It turned out in elsewhere, that you cannot necessarily use fire and CO2 in the furnace. Instead of CO2 you should use nitrogen as filler gas. In order to get neutral gas into furnace, you need two stage process.

In the first stage you burn oxygen from the air just like before. 
In the second stage you simply collect CO₂ and H₂O from the created exhaust gases. Unlike oxygen, it is kids play to remove both H₂O vapors and CO₂ from the exhaust gas. 

Produced water vapors can liquidized with low temperature. CO₂ can be separated by dropping it to the bottom, possibly collecting it from the gas. Drop needs, that you disturb the mesh, so that CO₂ molecules have a chance to fall onto floor. You need some kind of slow paddling system for doing the drop-out.

The produced, cheap, 100% fireproof, neutralized gas has obviously quite a lot of use.

CO2 furnace begins with load area. At load area you fill cars with things you want to liquidize and vaporize.
From load area you push the cars into Hall. In hall you clean air from oxygen. Air can be cleaned from oxygen with fire.
From Hall you take the loaded car into actual CO2 furnace. You warm CO2 furnace with electric resistor.
In furnace you collect liquids. You lead gases through cooler into gas distiller.

Furnace needs always a unit for the creation of oxygen free air.

When you play with metals you need electric resistor. Metals melting and vaporizing temperatures are so high.
Since metal furnace needs lots of electric energy, big furnace needs electric power production system.
When you use fire / combustion engine for creating the energy, you required CO2 from the power system.

With wood, food and others you can use copper heart, which is warmed with fire / electricity.