1. Introduction - Firenze University Press

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sour water-gas shift (WGS) process followed by an acid gas removal. H2-rich syngas is obtained after water condensation in the resulting gas. The SOG simplified process flow diagram is shown in Fig. 1: Fig. 1. SOG simplified process flow diagram. There are many technologies for separating air into its main components. The application of either one depends on the process requirements. For lower volumes of O2 and/or N2 (< 1.6 kg s -1 ), pressure swing adsorption or membrane processes are preferred [22]; whereas, for producing large quantities of gaseous products, cryogenic air separation technology is currently the most efficient, especially when high purity products are required [23]. The cryogenic process consists on several unit operations that compress, purify and separate air into its principal components. First, impurities (H2O, CO2, among others) are removed in a prepurification unit, located downstream of the air compression. Secondly, the air is cooled down to cryogenic temperatures (from 123 K to 463 K, depending on the operating pressure [24]) and goes into the air separation unit. Then, a multi-column cryogenic distillation is usually used for separating O2 and N2 [22]. Several configurations of rectifying columns and heat exchangers are made according to the requirements of the process [25]. A double column system is widely used in air separation processes. Air enters into the high pressure column (HPC) and provides two reflux streams that feed the low pressure column (LPC) [26]. At the top of the LPC, a pure gaseous nitrogen stream is obtained while liquid oxygen is evaporated at the bottom of this column to deliver a pure oxygen stream [25]. The two columns are built in a single tower for the commercial application, considering the use of a condenser-reboiler as a heat exchange unit [24]. The gasification process is developed using a GE gasifier with a gas-water quench system. Guaduas formation coal is wet-milled to a particle size about 100 µm and mixed with water to produce slurry. Coal slurry and O2 stream from the ASU unit are fed in the top of the pressurized reactor through burners. The coal reacts exothermally with O 2 at high temperature (> 1473 K) and high pressure (> 7 MPa) to produce syngas and slag [27]. The hot gas is contacted directly with water where the slag is solidified. The quenching process cools the syngas and generates a water-saturated gas product, leaving the quench chamber at a temperature between 473 K and 573 K. The resulting syngas is mainly free of particulate matter and water-soluble contaminants such as NH3, HCN and chlorides [20]. To increase the H2 concentration, the WGS process is employed to convert mostly CO into H2. This process consists of two reactors in series with intercooling. A high temperature (HTS) reactor (573 K - 873 K) as an initial stage followed by a low temperature (LTS) reactor (453 K – 523 K). The HTS reactor feed is heated by the effluent of the LTS to control the operating temperature. Additionally, the effluent of the HTS is cooled producing high pressure steam and then it is fed in 343
the second reactor. In this unit, syngas and steam are mixed with a steam to dry gas ratio (SDG) depending on the feed syngas water content and the required H2 to CO ratio. In the WGS reaction, chemical equilibrium favors products at low temperature; therefore, a catalyst is required to enhance the reaction rate. A catalyst typically made of sulfided Co/Mo on aluminum support reacts with the sulfurs, producing metal sulfides which activates the catalyst [28, 29]. Carbonyl sulfide (COS) is converted to H2S making the sulfur removal easier due to the WGS process location before the acid-gas removal process. For conditioning of the gas leaving the LTS, the Rectisol process is used. It employs methanol (CH3OH) as solvent to clean up the syngas. The high selectivity of methanol for H2S over CO2 at low temperatures (211 K to 233 K) and the ability to remove COS are the main advantages of the process. Besides, it allows a deep sulfur removal (< 0.1 ppmv H2S + COS) [30]. There are many possible process configurations for Rectisol, depending on the process requirements. A selective H2S removal configuration was used in the simulation. In this configuration, the raw syngas feeds up the main absorber in which CH3OH absorbs most of the impurities produced in gasification process such as CO2, H2S, COS, HCN and NH3 [31]. Thereafter, the solvent passes through a regeneration process, where these components are desorbed by reducing the pressure, stripping and/or boiling up the solvent. The regenerated and recirculated solvent is free of sulfur compounds but still contains some CO2. The acid gas leaving the solvent regeneration units is suitable for the Claus process [32]. 3. ASPEN PLUS ® Simulation Model In order to model the process, the following assumptions were considered: 1) the process is in steady state, 2) the coal feed flow rate is 12500 (kg h -1 ), 3) the reactors are perfectly insulated, 4) heat losses are neglected, and 5) coal tar is not modeled; char only contains carbon and ash. Main unit operations modeled in Aspen Plus ® are shown in Table 3: Table 3 Main blocks used in the process Aspen Unit operation Plus Comments/specifications model ASU RadFrac LPC: Rigurous distillation model, first stage to separate N2 and O2. SN 40, RR 12.3, BR 41.3, partial-vapor condenser, TSP 0.14 MPa, CPD 0.005 MPa. HPC: Rigurous distillation model, second stage to separate N2 and O2. SN 26, RR 0.5, BR 1.0, partial-vapor condenser, TSP 0.6 MPa, CPD 0.05 MPa. Coal Gasification RGibbs Specification of the possible products: CO, CO2, C, H2, H2O, CH4, SO2, H2S, S, CS2, COS, N2, NH3, HCN, O2, NO2, NO3. HTS reactor REquil Specification of the stoichometric reactions. OP 3.8 MPa, OT 623 K. LTS reactor REquil Specification of the stoichometric reactions. OP 0.5 MPa, OT 473 K. CH3OH absorber Radfrac Rigorous absorption of H2S, SO2, COS, NH3, HCN. SN 10, TSP 3.2 MPa. SN: Stage number; RR: Reflux ratio; BR: Boil up ratio; TSP: Top stage pressure; CPD: Column pressure drop; OT: Operating temperature; OP: Operating pressure. 3.1. Physical Property Method 344
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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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2. Process development 2.1. Backgro
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to dissolve the chloride salts prec
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The remaining 25% (5 ml/min) of the
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Table 6. Experimental conversions o
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p p 1 1. 5 p H 1 1. 5 2O p mi
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Calculating from the Aspen Plus mod
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[11] Mattila, H.-P., Experimental s
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Mg2SiO4(s) + 2CO2(g) →2MgCO3(s) +
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(Mg/Fe) of the mineral rock, Mg-sil
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Figure 2. Effect of Mg/Fe ratio of
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Figure 4 shows that an increase in
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Figure 5. Process flow diagram of M
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2. Only cold utility is needed belo
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extraction process at 400 °C (~ 62
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Table A2. Extraction equations and
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[13] Teir S, Kuusik R, Fogelholm CJ
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In the area of coal technologies al
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Tabel 1. Characteristics quantities
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N m eT 4a ~ T cp T4a 1 ( K
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Auxiliary power rate of ASU, % 40 4
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[8] Buhre B.J.P., Elliott L.K., She
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1.1 - Cement Manufacturing The ceme
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2. Numerical model The purpose of t
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-0.309x15.77x2 2.085x3 240x4 12.53x
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Table 4 - Results of the optimizati
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1. Define the studied system (in th
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cycle) or a lignin extraction plant
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limiting factor for the maximum siz
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Table 5. Key data for the four ener
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Global CO 2 emissions [ktonnes/yr]
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for biofuels and the investment cos
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The possibility to capture CO2 from
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[17] Berglin N, Andersson L. Proces
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Therefore NL Agency (an agency of t
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2.2.2. Pinch analysis Pinch analysi
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Page 361 and 362: 6. Extensions to core methodology 6
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Page 367 and 368: Abstract: PROCEEDINGS OF ECOS 2012
Page 369: gasification [15], hybrid biomass g
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1. Introduction - Firenze University Press

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