[Stoves] How to make smokeless coal?

Nikhil Desai pienergy2008 at gmail.com
Mon May 22 13:40:29 CDT 2017


Darpan:

Sorry, that post was sent prematurely from my naughty "smart" phone.

To complete :

So the answer is "more complete combustion" - ménage a trois of carbon,
hydrogen and oxygen?

You say complete combustion is impossible: "This can never be the case for
uncontrolled combustion devices like stoves."

Whoever gave you the thought that cooking is an "uncontrolled combustion"
operation? Some mythology of 3-stone fires? How many people have observed
these "uncontrolled" combustion processes? Any who did, and not just for
photo opportunity at the time of thrusting in measuring equipment in a few
households a few minutes or hours at a time, would know that cooking is a
dance of shuffling fuel, pots, ingredients, along with many other
concurrent activities, that together amounts to poor people's "control".

"Uncontrolled combustion" is a physicist's fancy way of admitting
ignorance.

I happen to remember from some Government of India reports in the 1970s and
some research papers by Ramesh Bhatia in the 1980s that coke was used as a
household cooking and heating fuel (then Bihar, now Jharkhand and Bihar).
Have you checked the state of Indian coke plants these days? I suspect a
lot of new plants have come up in the last 20-odd years.

Maybe "low smoke" coal is already in the market but picked up by commercial
customers.

If you are really worried about pollution from coal use in India, I venture
a guess that such commercial customers' direct use of coals is likely more
polluting in terms of resultant exposures than the household use by those
you call "slum dwellers".

Brick kilns. Small foundries. Often combined with Holy Renewable Energy,
namely Biomass (crop and mill residues).

Which is why I wondered why smokeless dung and smokeless wood oughtn't be
pursued as well.

Could it be that poor households wouldn't bother researchers and commercial
users couldn't be bothered by them?

Nikhil



------------------------------------------------------------------------
Nikhil Desai
(India +91) 909 995 2080
*Skype: nikhildesai888*


On Mon, May 22, 2017 at 1:18 PM, Nikhil Desai <pienergy2008 at gmail.com>
wrote:

> Darpan:
>
> So the answer is "more complete combustion" - ménage a trois of carbon,
> hydro1
>
> Nikhil Desai
> +91 909 995 2080 <+91%2090999%2052080>
> Skype: nikhildesai888
>
> On May 22, 2017, at 10:52 AM, Darpan Das <darpandasiitb at gmail.com> wrote:
>
> Dear Mr Andrew
>
> Thanks for your answers. Some comments:
>
> I asked: If I remove the volatiles then will the emissions reduce?
> You said: Perhaps but you will still have to burn the smokeless coal
> completely. What will you do with the volatiles you have removed?
> My reply: I do not understand what you mean by 'burn the smokeless coal
> completely'. Burning a fuel completely is achieved when they are provided
> with a stochiometric amount of oxygen to produce completely oxidised
> product of CO2 and H2O. This can never be the case for uncontrolled
> combustion devices like stoves.
> Further, I agree the process of carbonisation involves the removal of
> volatiles at a certain temperature. These volatiles, when removed have
> certain calorific value and usually when emitted from coke oven batteries
> are collected as 'tar' as can be used for commercial application.
>
> I asked: How do I decide at what temperature should I carbonise?
> You said: The higher the temperature then nearer the coal will get to be
> coke.
> My reply: So ideally you mean the temperature with infinite value is the
> one where coal would get converted to coke.Coking plants would try to
> reduce their cost by reducing the temperature at which to carbonise. This
> is basically that temperature, where most of the volatiles get removed.
> Will it not vary from coal to coal, size to size? How can I optimise this
> temperature?
>
>
> I asked: Why is low temperature carbonisation of coal meant for domestic
> use and high temperature for metallurgical use?
> You Said: The reason coke is made at a high temperature is so that it is
> nearly pure carbon, domestic smokeless coal just needs the more volatile substances
> removed but leaving higher tars in the coal to retain more of the initial
> energy in the coal plus make it easier to light.
> My reply: Usually literature report of 600 C for domestic coke and
> 800-1000 C for metallurgical coke. Why this distinction? Why can they be
> interchangeably used?  You said 'domestic smokeless coal just needs the
> more volatile substances removed but leaving higher tars in the coal to
> retain more of the initial energy in the coal plus make it easier to
> light'. So does this mean by heating the coal at lower temperature for
> domestic application the low molecular weight volatiles are removed,and tar
> with high molecular weight remain which provide enough calorific value to
> the fuel to make it a easy fuel to light. If this theory to be hold true -
> they why metallurgical coke are heated at higher temperature? We would want
> the same thing there too.
>
> Regards
> Darpan
>
> On Mon, May 22, 2017 at 3:13 AM, Andrew Heggie <aj.heggie at gmail.com>
> wrote:
>
>> On 20 May 2017 at 19:33, Darpan Das <darpandasiitb at gmail.com> wrote:
>>
>> >
>> > 1) Is carbonisation of coal the major step to make it a smokeless fuel
>>
>> I'm no expert but my take is yes and more below.
>> >
>> >
>> > 2) Is pyrolysis/carbonisation/ devolatalisation the same thing?
>>
>> Yes
>> >
>> >
>> > 3) Are volatiles the main reason for emissions from coal cook stoves?
>>
>> Not being able to completely burn these volatiles in the time the
>> molecules remain in the flame leads to Particles of Incomplete
>> Combustion leaving the flame, these are a mixture of soot and
>> Polycyclic Aromatic Compounds.
>> >
>> >
>> > 4) How can i remove the volatiles?
>>
>> By heating up the coal in the absence of air
>> >
>> >
>> > 5) If I remove them then all the emissions will reduce?
>>
>> Perhaps but you will still have to burn the smokeless coal completely.
>> What will you do with the volatiles you have removed?
>> >
>> >
>> > 6) How do I decide at what temperature should I carbonise?
>>
>> The higher the temperature then nearer the coal will get to be coke.
>> >
>> >
>> > 7) Why is low temperature carbonisation of coal meant for domestic use
>> and
>> > high temperature for metallurgical use?
>>
>> What do you mean by low temperature?
>>
>> The reason coke is made at a high temperature is so that it is nearly
>> pure carbon, domestic smokeless coal just needs the more volatile
>> substances removed but leaving higher tars in the coal to retain more
>> of the initial energy in the coal plus make it easier to light.
>> >
>> >
>> > 8) Is the size of the coal not important factor to be taken into
>> > consideration when carbonising the coal?
>>
>> I don't know
>> >
>> >
>> > 9) Why is coke for domestic purpose also called semi-coke?
>>
>> Because it is only part way to being coke as the pyrolysis is at a
>> lower temperature (typically 650centigrade rahter than 1100c when
>> making producer gas.
>> >
>> >
>> > 10) Coke obtained from Low temperature Carbonisation same as Semi Coke?
>>
>> Probably
>> >
>> >
>> > 11) What are the specification for quality assurance of the domestic
>> coke
>> > products? Are there any standards?
>>
>> I would think there are bound to be but  I don't know them.
>>
>> There are similariiities between pyrolysis of coal and making charcoal
>> but the by products from coal are nastier.
>>
>> I suspect this is because the coal contains volatiles which are more
>> phenol (ring like carbon structures) like whereas wood has more chain
>> like structures and the lignin, which is phenol like structures are
>> not as complex so can burn out more completely without giving rise to
>> many PAHs, Also coal gives of amoniacal liquids and sulphur compounds.
>>
>> Andrew
>>
>> >
>>
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>
>
> --
> Darpan Das
> Research Scholar
> IIT Bombay
> India
>
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