Clean Technology (청정기술)

The Korean Society of Clean Technology (한국청정기술학회)
권호 표지
DOI QR코드

DOI QR Code

High Temperature Corrosion Effect of Superheater Materials by Alkali Chlorides

염화알칼리에 의한 과열기 소재의 고온부식 영향

  • Kim, Beomjong (School of mechanical Engineering, Sungkyunkwan University) ;
  • Jeong, Soohwa (Thermochemical Energy System R&BD Group, Korea Institute of Industrial Technology) ;
  • Kim, Hyesoo (Thermochemical Energy System R&BD Group, Korea Institute of Industrial Technology) ;
  • Ryu, Changkook (School of mechanical Engineering, Sungkyunkwan University) ;
  • Lee, Uendo (Thermochemical Energy System R&BD Group, Korea Institute of Industrial Technology)
  • 김범종 (성균관대학교 기계공학과) ;
  • 정수화 (한국생산기술연구원 고온에너지시스템그룹) ;
  • 김혜수 (한국생산기술연구원 고온에너지시스템그룹) ;
  • 류창국 (성균관대학교 기계공학과) ;
  • 이은도 (한국생산기술연구원 고온에너지시스템그룹)
  • Received : 2018.07.31
  • Accepted : 2018.08.22
  • Published : 2018.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

In order to cope with environmental problems and climate change caused by fossil fuels, renewable energy supply is increasing year by year. Currently, waste energy accounts for 60% of renewable energy production. However, waste has a lower calorific value than fossil fuels and contains various harmful substances, which causes serious problems when applied to power generation boilers. In particular, the chlorine in the waste fuel increases slagging and fouling of boiler heat exchangers, leading to a reduction in thermal efficiency and the main cause of high temperature corrosion, lowering facility operation rate and increasing operating cost. In this study, the high temperature corrosion experiments of superheater materials (ASME SA213/ASTM A213 T2, T12 and T22 alloy steel) by alkali chlorides were conducted, and their corrosion characteristics were analyzed by the weight loss method and SEM-EDS. Experiments show that the higher the temperature and chloride content, the more corrosion occurs, and KCl further corrodes the materials compared to NaCl under the same condition. In addition, the higher the chromium content of the material, the better the corrosion resistance to the alkali chlorides.

화석연료로 인한 환경문제 및 기후변화 대응을 위해 신재생에너지 공급비중은 매년 증가하고 있으며 현재 폐기물 에너지는 신재생에너지 생산량의 60% 가량을 차지하고 있다. 그러나 폐기물은 화석연료에 비해 낮은 발열량을 가지고 여러 유해물질이 포함되어 있어 발전용 보일러에 적용 시 다양한 문제를 발생시킨다. 특히 연료 내 염소성분은 보일러 열교환부에 슬래깅 및 파울링을 증가시켜 열효율 감소와 고온부식의 주요 원인이 되며 설비 가동률을 낮추고 운전비용을 증가시킨다. 본 연구에서는 염화알칼리에 의한 과열기 소재의 부식특성 분석을 위해 과열기용 주요 금속소재(ASME SA213/ASTM A213 T2, T12 and T22 합금)를 대상으로 고온부식 실험을 수행하고 무게 감량법과 주사전자현미경 에너지분산분광기(SEM-EDS)를 활용해 다양한 조건에 따른 부식특성을 분석하였다. 실험 결과 온도 및 염화물 함량이 높을수록 부식이 증가하였으며 NaCl보다 KCl의 부식성이 더 높음을 확인하였다. 또한 소재의 크롬함량이 높을수록 염화알카리에 대한 내부식 특성이 우수하게 나타났다.

Keywords

CJGSB2_2018_v24n4_339_f0001.png 이미지

Figure 1. Mechanism of high temperature corrosion by alkali chlorides(chlorine-cycle)[14].

CJGSB2_2018_v24n4_339_f0002.png 이미지

Figure 2. Photo of metal coupons.

CJGSB2_2018_v24n4_339_f0003.png 이미지

Figure 3. Procedure of high temperature corrosion experiment.

CJGSB2_2018_v24n4_339_f0004.png 이미지

Figure 4. Variation of weight loss using cleaning method according to ASTM G1-03.

CJGSB2_2018_v24n4_339_f0005.png 이미지

Figure 5. Rate of weight loss with respect to the alkali chlorides and coupons at 400 ℃.

CJGSB2_2018_v24n4_339_f0006.png 이미지

Figure 6. Rate of weight loss with respect to the alkali chlorides and coupons at 500 ℃.

CJGSB2_2018_v24n4_339_f0007.png 이미지

Figure 7. Surface morphology of the T2 coupons: (a) Reference, 400 ℃ (b) KCl, 400 ℃ (c) NaCl, 400 ℃ (d) Reference, 500 ℃ (e) KCl, 500 ℃ (f) NaCl, 500 ℃.

CJGSB2_2018_v24n4_339_f0008.png 이미지

Figure 8. Surface morphology of the T12 coupons: (a) Reference, 400 ℃ (b) KCl, 400 ℃ (c) NaCl, 400 ℃ (d) Reference, 500 ℃ (e) KCl, 500 ℃ (f) NaCl, 500 ℃.

CJGSB2_2018_v24n4_339_f0009.png 이미지

Figure 9. Surface morphology of the T22 coupons: (a) Reference, 400 ℃ (b) KCl, 400 ℃ (c) NaCl, 400 ℃ (d) Reference, 500 ℃ (e) KCl, 500 ℃ (f) NaCl, 500 ℃.

Table 1. Previous studies on anti-corrosion technology as material aspects

CJGSB2_2018_v24n4_339_t0001.png 이미지

Table 2. Characteristic of boiler tubes materials and their applications

CJGSB2_2018_v24n4_339_t0002.png 이미지

Table 3. Chemical composition of coupons

CJGSB2_2018_v24n4_339_t0003.png 이미지

Table 4. SEM photo with respect to temperature and kinds of alkali chlorides

CJGSB2_2018_v24n4_339_t0004.png 이미지

References

  1. Moon, J. H., Lee, J. W., and Lee, U. D., "Economic Analysis of Biomass Power Generation Schemes Under Renewable Energy Initiative with Renewable Portfolio Standards (RPS) in Korea," Bioresour. Technol., 102, 9550-9557 (2011). https://doi.org/10.1016/j.biortech.2011.07.041
  2. Leckner, B., "Process Aspects in Combustion and Gasification Waste-to-energy (WtE) Units," Waste Manage., 37, 13-25 (2015). https://doi.org/10.1016/j.wasman.2014.04.019
  3. Viklund, P., "Superheater Corrosion in Biomass and Waste Fired Boilers," Ph.D Dissertation, KTH, Stockholm (2013).
  4. Patumsawad, S., and Cliffe, K. R., "Experimental Study on Fluidised Bed Combustion of High Moisture Municipal Solid Waste," Energy Conversion and Manage., 43, 2329-2340 (2002). https://doi.org/10.1016/S0196-8904(01)00179-0
  5. Shaop, S., "Could Biomass Boilers be Operated at Higher Steam Efficiencies (Higher temps.)?," International Workshop on High Temperature Corrosion in Biomass Installation (2014).
  6. Persson, K., Brostrom, M., Carlsson, J., Nordin, A., and Baclman, R., "High Temperature Corrosion in a 65MW Waste to Energy Plant," Fuel Process. Technol., 88, 1178-1182 (2007). https://doi.org/10.1016/j.fuproc.2007.06.031
  7. Karlsson, S., Pettersson, J., and Johansson, L.-G., "Alkali Induced High Temperature Corrosion of Stainless Steel: The Influence of NaCl, KCl and $CaCl_2$," Oxidat. Metals, 78(1-2), 83-102 (2012). https://doi.org/10.1007/s11085-012-9293-7
  8. Enestam, S., Bankiewicz, D., Tuiremo, J., Makela, K., and Hupa, M., "Are NaCl and KCl Equally Corrosive on Superheater Materials of Steam Boilers?," Fuel, 104, 294-306 (2013). https://doi.org/10.1016/j.fuel.2012.07.020
  9. Viklund, P., Hjornhede, A., Henderson, P., Stalenheim, A., and Pettersson, R., "Corrosion of Superheater Materials in a Waste-to-energy Plant," Fuel Process. Technol., 105, 106-112 (2013). https://doi.org/10.1016/j.fuproc.2011.06.017
  10. Wand, S. L., Li, H. X., Zhang, X. F., and Yi, S., "Effects of Cr Contents in Fe-based Bulk Metallic Glasses on the Glass Forming Ability and the Corrosion Resistance," Mater. Chem. Physics, 113, 878-883 (2009). https://doi.org/10.1016/j.matchemphys.2008.08.057
  11. Xu, T., Pang, S., Li, H., and Zhanf, T., "Corrosion Resistant Cr-based Bulk Metallic Glasses with High Strength and Hardness," J. Non-Crystalline Solids, 410, 20-25 (2015). https://doi.org/10.1016/j.jnoncrysol.2014.12.006
  12. Alexander, P. A., In Johnson, R., and Littler, D. J., Eds., The Mechanism of Corrosion by Impurities, Londen, Butterwoths, 571 (1963).
  13. Lehmusto, J., Skrifvars, B.-J., Yrjas, P., and Hupa, M., "High Temperature Oxidation of Metallic Chromium Exposed to Eight Different Metal Chlorides," Corrosion Sci., 53(10), 3315-3323 (2011). https://doi.org/10.1016/j.corsci.2011.06.007
  14. Kim, B. J., Ryu, C. K., Lee, U. D., Kim Y. D., Lee, J. W., and Song, J. H., "A Technical Review on the Protective Measures of High Temperature Corrosion of Boiler Eat Exchangers with Additives," Clean Technol., 23(3), 223-236 (2017). https://doi.org/10.7464/ksct.2017.23.3.223
  15. Lee, D.-B., "High-Temperature Corrosion by Chlorides in Biomass-Fired Plants," J. Korean Inst. Surface Eng., 49(1), 14-19 (2016). https://doi.org/10.5695/JKISE.2016.49.1.14
  16. Steenari, B. M., Lundberg, A., Pettersson, H., Wilewska-Bien, M., and Andersson, D., "Investigation of Ash Sintering during Combustion of Agricultural Residues and the Effect of Additives," Energy Fuels, 23(11), 5655-5662 (2009). https://doi.org/10.1021/ef900471u
  17. Steenari, B. M., and Lindqvist, O., "High-temperature Reactions of Straw Ash and The Anti-Sintering Additives Kaolin and Dolomite," Biomass and Bioenergy, 14(1), 67-76 (1998). https://doi.org/10.1016/S0961-9534(97)00035-4
  18. Gilbe, C., Ohman, M., Lindstrom, E., Bostrom, D., Backman, R., Samuelsson, R., and Burvall, J., "Slagging Characteristics during Residential Combustion of Biomass Pellets," Energy and Fuels, 22(5), 3536-3543 (2008). https://doi.org/10.1021/ef800087x
  19. Lindstrom, E., Sandstrom, M., Bostrom, D., and Ohman, M., "Slagging Characteristics during Combustion of Cereal Grains Rich in Phosphorus," Energy & Fuels, 21(2), 710-717 (2007). https://doi.org/10.1021/ef060429x
  20. Wang, L., Skjevrak, G., Hustad, J., E., and Gronli, M. G., "Sintering Characteristics of Sewage Sludge Ashes at Elevated Temperatures," Fuel Processing Technol., 96, 88-97 (2012). https://doi.org/10.1016/j.fuproc.2011.12.022
  21. Elled, A. L., Davidsson, K. O., and Amand, L. E., "Sewage Sludge as a Deposit Inhibitor when Co-Fired with High Potassium Fuels," Biomass and Bioenergy, 34, 1546-1554 (2010). https://doi.org/10.1016/j.biombioe.2010.05.003
  22. Adams, E. M., Peters, K. E., Diederen, S. W., and Winjhoven, P. F., "Preventing boiler corrosion," Waste Management World (2004).