Is it more energy-efficient to use unfiltered air?
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In a certain catalytic unit equipped with a waste heat boiler that includes a make-up combustion section, the make-up combustion system was not activated because the temperature of the superheated steam was sufficient. However, to prevent backflow of flue gases from causing corrosion of the blower and related pipelines in the make-up combustion system, the blower operated at a low load (with an outlet pressure of around ten thousand pascals). 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 electricity consumption and maintenance costs of the blower, making it more energy-efficient; this solution was even submitted as a measure to reduce energy consumption, and promotional materials for it were published on a certain website.
It’s possible to calculate this: measure the power consumption when the blower is running at low speed, then determine the flow rate when unfiltered air is fed through it. By comparing the costs of the two, an answer can be obtained
Well, this can be calculated through data, and energy consumption can also be calculated
Whether it’s mass flow rate or volume flow rate, it’s the same; using unfiltered air would likely 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, right?
Obviously, unpurified air is more energy-efficient. The cost associated with using unpurified air is only a few cents per cubic meter; no supplementary combustion is required, and the air is used for sealing purposes in small quantities – a flow rate of 0.1 m/s is sufficient. For an operating industrial fan, increasing the air volume by 100 cubic meters requires raising the pressure to 0.6 MPa; however, the current does not increase significantly. But when the make-up air fan is operated alone, the no-load current is quite high. I feel that the person who came up with this suggestion is thoughtful and deserves encouragement.