Solidification/stabilization of hazardous materials for … · 2006-10-30 ·...

Korea Institute of Geoscience and Mineral Resources

Solidification/stabilization of hazardous materials for recycling the industrial wastes

2006. 4

Ji-Whan Ahn

Korea Institute of Geoscience and Mineral Resource


Categories of wastes in Korea

Wastes

household wasteGeneral industrial waste

Construction waste

Hazardous industrial waste

Industrial waste

Sewage sludge

By generated field & industry

Wastes

Waste with high heavy metal content

Waste with low heavy metal content

By content of heavy metals

Recover potential energy value from the wastes

Enhance process efficiency

→ Need to new recycling field for the consumption of the wastes


Trend of waste treatment

Many countries recognize that although the recycling is the best solution in their disposal,it may not be viable, economically or due to the fact that recycling also generates further wastes.

Incineration

Recycling

Landfill

- Insanitary- Lack of landfill- Pollution in underground

- High investment &operation cost

- Air pollution, dioxin- Residue

- Refuse Derived Fuel(RDF)

- Alternative materials- Fertilizer

- More friendly to the environment- Helpful in recovering energy from waste


Co-incineration technique in cement industry

The co-incineration technique consists of partial substitution of raw materials or fuel for waste in a high temperature industrial process in such a manner that the waste is destroyed, the generated ash is incorporated in the product, and the product quality is not affected.

The co-incineration process provides an economy to the process in addition to providing a hazardous waste treatment methods

Cement IndustryCement Industry


Cement industry & incinerator

• high volume and weightreduction

• generation of residues• secondary pollution

Remarks

20-30wt.% of raw wasteResidue

2secResidence time

above 850oCTemperature

IncinerationItem

Incinerator

Comparison cement kiln with incinerator

above 1,450oCdecomposition of hazardous substances

Temperature

None zero pollutionResidue

5secResidence time

• need for homogenizing of components- control of heavy metals- control of volatile components

• use of present facilities• mass treatment

Cement kiln

Remarks

Item

Cement Industry


Recycling amount of wastes in cement industry

Cement Industry

[Million ton]

5.9 8.4

• Sludge & dust, slag etc

‘99

‘03

[Million ton]

0.1 0.4

• Sewage sludge

‘99 ‘03

IndustryIncinerator

- Iron making industry- Chemical industry- Power plant

[Million ton]

1.5 2.6

• Coal ash

‘99‘03 [Million ton]

• MSWI ash

‘99 ‘03

0.0 0.0

Increase rate for waste application in cement industry : about 10%, annually

To increase ratio of recycling amount, the studies on how to reuse as raw material in cement industry

Especially, municipal solid wastes have to be used in cement industry


Emerging Technologies for Environmental friendly Materials

• Sewage sludge & Construction waste• Sludge & dust, slag etc

• Fly & bottom ash

Manufacture Tec. Products Protect Env.Treatment Tec.

Ordinary Portland Cement

Special cement (CSA cement) (Calcium sulfo-aluminate)

Eco-cement (CCA cement)(Calcium chroline-aluminate)

Discharge of hazardous substances

- Dioxin - CO gas- SOx & NOx gas

Envir. Stability of Products

Volatilization/condensing of volatile substances

Heat distribution changein kiln

incomplete sintering/yellow clinker

Control wastes Tech. - Mixing & Crushing- Separation- Content of water

Storage of wastes

Emerging Tech.


Manufacture Tec. Products Protect Env.Treatment Tec.

Emerging Tech.

Slag & Dust from POSCO

MSWI bottom ash Behavior of chlorine & volatile substance in Kiln

Produce OPC in Plant

Calcium sulfo-aluminate cement synthesis from slag from iron making industry

Calcium chroline-aluminatecement synthesis from MSWI ash

Ordinary Portland cement Manufacturing from inorganicwastes

Behavior of circulation of toxic gas

Estimation of discharge gasfor air environment

Content of our research

Ordinary Portland Cement

Special cement (CSA cement) (Calcium sulfo-aluminate)

Eco-cement (CCA cement)(Calcium chroline-aluminate)

Discharge of hazardous substances

- Dioxin - CO gas- SOx & NOx gas

Envir. Stability of Products

Volatilization/condensing of volatile substances

Heat distribution changein kiln

incomplete sintering/yellow clinker

Control wastes Tech. - Mixing & Crushing- Separation- Content of water

Storage of wastes

Applying waste as the raw material to cement industry, it is possible to influence to the cement products and process→ To use wastes in cement industry, it is necessary to research on the behavior of heavy metals and alkali chlorine,

and influence on the cement properties.

Emerging Technologies for Environmental friendly Materials in Korea


A Pretreatment for Cl Removal and Stabilization of Heavy Metal to Recycle Municipal Solid Waste Incineration Bottom Ash


Disposal situation of municipal solid waste in Korea

Generation of municipal solid waste in 2003 : about 15 million tonsIncineration ratio : 5.5(1996) 14.5(2003)


Category of municipal solid waste incineration ash

Fly ash

Bottom ash

Korea

Mixed material collected from APC system including fly ash, injected adsorbent, flue gas condensate

Particulate material transported to the top of the incinerator and removed from flue gas.

Particulate material collected from the heat recovery system

Material remaining after excluding grate siftings from bottom ash

Material dropped through grate

Material discharged from the bottom of incinerator

Location

APC Residue

Fly Ash

Heat Recovery Ash(HRA)

Grate Ash

Grate Siftings or Riddlings

Bottom

Ash Category

Grate sifting or Riddlings Ash

Fly Ash

Boiler

APC residue

Heat Recovery Ash(HRA)Grate Ash

Bottom Ash

Fine particulate removal systemEnclosed receiving area

Heat recovery system


1,0005,000∼20,000

250

Commercial and industrial areaHHS/ATSDR(’97)

EPA(’98)

residential district

industrial area and road

40

10,000

1,0001,000

commercial and industrial area

parkresidential district

playground

5∼40farm land

1,000

10

1,000

100

(Pg-TEQ/g)

residential districtUSA

Residential district, farm land, playgroundSweden(’96)

town

town

Objects

Netherlands(’97)

Germany

Countries

2.4211.43PCDDS/DFs0.723.99PCDDs0.010.14OCDD0.040.531,2,3,4,6,7,8-HpCDD0.210.581,2,3,7,8,9-HxCDD0.290.761,2,3,6,7,8-HxCDD0.180.261,2,3,4,7,8-TCDD0.000.961,2,3,7,8-TCDD0.000.772,3,7,8-TCDD1.707.44PCDFs0.010.03OCDF0.030.051,2,3,4,7,8,9-HpCDF0.030.531,2,3,4,6,7,8-HpCDF0.240.181,2,3,7,8,9-HxCDF0.221.142,3,4,6,7,8-HxCDF0.140.871,2,3,6,7,8-HxCDF0.090.411,2,3,4,7,8-HxCDF0.923.652,3,4,7,8-PCDF0.020.141,2,3,7,8-PCDF0.000.442,3,7,8-TCDF

pg-TEQ/gpg-TEQ/gBottom ash DBottom ash I

2,3,7,8-sustitution

Guidelines for soil pollution of dioxin in various countries

(Source : NREL, 2000)

Amount of dioxins in bottom ash of Korea

-----

1,000-500----

400*10-3-310*10-3

----

Mid-CornDry Scrubber1Dry Scrubber2Dry Scrubber2Dry Scrubber3

USA

1.8*10-3

2.0*10-3

0.8*10-3

96*10-3

91*10-3

94*10-3

36*10-3-39*10-3

41*10-3-48*10-3

25*10-3-29*10-3

ABC

Germany

-----

NDNDND

<0.2*10-3

ND

NDNDND

400*10-3

ND

GVRDPEILVH

SWARUQUC

Canada

1/TEQTotal Furans(PCDF)

Total Dioxins(PCDD)FacilityCountry

Amount of dioxins and furans in bottom ash in various countries

Environmental hazardousness - dioxin

Amount of dioxin in bottom ash satisfies environmentalguidelines for soil pollution of dioxin Amount of dioxin in bottom ash satisfies environmentalguidelines for soil pollution of dioxin

(unit:pg/g)


Removal & Solidification of chloride in MSWI bottom ash

- Synthesis of calcium chlorine-aluminate cement (CCA cement) -


• heavy metals and its compound

•• batterybattery

•• vinylvinyl

•• ceramicsceramics

•• food wastefood waste

AdsorptionAdsorption•• clayclay•• Fe/Fe/MnMn OxideOxide•• organic matterorganic matter

→→ soil pollutionsoil pollution

CdCd2+2+

PbPb2+2+

CuCu2+2+

ZnZn2+2+

Metal OxideMetal Oxide

Metal HydroxideMetal Hydroxide

Al(Al(MnMn, Fe), Fe)ㆍㆍMM(z(z--)+)+ O O

SoilSoilSoil

incinerationincineration

Environmental harmfulness of chloride

Municipal solid wasteMunicipal solid waste


• chloride and salts

NaClNaCl

KClKCl

CaClCaCl22ㆍㆍ6H6H22OO

+ H+ H22O O ⇒⇒ClCl--

ClCl--

•• ChloroformChloroform•• ChloriteChlorite•• ChlorateChlorate

→→ synthesissynthesis

poisonousnesspoisonousnesspoisonousness

ClCl--

• ionization

Volume-rate garbage disposal system


Removal of chloride

(L/S ratio : 10, Temp. : 20oC)

chloride removal of above 85% within 30minutesresidual chloride content of bottom ash : 0.2-0.3%

Res

idua

l chl

orid

e co

nten

t(%

)


The sintering temperature of CCA clinker

Ordinary cement approximately 1,450oC

Ecocement approximately 1,350oC

Reduction of CO2 emission

Application: Soil stabilization projects

Calcium-chloroaluminate(11CaO·7Al2O3·CaCl2) cement

Characteristics of CCA cement


Soil stabilizer

Application field of CCA cement


2.5

2.7

Cl

1.105.750.211.653.4723.292.218.781.0710.2724.70Bottom ash I

Bottom ash D 2.20

MgO

0.98

TiO2

27.50

SiO2

1.20

ZnO

4.70

P2O5

2.50

Na2O

9.48

Fe2O3

2.00

K2O

25.49

CaO

8.50

Al2O3

0.25

MnOSample

Chemical composition of Municipal solid waste incineration bottom ash

(Unit : wt.%)

20 30 40 50 60

: larnite: quartz: lime: C

11A

7CaCl

2: calcite

1,000oC

800oC

600oC

400oC

200oC

Int.

2θ20 30 40 50 60

: lime: larnite: C

11A

7CaCl

2

: quartz: calcite

1,000oC

800oC

600oC

400oC

200oC

Int.

2θ

(a) (b)

Synthesis of calcium chloroaluminate : above 1,000oC

XRD patterns of (a) bottom ash I and (b) bottom ash D with various temperatures


ND0.0550.0110.065ND0.030120

NDND0.0070.030ND0.01228

0.00530.31.531.5Environmental criteria

HgPbCdAsCuCr

0.011

0.031

0.027

0.037

0.028

0.03

ND

0.041

0.015

0.027

0.011

0.028

0.037

0.028

ND

0.010

Concentration of heavy metal in leaching (ppm)

ND0.0350.0050.054ND28

ND0.0340.0140.063ND28

ND0.0070.0080.054ND28

NDNDNDNDND28

NDNDND0.050ND28

ND0.0100.0050.022ND28

ND0.046ND0.067ND28

NDNDNDNDND28

1

1

1

1

1

1

1

1

Curing time(day)

ND

ND

ND

ND

ND

ND

ND

ND

0.055

0.036

0.017

0.010

0.041

0.025

0.022

ND

0.055

0.066

0.048

0.057

0.069

0.056

0.032

ND

ND

ND

ND

0.003

ND

ND

0.004

ND

0.00713

0.01111

0.0099

0.0087

0.0135

0.0133

ND0

0.01015

Additive ratio of CCA(%)

Leaching of heavy metals from manufactured cement

It satisfies the environmental standard and regulation


Solidification & stabilization of heavy metalsin MSWI bottom ash


• heavy metals and its compound

•• batterybattery

•• vinylvinyl

•• ceramicsceramics

•• food wastefood waste

AdsorptionAdsorption•• clayclay•• Fe/Fe/MnMn OxideOxide•• organic matterorganic matter

→→ soil pollutionsoil pollution

CdCd2+2+

PbPb2+2+

CuCu2+2+

ZnZn2+2+

Metal OxideMetal Oxide

Metal HydroxideMetal Hydroxide

Al(Al(MnMn, Fe), Fe)ㆍㆍMM(z(z--)+)+ O O

SoilSoilSoil


Environmental harmfulness of chloride

Municipal solid wasteMunicipal solid waste


• chloride and salts

NaClNaCl

KClKCl

CaClCaCl22ㆍㆍ6H6H22OO

+ H+ H22O O ⇒⇒ClCl--

ClCl--

•• ChloroformChloroform•• ChloriteChlorite•• ChlorateChlorate

→→ synthesissynthesis

poisonousnesspoisonousnesspoisonousness

ClCl--

• ionization

Volume-rate garbage disposal system


Aging of Bottom Ash for stabilization of heavy metals

ObjectivesObjectivesStabilization of soluble salts

Stabilization of hydrogen-forming metals (such as aluminum)

Proper maintenance of moisture

Control of pH by carbonization reaction and stabilization of heavy metals

Time requirement for 3-6 months

U.S

ageing for 60 days for using as aggregates of concrete

ageing for 30 days for using as pavement materials

France

ageing for 3-6 months

Germany

ageing for 3 months for recycling of bottom ash

England

ageing for 3-6months for using as aggregates of concrete

MM••(OH)(OH)nn

MMxx++

(At 850℃, about pH 12) (At 850(At 850℃℃,, about pH 12) about pH 12)

MM••COCO33

MM••OO

• Oxidation•• OxidationOxidation

MM•• (OH)(OH)nn

COCO22

•• CarbonationCarbonation

(M: metal(Al, Fe, Cu etc)) (M: metal(Al, Fe, Cu etc))

MM••OO

HH22OO

••HydrolysisHydrolysis

TemperatureTemperatureTemperature pHpHpH

VolumeVolumeVolume

Vol

ume

Vol

ume

Tem

p &

pH

Tem

p &

pH

TimeTime

Aging requirement of bottom ash for road materials


Stabilization/conversion of bottom ash during aging

•• Ion solidification Ion solidification

•• CaSOCaSO44 •• 1/2H1/2H22O + 1O + 111//22HH22O O

→→ CaSOCaSO44•• 2H2H22OOGypsumGypsum

•• αα -- FeFe22OO3 3 →→ FeOOHFeOOH

•• Feldspars Feldspars →→ KaoliniteKaolinite

Ageing for several yearsAgeing for several years-- Stable Stable --

•• CaO CaO + H+ H22O O →→ Ca(OH)Ca(OH)22Calcium oxide Calcium oxide PortlanditePortlandite

•• CaSOCaSO44 + 1/2H+ 1/2H22O O →→ CaSOCaSO44•• 1/2H1/2H22OO

•• Dissolution of saltsDissolution of salts

Quenching of bottom ashQuenching of bottom ash-- Unstable Unstable --

•• Ion sIon solidification olidification

•• Ca(OH)Ca(OH)22 + CO+ CO22 →→ CaCOCaCO33Portlandite Portlandite CalciteCalcite

•• FeFe33OO44→→γγ -- FeFe22OO33 →→ αα -- FeFe22OO3 3

•• Expansion of aluminum Expansion of aluminum

Ageing for 3monthsAgeing for 3months-- SemiSemi--stable & stable stable & stable --


CdCd2+2+ CdCd2+2+CdCOCdCO33

PbPb2+2+PbPb2+2+

CuCu2+2+CuCu2+2+

ZnZn2+2+ZnZn2+2+

PbCOPbCO33

CuCOCuCO33

COCO22

COCO22

COCO22

COCO22

ZnCOZnCO33

Cd2+ + CO2 → CdCO3CdCd2+2+ + CO+ CO22 →→ CdCOCdCO33

Zn2+ + CO2 → ZnCO3ZnZn2+2+ + CO+ CO22 →→ ZnCOZnCO33

Pb2+ + CO2 → PbCO3PbPb2+2+ + CO+ CO22 →→ PbCOPbCO33

Cu2+ + CO2 → CuCO3CuCu2+2+ + CO+ CO22 →→ CuCOCuCO33

Low solubility

Low solubility

KKspsp=2.6=2.6××1010--11

KKspsp=3.8=3.8××1010--22

KKspsp=7.5=7.5××1010--11

KKspsp=2.4=2.4××1010--11

Carbonation for Fixation of Metals in MSWI Bottom Ash


0 2 4 6 8 10 12 14

1ppm

Cr3+

Fe2+

As3+

Pb2+

Zn2+

Cd3+Cu2+

Hg2+

Fe3+

Cr3+

0

-2

-4

-6

-8

-10lo

g m

M(M

/L)

pH

2.4　10-14.3　10-15.2　10-13.0　10-2

ZnCO3ZnSZn(OH)2Zn3(PO4)2Zn+2

7.5　10-11.6　10-111.1　10-23.1　10-3

CuCO3CuSCu(OH)2Cu3(PO4)2Cu+2

1.2　10-118.1　10-3Cu2SCuOH

Cu+

1.3　10-212.4　10-1HgSHg(OH)2

Hg+2

1.15.4　10-11Hg2CO3Hg2SHg2HPO4

Hg2+2

2.6　10-12.5　10-91.14.1　10-2CdCO3CdSCd(OH)2Cd3(PO4)2

Cd+2

3.8　10-22.1　10-97.1　10 22.3　10-4PbCO3PbSPb(OH)2Pb3(PO4)2

Pb+2

2.3　10-13.1　10-22.3

MnCO3MnSMn(OH)2Mn+2

6.3　10-42.5　10-7Cr(OH)3CrPO4

Cr+3

7.1　10-7Cr(OH)2

Cr+2

CarbonateCarbonateSulfideSulfideHydroxideHydroxidePhosphatePhosphateIonIon

Solubility of heavy metals hydroxidesSolubility product constant of heavy metals compount(25℃)


10.211.812.012.212.5bottom ash D

9.411.111.311.512.3bottom ash I

63210

Aging period(month)Samples

3.00.31.53.01.5Leaching criteria of Korea

0.06NDND1.731.730.039.46

0.06ND0.054.414.410.1512.50bottom ash D

0.05ND0.021.81.80.1010.26

0.08ND0.063.263.260.1312.30bottom ash I

PbCdAsCuCr

Concentration (mg/L)pHAging period

(month)Sample

Leaching concentration of heavy metals

pH change

Stabilization of heavy metals during aging


bottom ash I

bottom ash D

3.00.31.53.01.5Criteria of leaching

0.55NDND3.400.5012.2

0.340.1500.63.680.00436.8

0.840.7104.432.371.804.0

1.730.97627.6141.7512.941.8

0.40NDND3.250.489.4

Leached heavy metals(Leached heavy metals(ppmppm, As : ppb), As : ppb)pHpH

2.83NDND5.260.5013

0.590.0050.63.400.278.3

PbPbCdCdAsAsCuCuCrCr

3.00.31.53.01.5Criteria of leaching

5.49NDND3.490.313

0.67NDND2.450.312

0.25NDND1.770.039.1

0.510.00161.61.67ND7.7

0.440.343.32.97ND5.7

0.900.905.417.120.303.8

1.981.2630.094.453.572.3

PbPbCdCdAsAsCuCuCrCr

Leached heavy metals(Leached heavy metals(ppmppm, As : ppb), As : ppb)pHpH

Leaching of heavy metals with pH


Stabilization of heavy metals by carbonation

1.50.31.53.03.0criteria

ND

ND

ND

ND

ND

As

0.2

0.1

0.1

0.2

0.2

Cr CdPbCu

ND0.71.38

ND0.51.19

ND0.51.310

ND0.54.011

ND0.65.112.3

Concentration of leached heavy metals(mg/L)pH

Concentration of leached heavy metals with pH change by carbonation

pH 10-8 satisfied the environmental standards and regulation


Leached Cu concentration with carbonation time and CO2 flow rate(temp. : 20oC, L/S ratio : 10(v/w))

Cu leaching by carbonation- diminishment above 50%(3.7ppm 1.3ppm)

0.050.05

0.100.10

0.150.15


Comparison of natural weathering and carbonation

10.211.812.012.212.3D bottom ash

9.411.111.311.511.7I bottom ash

63210

Aging period(month)Samples

3.00.31.53.01.5criteria

0.06NDND1.731.730.039.46

0.06ND0.054.414.410.1512.50D bottom ash

0.05ND0.021.81.80.1010.26

0.08ND0.063.263.260.1312.30I bottom ash

PbCdAsCuCr

Concentratiom(mg/L)pHAging period

(month)Sample

Leaching of heavy metals

Natural weatheringNatural weatheringpH

Stabilization periodof heavy metals

1.50.31.53.03.0criteria

ND

ND

ND

ND

ND

As

0.2

0.1

0.1

0.2

0.2

Cr CdPbCu

ND0.71.38

ND0.51.19

ND0.51.310

ND0.54.011

ND0.65.112.3

Leached heavy metals(mg/L)pH

CarbonationCarbonation

Natural weathering: 3-6months

Carbonation : Within 2 hours


Characteristics of wastewater after treatment

<4057.3COD

5.8-8.6

<0.3

<0.1

<0.003

<3,000

<5

<400

<15

criterion

<10

<0.5

<1

<0.5

<1

<0.005

<3

<5

criterion

<0.1

<10

<30

<1

M* : <5

O **: <30

<5

<8

<60

criterion

9.5

ND

ND

ND

<2

0.56

42

0.30

Waste

water

pH

PCE

TCE

PCB

E.Coli

ABS

Color

F

Sample

Items

0.02

ND

0.09

0.001

ND

ND

0.05

0.03

Waste

water

Mn

Cr

Pb

As

Organophosphorus

Hg

Cu

Zn

Sample

Items

ND

0.05

42.5

0.002

ND

ND

7.03

12.1

wastewater

Cd

Fe

BOD

CN

N-hexane extracts

Phenol

T-P

T-N

Sample

Items

* : Mineral oil** : Oil and fat of animals and plants

Quality of wastewater satisfies the environmental standard and regulation


Carbonation process for capsulation

1. CO2 diffusion2. Permeation CO2 to solid waste3. Dissolution of CO2(g)(CO2(aq))4. Hydration of CO2(aq) to H2CO3.5. Ionization of H2CO3(pH 8)6. Decomposition of C3S and C2S7. Nucleation of CaCO3 8. Precipitation of Calcite, vaterite9. Secondary carbonation(S-H, CaCO3 등)

Waste

Gas phase

Pore fluid

Solid phases CaCO3

CO2

1

8

9

6

Calciumsilicate

23 4

5

7

SH

Increase of volume/gravity : Ca(OH)2 + CO2 CaCO3 + H2O : 11.8% (Ca(OH)2 gravity(volume) : 2.24g/mol(33.0ml),CaCO3 gravity(volume) : 2.71(36.9ml)

Decrease of porosity, enhancement of strength : formation of C-S-Hgel, Calcite, ettringite

Formation of stable heavy metal compounds- Pb : formation of PbCO3- Cd : formation of hydroxicarbonates- Ni, Co : substitution of Ca in C-S-H- Ba : formation of BaCO3, BaSO4

CO2 diffusion

Carbonated zone

Unaltered wasteform

Heavy metals

Heavy metals

Carbonation process

Capsulation effect : immobilization of heavy metals

Decrease of pH : pH of lowest solubility for metal hydroxides(pH 8-9.5)

Before carbonation

After carbonation


Chemical composition of bottom ash

43

35

33

24

22

28

12

Cd

137

135

167

145

171

133

112

Ni

985

1075

1202

1412

1849

880

618

Pb

3941602Under 0.15

37818180.15-0.3

48925920.3-0.6

44222990.6-1.18

49635111.18-2.36

32725922.36-4.75

3332938Over 4.75

CrCu

Content of heavy metals (mg/kg)size (mm)

ppmSize (mm)

11.7422171496184935114.350.64.5517.41.18-2.36

pHCdNiCrPbCuNa(%)Zn(%)Al(%) Ca(%)

The content of Cu and Pb in bottom ash

Chemical composition and pH in fresh and carbonated bottom ash


Carbonation reactorReactor of carbonation process

• CO2 flow rate: 1.0 L/min• Water content : 20%

• Liquid/Solid: 10• CO2 flow rate: 1.0 L/min

Condition of wet carbonation

Condition of dry carbonation

• Dry reactor• Wet reactor

• Dry reactor• Wet reactor

• CO2 gas

• Gas flowmeter


Leaching amount of Heavy metals & pH according to wet/dry carbonation

9.027.9611.74pH

<0.01<0.011.54(3.0)Pb (ppm)

<0.010.013.26(3.0) Cu (ppm)

bottom ash after dry carbonation

bottom ash after wet carbonation

fresh bottom ash(St. Limited)

Leaching amounts of Cu and Pb decrease with the wet/dry carbonation

pH of MSWI bottom ash also decreases via the wet/dry carbonation


0.0001540.0004010.00046pore size (cm3/g)

0.33170.75870.1047volume (m2/g)

2.38923.52691.2233BET surface area (m2/g)

bottom ash after dry carbonation

bottom ash after wet carbonationfresh bottom ash

Change in surface area, volume, and pore Size of MSWI bottom ash

via wet/dry carbonation

Surface area, and volume increase with the wet/dry carbonation

Pore size decreases via the wet/dry carbonation

In particular, the pore size is drastically decreased by dry carbonation


Surface Analysis of MSWI bottom ash with SEM

without carbonation with wet carbonation with dry carbonation

•Products (Calcium carboantes)

•Capsulation effect : immobilization of heavy metals• Wet carbonation < Dry carbonation

Carbonated zoneUnaltered wasteform

Heavy metals

Heavy metals


Stability of Heavy metals

Wet carbonation system with dry carbonation

• Carbonation process effects the pH of solution : 11.9 →7.9

• Change in solubility of Cu and Pb• Leaching amounts of Cu and Pb decrease

• Carbonation process forms carbonates on the surface of MSWI bottom ash

• Capsulation effect• Leaching amounts of Cu and Pb decrease

A Long term stability

Wet carbonation < Dry carbonation


Stabilization of heavy metalsStable properties

WeatheringProblems in recycling of bottom ash

• leaching of Cu, Pb, Cd

• instable physical properties(expansion)

• high chloride content

Need of long period for 3Need of long period for 3--6months6monthsLack of stockpileLack of stockpileLow effect of chloride removalLow effect of chloride removal

Pretreatment using in U.S and European countries

--Stabilization of heavyStabilization of heavymetalsmetals

-- Stable propertiesStable properties

--Shortening of stabilizationShortening of stabilizationperiod period

--chloride removalchloride removal

Weathering effect

CO2 gas

Developing technology


1

2 3

1

2 3

rotation type3

agitator type2treatment of wastewater1

Pilot scale(60L)


Lay-out of pilot plant

Magnetic Magnetic separatorseparator FeedFeed

hopperhopper

NonNon--ferrousferrousseparatorseparator

RotaryRotarykilnkiln

Coarse aggregate siloCoarse aggregate silo

Fine aggregate siloFine aggregate silo

VibratingVibratingscreenscreen

VibratingVibratingscreenscreen

FeedFeedhopperhopper

IncinerationIncinerationplantplant

TrommelTrommel

WastewaterWastewatertreatmenttreatment

Equipment for Fixation ofEquipment for Fixation ofheavy metals & Removal of heavy metals & Removal of ClCl

Capacity : 100kg/hr


• Clinkering Reaction • Hydration Reaction

Solidification of Heavy metals in Cement Process

Solidification of Heavy metals in Cement industrySolidification of Heavy metals in Cement industry

Future works of emerging technologies of recycling for inorganic wastes


Clinkering Reaction

2CaCO3+CA→C3A+CO22CaCO3+SiO2→C2S+CO2CaCO3→CaO+CO2

2CaO+SiO2→C2S CaO+C2S →C3S2CaO+C2F→C4AF

Breakdown of clays and iron ore350 ∼ 800 ℃

Carbonation of SiO2+CaO900 ∼ 1200 ℃

Carbonate dissociation800 ∼ 1000 ℃

Release of SiO2 Al2O3 of clays700 ∼ 900 ℃

Liq. formation

1200 ∼ 1280 ℃

C3S formation

1300 ∼ 1380 ℃

Kaoline+CaCO3 →2C2S+CA+H2O+5CO22CaCO3+Fe2O3 →C2F+CO2

▶ C3S : Tricalcium Silicate- Alite(Ca0.98 Mg0.01Al0.0067 Fe0.0033)3(Si0.97Al0.03)O5

▶ C2S : Dicalcium Silicate- BeliteCa2 Fe0.05Al0.05Si0.90O3.95

▶ C3A : Aluminate PhaseK0.03Na0.06Ca2.76Mg0.08Ti0.01)(Fe0.22Al1.60Si0.18)O6

▶ C4AF : Ferrite Phase- CeliteCa2AlFe0.6Mg0.2Si0.15Ti0.05O5

■ Main minerals of clinker

■ Clinkering reaction in kiln


Tricalcium silicate (Alite)

Solidification of heavy metals in Clinkers

(a) (b)

Substitution of Si4+ ion by Ti4+ in tetrahedral site [B. V. volkonskkii, et al., Tsement 6 (1974) 17-19]

Substitution of Zn2+ for Ca2+ site[I. Odler et al., J. Am. Ceram. Soc., 63 (1980) 519-522]

Substitution of Cr3+ for Ca2+ site[A. I. Boykova, Dokl. Chem. Techonl., 156 [6] (1964) 90 -92]

Twin Plane 100

Twin

Pla

ne 1

00

C

a

Calcium silicate networks retain large amount of Cd, Pb, Cr and Zn[M. A. Trezza et al., Cem. Con. Res. 30 (2000) 137-144]

Dicalcium silicate (Blite)

: Ca106Mg2(Na0.25K0.25Fe0.5)(Al2Si34)O180 : Ca87MgAlFe(Na0.25K0.25)(Al3Si42)O180

Alite containing small amounts of iron, magnesium, potassium, sodium, aluminum and titanium occurs in Portland cement

BilteBilte containing small amounts of magnesium, aluminum, iron, magnesium, aluminum, iron, sodium sodium and potassiumpotassium occurs in Portland cement clinker


Result of EDX experiment

MgO

AlCa

SCuCr PbZn

Mg

MgCr

Cr

Ca

Si

CrZn

Al

Ca

Fe

4CaO4CaO··3Al3Al22OO33··SOSO33

2CaO·SiO2

44CaOCaO··AlAl22OO33··FeFe22OO33


950 1000 1050 1100 1150 1200 1250 1300 1350 1400

0

100

200

300

400

500

600

700

800

900

1000

Res

idua

l Qua

ntity

(ppm

)Burning Temperture(oC)

Cu Zn Cr Pb

Changes in crystal structure via substitution of each heavy metal

23.0 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 24.0 24.1 24.2 24.3

Ca4Al6CrO16

1350oC

1300oC

1200oC

1100oC

2θ

1000oC

Ca4Al6SO16

CSA-CrCSA-Cr

Changes of interplanar spacingChanges of interplanar spacing

23.0 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 24.0 24.1 24.2 24.3

2θ

1350oC

1300oC

1200oC

1100oC

1000oC

23.0 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 24.0 24.1 24.2 24.3

2θ

1350oC

1300oC

1200oC

1100oC

1000oC

23.0 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 24.0 24.1 24.2 24.3

2θ

1350oC

1300oC

1200oC

1100oC

1000oC

CSA-CuCSA-Cu

CSA-ZnCSA-Zn CSA-PbCSA-Pb

950 1000 1050 1100 1150 1200 1250 1300 1350 1400

3.736

3.738

3.740

3.742

3.744

3.746

3.748

3.750

3.752

3.754

3.756

3.758

3.760

3.762

CSA-Main CSA-Cr CSA-Cu CSA-Zn CSA-Pb

d Kα1

Burning Temperture (0C)

• Especially, the change in 211 plane• As addition of heavy metal, the crystal structure of CSA was slightly distorted• In case of Pb is added, a big change at 1,100oC • Crystal shrinkage occurred by the vaporization of Pb at 1,100oC.


Ettringite & Tobermorite (C-S-H)

EttringiteEttringite[3CaO[3CaO••AlAl22OO33••3CaSO3CaSO44••32H32H22O]O]

•• 3CaO 3CaO •• AlAl22OO33 (C(C33A)A)

•• 4CaO 4CaO •• AlAl22OO33 •• FeFe22OO33 (C(C44AF)AF)

•• 3CaO 3CaO •• SiOSiO22 (C(C33S)S)

•• 2CaO 2CaO •• SiOSiO22 (C(C22S)S)TobermoriteTobermorite

[ 5CaO[ 5CaO••6SiO6SiO22••5H5H22O]O]+ + nHnH22OO

+ CaSO+ CaSO44 + + nHnH22OO

Clinker in OPC

4CaO • 3 Al2O3 • SO3 (CSA)

In this research, chose the calcium sulfoaluminate, because it can produce ettringite by self-hydration reaction.


EttringiteEttringite [ 3CaO[ 3CaO••AlAl22OO33 •• 3CaSO3CaSO44 •• 32H32H22O]O]

Ca/Ca/SiSi ratio increaseratio increase

Substitution of Heavy metal for interlayer Ca2+ site: Cr, Pb, Ba etc.

CaCa--O sheet : sevenfoldO sheet : sevenfold--coordinated Cacoordinated Ca--O polyhedronO polyhedron

Interlayer CaInterlayer Ca2+2+BridgingBridging SiSi

(A) (B) (C)

tetrahedrontetrahedronPairedPaired SiSi tetrahedrontetrahedron

Solidification of Heavy Metals in hydrates; Ettringite & Tobermorite (C-S-H)

Substitution of SO4

2- ion by CrO42- or SeO4

2-

in tetrahedral site

Substitution of Al3+ ion by Cr3+ in Octahedral site

a column structure

with sheet structure

However, it do not make completely fixation because C-S-H itself is known as very unstable hydrates.

Structure of ettringite & Substitution of heavy metals

The crystals have two distinct structural components:Columns, {Ca6[Al(OH)6]2 24H2O}6+ , and Channels, {(SO4)3 2H2O}6 -

Channel structure (Channel structure (intercolunmnintercolunmn))Substitution ofSubstitution of SOSO44

22-- ion byion by CrOCrO4422-- , , AsOAsO44

33--oror SeOSeO4422--

in tetrahedral site in tetrahedral site

Column structure Column structure Substitution of Substitution of AlAl3+3+ ion by ion by CrCr+3+3, Ni, Ni+3+3,, MnMn+3+3 or in octahedral siteor in octahedral siteSubstitution of Substitution of CaCa2+2+ion byion by PbPb+2+2,Cd,Cd2+2+, Co, Co+3+3 or in or in polyhedtralpolyhedtral sitesite

To extent the immobilization potential of ettringite in the field under specific conditions

The degree of the substitution of oxyanions into the ettringite structure depends largely on competing effects between oxyanions

competing ion effect

Synthesis of CrIII or VI-Ettringite6Ca(OH)2 + Al2(SO4)3 + 36H2O → Ca6[Al(OH)6]2(SO4)3 26H2O

Leaching test

Sonic horn

Ultrasonic transducerSt

ainl

ess t

ip

Ca2+ OH-

Al 3+ SO42-

H+ OH-

Al 3+

SO42-

H+

OH-

Ca2+ OH-

H+ OH-Al 3+

SO42-

Leaching test

Sonic horn

Ultrasonic transducer

Stai

nles

s tip

Ca2+ OH-

Al 3+ SO42-

H+ OH-

Al 3+

SOSO442-

H+

OH-

Ca2+ OH-

H+ OH-Al 3+

SO42-

In distilled water with Cr In distilled water with Cr 3+3+ In distilled water with Cr In distilled water with Cr 6+6+

Cr3+

Cr3+Cr3+

Cr3+Cr3+

Cr3+

Cr6+

Competing ionsCompeting ions

Cr6+

Cr6+ Cr6+

Cr6+

Cr6+Cr6+

or + 0.003 CrO3

+ 0.005 CrCl3

Ca6[Cr(OH)6]2(SO4)3 26H2O Ca6[Al(OH)6]2(CrO4)3 26H2O

Cr3+ Al3+ CrO42- SO4

2-

+ Cr: 300mg/kg+ Cr: 300mg/kg

XRD pattern of productsXRD pattern of products

5 10 15 20 25 30 35 40 45 50 55 60

2 theta/degree

ettringite Cr(III)-ettringite

Cr(VI)-ettringite

▼

▼

Ettringite is the main phase in the products of all synthesis systems.

But, in the case containing Cr(III) monosulfate formed together with ettingite.

Result (SEM)

In distilled water with Cr 3+ In distilled water with Cr 6+In distilled water

EttringiteEttringite

Ettringite

Monosulfate

Ettringite is only shown with the column-crystalline In distilled water and in the solution containing Cr(VI).

But monosuflate with plate shape is found to be formed together with that of ettringite in solution containing Cr(III).

This results well agree with that of XRD measurement.

Quantity of chrome ion substitutedQuantity of chrome ion substituted

240300CrO3 (Cr6+)

0.26300CrCl3 (Cr3+)

Residual amount of chrome ion(mg/kg)

Dosage amount of chrome ion(mg/Kg)

Cr3+ is almost substituted during the reaction, but in case of Cr6+, a large amount of chrome ions are detected in solution after reaction.

This results means that a fixed quantity of Cr6+ is only substituted into ettringite crystal, and most of them did not participate into the reaction.

Result (FTResult (FT--IR)IR)

4000 3500 3000 2500 2000 1500 10000

10

20

30

40

50

60

70

80

90

Tr

ansm

ittan

ce(%

)

Wavenumber(cm-1)

ettringite Cr(III) ettringite Cr(VI) ettringite

Free OHSO4

2-O-H stretch

O-H bend

Al-O-H bending

Cr-O stretch

broad, symmetric CO2- stretching vibration

Cr(VI) (CrO4): 886cm-1, 867-902cm-1

Cr(III) : 750-850cm-1, 798cm-1

FT-IR spectrum of ettringitesynthesized in solution containing Cr6+ are very similar to that ofettringite in distilled water.

Especially, absorbance peak attributed to CrO4 vibration did not shown at 867-902cm-1.

But the absorbance peak at 785.325 closely matched the peak attribute to Cr3+-compounds in the spectrum of ettringite synthesized in solution with CrCl3.

`

6Ca(OH)2 + Al2(SO4)3 + 36H2O → Ca6[Al(OH)6]2(SO4)3 26H2O

6Ca(OH)2 + Al2(SO4)3 + mCrCl3 + 36H2O

→ (1-n){Ca6[(Al(1-m/2)·Crm/2(1-n))(OH)6]2(SO4)3 26H2O}+n(2-m)Al3++mCl2-+6nCa2++3n(SO4)2-+mH2O

→ (1-n){Ca6[(Al(1-m)·Crm/2(1-n))(OH)6]2(SO4)3 26H2O}+n{Ca4[Al·(OH)6]2(SO4)· 6H2O}+2nCaSO4+2nmAl(OH)3+mCl2-

6Ca(OH)2 + Al2(SO4)3 + nCrO3 + 36H2O

→ (1-m)Ca6[Al(OH)6]2(SO4)3 26H2O + mCa6[Al(OH)6]2(CrO4)3 26H2O + n-mCr6++(OH)-+ H2O

Ettringite Monosulfate

Ettringite

In distilled water

In solution with Cr(III)

In solution with Cr(VI)

n<<1

m: not much

Solidification/stabilization of hazardous materials for … · 2006-10-30 ·...

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