1. Introduction - Firenze University Press

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ways. It could for example be used to cover the heat demand of production processes for additional products (such as electricity production or capture of CO2)or it permits the introduction of processes which reduces the steam production whilst producing new products (such as extraction of lignin or black liquor gasification where the product gas is used to produce motor fuels or electricity). Throughout this paper these two options are referred to as “utilisation of a potential steam surplus”.In a previous study by the authors [18], it was shown that making investments in steam saving measures and thereby enabling production of additional products generally is very profitable and contributes to reduction of global CO2 emissions. The trend in the pulp and paper industry is toward fewer mills with larger capacity. This means that some mills will be closed down, while the remaining mills will increase their production capacity [15]. For increased production capacity in pulp mills, the recovery boiler is often a bottleneck. In a study by Axelsson et al.[16], lignin extraction was found to be an economically attractive alternative for debottlenecking the recovery boiler, in comparison to upgrading the recovery boiler (and steam turbines) at a kraft pulp mill. The economic performance of lignin extraction compared to increased electricity generationfor utilization of a potential steam surplus is better for mills investigating investment options in connection with increased production capacity [8, 16]. Another approach to achieve debottlenecking of the recovery boiler is to introduce a black liquor gasifier as a booster. This approach has been investigated by for example Berglin and Andersson[17], who concluded that a black liquor gasifier using the product gas for steam generation yields a better economic return than investing in a new recovery boiler (it was assumed that the existing recovery boiler could not be rebuilt). 2. Objective This paper compares three different options for debottlenecking the recovery boiler and utilizing a potential steam surplus at a typical Scandinavian kraft pulp mill when increasing the production capacity by 25%: <strong>1.</strong> Upgrading the recovery boiler 2. Lignin extraction 3. Black liquor gasification (as a booster) For black liquor gasification two options for the product gas are considered; production of electricity (black liquor gasification combined cycle, BLGCC) or DME motor fuel (black liquor gasification with motor fuel production, BLGMF). Furthermore, both black liquor gasification and upgrading of the recovery boiler are assumed to be possible to combine with carbon capture and storage (CCS),where excess steam is used to cover the heat demand of the capture process. The extracted lignin is assumed to either be valued as wood fuel or as oil. The different options are evaluated and compared with respect to annual net profit and global CO2 emissions for four different future energy market scenarios. A further analysis of how different parameters such as policy instruments and investment costs affect the different technologies is also included. The results are compared with the results from the previous study by the authors where no production increase was considered; see [18]. 3. Methodology This work follows a methodology previously developed and described by one of the authors [6, 9]. The methodology enables changes in a studied energy system to be analyzed in a systematic way. The main steps in this methodology are briefly described below: 271
<strong>1.</strong> Define the studied system (in this case the kraft pulp mill). 2. Define possible system changes to be evaluated (in this case the investments in energy efficiency measures together with the different options for debottlenecking the recovery boiler). 3. Define the surrounding system used for evaluation of the studied system (in this case the different energy market scenarios describing energy market prices, policy instruments and associated CO2 emissions for marginal use of energy carriers). 4. Construct a model for simulation of energy flows in the overall system defined in steps 1-3 (in this case the simulation model is constructed using the energy systems modelling tool reMIND). 5. Define the performance indicator(s) to be used for evaluating the system changes considered (in this case the net annual profit and global CO2 emissions). 6. Use the simulation model to optimize the system based on the selected performance indicator for given settings in the surrounding system (defined by the aim of the study in question). 7. Vary key settings in the surrounding system to see how/whether the optimal solution is affected by these changes (in this study we calculate the optimal solution for a number of possible energy market conditions defined by energy market scenarios). 8. Fix certain parameters in order to investigate how close other solutions of interest are to the optimal solution (in this case solutions for all of the studied energy related technologies are obtained together with a sensitivity analysis showing the effect of changes in different system parameters) 9. Analyze the results in relation to the aim of the study (as defined by steps 1-3). For constructing the model of the studied system and the surrounding system (described in step 3 above) the energy systems modelling tool reMIND, based on mixed-integer linear programming, is used. The reMIND tool has previously been used and described by e.g. Karlsson [19]. With this tool a simulation model of an energy system can be specified using a graphical interfaceand pre-defined equations. The constructed model can then be used for optimization purposes. In this study the objective is to minimize the total annual system cost of the studied energy system (the mill), assuming given conditions in the surrounding system (the energy market, including policy instruments) and the objective function can be defined as follows: min Z = rI tot - B tot + C tot (1) wherer = Capital recovery factor (0.2) I tot = Total investment cost (energy efficiency measures and technologiesfor utilizing the steam surplus and debottlenecking the recovery boiler) B tot = Revenue of sold energy products including policy instruments (electricity, district heating, bark, captured CO 2, biofuels etc.) C tot = Running costs (electricity, chemicals etc.) For the system studied in this paper the different parameters, that is the investment costs, running costs and revenues for the different technologies, are described in Section 4. Asdescribed above, reMIND is constructed for minimization of the annual system cost. The different investment options studied in this paper are profitable when the annual system cost, Z, is negative. Hereafter the annual system cost is therefore referred to as the system’s annual net profit. 272
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Proceedings e report 90
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ECOS 2012 : the 25 th International
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Advisory Committee (Track Organizer
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The 25 th ECOS Conference 1987-2012
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VOLUME VI CONTENT VI. 1 CARBON CAPT
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-----------------------------------
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» Personal transportation energy c
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» Excess enthalpies of second gene
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VOLUME IV IV . 1 - FLUID DYNAMICS A
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» Exergy analysis and genetic algo
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» Optimal lighting control strateg
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» Stability and limit cycles in an
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PROCEEDINGS OF ECOS 2012 - THE 25 T
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Fig. 2. The exergy destruction of M
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ineffectiveness of the catalyst, in
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[ P EXmth EX SNG] ESR F where EXm
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Fuel inputkW 728221 203771 237719 3
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Not only at desined Rc (the ratio o
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4. DISCUSSION The graphic exergy an
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Figure 9(a) illustrates the energy
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Engineering Technical Conferences &
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generally there are four kinds of m
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However, even under the off-design
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Fig. 3. 600MW supercritical coal-fi
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CO2 rich loading(molCO2/molMEA) 0.4
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Net efficiency (%) 40.28 30.29 26.4
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Fig. 11. Schematic diagram of heat
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28.67%. In addition, through heat i
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Applied Thermal Engineering 2010;30
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Abstract: PROCEEDINGS OF ECOS 2012
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Fig. 1. Solution diagram of „four
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K ~ K 1 eK 1a p K 1a iK mK
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Oxygen recovery rate, % 105 95 85 7
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Calculated optimal compressor press
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The net amount of the flue gas leav
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Figure 3. Idea for lignite drying b
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Energy efficiency, % 34,00 33,00 32
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points efficiency increase related
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Figure A1b. Thermoflex flow sheet o
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Figure A3a. Thermoflex flow sheet o
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Figure A4. Thermoflex flow sheet of
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2.1. Life Cycle Assessment 2.1.1. G
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these factors. A sensitivity analys
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methane slip contributes to 13% of
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As can be seen in Fig. 5 the impact
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References [1] Eurobserv’er, The
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in which CO2 is separated from H2,
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dimensions of water droplets and wa
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Temperature (°C) 8 7 6 5 4 3 2 1 0
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4. Conclusions In the present paper
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penalty, but without separate captu
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0.5 - 0.7 kg/kg, resulting typicall
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3.3 - Utilising waste heat All exis
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4.5 - Suomusjärvi olivine deposits
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material will change from a few % t
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Fig. 5 Schematic diagram of the PFB
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8. Combined SO2 capture and CO2 min
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Fig. 10 Carbonate- (left) and sulph
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[13] Ekdahl, E., Idman, H. Statemen
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HEAT Fig. 1. Scheme and main reacti
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(raw) materials pre-heating and AS
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Fig 3- Aspen Plus® model 110
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Table 4. Elemental and XRD analysis
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the ÅA CSM route. The content of M
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moisture - 0,2237 ash - 0,0876 LHV
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2.2 CFB plant For the current momen
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The CO2 emission factor which indic
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The CO2 emission factor calculated
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Appendix A Fig A.1. Simulation mode
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(b) Fig. A.2. Simulation model of C
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Table A.1. Calculated parameters at
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References [1] Pfaff I., Oexmann J.
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with a CC installation could be avo
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2.3. Basic CHP plant indices. The b
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3. Off-design calculations The main
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Fig. 6. CHP plant efficiency Fig. 7
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amount of steam delivered to the he
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[5] Lukowicz H., Mroncz M.: Analysi
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water removal is feasible by coolin
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Figure 2. Sketch of the suggested P
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a b Figure 5. a) Exergy balance of
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The basis of comparison of each met
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Figure 7a. Impact of S/CATR on PCU
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However, more energy duty is requir
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3.1. JACOBIAN-ASPEN Interface ASPEN
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Fig. 3. Triple Pressure Bottoming S
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As seen from Table 1, the mass flow
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4. Conclusion Fig. 5. Partial Emiss
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[19] Yantovski E., Shokotov M., Sho
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investigation and the developing of
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University of L’Aquila and German
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hydrogen combustion technology at d
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eversibility of a pre-treated synth
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Fig. 1. TG curves collected for spe
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(see Fig 5). Carbon dioxide uptake
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period is reduced to the first 15 c
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CO2 capture capacity up to 150 th c
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the way for biogas utilisation is t
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projectand is described in the foll
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4. Pilot plant tests In order to de
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Concerning the absorption reaction,
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with Regeneration (AwR), consists i
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[25] Aspen Plus 2004.1. Cambridge,
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systems for fuel drying waste strea
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heated in a heat exchanger placed i
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Fig. 2. Lower heating value of fuel
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Acknowledgements The results presen
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large amount of CO2 [1,5-7]. APCr a
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N 1 i ( x x i n 1 m ) 2.3. Carbon
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DTA analysis of the untreated APCrs
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Table 4. Relative Error (%) of the
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CaO HCl CaCl H O 193kJ / mol (
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[1] M. Fernández Bertos, S.J.R. Si
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Page 275 and 276: Table A2. Extraction equations and
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3.2.2. Input data and assumptions A
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Fig.7 shows the operation forecast
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[13] TERMIS Operation User Guide, 7
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Polygeneration is a term used to de
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The increase in energy utilization
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are available for an entire year, 8
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6. Extensions to core methodology 6
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thermal storage and possible suppor
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laterites. Ore Geology Reviews, v.
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gasification [15], hybrid biomass g
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the second reactor. In this unit, s
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The variables effect was evaluated
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atio, as well as the shift-syngas f
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Fig. 4. Effect of operating tempera
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SDG has slight effect on the syngas
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[26.] Castle WF. Air separation and
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1. Introduction - Firenze University Press

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