[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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