To provide an effective and integrated process in which various operations of the process are integrated thermally and oppressively, and the need is eliminated of an independent oxigen producer or an oxygen supply system.

A material entraining gas flow 1 containing an oxygen element becomes a mateal entraining gas flow 3 pressurized in a lower 2 and is heated in a heat exchanger 33 to produce a hot material entraining gas flow 4. A material entraining gas flow 5 is heated in a heater 34 into a material entraining gas stream 6, and then enters a supply side of an ion conductive module 35 using an ion conductive film 7. Part of oxygen in the high temperature mateal entraining gas flow 6 is removed in an ion conductive module 35, and a gas flow 8 emanating the ion conductive module 35 is enriched with nitrogen with respect to the material entraining gas stream 1. A transmission side 7b of the ion conductive film 7 is purged with a purge gas flow 9 containing combustion products.