Would be pretty cool for interop to be able to burn liquefacted coal and blazing pyrotheum in the liquid-fueled boiler. I'm not sure what the exact 'burn times' are supposed to be for them, though, but here are the defaults for how much RF they provide, with charcoal, coal, and lava also included for comparison:

charcoal=32000
coal=48000
lava=180000

-- new fluid names --
coal=1000000
pyrotheum=2000000

Did a bit of checking.

Each bucket of liquefacted coal, or coal in the dict, is worth 20.833 coal. Each bucket requires 10 coal to create, so it's just over twice the energy of coal on a per-unit basis.

Blazing pyrotheum, or pyrotheum in the dict, is twice the energy, per bucket, as liquefacted coal. So roughly 41.666 coal.

Can someone point me at a description of these fluid: ie how they are made/acquired?

And could you define "in the dict"?

Ok, based on the RF produced by Fuel in the Compression Dynamo, I came up with a 2/3 ratio for coal/fuel. In a boiler, Fuel produces 48000 HU, therefore Liquid Coal will produce 32000 HU. From there, Pyrotheum is twice that value, so 64000 HU.

ok, done.