The Current State of Austrian Pellet Boiler Technology Ingwald Obernberger Gerold Thek S
EN
ER GY
BI O
P
Ca Mg
EC
M AS S
E
U
AIN AB L
ST
K
ASH
ONOMY
BIOS BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz, Austria TEL.: +43 (316) 481300; FAX: +43 (316) 4813004 E-MAIL:
[email protected] HOMEPAGE: http://www.bios-bioenergy.at
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
¾
Austrian pellet market
¾
Standards for pellet furnaces
¾
Pellet combustion technology
Introduction
Feeding Storage Burn-back protection Basic burner principles Technical details (furnace geometry, materials, control systems, boiler technology, de-ashing)
¾
Emissions
¾
Future developments
E
AIN AB
N ER G Y
B IO
P
Ca Mg
K
ASH
ON O MY
Number of newly installed pellet central heating units
EC
L
M AS S
E
S
ST
U
Development of small-scale pellet furnaces in Austria
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
5,000 Source: [Lower Austrian Chamber for Agriculture and Forestry, 2002]
4,000 3,000 4,599
2,000
3,041 1,536
1,000 0
820 205 220
503
592
425
333
1997
1998
1999
2000
2001
Year feed from storage tank
feed from storage room
E
AIN AB
N ER G Y
B IO
P
Pellet production in Austria – present state and outlook
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Ca Mg
EC
L
M AS S
E
S
ST
U
K
ASH
ON O MY
900
Pellet production [1,000 t/a]
300 Source: [Geisslhofer, 2000: Wood pellets in Europe; own enquiries]
250 200 150 100 50 0 1996
1997
*different prognoses for the year 2010
1998
1999
2000
2001
Year
2002
2010* 2010*
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Pellet consumption in Austria (year 2001)
¾ About 12,300 pellet central heating systems already installed in Austria ¾ Total nominal boiler capacity installed: about 220 MW ¾ Annual utilisation rate: about 72 % ¾ Boiler full load operation hours: 1,500 h p.a. ¾ Net calorific value of pellets: 4.9 kWh/kg pellets
ÎPellet consumption in Austria approximately 94,000 t/a ÎPellet export about 22 % of annual production: 26,000 t/a
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
General framework in Austria
¾ Investment subsidies granted in Austria on average 25 % (depending on the Austrian provinces) ¾ Currently 12 pellet producers active in Austria ¾ Pellet quality regulated by ÖNORM M 7135 and the standard of the Austrian Pellets Association ¾ Quality of pellet furnaces regulated by ÖNORM EN 303-5 ¾ Supply of pellets in Austria assured throughout the country by a well organised distribution network ¾ About 30 manufacturers of small-scale pellet furnaces in Austria
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Standards for furnaces fired with pellets
Austria: ÖNORM EN 303-5 Sweden: SPCR 093 SP-Method 2453 parameter
300 kW
SPCR 093 SP-Method 2453 15 kW
testing required by law
+
-
pellets are the only permitted fuel
-
+
all solid fuels (biomass and fossil fuels) are permitted
+
-
maximum organic carbon (OGC) emission [mg/MJNCV]
40
34
maximum CO emission [mg/MJNCV]
500
900
maximum NOx emissions [mg/MJNCV]
150
-
maximum dust emissions [mg/MJNCV]
60
-
minimum combustion efficiency
*
75%
limited validity period for the certificate
-
2 years
valid for heating boilers with a nominal boiler capacity up to
*depending on the nominal boiler capacity (see following slide)
ÖNORM EN 303-5
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
L
M AS S
E
K
ASH
ON O MY
Minimum combustion efficiency according to ÖNORM EN 303-5
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
88
Combustion efficiency [%]
S
ST
U
86
combustion efficiency [%] =
84
boiler heat produced fuel heat input (NCV)
82 80 78 76 74 72 1
10
100
Nominal boiler capacity [kW] manual feed
automatic feed
1000
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Pellet combustion systems Pellet central heating systems
Pellet single stoves Pellet burners
Source: [RIKA Metallwarenges.m.b.H. & Co KG, Austria]
Source: [GUNTAMATIC Heiztechnik GmbH, Austria]
Source: [Gilles Energie und Umwelttechnik GmbH, Austria]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Feeding and storage systems used
Feeding systems ¾ Screw conveyor (inflexible) ¾ Screw conveyor (flexible) ¾ Pneumatic system ¾ Pneumatic system / screw conveyor combination ¾ Agitator / screw conveyor combination
Storage systems ¾ Storage room (83 %) ¾ Integrated store (17 %) ¾ Underground storage tank
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Agitator / screw conveyor combination
Motor for conveying screw
Screw conveyor
Source: [KWB – Kraft und Wärme aus Biomasse GmbH, Austria, 2002]
Agitator
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Burn-back protection systems (1)
Cellular wheel sluice
Fireproof valve
Source: [COMPACT Heiz- und Energie-systeme GesmbH, Austria] Source: [KWB – Kraft und Wärme aus Biomasse GmbH]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Extinguisher system
Source: [Anton Eder GmbH, Austria]
Burn-back protection systems (2) Fall shaft
Source: [GUNTAMATIC Heiztechnik GmbH, Austria]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
Basic principles of wood pellet burners
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
¾ Underfed burners
¾ Horizontally fed burners
¾ Overfed burners
Source: [Handbook of Biomass Combustion and Co-Firing, IEA, 2002]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Boiler with spiral scrapers
Underfed burner
Intermediate storage
Flue gas Conveying screw
Secondary air Retort
Fan
Primary air Ash box Fuel supply (stoker screw) Source: [KWB – Kraft und Wärme aus Biomasse GmbH, Austria, 2002]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Geometry of the combustion chamber – important parameters
¾ Air staging ¾ Mixing of secondary air and flue gas (position and design of the secondary air nozzles) ¾ Appropriate dimensioning of primary and secondary combustion zone (residence time) ¾ Good utilisation of the furnace volume (flow distribution) ¾ Even temperature distribution (furnace temperature control)
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Secondary combustion zone
Secondary air
Primary combustion zone Primary air
Source: [GUNTAMATIC Heiztechnik GmbH, Austria]
Air staging and optimised mixing between flue gas and secondary air
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Design and optimisation of the nozzles for the injection of secondary air and re-circulated flue gas
Vectors of the flue gas velocity [m/s] in the horizontal cross-section right over the secondary air nozzles
Basic nozzle design
Improved nozzle design
Î CFD-based furnace and nozzle design of great relevance Source: [BIOS BIOENERGIESYSTEME GmbH, Austria, 2002]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
L
M AS S
E
S
ST
U
K
ASH
ON O MY
Materials used for combustion chambers
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
price
heat storage capacity
corrosion resistance
deposit resistance
stainless steel
++
-
+
+
firebrick
+
++
++
-
silicon carbide
-
-
++
++
material
-...low / expensive +...medium ++...high / cheap
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Control systems
Load control ¾
Guiding value:
feed water temperature
¾
Variables:
fuel and primary air feed
Combustion control ¾
Guiding value:
O2, CO or O2 and CO concentration in the flue gas (lambda, CO or CO/lambda control)
¾
Variable:
secondary air supply
Temperature control ¾
Guiding value:
temperature in the combustion chamber
¾
Variables:
flue gas recirculation or water-cooled furnace walls
Pressure control ¾
Guiding value:
pressure in the combustion chamber
¾
Variable:
induced draught fan (frequency)
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
CO-λ-characteristic and influencing parameters
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
CO [mg/m3] 4
10
¾ increased fuel water content ¾ partial load
103 102 101 100 Source: [Good, ETH Zürich, 1992]
1
2
3
4
5
Lambda [-]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Boilers
Geometry ¾ Usually vertical fire tube boilers (one or three-pass boilers)
Boiler cleaning ¾ Fully automatic by spiral scrapers in the fire tubes ¾ Semi-automatic by spiral scrapers in the fire tubes with a lever from the outside ¾ Manually
Automatic boiler cleaning systems increase the efficiency and reduce dust emissions
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Fully automatic boiler cleaning system
Source: [BIOS BIOENERGIESYSTEME GmbH, Austria, 2002; furnace of KWB - Kraft und Wärme aus Biomasse GmbH]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
De-ashing systems
¾ Usually ash collection in an ash box Æ ash box must be emptied periodically ¾ Ash compaction systems partly applied Æ ash box must be emptied periodically in longer periods of time ¾ Fully automatic de-ashing system by a screw conveyor in an external container Æ ash box must be emptied only about once a year
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Compactor
Ash box
Source: [KWB – Kraft und Wärme aus Biomasse GmbH, Austria, 2002]
Ash compaction system
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
200
Emission factor [mg/MJ (NCV)]
S
ST
U
Emissions Source: Spitzer et al, 1998; BLT Wieselburg, 2002
(500)
180
163
160 140 120 100
87 73
80 60
43
40
29
22
20
11
1
0 CO
TOC
test stand measurements
NOx (NO2) field measurements
dust limiting value
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
CO emissions – comparison between old and new pellet furnaces
300
Source: Jungmeier et al, 1999; BLT Wieselburg, 2002; results from test stand measurements
CO [mg/MJ]
E
AIN AB
N ER G Y
E
S
ST
U
200
100
0 1996-1998
1999-2001
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Dust emissions – comparison between old and new pellet furnaces
50
Source: Jungmeier et al, 1999; BLT Wieselburg, 2002; results from test stand measurements
40
Dust [mg/MJ]
E
AIN AB
N ER G Y
E
S
ST
U
30
20
10
0 1996-1998
1999-2001
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
TOC and NOx emissions – comparison between old and new pellet furnaces
TOC (total organic carbon) ¾ No differences detected due to the generally low level of the organic carbon emissions
NOx (nitrogen oxides) ¾ NOx emissions depend on the fuel nitrogen content (no thermal NOx formation) Æ no clear trends detected Æ NOx reduction by primary measures possible (depends mainly on air staging, residence time and temperature of the flue gas in the primary combustion zone)
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Future developments
¾ CFD-aided furnace development and optimisation ¾ Medium-scale combustion systems (nominal boiler capacity up to 500 kWth) ¾ Reduction of particulate emissions ¾ Small-scale dust burners (utilisation of pulverised pellets) ¾ Utilisation of herbaceous / non-woody biomass fuels ¾ Combination of pellets with solar systems ¾ Small-scale CHP systems (e.g. Stirling engines)
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Stirling engine application for small-scale pellet furnaces
¾ Pel: 1.1 kW ¾ Electric efficiency: 23 % ¾ Service life: 40,000 hours ¾ Fired by wood pellets ¾ 10 plants in operation (pilot plants)
Source: [Sunpower Inc., USA, 2001]
E
AIN AB
N ER G Y
B IO
P
Ca Mg
EC
K
ASH
L
M AS S
ON O MY
E
S
ST
U
BIOENERGIESYSTEME GmbH Sandgasse 47, A-8010 Graz
Summary
¾ Rapidly expanding pellet market in Austria ¾ Several actors, quality standards and subsidies supporting this development ¾ Proven feeding and combustion technologies available from many furnace manufacturers which ensure a fully automatic operation ¾ Low emissions with a decreasing tendency for new furnaces ¾ Several research activities and promising developments focusing on new fields of application, new biomass fuels and emission reduction
