Air vs. Steam Atomization Part 7 – Economics (Stack Losses)

Posted on September 14th, 2017 by David W. Spitzer, P.E. in Chemical Manufacturing Excellence

Previous posts discussed incineration and atomization. Atomizing with air instead of steam effectively relocates some combustion air to the liquid waste nozzles and eliminates the need for atomization steam. This occurs because the stack oxygen trim control will reduce the amount of combustion air by approximately the amount of atomization air.

Given that the atomizing steam temperature is 450 °F, the atomizing steam flow is 4200 lb/hr and the stack temperature is 350 °F, the stack heat loss associated with the atomizing steam can be calculated as 4200 lb/hr * 0.50 BTU / lb °F * (450 – 350), or approximately 0.21 x 10⁶ BTU/hr. This may not seem like much but operating all year, where fuel costs USD 5.00 per 10⁶ BTU, produces stack losses of approximately USD 9200 annually (0.21 x 10⁶ BTU/hr * 8760 hours/yr * USD 5.00 / 10⁶ BTU).

Note that there are also stack losses associated with atomizing air. It might seem that these losses should be subtracted from the stack losses associated with steam to calculate the net stack loss. This would not be correct in this application, because the stack oxygen trim control will reduce the combustion air flow by a like amount to account for the increase in oxygen available in the spray nozzles. Therefore, the amount of combustion air plus atomization air entering the incinerator is approximately the same for both air and steam atomization.

Further, the relocation of combustion air to the nozzles eliminates the volume associated with 4200 lb/hr of steam and reduces the flow through the incinerator, which provides an increased capacity to destroy liquid waste. The amount of capacity increase is dependent upon the relative sizes of the burner, incinerator and the amount of steam displaced (among other factors).

See previous posts:

• Air vs. Steam Atomization Part 1 – Sustainability
• Air vs. Steam Atomization Part 2 – The Incineration Process
• Air vs. Steam Atomization Part 3 – The Atomization Process
• Air vs. Steam Atomization Part 4 – Atomization Reliability
• Air vs. Steam Atomization Part 5 – Compressor Capacity
• Air vs. Steam Atomization Part 6 – Economics

 

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All opinions shared in this post are the author’s own.

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David W. Spitzer, P.E.
Principal at Spitzer and Boyes, LLC

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