Black Liquor Gasification Combined Cycles: Mill Integration Issues, Performance and Emissions Estimates

Transcription

1 Colloquium on Black Liquor Combustion and Gasification Salt Lake City, May 13-16, 2003 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

2 Background 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

3 Primary Energy in the US Biomass is a small part of the US primary energy mix (3.2%), but is second only to hydropower among renewable energy sources 1998 Total US Primary Energy Consumption All Sectors and Sources Petroleum 38.8% Nuclear 7.6% Other 7.5% Solar 0.1% Wind 0.0% Geothermal 0.4% Biomass 3.2% Hydro 3.8% Na tural Gas 23.2% Coal and Coke 23.0%

4 Electricity Production in the US In the US, 75% of non-hydro renewable power generation is biomass-based, accounting for 1.5% of total power generation US Electricity Generation by Fuel Type Natural Gas 15.3% Nuclear 18.5% Other 0.1% Wind 0.1% Solar 0.0% Pe troleum 3.5% Hydro 8.9% Geothermal 0.4% Other Renew. 2.1% Biomass 1.5% Non-Hydro Renewables Mostly in the pulp & paper industry. Coal 51.6% Total = 3,634 billion kwh Total = 74.7 billion kwh (Biomass 1 = 55.8 billion kwh) 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.

5 Recovery Boilers built in North America by year START-UPS RE-BUILDS

6 Pulp & Paper in the US South Southeast ~ 80 Kraft mills United States ~ 120 Mills Kraft mills served by SoCo Major 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)

7 Pulp & Paper in the US South Estimates of International Institute for Environment and Development, 1996

8 Black Liquor Gasification High-Temperature (smelt phase), directly heated Medium-Temperature (solid phase) directly heated Low-Temperature (solid phase) indirectly heated

9 High-temperature, directly-heated Gasifier 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 water Smelt falls in water at the bottom of the quench chamber, thereby generating green liquor Raw gas at ~220 C (temperature depends on pressure) exits laterally toward an MP boiler

10 High-temperature, directly-heated Gasifier oxygen-blown design with sulfur removal unit

11 Medium-temperature, directly-heated Gasifier air-blown design 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 bed Mild pressurization (~2 bar)

12 Medium-temperature, directly-heated Gasifier air-blown design

13 Low-temperature, indirectly-heated Gasifier Heat required to reach gasification temperature is provided by an external heat source: pulse combustor fed with product gas Rather than partial combustion, gasifier carries out a steam reforming reaction (quite endothermic) which generates an hydrogen-rich syngas Reforming 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 source Product gas exits from the top of the reactor while solid phase is extracted at the bottom of the bed

14 Direct vs indirectly-heated Gasifier

15 Indirectly-heated Gasifier

16 Sulfur recovery. S capture from syngas requires: absorption system ( steam consumption) Claus furnace + SCOT unit ( steam cons/generation) Increase of lime kiln load Integration issues Higher complexity and tighter integration of steam cycle among: gasification syngas clean-up chemicals recovery, remove alkali and tar power island mill Reliability of integrated system

17 Case Study Hypothetical mill defined to assess the potential benefits of BLG: integrated pulp and uncoated freesheet paper mill 1725 machine-dry metric tons paper/day nominal 6 MM lbs/day dry solids 65% hardwood/35% softwood electricity consumption 1500 kwh/mt paper steam 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/day Two gasification technologies: High-T, oxygen-blown and Low-T, indirectly-heat reformer Two sizes: Mill Scale and Utility-Scale Hog fuel still used in existing power boilers (no biomass gasification)

18 Black Liquor Capacity MM bls/day (approximate) Current Black Liquor Capacity in the US Pulp Industry > MM lbs/day bls % of total USA capacity % % % % % % % 120% 100% 80% 60% 40% 20% % of total capacity 0 Individual Mills 0%

19 Gas Turbine Model GE Heavy-duty gas turbines Power output Heat Rate Btu/kWh kj/kwh 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

20 Technological Competiton Compare performances (and costs) of gasification-based systems with conventional Tomlinson recovery boiler High Efficiency Recovery Boilers (HERB) In both cases, extra-hog fuel made available by decrease in mill steam consumption is burnt in existing power boilers to generate extra-steam Steam turbine includes a condensing section to take maximum advantage of the extra-steam

21 Assumptions: production and yield Tomlinson Gasification Parameter unit conventnl HERB polysulph. 80% BLS 85% BLS 80% BLS Product flow (paper) machine dry mtons/day 1,725 Unbleached pulp rate bd short tons/day 1,580 Wood mix 65% HW, 35% SW Wood to process (91% of total) 3,434 3,208 Hog fuel (9% of total) bd short tons/day Total wood used Yield pine 3, % 3, % bd kg/day hardwood 3,423, % 3,197, % Solids concentration in BL % mass BLS flow lbbls per day 6,000,000 6,000,000 5,419,646 HHV of BLS kj per kg of BLS 13,892 13,892 13,874 Btu 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%

22 Steam and electricity consumption Tomlinson Gasification Parameter unit conventnl HERB polysulph. 80% BLS 85% BLS 80% BLS lb per st of paper 3600 LP (55 psig) steam to paper machine 1.14 LP (55 psig) steam to pulp mill kg per kg of BLS LP steam to pulp+paper mill MJ / mt of paper 7,149 7,100 6,774 LP steam from Sulfur Recovery Unit kg/kg of H2S captured IP (80 psig) steam to SRU kg/kg of H2S captured kg / kg BLS MP steam to pulp mill MJ / mt of paper 3,469 3,581 3,247 MP steam from Sulfur Recovery Unit kg/kg of H2S captured Electricity consumption kwh / mt of paper 1,500 1,500 kw 107, ,836 varies with gasification technology

23 Gasifier and Power Plant Base HERB Low-T High-T medium High-T large Wood used bone dry kg/s DS flow kg/s T of black liquor C Gasif. Heat loss to environment % of BL HHV Heat to cooling screens % of BL HHV Carbon conversion % Methane in raw syngas % vol in dry raw gas T solids/green liquor from gasifie C Tars in raw syngas of input C as phenol T pulse combustor flue gases C O2 pulse combustor flue gases % vol wet Fluidization steam kg/kgds Purge steam kg/kgds CO2 captured by S-removal CO2/H2S, molar T pre-heated air recovery boiler C T flue gases recovery boiler C O2 in flue gases, wet basis % HP steam pressure psig (bar_abs) 1250 (87.2) 1500 (104.5) 1870 (130) 1870 (130) 1870 (130) HP steam temperature C Blowdown % of flow to HP ST Sootblowing steam Bark input (50% moisture) Hog fuel boiler HP steam Tomlinson Gasification bar % of RB HP steam kg/s MW LHV psig (bar_abs) 1250 (87.2) 1250 (87.2) 1250 (87.2) 1250 (87.2) 1250 (87.2) C T pre-heated air hog fuel boiler C T flue gases hog fuel boiler C O2 in flue gases % wet Kiln consumption MJ / mt of lime MJ / mt DS

24 Heat and Mass Balances Code developed at Politecnico di Milano and Princeton to predict the performances of power cycles, including: chemical reactions ( gasification, steam reforming) heat/mass transfer ( saturation) some distillation process ( cryogenic Air Separation) Model accounts in detail for most relevant factors affecting cycle performance: scale gas turbine cooling turbomachinery similarity parameters chemical conversion efficiencies Accuracy of performance estimates has been verified for a number of state-of-the-art technologies

25 Base Tomlison Case return from mill + makeup (110 C) air to stack Deaerator (4.8 bar) Gas cleanup Air heater 480 C Gross electricity out = MWe Net electriciy out = MWe Mill steam = MWth Power boiler bark (HHV) = 71.2 MWth Nat. gas (HHV) = 0 Black liquor (HHV) = MWth Biomass boiler ash Temp., C Pres., bar Flow, kg/s black liquor (80% ds) hog fuel (50% moisture) HP steam from power boiler Tomlinson boiler smelt soot-blowing steam 480 C Steam turbine MP Air Heater Drum (87.2 bar) blow down feedwater to power boiler Flue gas clean-up MWe ~ LP Air Heater LP fw heater Deaerator (4.8 bar) blwdwn flash de-sh air return from mill + makeup (110 C) To stack bar steam to mill 13-bar steam to mill Condenser (30.88 MWth)

26 High Efficiency Recovery Boiler (HERB) black liquor (85% ds) MP+ Air Heater MP Air 120 Heater Drum (103.5 bar) blow down LP Air Heater Deaerator (4.8 bar) air Temp., C Pres., bar Flow, kg/s Gross electricity out = MWe Net electricity out = MWe Mill steam = MWth Power boiler bark (HHV) = 71.2 MWth Nat. gas (HHV) = 0 Black liquor (HHV) = MWth Tomlinson boiler steam for soot-blowing and MP+ air heater steam from power boiler (Pev=87.22 bar, Tsh= 480 C, hog fuel = 7.12 kg/s) 520 C smelt Steam turbine HP fw heater Flue gas clean-up To stack from LP fw heater + make-up blowdown flash MWe ~ de-sh 4.8-bar steam to mill Condenser (35.97 MWth) bar steam to mill LP fw heater feedwater to economizer

27 High-T Gasifier, Mill Scale stripper Temp., C Pres., bar Flow, kg/s MWe ~ air MWe Gross electricity out = MWe Net electricity out = MWe Mill steam = MWth Power boiler bark (HHV) = MWth Nat. gas (HHV) = MWth Black liquor (HHV) = MWth vent Oxygen plant Gas turbine air % O green liquor Duct burner Black liquor (80% ds) Gasifier 1000 C 35 bar Quench cooler natural gas steam from power boiler (Pev=87.22 bar, Tsh= 480 C, hog fuel = kg/s) from saturator raw 35.0 gas condensate humidified syngas Steam turbine ~ boiler to stack HRSG Pev=130 bar, Tsh= 540 C (blow-down 1.14 kg/s fromhp drumnot shown) MWe water heater ST leakage IP steam to sulfur recovery from mill + from saturator + make-up Remove alkali Saturator de-sh 0.79 MP steam to mill trim cooler condensate to gasif. island and power boiler make-up tank MP steam absorber make-up clean syngas Selexol system H 2 S + CO 2 Claus + SCOT plant reboiler LP steam from blowdown flash tank to deaerator * 1.2* 2.45* to mill

28 Temp., C Pres., bar Flow, kg/s MWe ~ High-T Gasifier, Utility Scale MWe Gross electricity out = MWe Net electricity out = MWe Mill steam = MWth Power boiler bark (HHV) = 66.6 MWth Nat. gas (HHV) = MWth Black liquor (HHV) = MWth vent Oxygen plant Black liquor (80% ds) Gasifier 1000 C 35 bar steam from power boiler (Pev=87.22 bar, Tsh= 480 C, hog fuel = 6.66 kg/s) condensate from mill raw gas Quench cooler natural gas air condensate green liquor humidified syngas air Gas turbine % O Steam turbine to stack Pev=130/13 bar, Tsh= 565/200 C (blow-down 1.14 kg/s from HP drum not shown) HRSG boiler ~ MWe LP steam water heater condensate + make-up de-sh IP steam to SRU Saturator MP steam to mill trim cooler MP steam Condenser (46.07 MWth) condensate to gasif. island and power boiler make-up tank make-up absorber clean syngas Selexol system H 2 S + CO 2 reboiler Claus + SCOT plant de-sh stripper to deaerator from blowdown flash tank * 1.2* 2.45 MP steam to mill LP steam to mill

29 Low-T Gasifier, Mill Scale Gross electricity out = MWe Net electricity out = MWe Mill steam = MWth Power boiler fuel (HHV) = MWth Nat. gas (HHV) = 60.9 MWth Black liquor (HHV) = MWth Black liquor (80% ds) MP water MWe ~ air solids Gasifier 600 C 2.7 bar Gas turbine fan syngas heater Temp., C Pres., bar Flow, kg/s air raw syngas combustor cooling pulse combustor syngas kg/s purge steam syngas expander ~ MWe HP boiler excess syngas to duct burner Remove tar and alkali LP boiler return from mill + make-up Scrubber 540 to stack gasification return from steam mill + make-up HRSG - Pev=130 bar, Tsh= 540 C (blow-down 1.14 kg/s from HP drum) Duct to deaerator burner MWe Steam Turbine ~ from SRU excess nat. gas steam from power boiler syngas (Pev=87.22 bar, Tsh= 480 C, ST leakage hog fuel = 10.0 kg/s) to HP fw heaters water + tar M MWe water Claus + SCOT plant from blowdown de-sh de-sh H 2 S + CO 2 condensate to deaerator clean syngas * 1.2* 4.35 MP steam to mill LP steam to mill

30 Results: gas turbine and aux. fuel input Low-T Gasification High-T medium High-T large Air flow to GT kg/s syngas flow to GT kg/s total fuel flow to GT kg/s Ar % mol CH4 % mol CO % mol CO2 % mol COS % mol H2 % mol H2O % mol N2 % mol Total % mol HHV syngas MJ/kg Syngas power to GT kw HHV 249, , ,634 Syngas to pulse combustor kw HHV 132, Syngas to duct burner kw HHV 23,794 14,443 - Natural gas flow to GT kw HHV ,064 Natural gas to duct burner kw HHV 60,857 14,319 0 Hog fuel to power boilers kw HHV 100, ,000 66,622 Res fuel oil to lime kiln kw HHV 50,447 42,311 42,311

31 Results: power production and efficiency Tomlinson Base HERB Low-T Gasification High-T medium High-T large GT gross power output kwel ,910 86, ,840 ST gross power output kwel 71,990 96,472 65,109 48,163 71,536 Syngas expander power ouptut kwel - - 5, TOTAL GROSS PRODUCTION kwel 71,990 96, , , ,376 ASU power consumption kwel ,690 13,690 Syngas compressor power cons. kwel , Aux. for steam cycle/hrsg kwel - - 1,915 1,194 2,574 Aux. for Tomlinson/gasifier island kwel 6,690 6,804 2,667 2,667 2,667 Aux. for Sulfur Recovery kwel - - 2,063 1,058 1,058 Aux. for steam cycle/power boiler kwel 1,050 1,050 1,244 1,244 1,016 TOTAL UTILITIES kwel 7,740 7,854 26,600 19,853 21,005 NET electric power output kwel 64,250 88, , , ,371 Mill electricity consumption kwel 100, , , , ,096 Power exportable to grid kwel -35,846-11,477 20,327 15, ,276 Total nat gas flow kw, HHV ,857 14, ,956 Hog fuel input kw, HHV 71,189 71, , ,000 66,622 Res fuel oil to lime kiln kw HHV 36,032 36,032 50,447 42,311 42,311 Margnal efficiency with respect to Base % - infinite

32 Variations with respect to Base Tomlinson 300 Extra Consumption / Generation, MW HHV HERB Extra Electricity Natural Gas Import Hog Fuel Import Extra Kiln Fuel Low T 51.7% marginal efficiency 94.6% High T medium 60.2% High T large

33 Results: emissions Total Point Source Combustion Emissions metric tons per year Tomlinson Cases BLGCC Cases Base HERB Low T Mill Scale High T Mill Scale High T Large CO2 84,038 84, , , ,243 SO NOx 2,472 2,472 2,819 2,439 2,648 CO 1,096 1,096 1, VOC PM Grid Power Emissions Offsets Relative to "Base" metric tons per year Tomlinson Cases BLGCC Cases Base HERB Low T Mill Scale High T Mill Scale High T Large CO2-121, , , ,855 SO , ,962 NOx ,201 CO VOC PM

34 Results: net emissions for 6 MM lb/d Mill Net Emissions of each option metric tons per year Tomlinson Cases BLGCC Cases Base HERB Low T Mill Scale High T Mill Scale High T Large CO2 84,038 (37,689) (67,561) (124,260) (306,611) SO2 199 (246) (907) (810) (2,867) NOx 2,472 2,291 2,403 2,061 1,447 CO 1,096 1, VOC PM

35 Emission reductions for the whole US industry Aggressive Scenario ~100% market penetration by 2035 P&P industry growth 1% per year increase in efficiency of energy use compensates industry growth (total energy use is fixed electricity exports increase) average US emissions from DOE forecasts evaluate NET reductions with respect to Tomlinson, 2008 Net Reduction metric tons over period High T Utility Scale CO2 624,774,878 SO2 2,739,265 NOx 959,697 CO 688,958 VOC 120,857 PM 475,581 CH4 9,519 TRS 31,149

36 Conclusions BLGCCs can increase very significantly the efficiency of energy recovery from biomass in the P&P industry With BLGCC, P&P industry can become a large exporter of (mostly renewable) electricity The higher energy efficiency of BLGCC comes together with large reductions of emissions Mill 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 gasification Economic assessment is underway

37 Acknowledgements Bob Gemmer (DOE) Lee Rockvam & Ravi Chandran (ThermoChem) John Huyck (Mead-WestVaco) Niklas Berglin (STFI) 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) Jim Frederick (Chalmers Univ.) Michael Ryan (consultant) Dale Simbeck (SFA Pacific) Nathanael Greene (NRDC) Jim Wolf Michael Farmer (Georgia Inst. of Tech.) Gerard Closet (consultant) Ried Miner (NCASI) Shawna McQueen (Energetics) DOE, AFPA, Southern Company, TVA for financial support 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)