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Flue Gas Cleaning The state of the art
Presentation by Michael Kaden Pr Eng Dipl
Ing Member Nat. Ass. For Clean Air (NACA)
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Flue Gas Cleaning The state of the art
Many stacks Are still emitting high levels of
particulate
But particulate emission control
requirements will become more and more stringent
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Flue Gas Cleaning The state of the art
Reasons for excessive particulate emissions
Particulate is extremely fine
Actual measured Size Distribution
Standard Distribution
Tests conducted May 1999 at the John
Thompson Training center boiler South Africa
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Flue Gas Cleaning The state of the art
Equipment is operated at unsuitable
conditions i.e. cyclones running at part load
gas velocities
All values for 2000 mg/Nm3 inlet loading with 12
mm mean particle size
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Flue Gas Cleaning The state of the art
Equipment worn defective
Repair or Upgrade ?
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Flue Gas Cleaning The state of the art
Additional reasons for excessive particulate
emissions
Operation is not at optimum Equipment is not
maintained to the best standard Required
maintenance and repairs are not carried
out Operation is incorrect or outside of
specification Untrained operators run the
equipment Best available fuel is not
used Combustion air is not properly controlled
RECTIFY !
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Flue Gas Cleaning The state of the art
What systems are available to control
Particulate emissions ?

• Electrostatic precipitator
• Bag house fabric filter
• Wet scrubber
• High efficiency cyclones

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Flue Gas Cleaning The state of the art
Selection criteria
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Gas Cleaning The state of the art

• Evaluation of ESP for industrial boilers
• High cost (investment, maintenance operation)
• Complex large size plant with sub-systems
• Requires constant gas conditions (sulphur, temp,
  moisture)

• Evaluation of bag filters for industrial boilers
• High cost (investment, maintenance filter
  bags)
• Difficult to handle sulphur and sparks
• Not robust (one faulty bag destroys efficiency

• Evaluation of wet scrubbers for industrial
  boilers
• High cost (large water treatment plant)
• Difficult to separate fine particulate
• Sulphur control costly difficult

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Flue Gas Cleaning The state of the art

• Evaluation of cyclone grid arrestor
• Low collection efficiency due to
• Wrong design (see velocity analysis)
• Air ingress
• Bad manufacturing quality
• Lack of maintenance (blockage of cyclone cells)
• But cyclone system advantages are low cost and
  robust installation
• Can a cyclone reach efficiencies of ESP / Bag
  filter / Wet scrubber?
• This question triggered our cyclone development
  Program
• in 1994 to improve cyclone efficiency and to
  invent the
• dry spray agglomeration principle

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Flue Gas Cleaning The state of the art
History 1975 - 1980 work with Prof. Stairmond
(UK) Cyclones for coal fired gas turbine 80 MW
PFBC 1993 1998 basic research in cyclone
technology CyDesign - Cape Town development
center
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Flue Gas Cleaning The state of the art
On site technology studies testing
Glass melting furnace
JTA boiler training center
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Flue Gas Cleaning The state of the art
Commercial applications of high efficiency
cyclones
BurnerMax Fluidized bed furnace High efficiency
cyclones operating at 400 C
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Flue Gas Cleaning The state of the art
Project 1996 / 97 30 year old Büttner solid fired
wood chip dryer equipped with low efficiency
cyclone. Emission gt 650 mg / Nm3
Solution Step 1 retrofitting of high
efficiency cyclones Reduction of emission to lt
100 mg / Nm3
First idea of agglomeration spray in 1997
Step 2 installation of THERMAX agglomeration
sprays upstream of cyclones Reduction of
emission to lt 20 mg / Nm3
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Flue Gas Cleaning The state of the art
High efficiency cyclone plant with fully
evaporative fine agglomeration sprays (Installatio
n 1997) Efficiency gt 99 Emission lt 20 mg / Nm3
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Flue Gas Cleaning The state of the art
What is the agglomeration spray?

• Water spray with very fine droplets
• Fully evaporative (dry system)
• Droplets capture small particles
• and agglomerate them
• Larger particles are easily collected

Typical water consumption 30 liter / t steam
generation
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Flue Gas Cleaning The state of the art
Case study

• Wet scrubber installed at a
• 130 t/h JTA water-tube boiler
• Inlet conditions
• 5000 mg / Nm3
• 5 (250 mg / Nm3) lt 5 micron
• Emission gt 300 mg / Nm3
• Required 120 mg / Nm3

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Flue Gas Cleaning The state of the art
Solution Installation of 3 horizontal
spraytrees
Water consumption minimal. Fully
evaporative Final emission lt 100 mg / Nm3
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Flue Gas Cleaning The state of the art
Current CyDesign specifications for advanced
cyclone technology Integrated cyclone system
with fully evaporative agglomeration water spray
(20 l / h per cyclone)
To provide a robust, economic, low maintenance,
very high performance, flue gas cleaning system
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Flue Gas Cleaning The state of the art
Cyclone parts are manufactured to high precision
as erosion corrosion resistant castings
Wax dies
Cyclone vortex blade ring with pressure recovery
Castings
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Flue Gas Cleaning The state of the art
CyDesign - Reference list Flue gas cleaning
installations
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Flue Gas Cleaning The state of the art
Outlook To offer industry a robust and cost
effective system to reduce emissions to the
highest standards !
For a cleaner Environment!
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