Clean Technology (청정기술)

The Korean Society of Clean Technology (한국청정기술학회)
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Study on the Co-firing of Sewage Sludge to a 80 kWth-scale Pulverized Coal Combustion System

80 kWth급 미분탄 연소 시스템에서 하수슬러지 혼소시 연소 특성 연구

  • Chae, Taeyoung (Thermochemical Energy System Group, Korea Institute of Industrial Technology) ;
  • Lee, Jaewook (Thermochemical Energy System Group, Korea Institute of Industrial Technology) ;
  • Lee, Youngjae (Thermochemical Energy System Group, Korea Institute of Industrial Technology) ;
  • Yang, Won (Thermochemical Energy System Group, Korea Institute of Industrial Technology)
  • 채태영 (한국생산기술연구원 고온에너지시스템그룹) ;
  • 이재욱 (한국생산기술연구원 고온에너지시스템그룹) ;
  • 이영재 (한국생산기술연구원 고온에너지시스템그룹) ;
  • 양원 (한국생산기술연구원 고온에너지시스템그룹)
  • Received : 2018.07.10
  • Accepted : 2018.11.27
  • Published : 2019.03.30
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Abstract

Thermochemical treatment of sewage sludge is an energy-intensive process due to its high moisture content. To save the energy consumed during the process, the hydrothermal carbonization process for sewage sludge can be used to convert sewage sludge into clean solid fuel without pre-drying. This study is aimed to investigate co-firing characteristics of the hydrothermally carbonated sewage sludge (HCS) to a pulverized coal combustion system. The purpose of the measurement is to measure the pollutants produced during co-firing and combustion efficiency. The combustion system used in this study is a furnace with a down-firing swirl burner of a $80kW_{th}$ thermal input. Two sub-bituminous coals were used as a main fuel, and co-firing ratio of the sewage sludge was varied from 0% to 10% in a thermal basis. Experimental results show that $NO_x$ is 400 ~ 600 ppm, $SO_x$ is 600 ~ 700 ppm, and CO is less than 100 ppm. Experimental results show that stable combustion was achieved for high co-firing ratio of the HCS. Emission of $NO_x$ and $SO_x$ was decreased for higher co-firing ratio in spite of the higher nitrogen contents in the HCS. In addition, it was found that the pollutant emission is affected significantly by composition of the main fuel, regardless of the co-firing ratios.

하수슬러지의 열화학적 처리는 수분을 제거하여 연료로 사용되는 하수슬러지의 수분 함량을 낮추어 주는 기술이다. 열화학적 처리된 하수슬러지는 열량이 높아지기 때문에 에너지 집약적 과정이라고 할 수 있다. 이러한 공정 중에 소비되는 에너지를 절약하기 위해 하수슬러지의 수열 탄화 공정을 사용하였다. 수열탄화 공정은 하수슬러지를 사전 건조 없이 깨끗한 고체연료로 전환할 수 있다. 본 연구는 수열탄화 하수슬러지와 미분탄 연소 시스템의 혼소 특성을 조사하는 것을 목적으로 한다. 혼소 시 생성되는 유해물질 및 연소 효율의 변화를 측정하는 것을 목적으로 한다. 본 연구에 사용 된 연소 시스템은 $80kW_{th}$급 연소로로서 1기의 선회류 버너가 장착되어 있다. 두 가지의 석탄을 주 연료로 사용하였고, 하수슬러지의 혼소율은 열량 기준 0% ~ 10%까지 진행하였다. 실험 결과 $NO_x$는 400 ~ 600 ppm, $SO_x$는 600 ~ 700 ppm 사이를 유지하였고, CO는 100 ppm 전후로 일정하게 유지되어 안정적인 연소를 확인할 수 있었다. 하수슬러지를 혼소할 경우, 혼소율이 증가할수록 $NO_x$와 $SO_x$의 배출량도 증가하였으나 그 편차가 크지 않았다. 연소 배가스에 포함된 오염 물질 배출은 혼소 비율 보다 주 연료인 석탄의 조성에 의해 크게 영향을 받는 것으로 밝혀졌다.

Keywords

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Figure 1. Schematic diagram of the 80 kWth down firing furnace system set-up.

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Figure 2. Thermogravimetric analysis (TGA) and derivative thermo-gravimetric (DTG) of coals and sewage sludges.

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Figure 3. Temperature of IN/HCS co-firing case.

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Figure 4. CO concentration (ppm).

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Figure 5. NOx concentration at O2 6%.

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Figure 6. SOx concentration at O2 6%.

Table 3. Experimental conditions for co-firing

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Table 1. Composition of fuels

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Table 2. Experimental condition for hydrothermal carbonization sewage sludge

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Table 4. Combustion efficiency by co-firing rate

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Table 5. Concentration of O2 and CO

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