Optimum Utilization of Fly ash by Power Plants –

Technologies for Utilization of Fly ash at NTPC-NETRA

By:Dr. M. Malik, AGM (NETRA)Dr. N. K. Soni, Dy. Manager (NETRA)

NETRA

NTPC

NTPC is the largest power producer with approx 50000+ 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 fillingRoads/Rail Embankment & othersbrick/block/tile manufacturing, land development, ash pond dyke walls,

Global –Cement: World demand for cement is projected to rise 4.5% per year to 5.2 billion metric tons in 2019

Construction aggregatesAccording 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 2009-2014 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 2025.

Construction aggregates: Demand in India is expected to rise at a 7.7 percent annual pace to 1.6 billion metric tons in 2011.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.

Forecast for Cement and aggregates requirement

NETRA

Technologies for Utilization of fly ashTechnologies 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

NETRA Geopolymer Concrete (GPC) Road :

ROAD CONSTRUCTED AT CBRI Roorkee: Apr’2017 41 Meter x 3.0 Meter (single lane)at CBRI Roorkee 40 Mpa Compressive strength

ROAD CONTRUCTED AT NTPC-DADRI: Sep’2017 100 Meter x 6.5 Meter (Double lane) at NTPC-Dadri

NETRA

Geo-polymer cement free concrete road40 Mpa as per IRC44 guidelines

Bulk Fly Ash utilization

Geo-polymer concrete road laid at CBRI Roorkee Geo-polymer concrete road at Steel yard NTPC DADRI

50 m X 3 m RoadSingle Lane

100 m X 6.5 m RoadDouble Lane

NETRA

Zero cement concrete

Low Curing Time – 2 days against 7 days (50%

strength)

No water for curing

Nil CO2 technology

Geopolymeric Cement

Indian Road Congress Accreditation( on 05.01.2018)

CEMENT FLYASH GGBSActivator

(NaOH + Sodium Silicate)

Cement in conventional concrete replaced with

Technology:

Benefits:

NETRA 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 oC)

NETRA

Geopolymer vs CementProperty Cement Geopolymer

Energy requirement 3430 MJ/tonne 990 MJ/tonne

CO2 emission 1 tonne/tonne 0.15-0.20 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 800o C.

Thermal conductivity 0.51-1.28 W/m/K 0.3-0.5 W/m/K

Chemical resistance(acids and salts)

Low High

Source: Davidovits, Geopolymer Institute, France.

NETRA Raw materials

Coarse aggregate

Fine aggregate(Sand)

Fly ash from power plantActivators

Admixture (Specialty chemicals)

Constituents of Geo-polymer Concrete

NETRA

Plan & cross section for road at DADRI

2.0 %

150 mm Thick DLC, extended on both sides 50 cm beyond PQC

125µ Separation Membrane

G.L

Pavement Quality Concrete (280 mm thick, 28 day flexural strength, 55 kg/cm2)

Tied concrete shoulder, 50 cm

300 mm long plastic sheathing, 0.5 mm thick

MS round Dowel bar, Dia:36 mm, Length: 500 mm, Spacing:300 mm c/c

Widening Groove (Sealing detail ‘A”)

Initial 3-4 mm wide cut 90 mm deep

PQC, 280 mm thick

Polysulphide/Polyurethene/Silicon Sealant

Compressible debondingstrip

2 ± 1

10-12 mm

15 mm

5 mm

‘A’-Sealing Detail of joint

Fig.: CONTRACTION JOINT

Soft rope or back-up rod

Initial 3-4 mm wide groove

NETRA Comparison between geopolymer concrete and acceptable criteria of IRC 15

Test Acceptable criteria (IRC:15-2011)

Geopolymer concrete

Compressive strength (MPa) 43 43.5049 (Rebound hammer)

Flexural Strength (MPa) 4.20 4.62 (using equation)

Workability 40 ± 10 mm 50-60 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 39.50 MPa

NETRA

Ordinary Portland Cement

20-80ºC+alkali silicate solution

5CaCO3+2SiO2

Clinker Phases

C-S-H + Ca(OH)2

1450ºC

Hydration (curing with water)

GeopolymericCement

Al2O3+SiO2 in raw material

-Si-O-Al-O-

Alumino silicate 3D framework

Geo-polymer-BasicsDue to use of waste product and use of less CO2 emission reasonGeopolymers are called ‘GREEN MATERIALS’. They are based onalumino-silicate raw materials derived from industrial wastes.

3CaO.SiO2+2CaO. SiO2+5CO2

Non-curing

Geopolymer is a repeated unit of sialate monomerMn [-( SiO2)z-Al-O]n.wH2O

NETRA Raw materials

Coarse aggregate

Fine aggregate(Sand)

Fly ash from power plant

Activators (NaOH etc.)

Admixture (Specialty chemicals)

Constituents of Geo-polymer Concrete

NETRA

World’s 1st buildingQueensland’s University GCI building.

Precast slabs

UTAH State Capitol Building Path ways

World’s 1st commercial production run 2500 T by ROCLA Australia

Success Stories of Geopolymer Concrete

NETRA

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

Fly ash Geopolymeric tetrapods

Manufactured Tetrapods

NETRA

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 1000oC. Sintering technology – Electric Ignition

17

BIS Code: Cleared by sub-committee in Sept’17, Publication by May’18

Light Weight Aggregate (LWA) Plant at Sipat

Demo Plant: Capacity: 50,000 M3/Yr Foot Print: Plant: 1000 sq.m, Storage: 5000 sq.m

NETRA

Light Weight Aggregate (LWA) Plant at Sipat

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CARBON FLY ASHADDITIVE

METERINGMETERINGMETERING

MIXING NODULISING

WATER

METERING

PELLETIZING

SINTERINGLWA

DEDUSTING

NETRA A Maharatna Company Process Flow Sheet Of SINTERED LWA PLANT

*Source: Presentation by SANSAM technologies & engg pvt.ltd

85-90%5-10%2-4%

GREEN PELLETS SINTERED PELLETS(Heat treated above 900oC)

NETRA A Maharatna Company FA-LWA Pellets

*Source: Presentation by SANSAM technologies & engg pvt.ltd

NETRA

Ever increasing demand of natural sand Increasing cost of natural sandAvailability 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.

Process development for conversion of Fly/Pond ash to Sand

NETRA

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.

Use of Bottom Ash as replacement of sand in cement concrete

NETRA

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

Study on high volume use of Fly Ash Cement Concrete

NETRA

Moving towards All Flyash Concrete