Miroslav Variny, Michal Hruška, Otto Mierka Energetic and environmental evaluation of two black liquor processing technologies Miroslav Variny, Michal Hruška, Otto Mierka

Presentation overview Chemicals recovery in Kraft process → Kraft boilers & their integration in P&P mill → Black liquor gasification – an alternative under R&D Calculation model Aims of the works, study objectives Results and their interpretation Conclusions

Kraft process, chemicals recovery Majority of pulp & paper produced by Kraft process Wood chips cooking in cooking liqour Chemicals recovery

Recovery boiler – traditional well proven technology Black liqour combustion, steam and electric energy cogeneration Integrated in the P&P mill energy production system Moderate power to heat ratio Excess steam for EE production by condensing turbine Modern high efficiency boilers: steam T ↑, p ↑ Carnotization (air and BFW) flue gas coolers capacities up to 1000 t/h steam

Black liquor gasifier – novel promising technology Pressurized process; uses air or oxygen Syngas cleanup; fuel for gas turbine and/or elsewhere in the P&P mill (f.e. lime kiln) Integration in the P&P mill energy production system crucial for efficient operation Syngas is potential starting point for production of biofuels

Black liquor gasifier integration (IGCC) Possible gas extraction as lime kiln fuel gas

Emissions from EE production in Slovakia Year Delivered power to grid from SE, GWh [1,2] Brutto annual power consumption in Slovakia, GWh [1,2] Share of SE on brutto consumption, % 2014 20215 28355 71,3 2015 17892 29579 60,5 2016 17242 30103 57,3 Year Specific emissions from EE produced by SE, a.s. delivered to grid [3-5] CO2, t/GWh CO, kg/GWh SOx,kg/GWh NOx, kg/GWh TZL, kg/GWh 2014 121 34,97 1244,2 166,86 15,48 2015 142 39,57 2641,7 217,14 29,79 2016 134 66,35 370,8 109,44 9,80 Marginal fossil fuel fired source 900 110 500 650 18 Considered emissions from regeneration boilers and IGCC Regeneration boilers (8 % vol. O2): NOx 50 ppmv, SOx 5 ppmv, TZL 37 mg/m3 IGCC: NOx 50 ppmv (conservative estimate) CO2 emissions from fuel conversion considered the same in both cases [1] Official webpage of governmental institution Enviroportál: https://www.enviroportal.sk/indicator/detail?id=762 (accessed on 10.01.2018) [2] 2016 Annual report of National Transmission Operator SEPS, a.s., available online at: http://www.sepsas.sk/Dokumenty/Vyrocnespravy/2017/SEPS_VS2016.pdf (accessed on 05.01.2018) [3] 2014 Annual report of Slovenské elektrárne, a.s., available online at: http://2014.seas.sk/public/pdf/enel_annual_report_2014.pdf (accessed on 22.01.2018). [4] 2015 Annual report of Slovenské elektrárne, a.s., available online at: http://2015.seas.sk/public/pdf/se-vs-2015.pdf (accessed on 22.01.2018). [5] 2016 Annual report of Slovenské elektrárne, a.s., available online at: https://www.seas.sk/data/publishing/361/file/se-2016-annual-report.pdf (accessed on 22.01.2018).

Aims of our work Comparison of these two technologies → definition of comparison base → process schemes setup (as shown) → calculation model setup → net power production estimation with pre-defined mandatory heat production → investment costs (pressurized, oxygen blown gasifier) → difference in emissions release Tentative simple pay back period estimation → incremental value → model energy media costs

Comparison base, calculation model → amount and quality of black liquor processed → mandative amounts of middle and low pressure steam export to the mill Calculation model → syngas composition based on experimental data provided in available literature → material and energy balances, boiler thermal efficiency, turbines efficiencies → own electric energy consumption estimation

Results – comparison I. fuel input: 1600 tDS/day black liquor, 75 % wt. solids, 9 GJ/t LHV Parameter/Studied system CSPP IGCC Total steam production incl. flash steam, t/h 288 144 Internal steam consumption + losses, t/h 92 12 Steam for condensing power production, t/h 83 19 Exported steam LP + MP, t/h 76 + 37 Power produced by gas turbine, MW - 61,1 Power produced by steam turbine, MW 50,0 9,9 Total gross power production, MW 71 Internal power consumption, MW 2,6 11,2 Net power production, MW 47,4 59,8 (= +12,2 MW) Net power production efficiency, % 19,2 24,2 (= + 5 %)

Results – comparison II. *assumed 8400 h/year and 70 MW as the total average power consumption of the paper mill System understudy CSPP IGCC Difference (CSPP – IGCC) Power imported to paper mill, GWh/year* 190 87,4 -102,6 Emissions released by SE mix / by marginal source for power production, t/year CO2 25 460 / 171 000 11 712 / 78 660 -13 748 / - 92 340 CO 12,61 / 20,90 5,80 / 9,62 -6,81 / - 11,28 SOx 70,45 / 95,00 32,41 / 43,7 -38,04 / - 51,3 NOx 20,79 / 123,50 9,56 / 56,81 -11,23 / - 66,69 TZL 1,86 / 3,42 0,86 / 1,57 -1,00 / - 1,85 Emissions released by BL CSPP and by BL IGCC, t/year 45,02 Nearly zero - 45,02 319,2 356,2 + 37

Economic comparison Investment cost estimation (literature data) Is it feasible to install the IGCC technology instead of a modern recovery boiler, when replacing an obsolete one? Investment cost estimation (literature data) → Modern 1600 tDS/day recovery boiler + steam turbine + auxiliaries: appr. 110 mil. € → Pressurized oxygen blown gasifier, CCGT, oxygen production plant, auxiliaries: appr. 190 mil. € → Incremental IGCC investment cost = 190 – 110 = appr. 80 mil. € Net profit Δ EE = 3 to 10 mil. €/year (EE cost) Tentative incremental simple pay back period = 8 to 25 years → most likely not feasible with todays investment costs and EE costs

Further considerations Part of syngas to be used in lime kiln Modifications in the IGCC (humid air turbine, recuperation...) More detailed syngas cleanup system modeling Wider scope of gasifier integration (chemicals production, CO2 separation, H2 separation)

Conclusions Evaluation of traditional vs. emerging black liquor handling technologies Gasification technology yields higher net power production but is more costly and still under development Nearly all considered overall emissions are lower with the gasification technology Incremental simple pay back period exceeds 10 years for present EE prices for a 1600 tDS/day system (middle to large size paper mill) Future system modifications under consideration for profit increase

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