1

Technologies for Treating Dairy Manure

Gasification

Developing Projects and Partners to Comprehensively Treat DairyManure in the San Joaquin Valley

11 January 2006Modesto, California

Bryan M. Jenkins, University of California

Gasification:Thermochemical Conversion• Pyrolysis—thermal decomposition of organic

material through heating

• Gasification—conversion of solids or liquids tofuel- or synthesis-gases through gas-formingreactions

• Combustion (solids)—exothermic oxidationinvolving pyrolysis, gasification, andheterogeneous and homogeneous oxidationreactions

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Pyrolysis and Gasification asIntegral Processes in Combustion

Z916

Gasifier

3

Thermal Gasification

Fuel + Oxidant/HeatFuel + Oxidant/Heat

CO + HCO + H22 + HC+ HC + CO + CO22 + N + N22 + H + H22O +O +

Char + Tar + PM + HChar + Tar + PM + H22S + NHS + NH33 + +

Other + HeatOther + Heat

Partial Oxidation/Air or OxygenPartial Oxidation/Air or Oxygen

Steam/Carbon Dioxide/HydrogenSteam/Carbon Dioxide/Hydrogen

Indirect HeatingIndirect Heating

Classification by Reactor Type:Fixed/Moving Beds

• Updraft– Countercurrent– High moisture fuel (<60%

wet basis)– High tar production except

with post-reactor catalyticcracking or dual stage airinjection

– Low carbon ash

• Downdraft– Cocurrent– Moisture < 30%– Lower tar than uncontrolled

updraft– Carbonaceous char

• Crossdraft– Adaptation for high

temperature charcoalgasification

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Swedish design downdraft gasifier for mobile applications

Small Power Systems: CPC

• Fuel handlingincorporating dryer

• Downdraft gasifier withdry scrubbing toproduce low-Btuproducer gas

• Engine-generator setsrated 5-50 kWe

• Can operate in CHPmode

• 50 kWe unit designedfor 144 hourcontinuous operationbefore shut down forcleanout

• Capital cost $700-3,500/kWe (not fullydemonstrated)

5

Small Power Systems: Chiptec

• Crossdraft gasifier toproduce low-Btuproducer gas

• Principally used in heatapplications withoutgas cleaning(effectively 2-stageburners)

• Cogeneration systems35 kWe to 5 MWe(steam turbine)

Fixed-bed indirect gasifier

BGP Gasifier

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Classification by Reactor Type:Fluidized Beds

• Bubbling beds– Lower velocity

– Low entrainment/elutriation

– Simple design

– Lower capacity and potentially less uniformreactor temperature distribution thancirculating beds

• Circulating beds– Higher velocity

– Solids separation/recirculation

– More complex design

– Higher conversion rates and efficiencies

Demonstration Biomass IGCC

• Varnamo, Sweden– FW-Sydkraft 6 MW

electric

– Pressurized fluidizedbed

• Burlington, Vermont– FERCO dual-fluidized

bed

– Not tested in IGCCmode

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Classification by Reactor Type:Entrained Beds

• Solids or slurryentrained on gasflow

– Small particle size

– Entrained flow usedas component insome developmentalpyrolytic biomassreactor systems

ChevronTexaco Gasifier

Classification by Oxidation Medium

• Air gasification (partial oxidation in air)

– Generates Producer Gas with low heating value (~150 Btu ft-3) and highN2 dilution.

• Oxygen gasification (partial oxidation using pure O2)

– Generates synthesis gas (Syngas) with medium heating value (~350Btu ft-3) and low N2 in gas.

• Steam gasification– Generates high H2 concentration, medium heating value, low N2 in gas.

Can also use catalytic steam gasification with alkali carbonate orhydroxide

• Carbon dioxide• Hydrogen• Indirect heated--pyrolysis

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Gasification Reactions and Products

% by volume CO 22 H2 14 CH4 5 H2O 2 CO2 11 N2 46

Typical Clean, Dry Gas Compositionfrom air-blown gasifier

Simplified Reaction System forCarbon

C + O2 = CO 2 Oxidation C + CO 2 = 2CO Boudard Reaction C + 2H2 = CH4 Hydrogasification C + H2O = CO + H 2 Water-gas reaction s C + 2H2O = CO 2 + 2H2 CO + H2O = CO 2 + H2 Water-gas shift CO + 3H2 = CH4 + H2O Methanation

Composition of Raw Gas from Steam Gasification

% by volume dry (except as n oted)

H2O 30 – 45 (wet)

CH4 10 - 11

C2H4 2.0 - 2.5

C3 fraction 0.5 – 0.7

CO 24 – 26

CO2 20 – 22

H2 38 – 40

N2 1.2- 2.0

H2S 130 – 170 ppmv

NH3 1100 – 1700 ppmv

Tar 2 – 5 g Nm -3

Particulate Matter 20 – 30 g Nm -3

Lower Heating Value ~350 Btu ft -3

Advantages of Gasification

• Produces fuel gas for more versatile application in power generationand chemical synthesis.

• Potential for higher efficiency conversion using integrated gasifiercombined cycles compared with conventional Rankine steam cyclepower systems.

• Typically lower temperatures than direct combustion thus decreasespotential alkali volatilization, fouling, slagging, and bedagglomeration (fluidized beds) although for high alkali, high ashfuels such as manure, slagging and bed agglomeration can beproblems. Can also reduce heavy metal volatilization.

• Lower volume of gas requiring treatment to reduce NOx and SOxemissions compared to combustion flue gas.

• Fuel nitrogen evolved principally as NH3 and sulfur as H2S, morereadily removed than NOx and SO2 in combustion systems.

• Applications for power generation at smaller scales than directcombustion systems although gas cleaning is primary concern andexpense

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Gasification Constraints

• Gas cleaning required for use of fuel gas in engines,turbines, and fuel cells– For reciprocating engines, tar and particulate matter removal

are primary concerns, tar removal difficult to achieve. Reactordesigns influence tar production, some newer two stage gasifiersreduce tar but cleaning is still an issue. Need for cool gas tomaintain engine volumetric efficiency leads to tar condensationand waste water production for wet scrubbing systems. Enginederating for gas from air-blown reactors.

– For gas turbines, alkali concentration in gas must be kept low(typically less than 1 ppmv), need for hot gas cleaning tomaintain high efficiency. Alkali typically removed by condensingon particles and hot filtering at temperatures ~1,300°F.

– Fuel cells require clean gas and alkaline, phosphoric acid, andPEM types intolerant of high CO. Molten carbonate and solidoxide fuel cells internally reforming and developmental forgasification systems.

Gasification Constraints

• Generates carbonaceous solid (char)– Low grade carbon, can be activated to improve value.– Dual-reactor and similar systems burn char to provide additional

heat to process (e.g. FERCO dual fluidized bed tested inVermont).

• Individual reactors limited in scale, multi-reactor systemsneeded for large power or refinery systems

• Advanced IGCC systems using pressurized reactorsneed pressure feeding systems

• For lower tar reactors, moisture content limited (<30%),requires feedstock drying for wet manure solids.

• Particle size distribution important for proper fuelhandling and material flow

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Manure Composition

Fresh cattle manure

Concentrations vary depending on feed, management, age of manure,collection technique.

Ash 15.9 C 45.40 SiO 2 49.12

Volatiles 70.3 H 5.35 Al2O3 10.91

Fixed Carbon 13.8 O 31.00 TiO2 0.42

Total 100.0 N 0.96 Fe2O3 3.64

S 0.29 CaO 14.24

Cl 1.16 MgO 3.18

Total (with ash): 100.00 Na2O 4.26

K2O 6.4

P2O5 3.12

SO 3 2.06

Total 97.35

Undetermined 2.65

Proximate Analysis Ultimate Analysis Ash Analysis

Fate of N, S, Cl in gasification

• Fuel N principally converted to NH3 and N2– 20 to 70% conversion to NH3

– Concentrations from 600 to 6,000 ppmv depending on fuel N– HCN, other species present at lower concentrations– Need to remove to avoid high NOx emissions during gas

combustion– At sufficiently low NH3 concentrations, gas can be used in

reburning applications to reduce NOx from solid-fuel directcombustion systems

– Options to produce ammonia as gasification product

• Fuel S principally converted to H2S, can be scrubbed.• Fuel Cl mostly evolved as HCl, can interfere with sulfur

removal (e.g. reaction with zinc and iron basedsorbents).

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Gasifier Applications

Close-coupled Gasification• Gasifier to supply fuel

gas to solid fueled boiler

• Gasifier operates atlower temperatures/lower volatilization ofalkali, lower fouling

• Potential for loweremissions

• Reburning/Stagedcombustion /NOx

Boiler

Gasifier

Fuel

Fuel

Gas

Char

Ash

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Source: NREL

Thermochemical Processing/Conversion

MeOH

BIOMASSBIOMASS

Cofiring/

Reburn

Combined

Cycle

Cat: Ni/Mg

Cat: Mixed Bases

Na, Ca

CaCN

Cat: Cu-ZnO Cat: Zeolite

HYDROGEN

ETHANOL,

MIXED ALCOHOLS

METHANOL, DME

OLEFINS

FTL

LPG

NAPHTHA

KEROSENE/DIESEL

LUBES

WAXES

GASOLINE

OXOCHEMICALS

e.g., KETONES

AMMONIA

SNG

CHP

CHP

SYNGAS

FEED PREP

GASIFICATION

CLEANUP

Cat = Catalytic

Conversion Process

Cat: Ni, Fe,

Cu-Zn

Cat: Ni

Cat: Cu-Zn,

Cu-Co

Cat: Cu-ZnO

Cat: H3PO4,

Cr2O3

Cat: Fe

Cat: Co/K

UPGRADE

SELECTED SYNTHESIS GAS OPTIONSSELECTED SYNTHESIS GAS OPTIONS

FEEDSTOCK

+ Others

Gasifier—Boiler Application

CONDENSATE

option

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CFB with gas

conditioning—Engine Gensets(Carbona Skive Project, Denmark)

GASIFIER

PRODUCT GAS FILTER

GAS COOLER

PRODUCT GAS COOLING(Heat Recovery)

GAS ENGINES

TAR CRACKER

BIOMASS

AIR

ASH

FLY ASH

BOILER

TO STACK

WATER TREATMENT

PRODUCT GAS SCRUBBING

(Heat Recovery)

PRODUCT GAS

BUFFER TANK

STEAM

DISTRICT

HEATING

11.5 MWth

FLUE GASHEAT RECOVERY

POWER

5.4 MWe

Cyclone

Separator

Bed media

and char return

Courtesy Carbona Corporation

BIGCC Power Generation

3 MWe and up

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BTL: Biomass To Liquids

Pretreatment

•Drying

•Comminution

•Extraction

Gasification

Gas Cleaning

•Wet/Cold

•Dry/Hot

Gas Processing

•Methane ReformingCH4+ H2O = 3H2 + CO

•Shift

H2/CO adjust

•CO2 removal

FT Synthesis

Power

Generation

Recycle

Liquid/Wax Products

Off-gas

PowerBiomass

Fischer-Tropsch Synthesis

CO + 2H2 = -(CH2)- + H2O

H500K = - 165 kJ/mol

225-365°C/0.5-4 MPa

CO2 + 3H2 = -(CH2)- + 2H2O

H500K = - 125 kJ/mol

(Kölbel reaction)

Fe, Co

Refining

Heat/Steam

Products

(80 gals/ton)

Ash, Char

Water, Tar, PM

Air/O2

=33-50% LHV Overall

Biomass To Hydrogen: Gasification

Pretreatment

•Drying

•Comminution

•Extraction

Gasification

Gas Cleaning

•Wet/Cold

•Dry/Hot

Reformer

CH4+ H2O = 3H2 + CO

Water Gas ShiftH2O + CO =H2 + CO2

PowerGeneration/

Carbon Captureand Storage

Power

Biomass

(can also use bio-oil throughsteam reforming)

Gas Purification HydrogenAsh, Char

Water, Tar, PM

Air/O2

Heat/Steam

=52-61% LHV Overall

(Methanol production)

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0.00

0.02

0.04

0.06

0.08

0.10

0.12

0 1000 2000 3000 4000 5000

Installed Capital Cost ($/kW)

CO

E (

$/k

Wh

)

Efficiency = 10%

30%40%

Zero fuel cost

20%

5%

Fuel cost = $20/ton except as noted

Biomass Power—Levelized cost of

electricity (COE)/solid-fuel thermal systems

• Benchmark comparisonfor California: Naturalgas combined cyclewith heat rate of 7,000Btu/kWh (49%efficiency)—at$9/MMBtu gas priceCOE=$0.074/kWh (fuelcost = $0.063/kWh or85% of COE)

• Current natural gasprice $10-13/MMBtu

Levelized Cost of Energy: Sensitivity to Economic

Factors/solid-fuel thermal systems without CHP

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

-200 -100 0 100 200 300

Relati e Change (%)

CO

E (

$/kW

h,

Con

sta

nt)

Capital Cost

Fuel Cost

Debt Ratio

Debt Interest Rate

Cost of Equity

Net Efficiency

Capacity Factor

Sensitivity of COE (2004 constant $/kWh) to technical andfinancial factors for stand-alone power generation from biomass

One year debt reserveGeneral inflation = 2.1%/yearStraight line depreciation

PTC = $0.009/kWhCapacity payment = $166/kW-yCost of equity = 15%/year

Debt interest = 5%/yearDebt ratio = 75%Fuel cost = $20/ton

Capacity factor = 85%Net Efficiency = 20%Capital cost = $2,800/kWe

Base-case assumptions (20 year life):

Impact of Economic Life:

Base COE =

20 Year: $0.067/kWh

5 Year: $0.124/kWh(no salvage)—smallmodular/portablesystems?

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Cost of Electricity: Biomass

Combined Heat and Power (CHP)

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0 2 4 6 8 10 12 14 16

Value of Heat ($/MMBtu)

CO

E (

co

nsta

nt

$/

kW

h)

Current California NaturalGas Price Range (12/2005)

• CHP providesopportunitiesfor low costpower