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Licensed Unlicensed Requires Authentication Published by De Gruyter August 22, 2017

Bed Material Agglomeration Behavior in a Bubbling Fluidized Bed (BFB) at High Temperatures using KCl and K2SO4 as Simulated Molten Ash

  • Ehsan Ghiasi , Alejandro Montes , Fatemeh Ferdosian , Honghi Tran and Chunbao (Charles) Xu EMAIL logo

Abstract

The agglomeration of bed material is one of the most serious problems in combustion of biomass in fluidized-bed boilers, due to the presence of some inorganic alkali elements such as K and Na in the biomass ash, which form low-melting-point alkali compounds during the process. In this study, agglomeration behaviors of bed materials (silica sand particles) were investigated in a bench-scale bubbling fluidized-bed reactor operating at 800 °C using simulated biomass ash components: KCl, K2SO4, and a mixture of KCl and K2SO4 at eutectic composition (molar ratio K2SO4/(KCl+ K2SO4)=0.26). The signals of temperature and differential pressure across the bed were monitored while heating up the fluidized bed of silica sand particles premixed with various amounts of KCl, and the KCl-K2SO4 mixture in bubbling bed regime. A sharp decrease in temperature and differential pressure was observed around 750 °C and 690 °C for 0.4–0.6 wt% loading of the low melting-point KCl and KCl-K2SO4 mixture, respectively, suggesting the formation of bed material agglomeration and even de-fluidization of the bed. Moreover, this work demonstrated the effectiveness of kaolin and aluminum sulfate to minimize agglomeration. The results indicated that these additives could successfully prevent the formation of agglomerates by forming compounds with high melting points.

Funding statement: Natural Sciences and Engineering Research Council of Canada, (Grant/Award Number: ‘CRD’).

Acknowledgements

This investigation is a part of the NSERC CRD project titled “FUNDAMENTAL STUDIES OF DRYING, COMBUSTION AND ASH PROPERTIES OF BIOMASS, AND IMPACTS ON BOILER AND PULP AND PAPER MILL OPERATIONS”, led by one of the authors (H. Tran) at The University of Toronto. The authors (C. Xu and H. Tran) would also like to acknowledge the financial support provided by NSERC via the Discovery Grants, as well as the industrial support from various pulp and paper companies.

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Published Online: 2017-8-22

© 2017 Walter de Gruyter GmbH, Berlin/Boston

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