Endothermic Gas

               Endothermic gas generator

Endothermic gas or endo gas is used for the thermal treatment of metals as a protective gas. It can be generated in an

endothermic gas generator by burning natural gas, consisting mainly of methane or other hydrocarbons with heavy lack

of oxygen. The reaction takes place at the surface of a catalyst under external heating at around 1000°C. The process

needs energy supply and is therefore endotherm.

        2 CH₄  +  O₂  →  CO  +  4 H₂
Carbon monoxid and rather high amounts of hydrogen are formed. Nitrogen from the air is of course also available in larger

quantities and can be further increased in order to dilute the hydrogen content. Carbon dioxid, water and unburnt

hydrocarbons are included only in small amounts. Formation of soot can be avoided by selecting proper process conditions.
Hydrogen and carbon monoxide are reducing agents and avoid oxidation or corrosion of metal surfaces in a furnace. It has to

be taken into account however, that carbon monoxid increases the carbon content of steel. Endothermic gas can therefore

be used for surface hardening of steel by carbonisation or carburization. Carbon concentration can be increased up to the

saturation level of austenite in surface close areas (around 1mm deep).