Black Liquor Gasification Combined Cycles: Mill Integration Issues, Performance and Emissions Estimates Stefano Consonni* § , Eric D. Larson § , Ryan E. Katofsky ‡ * Politecnico di Milano § Princeton University ‡ Navigant Consulting Colloquium on Black Liquor Combustion and Gasification Salt Lake City, May 13-16, 2003 Pulp & Paper industry has the infrastructure, the experience and the expertise to handle large quantities of woody biomass Gasification can very substantially increase the efficiency of energy recovery from biomass → P&P industry can become net exporter of electricity and/or bio-fuels In the next decade, the industry will face the need to replace or refurbish a significant fraction of its recovery boiler fleet Most of the US P&P capacity is concentrated in the South-East DOE, a number of paper companies through AFPA and two utilities (Southern Company and TVA) have sponsored a case study to assess the potential of Black Liquor Gasification Combined Cycles (BLGCC) in term of energy, environmental and economic benefits Background
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Black Liquor Gasification Combined Cycles: Mill Integration Issues, Performance and
Emissions Estimates
Stefano Consonni*§, Eric D. Larson§, Ryan E. Katofsky‡
* Politecnico di Milano § Princeton University ‡ Navigant Consulting
Colloquium on Black Liquor Combustion and GasificationSalt Lake City, May 13-16, 2003
Pulp & Paper industry has the infrastructure, the experience and the expertise to handle large quantities of woody biomassGasification can very substantially increase the efficiency of energy recovery from biomass → P&P industry can become net exporter of electricity and/or bio-fuelsIn the next decade, the industry will face the need to replace or refurbish a significant fraction of its recovery boiler fleetMost of the US P&P capacity is concentrated in the South-EastDOE, a number of paper companies through AFPA and two utilities (Southern Company and TVA) have sponsored a case study to assess the potential of Black Liquor Gasification Combined Cycles (BLGCC) in term of energy, environmental and economic benefits
Background
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Biomass is a small part of the US primary energy mix (3.2%), butis second only to hydropower among renewable energy sources
1998 Total US Primary Energy Consumption – All Sectors and Sources
Coal and Coke23.0%
Natural Gas23.2%
Petroleum38.8%
Biomass3.2%
Hydro3.8%
Other7.5%
Nuclear7.6%
Wind0.0%
Solar0.1%
Geothermal0.4%
Primary Energy in the US
In the US, 75% of non-hydro renewable power generation is biomass-based, accounting for 1.5% of total power generation.
1. Data reported includes peat, municipal solid waste, landfill gas and tires.Source: DOE/EIA Renewable Energy Annual 1999 (DOE/EIA-0603(99)) and DOE/EIA Electric Power Annual 1998.
1998 US Electricity Generation by Fuel Type
Coal51.6%
Petroleum3.5%
Natural Gas15.3%
Nuclear18.5%
Wind0.1%
Solar0.0%
Geothermal0.4%
Biomass1.5%
Hydro8.9%
OtherRenew.
2.1%
Other0.1%
Total = 3,634 billion kWh
Total = 74.7 billion kWh(Biomass1 = 55.8 billion kWh)
Non-Hydro Renewables
Mostly in thepulp & paperindustry.
Electricity Production in the US
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Recovery Boilers built in North America by year
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18
20
1938
1947
1949
1951
1953
1955
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1959
1961
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1965
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1969
1971
1973
1975
1977
1979
1981
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1985
1987
1989
1991
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1995
1997
START-UPS RE-BUILDS
Pulp & Paper in the US South
Southeast ~ 80 Kraft mills
United States ~ 120 Mills
Kraft mills served by SoCoMajor natural gas pipelines
Sources:
Pulp mills: 2001 Lockwood-Post’s Directory of the Pulp, Paper and Allied Trades.
Major gas pipelines: Penwell Mapsearch. (LA, MO, OK TX, TN, VA pipelines are not shown)
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Pulp & Paper in the US SouthEstimates of International Institute for Environment and Development, 1996
Black liquor is injected at the top of a pressurized (or atmospheric) vessel together with oxygen (or air)Mixture flows downdraft and by reacting ~adiabatically it reaches ~1000°C. Then the gas+smelt flow enters a lower chamber where it is quenched with re-circulated waterSmelt falls in water at the bottom of the quench chamber, thereby generating green liquorRaw gas at ~220°C (temperature depends on pressure) exits laterally toward an MP boiler
High-temperature, directly-heated Gasifieroxygen-blown design with sulfur removal unit
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Black liquor and air are fed to a fluidized bed maintained below the smelting temperature (~700°C)Raw gas exits from the top of the reactor while solid phase is extracted at the bottom of the bedMild pressurization (~2 bar)
Heat required to reach gasification temperature is provided by an external heat source: pulse combustor fed with product gasRather than partial combustion, gasifier carries out a steam reforming reaction (quite endothermic) which generates an hydrogen-rich syngasReforming takes places in a bed fluidized with steam (if needed,also with recycle gas) and maintained below the smelting temperature by adjusting the heat provided by the external heat sourceProduct gas exits from the top of the reactor while solid phase is extracted at the bottom of the bed
Direct vs indirectly-heated Gasifier
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Indirectly-heated Gasifier
Sulfur recovery. S capture from syngas requires:absorption system ( → steam consumption)Claus furnace + SCOT unit ( → steam cons/generation)
Increase of lime kiln loadHigher complexity and tighter integration of steam cycle among:
gasificationsyngas clean-up → chemicals recovery, remove alkali and tarpower islandmill
Reliability of integrated system
Integration issues
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Hypothetical mill defined to assess the potential benefits of BLG:integrated pulp and uncoated freesheet paper mill1725 machine-dry metric tons paper/daynominal 6 MM lbs/day dry solids 65% hardwood/35% softwoodelectricity consumption 1500 kWh/mt papersteam consumption 10.6 GJ/mt of paper (~10% decrease with respect to current US best practice)
Gasification comes together with polysulfide pulping → yield increases by 3.25 percentage points → for the same paper production, Black Liquor Solids (BLS) flow decreases to 5.42 MM lb/dayTwo gasification technologies: High-T, oxygen-blown and Low-T, indirectly-heat reformerTwo sizes: “Mill Scale” and “Utility-Scale”Hog fuel still used in existing power boilers (no biomass gasification)
Case Study
Current Black Liquor Capacity in the US Pulp Industry
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Individual Mills
Bla
ck L
iquo
r Cap
acity
MM
bls
/day
(app
roxi
mat
e)
0%
20%
40%
60%
80%
100%
120%%
of t
otal
cap
acity
> MM lbs/day bls % of total USA capacity 4.0 65% 4.5 59% 5.0 53% 5.5 41% 6.0 32% 6.5 28% 7.0 26%
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Model Power output
Heat RateBtu/kWh kJ/kWh
GE Heavy-duty gas turbinesGas Turbine
GE Frame 6 FA for Mill Scale
GE Frame 7 FA for Utility Scale
When running on syngas, let pressure ratio increase up to 5%, then reduce air flow
Technological Competiton
Compare performances (and costs) of gasification-based systems with
In both cases, extra-hog fuel made available by decrease in mill steam consumption is burnt in existing power boilers to generate extra-steamSteam turbine includes a condensing section to take maximum advantage of the extra-steam
Wood to process (91% of total) 3,208Hog fuel (9% of total) 317
3,525bd kg/day 3,197,860
pine 48.75%hardwood 49.75%
Solids concentration in BL % mass 80 85 80BLS flow lbBLS per day 6,000,000 6,000,000 5,419,646
kJ per kg of BLS 13,892 13,892 13,874Btu per lb of BLS 5,974 5,974 5,966
Composition of BLS C % mass 33.46% 33.46% 32.97% H % mass 3.75% 3.75% 3.70% O % mass 37.35% 37.35% 36.88% S % mass 4.10% 4.10% 4.27% Na % mass 19.27% 19.27% 20.03% K % mass 1.86% 1.86% 1.93% Ashes/Clorides % mass 0.21% 0.21% 0.22%
MJ / mt of paper 7,149 7,100 6,774LP steam from Sulfur Recovery Unit kg/kg of H2S captured 0.0 0.0 1.80IP (80 psig) steam to SRU kg/kg of H2S captured 0.0 0.0 10.00
kg / kg BLS 1.12 1.15 1.16MJ / mt of paper 3,469 3,581 3,247
MP steam from Sulfur Recovery Unit kg/kg of H2S captured 0.0 0.0 3.30kWh / mt of paper 1,500 1,500
kW 107,836 107,836
1.14
Tomlinson
LP (55 psig) steam to paper machine 3600
kg per kg of BLS
LP steam to pulp+paper mill
MP steam to pulp mill
varies withgasificationtechnology
Parameter unit
Electricity consumption
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Base HERB Low-T High-Tmedium
High-Tlarge
Wood used bone dry kg/s 39.63 39.63 37.01 37.01 37.01DS flow kg/s 31.50 31.50 28.45 28.45 28.45T of black liquor °C 115 115 115 115 115Gasif. Heat loss to environment % of BL HHV - - 1.0 0.5 0.5Heat to cooling screens % of BL HHV - - - 2.0 2.0Carbon conversion % - - 98.5 99.9 99.9Methane in raw syngas % vol in dry raw gas - - 2.8 1.5 1.5T solids/green liquor from gasifie °C - - 250 120 120Tars in raw syngas of input C as phenol - - 1.50 - -T pulse combustor flue gases °C - - 662 - -O2 pulse combustor flue gases % vol wet - - 2.5 - -Fluidization steam kg/kgDS - - 0.25 - -Purge steam kg/kgDS - - 0.01 - -CO2 captured by S-removal CO2/H2S, molar - - 2.00 2.00 2.00T pre-heated air recovery boiler °C 165 220 - - -T flue gases recovery boiler °C 170 130 - - -O2 in flue gases, wet basis % 2.0 1.0 - - -HP steam pressure psig (bar_abs) 1250 (87.2) 1500 (104.5) 1870 (130) 1870 (130) 1870 (130)HP steam temperature °C 480 520 540 540 565Blowdown % of flow to HP ST 1.4 1.3 1.0 1.4 1.2
Emission reductions for the whole US industryAggressive Scenario
~100% market penetration by 2035P&P industry growth 1% per yearincrease in efficiency of energy use compensates industry growth (total energy use is fixed → electricity exports increase)average US emissions from DOE forecastsevaluate NET reductions with respect to Tomlinson, 2008
Net Reduction metric tons over period 2008-2035
CO2 624,774,878SO2 2,739,265NOx 959,697CO 688,958VOC 120,857PM 475,581CH4 9,519TRS 31,149
High T Utility Scale
BLGCCs can increase very significantly the efficiency of energy recovery from biomass in the P&P industryWith BLGCC, P&P industry can become a large exporter of (mostly renewable) electricityThe higher energy efficiency of BLGCC comes together with large reductions of emissionsMill Integration issues are significant but don’t seem to be subject to technical gaps. Main impact is on costs.Sulfur recovery and variation of kiln load are crucial to improve performances (and limit costs)Further increases in efficiency of renewable energy use can be expected by coupling BLGCC with biomass gasificationEconomic assessment is underway
Conclusions
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AcknowledgementsBob Gemmer (DOE)John Huyck (Mead-WestVaco)Del Raymond, Denny Hunter, Craig Brown (Weyerhaeuser)Paul Tucker (International Paper)Ben Thorp and Karl Morency (Georgia Pacific)Richard Campbell (AFPA)Tom Johnson (Southern Company)Martha Rollins and Les Reardon (TVA)Gerard Closet (consultant)Ried Miner (NCASI)Shawna McQueen (Energetics)Elmer Fleischman (Idaho National Energy Lab)Bo Oscarsson and John Lewis (Fluor)Sam Tam and King Ng (Nexant)Jarmo Kaila and Tervo Olavi (Andritz)Scott Sinquefield (IPST)Adriaan van Heinenengen (Univ. Of Maine)Hassan Jameel (U. of North Carolina)Ingvar Landalv (Chemrec)
Lee Rockvam & Ravi Chandran (ThermoChem)Niklas Berglin (STFI)Jim Frederick (Chalmers Univ.)Michael Ryan (consultant)Dale Simbeck (SFA Pacific)Nathanael Greene (NRDC)Jim WolfMichael Farmer (Georgia Inst. of Tech.)
DOE, AFPA, Southern Company, TVA for financial support