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