Effect of H2O content in air on the carburizing behavior of charcoal gas

Abstract

Conventionally, charcoal gas is produced by reacting air with hot charcoal. The constituents of such charcoal gas are N2, CO, and CO2. Because no H2 exists in this kind of charcoal gas, its carburizing rate to steels is relatively slow, compared with atmospheres containing CO and H2. A simple, but effective, method to raise the carburizing rate of the charcoal gas has been found through this study; that is, the air used for generating charcoal gas is humidified with some water vapor before passing through the hot charcoal layer. In this way, the carbon potential and carburizing rate of the charcoal gas can be raised markedly due to the formation of H2. For example, when the air is humidified with 7.30% H2O, the carbon potential increases by about three times, and the carburizing rate increases by about four times, compared with the charcoal gas generated from dried air and charcoal.