We’re sorry, something doesn't seem to be working properly.

Please try refreshing the page. If that doesn't work, please contact support so we can address the problem.


The enhanced SO3 formation by alkali-metal sulfates from ash in the post-flame region during the combustion of high-alkali coal

  • 59 Accesses


High alkali-metal sulfate contents in ash from high-alkali coal are a result of the alkali metals’ strong sulfur-capturing capacity. In this work, the effects of sulfates in ash on SO3 formation were investigated by adding alkali-metal sulfates (Na2SO4 and K2SO4) to ash and performing experiments to simulate SO3 formation. The results show that Na2SO4 and K2SO4 addition significantly increased SO3 formation and the formation rate increased with increasing temperature. The formed SO3 concentration increased by 6.8 ppm (adding Na2SO4) and 6.3 ppm (adding K2SO4) at 1000 °C. These increases are the result of SO3 release from sulfate during the formation of aluminosilicates such as NaAlSi3O8 (albite), NaAlSiO4 (nepheline), KAlSiO4 (kalsilite), and KAlSi3O8 (feldspar) with the SiO2 and Al2O3 in the ash. This was confirmed by X-ray diffraction (XRD) and thermodynamic calculation. In addition, increasing the SO2 concentration increased the SO3 concentration and decreased the SO3 conversion ratio.

Note: This data is mandatory.

This is a preview of subscription content, log in to check access.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8


  1. Ahn J, Okerlund R, Fry A et al (2011) Sulfur trioxide formation during oxy-coal combustion. Int J Greenh Gas Control 5:127–135

  2. Belo LP, Elliott LK, Stanger RJ et al (2014) High-temperature conversion of SO2 to SO3: homogeneous experiments and catalytic effect of fly ash from air and oxy-fuel firing. Energ Fuel 28:7243–7251

  3. Benson SA, Laumb JD, Crocker CR et al (2005) SCR catalyst performance in flue gases derived from subbituminous and lignite coals. Fuel Process Technol 86:577–613

  4. Cao Y, Zhou H, Jiang W, Chen CW, Pan WP (2010) Studies of the fate of sulfur trioxide in coal-fired utility boilers based on modified selected condensation methods. Environ Sci Technol 44:3429–3434

  5. Chen XD, Kong LX, Bai J et al (2017) Study on fusibility of coal ash rich in sodium and sulfur by synthetic ash. Fuel 202:175–183

  6. Dai BQ, Wu XJ, Zhang ZX (2014) Transition behavior of main elements in fly ash during high alkali coal combustion. Journal of Chinese Society of Power Engineering 34:438–442 (in Chinese)

  7. Duan L, Duan Y, Sarbassov Y et al (2015) SO3 formation under oxy-CFB combustion conditions. Int J Greenh Gas Con 43:172–178

  8. Dunn JP, Stenger JHJ, Wachs IE (1999) Molecular structure–reactivity relationships for the oxidation of sulfur dioxide over supported metal oxide catalysts. Catal Today 53:543–556

  9. Fleig D, Alzueta MU, Normann F et al (2013) Measurement and modeling of sulfur trioxide formation in a flow reactor under post-flame conditions. Combust Flame 160:1142–1151

  10. Glarborg P, Marshall P (2005) Mechanism and modeling of the formation of gaseous alkali sulfates. Combust Flame 141:22–39

  11. Guo JZ, Liu XW, Wang H et al (2018) Effect of HCl and CO on sulfur trioxide formation mechanisms during oxyfuel combustion. Fuel Process Technol 174:95–103

  12. Gupta SK, Gupta RP, Bryant GW et al (1998) The effect of potassium on the fusibility of coal ashes with high silica and alumina levels. Fuel 77:1195–1201

  13. Hindiyarti L, Glarborg P (2007) Reactions of SO3 with the O/H radical pool under combustion conditions. J Phys Chem A 111:3984–3991

  14. Kim KH, Choi JH (1981) Kinetics and mechanism of the oxidation of sulfur dioxide on α-Fe2O3. J Phys Chem 85:2447–2450

  15. Monckert P, Dhungel B, Kull R et al (2008) Impact of combustion conditions on emission formation (SO2, NOx) and fly ash. In: 3rd MEETING of the OXY-FUEL COMBUSTION NETWORK. Yokohama Symposia, Yokohama, Japan: IEA Greenhouse Gas R&D Programme

  16. Ochs TL, Oryshchyn DB, Gross D et al (2004) Oxy-fuel combustion systems for pollution free coal fired power generation, https://www.researchgate.net/publication/228418450_Oxy-fuel_combustion_systems_for_pollution_free_coal_fired_power_generation

  17. Pan PY, Chen H, Liang ZY et al (2018) Desulfurized flue gas corrosion coupled with deposits in a heating boile. Corros Sci 131:126–136

  18. Shi Y, Zhang P, Fang TT et al (2018) In situ regeneration of commercial NH3-SCR catalysts with high-temperature water vapor. Catal Commun 116:57–61

  19. Srivastava RK, Miller CA, Erickson C et al (2004) Emissions of sulfur trioxide from coal-fired power plants. J Air Waste Manage 54:750–762

  20. Steenari BM, Lindqvist O (1998) High-temperature reactions of straw ash and the anti-sintering additives kaolin and dolomite. Biomass Bioenergy 14:67–76

  21. Walsh PM, McCain JD, Cushing KM (2006) Evaluation and mitigation of visible acidic aerosol plumes from coal fired power boilers. US Environmental Protection Agency, Washington, DC, EPA/600/R-06/156, 2006

  22. Wang XP, Liu XW, Li D et al (2015a) Effect of steam and sulfur dioxide on sulfur trioxide formation during oxy-fuel combustion. Int J Greenh Gas Con 43:1–9

  23. Wang LY, Mao HX, Wang ZS et al (2015b) Transformation of alkali and alkaline-earth metals during coal oxy-fuel combustion in the presence of SO2 and H2O. J Nat Gas Chem 24:381–387

  24. Wang ZQ, Hu YJ, Cheng XX et al (2018) Study of adsorption characteristics of calcium-based sorbents with SO3. Energy Procedia 144:43

  25. Wei B, Tan HZ, Wang XB et al (2018) Investigation on ash deposition characteristics during Zhundong coal combustion. J Energy Inst 91:33–42

  26. Xiang BX, Shen WF, Zhang M et al (2017) Effects of different factors on sulfur trioxide formations in a coal-fired circulating fluidized bed boiler. Chem Eng Sci 172:262–277

  27. Xiao HP, Qi C, Cheng QY et al (2018) Experimental and modeling studies of SO3 homogeneous formation in the post-flame region. Aerosol Air Qual Res 18(12): 2939–2947

  28. Zhang LJ, Li ZH, Yang YL et al (2016) Effect of acid treatment on the characteristics and structures of high-sulfur bituminous coal. Fuel 186:418–429

  29. Zhao QX, Zhang ZX, Cheng DN et al (2012) High temperature corrosion of water wall materials T23 and T24 in simulated furnace atmospheres. Chinese J Chem Eng 20:814–822

  30. Zhao HB, He YZ, Shen JD (2018) Effects of temperature on electrostatic precipitators of fine particles and SO3. Aerosol Air Qual Res 18(11): 2906–2911

  31. Zheng CH, Wang YF, Liu Y (2019) Formation, transformation, measurement, and control of SO3 in coal-fired power plants. Fuel 241:327–346

Download references

Author information

Correspondence to Qiyong Cheng.

Ethics declarations

The authors declare that they have no competing interests.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


Effects of different factors on SO3 heterogeneous formation were investigated.

Na2SO4 and K2SO4 can promote SO3 formation by ash.

Sulfates formed aluminosilicates with SiO2 and Al2O3 in ash and SO3 was released.

Responsible editor: Philippe Garrigues

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Xiao, H., Cheng, Q., Shi, H. et al. The enhanced SO3 formation by alkali-metal sulfates from ash in the post-flame region during the combustion of high-alkali coal. Environ Sci Pollut Res (2020). https://doi.org/10.1007/s11356-020-07604-y

Download citation


  • Alkali-metal sulfates
  • Sulfur trioxide
  • High-alkali coal
  • Fly ash
  • Aluminosilicate