GAS-L: Biomass Gasification and Feeding

["Tom Miles" <tmiles@trmiles.com>]

Subject:     Biomass Gasification and Feeding
> 
> 
> 
> 
> I've been following with interest the recent exchanges between Tom Reed,
> Tom Miles, Thomas Koch and others over biomass feeding, in particular the
> feeding of bagasse.   This topic has also surfaced several times in the
> past.   SRI's James Joyce has recently posted a brief commentary on our
> development work.   My purpose with this brief commentary is to bring the
> gasification community up to speed with where the QBIG gasification
> development and SRI's feeder development is at right now.
> 
> I'm encouraged by Tom Reed's comment on 4 August ".... the world's most
> difficult feeding fuel - raw bagasse from sugar cane".  Chopped straw is
> not too far behind !!!   Our considerable experience with the handling of
> raw bagasse at high rates in Australian sugar mills has told us that over
> many years.  But to the point.  Put simply, SRI and University of
> Queensland, Chemical Engineering (as part of the QBIG gasification
> syndicate) embarked on the development of bagasse gasification technology
> integrated with a sugar mill (that combination provides unique hot fuel gas
> process advantages not found anywhere else) because of a host of technical
> and economic reasons.   Whether those reasons remain strong into the future
> remains to be seen !!!!  But for now these still exist.
> 
> But in setting out on this journey, based on our own extensive experience
> and judgement and with the benefit of the work done elsewhere around the
> world on biomass gasification, we settled on two basic principles to
> underpin our gasifier development (1) the process has to be pressurised
> (although this has yet to be confirmed with detailed engineering, process
> design and costing for Australian circumstances) and (2) we needed a whole
> new feeder for bagasse and cane trash.   Based on the Maui experiences
> directly, on our own long experiences with the screwing of bagasse and the
> commercial operating experiences of a sugar mill feeding bagasse using lock
> hoppers for furfural production, any screw device was not acceptable, and
> other devices including lock hoppers did not fit the goals.  But as Tom has
> said, bagasse being bagasse, you need a damned good feeder to feed bagasse
> whether the pressure is 25 bar or 2 bar (so called atmospheric - although
> rotary valves would be okay here).   Remember that our primary goal in all
> of our development work has been to focus on technology that would deliver
> commercially sustainable plant.  The feeder that we have now developed,
> even though it is quite small, has all of the engineering and process
> features that can be readily scaled-up to the rates that we need for our
> proposed BIG/CC projects in our large Australian sugar mills.  Raw bagasse
> feeding rates of between 20 and 70 t/h per feeder will be required.
> Notwithstanding Thomas Koch's admirable developments with his piston
> feeder, the intermittent piston approach was judged not to be acceptable
> for our goals - we needed continuous feeding at high very rates.
> 
> We have now successfully developed a continuous bagasse feeder that has
> been tested at rates up to about 5 t/h (not sure of the exact figure) for
> test periods of up to two minutes. That is as long a test time as out
> developmental rig will allow us.  Our experimental data tells us that this
> has been more than sufficient time to establish stable and consistent
> operating conditions  in the feeder.  The feeder operations over that time
> also tell us that the real world engineering issues that have to be
> addressed are being addressed, and the feeder can be scaled-up to much
> larger sizes.  The current feeder size was selected to be a direct
> application for our proposed 15 MWt (~ 5 MWe) demonstration gasifier, now
> in the planning stages.  The particular technology for our feeder comes out
> of our extensive experience with the milling of bagasse to extract sugar
> juice.
> 
> I would be happy to provide more information and comment on bagasse feeding
> and gasification in general to those interested as you make contact with me
> directly or through the gasification network.
> 
> Dr Terry Dixon
> Manager Engineering Group
> Sugar Research Institute
> Box 5611
> Mackay MC 4741
> AUSTRALIA
> Ph:  +61 7 49527600
> Fx:   +61 7 49527699
> Mb:  0418 185 309
> email: t.dixon@sri.org.au
> 
> 
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