[Stoves] Some Basic Properties of ND-TLUD Gasification

[Frank Shields]

Hi Julien,

I just retired from the lab i worked, got bored and am now setting up a small lab for a composter. So have been looking for inexpensive equipment and found this site for balances. 

http://www.affordablescales.com/laboratory-balances/precision-balances/ <http://www.affordablescales.com/laboratory-balances/precision-balances/>

If you get a short pipe with end caps and weigh it you will know the weight requirements of the more accurate balance you need. 

Suggest weigh the biomass going in the pipe and dump the char-ash after to be weighed. You only need to heat the pipe slowly if you want a reading at 450c. That because the gases coming off can catch fire and if that happens you have lost control of the temperature. But you only need to take the temperature something above 450 and well above is ok. So drop the loaded pipe into a camp fire or surround with burning charcoal with, perhaps aid from a fan. Let the gases ignite. Anything to get temperature above 450c. 

see below….





Frank Shields
franke at cruzio.com


> On Jul 13, 2015, at 5:51 PM, Julien Winter <winter.julien at gmail.com> wrote:
> 
> Hello Frank;
> 
> Thanks for your comments.  You have given me some interesting things to think about.  
> 
> I have sub-samples of my fuels to send of for analysis after I have measured them for thickness.  After that I will have values for ash.  Then I will redo my analysis on a dry ash-free basis.  Since all the fuels were wood, I don't expect they contained much ash, and I don't expect my conclusions to change.  I may be able to get a lab to do a slow heating to 450 °C to get a measure of the maximum amount of char possible.  I can't do that myself, because I don't have that kind of oven.
> 
> As well as particle size (fuel bed pore size), minerals could substantively affect the Tmax vs. %Char relationship.  
If reported on a DAF basis the minerals will be excluded from the calculations. and I would think the percent minerals would need be quite high (>10%?) before effecting combustion characteristics - but not sure. 

> 
> Thermogravemetric analysis shows that most pyrolysis is over by 450 °C, which may match with what you read from Tom Reed.  The high temperatures I measured are indicative of fast heating rates.  Faster heating rates mean more energy available for endothermic reactions creating volatiles.  Higher heating rates lead to less char.
I don’t think its higher temperatures that is reason for less char BUT think it more primary air and increased combustion in the combustion chamber resulting in higher temperatures and less char. 


> 
> I don’t know what the real heating rate of the fuel solids were, because it is dependent not only on the temperature in the fuel bed voids, but also the conduction of heat from particle surfaces inwards.
You have the total time and total cm of packed fuel length of a weight of fuel. Thinking if you have 20 cm column you can calculate the weight of ten cm of that column, start the timer when flame front hits 5cm and continue until front reaches 15cm. Will that not give you the average rate? in cm/sec? or wt/sec?  If you remove a sample of that fuel and pack tight into the pipe and re-heat to 450c you might get an idea of how much terrified wood is left. OR based on the first pipe test using biomass you know how much would be left if no outside air was involved in the combustion therefore if the char (DAF) is found to be more than calculated you know there is terrified wood and if the values is less than the >450c pipe value you know there was burning char taking place. We are not saying this is good or bad - leave that to the end user and what they are doing. But I think monitoring this 450c pipe char value on a DAF basis is a good reference to any future work we want to do or if, for example, we find a fuel-combustion combination works great we can use the findings compared to the 450c pipe reference as a goal for fuel for this specific stove brand.      

> 

> From the thermocouple traces of void temperature, I calculated the heating rate of thermocouples (°C/min).  However, I didn't use the data, because the heating rate of the thermocouples was often slower than the heating rate in the fuel bed, so my observations would be biased.  I understand that it is possible to calculate a rate of temperature rise if you use two thermocouple probes of different thicknesses.  … next time.
I am wondering if the readings are a constant time delayed if that really matters especially if you start the timer when the first one hits max temperature? 

It seems you have a very good set-up for this type of research. Perhaps I can help once I get some equipment - not really sure what the future brings. 

Thanks

Frank


> 
> Cheers,
> Julien.
> 
> -- 
> Julien Winter
> Cobourg, ON, CANADA
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