A heat balance is a three-step audit:

• State of play : description of the furnace, natural gas characteristics, air/gas ratio, productivities, consumption, pilot burners, recuperator and thermal measurements;
• Modeling : balance equations, power provided by gas, theoretical stack losses,effective power, total losses, losses due to wall conduction, losses due to smoke radiation, losses due to unwanted air intake and flue exhaust;
• Improvement options : process, pressure strength, heat loss.