Endothermic
gas generators are used to produce a low cost endothermic gas that is used
in heat processing and treating furnaces and other protective surface
treatments. They are one of the primary types of equipment used for heat
treatment. These generators are specially designed generators which generate
a special type of gas to be used as atmosphere gas during heat treatment.
The endothermic gas thus produced can also be as atmospheric gas for
carburizing metals and other industrial applications.
The process
An endothermic atmosphere is produced by endothermic generators at a low
cost by using any regular fuel gas like natural gas, propane or butane.
The atmosphere is created by mixing a hydrocarbon gas with air. The mixed
gas is passed through a heated steel chamber filled with a catalyst. The
process requires external heat. This heat is provided by electrical heaters
or fuel burning around the chamber. Heating the mixed gas in the presence of
a catalyst makes the gas to break down or crack into several simpler gases,
mainly hydrogen, nitrogen, and carbon monoxide. Under controlled conditions
when the generator heats fuel gas and air, a rich or lean endothermic gas is
produced. This "cracked" gas is then cooled rapidly to prevent
sooting and the formation of carbon dioxide.
Composition of Endothermic Gas
Operating on natural gas, propane, butane or methane, the reaction of air
and fuel on the catalyst produces endothermic gas of the following
composition:
| Property |
Value |
| CO |
28 to 30% |
| H2 |
20 to 25% |
| CO2 |
0.1 to 0.5% |
| N2 |
Balance |
| Dew point |
(-) 5oC |
Principal Components of an Endothermic
Generator
- Heating chamber: The chamber is used to supply heat by
combustion or electric heating.
- One or more cylindrical retorts in the heating chamber: These
retorts are usually vertical with several small, porous ceramic pieces,
infused with nickel as a catalyst for the reaction.
- A cooling heat exchanger: This is used to cool the reaction
products to a temperature that will not let the reaction to proceed
further.
- The control system: The system maintains the reaction
temperature. It also adjusts the gas/air ratio to create the required
dew point.
Applications of Endothermic Gas Generators
- Gas carburizing
- Carbo-nitriding
- Carbon restoration in steel
- Hardening/Annealing
- High temperature brazing
- Sintering of high carbon and alloy powdered compacts
- Reduction of metal oxides
Exothermic
Generator
Endothermic
Generator