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연세대학교 화학공학과 이 태 규 PowerPoint PPT Presentation


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Comparison of Mercury Removal Efficiency from a Simulated Exhaust Gas by Several Types of TiO 2 under Various Light Sources. 연세대학교 화학공학과 이 태 규. 제 4 회 광촉매 연구회 2004 년 2 월 26 일. Introduction. Mercury. Toxic properties High volatility Tendency to bio-accumulate. Emission resources.

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Comparison of Mercury Removal Efficiency from a Simulated Exhaust Gas by Several Types of TiO2 under Various Light Sources

연세대학교 화학공학과

이 태 규

제4회 광촉매 연구회

2004년 2월 26일


Introduction

Mercury

  • Toxic properties

  • High volatility

  • Tendency to bio-accumulate

Emission resources

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


Introduction

Hg 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)


Photocatalyst TiO2

 high removal efficiency for low concentrations of toxic compounds

Hg removal under UV light

Introduction

Hg removal by adsorbents

Activated Carbon

=> most widely used

disadvantage

  • Low applicable

    temperature range

  • Low regeneration rate &

    slow adsorption rate


Introduction

UV light

  • high energy strength

  • harmful

  • development of improved photocatalysts activating

  • under the visible light!!!

Intermediate

step

Hg removal using a TiO2

under thefluorescent light


Theory

Hg capture by TiO2

Light

Hg

TiO2

HgO

O

2

-

O

2

-

e

H

O

2

OH

+

Hg

HgO

+

+

H

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


Experimental

Apparatus


Light Sources

TiO2 Powder

  • UV black light

  • UV sterilizing light

  • fluorescent light

  • blue light

  • pure anatase (Ishihara co.)

  • P25 (Degussa co.)

  • anatase : rutile = 80 : 20

  • pure rutile (Junsei co.)

Experimental


UV-C

UV-B

UV-A

Visible Light

Infrared Ray

Experimental

Wave length


Results

[a] UV black light


Results

[b] UV sterilizing light


Results

[c] fluorescent light


Results

[d] blue light


Results

Breakthrough Experiment


Results

XRD pattern of (TiO2-Hg) Complex


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.

Conclusion


Future Works

  • Verification of Hg adsorption mechanism under the visible light

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

  • Hg removal by TiO2 directly coated on beads

  • Application of TiO2 coated ferro-powder to water treatment

Hg removal by sunlight


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

• Furnace 온도가 증가함에 따라 크기가 커지지만

open structure를 가진 입자를 생성

•입자의 크기가 증가할수록 수은의 제거효율 증가

• NH3를 이용하여 TiOx-Ny를 제조, 가시광선에의

반응성 측정 및 촉매 특성 분석


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


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

Ti(OC3H7)4 + 18O2 → TiO2+12CO2 +14H2O


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


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


SEM I

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

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


SEM II

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

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


The End


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