Clean Technology (청정기술)

The Korean Society of Clean Technology (한국청정기술학회)
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Co-firing Characteristics and Slagging Behavior of Sewage Sludge with Coal and Wood Pellet in a Bubbling Fluidized Bed

기포 유동층 반응기를 이용한 하수 슬러지와 석탄 및 우드 펠렛의 혼소 특성 및 슬래깅 성향 연구

  • Received : 2018.06.27
  • Accepted : 2018.08.02
  • Published : 2018.12.31
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Abstract

The results of an experimental investigation on the co-firing characteristics and slagging behavior of dried and hydrothermal carbonization sewage sludge, sub-bituminous coal, and wood pellet in a fluidized bed were presented. Combustion tests were conducted in a lab-scale bubbling fluidized bed system at the uniform fuel-air equivalence ratio, air flow rate, and initial bed temperature to measure bed temperature distribution and combustion gas composition. 4 different fuel blending cases were prepared by mixing sewage sludge fuels with coal and wood pellet with the ratio of 50 : 50 by the heating value. $NO_x$ was mostly NO than $NO_2$ and measured in the range of 400 to 600 ppm in all cases. $SO_2$ was considered to be affected mostly by the sulfur content of the sewage sludge fuels. The cases of hydrothermal carbonization sewage sludge mixture showed slightly less $SO_2$ emission but higher fuel-N conversion than the dried sewage sludge mixing cases. The result of fly ash composition analysis implied that the sewage sludge fuels would increase the possibility of slagging/fouling considering the contents of alkali species, such as Na, K, P. Between the two different sewage sludge fuels, dried sewage sludge fuel was expected to have the more severe impact on slagging/fouling behavior than hydrothermal carbonization sewage sludge fuel.

실험실 규모 기포 유동층 반응기를 이용한 하수 슬러지와 석탄 및 우드 펠렛의 혼소 실험 및 회분 분석을 통한 슬래깅 성향을 살펴보았다. 연료는 일반 건조 및 수열탄화를 통해 제작된 하수 슬러지와 아역청탄, 우드 펠렛이 적용되었다. 연소 실험은 당량비 및 산화제 유량, 초기 온도를 고정하고 2종의 하수 슬러지 연료와 석탄 또는 우드 펠렛을 발열량 기준 50 : 50 비율로 혼합한 총 4개의 조건에 대해 반응기 온도 및 배가스 조성을 측정하였다. 배가스 중 $NO_x$는 모든 조건에서 대부분 NO의 형태로 400 ~ 600 ppm 범위에서 측정되었다. $SO_2$는 원료 내 황 함량을 고려하면 하수 슬러지의 투입량이 큰 영향을 미쳤을 것으로 예상되는 가운데 수열탄화 연료가 일반 건조 연료에 비해 다소 낮은 경향을 보였다. 비산 회분 조성 분석 결과 하수 슬러지 연료가 슬래깅/파울링 가능성을 높일 것으로 생각되며, 수열탄화 연료가 일반 건조 연료에 비해 상대적으로 양호한 결과를 보일 것으로 예상되었다.

Keywords

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Figure 1. Schematic diagram of the lab-scale bubbling fluidized bed system.

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Figure 2. Measured temperature profiles of the tested conditions.

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Figure 3. Measured emission profiles of the tested conditions.

Table 1. Proximate, ultimate and heating value analysis results of Coal, WP, HTCSS and DSS

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Table 2. Ash fusion temperature analysis result at oxidizing condition

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Table 3. Evaluation of slagging tendency as ash fusibility index (AFI)

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Table 4. Results of ash composition analysis for the fuel samples (wt%)

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Table 5. Ash deposition tendency of fuel sample ashes

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Table 6. Experimental conditions

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Table 7. Mean temperature at measured points

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Table 8. Mean flue gas emissions at sampling point

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Table 9. Results of ash composition analysis for the tested cases (wt%)

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Table 10. Ash deposition tendency of the tested cases

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