[Gasification] Fluidised bed reactor
GFWHELL at aol.com
GFWHELL at aol.com
Sat Nov 30 13:45:47 CST 2013
The "recycling " of CO2 within the gasifier sounds very interesting because
CO2 can be converted into methane under the right conditions, presumably
in the presence of steam and a catalyst at high temperature.
I was informed on this site that IC engines were not able to deal with an
enriched oxygen fuel mix and required large quantities of "energy
absorbing" nitrogen to keep them running. or else the valves would burn out or
reasons of that nature. This is a pity because the exhaust would be of a much
higher value for gas making. This would also be true if the input supply of
air to the gasifier was devoid of nitrogen.
By comparison the gasifier would only need to be 1/5th in size if it was
designed to deal with oxygen only in order to burn its fuel.
This would require a pressure/adsorption system for the provision of
primary air for combustion,
These devices are not that complicated, requiring a compressor and a couple
of pressure vessels containing
the correct zeolite together with a plumber.
A simple test of this process would be to take your plastic welding
electrically heated welding torch and connected to a supply of CO 2 .attach the
nozzle to a suitable "reaction chamber" (capped water pipe"containing your
Biomass, switch on and vaporize the contents with your electrically heated CO
2
Test the value of the output, then do a second test using compressed air
for comparison.
GFWHELL
In a message dated 11/30/2013 12:39:04 P.M. Eastern Standard Time,
pannirbr at gmail.com writes:
Dear Tom , Thomas , Jim
Tom said
By injecting exhaust into the gasifier you are recycling a lot of inert
gas (CO2, N2) and very little heat
If the engine use pyrogas derived syngas not much c02 and less No2c
problems from combustion exhaust gas thus the out put c02 exhaust can be
sucessfly used upt0 30 porcent recycling back both enegy and co2, for
gasification . more than this amount othewise there can be co2 and N2 build up
,rightly pointed out by tom as there is closed loop via direct c02v with
no purge
The possibilty of integrated innovative design very urgent indeed , the
closed c02 to co looping via combustion and chacoal gasification .We
believe that the gasification of chacoal with exchaust gas can reduce the
c02 to c0. both via indirect pyrlysis one sucg as GEK gasifier and also
co2 and h2 chacoal gasifiction as done done well by recent DTU viking
gasifier reactors need futher study regarding energy integration.
int his context milled charcoal cola with exhaust co2 and steam via
spouted or fluidezed bed gasification can play key role to arrive at practical
technology . However c02 and c0 equilibrium temperature limited one , mass
transfer and heat rnsfer problems need to be understood before one arrive
practical small sacle fluidized bed gasifier.
Tom know well than any other that Brazilian ceramic bricks made low cost
gasogen was very much pracical energy generator iduring second wor lwar
even in remote place of Brazil, now chinese doing more work with low cost
charcoal gasifier.The pyrogas economy , charcoal economy ,syngas sofc fuel
all very mature to become reality to decentralized bioenergy small smart
grid power.Inthis context pyrolysis reactor as weel spouted bed
gasification can make possible the smaal biopower competetive with large scale
Yours sincerly with kind regards
Pannirselvam P.V, Brasil
ᐧ
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On Sat, Nov 30, 2013 at 6:34 AM, Thomas Koch <_tk at tke.dk_
(mailto:tk at tke.dk) > wrote:
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Tom
I agree very much to your description of the status of FB gasifiers.
Not real upscaleable to an interesting size - to many operations problems
- too big carbon or thermal losses and too dirty gas to real interesting !
The 2 Danish FB biomass gasifier - Pyroneer and Skive are struggling a
real lot with gas cleaning.
Do you have any idea of the status of the Viking gasifier development?
I have asked several times if it is possible to visit the plant for over 2
years - or if there is a public report available with a little data?? but
no luck sofar.
The last information I have from the project is from linked-in where saw
that the only engineer I knew on the project have left this summer.
Best regards
Thomas Koch
-----Oprindelig meddelelse-----
Fra: Gasification [mailto:_gasification-bounces at lists.bioenergylists.org_
(mailto:gasification-bounces at lists.bioenergylists.org) ] På vegne af Tom
Miles
Sendt: 30. november 2013 07:01
Til: 'Kevin'; 'Discussion of biomass pyrolysis and gasification'
Emne: Re: [Gasification] Fluidised bed reactor
If you want to use the engine exhaust in a gasifier you must consider the
heat and material balance for a gasifier and IC engine.
Fuel input 100%
Heat loss in FB gasifier 5%
(Sensible) Heat loss to cooling the gas 25% Cold clean gas efficiency to
engine 70% (20% C0, 20% H2, 2% CH4, 12% CO2, 44% N).
Heat conversion in engine ~25%
33% to power (~14-17% fuel to power)
33% to engine jacket heat (17% net)
33% to exhaust. (17% net, mostly CO2 and N)
By injecting exhaust into the gasifier you are recycling a lot of inert
gas (CO2, N2) and very little heat. The best use of the exhaust gas heat may
be in preconditioning the fuel. Danish Technological University (DTU Viking
gasifier, 1990-2010, that is now being commercialized by Weiss) and later
All Power Labs (Power Pallet, 2009) have used heat from the exhaust to
indirectly dry and pyrolyze incoming fuel. The dried and partially
devolatilized wood, along with preheated combustion air, appears to contribute to a
stable oxidation zone. Both units make a very good quality gas. These are
both fixed bed downdraft gasifiers with pre-pyrolysis zones.
Peak temperatures reach 1000 C-1200 C in the oxidation zone and 800-900C
in the reduction zones.
_http://www.btgworld.com/en/references/publications/handbook-biomass-gasific
a
tion-second-edition_
(http://www.btgworld.com/en/references/publications/handbook-biomass-gasification-second-edition)
We have worked with many fluidized bed gasifiers in research and in
industrial applications, for producer gas, and for synthesis gas. The fluidized
bed is an intriguing reactor that has its use in industrial applications but
they are expensive to build and operate.
Fluidized bed (FB) gasifiers are unique because distributor plates or
nozzles in the bed uniformly distribute the reactant (air, steam) in the sand
(or media) bed. It is therefore imperative that the fuel be distributed
uniformly for good gasification. This good distribution affords good
temperature control as the fuel goes through the exo- and endo- thermic reactions
that Kevin described. The ideal arrangement is to feed the fuel into the bed
and allow sufficient time (depth) for it to completely react before breaking
the surface into the vapor space above the bed. Of course there are
variations on fluidized bed reactors such as spouted beds, fast beds, or
entrained flow reactors. The latter are used for fast pyrolysis to liquid fuels by
companies like Ensyn. I think that Dynamotive is the only company that uses
a bubbling bed for pyrolysis. Many of the biomass to liquid reactors co
nsumes the char to drive the process so there is no excess char
When used for gasification fluidized beds can be pretty stable in the
650-750 C range. The higher temperatures are needed to provide thermal
inertia when wetter fuel (>20% MC) is used. Higher temperatures are generated
by adding oxidants as Kevin has described. Higher vapor space temperatures
(750 C) can be achieved by adding air above the bed. The partial oxidation
can reduce NOx precursors in the fuel gas. You can think of the heat
balance as consuming between 25% and 33% of the fuel to convert the remainder to
chemical (producer gas or syngas) and sensible energy.
Producer gas is burned directly in a boiler or reformed for use in engines.
Synthesis gas is usually made using enriched air or oxygen as the reactant
or by indirect heating, as in a dual fluid bed. The variety of catalytic
reformers used to make synthesis gases can be seen online in the
presentations at the TC Biomass 2011 and 2013 conferences.
http://www.gastechnology.org/tcbiomass2013/Pages/2013-Presentations.aspx
There are a few small commercial (50-100 tpd) fluidized bed/entrained flow
pyrolyzers that are making specialized products (liquid smoke) for the
food industry. In general there are no commercial small scale fluidized bed
gasifiers or combustors.
Attempts by US boiler makers and several small entrepreneurs have failed
to sustain commercial operation of fluidized bed gasifiers or combustors at
the small scale.
Tom Miles
-----Original Message-----
From: Gasification [mailto:_gasification-bounces at lists.bioenergylists.org_
(mailto:gasification-bounces at lists.bioenergylists.org) ] On Behalf Of Kevin
Sent: Friday, November 29, 2013 9:23 AM
To: Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] Fluidised bed reactor
Dear Rex
----- Original Message -----
From: "Rex Zietsman" <_rex at whitfieldfarm.co.za_
(mailto:rex at whitfieldfarm.co.za) >
To: <_gasification at lists.bioenergylists.org_
(mailto:gasification at lists.bioenergylists.org) >
Sent: Friday, November 29, 2013 4:18 AM
Subject: [Gasification] Fluidised bed reactor
> Kevin,
>
> What you say is correct. However, there is benefit in returning some
> exhaust
> back to gasification as you force a higher production of CO relative to
> CO2
> production. I suspect it is an equilibrium thing...
# For a gasifier having a relatively high exit temperature, then engine
exhaust additions to the gasifier intake air could indeed be a way to both
lower the gasifier exit temperature, and to raise the CO level.
There is a CO/CO2 equilibrium consideration, and also a kinetics or "speed
of reaction" consideration.
Best wishes,
Kevin
>
> Rex
>
>
> ---
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