Optimum Utilization of Fly ash by Power Plants Technologies for Utilization of Fly ash at NTPC-NETRA

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1 Optimum Utilization of Fly ash by Power Plants Technologies for Utilization of Fly ash at NTPC- By: Dr. M. Malik, AGM () Dr. N. K. Soni, Dy. Manager ()

2 NTPC NTPC is the largest power producer with approx MW of installed capacity with 60% alone based on coal. Ash generation approx 60 Million tonnes per annum Ash Utilization is around 60% Presently Fly ash is being utilized in Cement industries Mine filling Roads/Rail Embankment & others brick/block/tile manufacturing, land development, ash pond dyke walls,

3 Forecast for Cement and aggregates requirement Global Cement: World demand for cement is projected to rise 4.5% per year to 5.2 billion metric tons in 2019 Construction aggregates According to the study, titled World Construction Aggregates, the worldwide market for construction aggregates is projected to advance to more than 51 billion metric tons in 2019, recording growth comparable to that of the period India Cement: India is the second largest cement producer in the world Industry to grow at 5-6 per cent CAGR between FY17 FY20. (CAGR - Compound Annual Growth Rate) Cement production capacity of nearly 425 million tonnes, as of September 2017 and expected to reach 550 million tonnes by Construction aggregates: Demand in India is expected to rise at a 7.7 percent annual pace to 1.6 billion metric tons in In 2015 leadership in Asia changed hands, with China falling back in terms of global investments in this sector, achieving only +4% growth while India posted growth of 5.3% over the year.

4 Technologies for Utilization of fly ash 1. Geopolymeric cement Road Construction Tetrapod construction 2. Coarse aggregates Light weight coarse aggregates 3. Fine aggregates Bottom ash as replacement of fine aggregates Fly ash to Geopolymeric sand 4. High volume use of Fly ash in PPC

5 Geopolymer Concrete (GPC) Road : ROAD CONSTRUCTED AT CBRI Roorkee: Apr Meter x 3.0 Meter (single lane)at CBRI Roorkee 40 Mpa Compressive strength ROAD CONTRUCTED AT NTPC-DADRI: Sep Meter x 6.5 Meter (Double lane) at NTPC-Dadri

6 Bulk Fly Ash utilization Geo-polymer cement free concrete road 40 Mpa as per IRC44 guidelines 50 m X 3 m Road Single Lane Geo-polymer concrete road laid at CBRI Roorkee 100 m X 6.5 m Road Double Lane Geo-polymer concrete road at Steel yard NTPC DADRI

7 Geopolymeric Cement Technology: CEMENT FLYASH GGBS Activator (NaOH + Sodium Silicate) Benefits: Cement in conventional concrete replaced with Zero cement concrete Low Curing Time 2 days against 7 days (50% strength) No water for curing Nil CO2 technology Indian Road Congress Accreditation ( on )

8 Geopolymer Concrete (GPC) Road vs Cement concrete Road NO CEMENT - Developed Fly ash based green concrete road without cement NO WATER CURING - Construction of fly ash based GPC road without water curing. High early compressive strength Strength achieved in 7 days vs 28 days for Concrete road. Ensures bulk utilisation of Fly Ash Negligible CO2 emission vs high CO2 emission (0.8 tonne/tonne of OPC) in cement Negligible shrinkage No cracks observed in the GPC road Low permeability Good durability in aggressive environment compared to OPC Rapid, controllable setting and hardening properties Low thermal conductivity Good fire resistance (stable even at 800 o C)

9 Geopolymer vs Cement Property Cement Geopolymer Energy requirement 3430 MJ/tonne 990 MJ/tonne CO 2 emission 1 tonne/tonne tonne/tonne Phase C-S-H N-A-S-H Curing Water Near ambient temperature. Workability Handled up to 30 minutes. Handled up to 2 hours. Fire resistance Spalling at higher temperature. Stable even at a excess temperature of 800 o C. Thermal conductivity W/m/K W/m/K Chemical resistance (acids and salts) Low High Source: Davidovits, Geopolymer Institute, France.

10 Constituents of Geo-polymer Concrete Raw materials Coarse aggregate Admixture (Specialty chemicals) Fine aggregate(sand) Fly ash from power plant Activators

11 Plan & cross section for road at DADRI Tied concrete shoulder, 50 cm Pavement Quality Concrete (280 mm thick, 28 day flexural strength, 55 kg/cm 2 ) 2.0 % G.L 125µ Separation Membrane 150 mm Thick DLC, extended on both sides 50 cm beyond PQC mm 2 ± 1 Initial 3-4 mm wide cut 90 mm deep PQC, 280 mm thick Widening Groove (Sealing detail A ) MS round Dowel bar, Dia:36 mm, Length: 500 mm, Spacing:300 mm c/c 300 mm long plastic sheathing, 0.5 mm thick 15 mm Compressible debonding strip A -Sealing Detail of joint Polysulphide/Poly urethene/silicon Sealant 5 mm Soft rope or back-up rod Initial 3-4 mm wide groove Fig.: CONTRACTION JOINT

12 Comparison between geopolymer concrete and acceptable criteria of IRC 15 Test Acceptable criteria (IRC: ) Geopolymer concrete Compressive strength (MPa) (Rebound hammer) Flexural Strength (MPa) (using equation) Workability 40 ± 10 mm mm Degree of compaction No honey combing in the side surface after form removal Uniformity (30 % strength reduction through RH) Properly compacted Uniform compaction Abrasion resistance Min. 45 MPa concrete 49 (Rebound hammer) Durability No ASR No ASR Riding quality Good surface finish Satisfactory Surface texture No laitance roll appear No skidding Criteria for cracks Hair line & discrete crack No cracks Traffic opening Min. 32 MPa MPa

13 Geo-polymer-Basics Due to use of waste product and use of less CO2 emission reason Geopolymers are called GREEN MATERIALS. They are based on alumino-silicate raw materials derived from industrial wastes. Ordinary Portland Cement Geopolymeric Cement 5CaCO 3 +2SiO 2 Clinker Phases C-S-H + Ca(OH) 2 3CaO.SiO 2 +2CaO. SiO 2 +5CO ºC Hydration (curing with water) Al 2 O 3 +SiO 2 in raw material 20-80ºC +alkali silicate solution -Si-O-Al-O- Noncuring Alumino silicate 3D framework Geopolymer is a repeated unit of sialate monomer Mn [-( SiO 2 )z-al-o]n.wh 2 O

14 Constituents of Geo-polymer Concrete Raw materials Fly ash from power plant Activators (NaOH etc.) Fine aggregate(sand) Coarse aggregate Admixture (Specialty chemicals)

15 World s 1 st building Queensland s University GCI building. Success Stories of Geopolymer Concrete World s 1 st commercial production run 2500 T by ROCLA Australia UTAH State Capitol Building Path ways Precast slabs

16 Fly ash Geopolymeric tetrapods Salient Details: Replacement of cement and sand in concrete with ash and coastal sand & sea water in concrete mixes. Terapods can be used for sea/river shore protection and for prevention of erosion of canal bed (canal scouring) instead of rock boulders Conservation of precious natural resource Benefit: Bulk Fly ash utilization for NTPC coastal stations Status & Time line: Demonstration of geo-polymer tetra pod at SIMHADRI completed Manufactured Tetrapods

17 Light Weight Aggregate (LWA) Plant at Sipat Conservation of precious natural resource Bulk fly ash utilization by replacement of coarse aggregates Fly ash is mixed with additive and coal and spherical pallets of 5-16 mm are made, then heat treated at above 1000 o C. Sintering technology Electric Ignition BIS Code: Cleared by sub-committee in Sept 17, Publication by May 18 Demo Plant: Capacity: 50,000 M3/Yr Foot Print: Plant: 1000 sq.m, Storage: 5000 sq.m 17

18 Light Weight Aggregate (LWA) Plant at Sipat 18

19 A Maharatna Company Process Flow Sheet Of SINTERED LWA PLANT 2-4% ADDITIVE 5-10% CARBON 85-90% FLY ASH WATER METERING METERING METERING METERING MIXING NODULISING PELLETIZING LWA SINTERING *Source: Presentation by SANSAM technologies & engg pvt.ltd DEDUSTING

20 A Maharatna Company FA-LWA Pellets GREEN PELLETS SINTERED PELLETS (Heat treated above 900 o C) *Source: Presentation by SANSAM technologies & engg pvt.ltd

21 Process development for conversion of Fly/Pond ash to Sand Ever increasing demand of natural sand Increasing cost of natural sand Availability of natural sand for construction industry, a cause of concern due to environmental issues and legal aspects in present days. Illegal activities of sand Depletion of natural sand from river causes change in the path of river and brings damage Fly ash to fine aggregates (Sand) through Geo-polymeric route Conservation of precious natural resource by replacement of river sand with synthetic sand Demonstration of technology by setting up a pilot plant for manufacture of sand.

22 Use of Bottom Ash as replacement of sand in cement concrete Conservation of precious natural resource Casting & Testing of Concrete samples as per relevant standards Replacement of conventional sand by bottom ash in concrete mixes. Data to be used for formation of BIS Code Data sent to BIS.

23 Study on high volume use of Fly Ash Cement Concrete Study will pave the way for increasing blending of fly ash in Cement up to 50% from the present 35%. Study to be conducted at 4 Cement plants with ash from nearby NTPC plants Formation of BIS code with large Fly ash utilization in PPC

24 Moving towards All Flyash Concrete