Hexamine cubes
- burn smokelessly, do not liquefy while burning and leave no ashes
- As with trioxane, hexamine has an almost infinite shelf life if stored properly, in a sealed dry container.
- have a high energy density - 30.0 MJ/kg (so ultra-lightweight)
- used for cooking by campers, often with disposable metal stoves
Cooking
- heat given off cannot be easily adjusted - cooking requiring simmering is more difficult.
- The burning tablets are sensitive to wind, so a simple windscreen should be used. Eg. a cup.
- 45 min using 10-15min tablets sequentially to cook rice (faster if rice is presoaked for 2 hours).
Safety
- Not to be ingested
- combustion can create formaldehyde, ammonia, nitrogen oxide, hydrogen cyanide. So good ventilation needed.
Denatured alcohol
- Very simple. Can DUI.
- Easy to find compatible fuels.
- Very inefficient.
- Sensitive to the wind.
Dangers
- Spillage - can start forest file. Banned in CA.
- Can produce toxic fumes (can have additives).
Coal, Charcoal
Firing/ starting
- Use 2kW heat gun - for firing charcoals in 2 minutes. (3600 for made in india with rAghavendra in 2021).
- Make lumps contact flame for about 5 minutes. Usually coal stoves have a bottom vent to place/ air the initial fuel. Common initial fuel -
- oiled cotton
- Paper towel made to soak oil for 2 minutes. YT.
- Hexamine cubes (aka ಒಲೆ ಕರ್ಪೂರ, flame-o tablets)
Comparison
- Due to the high energy density, lump charcoal burns a lot cleaner with less smoke and much hotter than wood chunks.
- Lump is charcoal in its truest form. Burns hotter and cleaner than briquettes.
- Due to the irregularity in shape and size of lump charcoal, it’s quite often that it will not fully carbonize when it is made. You will often be able to see bits of pieces that still have some resemblance to the wood.
- Briquettes, on the other hand, are made of sawdust, leftover wood and anthracite coal powder. Binders and additives are added. Then they undergo pyrolysis like lump charcoal.
- briquettes are very consistent in size and burn slower too. That also makes them a more affordable fuel source than lumps.
- some types of coal emanate way more heat than charcoal.
Origin
- Coal is a natural mineral that forms over the span of millions of years while charcoal is a manufactured product created from wood.
- Dead plants and algae got buried under the layers of mud, unable to biodegrade or oxidise. The low oxygen environment causes anaerobic bacteria to start decomposing the matter, and converting it into peat.
- Deeply buried (we’re talking at least 4 km of depth) the layer of peat eventually starts to transform into lignite, which is the coal of the lowest quality. As this process continues and pressure and temperature increase, higher quality coals form.
- Charcoal is carbon that is left after water and other volatile compounds are burnt off from wood (or any combustible biomass) in a low oxygen environment. This process known as pyrolysis is usually done in silos or specialised charcoal kiln and can take days to complete.
- There is deforestation risk.
- This process results in a much more energy dense fuel, charcoal, that is around a quarter of original weight.