[Gasification] heat exchangers and gas cooling./ oil ?

Rolf Uhle energiesnaturals at gmx.de
Tue Jan 1 14:53:21 CST 2008 

Happy N Y to all,

this idea of scubbing tar is very old, but works well.
The tarry water can be a problem, although it might soon be a convenience.
My idea is to substitute water by WVO and use it up to saturation with tars 
and ashes.
This will shure give a kind of thick  asphalt like substance with a hv 
close to heavy fuel oil. As long as the chemical industry does not (yet) 
want it, it could be burnt safely in ceramic kilns or any high temp 
furnace.
Question : has this ever been realized ?

Rolf

>             
> -------- Original-Nachricht --------
> Datum: Tue, 1 Jan 2008 10:44:22 +1300
> Von: "Ken Calvert" <renertech at xtra.co.nz>
> An: "Discussion of biomass pyrolysis and gasification" 
> <gasification at listserv.repp.org>
> Betreff: Re: [Gasification] heat exchangers and gas cooling.
> 
>             O.K. you young fellers!  when it comes to gas cleaning and 
> cooling its
> already been done, by emperical methods!
>      So how about someone providing the mathmatical modeling of this
> situation?
>     The I.I.T., in New Delhi, back in the early eighties  produced an
> intregu'ing combination of cyclone gas cleaner and cooler by direct 
> contact
> of  hot gas and cooling water.  The top plate of the cyclone, as well as
> taking the gas exit pipe from its centre was fitted down below the top 
> edge
> of the body casing to make an open topped tank which was kept full of 
> water.
> Around the edge of the top plate there were a series of
> curved slots, which allowed a thin film of water to flow down the inside
> surface of the cyclone and exit from the bottom outlet.  The inlet gas,
> flowing in at right angles to the laminar flow conditions of the water,
> continued to flow tangentially around the cyclone, with a prolonged and 
> intimate contact with the film of water which extracted most of the
> solid particles and heavier tars as well as most of the heat.  The
> centrifugal force keeps the water film intact as a smooth film on the 
> walls 
> of the cyclone and flowing down through the outlet at the bottom of the 
> cone.  The only down side is that even with filtration and constant 
> recycling you still end up with a lot of dirty water,
> loaded with PAHs and all.  With a bit of detergent added, it looks and 
> smells just like the old "Jayes Fluid" in its useable form of a dirty 
> milky 
> emulsion.  The detergent helps in removing the tars.  O.K. Just keep the 
> discussion going!.  Seasons Greetings . Ken Calvert.
> 
> 
> --- Original Message ----- 
> From: <gfwhell at aol.com>
> To: <mark at ludlow.com>; <gasification at listserv.repp.org>
> Sent: Sunday, December 30, 2007 2:02 PM
> Subject: Re: [Gasification] heat exchanger / boiler design book and 
> vortex
> 
> 
> >
> > Mark
> > How would you explain the performance of gasses in a Hilsch Vortex?
> > It would seem that the gas under the influence of centrifugal force
> > behaves in a similar way as any fluid, the denser heavier molecules are
> > thrown to the outside. These molecules would be cooler and more densely
> > packed, the inner core of the Rotating column being hotter.
> > The idea of being able to sort the hot from the cold in the gasifier
> > output sounds rather appealing.
> > There seems to be no definitive explanation of how this Vortex works?
> >
> > GF
> >
> >
> >
> >
> > -----Original Message-----
> > From: Mark Ludlow <mark at ludlow.com>
> > To: 'Discussion of biomass pyrolysis and gasification'
> > <gasification at listserv.repp.org>
> > Sent: Tue, 25 Dec 2007 10:58 pm
> > Subject: Re: [Gasification] heat exchanger / boiler design book
> >
> >
> >
> >
> > Toby,
> >
> > "Swirling fins" do not increase residence time. Mass flux remains
> > constant.
> > They increase the velocity of the gases which increases their Reynolds
> > Number which increases the probability that flow will be turbulent.
> >
> > Observe the difference in velocity profiles between laminar and 
> turbulent
> > flow. The velocity profile for laminar flow is parabolic, meaning that 
> the
> > core of the flow-stream (portion of greatest mass transfer per unit of
> > time)
> > has much higher velocity than the "tails" of the parabola. Therefore, 
> much
> > less heat is transferred to this part of the flow stream because it has 
> a
> > short residence time (and it is further removed from the heat-transfer
> > surfaces).
> >
> > Fully-developed non-laminar flow streams have a flatter velocity 
> profile.
> > This is because there are fluid molecules moving in all directions at 
> once
> > and the velocity profile described is a two-dimensional average of 
> these
> > velocities. In general, higher fluid velocities imply higher rates of 
> heat
> > transfer. The faster the velocity, the thinner the boundary layer 
> through
> > which heat transfer that is purely conductive becomes.
> >
> > Higher velocity fluid streams also tend to result in less fouling of 
> heat
> > exchange surfaces.
> >
> > Mark
> >
> > -----Original Message-----
> > From: gasification-bounces at listserv.repp.org
> > [mailto:gasification-bounces at listserv.repp.org] On Behalf Of Toby 
> Seiler
> > Sent: Tuesday, December 25, 2007 6:24 PM
> > To: list at sylva.icuklive.co.uk
> > Cc: gasification at listserv.repp.org
> > Subject: Re: [Gasification] heat exchanger / boiler design book
> >
> > Andrew,
> >
> >  Please clear up something for me.  Not long ago there was a discussion
> > about heat exchanger design that I did not understand the principles
> > members
> > put forth.  Specifically I have believed that minimization of the 
> boundary
> > layer effect would increase the heat transfer, know to me as wiping the
> > surface.  Your forth element, surface texture, would have a large 
> effect
> > as
> > would flow, (ranging from laminar to turbulent) were increased or
> > decreased
> > (given other parameters remained the same).
> >
> >  I think the argument was made that turbulent flow transferred better.
> > That's what I didn't understand.  I have always thought that laminar 
> flow
> > over the surface were more efficient at the transfer and that more
> > molecules
> > would be moved if laminar low were maintained.  Please clarify that for 
> me
> > as a general principle, if you have it at hand.
> >
> >  For example;  the fire tubes of a boiler will often contain swirling 
> fins
> > that cause a circular or spiraling flow.  Both residency time and 
> surface
> > contact are extended and the centrifugal force is a factor.  The wiping
> > action reduces the boundary effect and also extends the flow path, 
> giving
> > more contact and transfer.  Flow would be laminar however.  It has long
> > been
> > my belief that making turbulent flow led to hot spots (much increased
> > boundary layer in places), less flow and ultimately less system
> > efficiency.
> > This has led me to believe that a cyclone and heat exchanger combined
> > would
> > be efficient, especially with hot gas heat being transfered to a wood
> > fuel.
> >
> >
> >  Have a good New Year!
> >
> >  Toby Seiler, Seilertechco
> >
> >
> > ---------------------------------
> > Be a better friend, newshound, and know-it-all with Yahoo! Mobile.  Try 
> it
> > now.
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