Biomass EnergyBiomass EnergyElectrical Conversion TechnologiesElectrical Conversion Technologies

byby

Dr. Eric Bibeau, Dr. Eric Bibeau,

University of ManitobaUniversity of Manitoba

(Alternative Energy Research)(Alternative Energy Research)

November 04, 2003November 04, 2003

BIOMASS FEEDSTOCKBIOMASS FEEDSTOCKBiomass is natures way to store solar energyBiomass from carbon and sunlight

sunlight6 CO2 + 6 H20 = C6H12O6 + 6 O2

Biomass – Crop residues– Forest residues– Energy crops– Animal waste– Municipal waste

Components– Cellulose, hemi-cellulose, lignin

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BIOMASS ANALYSISBIOMASS ANALYSISEnergy components – Carbon– Hydrogen– Oxygen

Pollution components– Ash (fly ash, particulate emissions)– Residual char (particulate emissions)– Sulfur (SOx)– Nitrogen (Fuel NOx)

Operational problem components– Alkali (Potassium, Sodium: stick ash, corrosion, fouling)– Water (wood: energy neutral at 67% MC; sludge at 75% MC)– Tars (sticky, plugs filters and engines)

Waste Wood Dry WetCarbon 49.91% 24.96%

Hydrogen 5.93% 2.97%Nitrogen 0.34% 0.17%

Sulfur 0.04% 0.02%Chlorine 0.01% 0.01%Oxygen 42.35% 21.18%

Ash 1.42% 0.71%Moisture (H2O), (AR)

Biosolids Dry WetCarbon 32.60% 19.56%

Hydrogen 4.71% 2.83%Nitrogen 5.13% 3.08%

Sulfur 1.60% 0.96%Chlorine 0.12% 0.07%Oxygen 16.34% 9.80%

Ash 39.62% 23.77%Moisture (H2O), (AR)

50.00%

40.00%

BIOMASS FUEL ANALYSISBIOMASS FUEL ANALYSIS

Fuel heating value– HHV (includes condensable)– LHV

Fuel analysis– Fixed carbon or char– Volatiles– Ash– Water

MJ/kgBiomass 19.7 MJ/kg

Hydrogen 119.5 MJ/kgCoal 25.5 MJ/kg

LHV

Volatile (dry) 55.5%Fix carbon (dry) 24.5%

Ash (dry) 20.0%Moisture (AR) 30.0%

Waste Wood

BIOMASS FUEL ANALYSISBIOMASS FUEL ANALYSISStages of conversion– Heat biomass

low, medium, high temperature heat low, medium, high pressure

– Drying processremove water (evaporation)

– Pyrolysis drive off volatiles and make gas (H2, CO, CO2, CH4, tar…)

– Gas phase oxidizationgas phase reacts with oxidant (heat release)

– Char oxidationfixed carbon reacts with oxidant (heat release)

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BIOMASS CONVERSION FOR ELECTRICAL GENERATIONBIOMASS CONVERSION FOR ELECTRICAL GENERATION

Feedstock Supply– Bio-solids– Animal waste– Sludge– Food waste– MSW– Urban wood– Agricultural

residue– Forest waste– Energy crops

Conversion Technology– Combustion– Gasification– Pyrolysis– Anaerobic

digestion– Supercritical

Product– Electricity from gas or

heat– Electricity from turbine

waste heat HRSG

– Fuel for electricity generation

Syn gas (H2, CO)Bio liquid fuel (long chain molecules) Solid fuel (charcoal)Hydrogen for fuel cellsMethanol for fuel cells from H2, CO2, CH4

BIOMASS TECHNOLOGIESBIOMASS TECHNOLOGIESCombustion (high temperature)– Combustion of organic matter (char and volatiles) with

excess oxygen– Can use heat to make steam to drive a steam turbine– Particulate, NOx, SOx

Gasification (low/high pressure, limited O2)– Thermal decomposition of organic matter into a gas by

controlling oxygen levels– Goal is to produce a clean gas at high pressure to feed to

a gas combustion turbine or ICE– Need to handle unconverted char, filter, and cool gases

BIOMASS TECHNOLOGIESBIOMASS TECHNOLOGIESPyrolysis (slow and fast, without O2)– Thermal decomposition of organic matter into a gas in

absence of oxygen (no NOx)– For power production

make syn-gas (CH4, CO2, H2, CO, Tar) to burn in boilercondense long chain volatiles quickly into bio-fuel to use in boiler, ICE, or turbine

– Need to handle char and low PH of bio-fuelAnaerobic digestion (fermentation)– Bacterial decomposition of organic matter without oxygen– Produce gas (CH4, CO2 and possibly H2) and burn in internal

combustion engine or gas turbine – Undigested material can be used as fertilizer

BIOMASS TECHNOLOGIESBIOMASS TECHNOLOGIESCombustion– Bring fuel and air together and make steam from

heat– Combustion boiler

Refractory (small systems mainly for heat)Water walled

– Fluidized bed boilerIdeal for solid fuelsBed made up of sand, fuel, air, re-circulating gasesBubbling bed (large bubbles formed)

– Circulating fluidized bed boilerMore particulate blown from the bed

BIOMASS COMBUSTION BOILERBIOMASS COMBUSTION BOILERGrate systemWater wallsConvection sectionProduces steam for turbine (or process use)Fuel drying, pyrolysis, and char combustion must occur on grate and in lower furnace– Fuel carry-over fouls convection

sections

Over fire airLow NOx burnersReburning for NOx control

BIOMASS ELECTRICAL BIOMASS ELECTRICAL POWER PLANTPOWER PLANT

Largest plant in North America

BUBBLING FLUIDIZED BED BOILERBUBBLING FLUIDIZED BED BOILERMix fuel with sandBubble gas through sandPromote fuel reactions– longer fuel residence time – more surface area as fuel

particles break downBetter char conversionRemove ash from bottomAsh and sand wear– increased ash and silica

particles at back-end– sand makeup

CIRCULATING FLUIDIZED BED BOILERCIRCULATING FLUIDIZED BED BOILERTechnology adapted from coal – achieve more carbon

burnoutcoal fixed carbon > wood fixed carboncoal volatiles < wood volatiles

Circulate sand up in upper surfaceCollect sand with U beamsErosion– Derated power

COAL COCOAL CO--FIRE BIOMASSFIRE BIOMASSUse wood as re-burning fuel in coal combustorIntroduce biomass below OFA to create elements that will react with NOUS estimates co-firing biomass in coal plants at 20 to 30 GW by 2020

Biomass

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1 TO 5 MW BIOPOWER SYSTEMS1 TO 5 MW BIOPOWER SYSTEMSSteam cycle– Not economically attractive– Limited cogeneration

Organic Rankine cycle– Increased low pressure to reduce turbine/condenser size– Organics ¼ of water enthalpy– Remote operation

Entropic cycle– Rankine cycle adaptation– Not yet published– Pre-vaporized fluid entering heater– Inherent high temperature coolant output

Heater

Recuperator

Cooler

Flue Gas

Coolant

90°C

60°C

1010°C

222°C

343°C

65°C

104°C

160°C

269°C

Power Unit

GASIFIERGASIFIERProduces CO and H2 with some CH4, H2O, N2, Char particles, Ash, Tars– Drying stage– Pyrolysis stage

occurs in presence of limited Air/O2tar, gas, fix carbon, CH4

– Oxidation stage Air, steam, pure O2 to produce CO2 and CO

– Reduction stageC and CO reacting with H2O and CO2 to produce CO, CH4, H2

Flue gas requires cleaning and cooling at low temperatures: cyclone and filters– Remove tar, dust, ammonia, sulfur, alkali

FIXED BED GASIFIER TECHNOLOGIESFIXED BED GASIFIER TECHNOLOGIESDirection of airflow and fuel changes– Co-current or counter

current

Updraft GasifierDowndraft GasifierCrossdraft Gasifier

MOVING BED GASIFIER TECHNOLOGIESMOVING BED GASIFIER TECHNOLOGIES

Pressurization is expensiveAvoid ash meltingMoving bed more efficient

Circulating Fluid Bed GasifierBubbling Fluid Bed Gasifier

Char Indirect

Gas Indirect

GASIFIER FOR POWER GASIFIER FOR POWER PRODUCTIONPRODUCTION

GASIFIER TECHNOLOGIESGASIFIER TECHNOLOGIESClass Type Strengths/Weaknesses Power Production

DowndraftDowndraft models: low heating value, moderate particulates, low level of tars

UpdraftUpdraft models: higher heating value, moderate particulates, high level of tars

CrossdraftCrossdraft models: low heating value,moderate particulates, high level of tars

Bubbling Higher rates of throughput over fixed bed

Circulating Improved mass and heat transfer from fuel

Higher efficiency

Higher heating value gas

Gas Indirect Highest rates of throughput

Char Indirect Highest gas heating value

Moderate tar and particulate content in gas

Indirect Large scale

Fluidised bed

Fixed bedSmall to

medium scale

Medium scale

GASIFIERSGASIFIERSUPDRAFT DOWNDRAFT CROSSDRAFT CIRCULATING CHAR

Reaction Temperature [°C] 1000 1000 900 850 850

Gas Exit Temperature [°C] 250 800 900 850 850

Fuel Capacity [t/h] 10 0.5 1 20 20

Electrical Capacity [MWe] 1 – 10 0.1 – 20 0.1 – 2 2 – 100 20 – 100

Tar Content very high very low very high low low

Particulate Content good moderate high very high very high

Overall Feed Specificity moderate specific moderate flexible moderate

Fuel Mixing poor poor poor excellent excellent

Fuel Size Flexibility very good good good fair fair

Fuel Moisture Flexibility very good fair good good poor

Ash Feed Flexibility poor poor poor very good good

Fluff Feed Flexibility very good fair good good good

Turndown Ratio good fair good good very good

Scale-up Potential good poor poor very good good

Start-up Facility poor poor poor good excellent

Management Facility very good very good very good fair poor

Control Facility fair fair fair very good excellent

Cost safety very low low low fair poor

Carbon Conversion very good very good poor very good excellent

Thermal Efficiency excellent very good good very good good

Gas Lower Heating Value poor poor poor fair excellent

good good

poor excellent

fair poor

EFFICIENCY

fair fair

fair poor

very good excellent

good good

good excellent

poor poor

INDUSTRIAL POTENTIAL

very good very good

good poor

very good very good

very good very good

fair fair

very high very high

FEED REQUIREMENTS

flexible moderate

1 – 20 20 – 50

GAS CHARACTERISTICS

moderate low

800 850

10 20

FIXED BED FLUIDISED BED INDIRECT GASIFICATION

850 850

BUBBLING GAS

PYROLYSISPYROLYSISAdd heat and no oxygen to biomass (crack large molecules)

– pyrolysis begins at low temperaturesFast pyrolysis produce

– 75% organics vapor (liquefy into bio-fuel)– 10% pyrolysis gases (burn to produce heat)– 15% charcoal (use for drying and heating organics)– may require external energy to drive process (natural gas)

Slow pyrolysis – significantly reduces the percentage of bio-fuel– increases the percentage of charcoal produced– has enough gas to drive process

Decouples biomass– time, place, space– create fuel with 5 time heating value but looses energy from original source

Bio-fuel – condensed long chain volatiles– breaks down and corrosive– mainly phenols and low PH– high water content even when using bone dry fuel

PYROLYSISPYROLYSISExample of pyrolysis systems– Cleaner gas when bio-fuel is

burnt– Use ICE or turbine– Sell bio-fuel and charcoal

Rotating Cone (fast pyrolysis)Screw Type

(slow pyrolysis)

Bubbling Bed (fast pyrolysis)

ANAEROBIC DIGESTERSANAEROBIC DIGESTERSBiological degradation– Mesophilic bacteria (25oC-38oC)– Thermophilic bacteria (50oC-70oC)

Gas CH4, CO2, H2S, N2, NH4Use gas in ICE or micro turbineNeed to scrub gasContinuous and batchFour main technologies– Lagoon type– Plug flow– Complete mix– Temperature-phased

Farm Feedstock

ProductsBiogasFiberLiquid

: Renewable CHP: Soil conditioner

: Liquid fertilizer

AnaerobicDigester

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ANAEROBIC DIGESTERSANAEROBIC DIGESTERS

Slurry In

Heat In

Heat InHeat In

Slurry In

Slurry In

Slurry In

Covered Lagoon

TPAD

Plug Flow

Complete Mix

Effluent Out Effluent Out

Effluent Out

Effluent Out

COVERED LAGOON DIGESTERCOVERED LAGOON DIGESTERManure storage lagoon Impermeable cover that traps gas produced during decompositionLiquid manure less than 2% solids– for pig and cow farms using flush systemRequire large lagoon volume Least expensive methodBetter in warm climates

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COMPLETE MIX DIGESTERCOMPLETE MIX DIGESTERSuitable for manure that is 2%-10% solids– engineered heated tank above or below ground– mechanical or gas mixer to keep solids in

suspension– expensive to construct – cost more than a plug-flow

digester to operate and maintain

Temperature control– applicable to cold climates

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PLUGPLUG--FLOW DIGESTERS FLOW DIGESTERS Manures with solids concentration of 11%–13%Raw manure slurry enters one end of a rectangular tank– decomposes as it moves through the tank – fresh manure added at one end – pushes older material to the opposite end – material flows through the tank in a "plug"

Cover traps CH4/CO2 gasMinimal maintenanceProblems with pig manure – low fiber content

Suspended heating pipes circulate hot water 25°C to 40°C

TEMPERATURETEMPERATURE--PHASED PHASED TPAD – Temperature-Phased Anaerobic Digesters

Variation of complete mixTwo-staged reactor to optimize methane recovery– high temp – low temp

Low solids manureKills more pathogens

FLUE GAS CONDITIONINGFLUE GAS CONDITIONINGBaghouseBaghouseParticulate (PM10 limit)

SOx limitNOx limitCO limitHg limit

CycloneCyclone

Electrostatic Electrostatic PrecipitatorsPrecipitators Tar removalTar removal

ScrubberScrubber

PICTURE REFERENCESPICTURE REFERENCES– “Steam its generation and use” issued by

Babcock and Wilcox– “An assessment of potential for electrical

power generation from gasification of municipal bio-solids using Sungas energy gasification process” by Christopher Evans, University of Manitoba, Manitoba Hydro Gasification Project, 2003

–

www.entropicenergy.com

www.jfbioenergy.com– www.dynamotive.com– www.zebu.uoregon.edu

–– www.geothermie.de– www.roseworthy.adelaide.edu– www.biogasworks.com– www.westbioenergy.org– www.sterling-energy.com– www.combustion-net.com– www.btgworld.com– www.alstar.com– www.vidir.com

ACKNOWLEDGEMENTACKNOWLEDGEMENTFunding for Alternative Energy from Manitoba Hydro

http://www.jfbioenergy.com/http://www.dynamotive.com/http://www.zebu.uoregon.edu/http://www.entropicenergy.com/http://www.geothermie.de/http://www.roseworthy.adelaide.edu/http://www.biogasworks.com/http://www.westbioenergy.org/http://www.sterling-energy.com/http://www.combustion-net.com/http://www.btgworld.com/http://www.alstar.com/http://www.vidir.com/

BIOMASS FEEDSTOCKBIOMASS ANALYSISBIOMASS FUEL ANALYSISBIOMASS FUEL ANALYSISBIOMASS CONVERSION FOR ELECTRICAL GENERATIONBIOMASS TECHNOLOGIESBIOMASS TECHNOLOGIESBIOMASS TECHNOLOGIESBIOMASS COMBUSTION BOILERBIOMASS ELECTRICAL POWER PLANTBUBBLING FLUIDIZED BED BOILERCIRCULATING FLUIDIZED BED BOILERCOAL CO-FIRE BIOMASS1 TO 5 MW BIOPOWER SYSTEMSGASIFIERFIXED BED GASIFIER TECHNOLOGIESMOVING BED GASIFIER TECHNOLOGIESGASIFIER FOR POWER PRODUCTIONGASIFIER TECHNOLOGIESGASIFIERSPYROLYSISPYROLYSISANAEROBIC DIGESTERSANAEROBIC DIGESTERSCOVERED LAGOON DIGESTERCOMPLETE MIX DIGESTERPLUG-FLOW DIGESTERSTEMPERATURE-PHASEDFLUE GAS CONDITIONINGPICTURE REFERENCES