[Stoves] Good enough stove?

Tue Nov 24 06:26:47 CST 2015

Frank,

I (and probably others) are reading with interest your dialog with 
Crispin.   Important stuff (but outside of my comfort zone for 
contributing.)   Let's see where this leads us.

I would appreciate some comments about the change in the volatile matter 
(and other issues) when char is created at 450 C vs 550 C vs 650 C (or 
other key temperatures).   You have pointed out the importance of E 450 
(energy in 450 degree C Char).   But is it changing much when created at 
higher temps?  We generally say that TLUD char is 550 or 600 C char.

How much are these differences going to impact the discussion you are 
having with Crispin?   I suspect that above 450 C, the weight loss of 
higher temp chars is closely proportional to the energy lost when that 
weight was lost.   If that is not correct, then the calculations you 
are  discussing with Crispin have an additional complication, which is 
the temperature at which the resultant char was formed.

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 11/24/2015 12:09 AM, Frank Shields wrote:
> Dear Crispin, Stovers,
>
> Please see below:
>
>> On Nov 23, 2015, at 11:25 AM, Crispin Pemberton-Pigott 
>> <crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
>>
>> Dear Frank
>> There is a guy in India who is contributing to the work of Working 
>> Group 3 (Field Testing) who says he can give me an ultimate analysis 
>> of any biofuel based on 4 measurements.
>
> Does he have a TGA and CHN analyzer? or calorimeter?
>
>
>> It reminds me of the work of Dr Tom Reed who proposed a general case 
>> for all biomass composition. On an ash-free dry basis, all biomass is 
>> substantially the same, and when factoring in the volatile %, a 
>> ‘pretty good guess’ can be made for the overall composition.
>
> Well this is where we really differ. We are talking biomass fuels 
> ranging from manures to Richards formulated pressed fuels. Nothing you 
> can look up. And all tests must be directly related to the fuel being 
> used or we waste our time and lots of room for corruption. So we need 
> to determine total energy, volatile matter at 550c and volatile energy 
> 450C (under N2). Can he give us those values with a TGA? And a 
> calorimeter to give total energy dry wt? If not we can go through the 
> motions with your book values and see how things work.
>
> What I do believe is the same is the energy value of the char (under 
> N2 -DAF) values. It is between 80 and 90% carbon with one % hydrogen 
> and the rest oxygen. I am suggesting giving that value 85%C, 1% H  to 
> use in calculating for the energy of that fraction. That will be our 
> biggest variable but because all will be using it and that a much 
> larger energy fraction will go off as the volatiles (450c in N2) and 
> that only a percentage of this energy value is used in the 
> calculations for what is used to ‘boil the water’ task - it is a small 
> error.
>
> For example:
> Total dry sample is 100g (1800kj)
> Ash 8g
>
>
> Volatile fraction 75g (450c-N2)(1800-510=1290kj)
>
>
>
> Fixed sample 25g
> Fixed sample DAF 17g
> Estimating:
> (510kj) (using 30kj/g)
>
>
> Estimating:
> This is 85% carbon (14.5 g C) and <1% H (0.17g)
>
> The carbon goes from Solid-C > CO and
> CO > CO2 both releasing energy.
>
> ****What I want help with is how to determine the percentage of the 
> energy from the 14.5g carbon that is released when converting to CO 
> and the rest of the energy from CO -> CO2. Not sure if its Bond Energy 
> or Enthalpy to use for the calculations?
>
> and what is the bond energy required to remove a carbon from a 
> graphite sheet? I think its held with three bonds and the fourth 
> holding the sheets together without a ‘bond’. That is C (three bonds C 
> = 960 kj/mol or 960/12 = 80g??
>
> O2 has a bond energy of 498 kj/mol or 498/16 = 31.1 kj/g?? or is it 
> 498 = 15.6??
>
>
>
> Thanks for any help.
>
> Regards
>
> Frank
>
>
>
>
>
>> In that case, using a formula I dug out of a moldy book, I can 
>> calculate the energy content of the fuel by adding in the ash and 
>> moisture again.
>
>
>
>
>
>
>
>
>> How well this applies to dung and highly processed fuels, I don’t 
>> know. It will be helpful to compare the theory and practice of this 
>> and your (and other?) approaches. It will make the science of stoves 
>> more accessible.
>> I am offline for a little while.  We will pick this up again in Beijing.
>> Regards
>> Crispin
>> Dear Crispin,
>> Interesting. A single stove with different inserts and a collection 
>> of fuels that are often mixed. Lets not make it easy!
>> Any combination of 1) fuels (and fuel mixes) and 2) stove inserts for 
>> any 3) task that actually works can be tested. For example if you 
>> fill a TLUD with cow manure it likely will not complete a task of 
>> boiling seven liters of water for an hour - so no need to test.
>> So gather your one stove with insert, your one fuel (or mix) and 
>> state the one task and test to make sure the task can be completed.
>> The fuel description is two parts:
>> 1) the general physical description of type, size, shape, bark 
>> included, etc to gather fuel as close to that being used as possible.
>> 2) then fine tune the fuel by normalizing energy values using the two 
>> volatile ones and the char (DAF) and moisture.
>> And make sure the task has a sharp end point when completed so to 
>> stop the clock.
>> So if you have a calorimeter to get total energy and a furnace with 
>> pipes to determine volatile energy and can ash samples to determine 
>> char DAF content (without ash included) we are ready to go.
>>  Regards
>> Frank
>> Frank Shields
>>> On Nov 22, 2015, at 3:30 PM, Crispin Pemberton-Pigott 
>>> <crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
>>> Dear Frank the Patient
>>>
>>>
>>> The stoves currently in use are burning everything. The description 
>>> given by John Davies is apt: a box with a chimney.
>>> >The fuels you list are very different so do you have several stoves 
>>> designed to burn each of the different fuels?
>>>
>>>
>>> Well that is the problem: no, there is a single stove. ‎ A possible 
>>> high efficiency option is the use of inserts optimised for each 
>>> fuel, but they are often burned together. For example people often 
>>> mix dung and wood. Some efforts have been made to find 'more 
>>> efficient' stoves which usually means extracting more heat without 
>>> improving the combustion efficiency. I will check.
>>>
>>>
>>> >The fuels need to be prepared as they are likely going to be on site 
>>> regarding moisture and size, densified (pellets or pressed into 
>>> cylinders), split, ground etc. Any process that is likely to take 
>>> place at the location in prep for the combustion apparatus.
>>> This is how to do a contextual test in a lab. There is no need to 
>>> drag the lab into the field if you know what they are going to do 
>>> and use.
>>> The stoves are designed to heat and cook. And bake I think, at least 
>>> some of them. The major issue I see is they are all similar to the 
>>> Mongolian baseline stoves, which is to say, copies of a Russian 
>>> portable wood stove.
>>> >Only the stoves that can actually use the fuel and expect to do a good 
>>> job for the task intended.
>>>
>>>
>>> But we already know they are going to use all those fuels. Now what?
>>> Regards
>>> Crispin
>>>
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