Characteristics of Solid waste – Residues Gardanne Coal Power Plant

Geochemistry, Petrography , Mineralogy

Naze - Nancy Masalehdani & Jean-Luc Potdevin

Naze-Nancy.Masalehdani@univ-lille1.fr

• Exploit two Chimney-Units: T4 &T5

o T4: CFBC, 268 MWe, known to combust high Sulphur, low rank coal

o T5: 600 MWe, combust pulverized coal

• Total capacity: 868 MWe

• Situated in: Gardanne - Meyreuil

• Owned and operated: by SNET

• Types of Fuel:

o T4: Petroleum coke (Pet-coke) & Imported coal (e.g.S- Africa …)

o T5: Imported coal

• Sorbent (SB): Limeston to trap the acidic SO2 before the atmospheric

emission

• Temperature of combustion: T4 ≈ 850°C, T5 ≥1000°C

• Residues:

o Fly Ash (FA) resulting from dust filtration of the flue gas

o Bottom Ash (BA) extracting from the bottom of the boiler

Introduction

Provence-Gardanne Thermal Power Plant

• Dumping waste location: « Terril Bramefan »

Waste heap

Stockage of Ash

Area: ≈ 76ha

Source:www.asn.fr

• X-Ray Diffraction (XRD)

• Optical microscope (OM)

• Scanning Electron Microscope -energy-dispersive spectroscopy (SEM-EDS)

• Electron Probe Micro Analysis-wavelength dispersion spectrometry(EMPA-WDS)

• Raman spectroscopy (RS)

• Chemical analysis (ICP-FIMS-INAA)

Objectives Principal: Investigate characteristics of Solid waste - Residues

“Petrology, Mineralogy & Chemical compositions”

Divers: Chemical composition of Pet-Coke

Methodes

Results

Unit T4

Unit T5

Fly ash, fine material

transported from the

combustion chamber by

exhaust gases

(i.e. dust filtration of the

flue gas).

Bottom ash a coarse, granular,

incombustible by-product collected

from the bottom of boiler.

Combustion by-products from T4CFBC and T5

A B C D A: S-African Coal

B: Colombian Coal

C: Pet-Coke

D: Limestone

Imported Coal: S-African Coal (example)

Proximate analysis

Mineral Matter: South African coals have relatively high amount of clay

minerals (illite and kaolinite), quartz, sulphides , carbonates in the form of

dolomite and siderite as the minor minerals.

SEM-EDS

S: 19,33 % C: 80,67 %

• Is a solid by-product of heavy oil refining process

• Has high heat (carbon-fuel) & low ash content

• Contains relatively high sulphur ± trace metals

• Is cheaper than coal

• Should be co-fired with coal in coal-fired plants

SEM-SE

Components of Pet-Coke: Gardanne Thermal Power Plant

P

E

T

C

O

K

E

Chemical Composition: Pet-Coke, Gardanne Thermal Power Plant

SiO2 Al2O3 CaO Na2O K2O Fe2O3 MgO MnO P2O5 TiO2 N C S H LOI

1.57 0.98 0.24 0.02 0.14 0.44 0.07 0.018 0.05 0.059 1.27 73.93 5.50 3.46 96.00

Major elements (wt%)

As Ba Be Bi Cd Ce Co Cr Cs Cu Dy Er Eu Ga Gd

ID 40.30 ID ID ID 5.39 2.05 6.00 1.23 10.40 3.08 0.15 0.08 3.18 0.35

Trace elements (ppm)

Ge Hf Hg Ho In La Lu Mo Nb Nd Ni Pb Pr Rb Sb

ID 0.21 0.033 0.06 0.11 8.47 0.02 17.3 0.63 2.09 252 2.74 0.65 6.65 1.76

Se Sm Sn Sr Ta Tb Th Tm U V W Y Yb Zn Zr

0.20 0.46 0.57 11.1 0.05 0.05 1.09 0.02 0.36 1395 0.33 1.69 0.15 ID 7.54

Minerals

XRD RM OM SEM-EDS EPMA-WDS

FA4 BA4 FA5 BA5

Anhydrite CaSO4 Lime CaO

Calcite CaCO3 Dolomite

MgCa(CO3)2

√

√

√

√

√

√

√

√

√ √

√

√

√

√

√

√

√ √ √

√ √ √ √ √ √

√

Hematite Fe2O3 Maghemite Fe2O3

Magnetite Fe3O4

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√ √ √

√

√

Quartz SiO2 Tridymite SiO2 Mullite Al6Si2O13 Anorthite

CaAl2Si2O8

√

√

√

√

√ √ √

√

√

√

√ √ √ √ √

√

√

Barite BaSO4

Brookite TiO2 Anatase TiO2

√

√

√

√

√ √ √

√ √

Al-Si-Oxide

Ca-Al-Si-Oxide

√

√ √

√ √ √

√

Compounds

Al-P-Si-Ba-Ca

Si-Na-Ca-Mg

√

√

√

√

√ √ √

√

Glass √ √ √ √

Identified mineral phases in Fly and Bottom Ashes

Methods Samples & Units

Characteristics of Solid Residues:Sorbent «LM T4»

SiO2 Al2O3 CaO Na2O K2O Fe2O3 MgO MnO P2O5 TiO2 N C S H LOI

3.19 1.04 53.92 0.01 0.11 0.42 0.54 0.015 0.04 0.08 ND 11.35 ND 0.17 45.56

As Ba

Ce

Co Cr Cs Dy Er Eu Ga Gd Hf Hg Ho

1.29 33.8 3.85 1.23 6.1 0.63 0.291 0.144 0.072 1.74 0.28 0.31 0.008 0.05

La Lu Mo Nb Nd pb Pr Rb Se Sm Sr Ta Tb

2.08 0.02 1.37 0.91 1.27 1.65 0.44 6.02 0.09 0.34 340 0.09 0.05

Th Tm U V Y Yb Zr

0.64 0.23 1.73 7.5 1.63 0.144 11.0

Trace elements (ppm)

Major elements (wt%)

XRD Patterns

Calcite (CaCO3)

Quartz (SiO2)

OM-CPL

Characteristics of Solid Residues: Fly Ash « T4 »

H

L

AlSi-oxide

H

Q

Ba

L

AlSi-oxide

Q

Al- P-Si-Ba-Ca-compound

L An

Lime > Anhydrite

XRD Patterns: Anhydrite, Lime, Quartz, Hematite

Characteristics of Solid Residues: Bottom Ash«T4»

A

L

Q

L Al-Si-oxide

Bottom Ash from unit T4 has relatively homogenous mineralisation. Concentration of

Anhydrite is being higher than Lime. Mineral zoning occurs between Anhydrite & Lime

as observed in Fly ash. Amorphous AlSi-Oxide (? metakaolinite) occurs as small

isolated phase or within Anhydrite -Lime grains.

L

Si-Na-Ca-Mg

compound

Al-Ca-Si-Oxide

Anhydrite > Lime

Wt

% SiO2 Al2O3 CaO Na2O K2O Fe2O3 MgO MnO P2O5 TiO2 N C S H LOI

FA 26.70 14.40 30.37 0.12 0.54 2.62 1.30 0.035 0.75 0.74 0.10 7.13 4.59 0.28 12.89

BA 13.74 6.53 50.99 0.06

0.26 1.39 0.99 0.03 0.30 0.47

ND 3.14 6.46 0.46 5.56

ICPS-MS Analysis: Residues from « T4 »

ppm As Ba Be Bi Cd Ce Co Cr Cs Cu Dy Er Eu Ga

FA

7.18 836 5.45 1.65 0.38 113 19.6 94.1 4.30 40.9 7.44 4.20 1.69 29.0

BA 8.09 489 4.45 0.67 0.18 66.0 17.3 97.5 2.22 14.7 4.15 2.30 0.99 20.40

ppm Gd Ge Hf Hg Ho In La Lu Mo Nb Nd Ni Pb

FA 8.06 6.61 6.30 0.441 1.48 0.19 64.70 0.61 17.0 16.30 47.2 275 36.5

BA 4.28 6.32 3.40 0.0015

0.83 0.14 37.5 0.35 17.4 10.60 26.6 300 4.49

ppm

Pr Rb Sb Se Sm Sn Sr Ta Tb Th Tm U V W

FA

12.6 29.1 2.38 3.8 9.05 4.37 1214 1.51 1.23 20.2 0.63 7.70 960 3.60

BA 7.38 14.2 2.10 0.08 5.05 4.04 909 0.94 0.67 12.4 0.36 5.98 1240 2.30

ppm Y Yb Zn Zr

FA 46.7 4.15 29.3 243

BA 24.9 2.36 36.8 135

FA: Fly Ash

BA: Bottom Ash

Characteristics of Solid Residues: Fly Ash « T5 »

Spherical texture, Fly Ash from Unit T5 contains high temperature T≥ 1000°C

mineral phases, more Si-bearing minerals and Iron oxides compared to T4 Fly

Ash. Quartz and Tridymite (both SiO2) occur together. Mineral Mullite

Al6Si2O13 was also identified. Lesser amounts of Lime and Anhydrite were

observed.

Mh

Mh

AlSi-oxide

Q

L

Characteristics of Solid Residues: Bottom Ash « T5 » OM-CPL

SEM-BSE

SEM-EDS

Microphotographs showing hoste Magnetite

(Fe3O4) crystallised in glass matrix. Quenched

texture indicates rapid crystallisation from melt.

Glass composition is: Al-Si-Na-silicate.

ICPS-MS Analysis: Residues from T5

Wt

% SiO2 Al2O3 CaO Na2O K2O Fe2O3 MgO MnO P2O5 TiO2 N C S H LOI

FA 52.84 24.06 5.21 0.63 2.03 6.74 1.83 0.08 0.67 1.11

ND

3.81 0.43

0.10

5.53

BA 45.89 15.20 8.58 0.42 1.13 9.50 1.93 0.15 0.27 0.62 0,19 10.49 0.60 0.69 16.52

ppm As Ba Be Bi Cd Ce Co Cr Cs Cu Dy Er Eu Ga

FA 39.0 1305 8.84 1.95 1.53 143 34.6 205 11.5 81.6 9.92 5.59 2.54 48.0

BA 13.7 682 3.65 0.28 0.91 63.9 16.5 289 4.92 66.1 5.11 2.86 1.27 13.9

ppm Gd Ge Hf Hg Ho In La Lu Mo Nb Nd Ni Pb

FA 10.8 18.6 7.34 0.199 1.99 0.21 77.3 0.88 18.2 20.8 63.8 128 57.4

BA 5.43 5.30 4.41 0.582

1.02 ID 33.9 0.48 13.8 11.2 29.0 142 15.4

ppm

Pr Rb Sb Se Sm Sn Sr Ta Tb Th Tm U V W

FA 17.1 97.8 14.4 21 12.4 7.17 945 1.89 1.70 26.3 0.85 10.2 312 7.57

BA 7.73 49.4 3.65 2.2 5.99 2.49 480 0.98 0.87 11.9 0.46 4.79 429 2.23

ppm Y Yb Zn Zr

FA 62.5 5.77 163 284

BA 31.8 3.06 155 171

FA: Fly Ash

BA: Bottom Ash

(Kaolinite) Al2Si2O5(OH)4

39.50 % Al2O3

46.55 % SiO2

13.96 % H2O

100 – 200 °C

Loss of H2O

Al2Si2O5 + H2O 500 – 600 °C

Dehydroxylated

Endothermic process

Metakaolinite

39.50 % Al2O3

46.55 % SiO2

Process of mineral formation during Ashing

* AlSi-Oxide found in Flay Ash and Bottom Ash from Unit T4 is an amorphous phase i.e.

metakaolinite which was not decomposed into Al-Si-spinel because the combustion

temperature remained T≤ 850°C.

EPMA - Result: Al2O3 35.83%, SiO2 45.26%, with 1.34% K2O, 0.54% CaO, 3.19%TiO2

as impurities.

** Al-Ca-Si-Oxide found in Flay Ash and Bottom Ash from Unit T4 is an amorphous

phase. A reaction of decomposed clays with lime (CaO) and partly quartz (SiO2) to form

Al-Si-Oxide (? pre-formation of Gehlenite) at 820-850°C.

EPMA - Result: Al2O3 18.48%, SiO2 26.7%,CaO 28.86%, with 1.98% FeO and 0.93%

TiO2 as impurities.

*** Al-P-Si-Ba-Ca-Compound in Fly Ashes (T4 & T5) and Bottom Ash (T4) could be a

mixed amorphous phase (Apatite + Lime + Al-Silicate ± Barite)

T5 Fly Ash: Si > Al > Ca

T5 Bottom Ash: Si > Al > Ca

T4 Bottom Ash: Ca >Si >Al

T4 Fly Ash: Ca >Al >Si

Ternary diagram chemical composition (wt%):

Fly and Bottom Ashes

Fly & Bottom Ashes from T4: produced from burning bituminous coals

& Pet-Coke have Sulfo-Calcic

compositions, contain lime (CaO) and

Anhydrite (CaSO4)

Fly & Bottom Ashes from T5: produced from burning bituminous coals

have Silico-Aluminous compositions,

contain higher concentration of Al-si-

oxides

Wt

%

Residues

• Unit T4: Higher sulphur concentration in residues confirmes the presence

of Anhydrite (CaSO4) • Unit T5:

* Higher iron concentration in residues confirmes Magnetite (Fe3O4), Hematite and/or Maghemite (Fe2O3) as principal Fe-Oxides

* Higher concentration of Carbon in bottom ash is related to presence of

Calcite (CaCO3), and probably to ± char (i.e.unburnt carbon)

Concentration of Sulphur,Carbon & Iron in Residues

0

2

4

6

8

10

12

T4 FA T5 FA T4 BA T5 BA

S

C

Fe

Elements

pp

m

ICP-FIMS-INAA Analysis

Concentration of Trace elements in Residues p

pb

0

200

400

600

800

1000

1200

1400

1600

As Cu Cr Ni Sr V Zn Pb

T4 FAT5 FAT4 BAT5 BACP

0

50

100

150

200

250

300

350

400

450

500

T4 FA T5 FA T4 BA T5 BA CP LM

Hg

pp

m

0

5

10

15

20

25

T4FA T5FA T4BA T5BA CP LM

Se

The Pet-Coke-Coal residues (Ashes) produced by

Provence-Gardanne Thermal Power Plant are:

enriched in Vanadium and Nickel

• V & Ni compounds are not toxic as Hg, Cd, As, Pb

or other «heavy metals».

• Most health problems related to Nickel deal with skin

& respiratory exposure (Nielsen,1977, p.134).

• The most common health problems associated with

Vanadium (if present as V2O5) exposure result from

inhalation e.g. coughing, bronchitis, eyes, nose & throat

irritation (Waters, 1977, p.148, pp.160-161).

The ash chemical composition for both Fly ash and

Bottom ash from the particulate control device at

Provence-Gardanne Thermal Power Plant directly

arises from the fuel characteristics

& sorbent composition They result:

1. from the chemical composition of the inorganic fraction

of the fuel,

2. from the fuel sulphur content and the SO2 removal rate.

Thank you for your attention

Conclusions