[Stoves] Continuous gasifier for household scale - experience sharing

Paul Olivier paul.olivier at esrla.com
Tue May 14 17:38:55 CDT 2013


See comments below.

On Tue, May 14, 2013 at 6:03 PM, Tuong DoDuc
<tuong.do at devi-renewable.com> wrote:
> Thanks Paul Oliver,
>
> I went through your presentation several times before.
> I must say that It is very convincing and inspiring as well.
>
> Regarding the continous feed concept, I think it is a trade-off.

It's not really a trade-off of equals. So much depends on the
application. If someone needs to cook a simple meal, why use a
continuous gasifier?
Cooking a meal is generally a batch process. Does it make sense to
situate a complicated and rather large continuous gasifier in an
ordinary household kitchen? It is quite messy to be loading rice hulls
and scrapping out char in a kitchen where food is being prepared. Why
not offer the user a device that is small, lightweight and mobile?

I once designed and tested a "V"-shaped gasifier with updraft and
downdraft barrels. This concept works to a limited extent, but only in
batch mode.
Even then, the syngas contained a lot of CO2.

Rice hulls often have a negative angle of repose, and they easily
bridge when confined to small spaces. The moment bridging occurs, a
lot of CO2 is generated, and the reactor overheats. For this reason it
is ideal that rice hulls are not in motion within the gasification
process.

I also abandoned the the concept of a double-barrel reactor because it
is quite costly to fabricate. Imagine the cost of making such a
reactor in high-quality stainless steel.

Thanks.
Paul

> One one side, we will tell the users all the pros anc cons and let them
> decide to choose what they like.
> In this case, we will leave several different options for the users by a
> field test of different gasifier models.
> The user will tell. At this development stage of the continuous gasifier, I
> can't tell which (batch or continuous) suits the user most. Especially,
> there is no one-size-fits-all solution
>
> Best regards,
>
> Tuong
>
>
> On Tue, May 14, 2013 at 10:12 AM, Paul Olivier <paul.olivier at esrla.com>
> wrote:
>>
>> The moment one goes from batch to continuous, the process gets really
>> complicated. Nothing beats the simplicity of a static batch reactor.
>> It provides ideal gasification conditions. The problem regarding the
>> length of the batch cycle can be overcome if the fuel is densified. If
>> the reactor is filled with pellets, the length of the cycle can be
>> extended to well over five hours. Imagine: for a five full hours, the
>> operator does not have to intervene. There is no loading of rice hulls
>> or scrapping out of biochar during this entire period.
>>
>> https://dl.dropboxusercontent.com/u/22013094/Paper/Presentations/Gasification.ppsx
>> The time to empty, reload and relight a batch reactor is less than one
>> minute.
>> Several reactor tubes can be operated at the same time.
>>
>> Thanks.
>> Paul Olivier
>>
>>
>> On Tue, May 14, 2013 at 8:23 AM, Tuong DoDuc
>> <tuong.do at devi-renewable.com> wrote:
>> > Dear Dr.TLUD, Paul Oliver, and others,
>> >
>> > The team in SNV Vietnam is adopting the continous gasifier model
>> > developed
>> > by Belonio. The manual has been obtained from the CRHET.
>> > Watch our first propotype: http://www.youtube.com/watch?v=xQGS-VQIj5M
>> > We were able to control the fire, load fuel without affecting the fire,
>> > and
>> > easily remove char at the bottom of the reactor.
>> >
>> > We also adopted the computer fan-casing by a cheaper, more popular fan
>> > in
>> > Vietnam (often used for coal and fixed wood stove). Fan costed 2USD
>> > (while
>> > to replicate Belonio's fan-casing, we bought the adapter for 5USD and a
>> > computer fan for 1.5USD)
>> >
>> > However, this is just our first step and we still have so many problems
>> > to
>> > fully control the fire and ease the operation.
>> > 1) For instance, uncontrolled moment happened when combustion occurs
>> > rigt on
>> > top of the fuel hopper, a lot of smoke was produced and later the fire
>> > burnt
>> > the fan.
>> > https://www.dropbox.com/s/43fkjs0axuye4oj/uncontrollable_moment.jpg
>> > https://www.dropbox.com/s/rd1g1cg0a9ue8qt/fan_casing.jpg
>> >
>> > 2) Another problem is that a lot of tar is produced. It deposits on pot
>> > bottom, burner and other part of the stove. That would also harm the
>> > user.
>> > An idea is to create a layer of char in the burner pipe (to filter the
>> > tar).
>> > Not tried yet.
>> >
>> > 3) We observes 5-10% of the gas leaked out through the char removal
>> > door. We
>> > burnt them, but user may not know (or they simply just don't care) that
>> > it
>> > is toxic.
>> >
>> > 4)  One more, it is very hard to control the final minutes of the
>> > gasificatoin process. It always cause inverted combustion to the fuel
>> > hopper.
>> >
>> > By this email, I would like to ask if some of you have done similar work
>> > with continuous gasifier like this to share more experience. We can thus
>> > reduce our time and effort in localizing this technology.
>> >
>> > Best regards,
>> >
>> > Do Duc Tuong,
>> >
>> > Renewable Energy Advisor
>> > SNV Vietnam
>> >
>> >
>> >
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>> >
>>
>>
>>
>> --
>> Paul A. Olivier PhD
>> 26/5 Phu Dong Thien Vuong
>> Dalat
>> Vietnam
>>
>> Louisiana telephone: 1-337-447-4124 (rings Vietnam)
>> Mobile: 090-694-1573 (in Vietnam)
>> Skype address: Xpolivier
>> http://www.esrla.com/
>>
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>
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--
Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/




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