청정기술 (Clean Technology)

  • 제25권1호
  • /
  • Pages.63-73
  • /
  • 2019
  • /
  • 1598-9712(pISSN)
  • /
  • 2288-0690(eISSN)
한국청정기술학회 (The Korean Society of Clean Technology)
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SNCR 시스템 내부의 물질 반응에 관한 전산해석적 연구

CFD Analysis on the Internal Reaction in the SNCR System

  • Koo, Seongmo (Department of Environmental Engineering, Yeungnam University) ;
  • Yoo, Kyung-Seun (Department of Environmental Engineering, Kwangwoon University) ;
  • Chang, Hyuksang (Department of Environmental Engineering, Yeungnam University)
  • 투고 : 2018.11.08
  • 심사 : 2018.12.17
  • 발행 : 2019.03.30
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초록

연소공정 내에서 질소산화물 배출을 저감하는 선택적 무촉매 환원장치 내부의 화학반응 및 저감효율에 대한 수치해석이 실행되었다. 선택적 무촉매 환원장치에서 저감된 질소산화물은 질소뿐만 아니라 아산화질소로도 전환된다. 아산화질소는 온실가스로써 지구온난화에 영향을 끼치기 때문에 선택적 무촉매 환원장치 내의 질소산화물 제어와 동시에 아산화질소 생성제어가 요구되어진다. 본 연구에서는 선행연구에서 실행된 실험과 온도조건과 가성소다의 첨가량이 동일한 선택적 무촉매 환원장치 내의 전산해석을 실시하고 비교하여 전산해석의 신뢰성을 확인하고, 가성소다 첨가량을 추가적으로 조절하여 질소산화물의 저감 효율과 아산화질소 생성량을 예측하였다. 전산해석은 후단의 측정점을 설정하여 각 물질의 질량분율을 확인하였다. 세부적으로는 측정점에서 유동방향에 수직한 면을 설정하여 온도 조건과 가성소다 첨가량에 따른 각 물질의 평균 질량분율을 비교하였다. 실험값과 전산해석에 의한 모사값은 최대 18.9%의 오차를 보이며 대체적으로 잘 예측됨을 확인하였으며 가성소다 첨가량을 증가시켰을 땐 70% 이상의 제거율의 온도 범위가 넓어지는 것을 확인하였다. 따라서 반응온도의 낙차가 크고 잦은 폐기물 소각시설 등에서 효과적일 것으로 예상된다.

Numerical analysis was done to evaluate the chemical reaction and the reduction rate inside of selective non-catalytic reduction to denitrification in combustion process. The $NO_X$ reduction in selective non-catalytic reduction is converted to not only nitrogen but also nitrous oxide. Simultaneous $NO_X$ reduction and nitrous oxide generation suppressing is required in selective non-catalytic reduction because nitrous oxide influences the global warming as a greenhouse gas. The current study was performed compare the computational analysis in the same temperature and amount of NaOH, and in comparison with the previous research experiments and confirmed the reliability of the computational fluid dynamics. Additionally, controlling the addition amount of NaOH to predict the $NO_X$ reduction efficiency and nitrous oxide production. Numerical analysis was done to check the mass fraction of each material in the measurement point at the end of selective non-catalytic reduction. Experimental Value and simulation value by numerical analysis showed an error of up to 18.9% was confirmed that a generally well predicted. and it was confirmed that the widened temperature range of more than 70% $NO_X$ removal rate is increased when the addition amount of NaOH. So, large and frequent changes of the reaction temperature waste incineration facilities are expected to be effective.

키워드

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Figure 1. Schematic of the SNCR reactor.

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Figure 2. Location of nozzle tips.

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Figure 3. Mesh of the SNCR reactor.

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Figure 4. Velocity distribution near the nozzle.

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Figure 5. Temperature distribution near the nozzle.

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Figure 6. NO concentration distribution near the nozzle.

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Figure 7. Reduction of NOX with respect to temperature at urea only.

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Figure 8. Reduction of NOX with respect to temperature at urea and NaOH 1%.

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Figure 9. Reduction of NOX with respect to temperature and NaOH percentage.

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Figure 10. NH3 slip with respect to temperature at urea only.

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Figure 11. Generation of N2O with respect to temperature at urea only.

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Figure 12. Generation of N2O with respect to temperature at urea and NaOH 1%.

Table 1. Boundary condition at main inlet

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Table 2. Boundary condition of atomizing air at nozzle tip

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Table 3. Boundary condition of 40% urea solution at nozzle tip

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Table 4. Boundary condition of heat loss at each wall

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Table 5. Boundary condition of 40% urea solution and NaOH 1% at Nozzle tip

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Table 6. Reaction list

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Table 7. Comparison of NOX reduction percentage between experimental and CFD at two different NaOH concentration and five different heat loss

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