연세대학교 화학공학과 이 태 규 제 4 회 광촉매 연구회 2004 년 2 월 26 일...

연세대학교 화학공학과이 태 규

제 4 회 광촉매 연구회2004 년 2 월 26 일

Comparison of Mercury Removal Efficiency from a Simulated Exhaust Gas by Several Types of TiO2 under Variou

s Light Sources

Mercury

• Toxic properties

• High volatility

• Tendency to bio-accumulate

IntroductionIntroductionIntroductionIntroduction

Emission resources

• 80% of the total emission from the combustors (Coal Combustors, Waste Incinerators, etc.)

Hg Emissions Control MethodsHg Emissions Control Methods


• Oxidized mercury can be captured relatively easily because of its high solubility in weak acidic solution

• Elemental mercury is difficult to capture

• Unusual non-reactivity compared to other metals– 5d106s2 closed shell electronic structure for Hg atom– extremely slow or no oxidation at high temperatures

– possible oxidation by strong oxidants (NO2, Cl2)

=> most widely used

Activated Carbon

Hg removal by adsorbents


Photocatalyst TiO2

high removal efficiency for low concentrations of toxic compounds

disadvantagedisadvantage

Low applicable temperature range Low regeneration rate & slow adsorption rate

Hg removal under UV

light


- high energy strength- harmful- development of improved photocatalysts activating

under the visible light!!!

UV light

Hg removal using a TiO2

under the fluorescent light

Intermediate

step

Hg capture by TiOHg capture by TiO22

TheoryTheoryTheoryTheory

Hg TiO2 HgO

OH•

H2O

O2

O2-

Hg HgO

Light

e-

+

+

H+

TiO2(s) + light → TiO2·OH + Hg(g) → TiO2·HgO(complex)

ApparatusApparatus

ExperimentalExperimentalExperimentalExperimental

ParticleFree Air

N2

Oilbath

ElementalMercury

(Hg0)

TemperatureController

MFC

MFC

Mixing

Light Source

TiO2

Filter

HoodOn-line

Hg Analyzer

GlassBead

Ontario- Hydro Method

• UV black lightUV black light

• UV sterilizing lightUV sterilizing light

• fluorescent lightfluorescent light

• blue lightblue light

• UV black lightUV black light

• UV sterilizing lightUV sterilizing light

• fluorescent lightfluorescent light

• blue lightblue light

• pure anatase pure anatase (Ishihara co.)(Ishihara co.)

• P25 P25 (Degussa co.)(Degussa co.)

anatase : rutile = 80 : 20anatase : rutile = 80 : 20

• pure rutile pure rutile (Junsei co.)(Junsei co.)

• pure anatase pure anatase (Ishihara co.)(Ishihara co.)

• P25 P25 (Degussa co.)(Degussa co.)

anatase : rutile = 80 : 20anatase : rutile = 80 : 20

• pure rutile pure rutile (Junsei co.)(Junsei co.)

Light Sources TiO2 Powder


Wave lengthWave length


wave length (nm)

200 300 400 500 600 700 800

co

un

ts

0

1000

2000

3000

4000

5000

blue lightfluorescent lampUV black lightUV sterilizing light

UV-C UV-B UV-A Visible Light Infrared Ray

time (s)

0 1000 2000 3000 4000 5000 6000

Hg

re

mo

va

l e

ffic

ien

cy (

%)

0

20

40

60

80

100

Ishihara (anatase)Degussa (P25)Junsei (rutile)

Off

On

[a] UV black light[a] UV black light

ResultsResultsResultsResults

time (s)

0 1000 2000 3000 4000 5000 6000

Hg

re

mo

va

l e

ffic

ien

cy (

%)

0

20

40

60

80

100


Off

On

[b] UV sterilizing light[b] UV sterilizing light


time (s)

0 1000 2000 3000 4000 5000 6000

Hg

re

mo

va

l e

ffic

ien

cy (%

)

0

20

40

60

80

100


Off

On

[c] fluorescent light[c] fluorescent light


time (s)

0 1000 2000 3000 4000 5000 6000

Hg

re

mo

va

l e

ffic

ien

cy (

%)

0

20

40

60

80

100


Off

On

[d] blue light[d] blue light


Breakthrough ExperimentBreakthrough Experiment


TiO2 activated

carbon

average time to reach 80% of the initial Hg conc.

~ 570 hrs ~ 40 hrs

amount of Hg per gramof adsorbent

~ 48.0 mg ~ 2.5 mg

cost per gram of adsorbent

3~5 원 2~4 원

estimated costper gram of Hg

~ 104.2 원 ~ 1600 원

XRD pattern of (TiOXRD pattern of (TiO22-Hg) Complex-Hg) Complex


ConclusionConclusionConclusionConclusion

The removal efficiency was close to 100% under most light sources tested.

More than 99% of initial Hg was removed under all the light sources tested except for the blue light still achieving a Hg removal efficiency close to 80%.

High efficiency was achieved even under the low concentration.

Easily maintainable and cost-effective fluorescent light can be used.

Hg removal by sunlight

Future WorksFuture WorksFuture WorksFuture Works

• Verification of Hg removal efficiency with crystallinity, surface area, and particle size

• Verification of Hg

adsorption mechanism

under the visible light

• Hg removal by TiO2

directly coated on beads

• Application of TiO2

coated ferro-powder to

water treatment

• Furnace 온도가 증가함에 따라 크기가 커지지만 open structure 를 가진 입자를 생성

• 입자의 크기가 증가할수록 수은의 제거효율 증가

• NH3 를 이용하여 TiOx-Ny 를 제조 , 가시광선에의

반응성 측정 및 촉매 특성 분석

Structural Effect of In Situ Generated TiO2 on Hg0 Removal in a Simulated Combustion Flue Gas

Hood

On- lineHg Analyzer

HgQuartzReactor

Air

Nitrogen

TiPrecursor

SecondaryFurnace

Filter

UV Lamp

TemperatureController DMA

CPC

Argon

PrimaryFurnace

OilBath


Ti Precursor (g) TiO2 (g) TiO2 (s) Hg0 (g) UVHgO (g)

Ti(OCTi(OC33HH77))44 + 18O + 18O22 → TiO → TiO22+12CO+12CO2 2 +14H+14H22OO


1.88 1.81 1.70Df 1.761.93

175 188 201 225 247

55.18 74.86 90.98 108.73 129.01

dg (nm)

Rg(nm)

14.2 25.3 62.5Hg captureefficiency(%)

41.43.3


raman cm-1

100 200 300 400 500 600 700

cts

4000

6000

8000

10000

12000

14000

pure TTIPHAB; 5cm

Preparation of Column Shape TiO2 Fiber by a Diffusion Flame Reactor

• Height above burner (HAB) 에 따른 particle shape / crystallinity ; fibrous / anatase

• Raman Spectroscopy

Apparatus

Figure 1. Schemetic diagram of multiport diffusion with particle collection system

Controllerto Move mat

TTIPPrecursor

&Heatingmantle

DiffusionBurner

Slide Glass

MFC

MFC

MFC

MFC

N2

O2

LPG

Air

SEM I

<Figure 1. Pure TTIP, HAB=3cm> <Figure 2. Pure TTIP, HAB=5cm>

<Figure 4. Pure TTIP, HAB=10cm> <Figure 3. Pure TTIP, HAB=7.5cm>

SEM II

The End

연세대학교 화학공학과 이 태 규 제 4 회 광촉매 연구회 2004 년 2 월 26 일...

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