Valorization of Industrial and Agricultural Wastes into Ceramics

1. Πράξη «ΑΡΧΙΜΗΔΗΣ ΙΙΙ – Ενίσχυση Ερευνητικών Ομάδων στο ΤΕΙ Δυτικής Μακεδονίας» του Ε.Π. «Εκπαίδευση και δια Βίου Μάθηση» MIS 383583 Υποέργο 3 Valorization of industrial and agricultural wastes into ceramics Vayos G. Karayannis Scientific Coordinator Department of Environmental Engineering Technological Education Institute of Western Macedonia Kozani, Greece Assoc. Professor Vayos G. Karayannis E-mail: vkarayan@teiwm.gr, Tel: +302461068022-3; +306976447511

2. Acknowledgment This research has been co-financed: by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - - Research Funding Program: ARCHIMEDES III: Investing in knowledge society through the European Social Fund

3. Research Team Vayos Karayannis, Asimina Domopoulou, Evangelia Lakioti, Nikolaos Taousanidis Τechnological Education Institute of Western Macedonia, Kozani, Greece Dept. of Environmental Engineering / Lab. of Waste Management Technologies Dept. of Mechanical Engineering and Industrial Design Angeliki Moutsatsou, Eleni Katsika, Christina-Amalia Drossou National Technical University of Athens, Greece School of Chemical Engineering George Papapolymerou, Xenofon Spiliotis, Konstantinos Ntampegliotis Τechnological Education Institute of Thessaly, Larissa, Greece Dept. of Civil Engineering Nikolaos Koukouzas Centre for Research and Technology Hellas, Athens, Greece Process and Energy Resources Institute Petros Samaras, Efthymios Papastergiadis Alexander Technological Education Institute of Thessaloniki, Greece Dept. of Food Technology

4. Introduction • The valorization of industrial solid residuesas useful secondary resources in the manufacturing of value-added products: - can contribute to environmental protection, resources conservation & cost reduction - is strongly encouraged by current E.U. environmental policies, with the aim of turning waste from one industry into useful feedstock for another one, towards industrial symbiosisand ample coordination • Limited quantities of coal/lignite-fired power stationandsteel industry by-products are currently used as raw materials for cement and concrete manufacture • Production of ceramics: Possible further beneficial use in the synthesis of ceramics - Industrial residues: substitutes for clayey raw materials in ceramic manufacturing mainly due to their useful silica and alumina and other oxides content - Fly ash being mainly composed of hollow spheres (cenospheres), it can promote: a) pore-forming in the bulk of the bricks to improve thermal insulation b) thorough firing to attain energy savings - Fly ash can be selected to give special colors or properties not possible from clays - Potential to be an important application of industrial residues, given the large quantities of raw materials needed for ceramic production - Potential contribution to reducing CO2 emissions originating from carbonates decomposition during clay firing - Improved resource efficiency and cost savings by the recycling of a largely industrial by-product as a secondary resource - Solving problems associated with the environmental impact of ash disposal - Sustainable production of eco-friendly ceramics towards a circular economy

5. In the current research • The recycling / valorizationof several industrial and agricultural solid waste by-products • as substitute raw materials in the production of value-added ceramics was studied. • Specifically: • - flyash and bottomash from lignite-fed power stations of: • * Western Macedonia (high-Ca) • * Megalopolis (siliceous) • - fly ash from circulating fluidized bed (CFB) combustion pilot-plant • - steel industry by-products • - glass cullet • - olive kernel ash • Ceramic specimens were fabricated employing alternative procedures: • Formation: - Cold Pressing / Compaction • - Extrusion • Consolidation: - Conventional sintering • - “Two-step” sintering • - Microwave sintering • The microstructure and physico-mechanical properties of the ceramic specimens • were thoroughly investigated • It was evaluated whether the chemical, mineralogical and morphological characteristics • of the powdery by-products examined render them suitable starting materials for ceramics

6. Novelty • Development of ceramics starting 100% from industrial and agricultural solid by-products • Emphasis: • - Novel utilization oflignite fly and bottomashes from Western Macedonia power stations • - Investigation of the effect of intrinsic characteristics of these by-products. and especially: • * CaO content that act as a natural binder • * SiO2 reactivity associated with its different structures • Use of alternativeformation procedures of ceramic specimens for comparison reasons: • - Cold Pressing / Compaction • - Extrusion • Application of innovative densification/consolidation processesto fly and bottom ashes: • - “Two-step” sintering • - Microwave sintering • Utilization of CFB (Circulating Fluidized Bed) combustion fly ash • as 100% the raw material in ceramics fabrication, taking into consideration that: • - CFB combustion is an advanced and rapidly growing technology for cleaner power generation • - steadily increasing amounts of such fly ash are globally produced • Combined/synergistic use of industrial and agricultural by-products for improved efficiency • Novel valorization of olive kernel ash, an agricultural by-product of increasing interest, • in ceramic applications.

7. Preparation of specimens Firing / Sintering Microwave Sintering Uniaxial Cold Pressing - Compaction

8. Characterization of specimens Density (Archimedes method) Vickers Microhardness

9. Secondary resources: industrial solid by-products Base raw materials: Clays typically used by the ceramic industry High-Ca fly ash : Lignite thermal power station (Region of Western Macedonia): Highly calcareous (> 25 wt.% CaO) → Class-C FA (ASTM C618) Siliceous fly ash : - Megalopolis power station - Lignite: High ash & high moisture - Strongly siliceous ash (51.26 % SiO2) - Lower amounts of Ca-bearing species: 11.82 wt.% CaO (only 0.95 wt.% free)

10. Compacted ceramics 100% from high-Ca fly ash & bottom ash • Experimental • - Compacted ceramics 100% from high-Ca lignite fly & bottom ashes (Western Macedonia, Greece) • - Simple powder processing techniques (P/M): Cold pressing followed by sintering (1100oC) • - The addition of H2O and CaO tested in order to improve compaction efficiency Results (a) (a) (c) (a) (b) (d) (b) (b) SEM micrographsof sintered pellets: FA/BA:1/1+3%Η2Ο+1%CaO (a); FA (b), FA+10%CaO+3%H2O (c); FA/BA:3/1+3%Η2Ο+1%CaO (d) Sintered ash pellets (d: 1.3 cm): FA (a); FA+3wt.%CaO+1wt.%H2O (b) XRD patterns of sintered pellets: FA (a); FA/BA:1/1 (wt.) (b) Conclusions The ceramics obtained: acceptable microstructure, and negligible leachability. Porosity varies with the relative FA/BA composition, and therefore, can be tailored accordingly: importance for several applications, including heat insulation behavior development.

11. “Two-step” sintering method for transformation ofhigh-Ca lignite fly ash and bottom ash into ceramics

12. Microwave sintering for transformation ofhigh-Ca lignite fly ash and bottom ash into ceramics Reasonably dense ceramic microstructures are achieved after sintering lignite flyand bottom ashes in a short period of time (30 min) at 1000°C using microwave energy. MW sintering causes noticeable changes in the amount of the mineralogical phases originally present in the ash mixtures. The ashparticle size and shape, the green density of the compacts and the sintering time influence the consolidation efficiency by microwave heating The high-Ca nature of fly ash does not hinder the synthesis of ceramics

14. Compacted ceramics 100% from CFB combustion fly ash • Circulating Fluidized bed combustion: • Continuously gains ground for environmentally-friendlier power production • CFB-fly ashes: Particular characteristics of CFB technology • → ashes possibly different from those generated in the conventional processes

15. Production of successfully densified and uniformlightweight ceramics, • mainly composed of siliceous ceramic phases • When higher densification is demanded → • the use of BA previously treated for residual C burnout should be preferred

16. Synergistic sintering of lignite fly ash & waste glass cullet for their valorization into ceramics Tsint for fly ash can be lowered (900oC, 2h) by the favorable effect (fluxing action) of glass cullet → leading to possible energy consumption reduction.

17. Synergistic sintering of lignite and olive kernel ashes for their valorization into ceramics

18. Preparation of extruded ceramic specimens:Pilot-plant simulation of industrial building brick manufacturing Extrusion of specimens Formation of plastic mass • Sintering – Final consolidation • of the extruded specimens • Drying in air for 24h • Drying in oven at 105oC for 48h • Firing in programmable furnace • up to 850, 950, 1050, 1150 oC As-extruded green specimens

19. Synergistic combination of industrial solid by-products into red ceramics • Combined-synergistic addition of power station fly ash with steel-making dust (5+5%wt.) • By appropriately adjusting the admixture composition, • the brick properties can be predicted & tailored to meet the needs for specific ceramic applications • The influence of Tfiring(especially:1150oC) on sintered ceramics properties is emphasized.

20. Reliability analysis of clay bricks incorporating industrial solid by-products • Critical factor (drawback) restricting wider use of brittle materials in various structural applications • Tendency to present a large and unpredictable variation in mechanical strength data. • Analysis of fracture data in ceramics by probabilistic theories • such as Weibull analysis in view of their utilization in design and manufacturing

21. Field study - Survey

22. CONCLUSIONS • Total (100%) or partialbeneficial substitution for clays (natural resources), which are normally demanded for the production of fired (red) ceramics, with industrial & agriculturalby-products is feasible → sustainable use of resources • The low cost of these largely available solid residues should also be taken into account. • Novel sintering processes, specifically microwave and “two-step” sintering were successfully applied and compared to conventional firing for the transformation of fly and bottom ashes into ceramic materials with advantages regarding energy savings or specific characteristics obtained. • Innovative synergistic combination of lignite fly ash with either steel-making dust, either waste glass cullet or olive kernel ash, into new ceramics shaped by two alternativeformation techniques, compaction or extrusion. • By appropriately adjusting the starting relative mixture composition, the ceramic microstructures and properties obtained can be predicted and tailored → to meet the needs for specific applications. • The physico-chemical, mineralogical & morphological characteristics of the by-products render them appropriate secondary resources for their valorization into red ceramics → to contribute to alleviating waste management problems. • Work still remainsto be done to set up full scale operations of potential commercial interest ….

23. Implementation possibilities – Benefits • The outcome of the current program can be important for the: - producing industries with regard to safe waste management - ceramic industry that seeks innovative, environmentally-friendly & low cost products → to maintain job positions, especially in economic crisis period. • The current research leadtothedevelopmentofnewscientificknowledge: - withregardtothedevelopmentofvalue-addedceramicmaterials - also respondingtocurrentenvironmentaldemandsforsafemanagement ofindustrialandagriculturalwaste by-products → thus, atleastpartially, contributingtoimprovinghealthandqualityoflife especiallyinareaswithenvironmentalissues. • Information, publicity & dissemination of the results in the society were strongly promoted • The interdisciplinary program, focusing on both environmental & materials science/engineering: - encouraged the mobility & cooperation among different educational & research institutions - with the potential for further broader coordination both in research and educational level.

24. Published work