CZESTOCHOWA UNIVERSITY OF TECHNOLOGYCZESTOCHOWA UNIVERSITY OF TECHNOLOGYCZESTOCHOWA UNIVERSITY OF TECHNOLOGY

TECHNICAL UNIVERSITYOF CZĘSTOCHOWA

TECHNICAL UNIVERSITYOF CZĘSTOCHOWA

ENERGY ENGINEERINGLABORATORY

ENERGY ENGINEERINGLABORATORY

Biomass Co-Combustion and Gasification

Wojciech Nowak

The largest potential and The largest potential and priority for thermal and priority for thermal and utility utility

power plants power plants as well as as well as activation the agricultural activation the agricultural

terrains and the farm terrains and the farm implement of waste landsimplement of waste lands

BIOMASSBIOMASS

The local development of biomass utilization in scale of municipal and village governments creates the large chance of development of these areas as well as the chance of improvement of natural environment

Acquisition of energy from biomass creates the new workplace in sector of power industry, agriculture, forestry as well as production and service of devices and technology, the competitiveness of Polish agriculture and forestry

Barriers to conquest

Accessibility of biomass in proper

Time

Place

With proper price and required properties

Biomass gathered from approx. 80 km gives continuous production approx. 60 MWth

In many cases it is difficult to accumulate biomassthat can guarantee heat production of 30 MWth

Co-Combustion

Why co-combustion?

� Possibility of biomass utilization in already existing heat and power generating plants

� A number of fluidized bed boilers � Risk minimization in price fluctuations and

accessibility of biomass� Lower emissions of atmospheric pollutants� Providing a CO2 neutral fuel source� Low investment costs (it is no necessary to

construct the separate feeding line when 5% of biomass is fired)

Co-combustion of biomass with coal in existing boilers- the most competitive source of renewable energy

� Mixture should be uniform� Mixture should posses proper

heating value and should be stable� Lower gas pollutant emissions� Lower coal consumption

Driving forces of co-combustion

New environmental requirementsSO2, NOx, CO, Dust

Local biomass and wood residues utilizationbark, saw dust, sludges, logs and paper

Cost savings compared to new boiler

Short delivery time

odpady biomasa

wêgielwegiel odpady

biom asa

wegiel

dodatkowe palenisko

Direct combustion in PC boilers

1 � milling system (capacity, wear) 2 � furnace (slagging) , 3 �superheater (corrosion); 4 �convective heat exchanger (fouling, erosion); 5 � DeNOx (deactivation, capacity, erosion); 6 �ESP (capacity); 7 � ash (utilization); 8 � DeSOx (capacity); 9 � DeSOx residue (utilization); 10

� flue gas (emission)

Co-combustion in PC boilersAreas of Concern

Unterrsberg S. Bio-Energy, Budapest, 2003

Circulating Fluidized Bed Boilers

CFB technology offers wide fuel flexibility

Coal- Anthracite- Bituminous- Sub-Bituminous- Lignite

Waste Coal- Bituminous Gob- Anthracite Culm- Coal Slurry

Petroleum Coke- Delayed- Fluid

Wood Residues- Bark- Chips- Wood Dust- Forest Residue- Demolition Wood

Peat

Oil Shale

Gas- Natural- "Off" Gases

Sludge- Paper Mill- De-Inking- Municipal

Refuse Derived Fuel

Paper Waste

Tires

Agricultural Waste- Straw- Olive Waste

Biomass feeding into existing CFB boilersA.Feeding into coal before the combustion chamber B.Feding directly into the combustion chamber

Biomass feeding line

Existing coal feeding line

FW materials, 2003

Temperature distribution in the combustion chamberTemperature distribution in the combustion chamber

CoalCoal

Coal Coal + + biomassbiomass

`Local heat transfer flux in the combustion chamberof CFB boiler with ununiform fuel feeding

Heat flux[kW/m2]

Area of concern

Agglomeration & Defluidization

• Poor mixing or low gas velocity, Tbed>Tashsoft

• Parameters: ug, T, mbed, dp,bed, λλλλ, O2

Important: fuel & bed composition (Na, Ca, K, CaSO4,silicates, aluminasilicates: problems)

Getting rid of agglomeration:uniform temperature, change of fuel or sorbent,ev. their PSD (from coarse to fine ones)

Problems of CofiringProblems of CofiringProblems of CofiringProblems of Cofiringof Coal and Alternative Fuelsof Coal and Alternative Fuelsof Coal and Alternative Fuelsof Coal and Alternative Fuels

• Agglomeration and Defluidization

• Fouling

• Corrosion

• Fuel composition - fluctuations

• Toxic byproducts in flue gas and ashes:CO, NOx, SOx, PM, VOC, DXNs, PAH,

Trace elements, alkalis

• Ash reuse/management

Surface corrosion

Caused mainly by acids in FG.Kinetics affected by fuel composition (mainly HCl)

Low oxygen and chlorine above 0.1% – critical

Counteractions:Separation of chlorine, HCl/Cl2 capture (in the furnace,

FGD, ESP)

Getting rid of chlorine by sorbent injection (eg. Na2O,Na2CO3, CaCO3)

Fuel composition & its fluctuation• Fluctuation of oxygen concentration in the furnace• Effect: emission of toxic byproducts

Waste combustion: emission control - difficultbiomass – O.K.

Lowest emission of CO & other carbon compounds at 6-10% O2in the flues gas

Counteractions:good mixing of fuel and oxygen, fuel change, higher temperature,more uniform fuel composition (eg. segregation, etc.)

Counteractions: Air staging, SNCR, SCR

NOxNONONONOxxxx from FBC: mainly NO (>90%) and NO2FBC: less NOx than from PC, CFB: less than BFB

Creation of NOx:fuel, thermal & fast NOx

FB: NOx mainly from fuel

Emission increase with air ratio, temperature, concentration in fuel

N2O

0 100 200 3000

100

200

300

N2O

[ppm

, prz

y 6%

O2]

NO2 [ppm, przy 6% O2]

Węgie l A Węgie l B Węgie l C Węgie l D

CounteractionsCounteractionsCounteractionsCounteractions:

higher temperature, less O2,

more CaCO3, combustion

of poor fuels (during devolatization

NH3 rather than HCN is created)

p=patm, λλλλ>1: sulfationReductive condition: CaS

Most efficient at 800-9000C

Dolomite – more sorbent, expensive, attritionbut acts agains defluidyzation

Desulfurization:dry, semi-dry and wet methodNew sorbents (synthetic, zeolites,

fly ash based sorbents, etc.

SOx

Lower emission:filters, bagfilters, ESPs, cyclones, multicyclones, ceramic

barrier filters (T<12000C)Also wet methods: scrubbers, spray towers

Coarse solids: gravitation, centrifugal, fine solids: electrostatics

PM 2.5 PM 2.5 PM 2.5 PM 2.5 –––– ultraultraultraultrafinesfinesfinesfines!!!!!!!!!!!!

PM

Trace elementsEmission from FBC lower than PC:

lower temperaturegood gas-solids separation (cyclones)good FG cool down

FBC: roughly 90% of metals is captured in the fly ash

DIOXINS=PCDDs, PCDFs, Co-Planar PCBs

Source ofSource ofSource ofSource of CreationCreationCreationCreation::::C, OC, OC, OC, O2222, H, H, H, H2222, Cl, Cl, Cl, Cl2222 + + + + Temperature Temperature Temperature Temperature Br, F (?)

O

O

12

346

98

7

O

12

346

98

7

12 3

4

6 5

co-planar PCBs

1'2'3'

4'

6'5'

PCDDs

PCDFs

SOME ‘DIOXIN PEOPLE’:SOME ‘DIOXIN PEOPLE’:SOME ‘DIOXIN PEOPLE’:SOME ‘DIOXIN PEOPLE’:H. Rghei, G. Eiceman, Chemosphere, 1982

F. Karasek, L. Dickson, Science, 1987Vogg, Stieglitz, Gullett, Bruce, Hiraoka, Hagenmaier, Milligan, Altwicker

DXNs – Some Facts:

• Chlorine source:

NaCl, PTFE, PVC, herbicides, etc.

• No effect of chlorine source

(organic, nonorganic) on DXN formation

• Chlorine Content: ?

• Required:

Reaction Time (>2s), Temperature,

Components, Free Oxygen (>1%)

Average Chlorine Content in Various FuelsAverage Chlorine Content in Various FuelsAverage Chlorine Content in Various FuelsAverage Chlorine Content in Various Fuels(% (% (% (% dry mass basisdry mass basisdry mass basisdry mass basis))))

Wood 0.08-0.13 Municipal Waste 0.05-0.25Bark 0.02-0.4 RDF 0.3-0.8Straw 0.1-1.5 Packages 1-4Refuse Dump Gas 0.005 Car Tyres 0.05-0.07Textiles 0.25 Auto Shredder Dust 0.5-2Newspaper 0.11 Computer parts 0.1-0.5Sewage Sludge 0.03-1 Plastic Waste 3.5PVC 50 Medical Waste 1-4

101 102 103 104 1051E-4

1E-3

0,01

0,1

1

10

100Municipal waste

Hospitalwaste

PCP-treated wood

Dio

xin

Emis

sion

[µg/

kg]

Chlorine Concentration [ppm]

Biomass Thomas & Spiro’sU.S. Summary Data

Low Emission of DXNs:• Less chlorine in fuel (PVC, NaCl separated)• 3T Technique (high Temperature, long residence Time,

better Turbulence) + Quick Quench of the flue gas

Other options:• High Temperature (>5500C) FG – ash separation system

(ceramic filters, ESP, cyclones)• Low Temperature (<1500C) FG – ash separation system• No deposition of fly ash in the flue gas duct• AC injection before the filter (HCl capture)• Flue Gas Recirculation• Injection of inhibitors (ammonia, urea, Na2SO3) and less O2

in the flue gas• Co-combustion with coal (SO2 reacts with chlorine and

steam, DXN formation decreased). FBC advantage!

No DXNs above 600-6500C – low concentration in the furnance

Main Problem:Formation in the FG Duct and Fly Ash Separator (de novo,

100x more behind the ESP than at the furnance outlet

The majorityThe majorityThe majorityThe majority od od od od DXNsDXNsDXNsDXNsis included in the Fly Ashis included in the Fly Ashis included in the Fly Ashis included in the Fly Ash!!!!

OurOurOurOur ApproachApproachApproachApproach::::Fly Ash Pelletization and Reburning in Fly Ash Pelletization and Reburning in Fly Ash Pelletization and Reburning in Fly Ash Pelletization and Reburning in

a a a a Fluidized BedFluidized BedFluidized BedFluidized Bed

Fouling

Condensation of alkalis from th egas phase & fouling on the surfaces

More alkalis (eg. biomass) – more troubles (when the flue gasis cooled down)

Counteractions:• separation of fines from the FG duct,• surface cleaning,• change of composition of fuel & bed,• different shape of surfaces (shorter contact time & area)

BoilerBoiler efficiency with biomassefficiency with biomass

0,0 0,1 0,2 0,3 0,4 0,5 0,60,60

0,65

0,70

0,75

0,80

0,85

0,90

ηη ηη k

X [kg H2O / kg paliwa]

Performance test results

Brown coal Brown coalBiomass

Biomass % (energy) 0 30Load % 100 100Efficiency % 92.7 91.6SO2 mg/m3n 476 356Limestone kg/s 1,18 1.0NOx mg/m3n 224 171CO mg/m3n 26 28

CONCLUSIONS

�Cofiring coal and biomass has been demostrated successfully in several CFB boilers

� Biomass can contain harmfull components like alkalis and chorine, which increase slagging and corrosion

� When converting existing CFB boiler for biomass cofiring, the save share of biomass depends on biomass and coal properties as well as boiler design, and must be determined case by case

�Combined heat and power results in more efficient use of biomass and couls contribute significantly to the economic viablility of electricity from biomass

Biomass gasification

FW CFB Gasifier

850°C

900°C

BOTTOM ASH COOLING SCREW

HOT LOW CALORIFICGAS (750 - 650 °C)

UNIFLOW CYCLONE

BIOFUEL FEED

REACTOR

BOTTOM ASH

GASIFICATION AIR FAN

COOLING WATER

AIR PREHEATER

RET

UR

N L

EG

• Developed in the late 1970s • Driving force the dramatic

increase in oil price• Foster Wheeler has supplied

7 commercial scale CFB/BFB gasifiers producing low CV gasfor different applications

FW materials, 2004

CFB Gasification Advantages� Cheap solid fuels can be converted to gas for

replacing expensive oil or gas � Waste wood� Bark� Other fuel fractions

� Allows the use of local fuel resources� A multi-fuel unit with good fuel flexibility

� Co-combustion in a PC boiler provides also a high electric efficiency for the biomass or waste utilized

Reference list of the atmospheric fluidized bed gasifier

Customer SizeMW

Fuel Application Year

Hans Ahlstrom Laboratory, Finland 3 Misc. Test unit 1981

Oy W. Schauman Ab, Finland 35 Bark,sawdust Lime kiln fuel 1983

Norrsundet Bruks Ab, Sweden 25 Bark Lime kiln fuel 1984

ASSI Karlsborg, Sweden 27 Bark Lime kiln fuel 1984

Portucel, Rodao, Portugal 15 Bark Lime kiln fuel 1985

Kemira Oy, Vuorikemia, Finland 4 1986

Lahden Lämpövoima Oy, Finland 40-70 Biofuels Hot raw gas toboiler

1997

Coal, peat

Test unit, clean gas

Corenso United Ltd., Finland 40 2000Aluminiousplastic waste

Cyclone cleanedgas to boiler

Electrabel, Belgium 50 Biofuels Hot raw gas toboiler

2002

FW materials, 2004

Biofuel/Multifuel Gasifier at Kymijärvi Power Plant, Lahti, Finland

� Direct gasification of wet fuels in an atmospheric CFB gasifier

� Atmospheric CFB gasifier produces 40 � 70 MWth low CV product gas to be co-combusted in a 125 MWe PC boiler

� Product gas replaces part of the utilized coal in the boiler

� Main fuels in the gasifier are local biomasses, industrial waste, paper and plastics

BIOMASS GASIFICATION - COAL BOILER - LAHTI PROJECT

Bottomash

Gasifier

Coal

540 °C/170 bar

Processing

Biomass

Fly ash

Pulverized coal flames

Gas flame

Natural Gas

50 MW

300 GWh/a -15 % fuel input

1050 GWh/a -50 %

350 MW

650 GWh/a -35 %

Power* 600 GWh/aDistrict Heat* 1000 GWh/a

CO2 Reduction -10 %

Biofuel/Multifuel Gasifier at Kymijärvi Power Plant, Lahti, Finland

CFB Gasifier at the Kymijärvi Power Plant

Lahti CFB Gasifier Design DataTotal fuel input to main boiler 2 000 000

MWh/aTotal input to gasifier 300 000

MWh/a

Substitution of fossil fuelsCoal 21.300 tonsNatural gas 15.7 milj.m3

Total energy 15%

Annual operating time of gasifier 6500 h(depending on heat load requirement)

Lahti CFB Gasifier Fuels

Gasifier Effect on Main Boiler Emissions

NOx Decrease by 10 mg/MJ (5 to 10%)SOx Decrease by 20 � 25 mg/MJCO No changeHCl Increase by 5 mg/MJ, base level

lowParticulates Decrease by 15 mg/nm3

Heavy metals Increase in some elements, base level low

Dioxins, etc. No change

Gasifier � PC Boiler Combustion Offers

� Lower environmental emissions� use of coal is reduced � lower CO2, SO2 and NOx emissions

� Better fuel flexibility� Possibility to use local fuel (biomass, recycled

industrial waste, plastics, etc.) resources in high efficiency steam cycle

� Low investment and operation costs� Utilization of existing power plant capacity� Only small modifications to the main boiler� High plant availability

Ruien Design� Plant owner is Electrabel, Belgium

� Gasifier fuel input 50 MW with 50% fuel moisture

� Process electrical efficiency 34% � Main boiler 36%, gasifier energy efficiency 98%

� Produced green electricity 17 MWe

� Annual production 120 GWh

Ruien Gasifier Lay-out

RUIEN

BRUSSELS

Main boiler

Main boiler ESP

Gasifier island

FW materials, 2004

Main boiler feed water

Main boiler furnace

Recycled fuels

CFB gasifier

Pulsing gas

Cooling water

Flare

LP steam

Filters

Fly ash

Bed materials

Gas cooler boiler

Fuel feed system

Gasification of Recycled Fuels

Summary � Development Work

� Gasification as a process proven technology for several fuel types

� Specific fuels e.g. ASR (Auto Shredder Residue) require further testing and development work

� Regarding the concept, development work at the moment is concentrated on clean gas production

� Gas cooling� Gas cleaning� Filter ash final treatment

Summary � Current Commercial Status

Fuels: Status:

- Wood, bark, shavings, saw dust - Commercial

- Recycled industrial waste, paper & -Commercialplastics

- Coal, straw, peat, RDF -Demonstrated

- ASR, other specific wastes - To be developed

Present Status of FW Atmospheric Gasifier Systems

Gasification is a way to high efficiency power production

from biomass and wastes

� Gasification� Gas combustion/co-firing in an existing boiler

Commercial technology

� Lahti 70 MW � Corenso 50 MW� Ruien 50 MW

Authothermal fuel upgradingAuthothermal fuel upgrading

Problems encountered when biomass is co-fired with coal can be avoided

Biomass is initially prepared before final combustion in the boiler

!! increasing carbonification of fuel and increasing energy densityincreasing carbonification of fuel and increasing energy density

!! moremore uniform uniform size distributionsize distribution

!! highhigh--efficient efficient „„distillationdistillation” ” of sulfurof sulfur, , chlorinechlorine, , mercury compoundsmercury compoundsand other gas pollutants from biomass and other gas pollutants from biomass by by lowlow--temperature temperature (750 (750 ooCC) ) heating through the wall without oxygen heating through the wall without oxygen

Biomasswastes

Fuel preparation

GrindingSegragation

Storage

Drying Thermolysis

Combustion

Combustion

Heat recovery Flue gascleaning

Pirolytic gases

to atmosphere

to atmosphere

Clean and upgrading fuel intoPC, CFB, stocker boilers etc

Schematic process of biomass and wasteSchematic process of biomass and wasteupgradingupgrading

Reactor Reactor for for biomass upgradingbiomass upgrading

BIOCARBON

PREBIOCARBON

Products of thermolysisProducts of thermolysis

Volume reductionVolume reduction

BiomassBiomass and biocarbon parametersand biocarbon parameters

Biomass I BBiocarboniocarbon II Biomass II BiocarbonBiocarbon IIIIWa [%] 4 0,7 20 1,0Wh [%] 4,8 4 3 1,9Wt

r .[%] 8,8 4,7 23 2,9Aa [%] 3 17,7 0,6 8,8Va [%] 84,2 32,2 76,3 43(F.C)a [%] 7,8 46,3 20,1 48,3Sa [%] 0,096 0,1 0,075 0,08Ca [%] 36,7 59 39,1 64,3Wg

a [kJ/kg] 18 720 26 790 18 150 24 400Wd

a [kJ/kg] 17 480 25 940 16 860 23 200

Biomass I – mixture of sawdust, wood chips, grass, leafs Biomass II –sawdust

Upgrading processUpgrading process

0 10 20 30 40 50 60 70 80 90 10015

20

25

30

35

40

4,5

Biocarbon II

35 SŁOMA40

4550

556065

7075

c = 80 %

6,5

6,05,5

5,04,5

4,0h = 3,5 %

DREWNO

WĘGIEL BRUNATNY

WĘGIEL KAMIENNY

ANTRACYT

Cie

pło

spal

ania

[M

J/kg

]

Substancje lotne [%]

Biocarbon I

0,0 0,1 0,2 0,3 0,4 0,5 0,60,5

0,6

0,7

0,8

0,9

1,0ηη ηη k

,η,η ,η,ηA

WP

,η,η ,η,ηk(

bioc

arbo

n) , δδ δδ

bioc

δδδδbioc

ηηηη AWP

ηηηη k

ηηηη k(biocarbon)

X [kgH2O/ kgpaliwa]

Biomasaw stanie roboczym

Cieplo do zagospodarowania

ComparisionComparision ofof efficiencesefficiences

Heat densityHeat density

1 2 30

5

10

15

20

25

BiocarbonBiomas aWęgiel kamienny

Cie

pło

spal

ania

[ G

J/m

3 ]

Upgrading network near power and heat generating plantsUpgrading network near power and heat generating plants

Conclusions

� The development of a bioelectricity industry will depend on the competitiveness of bioelectricity with coal

� Policies and regulations have a fundamental role in promoting energy from biomass and in ensuring the sustainability of biomass fuel chain

� There is a little market for biomass feedstocks for electricity generation in utility power plants

� Bioelectricity needs greater integration between energy, environment, and agricultural and foresty policies and a careful selection of technology aimed at the energy

� There is need for advanced conversion technologies such as gasification, upgrading and integration with gas turbines and fuel cells