Air-Gas Ratio Control Applied to Nonatmospheric-Pressure Furnaces

For reasons of economy and efficiency, in the burning of fuel gases in industrial furnaces it is essential to maintain the air-gas ratio at approximately the correct point for perfect combustion. Furthermore it is important to control the ratio of air flow to gas flow because of the effect of burned gases or atmosphere upon material being heat-treated. The author discusses in detail the various control processes available, the equipment developed for the purpose, and analyzes the several control circuits, basing the work on the laws of low-pressure gas flow or noncompressible flow.