Air Pollution as a Feedback Control Loop

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Air Pollution as a Feedback Control Loop

• Andrew McCarthy

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Introduction

• Air Pollution Feedback Control
• Purpose and Components of Feedback
• Components of Air Pollution Feedback Control,
  with Mercury as a specific example

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Air Pollution Feedback Control

• Air pollution is monitored and managed by a
  feedback control system

4
Air Pollution Feedback Control

• Economic growth has benefits, but with those
  benefits come risks, such as those caused by air
  pollution. As a result, the growth must be
  controlled.

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Purpose of Feedback

• The primary reason for feedback control is to
  measure and compensate for the effect of
  disturbances.

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4 Elements of Feedback

• Sensor
• Reference Input
• Comparator
• Control Mechanism

www.oz.net/coilgun/levitation/feedbackloop.htm
7
Sensor

• The sensor measures the variable that we seek to
  control, also known as the control variable.

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How is pollution sensed?

• Monitoring agencies use EPA approved equipment.
  PM and lead are measured over a 24 hour period,
  whereas gaseous pollutants are measured hourly.
  Collected data is then compared to the Clean Air
  Act standards (NAAQS) for each pollutant.
• In the case of Mercury, U.S. Bureau of Mines data
  is examined for the following categories
  electrical, paint, agricultural chemicals,
  measuring and control instruments, lab use,
  pharmaceutical, dental, chlorine, caustic soda
  manufacturing, and other. This is combined with
  emission data such as 50 for coal, 75 for
  paint, and 30 for electrical, control equipment,
  and lab use.

http//www.epa.gov/region08/air/monitoring/monitor
ing.html
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Reference Input

• This specifies the value the controlled variable
  should have.

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Pollution Reference Value

• The EPA creates Clean Air Act standards (NAAQS)
  for each pollutant.
• For the case of Mercury, the EPA sets standards
  depending upon the use. (ie 50 ppm
  for paint, 50 reduction by chlor-alkali industry
  by 2005, 90 emission reduction by municipal
  waste combustors by 2000, and 95 emission
  reduction by medical waste incinerators)

http//www.epa.gov/region08/air/monitoring/monitor
ing.html http//www.usgs.gov
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Pollution Reference Value

• NAAQS
• Carbon Monoxide (9 ppm, 8 hour)
• PM10 (150ug/cubic meter, 24 hour)
• PM2.5 (65ug/cubic meter, 24 hour)
• Ozone (.08 ppm, 8 hour)
• Sulfur Oxides (.14 ppm, 24 hour)

http//www.epa.gov/air/criteria.html
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Comparator

• Compares the sensed value with the reference
  value. It also specifies the direction in which
  the correction needs to be made.

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Air Pollution Comparator

• The EPA compares the data collected by monitoring
  sites to the Clean Air Act Standard.
• The EPA can, in the case of Mercury, monitor
  certain industries and the products they produce
  to determine if Mercury levels are within their
  guidelines.

http//www.epa.gov/region08/air/monitoring/monitor
ing.html
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Control Mechanism

• Takes the output of the comparator and corrects
  the sensed value in the direction of the
  reference input.

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Air Pollution Control Mechanism

• If pollution levels are above the NAAQS and
  present a risk, the monitoring agency in the
  state must develop and implement a plan to reduce
  the air pollution.
• If mercury levels are too high in a given
  industry, the EPA can levy stiff financial
  penalties, and the industry opens itself to
  litigation.

http//www.epa.gov/region08/air/monitoring/monitor
ing.html
16
Conclusion

• Air Pollution Feedback Control
• Purpose and Components of Feedback
• Components of Air Pollution Feedback Control,
  with Mercury as a specific example

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References

• http//www.oz.net/coilgun/levitation/feedbackloop
  .htm
• http//www.acfr.usyd.edu.au/teaching/3rd-year/mech
  3800-SystemsControl/material/lectures/block20diag
  rams.pdf
• http//www.engin.umich.edu/group/ctm/examples/exam
  ples.html
• http//www.epa.gov/region08/air/monitoring/monitor
  ing.html
• http//www.epa.gov/air/criteria.html
• http//www.usgs.gov