Biomass Conversion and Biorefinery

, Volume 8, Issue 2, pp 357–367 | Cite as

A novel dual-bed for steam gasification of biomass

  • Y. H. Li
  • Z. Chen
  • P. Watkinson
  • X. Bi
  • J. Grace
  • C. J. Lim
  • N. Ellis
Original Article

Abstract

A unique indirect steam gasification system for biomass has been developed and tested. The unit features a bubbling bed gasifier equipped with a “sore thumb” and central standpipe, which circulate a mixture of bed material and char through a U-bend to a riser in which char combustion occurs. Re-circulated silica sand from the riser is returned to the bubbling bed through a trickle valve at sufficiently high temperatures to drive biomass gasification. Factors which govern re-circulation of solids are explored and pressure profiles demonstrated. Gasification tests using wood pellets fed at 10–15 kg/h showed that syngas with heating value of about 12 MJ/m3 and nitrogen contents < 5% can be produced. Trends of gas composition versus bed temperature are established. The char combustor required a continuous flow of auxiliary fuel (natural gas) to compensate for high heat losses in the system. Circulation rates were such that riser top temperatures roughly 100 °C above those of the bubbling bed were adequate to provide the gasification heat, without auxiliary fuel to the gasification stage.

Keywords

Dual-bed Biomass gasification Indirect gasifier 

Nomenclature and abbreviations

B

Biomass mass rate (kg dry basis/h)

BFB

Bubbling fluidized bed

BM

Biomass

CFB

Circulating fluidized bed

H0

BFB static bed height above distributor (m)

HW

Hardwood

L

Reactor length (m)

LHV

Lower heating value (MJ/Nm3)

P

Pressure (kPa)

PCFB

Pressure in circulating fluidized bed (kPa)

PBFB

Pressure in bubbling fluidized bed (kPa)

S

Steam input (kg/h)

S/B

Steam to biomass mass feed ratio

SW

Softwood

TBFB

Average temperature in bubbling fluid bed gasifier (°C)

TCFB

Top temperature in combustor riser (°C)

UBFB

Superficial gas velocity in BFB (m/s)

Notes

Acknowledgements

The authors wish to gratefully acknowledge Mike Stewart who worked on the original design and assembly of the unit, and the researchers, visiting scholars, and undergraduate and graduate students who have contributed to operating the pilot plant in teams over the past few years: Tim Cai, Bill Cheng, Luis Daniel, David Houghton, Wolfgang Huster, Lea Pierrot, Ujash Shah, Marion Wilhelm, Katharina Lammel, Chao Qu, YongShi Liang, RuiXu Wang, Ziliang Wang, Hafiz Rahman, Dr. XiaoBo Chen, Dr. Jhon Ramirez, and Dr. Lai Wang. For in-kind support and advice, we are grateful to Noram Engineering and Constructors Ltd. We also acknowledge the help of Marlene Chow, and the contribution of our department workshop.

Funding information

Financial support has been provided by Highbury Energy Inc., Natural Sciences and Engineering Research Council of Canada (NSERC) Strategic Partnership Grant, BC Bioenergy Network, CMC Research Institutes (formerly Carbon Management Canada), Dow Chemical Co., and Fraunhofer Institute.

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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Y. H. Li
    • 1
  • Z. Chen
    • 2
  • P. Watkinson
    • 1
  • X. Bi
    • 2
  • J. Grace
    • 2
  • C. J. Lim
    • 2
  • N. Ellis
    • 2
  1. 1.Highbury Energy Inc.VancouverCanada
  2. 2.Department of Chemical and Biological EngineeringThe University of British ColumbiaVancouverCanada

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