Another stove run

Fired up the stove again a couple of nights ago. Made some tasty, tasty jaffles on it. Mmmm, jaffles.

It took quite some time to melt the cheese, so it's not putting out a great amount of heat. However the main point of this run was to see what happens when the stove is left alone after the burn - in the previous burn I put the char into a sealed container to prevent it from burning. Turns out the char does keep burning as I expected - the next day there was just a tiny bit of char and ash left in the stove.

So I need some way of stopping the combustion ... I guess either cooling it down, or stopping the oxygen getting in. I prefer to not to quench it if possible (makes a bit of a mess), so maybe a sealed lid and some sort of ring to block the holes in the outer tin?

EverythingNice stove Mk II

So the initial burn of my EverythingNice stove went pretty well but it can still be improved. The main issue with it was the "cone" of uncharred fuel left in the bottom after the burn. From my (admittedly not perfect) understanding of TLODs¹, this shape makes sense due to the direction of flow of the hot gasses in the inner chamber.

My simple solution (I don't claim to have come up with the idea, others have done this before me) was to insert a cone-shaped piece of metal into the bottom to prevent any fuel from sitting where it wouldn't be burnt. The cone was made from the bottom of a tin of tomatoes (approx same diameter as the outer tin).

Circular piece of metal cut along a radius, and two holes drilled near the cut

The cone shape formed and secured with a bolt

The edges were snipped a bit so I could bend it to fit nicely inside the tin, and then it was simply placed at the bottom. I didn't really feel like watching it for an hour this time so I only filled it up maybe just over 1/2 way with 100g of pellets for the burn. I lit it the same way as before, soaking a couple of pellets in alcohol for a couple of minutes, putting them on top and lighting them.

Also played around with putting cans on top to try to increase the draw. Seemed to give a slightly stronger flame, but not much.

The results:

• Seemed to take a little longer to achieve a nice consistent flame cap. Not sure if this was the cone in the bottom, or because I only filled it halfway up. (What's that about only changing one variable at a time?)
• Once it was going, had a nice steady flame as before.
• The 100g of fuel burnt for ~32mins and produced 19g of nice biochar. (Okay, I couldn't resist throwing a couple of seeds and leaves in there to see what would happen, so I guess slightly over 100g of fuel)
• When the flame died down and went out, it smoked a little for maybe 5-10 seconds, but that was it.
• After it had stopped smoking I looked into the chamber and noticed that a little of the char was glowing red. Taking this as a sign that the charcoal was now combusting (which I didn't want, I wanted to keep it), I poured it out into a metal tin and put the lid on to deprive it of oxygen.
• After it had cooled down, the char left behind was much nicer than before. All fully pyrolised.

All fuel fully pyrolised. Yay!

So, in the end, very happy with Mk II of my EverythingNice stove at the moment. I'll do some water boil tests to get some idea of the heat output in the near future.

[1] : TLOD (Top-Lit Opposing Draft), the mechanism by which the EverythingNice and Lucia stoves (invented by Nat Mulcahy of Worldstove) operate. A lot of people out there claim that they are TLUDs, but they are a different beast altogether. I'll post about the differences and the airflow in TLODs in a future post.

EverythingNice stove build

I've been playing with home made gasifier stoves for a little while now. I'd watch some youtube videos of other people's stoves, find some tin cans, drill some holes and fill it with some biomass that was lying around. The results were never great, they would usually burn for a little while and then go out and give out lots of smoke. Using different quality fuel each time also made it really hard to tell how changes I had made to the stoves affected them.

So I decided to get some proper fuel and make a proper version of the EverythingNice stove from Worldstove (plans are here).

First thing was to find some suitable tins. I needed the two diameters to be within 8-10mm of each other, and the smaller tin to be 8-10mm shorter. After exploring the aisles of the local supermarket for some time, I ended up with a tin of Lindt drinking chocolate (with a nice lid) and a standard baked-beans can. Following the instructions I drilled a series of 12mm holes around the base of the Lindt tin, and then cut a 37mm hole out of the centre of the lid with tinsnips :

Lindt chocolate tin

The inner tin got as many 4mm holes as I could, centred on a line 18mm from the bottom of the tin.

Old baked beans can

 Each tin had a 3mm hole drilled in the bottom at the centre, so a M3 bolt could be used to keep the two tins centred.

Holes drilled for centring tins

Centred using one M3 bolt

Turns out finding wood pellets in Sydney isn't as easy as I thought. There are places that sell them, but they seem to want to sell by the pallet load. I found this product called Oz-Pet Cat & Pet Litter which are just wood pellets, but sold as kitty litter. Got a 10kg bag for ~ $14 from a local pet store.

Fuel pellets masquerading as kitty litter

Now for the fun part. I filled the inner tin up to the "fill line" (18mm from the top) with pellets. I soaked a couple of wood pellets in some metho for about 5 mins. Then I dropped them on top and lit them using my girlfriend's creme brulee torch (sshhh).

Here's what happened:

• Stove lit nicely with a blue flame (due to the alcohol). Began gasifying within around 2 mins
• Burned with a fairly strong orange flame for ~55mins
• Produced virtually no smoke (until the end ...)
• After around 55mins, the flame died down and a little smoke started to be produced
• After the flame went out, it made lots and lots of smoke. I mean lots. I assume this would have gone on for a while, but I poured a bucket of water over it. That stopped it smoking.

In this photo you can see the flame ...

... and in this one you can see the tin. Use your imagination to combine the two.

 After everything had cooled down a bit I had a look at what was left of the wood pellets. On top they were very nicely pyrolised, but as I dug further down it turned out there was a cone-shaped region of unburnt pellets at the bottom. This would have been what was causing all the smoke at the end. Here's what was left:

The aftermath.

Note that the unburnt pellets have swollen up quite a bit from the water, they would have been the same size as the charred ones.

So, all in all, I was quite happy with the stove, especially for a first (proper) attempt. It burnt really well while it was alight, just need to get it to char all the fuel, and to not smoke so much once it's done.

Intro

A blog to keep track of projects I do and stuff I get up to. Mainly so that I can remember what I've done if I need to do it again, but if others happen to stumble across it then all the better.