Hunan industrial kiln benchmark oxygen content is how much

Hunan industrial furnace benchmark oxygen content is 5%. According to the "boiler air pollutant emission standards" (GB13271-2014), oil, gas boiler benchmark oxygen content of 3.5%, but the actual operation is difficult to achieve, Hunan industrial kiln boiler sealing is good, the furnace structure and disturbances are reasonable, can be controlled to 5% or so, it is a more ideal value. Now many boiler plants in order to improve the thermal efficiency of the flue gas oxygen 5% as the benchmark value.