[Stoves] Good enough stove?
Frank Shields
franke at cruzio.com
Tue Nov 24 14:07:02 CST 2015
Dear Paul, Stovers,
<see below>
> On Nov 24, 2015, at 4:26 AM, Paul Anderson <psanders at ilstu.edu> wrote:
>
> 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.
What is important here (for me) is coming up with a reasonable accurate energy value for the char (DAF) without additional testing. Higher temperatures would be better. With a TGA any temperature is easy to get so from now on I will try to remember to say 600c. From what I have seen there is little difference.
And what we are doing in the lab to normalize energy from the fuels chosen has nothing to do with what you are doing in real life. Lab does it so all labs will get the same results from all stoves. Once we figure out how to do that you can bring in your stoves for testing and we labs will see what your stove gets.
What I am counting on is that the carbon graphite structure in char produced will have the same energy value as that derived from grass, twigs, manure, bark, wood etc. And that char is made of 90+% carbon on a DAF basis at the higher temperature you suggest (600c).
That total char energy is then split into Solid-C -> CO and CO -> CO2 energy by a percentage. The CO -> CO2 energy I plan to add that to the volatile pyrolyze energy as (possible) energy that can be used for the task. The best designed stove will be able to use as much as that as possible in the secondary. The SolidC -> CO is heating the stove and boiling moisture, keeping the fire going, etc. but not for the secondary flame used for the task.
So we labs gather fuel as close as we can to the fuel used at a real site then normalize (tweak) it based on all the volatile energy (maximum) that can be used to do the task. Is my thinking.
>
> 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.
More testing needed BUT if you look at what Tom Reed did there is little (but some) difference in changing weight. But I am more inclined to require labs certified for stove testing to have a TGA and not concern with testing in the back yard as I once was. So 600c it is as long as I remember to use it.
Whats left in the char is ash. And if a CHN analysis is run on the char to get percent carbon I have found the Oxygen and hydrogen to be very low on samples with low ash. Oxygen is done by difference. The CHN is challenging to get good results. Moisture absorbed upon sitting adds hydrogen and oxygen (weight not accounted for). More testing needs to be done to add to what Tom Reed (love that guy) has done so to get a percent carbon in the char DAF. That so to report the total energy value of the char.
Regards
Frank
>
> Paul
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email: psanders at ilstu.edu <mailto:psanders at ilstu.edu>
> Skype: paultlud Phone: +1-309-452-7072
> Website: www.drtlud.com <http://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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