Reference Books

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Reference Books

• Air Pollution Control Engineering, International
  Edition 1995 by Noel De Nevers, McGraw-Hill
  Publishers
• Handbook of Air Pollution Control Engineering and
  Technology 1995, by J.C. Mycoch, J.D.Mckenna
  L.Theodore, Lewis Publishers
• Air Pollution Engineering Manual, 1992 by
  A.J.Beronicore W.T.Davis, Air Waste
  Management Association
• Air Quality Management, Environmental Control and
  Public Health-Air, 1993, T237 Units 14-16, Open
  University

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Factors in control equipment selection

• Environmental

1. Equipment location 2. Available space 3.
Ambient conditions 4. Availability of adequate
utilities 5. Maximum allowable emissions 6.
Aesthetic considerations 7. Contribution of air
pollution control system to wastewater and
solid waste 8. Contribution of air pollution
control system to plant noise levels
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Factors in control equipment selection

• Engineering

1. Contaminant characteristics (i.e.physical and
chemical properties, concentration, particulate
shape and size distribution - in the case of
particulate, chemical reactivity, corrosivity,
abrasiveness, toxicity, etc.) 2. Gas Stream
characteristics (i.e.volume flow rate,
temperature, pressure, humidity, composition,
viscosity, density, reactivity, combustibility,
corrosivity, toxicity, etc.)
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Factors in control equipment selection

• Engineering

3. Design and performance characteristics of the
particular control system (i.e.size and weight,
fractional efficiency curves - in the case of
particulate, mass transfer and/or contaminant
destruction capability - in the case of gases or
vapors, pressure drop, reliability and
dependability, turndown capability, power
requirements, utility requirements, temperature
limitations, maintenance requirements,
flexibility with regard to complying with more
stringent air pollution regulations, etc.)
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Factors in control equipment selection

• Economic

1. Capital cost (equipment, installation,
engineering, etc.) 2. Operating cost (utilities,
maintenance, etc.) 3. Expected equipment lifetime
and salvage value
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Generalized Design Review Procedure

• Design reviews for air pollution control
  equipment are performed for a variety of reasons,
  including

1. To anticipate compliance with applicable air
pollution codes 2. To estimate performance of
existing control equipment 3. To evaluate the
feasibility of a proposed equipment
design 4. To assess the effect on control
equipment of process modification
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Pollution prevention and waste minimization for
air pollution control

• Integrated pollution control has a principal
  objective of preventing or minimizing the
  release of substance which are potentially
  harmful or polluting to the environment
• BATNEEC -- Best available technique not
  entailing excessive cost

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Pollution prevention and waste minimization for
air pollution control

• A general approach
• Four key steps for preventing or minimizing
  pollution
• (1) Reformulate the product -- develop a
  non- polluting or less polluting product or
  process, by using different raw materials or
  feedstock.
• (2) Modify the process -- change the process to
  control by-product formation or to incorporate
  non-polluting raw materials.

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Pollution prevention and waste minimization for
air pollution control

• (3) Change the equipment -- make the equipment
  more efficient or allow it to use by- products
  from another process.
• (4) Recover resource -- recycle by-product for
  own use or use by others.

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Examples of waste minimization which alone or in
combination with others can minimize air
pollution include

• (1) Replacing organic solvent-based inks, paints
  and coatings with water-based ones -- reduces
  emissions of volatile organic compounds
• (2) Replacing halogenated compounds with
  non- halogenated -- reduces the impacts on
  stratospheric ozone
• (3) Replacing mercury, cadmium and lead with
  other less toxic substances -- reduces emission
  as particulate matter or as vaporized metal

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Examples of waste minimization which alone or in
combination with others can minimize air
pollution include

• (4) Improving technology to minimize producing
  pollutants from the process stream, or to
  return useful products to the process
• (5) Installing improved process-monitoring
  equipment to make it possible to improve and
  continuously maintain optimum process conditions
  -- this improves all-round efficiency and so
  reduces emission

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Particulate Matter

• PM is airborne solid or liquid material with a
  particle diameter 2x10-10m
• solid material can be classified according to
  size into 3 categories

• 1. Grit
• 2. Dust
• 3. Fume

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Grit

• defined in the Air Pollution Control (Dust and
  Grit Emission) Regulations of 1987 as particles
  of solid matter which are retained in sieve of
  75um nominal aperture in conformity with BS 410
  1986 of British Standards Institution

Dust
means particles of solid matter which will pass
through a sieve of 75mm nominal aperture in
conformity with BS 410 1986
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Fume

• is not defined in the Dust and Grit Emission
  Regulations of Hong Kong, buy is usually regarded
  as solid particulate matter smaller than dust
  i.e.

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By convention, liquid particulate is usually
split into 1. Mist2. Spray

• Mist --- is particulate matter formed by
  condensation of vapor and typically ranges in
  diameter from 0.5 to 5.0 mm
• Spray --- consists of larger particles formed by
  atomization and break up of bulk liquid

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Engineering control of air pollution

• 1. Enclosure - to prevent the exposure of workers
  and control of emission of air pollutants from
  sources by enclosure or containment within a
  confined area
• 2. Negative pressure - air contaminants are not
  allowed to escape by maintaining a negative
  pressure inside the enclosure
• 3. Natural ventilation - increase natural
  ventilation, only suitable for modest heat loads
  and very lowest emissions of less toxic gases and
  vapors

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Engineering control of air pollution

• 4. Dilution ventilation - to admit to a work
  place a sufficient quantity of fresh air to
  dilute the contaminated atmosphere
• 5. Induced dilution ventilation - to extract the
  contaminated air from the premises by force
• 6. Local exhaust system - to draw the air
  contaminants to air exhaust hood
• 7. Relocation - to relocate the emission source
  to an area where the effect of air pollutants is
  minimal

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The various aspects of Dust Control

• A systematic approach to the solution of a dust
  control problem

1. Identification of the exact nature of the
problem 2. Prevention of the dust becoming a
nuisance 3. Containment and capture of the
dust 4. Transfer of the dusty gas or air in a
dust system 5. Gas cooling or conditioning prior
to dust collection 6. Separation of the dust from
the air or gas stream 7. Handling and disposal of
collected dust and/or slurry 8. Air-moving
machine or fan 9. Control and instrumentation 10.
Dispersal of the exhaust gases
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The Control of Particulate Emissions

• 1. Appreciate the main features which should be
  taken into account in the design of hoods and
  ducting for the capture and transport of
  particulate contaminated gases
• 2. Determine the overall collection efficiency
  which is necessary to meet specified requirements
• 3. Determine the overall collection efficiency of
  emission control equipment from a knowledge of
  the grade-efficiency and the particulate size
  distribution

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The Control of Particulate Emissions

• 4. Appreciate the main features of the following
• types of particulate emission control plant

a.) Gravity and inertial separators b.) Cyclones c
.) Wet dedusters and demisters d.) Electrostatic
precipitators e.) Filtration devices
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Dust containment, capture and pre-treatment

• Containment and capture
• 1. Total enclosure - gas tight
• 2. Partial enclosure - this involves the use of a
  booth i.e. a chamber with an operating in one
  face which allows access to the process or work
  area. The booth must be deep enough to prevent
  escape of dust through the open face-entrain
  velocity 0.5(-1) m

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Dust containment, capture and pre-treatment

• 3. A hood as described in Section 5.3 of the User
  Guide. A hood should be designed to obtain
  effective entrainment of airborne dust using the
  minimum volume of air as close as possible to the
  source of the dust. Air flow rate too low an
  estimate can result in inadequate dust control
  and too high an estimate results in an over-sized
  fan, dust collector, dusting etc.

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Bad design
Good design
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Dust containment, capture and pre-treatment