Combined heat and power production biofuels

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Combined heat and power production - biofuels

• ICRE Joensuu, Finland, 18th Sept. 2009
• Petri Rousku
• North karelia university of Applied Sciences

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Conventional electricity production

• Condensating power plants(electricity only)
• CHP-plants (combined heating and power)
• Combustion engine power plants
• Hydropower plants
• Gas turbines

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New alternatives

• Wind generators
• Fuel cell power plants
• Photovoltaic plants

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Conventional production equipment

• Steam boiler
• Steam turbine
• Generator
• District heat exchanger

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Steam turbine
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Combined heat and power production

• Principle
• 1. steam produced in the boiler
• 2. turbine rotation by steam feed
• (-gt and generator rotation)
• 3. residual heat recovery in the heat exchanger
  -gt district heat
• Aim maximize electric power/ heating capacity
• gtelectricity production dependant on heating
  demand

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Large biofuel CHP plant features
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Case Kaukaan Voima 2010, Lappeenranta, Finland

• Heating capacity 385 MW (district heat, process
  steam)
• Electrical pwer 125 MW
• Circulating fluidized bed boiler (CFB)
• Fuel flow rate at maximum output 150 kg/s
• Meaning ca. 80 truckloads of biofuel/ day
• Logostical and resource challenge

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Small-scale CHP-plant tehcniques with woodfuels

• Technical outlook and usability
• Petri Rousku
• North karelia university of Applied Sciences

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Small-scale CHP

• Techniques
• Gasifier gas engine
• Micro steam turbine steam boiler
• ORC (organic Rankine cycle) heat boiler
• Fuel cell
• Microturbine, several applications
• Stirling engine heat boiler

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Applications for woodfuels?
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Stirling engine

• Simple construction overhaul period even 60000
  h
• Outer heat source -gt anything
• Small power scale, 2-100 kW
• Work gas helium, air

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Stirling engine principle (beta type) (Wikipedia)
1. Power piston (dark grey) has compressed the
gas, the displacer piston (light grey) has moved
so that most of the gas is adjacent to the hot
heat exchanger.
2. The heated gas increases in pressure and
pushes the power piston to the farthest limit of
the power stroke.
3. The displacer piston now moves, shunting the
gas to the cold end of the cylinder.
4. The cooled gas is now compressed by the
flywheel momentum. This takes less energy, since
when it is cooled its pressure dropped.
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Stirling

• Applications for wood chips, pellets
• Aim high work gas temperature
• gt combustion temperature 1300 oC
• gt combustion air preheating -gt ca. 500 oC
• gt hot heat exchanger efficiency aimed!
• gt structural demands for the boiler!

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Chip boiler stirling 35 kW (Mawera)
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Stirling usability?

• Good with natural gas and oil
• Woodfuels
• Electic output decrease engine efficiency ca. 25
  (compare natural gas ca. 30)
• Fuel quality alteration -gt combustion gas
  temperature unstability
• Complex hot heat exchanger sweeping unit
• High combustion temperature -gt ash melts
• -gt can the grate last long enough?

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ORC power plants

• Used since 1960s
• Thermal oil boiler silicone oil-ORC process
  (many organic circulation fluids) single phase
  turbine generator ca. 1500-3000 rpm
• gt100 kWe n. 2 MWe
• For e.g. 6 MW boiler, 800 kWe ORC

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Traditional ORC

• Reliable
• Not very sensitive to unstability of combustion
  process
• Vaporization temperature ca. 300 oC
• Thermal oil expensive, end use/storage?

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ORC 800 kW Weiz, Austria
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High-spped ORC

• Smoke gas directly to steam generator -gt no
  thermal oil circulation
• Circulating media toluene vaporization 350 oC
• High-speed turbogeneraator 1828000 rpm
• gt no gearbox, but inverter -gt grid frequency
• Modular structure, unit power 170 kWe

Radial turbine, generator rotor, cooling blower
and feed pump (Lappeenranta University of
Technology)
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High-speed ORC (Tri-O-Gen)
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High-speed ORC / wood chips

• Steam generator contamination/ efficiency?
• Steam generator structure/ price/ safety
• Other circulating media than toluene
• gtefficiency?
• sizing -gt heat to district heating?
• Modular structure -gt price
• No thermal oil -gt price
• Variating-speed generator evens the unstability
  of the combustion process
• Not available yet?

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Microturbine applications

• Micro gas turbine commercialized for natural
  gas, coming for biogas
• Fuel cell micro gas turbine
• Fuel cell /biogas
• High-speed turbine/ work gas air
• High-speed steam turbine commercialized

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Micro steam turbine (Savonia Power)

• Standard module 2007, district heating
  application 5,9 MW(th)
• Vapour 1,65 kg/s, 60 bar, 470 C
• 1 MWe electric power, efficiency ca. 80,
  electric power/heating capacity 0.26
• No oil for lubrication etc.
• Inverter adjustment, no gearbox
• 1 MWe-

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Gasification techniques

• Down-draft gasifyer (gasifying air and fuel to
  same feed direction)
• Dry fuel
• Low product gas tar content
• Up-draft gasifyer
• Combined down-draft up-draft gasifyer
• Wet and recirculation fuels
• Relatively low tar content

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Novel gasifyer (Condens)
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Gasifyer gas engine

• Example gasifyer 2 MW
• gt electricity 600 kW
• gt heat recovery from engine cooling 1 MW

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Gasifyer gas engine usability

• Gasification techniques advancing
• Fuel quality alteration still problem?
• gt tar content -gt engine problems
• gt for e.g. wood chip dryer -gt fuel quality
  homogenous
• Gas engine usage costs high

Wood chip dryer (Xylogas)
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Biofuels/ small-scale CHP

• Gasifyers particularly interesting
• Already in the market, but not completely problem
  free
• Gas engine electricity production rate relatively
  good
• More profitability to heating entrepreneurship?
• Profitable in Middle Europe already now?
• More demands for fuel quality!!!
• National subsidies?