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

2. 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

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

4. 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

5. 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

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

7. 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: (accessed on )
[2] 2016 Annual report of National Transmission Operator SEPS, a.s., available online at: (accessed on )
[3] 2014 Annual report of Slovenské elektrárne, a.s., available online at: (accessed on ).
[4] 2015 Annual report of Slovenské elektrárne, a.s., available online at: (accessed on ).
[5] 2016 Annual report of Slovenské elektrárne, a.s., available online at: (accessed on ).

8. 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

9. 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

10. 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
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 %)

11. 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 /
11 712 /
-13 748 / 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

12. 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

13. 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)

14. 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

15. Thank Your for Your kind attention!