Optimizing Heat Exhaust Capture for Natural Gas Fired Industrial Heaters

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Discussion Overview

The discussion revolves around the feasibility of capturing and storing heated air exhaust from a natural gas fired industrial heater dryer, specifically focusing on the potential for compressed storage and subsequent filtration of pollutants such as NOx and VOCs. The scope includes theoretical calculations for compression ratios and tank volume requirements, as well as practical considerations for air filtration systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the practicality of capturing 24 hours' worth of heated air exhaust, suggesting that storing such a volume in a single tank may not be feasible and could be inefficient.
  • Another participant proposes that the goal may be to capture and utilize the energy from the exhaust, mentioning the possibility of using a Brayton cycle for energy recovery.
  • A participant clarifies that their ultimate goal is to filter the air to remove pollutants, but expresses concern that the filtration system cannot handle the high flow rate of 70,000 CFM.
  • Suggestions are made to either upgrade the filtering system to match the flow rate or to explore additives or secondary processes to reduce NOx emissions.
  • Concerns are raised about the source of pollutants, with one participant indicating that the presence of pollutants might suggest issues with the gas burners or the quality of the gas being used.
  • It is noted that the combustion process itself generates NOx emissions, emphasizing the discussion's focus on environmental pollution control rather than decontamination of the drying process.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of capturing and storing exhaust air, with no consensus on the best approach to address the filtration of pollutants or the efficiency of current systems.

Contextual Notes

Participants highlight limitations related to the capacity of filtration systems, the efficiency of energy capture methods, and the implications of gas quality on emissions. The discussion remains open regarding the best methods for managing exhaust and pollutants.

Jake Platt
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Given a natural gas fired industrial heater dryer which gives off 70,000 CFM of 190F air at 1.1 atm air pressure, is it practicably possible to capture 24 hours worth of this heated air exhaust into a compressed storage tank?

How would I calculate the theoretical maximum compression ratios and tank volume requirements?
 
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Jake Platt said:
Given a natural gas fired industrial heater dryer which gives off 70,000 CFM of 190F air at 1.1 atm air pressure, is it practicably possible to capture 24 hours worth of this heated air exhaust into a compressed storage tank?

How would I calculate the theoretical maximum compression ratios and tank volume requirements?

There's no way you could store that kind of volume in a single tank, and doing so would be a losing proposition anyway. http://www.wolframalpha.com/input/?i=70000+cfm+*+24+hours".

I'm getting the feeling you're actually interested in capturing/utilizing/storing the energy in the exhaust from the dryer, which could possibly be done with some sort of http://en.wikipedia.org/wiki/Brayton_cycle" , which assuming atmospheric temperature is 75 F will be 17.5% (but if it's "free" energy, who cares? Run a generator and pipe that energy back into the dryer...)
 
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Thank you. Actually, our goal is ultimately to filter the air to remove suspended Nox or VOC particulate matter but the air filtration system cannot handle 70,000 CFM so we were considering compressing and storing the air so we can filter it later at a metered, controlled rate. But alas, it seems that won't work either. Any ideas??
 
Get a filtering system that can keep up with the flow rate, or look into additives or secondary processes that reduce NOx?
 
If you are getting enough pollutants to need filtering, that suggests there is something wrong with your gas burners, or you are using low quality gas.

In any case, the pollutants have presumably already contaminated whatever you are drying before you would filter them from the exhaust.
 
The natural gas combustion is what creates the NOx. We are talking about environmental pollution control not decontamination of a polluted process. The process starts with clean agricultural commodities at 80% moisture and ends with the commodities at 10% moisture and voluminous quantities of heat exhaust from the natgas combustion that has suspended VOC's and NOx emmissions.
 

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