Reduction of CO2 gas emissions and energy consumption in heat treatment furnaces by development and implementation of a hybrid furnace concept.

In the present work, measures to reduce greenhouse gases in metal processing are presented. The focus here is on CO₂ gas emissions produced by heat treaters specifically on two studied processes neutral hardening and carburization.

The concept and development of a hybrid furnace is based on a standard gas protective modular furnace equipped with radiant tubes, where electrical heating elements are added. In a furnace with natural gas as a heating source, the main stages for these processes are identified on the temperature-time plots: For hardening process, the temperature drop, temperature recover, and soaking; this last is replaced by carburizing and diffusion for the carburization process.

Recovering from the dropped temperature requires the largest amount of energy of the whole process while soaking or carburizing requires significantly less energy to maintain the set-point temperature.

When looking at combustion with standard burners the thermal efficiency lays at around 60%. It is visualized as too profitable a possibility in terms of CO₂ and energy reduction, when additional electric heating elements with an efficiency of 90% to 95% in the process are integrated, these would be exclusively used to support the soaking or carburizing stages.