PARTIAL CO 2 CAPTURE TECHNOLOGY OPTIONS IN THE PULP AND PAPER INDUSTRY

Transcription

1 PARTIAL CO 2 CAPTURE TECHNOLOGY OPTIONS IN THE PULP AND PAPER INDUSTRY A case study within the CO 2 stcap Project Marie Anheden 1, Jens Wolf 1, Ragnhild Skagestad 2, Stefanía Ósk Gardarsdóttir 3, Fredrik Normann 3 1 RISE Bioeconomy 2 Tel-Tek 3 Chalmers University of Technology Research Institutes of Sweden RISE BIOECONOMY

2 CO 2 and pulp and paper industry in the Nordics Pulp and paper industry is of large economic importance in the Nordics, especially in Sweden and Finland Sweden: employment > , 9-12% of export Capacity expansions in a number of existing mills are ongoing Characterized by low emissions of fossil CO 2 1-2% of total fossil emissions, < 1 Mt out of total 55 Mt in Sweden (2013) However, large emissions of biogenic CO 2 in large point sources Sweden 22 Mt CO 2 /y in 2007 About 10 mills with emissions of 1-2 Mt/y Finland 17 Mt CO 2 /year mills with emissions from 1-3 Mt/y Opportunity for negative CO 2 emissions through largescale BECCS, to reach national CO 2 emission targets! Teir S. et al., 2010, potential for carbon capture and storage (CCS) in the Nordic region, VTT, Research Notes 2556

3 Pulp & paper Industry and CO 2 emissions The main emissions to air in the pulp and paper industry takes place in the pulp mill Three principally different processes for pulp production mechanical pulping chemical pulping based on either the kraft process (sulphate) or the sulfite process. The dominating process today is kraft pulping The kraft pulp mill can either be a stand-alone plant producing market pulp for export or integrated with a paper mill. Integrated mill: there is less excess of steam, as steam is extracted to supply process steam also for the paper production and more electricity is used to supply the demand from the paper mill. There is then less opportunities to use steam for CO 2 capture. Stand-alone kraft pulp mill selected for the case study in CO 2 StCap

4 The modern Nordic kraft pulp mill Recovery boiler: Combustion of black liquor to recover chemicals and generate process steam Lime kiln: Combustion of biomass to transfer CaCO 3 to CaO Power (bark) boiler: Combustion of by-products (bark) to generate additional process steam and power

5 P&P case study goal: to investigate hypothetical technical and economic potential of full and partial CO 2 capture Total yearly emission of CO 2 : 1.5 Mt Modern Nordic kraft pulp mill (BAT 2010) (hypothetical) Adt/y of pulp 355 days of planned operation, 92% combined availability = 7840 h/y Bark powder as fuel in lime kiln Condensing turbine for electricity generation from excess energy 68 MW exported green electricity Capture plant and Economic assumptions MEA, split flow configuration The capture plant is treated as an extension to the existing plant Rate of return: 7.5 % No of years: 25 (3 year of construction and 22 years in operation). Electricity: 0.03 EUR/kWh Green electricity certificates: EUR/kWh Bark 16 EUR/MWh 5 Cooling water 0,02 EUR/m 3

6 Split flow configuration - MEA CO 2 -lean flue gas Lean cooler Absorber Compressor train Stripper Condenser CO 2 Model constructed in Aspen Plus Rate-based calculations 30 wt% MEA 4 stage compression and pumping of CO 2 to 110 bar Dimensions of main process components derived from simulations Simple rich-solvent split configuration Improved process performance for relatively small increase in complexity compared with standard set-up Flue gas DCC Fan Cross heat Exchanger Heat requirement for CO 2 capture: MJ/kg CO 2, depending on source and capture approach Reboiler 6

7 CO 2 StCap P&P cases Steam to the reboiler is primarily generated through extracting steam at 4,5 bars previously designated for the condensing turbine If additional steam is required, it is generated in a separate bark boiler supplying steam to a back-pressure steam turbine 5 cases with partial and full capture of CO 2 from the recovery boiler and lime kiln (bark boiler handles variations and has a low production of CO 2 and is therefore not included) Case ID CO 2 source Capture approach Source of energy 1a Lime kiln Full from 1 source Existing steam cycle 1c Recovery boiler Max partial Existing steam cycle 3a Recovery boiler Full from 1 source Existing steam cycle + new bark boiler 4a Lime kiln + Recovery boiler Max partial Existing steam cycle 4c Lime kiln + Recovery boiler Full from 2 sources Existing steam cycle + new bark boiler Sub-cases with 1 common or 2 separate absorbers are investigated for case 4a and c 7

8 [MW] [kt/y] Influence on CO 2 and energy balance 80 Net generated power, pulp mill Additional bark consumption Total emitted CO2 Total CO2 captured ,600 1,400 1,200 1, a: Full capture from lime kiln Marginal effect on CO 2 emissions CCU rather than CCS? 1c and 3a: Partial and full capture from Recovery Boiler Max steam extraction kt CO 2 /y, 60% reduction in sold el Full capture results in additional capture of 75 kt/y, 4 MW e at the cost of investment in a 30 MW f bark boiler 4a and 4c: Partial and full capture from lime kiln and recovery boiler Max steam extraction kt CO 2 /y, 61% reduction in sold el Full capture results in capture of additional 200 kt CO 2 /y, 11 MW e at the cost of investment in a 75 MW f bark boiler 8

9 Cost of steam (EUR/MWh reboiler steam) Cost of steam 30 Additional bark boiler Use of only steam extraction to supply reboiler heat demand results in a cost of steam of about 14 EUR/MWh or 8 EUR/t reboiler steam (case 1a, 1c and 4a) Reduced condensing power Case 1a Case 1c Case 3a Case 4a Case 4c Cost of loss of sold power Cost of loss of green certs Cost of bark Cost of investment in bark boiler Bark boiler OPEX (excl bark) Investment in an additional bark boiler increases the cost of steam 22 EUR/MWh or 13 EUR/t steam (3a: full capture RB) 25 EUR/MWh or 15 EUR/t steam (4c: full capture RB+LK) Partial capture to utilise available excess heat from steam to the condensing turbine is most profitable Based on CO 2 capture cost: Break-even for full capture from RB requires 2 EUR/kWhe or 23 EUR/MWf for coat of bark Break-even for full capture from LK+RB requires 1.4 EUR/kWhe or -12 EUR/MWhf for the cost of bark 9

10 EUR/ton CO2 captured Economic results Capture cost ( EUR/t) / captured CO 2 pr year ( kton/year) ,200 1,000 OPEX per ton correlates with the energy requirement for solvent regeneration kton CO2 captured pr year OPEX Bark boiler has a high impact on CAPEX and OPEX ( ref 1c vs. 3a and 4a vs. 4c) Lowest CO 2 capture cost with maximum partial capture (1c and 4a) High investment costs entail high risk CAPEX - 1a 1c 3a 4a 4a-II 4c 4c-II - Capture Parameter Unit Case 1a case 1c Case 3a Case 4a Case 4a-II case 4c Case 4c-II CAPEX keur OPEX keur/an

11 Distribution of capture cost ( EUR/t) Distrubution of capture cost, 53 EUR/t (case 3a) bark boiler 19% Compressor 9% The capture cost is a combination of CAPEX and OPEX devided on amount of CO 2 captured. 10 EUR/t Absorber 5% OPEX stand for 56 % of the capture cost. Reduction in sold certificates 4% Reduction in sold electricity relative reference 14% 2,1 EUR/t 7,6 EUR/t HEX-1 7% The main cost parameter is the bark boiler. It takes almost 20 % of the capture cost. The reduction in sold electricity and reduction in sold certificates is 18 % of the costs. 5,5 EUR/t HEX-2 10% HEX-5 7% Reboiler 11% 11

12 Centralised absorber vs separate absorbers Common absorber/stripper Seperate absorber- common stripper 12

13 One or two absorbers? Economy of scale makes the CAPEX for 1 absorber less costly. 2 absorbers are more costly than 1, 2 flue gas blowers are more costly than 1 ect. The distance between the sources is crucial- it is more costly to transport flue gas over long distances than pipes with rich/lean amine. In this case, the distance was approx. 300 m. Opex is slightly less costly with two absorbers In this case, more CO2 can be captured with 1 absorber, and that is the most important parameter for the result of capture cost ( more costly with 2 absorbers) 2 absorbers may give the opportunity to optimize the capture rate for the specific flue gas Conclusion: The economy of scale makes 2 absorbers more costly, but if the distances is long, the cost for ducts may also be important. 13

14 Conclusions There is a potential for capture of biogenic CO 2 in the pulp and paper industry to compensate for emissions in other sectors; 1-2 mill ton from state of the art pulp mill sites at a couple of locations in Sweden and Finland Non-integrated, stand alone pulp mills are the primary target as they have an excess of energy The CO 2 capture cases investigated for the pulp mill result in specific cost of CO 2 capture in the range of EUR/t CO 2 captured The lowest costs are obtained with max partial capture (about 65-70% of total emissions) utilizing excess energy otherwise used to generate electricity in a condensing turbine Investing in a new bark boiler to reach full CO 2 capture increases the specific capture cost significantly (10-12 EUR/t) The CO 2 capture cost is low compared to other industrial sources Economy of scale, large plant with 1 main stack (recovery boiler) Excess energy and fuel (by-products such as bark) available However, additional cost of loss of green electricity certificates in the order of EUR/t CO 2 captured Few incentives for CO2 capture; requires new financial measures to stimulate investments! 14

15 BECCS is just one of many optional ways that pulp & paper can contribute to CO 2 emission reduction a) Additional production of renewable electricity from bio-based by-products (lignin, bark) b) Use of bio-based by-products to replace internal use of fossil fuels (e.g. use of wood powder, bark powder or tall oil pitch as replacement to heavy fuel oil in the lime kiln) c) Production of bio fuels from by-products for external use (e.g. wood chips, wood pellets, lignin etc.) d) Production of bio-based as external replacement of fossil raw materials (e.g. pyrolysis oil to oil refineries, biocoal to steelmaking and the metal industry etc.) e) Production of new materials that during application results in indirect reduction of CO2 emissions (e.g. use of wood-based carbon fibers as lightweight materials in the automotive industry) f) CCS, i.e. carbon capture and storage of the remaining fossil CO2 emissions in the pulp industry (e.g. CCS on a lime kiln using heavy fuel oil or natural gas) g) BECCS, i.e. capture and permanent storage of emissions of biogenic CO2 from the pulp mill s emission sources, resulting in negative emissions of CO2, which is the focus of the pulp- and paper mill case study in the CO2StCap project. Technical, economic feasibility and market potential have to be evaluated against overall effect on CO 2 emissions!

16 THANK YOU! Acknowledgements The authors wish to thank the partners in the CO2stCap project, Climit and Swedish Energy Agency for financial contribution. The University College of Southeast Norway, Chalmers, RISE, Swerea MEFOS, SSAB, GCCSI, IEAGHG, Elkem AS, Norcem Brevik AS and AGA Gas AB. Research Institutes of Sweden

17 Division of CO 2 capture cost on sub-costs including green certificates Bark boiler Distribution of CAPEX (case 3a) OP-1 Compressor HEX-9 HEX-5 Reboiler X- HX Absorber Absober packing Flash tank Other Flue gas HX 17

18 Main reactions leading to emissions of CO 2 Recovery boiler: Na2SO4 + 2 C -> Na2S + 2 CO2 (biogenic C) C + O2 -> CO2 + heat for reactions (biogenic C) Lime cycle Na2S + Na2CO3 + Ca(OH)2 -> Na2S + 2 NaOH + CaCO3 (dissolution in weak white liquor and precipitation of CaCO3) CaCO3 -> CaO + CO2 (in lime kiln) (biogenic C) C + O2 -> CO2 + heat for reactions in lime kiln (biogenic C or fossil) CaO + H2O -> Ca(OH)2 Power boiler Combustion of bark and by-products for generation of steam and power (biogenic C)

19 Economic assumptions An overview of important assumptions for the CAPEX calculations: Reference year for cost level: 2015 Currency: EUR ( ) Rate of return: 7,5 % No of years: 25 (3 year of construction and 22 years in operation). The capture plant is treated as an extension to the existing plant Operational time 7840 h Green sertificates for green electricity production Utility Unit Unit cost (EUR) El price EUR/kWh 0,03 Green certificates EUR/kwh 0,015 Maintenance % of CAPEX 4 % Cooling water EUR/m3 0,02 Steam EUR/ton 16,67 Bark EUR/MWh 16 19

20 Sensitivity case 3a, base value 53 /t CO 2 Number of years Operating hours rate Opex cost. Cooling water Maintenace Green sertificates El cost EUR/t added to capture cost

21 Emissions of CO2 in Sweden 21

22 Future work Extraction at higher pressure for full capture Energieffektiviserer- hva kan det gi som resultat? Se på CCU, der vi tar co2 fra lime kiln og gjør lignin Sesongvariasjon- endre flere parameter samtidig- ved å bare operere om sommeren vil el pis og damp. Sammenligne vårt system med et stort biokraftvarmeverk som f eks det i Stockholm eller amagerverket 22

23 Partial capture two design approaches ṁ solvent f ABS 90 % Full capture 100 % D 0 f( ) ṁ solvent f ABS 90 % ṁ solvent f ABS e.g. 45 % Partial capture e.g. 50 % 100 % 23 QSPEC 1 = QSPEC 0 CAPEX 1 << CAPEX 0 D I < D 0 f( ) D I = D 0 f( ) QSPEC 1 < QSPEC 0 CAPEX 1 < CAPEX 0