SO2 Abatement in Cement Preheaters

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SO2 Abatement in Cement Preheaters

• Martin Hagsted Rasmussen, PhD student
• Kim Dam-Johansen, Professor
• Stig Wedel, Associated professor
• Jytte Boll Illerup, Senior Advisor
• Kent Thomsen, FLSmidth
• The project is a
• collaboration between
• DTU,
• FLSmidth and
• Danish National Advanced Technology Foundation

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The Dry Cement Plant
Introduction - Experimental - Results -
Conclusion

• A dry plant consist of
• 4-6 cyclones
• A calciner
• A rotary kiln
• A grate cooler
• Raw meal feed
• 75 CaCO3
• 25 Si,Al,Fe oxides
• Exhaust gas
• 65 N2
• 30 CO2
• 5 O2
• At ppm level
• VOC, NOx, CO and SO2

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Processes in the Preheater
Introduction - Experimental - Results -
Conclusion

• Pyrite Oxidation
• 2FeS2(s) 5½O2(g) ? Fe2O3(s) 4SO2(g)
• Direct Sulfation
• CaCO3(s) SO2(g) ? CaSO3(s) CO2(g)
• Indirect Sulfation
• CaO(s) SO2(g) ? CaSO3(s)
• Carbonization
• CaO(s) CO2(g) ? CaCO3(s)
• Calcination
• CaCO3(s) ? CaO(s) CO2(g)

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Experimental Setup
Introduction - Experimental - Results -
Conclusion

• Setup features
• Very short residence time
• Designed for particle/gas reaction
• Isothermal
• Possible to inject two different gases
• 4 gas injection spots
• Accurate particle feeder
• Atmospheric pressure

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Reaction Product
Introduction - Experimental - Results -
Conclusion

• Results
• No difference at low temperatures, indicates
  CaSO3
• Oxidation of CaSO3 starts between 590ºC and 640ºC
• Particle Data
• Particle size 75-150 micron
• Surface area 54 m2/g (BET)
• Porosity 31

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Influence of CO2
Introduction - Experimental - Results -
Conclusion

• Results
• CO2 change the influence of temperature
• CO2 effect largest at high
• temperature
• Conversion is 10 times
• higher than pure
• limestone at 600 ºC
• Particle Data
• Particle size 150-250 micron
• Calcination degree 88
• Surface area 20 m2/g (BET)
• Porosity 41

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Conclusions
Introduction - Experimental - Results -
Conclusion

• Below 590 ºC oxygen do not affect the reaction
• CO2 strongly decrease the
• conversion, especially at high temperatures
• CaO/SO2 is more reactive than
• CaCO3/SO2 even when CO2 is present

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Tak for opmærksomheden/ Thanks for the Attention !