1. Introduction - Firenze University Press

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As the mass flow rate of "AIRREST" increases, the compressor power and flow rate through the turbine increase, thus increasing the power output from gas turbine "GT". At the same time, increase in "AIRREST" flow rate, keeping the "B10" split fraction constant, decreases the input temperature to the turbine, which decreases the output power. A similar effect is seen for the variation of the "B10" split fraction. For fixed "AIRREST" flow rate, increased direct flow through the gas turbine results in lower gas turbine "GT" inlet temperatures. However, this results in smaller flow rates through "BHEX" and thus, the maximum energy in the heat exchanger is not extracted. When the flow to the heat exchanger is large, the air inlet flow temperature to the gas turbine decreases. The interplay of these effects emphasizes the importance of optimization. As aforementioned, it is advantageous to extract the maximum possible power from the gas turbine and transport less thermal energy to the bottoming cycle. Therefore, the air outlet temperature from the heat exchanger "BHEX" must be the maximum possible, while satisfying the minimum pinch. Fixing the pinch which occurs at the hot end to 10 K, for inlet temperature of combustion products 1473.15 K, the outlet temperature of air must be 1463.15 K. However, it is seen that as air flow rate through the heat exchanger "BHEX" is increased, air outlet temperature begins to decrease after a point. Though larger air-flow through "BHEX" is expected to produce more power in gas turbine "GT", other deteriorative factors such as a higher air compression power required, and lower air outlet temperature in "BHEX" also come into play. It is seen from the optimization results of Table 1, the local optimum occurs at lower flow rates, with maximum possible air outlet temperature from "BHEX". The amount of "GT" turbine blade cooling required is chosen according to performance maps [11 Chart 5.16] and is specified as an optimization constraint. Performance maps specify the amount of cooling air required based on the turbine inlet temperature. As the optimizer searches for a local optimum, the turbine inlet temperature varies. Therefore, a constraint is added to meet the turbine blade cooling requirements. The average of the lower and upper limit of this range is chosen for our optimization studies. Based on the performance map: For faster convergence of the ASPEN Plus ® optimizer, the design specifications of the topping cycle have been implemented as optimization constraints. The split fractions of "B6" and "B3", which are treated as design specification variables earlier, are now treated as optimization variables. This means, in addition to the actual optimization constraints, design specifications also become optimization constraints, and in the process, design specification variables now become optimization variables. The minimum approach temperature for "BHEX" is also treated as an optimization variable. Table 1. Results of Optimization of Topping cycle Variables Units Before Optimization After Optimization Molar flow rate of AIRREST kmol/s 5.665 9.28 Molar flow rate of AIRMCM kmol/s 37.335 49.18 Split fraction of B6 (BLDPROP) 0.1267 0.1189 Split fraction of B10 (Stream 2) 0.73 0.7169 Air outlet temperature from BHEX K 1463.15 1463.15 ITM ΔP feed/permeate (%) ITM Recovery ratio Efficiency 163 1.1/0.6 29.1 25.33 % 1.5/0.9 30.51 26.07%
As seen from Table 1, the mass flow rates of both "AIRMCM" and "AIRREST" have decreased. This implies lesser oxygen separation across the ITM and lower fuel intake. Split fractions of "B6" vary to attain minimum approach temperature in heat exchanger "LHEX" without any temperature crossover in the heat exchanger network "LHEX-ITM-HHEX" (implemented as one of the constraints). The air outlet temperature of "BHEX" does not change as 1463.15 K is the maximum temperature of air that can be reached for the specified minimum approach temperature of "BHEX". The first law efficiency, which is defined as the ratio of power output to the product of heating value of the fuel and the fuel flow rate, increases by 0.74 percentage points (from 25.33 % to 26.07 %) as a result of the optimization. Fig. 4. Variation of efficiency with air mass flow rate through "LHEX" Fig. 4 shows the effect of varying the air flow rate through the heat exchanger "LHEX" on the efficiency of the topping cycle, while the topping cycle is optimized by changing the other variables with the solution of the previous run as the initial guess value for the present run. Clearly, in the range 30 - 55 kmol/sec, only one local optimum exits and hence the point that has been reported has the maximum efficiency, although this does not prove that it is the global optimum. Thus global optimization is capable of improving the cycle efficiency even higher. 3.4.2. Optimization of Bottoming Cycle The bottoming cycle is a triple pressure HRSG. The input specifications of the streams "GTEHX" and "PRODBOTM" are specified using the results obtained from the optimized top cycle, and the bottoming cycle is then independently optimized. The variables considered for optimization of the bottoming cycle include the three pressure levels, the discharge pressure of the turbine and the condenser pump, and the split fraction of the three splitters. Lowering the temperature of stream "EXHEXIT" which leaves the heat exchanger "ECON" and increasing the temperature of streams "HPSTM" and "IPSTM" which exits the heat exchanger "HPSP" increases the efficiency as the heat input to the bottoming cycle increases. Thus, the outlet temperature of the heat exchangers "ECON" (stream "EXHEXIT") and "HPSP" (streams "HPSTM" and "IPSTM") are increased and decreased respectively, to the maximum possible extent such that there are no temperature crossovers in any of the heat exchangers. At the optimal point, the pinch value for heat exchangers "ECON" and "HPSP" are observed to be 4.8 K and 4.4 K respectively. This can be done only for the AZEP 100 as "GTEXH" is pure air without any CO2 emissions. This is not true in the case of partial emission cycles. For partial emission cycles, there is a limit on "ECON" outlet temperature since low temperatures can cause acid condensations. 164
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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
Page 139 and 140: Table 4. Elemental and XRD analysis
Page 141 and 142: the ÅA CSM route. The content of M
Page 143 and 144: Abstract: PROCEEDINGS OF ECOS 2012
Page 145 and 146: moisture - 0,2237 ash - 0,0876 LHV
Page 147 and 148: 2.2 CFB plant For the current momen
Page 149 and 150: The CO2 emission factor which indic
Page 151 and 152: The CO2 emission factor calculated
Page 153 and 154: Appendix A Fig A.1. Simulation mode
Page 155 and 156: (b) Fig. A.2. Simulation model of C
Page 157 and 158: Table A.1. Calculated parameters at
Page 159 and 160: References [1] Pfaff I., Oexmann J.
Page 161 and 162: with a CC installation could be avo
Page 163 and 164: 2.3. Basic CHP plant indices. The b
Page 165 and 166: 3. Off-design calculations The main
Page 167 and 168: Fig. 6. CHP plant efficiency Fig. 7
Page 169 and 170: amount of steam delivered to the he
Page 171 and 172: [5] Lukowicz H., Mroncz M.: Analysi
Page 173 and 174: water removal is feasible by coolin
Page 175 and 176: Figure 2. Sketch of the suggested P
Page 177 and 178: a b Figure 5. a) Exergy balance of
Page 179 and 180: The basis of comparison of each met
Page 181 and 182: Figure 7a. Impact of S/CATR on PCU
Page 183 and 184: However, more energy duty is requir
Page 185 and 186: Abstract: PROCEEDINGS OF ECOS 2012
Page 187 and 188: 3.1. JACOBIAN-ASPEN Interface ASPEN
Page 189: Fig. 3. Triple Pressure Bottoming S
Page 193 and 194: 4. Conclusion Fig. 5. Partial Emiss
Page 195 and 196: [19] Yantovski E., Shokotov M., Sho
Page 197 and 198: investigation and the developing of
Page 199 and 200: University of L’Aquila and German
Page 201 and 202: hydrogen combustion technology at d
Page 203 and 204: eversibility of a pre-treated synth
Page 205 and 206: Fig. 1. TG curves collected for spe
Page 207 and 208: (see Fig 5). Carbon dioxide uptake
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Page 211 and 212: CO2 capture capacity up to 150 th c
Page 213 and 214: the way for biogas utilisation is t
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Page 217 and 218: 4. Pilot plant tests In order to de
Page 219 and 220: Concerning the absorption reaction,
Page 221 and 222: with Regeneration (AwR), consists i
Page 223 and 224: [25] Aspen Plus 2004.1. Cambridge,
Page 225 and 226: systems for fuel drying waste strea
Page 227 and 228: heated in a heat exchanger placed i
Page 229 and 230: Fig. 2. Lower heating value of fuel
Page 231 and 232: Acknowledgements The results presen
Page 233 and 234: large amount of CO2 [1,5-7]. APCr a
Page 235 and 236: N 1 i ( x x i n 1 m ) 2.3. Carbon
Page 237 and 238: DTA analysis of the untreated APCrs
Page 239 and 240: 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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3. Case study 3.1. Plant and proces
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Te 1000 mp era 900 tur 800 e [°C 7
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Application of the approach led to
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The advantage of dynamic models is
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e equal at both time intervals and
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2.5. Selecting the number of TSs Se
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A) Time Slices for solar thermal en
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The first step of procedure is to p
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cTSs demand TS solar TSs 0 2 4 6 8
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In the presented paper a framework
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[5] Erdil E, Ilkan M, Egelioglu F.
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district energy network simulation
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were decreased by 10°C.All scenari
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Site 3 Heat sources Heat load Site
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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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