Air Pollution Management 2006

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Air Pollution Management 2006

• Combustion appliances
• for small-scale use of biofuels
• Lennart Gustavsson
• SP Swedish National Testing and Research
  Institute

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Technology for small-scale biomass combustion

• Domestic heating

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Technology for small-scale biomass combustion

• Heating of public and commercial premises

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Technology for small-scale biomass combustion

• Small-scale district heating

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Biofuels for domestic heating

• Log wood
• Wood chips
• Pellets
• Energy crops ????

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Equipment for domestic heating

• Logwood heating boilers
• Logwood stoves, fireplaces and inserts
• Tiled stoves, soap stone stoves (accumulating)
• Pellet burners, boilers and stoves
• Stokers and furnaces for wood chips etc
• ?????

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Traditional wood-fired central heating boiler
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Modern wood-fired central heating boiler
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Commercial modern boiler for wood
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Wood stoves - examples
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Accumulating stoves
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Underfed burner - principle
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Underfed burner - commercial
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Horisontally fed burner - principle
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Horisontally fed burner - commercial
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Overfed burner - principle
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Overfed burner - commercial
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Lambda control (air-fuel ratio)
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Pellet stove
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Alternative pellet fuels

• Bark
• Reed canary grass
• Salix
• Forest residues
• Straw
• Energy grain
• Peat
• Lignine

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Solar Pellet System
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Small-scale district heating - fuels

• Wood chips
• Forest residues
• Bark
• Sawdust
• Pellets
• Briquettes

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Small-scale district heating - equipment

• Grate firing
• - Reciprocating grates
• - Fixed grates
• - Vibrating grates
• - Rotating grates
• Burners for pellets or pulverized fuels
• Bubbling Fluidized Beds (BFB)

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Plant for combined heat and power production
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Grate firing - principle
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Reciprocating grate most common
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The grate system
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Rotating grate - underfed
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Vibrating grate
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Burner for pulverized pellets
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• Small-Scale Combustion Control
• Some New Research Results
• David Eskilsson
• Henrik Quicklund
• Claes Tullin
• SP Swedish National
• Testing Research Institute

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Agenda

• In-situ sensors measuring CO Hydrocarbons
• - Different sensor techniques
• - Examples of measurements
• Cross sensitivities
• Conclusions sensors
• Combustion control of a pellet burner (13 kW)
• - Different control strategies
• - Control algorithm Lambda optimisation
• - Test Results
• - Conclusions

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Gas sensors for unburned carbon compounds

• Commercial gas sensors available
• Measures the amount of unburnt, CO hydrocarbons
  gives a sum signal
• Measures directly in the flue gas duct
• Relatively cheap, 100 300

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Testing of three control strategies during
different combustion conditions

• Control strategies
• Original Adjustment of fuel flow during
  installation
• Lambda control Fixed O2 set point
• Lambda optimisation Optimised O2 set point
  (varied)
• Combustion conditions Nominal Heat Output
• Load 13 kW 9 kW
• Fuel Quality 8 mm pellet (standard), 6 mm
  pellet, Bark pellet (bad fuel, high ash content)

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The Problem!
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Lambda optimisation Varied set point
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Conclusions

• Sensors
• Both tested sensors are able to measure the CO
  transients
• Long term stability have to be tested further
• Control system lambda optimisation
• Advantages with a lambda optimised system for a
  pellet burner
• Higher efficiency lower fuel costs
• Higher fuel flexibility lower fuel costs ?
• Higher availability - compensate ash
  slagging
• Warning system bad combustion
• Disadvantages
• Higher costs (sensors and control system) first
  introduced in boilers above 300 kW