[Gasification] Sawdust agglomeration
John Hofmeyr
john-h at global.co.za
Tue Aug 15 10:50:16 CDT 2006
Starting a new thread based on submissions in Gasification Digest, Vol 2, Issue 23: On the subject of agglomerating sawdust for gasification, but also for other processing I guess (would the "stoves" list be interested?):
Aaron wrote: "... From what I have studied the sawdust will pack to tightly and not allow the downdraft gasifier to work correctly ..."
Jeff wrote "... You may want to look into pelleting or agglomerating your sawdust ..."
and Aaron replied: "... the sawdust needed to be at a specific moisture content ..."
I think Aaron is correct. As I understand it, the agglomerated sawdust exits the high-pressure environment of the extruder barrel at a temperature well above the boiling point of water. The high temp and pressure are required in order to melt the lignins and hence "glue the particles together". Then the pellets will survive much handling and transport before they are finally sold. If there is excessive moisture present as the pellets exit the extruder barrel, it will vaporise and cause the pellets to disintegrate.
There are two additional advantages: (a) the freight cost is lower if the bulk density is higher and (b) the CV of the fuel is higher if the moisture content is lower.
But I think these are not important requirements if the sawdust is to be mildly agglomerated so the pieces are just strong enough to survive the gasification process. i.e. without the sizing, cleaning and drying processes which occur upstream of commercial-scale barrel-and-screw extrusion plants.
Any experience?
John in Joburg.
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Today's Topics:
1. Gasification of sawdust (Gm Parts Source)
2. Bourke Engine For Biomass Gasification Power Generation?
(Mark & Elena Gallmeier)
3. Help with Heating Gasifier design (Starting to get confused)
(Steve Carroll)
4. Re: Help with Heating Gasifier design (Starting to
getconfused) (Shaun)
5. Re: Gasification of sawdust (Jeff Davis)
6. Re: Fw: Biomass heated ethanol plants (Mark Ludlow)
7. Re: Fw: Biomass heated ethanol plants (Michael Redler)
8. Re: Gasification of sawdust (Gm Parts Source)
9. Re: Help with Heating Gasifier design (Starting to
getconfused) (Steve Carroll)
----------------------------------------------------------------------
Message: 1
Date: Mon, 14 Aug 2006 13:02:18 -0400
From: "Gm Parts Source" <abryer at gmail.com>
Subject: [Gasification] Gasification of sawdust
To: <gasification at listserv.repp.org>
Message-ID: <04ab01c6bfc3$68206800$3f0aa8c0 at Home.NHCustoms.com>
Content-Type: text/plain; charset="us-ascii"
Hello All,
I have just begun to study wood gasification. I am looking to
build a small gasifire to run an Internal combustion Engine (less than 100
Cubic Inches). All of the small scale gasifies that I have studied use a
downdraft type system where the fuel and air enter from the top and the
vacuum of the engine maintains the air flow. The drawback with this system
is fuel size. I have an abundant amount of sawdust that I want to use as the
fuel. However From what I have studied The sawdust will pack to tightly and
not allow the downdraft gasifire to work correctly. I was hoping to get some
information on how to create a small scale gasifire to gasify sawdust. Any
help would be appreciated.
Thanks
Aaron
------------------------------
Message: 2
Date: Mon, 14 Aug 2006 13:17:43 -0400
From: "Mark & Elena Gallmeier" <mgallmeir at comcast.net>
Subject: [Gasification] Bourke Engine For Biomass Gasification Power
Generation?
To: <gasification at listserv.repp.org>
Message-ID: <00e401c6bfc5$8e12ff30$6402a8c0 at c9y1p2>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
To all,
Has anyone here had any hands-on experience with "Bourke" engines? Or even
know anyone who does?
http://www.bourke-engine.com/general_info.htm
http://bourkeengine.net/home.htm
http://bourke-engine-project.com/index2.html
A friend told me about the Bourke Engine recently. When I checked out
Bourke engine researchers with websites, I noticed they were testing their
engines using electric generators.
Regards,
Mark
------------------------------
Message: 3
Date: Mon, 14 Aug 2006 15:11:14 -0700 (PDT)
From: Steve Carroll <luxthreads at yahoo.com>
Subject: [Gasification] Help with Heating Gasifier design (Starting to
get confused)
To: gasification at listserv.repp.org
Message-ID: <20060814221114.78966.qmail at web60714.mail.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello List,
I am about to build a wood gasifying furnace to be used for home heating. Most of the information that I find is about power generating gasifiers or small cookstoves. I keep thinking that I have a good design but I'm never 100% sure that it will work the way I intend it to.
I have attached 3 small drawings (about 6k each and scanned for viruses) that show a basic design of what I am attempting. The only differences between them is where the primary and secondary air is introduced. The goal for this process is to create as much heat as possible and to burn all of the wood, charcoal, tar, and gas before leaving the gasifier.
In drawing 1, I imagine that the primary air will be sufficient for pyrolysis to occur in the area above the burning char. The secondary air should have enough flow to burn the charcoal, tars, and gasses. My concern with this one is that the woodgas will ignite as soon as it contacts the secondary air and somehow cause a dirty combustion of tars and unpyrolysized wood.
In drawing 2, primary air is introduced at the top again with enough airflow to allow for pyrolysis, the burning of charcoal and tar. The woodgas does not ignite until it comes in contact with sufficient preheated secondary air. My fear here is that the charcoal and tars will not burn completely and that it might be hard to preheat the secondary air enough to ignite the woodgas.
Drawing 3 is the same as drawing 2 but the primary air inlets are located in the burning char zone. Perhaps this would ensure that the primary air is mostly used to burn the charcoal so that the woodgas does not ignite until being introduced to the secondary air stream. I am concerned about having enough primary air for the pyrolysis area.
Is it possible that I need a third air inlet?
My design at this moment is a large box made of 1/4" plate steel and lined with insulating refractory. It should put out about 50,000 BTUs and burn 7.2 lbs of wood an hour. The primary air would be set to about 12 cfm and the secondary air to about 60 cfm. After reading a paper on superficial velocity in downdraft gasifiers I sized the throat area to give an air velocity of 86 fpm in hopes of achieving fast pyrolysis. I'm probably making a terrible assumption that the superficial velocity will be something close to the calculated air velocity so I made the throat area adjustable.
Would you all be kind enough to set me straight on where my inlets should be and if there are any glaring mistakes in my overall plan?
One more question that I have is how hot should my secondary air be? I plan to use stainless heat exchanger tubing to preheat the secondary air but how hot it needs to be can help me decide where to run it.
Thanks,
Steve
---------------------------------
Stay in the know. Pulse on the new Yahoo.com. Check it out.
------------------------------
Message: 4
Date: Mon, 14 Aug 2006 19:43:16 -0300
From: "Shaun" <engineer at arnet.com.ar>
Subject: Re: [Gasification] Help with Heating Gasifier design
(Starting to getconfused)
To: "Steve Carroll" <luxthreads at yahoo.com>,
<gasification at listserv.repp.org>
Cc: "Ing. Chem. P. Maya" <alemaya2004 at yahoo.com.ar>, "Richard Hallett
\(Oil UK\)" <richard at hallettoil.co.uk>
Message-ID: <005601c6bff3$09755380$49842dc8 at particuldeda56>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
No drawings attached Steve, can you please resend with drawings so that I
can have a look at your set up? Thanks.
Shaun.
----- Original Message -----
From: "Steve Carroll" <luxthreads at yahoo.com>
To: <gasification at listserv.repp.org>
Sent: Monday, August 14, 2006 7:11 PM
Subject: [Gasification] Help with Heating Gasifier design (Starting to
getconfused)
> Hello List,
>
> I am about to build a wood gasifying furnace to be used for home heating.
> Most of the information that I find is about power generating gasifiers or
> small cookstoves. I keep thinking that I have a good design but I'm never
> 100% sure that it will work the way I intend it to.
>
> I have attached 3 small drawings (about 6k each and scanned for viruses)
> that show a basic design of what I am attempting. The only differences
> between them is where the primary and secondary air is introduced. The
> goal for this process is to create as much heat as possible and to burn
> all of the wood, charcoal, tar, and gas before leaving the gasifier.
> In drawing 1, I imagine that the primary air will be sufficient for
> pyrolysis to occur in the area above the burning char. The secondary air
> should have enough flow to burn the charcoal, tars, and gasses. My
> concern with this one is that the woodgas will ignite as soon as it
> contacts the secondary air and somehow cause a dirty combustion of tars
> and unpyrolysized wood.
>
> In drawing 2, primary air is introduced at the top again with enough
> airflow to allow for pyrolysis, the burning of charcoal and tar. The
> woodgas does not ignite until it comes in contact with sufficient
> preheated secondary air. My fear here is that the charcoal and tars will
> not burn completely and that it might be hard to preheat the secondary air
> enough to ignite the woodgas.
>
> Drawing 3 is the same as drawing 2 but the primary air inlets are located
> in the burning char zone. Perhaps this would ensure that the primary air
> is mostly used to burn the charcoal so that the woodgas does not ignite
> until being introduced to the secondary air stream. I am concerned about
> having enough primary air for the pyrolysis area.
>
> Is it possible that I need a third air inlet?
>
> My design at this moment is a large box made of 1/4" plate steel and
> lined with insulating refractory. It should put out about 50,000 BTUs and
> burn 7.2 lbs of wood an hour. The primary air would be set to about 12
> cfm and the secondary air to about 60 cfm. After reading a paper on
> superficial velocity in downdraft gasifiers I sized the throat area to
> give an air velocity of 86 fpm in hopes of achieving fast pyrolysis. I'm
> probably making a terrible assumption that the superficial velocity will
> be something close to the calculated air velocity so I made the throat
> area adjustable.
>
> Would you all be kind enough to set me straight on where my inlets should
> be and if there are any glaring mistakes in my overall plan?
>
> One more question that I have is how hot should my secondary air be? I
> plan to use stainless heat exchanger tubing to preheat the secondary air
> but how hot it needs to be can help me decide where to run it.
>
>
> Thanks,
> Steve
>
>
> ---------------------------------
> Stay in the know. Pulse on the new Yahoo.com. Check it out.
--------------------------------------------------------------------------------
> _______________________________________________
> Gasification mailing list
> Gasification at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org
> http://www.repp.org/discussiongroups/resources/gasification
--------------------------------------------------------------------------------
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Checked by AVG Free Edition.
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------------------------------
Message: 5
Date: Mon, 14 Aug 2006 19:13:17 -0400 (EDT)
From: "Jeff Davis" <jeff0124 at velocity.net>
Subject: Re: [Gasification] Gasification of sawdust
To: gasification at listserv.repp.org
Message-ID: <16526.152.50.3.3.1155597197.squirrel at www.velocity.net>
Content-Type: text/plain;charset=iso-8859-1
Hi Aaron,
You may want to look into pelleting or agglomerating your sawdust.
Jeff
> I have an abundant amount of sawdust that I want to use as
> the
> fuel. However From what I have studied The sawdust will pack to tightly
> and
> not allow the downdraft gasifire to work correctly.
--
Jeff Davis
Some where 20 miles south of Lake Erie, USA
------------------------------
Message: 6
Date: Mon, 14 Aug 2006 21:38:53 -0700
From: "Mark Ludlow" <mark at ludlow.com>
Subject: Re: [Gasification] Fw: Biomass heated ethanol plants
To: "'Ken Basterfield'" <ken at basterfield.com>, "'Peter Singfield'"
<snkm at btl.net>, <gasification at listserv.repp.org>
Message-ID: <03de01c6c024$b6742b20$0500a8c0 at AV2>
Content-Type: text/plain; charset="us-ascii"
The issue is that, plus, depending on the heat transmitivity of the
insulation, at some point the losses from convection and radiation can
actually be increased. A pipe insulated with poor insulation has increased
area from which to radiate energy. As the diameter is increased with
insulation, the Grashof Number increases (to D^3; D is a characteristic
diameter) and convective heat transfer also increases.
A poor insulation with a low resistance to conduction will actually increase
heat loss because it has a larger characteristic diameter and more surface
from which to radiate energy. Past the critical thickness this is not an
issue; economics is, however.
Mark
-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] On Behalf Of Ken Basterfield
Sent: Sunday, August 13, 2006 1:52 PM
To: 'Peter Singfield'; gasification at listserv.repp.org
Subject: Re: [Gasification] Fw: Biomass heated ethanol plants
Hello Mike & Peter,
Ok,
is it simply that the cost of extra layers of insulation can never be
recovered at such lowering heat losses?
ken
------------------------------
Message: 7
Date: Tue, 15 Aug 2006 05:31:02 -0700 (PDT)
From: Michael Redler <redlerm at yahoo.com>
Subject: Re: [Gasification] Fw: Biomass heated ethanol plants
To: gasification at listserv.repp.org
Message-ID: <20060815123102.11318.qmail at web51313.mail.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
Look at the graph at:
http://www.eng.fsu.edu/~shih/eml3016/lecture-notes/thermal%20bubble%20jet/sld011.htm
A picture speaks a thousand words.
At the far right, it actually shows better conduction with "lots of" insulation than with none at all.
Mike
Mark Ludlow <mark at ludlow.com> wrote:
The issue is that, plus, depending on the heat transmitivity of the
insulation, at some point the losses from convection and radiation can
actually be increased. A pipe insulated with poor insulation has increased
area from which to radiate energy. As the diameter is increased with
insulation, the Grashof Number increases (to D^3; D is a characteristic
diameter) and convective heat transfer also increases.
A poor insulation with a low resistance to conduction will actually increase
heat loss because it has a larger characteristic diameter and more surface
from which to radiate energy. Past the critical thickness this is not an
issue; economics is, however.
Mark
-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] On Behalf Of Ken Basterfield
Sent: Sunday, August 13, 2006 1:52 PM
To: 'Peter Singfield'; gasification at listserv.repp.org
Subject: Re: [Gasification] Fw: Biomass heated ethanol plants
Hello Mike & Peter,
Ok,
is it simply that the cost of extra layers of insulation can never be
recovered at such lowering heat losses?
ken
------------------------------
Message: 8
Date: Tue, 15 Aug 2006 09:31:51 -0400
From: "Gm Parts Source" <abryer at gmail.com>
Subject: Re: [Gasification] Gasification of sawdust
To: <gasification at listserv.repp.org>
Message-ID: <04e001c6c06f$2b166a70$3f0aa8c0 at Home.NHCustoms.com>
Content-Type: text/plain; charset="us-ascii"
Hi Jeff,
Thanks for your reply. I have looked into the pelleting but what I
found was that the sawdust needed to be at a specific moisture content is
this true? I am interested into looking into this more. One of the other
things that I have an abundance in addition to the sawdust is bark and very
course sawdust. It would be great to be able to use that to make gas as well
Do you know of any good online resources where I can study the pelleting
process and the working pressures needed to get the sawdust to stay
pelleted?
Thanks
Aaron
>Hi Aaron,
>
>You may want to look into pelleting or agglomerating your sawdust.
>
>
>Jeff
------------------------------
Message: 9
Date: Tue, 15 Aug 2006 06:55:13 -0700 (PDT)
From: Steve Carroll <luxthreads at yahoo.com>
Subject: Re: [Gasification] Help with Heating Gasifier design
(Starting to getconfused)
To: gasification at listserv.repp.org
Message-ID: <20060815135513.95938.qmail at web60721.mail.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
I just posted them here: http://luxthreads.tripod.com/gasifier.html
Sorry about the attachments. I thought that attachments were allowed but I can't find anything on how to go about sharing pictures on the list or about general etiquette and rules.
Thanks for your patience,
Steve
No drawings attached Steve, can you please resend with drawings so that I
can have a look at your set up? Thanks.
Shaun.
> Hello List,
>
> I am about to build a wood gasifying furnace to be used for home heating.
> Most of the information that I find is about power generating gasifiers or
> small cookstoves. I keep thinking that I have a good design but I'm never
> 100% sure that it will work the way I intend it to.
>
> I have attached 3 small drawings (about 6k each and scanned for viruses)
> that show a basic design of what I am attempting. The only differences
> between them is where the primary and secondary air is introduced. The
> goal for this process is to create as much heat as possible and to burn
> all of the wood, charcoal, tar, and gas before leaving the gasifier.
> In drawing 1, I imagine that the primary air will be sufficient for
> pyrolysis to occur in the area above the burning char. The secondary air
> should have enough flow to burn the charcoal, tars, and gasses. My
> concern with this one is that the woodgas will ignite as soon as it
> contacts the secondary air and somehow cause a dirty combustion of tars
> and unpyrolysized wood.
>
> In drawing 2, primary air is introduced at the top again with enough
> airflow to allow for pyrolysis, the burning of charcoal and tar. The
> woodgas does not ignite until it comes in contact with sufficient
> preheated secondary air. My fear here is that the charcoal and tars will
> not burn completely and that it might be hard to preheat the secondary air
> enough to ignite the woodgas.
>
> Drawing 3 is the same as drawing 2 but the primary air inlets are located
> in the burning char zone. Perhaps this would ensure that the primary air
> is mostly used to burn the charcoal so that the woodgas does not ignite
> until being introduced to the secondary air stream. I am concerned about
> having enough primary air for the pyrolysis area.
>
> Is it possible that I need a third air inlet?
>
> My design at this moment is a large box made of 1/4" plate steel and
> lined with insulating refractory. It should put out about 50,000 BTUs and
> burn 7.2 lbs of wood an hour. The primary air would be set to about 12
> cfm and the secondary air to about 60 cfm. After reading a paper on
> superficial velocity in downdraft gasifiers I sized the throat area to
> give an air velocity of 86 fpm in hopes of achieving fast pyrolysis. I'm
> probably making a terrible assumption that the superficial velocity will
> be something close to the calculated air velocity so I made the throat
> area adjustable.
>
> Would you all be kind enough to set me straight on where my inlets should
> be and if there are any glaring mistakes in my overall plan?
>
> One more question that I have is how hot should my secondary air be? I
> plan to use stainless heat exchanger tubing to preheat the secondary air
> but how hot it needs to be can help me decide where to run it.
>
>
> Thanks,
> Steve
>
>
> ---------------------------------
> Stay in the know. Pulse on the new Yahoo.com. Check it out.
--------------------------------------------------------------------------------
> _______________________________________________
> Gasification mailing list
> Gasification at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org
> http://www.repp.org/discussiongroups/resources/gasification
--------------------------------------------------------------------------------
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