Protocol, the Reference Document of Best Available Techniques, Harmonization Committees TC 351 Dangerous Substances and TC 154 Aggregates, the REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) directive, are also concerned about the use of slag (Branca and Colla, 2012). • In Taiwan, the use of steel slags resulted from EAF operations is regulated by “Governance Guidelines for Industrial Waste Recycling (Revised on January 9, 2015)” promulgated by Ministry of Economic Affairs(Taiwan MOEA, 2015). 28

29. III. Results and discussion（15/15） Recycling of slags from EAF steelmaking (in Taiwan) • EAF slag (oxidized slag) can be used as the raw material for cement products, as the raw material for aggregate in bituminous pavements and base courses, as the raw material for aggregate in non-structural concrete, etc. But EAF slag has to be subjected to the following pretreatments before it is used: crushing, magnetic separation, and sieving. • LF slag (reduced slag) can be used in a variety of applications similar to that of oxidized slag with the following restrictions: Except for the use as the raw material for cement, LF slag has to be stabilized before use and the stabilized LF slag has to be subjected to CNS 15311 expansion test to determine whether excessive expansion occurs. For stabilized LF slag to be recyclable in Taiwan, the development of expansion should not be greater than 0.5% at seven days when tested using CNS 15311-2010. 29

30. IV. Conclusionsand perspectives（1/2） • Regulations and control measures for the use of steelmaking by-products are available in many countries over the worldincluding Taiwan. • In addition, several technologies have been employed in Taiwan for full-scale recycling of steelmaking by-products including EAF dust, EAF slag, and LF slag. • A great percentage of EAF dust are recycled to produce crude ZnO, whereas oxidized slag and reduced slag generated by EAF steelmaking operations are primarily used in different manner for road construction. 30

31. IV. Conclusionsand perspectives（2/2） • “Melting MIFA while EAF steelmaking” technology employed in this work has been justified to be an eco-friendly treatment technology for municipal incinerator fly ash. • By doing so, MIFA can be completely recycled via recycling of EAF dust and (oxidized plus reduced) slags. As a result, MIFA is no longer needs to be solidified/stabilized and landfilled in a way presently practiced in Taiwan and perhaps other countries. Thus, “zero waste” of MIFA becomes achievable at least in Taiwan. • It is the primary author’s dream that “Melting MIFA while EAF steelmaking” technology would be adopted and implemented for the disposal of MIFA all over the world. 31

32. Acknowledgments • Many thanks go to: (1) Coworkers at the EAF steelmaking plant participated in this work; (2) Taiwan EPA and local municipal solid waste incineration plants for providing fly ash; and (3) Ministry of Science and Technology (formerly known as NSC), Taiwan and Ministry of Economic Affairs, Taiwan for the research grants. 32

33. Campus of Thank you for your attention! 33