GASCLEANING TECHNOLOGY Chapter 13

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GAS-CLEANING TECHNOLOGYChapter 13

• PETRI SJÖHOLM
• DEREK B. INGHAM
• LEENA PERTTU-ROIHA
• MATTI LEHTIMÄKI
• HOWARD GOODFELLOW
• HEIKKI TORVELA

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Contents of Chapter 13

• GENERAL
• PARTICLE REMOVAL
• Cyclones in Industrial Ventilation
• Electrostatic Precipitators Fundamentals
• Fabric Filters
• Scrubbers Wet Cyclonic, Packed Tower,
  Impingement, and Venturi
• References
• GASEOUS COMPOUNDS
• The Control of Organic Compound Emissions
• References

• FUME CONTROL TECHNOLOGY
• Basic Principles
• Emission Source Characterization
• Fume Capture Design Methodolgy
• References
• EMISSION MEASUREMENT TECHNOLOGY
• Basic Procedures For Emission Measurements
• Particulate Material Emissions
• Gaseous Emissions
• Case Example
• References

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GENERAL

• Gascleaning technology deals with all types
  gases, from air to flue gases and process gases.
• Particle size distribution relating to gas
  cleaning is well understood in the industry. This
  section deals with general rules of thumb.

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TABLE 13.1 The Physical and Chemical Nature of
Particles, from Molecular Level to 10 mm Size.
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FIGURE 13.1 A schematic diagram of a classical
reverse-flow cyclone.
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FIGURE 13.2 A schematic diagram of the
trajectories for two different sizes of particles
in a typical cyclone.
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FIGURE 13.3 Typical collection efficiency curve
of a cyclone.
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FIGURE 13.4 A schematic diagram of the critical
trajectory of a particle of diameter
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FIGURE 13.5 Principle of electrostatic
precipitation.
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FIGURE 13.6 Principle of electrostatic
precipitation utilizing separate charging and
collection sections.
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FIGURE 13.7 Principle of the tubular
electrostatic precipitator.
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FIGURE 13.8 Principles of single-stage and
two-stage electrostatic precipitators.
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Cleaning Cleaning method The physical principle
used to dislodge and remove the collected dust
from the fabric. Cleaning mechanism The specific
mechanical or pneumatic system used to clean the
fabric. Cleaning sections The number of segments
into which the cleaning mechanism is divided. (An
intermittent baghouse would have a single
section, while automatic or continuous baghouses
would have two or more sections.) Compartments
The number of rooms in a continuous baghouse that
can be entered for maintenance while the
remainder of the baghouse is operating (may
contain one or more cleaning sections).
TABLE 13.2 Common Terminology for Fabric Filter
Collectors
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Cleaning methods Intermittent Periodic cleaning,
with total flow interruption. Automatic
Continuous automatic cleaning, without total
flow interruption. Continuous Continuous
automatic cleaning and maintenance possible,
without total flow interruption. Filtering fabric
area Gross fabric The total effective area of
filter fabric installed in the baghouse. Net
fabric The gross fabric area less the area of
fabric being continuously or periodically
cleaned. Filter-cleaning operations Cleaning
cycle The total elapsed time from commencing to
clean a section of the baghouse to commencing to
clean that same section again. Cleaning interval
The elapsed time from commencing to clean a
section of the baghouse to beginning to clean the
next section. (The cleaning interval times the
number of sections equals the cleaning cycle.
TABLE 13.2 Common Terminology for Fabric Filter
Collectors (contd)
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Cleaning period The total elapsed time that a
section of the baghouse is off-stream for
cleaning. (This time increment determines the
total availability of section gabric for
filtration use.) Filter ratings Air-to-cloth
ratio The unit capacity of a fabric filter,
i.e., the total volume of gas in actual m3/s
divided by the gross or net fabric area in
m2. Operational problems Dusting Dust passing
through the fabric upon initial start-up or
immediately following cleaning. Bleeding Dust
continuously passing through the fabric during
normal operation. Blinding A situation wherein
fabric and dust cake permeability cannot be
maintained. The collected dust so adheres to or
is so embedded in the fabric substrate that it
cannot be removed by the cleaning method
employed. This is evidenced by continually
increasing pressure drop. Source Smith and
Lucas32
TABLE 13.2 Common Terminology for Fabric Filter
Collectors (contd)
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FIGURE 13.16 Typical bag, pocket, and cartridge
filters.
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FIGURE 13.18 Emission inventory.
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FIGURE 13.9 Principle of negative corona
discharge.
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TABLE 13.4 Properties of Fiber Materials
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TABLE 13.7 Standard Parameters for HEPA Filters
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FIGURE 13.19 Typical removal efficiencies.
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FIGURE 13.20 Thermal incineration unit.
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FIGURE 13.23 Adsorption unit.
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FIGURE 13.27 Membrane unit.
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FIGURE 13.28 Elements of a fume control system.
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FIGURE 13.29 Average plume flow rate at roof
truss level for a tapping operation.
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FIGURE 13.30 Average plume velocity and flow rate
during an electric furnace tapping operation.
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FIGURE 13.37 Relative roof monitor opacity as a
function of fume hood suction.
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FIGURE 13.38 Basic procedures for emission
measurements.
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FIGURE 13.39 Example of a measuring-equipment
arrangement with water removal upstream of the
gas-metering device 1. Entry nozzle 2. Probe
tube 3. Particle separator 4. Sampling flow rate
control device 5. Exhauster 6. Gas volume
meter 7. Sampling flow rate measuring device 8.
Water-removing device 9. Duct thermometer 10.
Instrument for measuring effective static
pressure in duct 11. Sensitive differential
pressure instrument connected to Pitot tube 12.
Gas velocity measuring device 13. Humidity
measuring instrument 14. Thermometer at
gas-metering device 15. Instrument for measuring
effective static pressure at gas-metering device.
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FIGURE 13.45 Schematic of particle size analysis
based on the diffraction of forward-scattered lase
r light.
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FIGURE 13.47 Diagram of flame ionization detector.