4. Context
4
• Focus of NGT on Ash Utilization in Distt
Korba.
• Exploring Un-utilized Avenues.
• Prospects for Team Alchemy.
• Idea Generation.
• Existing Methods of Ash Utilization at
NTPC Korba.
• Utilization of Idea.
• Ash Dyke Issues.
5. GoI’s Ash Notification-2015/16
Clause-2.11/ 2.12 & 5.0
2.11 – The Coal based TPP shall promote, adopt & setup Ash based manufacturing
facilities within their premises or vicinity.
2.12 – The coal based TPP in the vicinity of the cities shall promote, support and
assist in setting up of ash based product manufacturing units so as to meet the
requirements of bricks and other building construction materials and also to reduce
the transportation.
5.0 – 100% utilization of Fly Ash generated by 31.12.2017.
6. NTPC’s Ash Policy-2015
Clause-11.0 “Efforts for New Area of Ash Utilization -
Geopolymers”
11.1 Fly Ash based light weight sand. 11.2 Fly Ash based Geo-Polymer Concrete.
*These activities shall be financed from
Ash Fund.
Material Requirement
1) Sodium Silicate – Na2SiO3
2) Sodium Hydroxide – NaOH
3) Fly Ash
Activator
7. Concept of Geopolymers
Geo-polymerisation involves alkaline activation of materials rich in silica and alumina.
Reaction
conditions
Temp/
Time
Solid aluminosilicate raw
material
Alkali
activator
Geopolymer paste
It give a three- dimensional silico-aluminate structure by polycondensation.
8. Potential at NTPC Korba
• Sodium Hydroxide – Pellets used in DM Plant
for Resin Regeneration. Required only for
preparation of alkali activator.
• Sodium Silicate – Required as Binder in alkali
activator solution. It is an inorganic sodium
salt which has silicate as the counterion. To
be arranged/ sourced.
2x NaOH + SiO2 →
(Na2O)x·SiO2 + x H2O
• Aggregate material – Sand/ Gravel or any
other coarse material to be iterated as per
availability.
Raw Material Availability
• Solid Aluminosilicate Raw Material – Available
as Fly Ash in plenty.
Iterations
9. Iteration I – Silica Gel
9
NTPC’s Zero Deviation Document –
• Disposal of Silica Waste - P.No. 36 of 55.
• Material Type – Hazardous as per HWM Rules-
2016.
• Authorization from PCB – Required for Disposal.
• Disposal – Sale to Recycler or disposal at TSDF
facility.
• Documentation – Annual Return/ Storage
permission from PCB.
Present stock at NTPC Korba:
• At Stores – 5 MT
• At site – 1 MT
• Validity of Authorization for NTPC Korba:
Qty – 10 MT/ annum.
Period – 21.11.2024.
Silica Gel stored at NTPC Korba
10. Preparation of Sodium Silicate solution
1. Removing water and impurities from Silica gel and Sodium Hydroxide.
2. Weighment as per stoichiometric requirement.
3. Addition and Preparation of Reactants.
4. Maintaining reaction conditions (100-120 deg C with stirring).
5. Filtration of reaction product.
6. Stocking of sodium silicate solution.
1 5
4
3
2 6
11. Iteration II – Mill Reject as aggregate
11
• Available quantity – 75, 000 MT (approx).
• Material Type – Waste with minimal resale value.
• Authorization – Not required.
• Disposal – Sale on online platform MSTC.
• Utilization proposed – As aggregate for GP
concrete mix after crushing.
• Potential – 1, 35, 000 sqm area.
12. Design Parameters
12
Mix Design parameters selected for Fly Ash
Geopolymer Mortar
Ratio of alkaline liquid to fly ash by
mass
0.35
Concentration of NaOH solution (in
molar)
8
Ratio of Na2SiO3 to NaOH (by
mass)
2.5
Initial Curing Method Oven
Initial Curing Temp (deg C) 60
Curing Time (in hrs) 24
Rest Period (in hrs) 168
Preparation of Fly Ash Geopolymer concrete
Mortar blocks 9X9X9 cm.
Preparation of blocks using Sand-Fly Ash
Geopolymer concrete 15X15 X15 cm.
Preparation of blocks using Mill Reject-Fly Ash
Geopolymer concrete 15X15X15 cm.
9X9X9 cm
Mould
15X15X15 cm Mould
13. Detailed Mix Proportions
13
Details of mix proportions for Fly ash geopolymer concrete
Mix-type proportion GP-Mortar Block Sand-Fly Ash GP Mill Reject-Fly Ash
GP
Fly Ash Only (kg/
m3)
1201 721 960
Sand (kg/ m3) - 480 -
Mill Reject (kg/ m3) - - 241
Extra Water (kg/ m3) 10 10 10
NaOH (kg/ m3) 41 43 45
Na2SiO3 (kg/ m3) 103 108 113
Na2O/SiO2 0.1 0.12 0.15
SiO2/Al2O3 4.68 4.8 4.95
H2O/SiO2 14.70 14.40 14.10
Water to Solids by
weight
0.2 0.2 0.2
14. Preparation Process
Raw Material - Fly Ash GP
Mortar
Raw Material – Sand Fly Ash GP
Concrete
Raw Material – Mill Reject Fly Ash
GP Concrete
Step-1 – Preparation of Precursors & Raw
aggregates
15. Preparation Process
Raw Material – Sand Fly Ash GP Concrete Raw Material – Mill Reject Fly Ash GP
Concrete
Step-2 – Mixing of Raw aggregates
16. Preparation Process
Addition of Alkali Activator Making Dough Mix
Step-3 – Preparation of Dough Mix
Sand-Fly Ash Mill Reject-Fly Ash
18. Preparation Process
Blocks after temperature
curing
Step-5 – Temperature Curing and Resting
Temperature Curing @ 24
Hrs at
60 deg C
Mould after Temperature
Curing
19. Preparation Process
Sand-Fly Ash Geopolymer
Concrete
Step-6 – Final Fly Ash Geopolymer Concrete Block after 4 days
Fly Ash Mortar Geopolymers
Mill Reject - Fly Ash
Geopolymer Concrete
20. Testing planned of GP Fly Ash Concrete
Blocks
20
Tests Planned
• Dimensions & Tolerances
• Compressive Strength at 7, 21 & 28 days.
• Abrasion Resistance.
• Water Absorption Tests after 28 days.
• X-ray Diffraction test for crystallinity.
• SEM analysis to study morphology and
distribution of particles.
Other Iterations proposed –
• Use of Bottom Ash as aggregate
material for construction of test
blocks.
21. Advantages & Disadvantages
21
Advantages
• Reduces Carbon footprint.
• Utilize Fly Ash.
• High Compressive &
Tensile Strength.
• Very low Creep and
Shrinkage.
• Resistant to Heat & Cold.
• Chemical Resistant.
Disadvantages
• Slight Difficult to create.
• Require handling of
chemicals.
• Field is Nascent and still
under study.
22. 22
Areas available for Testing Geopolymer
Concrete
DM Plant CW P/p House CT Area Construction Stores ZLD Area
23. Cost savings/100 sqm concreting of 0.15m
thickness
23
Cement required 28 bags @ Rs 300/ bag (1:2:4) (tentative) = Rs 8, 400/-
Sand & Aggregates Cost @ Rs 3/ kg (1:2:4) (tentative) = Rs 5, 120/-
Total material savings for 100 sqm fly ash geopolymer concreting
with mill reject = Rs 13, 520/-
Cost to be incurred for alkali activator per 15 m3 of fly ash
GP concrete = Rs 42/-
Nominal cost of Mill reject @ Rs 650/ m3 = Rs 4, 062/-
Gross material savings/ 100 sqm fly ash GP concreting = Rs 9, 416/-
• NaOH required for alkali activator can be further reduced by using effluent of
regeneration (2M) in DM plant.
24. NTPC Green Initiatives
24
Our company has planned to replace 11000 MW Thermal Power
Plants older than 25 years with Energy Efficient Super Critical
Plants.
Our company is running more than a dozen initiatives to get rid of
fly ash.
Our company has planted 20 million trees till date in and around its
projects.
Our company have committed to use treated sewage water at its
Dadri Power Station.
Our Company has set ambitious targets for promotion of Green
Hydrogen as alternate fuel for Transport and Gas turbines.
25. Conclusion
25
Our company has been at the forefront of Agro Residue and
Municipal Solid Waste Management, to give the capital and
NCR cleaner air.
Our company has invited developers to set up 100 waste-to-
energy plants.
Our company has gone for Paperless Office through “PRADIP”
Project.
Going Green begins at home’ is the company’s mantra in
all aspects of its operations.
26. 26
• The savings on account of use of Fly Ash GP may
not be huge.
• As a responsible corporate entity, NTPC can spread
environment protection message among its industry
peers.
• Inhouse utilization of fly ash will help NTPC to
achieve the GoI set target of 100% ash utilization
from TPP’s
• Moreover, this initiative will add one more feather in
already bright cap of NTPC towards environment
protection.
Conclusion
30. Laboratory Testing of GP Fly Ash Concrete
Blocks
30
Sample Block Compressive Strength at
25 oC in N/mm2
(IS 15658: 2006)
*Cement Mortar Blocks 7.5
*Concrete Blocks (M25) 18.3
**Fly Ash GP Mortar
Blocks
**Fly Ash - Sand GP
Blocks
**Mill Reject - Sand GP
Blocks
*Source – IS 2185: 2005 “Concrete Masonry Units”.
31. Laboratory Testing of GP Fly Ash Concrete
Blocks
31
Sample Block (after 28 days curing) Water Absorption at room temp %
(IS 15658: 2006)
*Cement Mortar Blocks 1.5
*Concrete Blocks 2.4
Fly Ash GP Mortar Blocks
Sand – Fly Ash GP Blocks
Mill Reject – Fly Ash GP Blocks
*Source – IS 2185: 2005 “Concrete Masonry Units”.
Notas do Editor
1 sq ft = 0.09 sqm
1 cum = 35.3 cuft
Aggregate req = 1.35cuft per sqft i.e. 1350 cuft for 1000 sqft
SEM- Scanning Electron microscopy
1 m3 = 2.4 MT
Water absorption
IS 15,658:2006. The block was completely immersed in water tank at room temperature for 24 hours. The block was removed and allowed to drain for 1 minute. The excess water on the surface of block was removed by damp cloth. The weight of block was noted immediately. Afterwards, the block was dried in a ventilated oven at 110ºC for 24 h. The dry weight of each block was recorded. The water absorption of block was calculated by taking the difference of weights of saturated block and dry block and dividing it by the weight of dry block.
