HELSINKI UNIVERSITY OF TECHNOLOGY ENE-47.153 Halogens

HELSINKI UNIVERSITY OF TECHNOLOGY ENE-47.153

Halogens, dioxins/Halogens, dioxins/furansfurans

•• Halogen compounds in fuels and fuel/flue gasesHalogen compounds in fuels and fuel/flue gases

•• Chlorine-related corrosionChlorine-related corrosion

•• HCl HCl control in flue gases and fuel gasescontrol in flue gases and fuel gases

•• Dioxins/Dioxins/furansfurans formation and control formation and control

•• Other compounds: HF, Other compounds: HF, HBrHBr, , brominated organobrominated organo-halogens-halogens

see: www.hut.fi/~see: www.hut.fi/~rzevenhorzevenho//gasbookgasbook


Organo-halogen compoundsOrgano-halogen compounds

2,3,7,8 tetrachloro dibenzo - p- dioxin

PCBfuran

2,3,7,8 tetrachlorodibenzo furan

12

34 6

7

89

PCBsPCBs polychlorinated polychlorinated biphenylsbiphenylsPCDDsPCDDs polychlorinated polychlorinated dibenzodioxinsdibenzodioxinsPCDFsPCDFs polychlorinated polychlorinated dibenzofuransdibenzofurans

with bromine: with bromine: PBBsPBBs, , PBDDsPBDDs etc. etc.


Halogens in fossil fuels (mg/kg)Halogens in fossil fuels (mg/kg)(listed as F, Cl, Br)

Coal*, lignite 20 -500 /50-2000/0.5 -90

Light fuel oil -

Peat ~ 500 Heavy fuel oil - / < 20

Estonian oil shale ~2000 Orimulsion™ ~700

Petroleum coke, “petcoke” ~ 300 Natural gas -* Iodine 0.5 - 1.5 mg/kg


HalogensHalogens in in biomassbiomassand wasteand wastestreamsstreams(mg/kg)(mg/kg)

(listed as F, Cl, Br)

Wood(firewood)

0.08 - 0.13 Munical solid waste (MSW) 0.005 - 0.025 /0.05 - 0.25

Bark 0.02 - 0.4 Refuse derived fuel (RDF) 0.001 - 0.07 /0.3 - 0.8

Straw 0.1 - 1.5 Packaging derived fuel (PDF) 0.001 - 0.012 /1 - 4

Landfill gas ~50 ppmw CCl44 Car tyre scrap 500 - 700Auto shredder residue (ASR) 0.5 - 2

Textile ~ 0.25Newsprint paper ~ 0.11 Computer circuit boards

(epoxy or phenolic resins)0.1 - 0.5 /2 - 6

Leather waste 0.7 - 3 Computer monitor housings ~ 0.1 / ~ 2Electric & electronic equip-ment (E&E) waste plastics *

~ 3.5 / ~ 0.9

Sewage sludge 0.03 - 1

Mixed medical waste 1 - 4Polyurethane foam(containing CFC11)

~ 0.7 /~ 8/~ 3

PVC ~ 50 Black liquor solids 0.05 - 0.2* Polymer market mix 1998


Oxidation rate of CO in FBC in presence of Oxidation rate of CO in FBC in presence of HClHCl

0.00001

0.0001

0.001

0.01

0.1

1

0.001 0.01 0.1 1 10 100 1000 10000

HCl in gas ( ppm-v)

CO

oxi

dat

ion

rat

e (m

ol/m

3s)

1100 K1 bar

10% O2 5% CO

10% H2O


Emission standards for halogen compoundsEmission standards for halogen compounds

@ 11 % O22, dryPowerplant

Finland(1990+)

MSWincinerator

Finland(1994)

MSWincinerator

EU(2000)

Powerplant

Germany(1999)

MSWincineratorGermany

(1999)

Wasteincinerator

USA(1995)

HClmg/m³STPSTP

no standard 10 10 50 10 29.1 or99.5% red.

HFmg/m³STPSTP

no standard 1 1 2 1 no standard

PCDD/Fng/m³STPSTP TEQ

no standard 1 0.1 no standard 0.1 9.63


Chlorine-related corrosion #1Chlorine-related corrosion #1

DewpointDewpoint of of hydrochloric acidhydrochloric acid

Corrosion rate by Corrosion rate by HClHCl and Cl and Cl22



Important forImportant forchlorine-relatedchlorine-related

corrosion:corrosion:

HClHCl, Cl, Cl22

NaClNaCl, , KClKCl,,OO22, SO, SO22, H, H22OO

Tube metalsTube metals

TemperatureTemperature



Corrosion rate Corrosion rate versusversus chlorine in coal chlorine in coal


Halogen removalHalogen removalin FGDin FGD

(with forced oxidation)(with forced oxidation)


Removal of Removal of HCl HCl (& HF, (& HF, HBrHBr)) from flue gases from flue gases•• Conventional, at low concentrations:Conventional, at low concentrations:

in wet scrubber for FGD, gives ~70% removal of in wet scrubber for FGD, gives ~70% removal of HClHCl, HF., HF.Disadvantages:Disadvantages:–– dissolution of SOdissolution of SO22 and lime/limestone are inhibited and lime/limestone are inhibited

–– HF and fly ash giveHF and fly ash give AlF AlFxx complexes in FGD complexes in FGD ((InkooInkoo, Finland), Finland)

–– Corrosion, deposits formation upstreamCorrosion, deposits formation upstream

•• More suitable methods:More suitable methods:–– (cold) inject alkali and collect salt particles in filter(cold) inject alkali and collect salt particles in filter

–– (hot) injection of calcium-based (hot) injection of calcium-based sorbent sorbent in upper furnacein upper furnace


3-stage3-stageHClHCl scrubber, scrubber,

producingproducinghydrochlorichydrochloric

acidacid

gives 14-18 % gives 14-18 % HClHCl,,which is furtherwhich is further

processed toprocessed to 30-31% 30-31%

Flue gas fromdust separator

Water

Water

Flue gas toSO2 separator

1st stage

3rd stage

2nd stage

Packing

Packing

Salt solutionto vaporiser

Pump /containerset stage 2

Pump /containerset stage 3


SorbentsSorbents for for HCl HCl, HF,, HF, HBr HBr ( (i.e.i.e. HX) #1 HX) #1

Limestone Limestone CaCOCaCO33 Lime Lime CaOCaO Hydrated lime Ca(OH)Hydrated lime Ca(OH)22

NahcoliteNahcolite NaHCONaHCO33 Soda/Soda/tronatrona NaHCO NaHCO33•Na•Na22COCO33

Melting points of halogen saltsMelting points of halogen salts

NaFNaF:: 988 °C ;988 °C ; NaClNaCl:: 801 °C ;801 °C ; NaBrNaBr:: 755 °C755 °C

CaFCaF22:: 1360 °C ;1360 °C ; CaClCaCl22:: 772 °C ;772 °C ; CaBrCaBr22:: 730 °C730 °C

KF:KF: 858 °C ;858 °C ; KClKCl:: 770 °C ;770 °C ; KBrKBr:: 734 °C734 °C


Sorbents Sorbents for for HClHCl, HF,, HF, HBr HBr ( (i.e.i.e. HX) #2 HX) #2

Potassium salts : high vapour pressures for KF, Potassium salts : high vapour pressures for KF, KClKCl, , KBr KBr


Removal of Removal of HCl HCl and HF from pulverisedand HF from pulverisedcoal combustion flue gas coal combustion flue gas (Illinois, US, 1993)(Illinois, US, 1993)

Chemistry :Chemistry :Ca(OHCa(OH22) ) →→→→ CaO CaO + H+ H22OOCaO CaO + 2 + 2 HCl HCl →→→→ CaCl CaCl22 + H + H22OOCaOCaO + 2 HF + 2 HF →→→→ CaF CaF22 + H + H22OO

Results :Results :HClHCl 63-86% removal,63-86% removal,

from 660 from 660 ppmwppmwHFHF 94-99% removal94-99% removal

from 49 from 49 ppmwppmw

Hydrated lime injected into a coal-firedHydrated lime injected into a coal-firedboiler at Ca/S=1.66, 3%-wt sulphur in fuelboiler at Ca/S=1.66, 3%-wt sulphur in fuel

Injected into upper furnace at ~1250°CInjected into upper furnace at ~1250°C


Halide removal (Halide removal (HClHCl, HF), HF)from IGCC raw fuel gas at ~400°Cfrom IGCC raw fuel gas at ~400°C

Buggenum Buggenum IGCCIGCCHCl HCl ~ 600 ~ 600 ppmppmHF ~ 220 HF ~ 220 ppmppm

Texaco IGCCTexaco IGCCHCl HCl ~ 500 ~ 500 ppmppmHF ~190 HF ~190 ppmppm

for coal, for coal, 0.2 % 0.2 % ClCl, 0.04 % F, 0.04 % F


Removal of Removal of HCl HCl from flue gasfrom flue gaswith various with various sorbentssorbents


Formation of dioxins / Formation of dioxins / furansfurans #1 #1


Formation ofFormation ofdioxins / dioxins / furansfurans #2 #2


“De “De NovoNovo”” dioxins / dioxins / furansfurans formation formationDepends on 5 major factors :Depends on 5 major factors :

1.1. The cooling rate of the flue gas, especially around 300°CThe cooling rate of the flue gas, especially around 300°C2.2. The amount of fly ashThe amount of fly ash3.3. The presence of trace elements, especially Cu and The presence of trace elements, especially Cu and PbPb4.4. The carbon and chlorine content of the fly ashThe carbon and chlorine content of the fly ash5.5. The presence of free oxygenThe presence of free oxygen

Radical reactionsRadical reactions ClCl + OH + OH →→→→ HCl HCl + O,+ O, OH + H OH + H →→→→ H H22OOare competing withare competing with CO + OH CO + OH →→→→ CO CO22 + H + Hgiving apparently lower giving apparently lower stoichiometrystoichiometry, giving more soot and , giving more soot and CCxxHHyy

Deacon reaction :Deacon reaction : 2HCl + 2HCl + ½½ O O22 <=> Cl <=> Cl22 + H + H22OOcatalysed by Cu, catalysed by Cu, PbPb, , SnSn, .... ; reaction equilibrium to Cl, .... ; reaction equilibrium to Cl22 below ~500 below ~500°°CC

ClCl22 + O + O22 + + CCxxHHyy + time @ 250-350+ time @ 250-350°°C C →→→→ PCDDsPCDDs/Fs/Fs


Equivalence schemes for PCDD/FsEquivalence schemes for PCDD/FsDioxin I- TEF Furan I - TEF

2,3,7,8-TCDD 1 2,3,7,8-TCDF 0.11,2,3,7,8-PCDD 0.5 1,2,3,7,8-PCDF 0.05

1,2,3,4,7,8-HxCDD 0.1 2,3,4,7,8-PCDF 0.51,2,3,6,7,8-HxCDD 0.1 1,2,3,4,7,8-HxCDF 0.11,2,3,7,8,9-HxCDD 0.1 1,2,3,6,7,8-HxCDF 0.1

1,2,3,4,7,8,9-HpCDD 0.01 2,3,4,6,7,8-HxCDF 0.11,2,3,4,6,7,8,9-OCDD 0.001 1,2,3,7,8,9-HxCDF 0.1

1,2,3,4,6,7,8-HpCDF 0.011,2,3,4,7,8,9-HpCDF 0.011,2,3,4,6,7,8,9-OCDF 0.001

International Toxic Equivalence Factors (I-TEF) (NATO, 1988) standardize the toxicity of thedioxins and furans, to derive a toxic equivalence as 2,3,7,8-TCDD. The I-TEF for the dioxinsand furans without chlorine atoms at the 2, 3, 7, and 8 positions is zero.


Rate of Rate of de de novonovo PCDD/F formationPCDD/F formation


Effect of calcium-based Effect of calcium-based sorbentssorbents on onPCDD/F release from an FB waste PCDD/F release from an FB waste combustorcombustor


Emission control for PCDD/FsEmission control for PCDD/Fs•• Carbon injection*Carbon injection*

•• Fixed bed carbon absorption + SNCRFixed bed carbon absorption + SNCR

•• SNCR + carbon injection*SNCR + carbon injection*

•• Lime / char adsorptionLime / char adsorption

•• SCR catalytic oxidationSCR catalytic oxidation

•• SCR catalytic oxidation + carbon injection*SCR catalytic oxidation + carbon injection*

* collected downstream in (a separate) dust control system* collected downstream in (a separate) dust control system

also for PCBs, also for PCBs, brominated brominated compounds (compounds (PBBsPBBs, PBDD/Fs), PBDD/Fs)


Dioxins/Dioxins/furans furans control for waste incineratorscontrol for waste incinerators(MSW = municipal solid waste)(MSW = municipal solid waste)

process PCDD/Fs fromfurnace ng/m³STPSTP

gas clean-upsystem

PCDD/Fs removalefficiency %

5 incinerators for RDFor MSW

43 - 2157 wet scrubber +fabric filter

> 95.7

3 incinerators forMSW

28 - 783 SCR + wet scrubber+ fabric filter

87.7 - 99.6

pilot incinerator forMSW

87 - 2277 sorbent injection +fabric filter

> 99.55

MSW incinerator 170 wet scrubber + ESP 64.3


PCDD/F removal by a bag filter :PCDD/F removal by a bag filter :effect of entrance temperatureeffect of entrance temperature


Other halogens #1:Other halogens #1:control of HF + control of HF + HClHCl

Process* Temperature at outlet EEC

HF removal %

HCl removal%

dry sorbent injection + fabric filter 160 - 180 98 80

spray dryer absorber + ESP 140 - 160 99 > 95

spray dryer absorber + fabric filter 140 - 160 99 > 95spray dryer absorber + dry sorbent

injection + ESP or fabric filter~ 200 99 > 95

ESP + wet scrubber 104 - 122 99 > 95

spray dryer + west scrubber + ESP or fabric filter

104 - 122 99 > 95

* sorbent = sodium- or calcium- based sorbent


Other halogens #2:Other halogens #2:formation offormation of brominated brominated dioxins/ dioxins/furansfurans

(PBDD/Fs) from PBDE flame (PBDD/Fs) from PBDE flame retardantsretardants

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HELSINKI UNIVERSITY OF TECHNOLOGY ENE-47.153 Halogens