Integrated Process for Producing Atmospheres Suitable for Heat Treating from Non-Cryogenically Generated Nitrogen

摘要

An integrated two-step process for producing low-cost atmospheressuitable for annealing ferrous and non-ferrous metals and alloys, brazingmetals, sealing glass to metals, and sintering metal and ceramic powders incontinuous furnaces from non-cryogenically produced nitrogen containing upto 3% residual oxygen is disclosed. The residual oxygen present innon-cryogenically produced nitrogen is converted to moisture by mixing ithydrogen and passing the mixture through a reactor packed with a platinumgroup catalyst in the first step of the process. The reactor effluentstream containing a mixture of nitrogen, unreacted hydrogen, and moistureis mixed with a pre-determined amount of a hydrocarbon gas and introducedinto the heating zone of a continuous furnace in the second step of theprocess to 1) convert moisture to a mixture of carbon monoxide and hydrogenby reaction with the hydrocarbon gas via water gas shift reaction and2) produce atmospheres in-situ suitable for heat treating. The key featuresof the process include 1) use of economical amount of hydrogen to convertresidual oxygen to moisture in an external catalytic reactor and 2)conversion of moisture to a mixture of carbon monoxide and hydrogen byreaction with the hydrocarbon gas via water gas shift reaction in the hotzone of a continuous furnace. The disclosed process is particularlysuitable for producing low-cost heat treating atmospheres for continuousfurnaces operated at 700°C and above.