SHRIRAM INSTITUTE FOR INDUSTRIAL RESEARCH19, UNIVERSITY ROAD, DELHI - 110 007
Presented by :
Dr. R. K. KhandalDirector
Fly Ash: A Resource of Extraction of Metals & High Value Products
Content
1. Fly Ash utilization : levelsvalue additionvolume additionchallenge addition
2. Utilization of Fly Ashcement & ceramicsextraction of metalsCenospheres
3. Need for BIS specifications4. Path forward
Al 2
O3
TiO2
SiO2
Al
Fe
Si
U Ti
Mg
Ca
VA
LUE
AD
DIT
ION
Ash
As such
Component
Reaction
Separation
Extraction
Fly Ash Utilization: Value addition
Fly Ash Utilization: Volume Addition
VOLUME ADDITION
As such
WastecreteBack filling
Land reclamationEmbankment filling
Cement concrete
Soil stabilizationPlastic compositesBricks
Reaction
MulliteCenosphere
Separation
Water purificationEffluent treatment
Extraction
AlCa
Al2O3
TiO2
SiO2
TilesGlass
Ceramics
MgTi
FeSi
U
Components
Fly Ash : Challenge additionEach step upwards: a)adds value andb)involves challenges
Each step drives :a) fly ash utilizationb) sustainable way C
hal
len
ge
Geo-polymers
Waste
Materials
Specialty materials
Precious
Resource
Fly Ash: Types & Components
Other elements present in traces: Hg, Cd, Sb, Se, Ti, V (1-10 ppm)
As, Cr, La, Mo, Ni, Pb, Th, U, Zn (10-100 ppm) B, Ba, Cu, Mr, Sr(100-1000ppm)
Fly Ash
Class F Class C
1-2
Burning of Bituminous & Anthracite
Burning of Lignite & Sub Bituminous
1-2
Low Fe High Fe Low Ca High CaComponents
SiO2
Al2O3
MgOK2O
TiO2
Fe2O3
CaO
Na2OSO3
46-5718-296-162-6
0.7-2.12.0-3.00.2-10.4-30.6-5 LOI
42-5417-2416-241-4
0.3-12.1-2.70.2-10.5-21.2-5
46-5914-225-138-163-5
0.5-11-4
0.5-30.1-2<1
25-4215-215-10
17-324-12
0.3-1.61-6
0.5-50.1-1<1
Utilization of Fly Ash : Cement
Cement: Composition
Al2O3
CaO
SiO2Fe2O3
C3A C3S C2S C4AF
Lime binding modulus of fly ash = CaO / (SiO2+Al2O3+Fe2O3)
Portland Cement: Types (as per ASTM)
General purpose, residential purposeType I, Ia
Type II, IIa
Type III, IIIa
Type IV
Type V
heat of hydration, sulfate resistance
Early high strength in one to three days
Heat during hydration kept to a minimum,
intended for large masses e.g. dams
Sulfate resistant, especially good for
marine structures & soils with high alkali
“a” type cements contain additional air entrainer
Portland Cement: Classification
Ingredients
I
C3S (%) 55
C2S (%) 19
C3A (%) 10
C4AF (%) 7
Others 2.8
II
51
24
6
11
2.9
ASTM Types
57
19
10
7
3
IV
28
49
4.0
12
V
38
43
4.0
9.0
1.91.8
III
45
27
11
10
7
43
50
22
11
10
53
55
17
11
9
87
33
BIS Grades
Quality evaluation of ASTM & BIS for cement are different: ASTM Specifications emphasize on the oxides’ composition BIS specifications emphasize on the strength of cement
Fly Ash : Components Component
CaO
SiO2
Al2O3
5.0
48.024.0
Fe2O3 10.0
Average Content(%)
Others
Range
Min (%) Max (%)
1 10
34 61
17 305 16
Remainder
C3S
C2S
C3A
3
2
3
C4AF 4
1
1
0
0
CaO SiO2 Al2O3 Fe2O3
0
0
1
1
0
0
0
1
45
27
11
10
Gr 33 Gr 43 Gr 53
50
22
11
10
55
17
11
9
Mo
le R
atio
Per
cen
tag
e
Fly Ash Addition in Cement : Criteria
C3S (100%)
Grade : 33 CaO SiO2 Al2O3 Fe2O3
0 0
32.2 12.8
71.5 28.5
C3S (45%)
C2S (100%) 0 0
17.6 9.4
65.1 34.9
C2S (27%)
C3A (100%) 0 0
6.8 4.2
62.2 38.0
C3A (11%)
C4AF (100%) 0 32.9
4.6
46.1
C4AF (10%) 2.1
20.9
3.3
61.2 22.2 6.3 3.3Total
Composition of Cement Using Fly Ash
Component
Fly ash (100%) 5.7
1.71
55.2
16.6
CaO SiO2 Al2O3 Fe2O3
27.6
8.3
11.5
3.4Fly ash (30%)
Lime (70%) 70
Total (Cement)
71.71 16.6 8.3 3.4
+
Answers the question as to why BIS allows Fly ash addition in cement not more than 35%- !
5.7 55.2 27.6
8.3
11.5
3.41.71 16.6
70
71.71 16.6 8.3
5.7 55.2 27.6
8.3
11.5
3.4
Cement:Pozzolanic Activity
Depends on active Silica content
Relates to amount of active contents e.g. SiO2 & Al2O3
Shows good strength Long term durability Corrosion resistance
CH Pozzolanic activity
CH + SH CSH
Pozzolanic reaction is slower than other hydration reactions
Calcium hydroxide
Silicic acid
Calcium silicate hydrate
Consumption of CH Pozzolanic activity
SiO2 + CaOH2O
Utilization of Fly Ash : Ceramics
Ceramic : Types
Composition
Oxides Non-oxides Composites
Al, Zr, Ce, Be •Carbides•Borides•Nitrides
•Fiber reinforced,
•Particulate reinforced
Ceramics Using Fly Ash
Al2O3.2SiO2.2H2O 3Al2O3.2SiO2 + 4SiO2 + 6H2O
Large amounts of CaO, Al2O3 & SiO2
Mullite Cristobalite
Kaolinite
Composition similar to glass
Typical glassy ternary system CaO-Al2O3-SiO2
Why Fly ash for Ceramics?
Significant amount of MO Act as Nucleating agents
Partial replacement for clay Clay/Fly ash blend
Utilization of Fly Ash : Extraction of Metals
Fly Ash : Extraction & Separation of Metals
Valuable components Present at macro level (%)
Hazardous components Present at micro level (ppm)
Fe, Al, Si Cenosphere Valuable components present at micro levels < 1%
Hg, Cd, Sb, Se, Ti, V (1-10 ppm)
As, Cr, La, Mo, Ni, Pb, Th, U, Zn (10-100 ppm)
B, Ba, Cu, Mr, Sr(100-1000ppm)
Valuable components are extracted from the fly ash using physical/chemical processes Fly ash detoxified for hazardous components
Raw Material for Alumina
Type
50-70 % 17-23%
Bauxite Fly ash
Lumps Powder
Availability Geographically distributed
Universally abundant
Production
Al2O3 Content
Mining operation Nothing special
Fly ash can be preferred source for Al in case of countries
importing bauxite; may not be applicable in case of India
Physical appearance
Separation of Alumina : Fly ash vis-a-vis Bauxite(Baeyer’s Process)
Fly ash
Removal of Carbon
Removal of Fe
Removal of Ca, Mg, N, K, Ti, Fe(Al rich Fly ash)
Al(NO3)3 solution
3C + 4HNO3 4NO + 3CO2 + 2H2O
Heat
Magnetic separation
Treatment with weak HNO3
Treatment with conc. HNO3
Crystalization
Carbon removal prevents addition of large vol. of HNO3
Al(NO3)3 .9H2O
Al2O3 + NO2 + H2O
Mining
Concentration
Powdered Bauxite
Removal of impurities
Al:Si ≥ 7 in raw Bauxite ore Fly ash contains Al:Si<7 Hence cannot be used for this process
Lumps of Bauxite
Crushing
Al2O3 in Bauxite+ NaOH
Al(OH)3
+ HCl + H2O
NaAlO2+ H2O + NaAl Silicate+ Impurities(SiO2+Fe2O3+TiO2
Bauxite
Al2O3 + 3 H2O
NaCl + Red Mud (SiO2 + Fe2O3 + TiO2)
+
Heat
Extraction of IronHematite Ore (70% Fe2O3)
Chemical Process
Small particles of Hematite
Hematite free of clay, gangue
Fe2O3
Pig Iron(S, C, Si or P impurities)
Wrought Iron
Fly ash (5-24% Fe2O3)
Physical & Chemical Process
Residue Fly ash
C + O2 CO2
CO2 + C 2COFe2O3 + 3CO 2Fe + 3CO2
CaCO3 + SiO2 CaSiO3+ CO2
Fe2O3
Breaking
Washing
Calcination
Reduction with Coke
Removal of impurities
CaCO3
Magnetic separation
Fe2O3 is removed from fly ash rich in Al2O3 & Fe2O3 to use it as refractory material
Wrought Iron
Separation of Silica From Fly AshFly ash
Alkali treatment
Activated fly ash
Fly ash residue containing Alumina
Al2O3
Separation of SiO2 from Alumina
Activation Roasting/ acid or alkali steeping
Clinker
Alkali addition
Solution
Al(OH)3
Carbonation
Calcination
Residue
Used as filler or for making
cement
Sodium silicate solution
Mixture
Filteration
FiltrateResidue
Recycle
+ CaOCarbonation
> 98% SiO2
Fly Ash : Extraction of Metals Present in Traces (For Detoxification)
Hg, Cd, Sb, Se, Ti, V (1-10 ppm)
B, Ba, Cu, Mn, Sr(100-1000ppmAs, Cr, La, Mo, Ni, Pb, Th, U, Zn (10-100 ppm)
Trace Metals in Fly ash
Acid leaching
Extraction Procedures
Fly ash Fly ash free of Cu, Cd, Pb, Mn & ZnAcid
pH=3
Vaporization with Chlorine
Fly ashFly ash free of U impurities
Heat/C/Cl2
Volatilization of metal chlorides
Supercritical Extraction
Fly ash Fly ash free of Cu, Cd, Pb, Mn & Zn
Supercritical CO2/Cyanex302
Phytoextraction
Soil + Fly ash Fly ash + soil with reduced Mn, Ni, Cu, Zn& Pb)
Growth of wetland plants
Condensation
Utilization of Fly Ash : Cenospheres
Cenospheres
Properties• Density : 0.6 – 2 g/cm3
• Particle Size : 1-500 µ• Spherical & hollow
Gas from coal burning Molten particles of fly ash
Spherical particles with gas entrapped
Microspheres
CENOSPHERES
Composition•SiO2 : 65 %•Al2O3 : 25–35%•Fe2O3 : 1-5%•TiO2 : 1.5%
Application•Fillers in cement: Low density concrete•Foam: i) Composite material: with metals & Polymer ii) Automotive sector: Aluminium foam
+
Cenospheres : ExtractionExtraction (Physical Process)
Wet Dry
Recovery from fly ash ponds
Disadvantages
Dissolution of toxic materials in waterLand availabilityAdditional drying step
Overflow
Underflow (UF)
Main air Flow (Feed)
Sub-air Flow
Sample
Rotor
Coarse Particles
Fine Particles
Pneumatic/micron separator
Utilization of Fly Ash : Need for BIS Specifications
TILESNot used at present
Specified
Not yet Specified
445710779428 &41396 & 821802222269135834885
BRICKSFly ash lime bricksBurnt clay fly ash bricks
1289413757
IS Code Materials IS Code
BRICKSAcid resistant bricksBurnt clay bricksCa-silicate brick
High alumina bricksClay bricksPerforated bricksFacing bricksPaving bricksSewer bricks
Materials
1237156226250112865413801
TILESFlooring tileCeramic tilesSlate tilesLimestone slab&tilesClay roofing tilesChequered tiles
Use of Fly ash : BIS Specifications
156583006
125925758
CONCRETEAAC blocks Lime concrete Ready Mix Concrete Light Weight Concrete Lime PozzolanaConcrete Blocks
Code of Practice For PCC & RCC
2185 & 622025414926914210359 &10360
456
Materials
CONCRETEPaver block
Chemical Resistant Paver
Manhole CoverPrecast Kerb &
Channel
12330690764529743
CEMENTPortland PozzolanaOil well CementLow Heat Cement
1489822912600
CEMENTSulphate ResistantSuper sulphateHigh AluiminaThermal Insulating
Use of Fly ash : BIS SpecificationsSpecified
Not yet specified
IS Code Materials IS CodeMaterials
33165913
105704586517741592142231197
MISCELLANEOUSNot in use at Present
MISCELLANEOUSGraniteAsbestos CementSheetsFire Clay RefractoryConcrete PipeStone ware pipeSanitary wareAsbestos Cement PipePolished Bldg. StoneMastic Asphalt
Use of Fly ash : BIS Specifications
Specified
Not Yet Specified
IS Code Materials IS CodeMaterials
Utilization of Fly Ash : Path Forward
Utilization of Fly Ash : Path Forward
Reaction Products
Extraction
Used as such as a substitute for fillers
Separations of constituents
As an additive component to enhance performance of the composition
Volume Addition
Challenge
Clockwise developmental path would be the most practical, successful & sustainable for fly ash utilizationKey driving forces : Realization Adoption Orientation Institutional Diffusion
Sustainability Entrepreneurial development
Value Addition
Thank You