[Stoves] Coal dust briquetting

[Andrew Heggie]

On Sun, 10 Mar 2019 at 21:53, alex english <aenglish444 at gmail.com> wrote:
>
>
> Here is an interesting document about spontaneous biomass heating.
> http://www.mdpi.com/1996-1073/8/6/5143/pdf


That was thorough, I think I understood most of it.

It includes the fact that  initial heating (and production of
moisture), up to 70C can happen with microbes and then oxidation of
fatty acid esters can raise the temperature to the auoignition point.
There have been a number of cited incidents where rags soaked in
linseed oil and turpentine have spontaneously ignited as the heat
builds up from oxidation of the oil.

As Daniel says it has long been a practice to load cold frames with
dung and straw to provide heat and we had a hotel in Devon that
utilised the heat from decomposition of woodchip  by running alkathene
pipes through it.

I was going to comment about a  discussion I had with Tom Reed years
ago, he was intending to write a paper on the way "will-O-the-wisp"
occurred. This is the ethereal blue flame that is said to occur above
marshes. Sure enough I have experienced an ignitable gas rising (a
mixture of methane and carbon dioxide) in bubbles above water but I
have never seen it self igniting. Tom had a theory and it is similar
to what I today received from Frans.



On Mon, 11 Mar 2019 at 23:48, peeters frans <peetersfrans at telenet.be> wrote:
>
>     Flames rising from GRAVES …..Is ignition of H3P Phosphin in air ; not the spirit leaving the body .
>


As well as phosphine Tom was suggesting the same could happen with
silane,  though I'm not sure that occurs naturally.

The thing is whilst phosphine and silane ignite on contact with air
and may thence ignite the methane, methane  only burns in a small
range of air ratios IF premixed.

Many years ago, Alex, you pointed out that  a diffuse flame at some
point always has the right air to fuel ratio to allow ignition, so at
the bounday of the bubble bursting in air conditions would be right
somewhere if an ignition source is present.

Andrew