HIGH VOLUME FLY ASH CEMENT AN ECONOMICAL APROACH

HIGH VOLUME FLY ASH CEMENT AN ECONOMICAL APROACH FOR REDUCING THE POLLUTION IMPACT OF THERMAL POWER PLANT BY- PRODUCTS IN THE OHRID AREA Arjan Korpa; Kledi Xhaxhiu; Altin Mele; Bujar Seiti; Erjon Spahiu Vth International Scientific Conference on Water, Climate and Environment BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012

By-products of coal burning

Coal fly ash - FA Worldwide FA production estimated at around 600 million TPA. FA production in Macedonia more than 2. 5 million TPA. Total FA generated since 1970 more than 50 million tons. Almost all of the fly ash produced is disposed of in landfills at significant cost. Fly ash creates massive pollution to the environment! As fly ash piles up, the challenge for safe disposal rises! Location of the two coal power plants in Macedonia

Fly ash generation and utilization - Europe FGD – Flue gas desulphurization product SDA – Semi dry absorption product FBC – Fluidized bed combustion product Source: ECOBA – European Coal Combustion Products Association

Hazardous waste - fly ash According to the US Environmental Protection Agency (USEPA): Hazardous waste - materials containing specific heavy elements which exceed regulated concentration levels. Heavy elements are extremely toxic - they present danger to the whole ecosystem. Dump sites/pond fly ash - can leak their toxic cargo into rivers or public water systems by leaching and migration up to hundred kilometers. A number of incidences have been reported in the past, where leachate had contaminated the groundwater!

Dumped coal fly ash Production in Macedonia more than 2. 5 million TPA.

Macedonian fly ashes – Toxic elements Trace elements enriched in waste products Bitola FA Nb, Mn, P, Mo, Ti Oslomej FA Nb, Sb, Hg, Y, Ti, Zr, Sc, Cu, Mn, V, Zn, Th, Ni, Ga, Co, Pb exceeds Clarke concentration by more than two times*! Some of these elements may contribute to environmental and health problems in the area! *The concentration of an element in a mineral or rock relative to its crustal abundance.

Fly ash radioactivity/Macedonian fly ash Fly ash concentration* 100% 90% 80% 70% 60% 50% Activity concentration index (I) 1. 34 1. 21 1. 1 0. 94 0. 81 0. 67 Activity concentration index limit (Imax) 1. 0 1. 0 Compliance No No No Yes Yes where CTh, CRa and CK are the activity concentrations of 232 Th, 226 Ra and 40 K in the final product, expressed in Bq/kg. European Commission: Radiation Protection Report (RP-112, EC), Luxembourg, (1999). *- Concentration in the final product

Fly ash can be upgraded to a valuable raw material with proper quality control Fly ash Cement

High Volume Fly Ash (HVFA) cement Current practice: Silicious fly ash in cement can be used up to 30% New approach: Silicious fly ash in cement up to 50% (a real challenge!) Constituents [%] M% Clinker Gypsum 50 -70 Activator (AC) Fly ash 30 – 50

Physical properties of the HVFA cements Compressive strength Sample code Grinding time [min] 2 days [MPa] 7 days [MPa] 28 days [MPa] Ref. cem M 0 FAM 1 FAM 2 FAM 3 FAM 4 FAM 5 FAM 6 FAM 7 FAM 8 FAM 9 FAM 10 FAM 11 FAM 12 FAM 13 FAM 14 FAM 15 FAM 16 FAM 17 25 25 25 25 25 26. 5 7. 6 10. 8 11. 2 15. 7 17. 9 18. 7 20. 3 17. 1 18. 3 16. 2 19. 9 17. 4 16. 2 15. 0 19. 0 21. 2 24. 7 26. 5 41. 2 19. 7 26. 6 28. 4 36. 8 40. 8 41. 7 42. 1 39. 9 38. 5 33. 7 40. 4 37. 4 35. 2 35. 5 38. 8 45. 7 48. 7 47. 7 56. 5 29. 8 46. 6 48. 0 52. 2 57. 3 54. 7 53. 7 56. 0 57. 1 52. 8 54. 0 53. 8 50. 8 54. 3 56. 8 57. 5 58. 8 58. 5 Initial setting time [min] 170 340 230 115 185 260 120 100 195 210 170 80 160 185 140 130 175 180 Fineness ROS 90µm [%] 4. 8 5. 6 5. 9 4. 3 4. 9 4. 2 3. 8 3. 7 4. 4 4. 1 5. 2 5. 5 6. 5 5. 1 7. 0 6. 8 5. 3 5. 0 Expansion [mm] Code of the Activating compound (AC) 0. 1 0. 2 0. 1 0. 1 SV ML S 300 SV S 300 IP SV SV SV S 300 SV FM FM FM SV SV SV

Investment required for industrial production of HVFA through ball mills Air Slide Truck Unloading Mill Inlet Silo Vertical Screw Weigh Feeder Cement Mill

Economic Evaluation – Cost of New Mix Designs/HVFA Cem I 42. 5 R Current mix New mix 1 Composition New mix 2 Material Var cost of materials (euro/t) Composition Var cost of materials (euro/t) Clinker 26. 59 95% 25. 26 75% 19. 94 50% 13. 29 Fly ash 22. 95* 0% 0. 00 20% 4. 59 45% 10. 33 Gypsum 8. 99 5% 0. 45 Cement total 25. 71 24. 98 Cost savings 0 -0. 73 Var cost of materials (euro/t) Cost savings for 1. 3 million TPA cement = 1. 64 x 1 300 000 = 2 132 000 euro * Variable cost of fly ash comprises also the transport cost within 200 km distance 24. 07 -1. 64

Conclusions Ø What is considered ”waste” for a human activity sector appears to be a highly valuable raw material for another activity. Ø The economical solution to waste handling - incorporation into construction products. Ø Materials bonded with cement tend to have significantly lower leaching abilities. Ø Hence there is no significant influence of hazardous elements on the surrounding waters due to leaching.

Thank You for your attention!