Waste heat recovery has been successfully utilized in energy intensive industries such as steel,glass and brick for 150 years, however few investment casting furnaces have been equipped utilizing this technology. Significant fuel savings are possible in a pre-heat or burnout furnace and can be guaranteed in advance of any investment through calculation. Given the economics and politics of fuel consumption, investment casters will benefit from the application of waste heat recovery for their furnaces.

Advances in casting technology and techniques have resulted in the increased demand for higher quality castings, tighter tolerances, exotic materials and development of rapid prototypes.

Investment casters have met these challenges by increasing the excess oxygen levels in their furnaces to guarantee clean molds and by preheating molds to higher temperatures for flexibility in pouring. These two directions amplify the savings in fuel that will be achieved through the recovery of waste heat which is normally expelled out through the flue gases. A significant portion of the energy expended in a fuel-fired investment casting furnace is used to heat the combustion air to the process temperature. The high oxygen (high excess air) requirement in investment casting furnaces make the application of heat recovery particularly attractive. One method for the recovery of waste heat is through the use of a specialized heat exchanger called a recuperator. A recuperator takes the waste heat and passes the hot gasses over the heat exchanger to preheat the combustion air to the burners. A recuperator is flexible in application and can be provided on a new furnace or may be retrofitted to an existing furnace. An investment casting foundry desiring to preheat molds to 2200°F in a furnace having an oxygen content of 6% could save 45% in fuel by using a recuperated combustion system to preheat the combustion air to 800°F. If that furnace runs 24 hours a day, 7 days a week, 48 weeks per year with an average fuel input of 1.5 Therms of Natural Gas per hour and an average fuel cost of $0.95/Therm, the investment caster could expect to see a savings of $52,318 per year. If the operating conditions are held the same, except the oxygen level is raised to 9% (common in many SLA applications), the fuel savings increase to 77% for a savings of $88,854 per year. Knowing these process variables is all that is required to calculate a fuel savings and the return on investment.