Fly ash treatment in Japan and the new oxygen-enriched WTE in Sendai

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1 Fly ash treatment in Japan and the new oxygen-enriched WTE in Sendai T.Nakamura Institute of Multidisciplinary Research for Advanced Materials, Tohoku University

2 Location of Sendai City and Tohoku University Sendai City is called Capital of Forest

3 OUT LINE Introduction The new oxygen-enriched WTE in Sendai Fly Ash Treatment in JAPAN New Technology for Fly Ash Treatment Conclusions

4 The Flowchart of Municipal Solid Waste Treatment Direct Landfill (5,700) Municipal Solid Waste (50,000) (38,000) Incineration (39,400) (1,400) Other Treatments (6,100) Fly Ash Bottom Ash (1,500) (4,500) Treatments Recycle (2,700) Residue (2,000) Landfill (13,700) Unit of ( ) : 1,000 tons per year Requirements priority of the Japanese government are 1Making fly ash harmless 2Reducing the quantity of landfill WTERT 2005 Fall Meeting at Columbia University

5 Decrease Trend of Landfill Sites Landfill Sites Years

6 OUT LINE Introduction The new oxygen-enriched WTE in Sendai Fly Ash Treatment in JAPAN New Technology for Fly Ash Treatment Conclusions

7 Outline of the Refuse Incineration Plant in Matsumori Stoker Furnace Maximum temperature : CO gas content : >100 ppm Boiler Burner Bag filter temperature >150 Gas cooling tower Amount of solid particles: > 10mg/m 3 Dioxins content: > 0.01 Teq/m3 Mercury Content : >0.05mg/m3 Re-heater OXYGEN Ash Extractor Fly ash re-melting Furnace De-Nox catalytic reactor Stack Air blower

8 : Normal Operation :O2 enriched Operation 100 Relative rate of flue gas Flue gas rate 35% decrease Flue gas rate after Bag filter 25% decrease Relative comparison of flue gas flow rate

9 : Normal Operation : O2 enriched Operation Relative concentration ( %) CO NOx More than 20% reduction of CO while 10% reduction of NOx

10 Temperature ( ) Normal Operation O2 enriched Operation Furnace temperature increases about 150 for oxygen enriched operation

11 Dust Concentration (g/nm 3-12% O 2 ) :Normal operation :O2 enriched Operation Air amount [UGA+O 2 ] (Nm 3 /h) Amount of Fly ash needing special treatment before being disposed of reduces as primary air flow rate decreases through oxygen enrichment

12 0.04 Dioxins Content (ng-teq/nm 3 ) Regulation: 0.05ngTEQ/Nm Normal Operation O2 enriched Operation Dioxins concentration reduces to ¼ for oxygen enriched operation

13 OUT LINE Introduction The new oxygen-enriched WTE in Sendai Fly Ash Treatment in JAPAN New Technology for Fly Ash Treatment Conclusions

14 The Treatments of Fly Ash by Notification (Detoxification Treatment) Melting and Solidification Solidification with Cement Notified in April, 1995 Stabilization by Chemical Agents The long-term stability is questionable. Not recyclable Our Technology Stabilization by Acid or Solvents Notified in January, 2000 Volatilization and Detoxification by Roasting

15 Treatment Process for Fly Ash notified in Japan Process (a) Melting (b) Sintering (c) Fixation by Cement (d) Treatment by Chelate Agent (e) Leaching by Acid CONTENT Fly ash is melted by a melting facility and solidify to slag. Slag and secondary dust have to be treated by following processes (c),(d) and (e) Fly ash is sintered by a sintering facility to obtain the stable sintered block. Sintered block and secondary dust have to be treated by following processes (c),(d) and (e) Fly ash is solidified with a sufficient amount of cement and aged not to elute heavy metals Fly ash is mixed with chelate agents to stabilize heavy metals and keep them to well controlled landfill place. Fly ash is leached by acids or other solvent to remove heavy metals from it and heavy metals have to be recovered from the leach ant and deposit of heave metals have to treated in smelter.

16 Recent Targets of Fly Ash Treatment Technology Detoxification -Thorough removal of Heavy Metals -Reliable stabilization of Residual Metals -Decomposition of PCDDs Recycling -Utilization of gangue components -Recovering Zn as Smelting Resources

17 Environmental Quality Standards for Soil Pollution Substance cadmium Target level of soil quality examined through leaching test 0.01 mg/l or less in sample solution lead chromium (VI) 0.01 mg/l or less in sample solution 0.05 mg/l or less in sample solution arsenic selenium 0.01 mg/l or less in sample solution 0.01 mg/l or less in sample solution (partly extracted)

18 Basic Flow Chart of Direct Melting System

19 Electrode Fly Ash Wet Treatment Molten Fly Ash Recovery of Heavy Metal 1200~1400 o C Slag Fig. Fly ash melting furnace (Electric furnace).

20 Comparison of Fly Ash Treatment Processes and their Characteristics Process Cost Energy Consumpti on Recovery of Heavy Metals Log term stability others Melting Generation of secondary fly ash Sintering Reuse sintering block of Fixation by Cement Limitation of amount Treatment by Chelate Agent (?) Leaching by Acid Stability Chelate agent of High cost and reuse of final deposit

21 <Cl elimination> Other Materials EAF Dust Power Plant Fly Ash Raw Materials Coal Silica Steam Sell Out Binder MF Boiler Gas Cooler Bag Filter Leaching Tank Dryer Rod Mill Thickener Slag Removal of Halogen Briquette Machine Filter Press Aging Bins Filter Press Crude Zinc Oxide Fly Ash Treatment Process by MF furnace

22 water wall tube by-pass duct coking zone conveyor hot air boiler tuyere settler smelting zone Conceptual Figure of MF Furnace

23 Contribution of Non-ferrous Industry to Fly Ash Treatments (1) Miike Smelting Corporation Fly ash is rinsed by water and residue is treated by MF furnace to recover crude ZnO. (2) Mitsubishi Materials Corporation Naoshima Smelting Fly ash is rinsed by water and residue is treated by lead furnace. (2) Kowa Seiko Corporation Fly ash is treated by Kowa process to recover nonferrous metals. Principle of Kowa process is chlorination roasting using a rotary kiln. (3) Sumitomo Metals and Mining Corporation Fly ash is treated by a sintering process with a rotary kiln. They produce artificial rock materials and secondary fly ash which is suitable for resource of Zn and Pb.

24 OUT LINE Introduction The new oxygen-enriched WTE in Sendai Fly Ash Treatment in JAPAN New Technology for Fly Ash Treatment Conclusions

25 From Melting Process to Sintering Process Melting process needs high energy Sintering process produces more valuable by-products like Pellets for Construction materials and secondary fly ash from sintering process is more suitable for resources for Zn and Pb smelting.

26 Flow Sheet of The Fly Ash Treatment Process LPG Burner Fly Ash Mixing & Grinding Pellet Forming Green Pellets Drying Flux Waste Gas & 2 nd Fly Ash Rotary Kiln Dried Green Pellets Roasted (Sintered) Pellets Water Cooler Aggregate Bag Filter 2 nd Fly Ash Waste Gas Capacity:100kg/h Construction Site Hydrometallurgy Pb,Zn and Cd Salt & Effluent WTERT 2005 Fall Meeting at Columbia University Smelter

27 Rotary Kiln Inner Diameter : 900 mmφ Length : 12 ml

28 Composition of Fly Ash Used in Experiments Contents(%) A-City B-City1 B-City2 SiO Al 2 O Fe 2 O CaO Na K Cl SO Pb Zn Cd T-Cr As Hg < Se C

29 Schematic Diagram of Kiln Off Gas Treatment System ,000mm LNG(LPG) Burner Feeder Gas Flow >1000 1,200mm Dry Green Pellets Pellets Flow Dam Roasted Pellets (Aggregate)

30 Residual Amount Change of Elementals in Pellets Through Rotary Kiln WTERT 2005 Fall Meeting at Columbia University Na K Pb Zn Cd Cl Temp Residual Amount(g/100g Green Pellet) Temperature( ) Distance from Kiln End (m) 500

31 Residual Amount of Pb, Cd in Roasted Pellet Residual Percentage (%) Planned new standard Pb, Cd : <150ppm Pb current standard : <600ppm Cd current standard : <9ppm Pb Cd Runs Residual metals could be reduced at any conditions.

32 Results of TCLP and Estimation of Pb stabilization Sample No. Elution of Pb (mg/l ) USA(TCLP) (note 1) (a) Residual Amount (%) Lead Concentration when all residual is dissolved. (mg/l)(note 2) (b) Stabilization rate of residual Pb 1-(a)/(b) F F L L (note 1) TCLP:Toxicity Characteristic Leaching Procedure (note 2) The estimated concentration when residual Pb dissolved all the quantity on the dissolution condition (100g is dissolved in 2000m/ l ) of TCLP. Under the proper condition, 95% of residual Pb can be stable.

33 Relationship between Compressive Strength of Sintered Pellet and (Na+K)Concentration in Green Pellet Compressive Strength (kgf) WTERT 2005 Fall Meeting at Columbia University (Na+K) Concentration in Green Pellet (%)

34 Composition and Strength of Pellets (Na 2 O include K 2 O)

35 Dioxins WTERT 2005 Fall Meeting at Columbia University Schematic Diagram of The Waste Gas Treatment Kiln end hood DXNs concentration (ng-teq/nm 3 ) Water spray gas cooler Dioxins concentrations in the waste gas Exit of the kiln Sample-1 Sample-2 Exit of the gas cooler Exit of the bag filter Exit of the scrubber Exit of the AC-tower Bag filter Scrubber With AC-adsorption, Activated carbon adsorption tower the new Japanese guideline can be satisfied; <0.1 ng-teq/nm 3.

36 Composition of Secondary Fly Ash Elements Contents(%) 2nd. Fly Ash-1 2nd. Fly Ash-2 Zn Pb Fe Cu Cd Cr Hg < < Sb Cl

37 Flow Sheet of Secondary Fly Ash Treatment Test Secondary Fly Ash Water Leaching ph=4 Filtration Filtrate Filter Cake Neutralization ph=7 Dehydration Filtration Calcination Filtrate Filter Cake PbO Dehydration Smelter Cleaning Solution Salt Treatment Drain Calcination Smelter ZnO

38 Composition of Recoveries (Metal Containing Materials) WTERT 2005 Fall Meeting at Columbia University Zn- Concentrated Recovery Contents(%) Pb- Concentrated Recovery Elements Zn Pb Fe Cu Cd 0.12 <0.01 Cr Hg < < K Na Sb Sn < Cl F Ca Si Al

39 Use Development Samples Decollation fence block Car tire block Curbstone block Sub-base Soil improvement material Filter medium

40 CONCLUSIONS 1.Detoxification and recycling of heavy metals are strongly required with low energy consumption. 2. Sintering Process will be next main process for fly ash treatment in Japan. 3. Secondary Fly ash are finally treated in primary non-ferrous smelter

41 Thank you for your kind attention Welcome to Sendai and TOHOKU University