BioEnergy BioEnergy in Manitoba in Manitoba Gasification Myths Gasification Myths Gasification Workshop – Truths, Myths & Opportunities Greenwood Inn, Winnipeg, Manitoba, Nov 15, 2004 Dr. Eric Bibeau Dr. Eric Bibeau Mechanical & Industrial Engineering Dept Mechanical & Industrial Engineering Dept Manitoba Hydro/NSERC Chair Alternative Energy Manitoba Hydro/NSERC Chair Alternative Energy
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Dr. Eric BibeauDr. Eric BibeauMechanical & Industrial Engineering DeptMechanical & Industrial Engineering Dept
Manitoba Hydro/NSERC Chair Alternative EnergyManitoba Hydro/NSERC Chair Alternative Energy
Gasifier Terms UsedGasifier Terms UsedDistributed power (< 5 MWe)– applicable to Manitoba
Gasification for producing power– direct = syngas– indirect = hot flue gas
Gasifier types discussed – gasifier to produce a syngas to make power (direct)– gasifier or gasifier/combustor to produce a hot flue gas
to make power (indirect)Gasifier for heat (not covered)– similar aspects apply– focus on power generation
Why Look at MythsWhy Look at MythsNeed strong focus on realization of BioPower energy rather than on developing a technology– gasification is favored in the public eye– gasification is in news
…the EERC has completed over 100 hours of continuous operation of a biomass gasifier firing wood chips… The process converts wood chips into gas (similar to natural gas) that can be fired in a small gas turbine (microturbine), diesel, or conventional combustion engine.
Why Look at MythsWhy Look at MythsNeed to be able to question information– “Experience from the Second World War shows, however,
that properly designed wood gasifiers, operated within their design range and using fuels within the fuel specifications (which may differ between designs), can provide a sufficiently tar free gas for trouble-free operation”
– From “Mechanical Wood Products Branch,” Forest Industries Division FAO Forestry Department
large scale applications (500 kW and above): US$ 1000 per installed kW and upwardsmedium scale applications (30 - 500 kW): 300 - 800 US$/kW (gasifier only) small-scale applications (7 - 30 kW): 150 US$/kW, extremely reliable and should need no special operation and maintenance skills
Why Look at MythsWhy Look at MythsRequired to improve BioPower technology– continuously questioning statements and findings
a positive (negative) way to move forward understanding pitfalls allows solutions to be put forward
– many gasification projects have failed – some types of gasification projects have succeeded– understand how this technology
could be effectively applied in Manitoba compares to other forms of biomass conversion technologiesexport market potential for Manitoba
BioPower is GasificationBioPower is Gasification
indirect
direct
Limit air Excess airNo air
Add air
Add airAdd air
No air
Add air
Add air Add air
direct indirect
BioPower is GasificationBioPower is Gasification650°C 315°C
367 kPa 258 °C
111 kPa 315 °C 336 kPa
483 °C
377 kPa 127 °C
13.1%cycle eff. 58.3%
cycle energy
108 kPa 185 °C
101 kPa 15.6 °C
Air Heater
7.4% overall eff.
Compressor Turbine / Expander
Recuperator
combustion air
56.7% recovery
Thermal Oil Heat Transfer
TURBODEN srl
synthetic oil ORC
Conversion
1000°C 310°C
250°C300°C
60°C
80°C Liquid Coolant
Air heat dump
17%
Input Heater 59.9% recovery
Entropic Fluid Heat
Transfer
ENTROPICpower cycleConversion
1000°C 215°C
170°C400°C
60°C
90°C Liquid Coolant
Air heat dump
17.6%
Input Heater 68.2% recovery
Brayton Air Cycle (indirect)
ORC (indirect)
Bio-oil (direct)
EHC(indirect)
Superheater
Economizer
Boiler
Feed Pump
Deaerator
Attemporator
Turbine
2%blowdown
Condensate returnand makeup
10
9
6
4
3
18
7
Co-generation process
5
Small steam CHP
(indirect)
Gasifiers are ScalableGasifiers are ScalableScalability issues surrounding gasifiers are more complex than combustion devices– thermo-chemical conversion depends on the geometry of the gasifier – affects the thermal properties of the fuel impacting reactions
CO2 + CH4 + C2H4 + Cs Secondary Pyrolysis Primary Tar → Secondary tar (CHxOy) +
CO + CO2 + C2H4 + H2 Homogenous Gas Phase Reactions
Gaseous tar Secondary Tar → C + CO + H2 Hydrogen oxidation H2 + ½ O2 H2O + 242 MJ Water shift CO + H2O CO2 + H2 + 41 MJ CO oxidation CO + ½ O2 CO2 + 283 MJ Methane oxidation CH4 + ½ O2 CO + 2 H2 + 110 MJ Dry reforming CH4 + CO2 + 247 MJ 2 CO + 2 H2 Steam reforming CH 4 + H2O + 206 MJ CO + 3 H2 Water-gas shift CO2 + H2 CO + H2O + 41.2 MJ Methane formation CO + 3H2 CH4 + H2O + 206 MJ
Heterogeneous Reactions (solid and gas phase) Partial oxidation of carbon Cs + O2 CO2 + 393 MJ Methane formation Cs + 2 H2 CH4 + 75 MJ Steam gasification Cs + H2O + 131.4 MJ CO + H2 Oxidation of char and hydrogen Cs + 2 O2 + H2 CO2 + 2 H2O + 393 MJ Boudouard char Cs + CO2 + 172.6 MJ 2 CO
Gasification is More EfficientGasification is More EfficientWhat does the statement mean?– high reaction efficiency as gasifier converts most of the fixed
carboncaution: reduction reactions of the fuel may be affected by moisture content and this is not well understoodBFB combustion devices covert most of the carbon
– produce more power using direct method vs indirectGasifiers are often reported in the literature as being more efficient than combustion systems• there is limited practical experience to support this claim
• Possible advantages of gasifiers are that burning syngas in a turbine allows for greater overall cycle efficiency • gas turbine Brayton cycle with high efficiency gas turbines
can theoretically outperform a steam-Rankin cycle if properly implemented
Gasification is More EfficientGasification is More Efficient• Recent white paper on gasification reports
plant efficiencies for integrated biomass gasification combined cycles of 35% to 50% • these values are promising • not achievable for small systems and for high MC
fuels• values seem higher than those achievable in
practice by large fossil fuels power systems • where fuel moisture is of minor important
• Rule of thumb • No combined cycles under 20 MWe
Gasification is More Gasification is More EfficientEfficient
At low MC
Small
Condensing Steam
Small steam with
cogeneration
Organic Rankine
Cycle
Air Brayton
cycle
Entropic cycle Gasification1
Heat recovery loss (MW)
8.0 8.0 7.8 12.3 5.3 11.0
Cycle loss (MW)
15.2 16.5 15.3 12.1 7.2 10.5
Power generated (MWe)
3.03 1.75 3.13 1.83 3.68 4.71
Cogeneration heat (MWth)
0.0 15.0 14.5 0.0 16.4 0.0
1Assumes Producer gas has heat value of 5.5 MJ/m3 and cooled down to room temperature
Vegetation maps Netley-Libau
Marsh 2001
Netley 1979 Area Moisture HHVPlant Available kJ/kgSpecies (ha) min max (%) min max DryCattail 4987 8,528 118,267 17.1 7,070 98,043 18,229Bulrush 3247 3,215 32,584 18.2 2,629 26,653 17,447Reed Grass 650 1,112 1,170 12.8 969 1,020 17,285Rushes, Sedges.. 922 954 6,638 12.4 836 5,819 15,838Sum 9,806 13,808 158,659 11,505 131,535Weighted average 16.7 18,024
Harvest Biomass(Wet tonne) (Dry tonne)
Gasification is More EfficientGasification is More EfficientModeling distributed power systems with 50% MC feedstock– realistic small size systems
limit cycle improvement opportunities– cost effective for technology for small size
limit external heat/power to systemadapt component efficiencies to scale
– model system as if building system todaymodel actual conversion energy system ignore parasitic power for bio-oil & gasifiermass and energy balances
– account for every step in conversion– exclude use of specialized materials
BioBio--oil Overall Energy Balanceoil Overall Energy Balance
Biomass Feed 50% moisture
Drying/Sizing to 10% / 2 mm Pyrolysis
21.5% energy loss 32% energy
Char 45.6%
energy loss
Engine/ Generator
6.4% Electricity
60% energy Bio-oil
8% energy loss
18.5%
3%
3%
5%
N2 Sand
Electricity: 363 kWhr/BDtonne
Pyrolysis heat: non-condensable gas + some char (no NG)
Pyrolysis power: 220 – 450 kWhr/BDtonne (335 or 5%)
Engine efficiency: 28% (lower HHV fuel; larger engine; water in oil lowers LHV)
New Hampshire experience studying bio-oil•What was learned?
•What information was missing?
Gasification Overall Energy BalanceGasification Overall Energy Balance
Biomass Feed 50% moisture
Drying to 25%
40% energy Producer Gas
7.75% Electricity
Engine/ Generator Gasification
15%
15% energy loss
60% energy loss
17.25% energy loss
Electricity: 440 kWhr/BDtonne
Assume require 25% MC and no sizing requirements (conservative)Ignore parasitic loads: dryer, gas cooler, gas cleaning, tar removal, fans (conservative)Heat to dry fuel comes from process (3.8 MJ/BDkgfuel)100% conversion of char to gas (conservative)HHV of syngas = 5.5 MJ/m3 dry gas (16% of natural gas)
Gasification Overall Energy BalanceGasification Overall Energy Balance
Biomass Feed 50% moisture
Drying to 25%
40% energy Producer Gas
7.75% Electricity
Engine/ Generator Gasification
15%
15% energy loss
60% energy loss
17.25% energy loss
Electricity: 440 kWhr/BDtonne
Low HHV of gas affects efficiency of engineAssume ICE operates at 75% of design efficiency15% heat from producer gas dries fuelNo heat lost across gasifier boundaryLimited useable cogeneration heat
Small Steam Overall Energy BalanceSmall Steam Overall Energy Balance
Limit steam to 4.6 MPa and 400oC (keep material costs low)
Could use economizer to pre-heat combustion airMany ways to improve efficiency
Biomass Feed50% moisture
Steam Cycle5.7%
Electricity
Heat Recovery
115°C steamcogeneration
40.5%energy loss
53.8%energy loss
Air Brayton CycleAir Brayton Cycle
Electricity: 420 kWhr/BDtonne
Flue gas temperature inlet to heater limited to 650oC for material requirementsRecuperator with single-stage turbineNo preheat of combustion air (34% increase in efficiency)Tube metal temperatures limited to 565oC Turbine thermal efficiency 85%
Gasifiers Have Low EmissionsGasifiers Have Low EmissionsBiomass emissions in general– CO2 neutral– CO
Excess air and good mixing
– CH4active use can be better or worse than natural decay
– Particulatecan be addressed
– Sulfurbiomass (except for MSW) has low S
– NOximportant in all biomass conversion technologies every time air is injected
Gasifiers Have Low EmissionsGasifiers Have Low Emissions
Biomass emissions in general
CO2 no change except for composting
CH4 is 21 times worst of a GHG than CO2; biomass energy production is the ONLY option that makes senseNatural way has more
NOx
SO2 no influence of technology
Gasifiers Have Low EmissionsGasifiers Have Low EmissionsDo gasifiers have lower emissions than combustion devices?– direct?– indirect?
Gasifier should have less fly ash because of reduced carry over as less air flow is required Is there a real advantage using syngas?– does this outweigh the complexity of the flue gas
treatment, fuel preparation, low moisture content requirements, and loss of the latent heat of the gas
– indirect method: is it easier and cheaper to clean the flue gas?
Gasifiers Have Low EmissionsGasifiers Have Low EmissionsGasification is seen as being the environmental choice– is this justified?– what are the physical mechanism to justify this?– what about CHP; GHG offsets
Look at designs– combustors– gasifiers
Particulate levels are not low enough to use the syngas directly in an engine How emissions change with the type of fuel and moisture content is also not certain
Gasifiers Have Low EmissionsGasifiers Have Low EmissionsNote: Gasification systems using the direct approach have two sources of emissions – NOx, Sox, CO, PM need to be looked at from gasifier
and engineEmissions need to be reported after the engine– Cannot stop at energy from product or intermediate
formExamples of multi-step energy conversion systems– bio-oil– renewable hydrogen– ethanol from fermentation
Gasifiers Have Low EmissionsGasifiers Have Low EmissionsBTG 2001 study of emissions from 21 gasifiers in Europe– 4 out of 21 gasifiers met the NOx limit– 5 out of 21 met CO limits– 8 out of 21 met particulate limits
California study (From National Renewable Energy Laboratory, NREL/SR-570-27541, 1999)
Consider that gasifiers in these studies operated possibly with dryer fuel
Gasifiers Can Handle Any FuelGasifiers Can Handle Any Fuel• Most gasifiers sensitive to the fuel properties • Cannot support high moisture fuel content
• what gasifier manufacturers mean is that the fuel can be pre-processed to make the feedstock acceptable to their gasifiers
• requirements for this preprocessing are often not well understood economically or from an energy efficiency point of view
• little attention given in drying the fuel and evaluate the impact on gasification performance, efficiency, and costs
• fuel drying consumes heat and power and increases capital and operating costs
• alternatively higher moisture fuel can be mixed with lower moisture feedstock or with waste hydrocarbon fuels
• In traditional combustion biomass boiler systems• fuel variations lead to boiler upsets
Gasifiers & Energy Crops are FavorableGasifiers & Energy Crops are Favorable• Consensus for marginal lands
• grow high yield crops• use entire plant and weeds• limit fossil fuel use• use proven and economical conversion method
• Manitoba has unused waste biomass– forest biomass
wood residues from sawmills– agriculture residues
straw from grain– animal wastes
swine, poultry, bovine– municipal wastes
organic residues– non-mainstream biomass
cattails and peat moss
See Gasification Workshop, Gimli, Manitoba, September 30, 2004
Gasifier Performance is WellGasifier Performance is Well--KnownKnown
Need to develop the technical and economical aspects of gasification Determine if biomass syngas could be co-fired into power boilers in the provinceDetermine if gasifiers can economically pre-dry high moisture content fuelInvestigate the co-generation potential of gasifiers for direct and indirect conversion– double the economic return – displaces natural gas important in Manitoba for GHG offsets
Syngas cleanup and conditioning technology
Gasifier Performance is WellGasifier Performance is Well--KnownKnownMethods to condensate the moisture and tars Biomass plant economics are poor compared to fossil based power systems– important to achieve a simplified system that is trouble-
free – gasifier need to operate at very high capacity factor
BTG, “Inventory of biomass gasifiers manufacturers and installations,” Final Report, EWAPprogram, October 2001.
Gasifier Concentrates Heavy MetalsGasifier Concentrates Heavy Metals
This has been shown in Manitoba for MSWMechanism of how the fixed bed interacts with the oxidizing agent is not well understoodIf gasifiers perform better than a deep bed combustion system, it is not known why
Gasifiers are a Low Cost SolutionGasifiers are a Low Cost SolutionGasifiers are low cost has yet to be demonstrated practically for all scales Need to demonstrate the cost advantages as require additional equipment:– fuel: sizing & drying– direct: tar, water, PM, latent heat removal to inject
syngas into engine– engine: production versus low BTU engine
Cost for biomass turnkey installations for gasifiers should not exceed (high side)
Base Power ($/kW installed) Capital Cost5 MWe 3,0001 MWe 3,5000.25 MWe 4,000
Gasifiers are a Low Cost SolutionGasifiers are a Low Cost SolutionCost estimates vary according to industry, region, and the payback time required – payback period can be reduced by up to 50% if the waste
heat can be use productively – payback for different capital cost and power rates
*Revenue for distributed biopower systems using 50% MC biomass
1
Gasifiers are a Low Cost Solution Gasifiers are a Low Cost Solution CHP Revenue Chart CHP Revenue Chart
Gasifier Has Limited Operator RequirementsGasifier Has Limited Operator Requirements
This point is crucial in the use of this technology for distributed powerGasifiers need to function with little operator assistance or they will potentially fail in the market placeSteam engineer (cost?)– indirect approach
Impact of system on automation and operator requirements– direct approach (focus on gas quality and hard to control)– indirect approach (decoupled)
Gasification is Beyond CombustionGasification is Beyond CombustionStatement based in part on gasification being
– more environmentally friendly – more efficient– less costly– “in fashion”
Bias against combustion based on – bad experiences in the past (older technology)– time when their was no regulation– doing the impossible: disposal of very wet biomass using combustion
If all technology meets environment emissions, what is better?– gasifier– gasifier/combustion– combustion– incinerator– fast and slow pyrolysis
Which technology holds better promise for emissions reduction inthe future?
Tampier M., Smith D.W., Bibeau E.L. and Beauchmin P., "Identifying environmentally preferable uses for biomass resources: Phase 2 report: life-cycle emission reduction benefits of selected feedstock-to product threads," Envirochem Services Inc. Project sponsored by the National Resource Canada, the National Research Council, and the Commission for Environmental Cooperation, 2004.
BioPower distributed technologies for 50% MC
direct indirectTechnical complexity
25%
Gasifiers are Best at GHG DisplacementGasifiers are Best at GHG Displacement
Waste biomass application (residues)– often no fuel usage attributed to biomass– transportation (35% MC)
0.0249 kgfuel/km/BDtonne 3.2 kgCO2 released for 40 km
– from emissions point transportation of biomassvery positive on CO2 displaced
– < 1% CO2 cost per 100 kmeconomic limitation
– $65/BDtonne for 125 km
Gasifiers are Best at GHG DisplacementGasifiers are Best at GHG DisplacementElectricity (kWe- hr)– displace electricity from various sources– look at (1) location, (2) average electricity
on the grid, (3) additional load– favorable to displace fossil fuels generation
Electricity Emissions Average Marginal Provincial Emission
CO2
Remote communities
CHP Impact
Gasifiers are Best at GHG DisplacementGasifiers are Best at GHG DisplacementHeat (kWth- hr)– integrated areas
displace oil, natural gas, electricity
– non-integrated areadisplace oil
Northern Community: special case– off-grid power from transported diesel– off grid heat from transported oil– very favorable to CHP
ORC, EHC, and small steam CHP
Gasifiers are Best at GHG DisplacementGasifiers are Best at GHG DisplacementScenario Description Emissions
per kWe-hrTypical Regions
1 Low carbon intensity power generation: 90% of nuclear or large hydropower; 10% natural gas
CO2: 52 g Québec, British Columbia, Manitoba; France; Norway; Sweden
2 Moderate carbon intensity power mix:65% nuclear/large hydro, 25% coal, 10% natural gas
CO2: 288 g Canadian average; Ontario; Atlantic Canada; Austria; Belgium
3 High coal/oil content in power production (50%); nuclear/large hydro: 25%; natural gas: 25%
CO2: 588 g United States average, Denmark; Germany; Mexico; Spain; U.K.
4 Very high coal/oil content 75%, nuclear/large hydro 15%, natural gas 10%
CO2: 761 g Alberta, Saskatchewan, central U.S.; Greece; Ireland; Netherlands
-900-800-700-600-500-400-300-200-100
0
CHP SYSTEMSSmall Steam Turboden Entropic
GH
G E
MIS
SIO
N
(kgC
O2/
BD
tonn
e)
Heating OilNatural Gas
Power
Heat
Gasifiers are Best at GHG DisplacementGasifiers are Best at GHG DisplacementDistributed Systems and 50% MCDistributed Systems and 50% MC
-1400
-1200
-1000
-800-600
-400
-200
0
EMISSION REDUCTIONS for CHP SYSTEMS
GH
G E
MIS
SIO
N(k
g CO
2/BD
tonn
e)
Scenario 1Scenario 2Scenario 3Scenario 4
LargeSteamPow er
SmallSteamPow er
BraytonCycle
Pow er
Bio-oilConver.Pow er
Gasif.Conver.Pow er
SmallSteam
CHP
TurbodenCycleCHP
EntropicCycleCHP
Displacing oil for heat
Gasifiers indirect
Gasifiers direct
Manitoba
Gasifiers are Best at GHG DisplacementGasifiers are Best at GHG DisplacementBioEnergyBioEnergy in a Northern Manitoba Communityin a Northern Manitoba Community
2 MWe Community Subsidized Power System BioPower SystemPower (2 MWe) tonne CO2 0 tonne CO2
Heat (10 MWth) tonne CO2 0 tonne CO2
Total tonne CO2 0 tonne CO2
115532305534,608
Power: Diesel Fuel EHCCHPManitoba Northern Community
Heat: Oil Biomass (local or pellets)2 BD tonne/MWe-hr