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Regulatory Information

Stop 03: Heat Exchangers

Highlighted Topic:  Characterizing an Air Emissions Source

Tour Stop 03

The main law governing air emissions is the Clean Air Act (CAA).   The next tour stop covering Vents & Flares (Stack Emissions) provides a general introduction to the main provisions of the CAA.  This stop on the tour will use a heat exchanger to illustrate how to methodically characterize a piece of equipment or unit in order to identify potential air emissions sources.

At first glance, a heat exchanger might not seem to be an important air emissions source, since under normal operations there is no contamination between the heat exchange fluid and the process fluid, and the major purpose of the unit is simply to reduce process fluid temperatures.  However, there is always the chance that leaks or corrosion will occur, causing either cross-contamination of the fluids or releases to the atmosphere.  In addition, any potential venting of the heat exchange gases (e.g., to control pressure) may also release air pollutants.  Finally, even non-process oriented activities, such as blowdown of heat exchange water to minimize corrosion, can represent a source of air emissions.

In order to best evaluate the types of air regulations that might apply to a given unit operation, it is important to first step through all the various regular processes or potential events that might occur with that unit.  For a heat exchanger, this list would include:

Regular Processes:

  • startup
  • operation
  • venting
  • blowdown activities
  • equipment cleanout
  • maintenance
  • shutdown

Potential events:

  • leaks
  • failures/malfunctions

After the list of events is identified, it is then important to consider the possible materials and chemicals that would be involved in those events.  Depending on the specific process fluid and heat exchange fluid being used, each of these actual or potential events may represent a source of air emissions, either because there is specific "venting" involved; or due to general "fugitive" vapor release, etc.   Note that even "potential" events are specifically considered under the Clean Air Act.  For example, there are certain regulations covering controlling equipment leaks (e.g., equipment containing certain hazardous organic compounds).

With a comprehensive idea of the types of regular and potential events that might affect a unit operation, you will be better able to characterize you air emissions sources and meet regulatory requirements.

Other Regulatory Issues:

A unit's list of regular or potential events can also be used to evaluate the potential for generating hazardous waste (managed under RCRA) and wastewater (managed under the Clean Water Act).