Heating – Processes of heating or heater operation – Controlling flame position or work atmosphere
Patent
1996-02-09
1998-06-30
Doerrler, William
Heating
Processes of heating or heater operation
Controlling flame position or work atmosphere
432200, 148634, F27B 904, F27D 700
Patent
active
057724288
ABSTRACT:
A closed-loop control system controls introduction of either water or hydrogen into a furnace region where a part is subjected to an elevated temperature to accomplish a heat treatment process. The heat treatment process causes the part to participate in reduction and/or oxidation reactions which remain in balance at the elevated temperature so long as a hydrogen/water ratio set point is maintained. The system includes an oxygen probe in communication with the furnace region for providing (i) an oxygen output indicative of sensed oxygen concentration within furnace region, and (ii) a temperature output indicative of temperature therein. A controller determines from the oxygen output and temperature output, a measured ratio of hydrogen to water within the furnace region and compares the measured ratio with the hydrogen/water ratio set point, and provides a correction signal output in accordance with a determined difference between the measured ratio and the ratio set point. A flow controller is responsive to the correction signal output to provide a flow of at least one of hydrogen and water to the furnace region to move the hydrogen/water ratio towards said ratio set point.
REFERENCES:
patent: 5211820 (1993-05-01), Poor et al.
Armson, F.J.; Barnett, J.H.; Davies, D.W.L. "Electrochemical Sensors for Heat Treatment Atmosphere Monitoring"; Met -Slag-Gas React. Processes,
Sastri P. and Abraham K.P., "Atmosphere Control in Heat Treatment Furnaces Using Oxygen Probes", Tool And Alloy Steels, Apr.-May 1986, pp. 155-162.
Chen Y.C., "Automatic Control of Carbon Potential in Furnace Atmospheres Without Adding Enriched Gas", Metallurgical Transactions B, 24B, Oct. 1993, pp. 881-888.
Weissohn, K.H. "Sauerstoffmesszellen zum Regeln von Ofenatmospharen" Gaswarme International, 32, 436-437, 1983.
Weissohn, K.H., "Oxygen Partial Pressure Measurements With a Zirconium Oxide Probe", Gas Warme International, 29, 331-342, 1980.
Van Den Sype Jaak Stefaan
Vankempema Richard Bruce
Doerrler William
Lau Bernard
Praxair Technology Inc.
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