Is it more energy-efficient to use unpurified air in refineries rather than low-pressure compressed air from blowers?

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In a certain catalytic unit equipped with a waste heat boiler that includes a afterburning section, since the temperature of the superheated steam was sufficient, the afterburning system was not activated. However, to prevent backflow of flue gases from causing corrosion of the blower and related pipelines in the afterburning system, the blower operated at a low load (with an outlet pressure of around ten kilopascals). It was proposed to connect a non-purified air pipeline at the blower outlet, using such non-purified air (with a normal pressure of around 0.6 MPa) to prevent backflow of flue gas. It was claimed that this approach saved on the blower’s electricity consumption and maintenance costs, making it more energy-efficient; this solution was even submitted as a measure to reduce energy use, and promotional materials for it were published on a certain website. PS: Personally, I think it makes no difference whether it is mass flow rate or volume flow rate; using unpurified air would result in higher energy consumption. The energy required to compress air to 0.6 MPa must be much higher than that needed to compress it to tens of kilopascals. Some people on the forum said that using unfiltered air is more energy-efficient – what do you all think?