[Stoves] Oil drum based TLUD for biochar production and water heating

[Paul Anderson]

Darren and Crispin,

I agree with Crispin.

Because you live in a developed society (UK), you can utilize the 
advantages of low-cost, low-energy-consumption technology such as fans 
and blowers and compressed air to accomplish your task more easily.   
You are certainly not limited to the natural-draft chimneys for your 
operation.

I do not totally understand Crispin's description of the
> Rocket Mass Heater heat exchanger. This is a device with a hot central 
> rising pipe insulated from an exterior concentric pipe that loses heat 
> to the environment. 
In theory it is fine.   The only caution is that once you start cooling 
the woodgas (TLUD pyrolytic gases), there can be condensation and 
deposition of tarry stuff.   What you have studied about natural draft 
barrel-size TLUDs is based on "close-coupled combustion" to burn those 
gases promptly.   It all depends on what you want to do with the gases, 
and you wrote that you wanted to heat water.

Heating water sounds simple, but I assure you that there is much to be 
learned and implemented.   Please keep us informed of your progress.

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype:   paultlud    Phone: +1-309-452-7072
Website:  www.drtlud.com

On 5/5/2016 11:32 AM, Crispin Pemberton-Pigott wrote:
> Dear Darren
>
> A couple of suggestions you can try with ease. In your favour is the 
> scale. Some things work better when the device is large.
>
> Secondary air can be introduced into the gas ‎either above the fuel 
> bed and burned elsewhere, or the gas can be piped to a nozzle where 
> air is entrained as it blasts into a burner, perhaps no more than a 
> length of 4" pipe.
>
> At ETHOS a few years ago the GEK gasifier was ‎demonstrated. In terms 
> of scale it is not much different from the barrel. The interesting 
> thing was the velocity of the discharge. It was powerful enough to 
> power the air entrainment.
>
> What I am suggesting is that there be no holes in the upper portion of 
> the drum, that it produce gas under at least the draft pressure 
> generated between the vertical column. That implies running the top at 
> a slight positive pressure which in turn means having a clamp-on lid.
>
> ‎That implemented, you can use the heat in the gas to your advantage. 
> The next idea is to use the device knows as a Rocket Mass Heater heat 
> exchanger. This is a device with a hot central rising pipe insulated 
> from an exterior concentric pipe that loses heat to the environment. 
> This cools the gas and as it does so, it gains density. This increases 
> the draft in the chimney above the reactor. The increased pressure 
> comes from, is powered by, the loss of heat.
>
> The net effect is that the pressure from the closed system is 
> increased beyond that prevailing in the drum. This should allow you to 
> burn the cooled gas in an adjacent burner, not above the drum as you 
> envisaged.
>
> Once you have a cooled gas stream ‎you can burn it as you wish.
>
> Best regards
> Crispin
>
>
>
>
>
> On 5/5/2016 7:37 AM, Darren wrote:
>> Looking to work on a TLUD design based on a standard oil drum 
>> (200-litre drum (known as a 55-gallon drum in the United States and a 
>> 44-gallon drum in the United Kingdom) to produce biochar from well 
>> dried wood.
>>
>> Ideally the stove would have a short chimney so as not to be too high 
>> so that a pot/water tank/oven could be placed above the stove to be 
>> directly heated by the flames.
>>
>> I've had a look about on the internet to see what people have been 
>> building - almost all appear to have an extra 1/3rd of a drum on top 
>> as an 'afterburner' chamber and a reasonably long chimney on top of 
>> this.  Making them rather tall for easily positioning 
>> oven/watertank/pots for direct flame heating.
>>
>> None I have seen have an extra, large metal skin / tube surrounding 
>> the barrel to provide secondary air pre heating (as is done with some 
>> smaller TLUD designs).  I wonder if adding this could reduce the 
>> total working height of the stove.
>>
>> Looking to make something that is nice and clean burning.
>>
>> Current ideas include -
>>
>> * positioning the chimney/riser at one side of the barrel to allow 
>> heating on the rest of the metal surface next to the riser - although 
>> I suspect a large diameter chimney is required, leaving a hot surface 
>> of limited size.
>>
>> * charging the barrel 2/3rds full with fuel leaving the top 1/3rd 
>> empty as an 'afterburner' - having secondary air holes positioned to 
>> jet in air at this height.
>>
>> Interested in any thoughts people have or any efforts people know of 
>> oil drum TLUD designs where people are trying to reduce the height, 
>> use the heat, or provide heated secondary air.
>>
>> Best
>>
>> Darren
>>
>> see our previous biochar stove at 
>> http://www.appropedia.org/Forest_biochar_rocket_stove
>>
>> .
>>
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>
>
>
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