Hybrid molten carbonate fuel cell power plant and multiple-effect desalination system

Journal of Cleaner Production 220 (2019) 1039e1051

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Hybrid molten carbonate fuel cell power plant and multiple-effect desalination system Bahram Ghorbani a, Mehdi Mehrpooya b, *, Seyed Ali Mousavi b a b

Faculty of Engineering Modern Technologies, Amol University of Special Modern Technologies, Amol, Iran Department of Renewable Energies and Environment, Faculty of New Science and Technologies, University of Tehran, Tehran, Iran

a r t i c l e i n f o

a b s t r a c t

Article history: Received 29 September 2018 Received in revised form 4 February 2019 Accepted 20 February 2019 Available online 21 February 2019

In this work, an integrated system of simultaneous power generation, refrigeration and desalination cycle using a molten carbonate fuel cell, is developed and investigated. The process is simulated by HYSYS and MATLAB softwares. Molten carbonate fuel cell subsystem is the main power generation source, which produces 72000 kW power. Absorption refrigeration cycle with ammonia-water mixture as the working fluid is utilized for providing the required refrigeration. The required heat duty is supplied by exhaust heat from the power plant. This absorption refrigeration cycle can provide 32090 kW refrigeration with coefficient of performance of 0.4915. Four stage multiple-effect desalination subsystem produces 118944 kg/h fresh water. The proposed process is assessed by conventional exergy analysis method in order to evaluate performance of the process. Results of the energy analysis illustrate that overall thermal efficiency based on higher heating value (HHV) and lower heating value (LHV) are 54.37% and 60.32%, respectively. Results of the exergy analysis show that molten carbonate fuel cell with 91062 kW has the most exergy destruction rate. Also, generator has the most exergy efficiency (98.67%) and overall exergy efficiency of the process is 88.95%. Finally, a sensitivity analysis is applied on the major operating parameters of the system to demonstrate their effects on the performance of the process. © 2019 Elsevier Ltd. All rights reserved.

Keywords: MCFC Absorption refrigeration system Multi-effect desalination Exergy analyses Sensitivity analyses

1. Introduction By increasing the energy demand and potable water, investigation of hybrid renewable energy and potable water production systems is considered as a sustainable solution (Gude and Nirmalakhandan, 2010). Renewable energy resources unlike fossil fuels are sustainable and do not cause acid rains and ozone layer depletion. Hydrogen has been known as the future fuel because of its properties and zero-emission when burned with oxygen. Fuel cells convert chemical energy of the fuel directly to the electricity with high efficiency and no combustion. So fuel cells can be utilized as the main power generation devise in the combined systems. A hybrid system consists of molten carbonate fuel cell (MCFC) and pressure swing absorption (PSA) is analyzed (Verda and Nicolin, 2010). The results show that total energy efficiency increases by operating temperature of the fuel cell. A combined system includes solid oxide fuel cell (SOFC) and hydrogen production is evaluated by thermodynamic analysis (Leal and Brouwer, 2006). The outcomes

* Corresponding author. E-mail address: [email protected] (M. Mehrpooya). https://doi.org/10.1016/j.jclepro.2019.02.215 0959-6526/© 2019 Elsevier Ltd. All rights reserved.

display that the total exergy efficiency is about 61%. A combined system consist of micro gas turbine and SOFC is evaluated thermodynamically (Costamagna et al., 2001). Thermal efficiency of the system is gained 60%. Energy and exergy analyses are performed for an MCFC cogeneration system (Silveira et al., 2001). Thermal efficiency and exergy efficiency are gained 44% and 42%, respectively. A novel MCFC hybrid process which uses solar energy is introduced and analyzed (Mehrpooya et al., 2018). The results show that the proposed process has overall thermal efficiency of 73.14%. Desalination process is one of the conventional methods to produce potable water, which can be utilized fossil fuels or renewable energy resources such as solar energy, for supplying the required energy (Ghaebi and Abbaspour, 2018). Several investigations have been carried out in the area of desalination processes. A solar power system integrated with desalination cycles is studied and analyzed (Mehdi Mehrpooya, 2018). In this study multi-Effect desalination process with a parallel feed of seawater is used. MED-RO desalination system is investigated and evaluated by exergy analysis (Sadri et al., 2017). The results show that thermal vapor compression has the highest exergy destruction rate and by increasing the volumetric flow rate of the feed water, exergy efficiency decreases.

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Nomenclature e _ Ex G h Q_ _ m N s S T Uf _ W V x Wt P Ra

Specific exergy (kJ/kgmol) Rate of exergy (kW) Gibbs free energy (kJ/kgmol) Specific enthalpy (kJ/kg) Heat transfer rate (kW) Mass flow rate (KJ/Kg) Number of effects Specific entropy (kJ/kg.K) Entropy (kJ/K) Temperature (K) fuel utilization factor Power (kW) Volume(m3) Mole fraction() Weight fraction concentration (%) Pressure (bar) entrainment ratio

Greek symbols P Sum hex Exergy efficiency (%) D Delta n Steam Subscripts 0 ex min tot max D

Dead state Exergy Minimum Total Maximum Destroyed

A multi-effect desalination system driven by solar steam production plant is studied and analyzed (Bataineh, 2016). The results indicate that efficiency of the system improves by rising temperature of the first stage. In recent years many modifications have been carried out about refrigeration systems to reduce the power consumption and initial costs. Replacing absorption refrigeration cycles (ARC) with vapor compression cycles is an efficient idea for reducing energy consumption and efficiency improvement (Lim et al., 2014). These systems utilize a thermal compressor instead of a compressor. So they consume heat duty instead of electrical power (Ghorbani et al., 2018d). In ARCs, LiBr/H2O and H2O/NH3 mixtures are commonly utilized as the working fluid (Srikhirin et al., 2001). In recent years, many investigations about ARCs and combined these cycles with other cycles such as: power generation and desalination system have been performed. An absorption refrigeration cycle which is utilized for liquefied natural gas (LNG) production and driven by waste heat from the gas turbine, is investigated (Kalinowski et al., 2009). The outcomes show that by generating 9 MW electricity, 5.2 MW waste heat is produced and can be used in ARC. A hybrid system, include LiBr/H2O ARC and potable water production is studied and evaluated (Wang and Lior, 2011). Coefficient of performance (COP) and exergy efficiency of the system are obtained by 1.3 and 60%, respectively. Alelyani et al. (2017) (Alelyani et al., 2017) compared a hybrid system consists of NH3/H2O ARC and multi-effect distillation (MED) with standalone ammonia-water and MED systems. It is shown that by utilizing the hybrid system, total exergy destruction rate reduces by

F P p ph ch mix i k in out

Fuel Product potential Physical Chemical Mixture Component i kinetic inlet outlet

Names utilized for devices in plants Ci Compressor GTi Gas turbine Ti Tower Di Flash drum Ei Heat exchanger Pi pump Vi Valve Abbreviations MED multi effect desalination NEA non-equilibrium allowance LMTD logarithmic mean temperature difference ARC Absorption refrigeration cycle COP Coefficient of performance NG Natural gas MCFC Molten carbonate fuel cell PCF Pressure correction factor TCF Temperature correction factor HHV High heating value (kJ/kg) LHV Low heating value (kJ/kg)

55%. A hybrid system which includes: water desalination, CO2 liquefaction and oxy-fuel power generation is proposed and analyzed (Ghorbani et al., 2018a). The results illustrate, this hybrid system generates 74.58 ton/h desalinated water, 84.62 ton/h CO2 and 593.3 ton/h LNG. Also, shell and tube heat exchangers and air coolers have the highest and lowest exergy destruction rate, respectively. A novel hybrid cooling, heating and power generation (by SOFC-ST) system with a natural gas liquefaction process is reported (Mehrpooya, 2016). The results indicate that overall thermal (LHV Base) and electrical efficiency (HHV Base) of the proposed process are 81.7% and 64.9%, respectively. Performance of a hybrid combined cooling, heat and power (CCHP) system that includes molten carbonate fuel cell and sterling engine is analyzed by energy and exergy assessment methods (Mehrpooya et al., 2017b). Outcomes show that output power of this hybrid system is 6482 kW with overall efficiency of 71.71%. Also, based on the results duct burner has the highest exergy destruction rate (5.94
106 kW). A hybrid system consists of MCFC power plant, hydrogen production and cryogenic CO2 capturing is investigated and analyzed (Mehrpooya et al., 2017a). The results indicate that this system can provide 90 kmol/h H2, 101.2 kW refrigeration load and 6.55 MW output power. In another research a hybrid system that produces simultaneous power, heating and potable developed and evaluated (Ghorbani et al., 2018b) the performance of. According to the outcomes, the total exergy efficiency and total thermal efficiency are obtained by 90.04% and 44.64%, respectively. In this study, an integrated process that produces power, cooling

B. Ghorbani et al. / Journal of Cleaner Production 220 (2019) 1039e1051

and potable water, is investigated and analyzed. The required power is supplied by molten carbonate fuel cell and gas turbine. Exhausted heat from the power plant is used for supplying the required heat load in the absorption refrigeration cycle. Energy and exergy methods are used for evaluation of process performance.

CO2 þ 0:5 O2 þ 2e / CO2 3

(2)

Overall cell reaction:

H2 þ 0:5 O2 / H2 O

(3)

To validate the proposed fuel cell model, two references ((Mehrpooya et al., 2017b), (Milewski et al., 2014)) were used. Fig. 2 illustrates results of the validation. According to this figure, the proposed model has an acceptable accuracy. In continue for utilizing the fuel cell model in the developed integrated process, corrective changes on the temperature and pressure is done. Natural gas with flow rate of 4.31 kg/s and air flow rate of 117.57 kg/s follows to C2 and C1 compressors, respectively. Natural gas (stream 101) and steam (stream 103) are mixed together to react and produce the required H2. Water stream after passing through P100, enters E100 heat exchanger in order to phase change to steam and at 170  C is mixed with stream101. Stream 104 at 150.8  C and with flow rate of 19.12 kg/s is sent to E102 for preheating. After preheating, stream 105 at 298  C is sent to the Reformer to produce the required H2. The hydrogen is produced by steam reforming reaction as follows:

2. Process description and simulation 2.1. Process description Fig. 1 indicates flow sheet of the developed integrated process. This process contains three subsystems: power plant with molten carbonate fuel cell (MCFC), absorption refrigeration cycle and multiple-effect desalination (MED) process. Table 1 presents specifications of the developed integrated process streams. Table 2 illustrates composition of the important process streams. 2.1.1. Power plant with molten carbonate fuel cell (MCFC) In this subsystem, pressurized molten carbonate fuel cell and GT100 and GT101 gas turbines, produce the required power of the process. In MCFC, chemical energy of the natural gas is converted to power. In the cathode, CO2 3 ions are generated and after passing through the membrane, reach to the anode side (Gude and Nirmalakhandan). In the anode side, CO2 3 ions are reacted with H2 to produce electrons. Electrochemical reactions in the MCFC system can be written as follows (Koh et al., 2000): Anode side:  CO2 3 þ H2 / H2 O þ CO2 þ 2e

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CH4 þ H2 O 4 CO þ 3H2

(4)

Also, supplementary H2 can be generated by water gas shift reaction, which can be written as follows:

CO þ H2 O 4 CO2 þ H2

(5)

The overall reaction is expressed by equation (6):

(1)

CH4 þ 2H2 O 4 CO2 þ 4H2

Cathode side:

(6)

315 313

E107

E106

E114 Generator

317

305

402

P101

E104

125

403

414

E110

419

E111

`

410 408

405

427

307

432

409

E112

416 412

406

413 415 411

422 418

417

D4

E109 404

T100

300

407

D3

D5

400

318

Chiller

401

321

312

P103

126

323

308

304

424

E108

319

320

434

V5

322

E105

V2

V1

311

436

437

D2

HX8

309

435

V4

422

314 301

316

303

Ejector

302

V3

306

D1

310

V6

E103

425

421 420

426

423 428 429

122

C3

117 118 C

108 C

GT100

107

Cathode

430

114

110

Catalytic C burner

109

124

112

C2

NG

116

E102 104

101

15 ºC, 1 bar, 15505 kg/h,

105 Reformer 103

Natural Gas

106

E100

P102

202 203 Water

102

P100

200

123

E101

E113

431

Desalinated Water

111

Anode

Air

115 113

100

15 ºC, 1 bar, 423249 kg/h,

Natural Gas

119

121

C1

AIR

120

Splitter

Combustion chamber C

25 ºC, 1 bar, 193114 kg/h, Sea Water

15 ºC, 1 bar, NG1 2888 kg/h,

GT101

201

Fig. 1. Process flow diagram of the developed integrated process.

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Table 1 Specifications of the developed integrated process streams. Stream

Temperature (ºC)

Pressure (kPa)

Mass flow (kg/s)

Stream

Temperature (ºC)

Pressure (kPa)

Mass flow (kg/s)

100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 200 201 202 203 300 301 302 303 304 305 306 307 308 309 310 311 312

126.6 99.78 25.02 170.0 150.8 298.0 610.0 492.8 878.4 878.4 742.3 750.3 750.3 744.4 728.2 728.2 690.0 731.6 731.5 731.5 106.6 952.2 952.2 800.0 528.2 118.0 61.83 36.07 795.0 682.2 31.06 123.2 45.49 33.98 10.00 27.89 27.61 28.98 148.4 37.02 37.27 47.09 31.91 32.02

250.0 250.0 250.0 250.0 250.0 250.0 237.7 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 250.0 106.1 106.1 101.7 101.7 14229 14229 179.6 179.6 1300 1300 1300 1300 130.0 130.0 130.0 1300 1300 120.0 120.0 120.0 1300

117.5 4.307 14.81 14.81 19.11 19.11 19.11 19.11 285.2 0.0000 9261 9261 0.0000 9378 0.0000 9378 280.4 9098 8976 122.4 0.8021 0.0000 123.2 123.2 123.2 123.2 123.2 22.77 22.77 22.77 22.77 222.2 26.66 26.66 26.66 26.66 26.66 26.66 195.5 195.5 195.5 222.2 222.2 222.2

313 314 315 316 317 318 319 320 321 322 323 400 401 402 403 404 405 406 407 408 409 410 416 417 418 419 420 421 423 424 425 426 427 429 430 431 433 435 437 438 NG NG1 AIR Water

25.00 30.00 25.00 30.00 129.2 148.4 101.5 45.49 45.49 25.00 30.00 77.45 56.01 67.96 56.39 67.96 67.96 62.92 56.02 64.51 64.50 64.50 60.96 57.24 58.00 56.02 60.96 58.64 58.64 58.64 58.64 56.39 56.39 56.58 52.17 25.00 56.00 56.00 56.00 56.39 15.00 20.00 15.00 25.00

103.2 103.2 103.2 103.2 1300 1300 1300 1300 1300 103.2 103.2 18.22 29.93 25.93 15.22 25.93 25.93 22.93 26.12 22.12 22.12 22.12 18.73 15.73 16.73 20.73 18.73 16.73 16.73 16.73 16.73 15.22 15.22 15.22 12.22 101.3 97.32 97.32 97.32 37.00 101.3 101.4 101.4 101.3

1483 1483 2254 2254 223.9 28.43 34.54 34.54 7.872 778.0 778.0 11.32 24.40 24.40 11.32 11.12 13.28 11.12 24.40 24.40 37.69 10.89 10.89 10.89 24.40 24.40 40.31 64.72 64.58 0.1263 0.0081 0.1245 11.19 33.04 33.04 53.64 97.63 24.40 24.40 11.19 4.307 0.8021 117.5 14.81

Released heat duty from the Reformer, is sent to the Catalytic burner. Produced H2 (stream 106) enters E102 heat exchanger and its temperature reaches to 492  C (stream 107). Stream 116 that comes from the Splitter, with stream107 are sent to the Anode. Unreacted fuel leaves the anode (stream 108) and is mixed with stream118. Stream110 at 742.3  C and 250 kPa with 9261 kg/s mass flow rate enters the Catalytic burner. Stream111 is mixed with compressed air (stream100) that its pressure reaches to 250 kPa Stream113 at 744.4  C and 250 kPa with flow rate of 9378 kg/s is fed to the cathode. Stream115 goes to the Splitter and is divided into two parts. Stream116 is recycled to the anode and stream 117 goes to the Combustion chamber. Stream 119 before entering GT100 turbine, is mixed with natural gas in the Combustion chamber and burns completely. Stream NG1 at 15  C and 101.4 kPa with the flow rate of 0.8021 kg/s enters C3 compressor and its pressure and temperature reach to 250 kPa and 106.6  C (stream 120). Stream 122 at 952.2  C and 250 kPa enters GT100 turbine. Stream 123 leaves the turbine at 106.1 kPa and enters E101 heat exchanger. After exchanging heat with carbonate ion stream, temperature of the outlet stream (stream 124) reaches to 528.29  C and is sent to the Generator to supply the required heat for absorption refrigeration cycle. Table 3 presents specifications of the carbonate ion. Also, GT101 is a gas turbine which supply a portion of the required

power. Toluene stream (stream 202) at 682.2  C and 179.6 kPa enters E100 heat exchanger. Temperature of the outlet stream (stream 203) reaches to 31.06  C and enters P102 pump. Stream 200 at 14229 kPa is sent to E101. Stream 201 at 795  C and 14229 kPa enters the turbine to produce power. Stream 202 leaves the turbine at 179.6 kPa and enters E100 heat exchanger. 2.1.2. Absorption refrigeration cycle (ARC) modeling In this cycle, NH3/H2O solution is used instead of LiBr/H2O as the working fluid, because of three reasons: providing lower refrigeration temperatures, specific volume of the ammonia is low at high pressures and no concern for crystallization (Deng et al., 2011). This cycle operates at a pressure range of 120e1300 kPa. Also, this subsystem consists of a generator, purifier, condenser, evaporator, absorbent, heat exchangers, pumps and valves. Stream 124 at 528.2  C and 106.1 kPa with flow rate of 123.2 kg/s enter the Generator. In the Generator, water is separated from the ammonia (Ghorbani et al., 2018c). Stream300 at 123.2  C and 1300 kPa is sent to the T100 absorber. Steams 317 and 319 leave the bottom and top of the absorber, respectively. Stream 317 with 22.5% mole NH3 enters the Generator and after exchanging heat, most of the water of the solution is evaporated and stream 307 with 84.5% mole H2O is sent to E104 heat exchanger. Stream318 goes to the T100 at

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Table 2 Composition of the important developed integrated process streams. Stream

CH4

CO

CO2

N2

O2

H2O

H2

C2H6

C7H8

Carbonate ion*

NG AIR Water 108 110 11 1 113 115 116 117 122 `200

0.927 0 0 0.002 0 0

0.008 0 0 0.020 0.0004 0.0001

0.009 0 0 0.081 0.002 0.002

0.015 0.790 0 0.0006 0.661 0.662

0 0.210 0 0 0.055 0.054

0 0 1 0.146 0.267 0.268

0.005 0 0 0.066 0.002 0.0003

0.034 0 0 0.002 0.002 0.0003

0 0 0 0 0 0

0 0 0 0.682 0.011 0.011

0 0 0 0 0 0

0.0001 0.0001 0 0.0001 0 0

0.002 0.0002 0 0.0002 0.011 0

0.663 0.664 0 0.673 0.666 0

0.056 0.055 0 0.056 0.035 0

0.265 0.266 0 0.269 0.287 0

0.0003 0.0003 0 0.0003 0 0

0.0003 0.002 0 0.002 0.002 0

0 0 0 0 0 1

0.011 0.013 1 0 0 0

Stream

NH3

H2O

NaCl

300 301 307 313 315 317 318 319 321 322 400 402 405 408 411 415 418 430 431

0.261 0.999 0.155 0 0 0.225 0.689 0.947 0.767 0 0 0 0 0 0 0 0 0 0

0.739 0.001 0.845 1 1 0.775 0.311 0.053 0.233 1 1 0.987 0.977 0.961 0.929 0.944 0.987 1 0.0124

0 0 0 0 0 0 0 0 0 0 0 0.013 0.023 0.039 0.071 0.056 0.124 0 0.9876

V2 valve, its pressure reaches to 130 kPa (stream304). In chiller 32090 kW refrigeration duty is produced and then stream305 goes to E107 heat exchanger. Outlet stream of the E104 heat exchanger after passing through V1 valve at 37.27  C and 120 kPa (stream309) is mixed with stream306. Stream 310 at 47.09  C and 120 kPa sent to E103 heat exchanger. Stream311 at 31.91  C and 120 kPa is sent to P103 pump and its pressure increases to operating pressure of the absorber. COP of the cycle is gained 0.4915 and can be expressed as equation (7) (Li et al., 2016).

COP ¼

Fig. 2. Validation of the MCFC electrochemical model with references ((Mehrpooya et al., 2017b), (Milewski et al., 2014)).

148.4  C with 68.9% mole NH3. Stream319 with 94.7% mole NH3 is sent to the E105 heat exchanger and after exchanging heat with the liquid water stream, its temperature reaches to 45.49  C. Now, stream320 enters the D5 flash drum in order to separate remained water from the ammonia stream. Stream 321 is recycled to the T100 and stream301 enters the condenser (E106 heat exchanger). Stream 301 temperature, after condensation, reduces to 33.98  C and goes to the E107 heat exchanger (stream302). Stream303 at 10  C and 1300kpa leaves the E107 heat exchanger and after passing through

Q_ evaporator _ pump Q_ geneator þ W

(7)

_ pump ðkWÞ are evapWhere Q_ evaporator ðkWÞ , Q_ geneator ðkWÞ and W orator duty, generator refrigeration duty and pump power, respectively. Results of ABC simulation is compared with reported data in (Niasar and Amidpour, 2018). As shown in Fig. 3, there is an acceptable agreement between the simulated model and results of this study. 2.1.3. Multi-effect desalination (MED) modeling Multi-effect desalination system is a thermal process which operates under vacuum condition and is the main method for production of potable water from the sea water (Shahzad et al., 2014). Generally, the required heat for this process is supplied by exhausted heat from a power plant (Ghorbani et al., 2018a). This process has multiple stages that operate by condensation of the salty water vapors. This system includes several evaporators, flash drums and a thermal ejector for creating a vacuum. In this process,

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analyzing the multi-effect desalination system are expressed (Meratizaman et al., 2015). Ttemperature difference can be considered constant through all effects and is defined by equation (8):

Table 3 Specifications of the carbonate ion in the developed integrated process. Carbonate ion* Base Properties Molecular Weight Normal Boiling Pt  (C) Ideal Liq Density (kg/m3) Critical Properties Temperature  (C) Pressure (bar) Volume (m3/kgmole) Acentricity

60 333.6 858.3 513.8 14.98 0.993 0.719

DT ¼

Ts  TN N

Where, Ts ( C), TN ( C) and N are the first stage temperature, last stage temperature and number of effects, respectively.

T1 ¼ Ts  DT Tiþ1 ¼ Ti  DT

Fig. 3. Validation of the ABC model with (Niasar and Amidpour, 2018).

two streams are fed to the system: sea water and steam. According to Fig. 2, seawater (stream431) at 25  C and 1 bar with the flow rate of 53.64 kg/s firstly is sent to E113 heat exchanger for preheating. By preheating, the produced fresh water being cooler. After exchanging heat with steam, its temperature reaches to 56  C (stream432). Next, the feed water enters stages of the desalination system. In the primary stage, salty water after passing through V6 valve is sent to E109 heat exchanger. After exchanging heat with the steam (stream400), stream 402 at 67.96  C is sent to D1 flash drum. Also, stream 403 is divided into two streams, 426 and 427. Stream 426 is mixed with other condensed water streams. Stream 427 is sent to the P101 pump. In the flash drum, because of the snap pressure drop, steam is formed. This steam, stream 404, enters E110 heat exchanger (second stage) and by exchanging heat with stream 407 (salty water) is condensed (stream406). Stream 405 with 2.3% mole NaCl leaves the bottom of the D1 and is mixed with stream 408. The stream410 enters E111 heat exchanger to condense and stream 411 with 7.1% mole NaCl is mixed with stream 413. Stream 415 at 60.95  C with 5.6% mole NaCl is sent to 3rd stage (D3 flash drum). The stream 416 is sent to E112 heat exchanger to condense and its temperature reaches to 57.24  C (stream417). Salty water after exchanging heat with steam is mixed with stream 420 and next, stream 421 goes to ] last stage (D4 flash drum). Finally, the produced fresh waters are mixed and after exchanging heat in E113 heat exchanger enter desalination water tank. E108 heat exchanger is utilized for supplying the primary stage thermal steam. Stream 422 at 58.64  C and 16.73 kPa goes to the steam ejector. In addition to stream 422, some of the formed steam (stream 424) from the final stage is sent to the steam ejector. In this part, by reducing the cross section, velocity of the steam increases and comes to supersonic. After crossing the bottleneck, goes to the divergent section and by increasing the cross-section, pressure of the steam increases. Finally, stream 400 at 77.45  C and 18.22 kPa with the flow rate of 11.32 kg/s mass is sent to E109 heat exchanger (primary stage of the desalination). In following, relations utilized for

(8)

(9a) i ¼ 2:::N

(9b)

F ¼ B1 þ D 1

(10a)

xf F ¼ xb1 B

(10b)

F ¼ Bi  Bi1 þ Di

(11a)

xf F ¼ xbi Bi xbi1 Bi1

(11b)

In these relations, F (kg/s), B (kg/s) and D (kg/s) are mass flow rates of the fresh water, waste water and salty water, respectively. Also, x, f, b, and i are salinity percentage of each effect, salty water, wastewater and number of effect, respectively. The required thermal vapor at the primary effect is Q and is supplied by the power plant. So energy balances for the first effect and effects 2 to N can be expressed as follows:

  Q1 ¼ ms ðhsout  hsin Þ ¼ FCp T1  Tf þ D1 lv1

(12)

  Qi ¼ ðDi1 þ di1 Þlvi1 ¼ FCp Ti  Tf þ Di lvi þ Bi1 Cp ðTi1  Ti Þ i ¼ 2; ::; N (13) In the above balances, h (kJ/kg) and di (kg/s) are related to the specific enthalpy and mass flow rate of the formed steam in the flash drum, respectively. Also, d and s are formed steam in each step and thermal vapor in the primary effect, respectively. di can be computed as follows:

di ¼ Di1 Cp

T

00

i

 00  Tvi1  T i

lvi

¼ Tvi þ ðNEAÞi

ðNEAÞi ¼

33ðTi1 Ti Þ0:55 Tvi

(14a)

(14b)

(14c)

Where Tv ( CÞ and 00 ( CÞ are steam temperature and potable water temperature generated in the previous effects, respectively. NEA is abbreviation of the non-equilibrium allowance amount. Entrainment ratio (Ra) is utilized for analyzing the steam ejector performance and can be defined as follows (Shakib et al., 2010):

PCF ¼ 3
107 ðPms Þ2  9
104 ðPms Þ þ 1:6101

(15a)

TCF ¼ 2
108 ðTev Þ2  6
104 ðTev Þ þ 1:0047

(15b)

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AIR 15 ºC, 1 bar, 117.6 kg/s

Salt Water Holding Tank

Power 18146 kW

MoltenCarbonate Fuel Cell

Sea Water 25 ºC, 101.3 kPa, 53.64 kg/s

Heat Duty 27939 kW

Heat Duty 205573 kW

Natural Gas 15 ºC, 1 bar, 54.44 kg/s

Multiple-Effect Desalination

Power Plant Power 14866 kW

Power 72000 kW

1045

Power 0.3916 kW

Heat Duty

Power 346.6 kW

64945 kW

Desalinated Water 52.17 ºC, 12.22 kPa, 33.04 kg/s

Brine 58.64 ºC, 16.73 kPa, 64.58 kg/s

Absorption Refrigeration System Refrigeration 32090 kW, -27.89 ºC, 1.3 bar Fig. 4. Block diagram of the developed integrated process.

Table 4 Specifications of the developed integrated process components. Pump & Compressor

P100 P101 P102 P103 C1 C2 C3 Turbine GT100 GT101

Adiabatic Eff.

Power(kW)

DP (kPa)

P ratio ()

75%

3.652

149.0

2.475

75% 75% 75% 75% 75%

496.9 346.6 13394 809.2 162.4

14050 1180 148.6 148.6 148.6

79.23 10.83 2.465 2.467 2.465

70% 70%

26880 6132

143.8 14050

0.4245 0.0126

Heat Exchanger Min. Approach (ºC)

LMTD (ºC)

Duty (kW)

Cold Pinch Temp. (ºC)

E100 E101 E102 E103 E104 E105 E106 E107 E108 E109 E110 E111 E112 E113

6.042 7.32 46.12 6.914 5.00 20.49 5.141 5.121 5.439 3.733 3.456 3.542 3.224 2.579

32.12 19.42 56.32 11.08 10.81 39.57 17.23 19.18 17.36 12.83 14.98 13.75 19.65 16.99

40574 46210 6057 48617 99160 16779 32000 5681 27939 28248 27226 26736 211.2 7254

25.02 795.0 298.0 25.00 32.02 25.00 29.00 28.97 56.39 56.01 64.51 60.96 56.01 56.00

Reboiler

Duty(kW)

Volume (m3)

Diameter (m)

Length (m)

E114

64945

2

1.193

1.789

Ejector Ejector

Suction Nozzle Size (mm)

Motive Nozzle Size (mm)

Discharge Nozzle Size (mm)

Pressure Drop (kPa)

200

250

300

18.80

Number of stages

Feed stage

Tray/Packed Space (m)

Tray/Packed Volume (m3)

5

3

0.5500

0.9719

Column

T100

1046

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Table 5 Specifications of the multi-effect desalination subsystem in the developed integrated process. Parameter

Value

Unit

Total water product Number of effects Steam temperture at final stage Gain output ratio Ratio of the sea water to desalinated water The total received heat Electricity consumption The entrainment ratio of steam ejector Total brine

118944 4 58.64 2.918 1.623 27939 0.3916 2.519 232517

kg/h e ºC kg.hr1/kg.hr1 kg.hr1/kg.hr1 kW W kg.hr1/kg.hr1 kg/h

Ra ¼

   p1:19 PCF mms pms 0:015 ¼ 0:296 hs 1:04 TCF mev pev pev

(15c)

Where PCF (Pa) and TCF (K) are pressure correction factor and temperature correction factor, respectively. Also, mass flow rate of the heating vapor can be computed as follows:

mev ¼ mhs  mms

(16a)

  1 mhs ¼ mms 1 þ Ra

(16b)

Fig. 4 indicates relationship between subsystems of the simultaneous power generation, refrigeration and desalination system.

Table 6 Specifications of the absorption refrigeration cycle in the developed integrated process. Parameter

Value

Unit

Low pressure High pressure NH3 concentration in the strong solution NH3 concentration in the weak solution Absorber refrigeration duty Condenser refrigeration duty Generator refrigeration duty Evaporator refrigeration duty Rectifier heating load Ammonia temperature in the evaporator Pump power consumption Purity of ammonia flow at evaporator COP

120 1300 25 14.78 48617 32000 64945 32090 16779 27.89 346.6 99.90 0.4915

kPa kPa Mass fractions% Mass fractions% kW kW kW kW kW ºC kW Mass fractions % e

Table 7 Specifications of the molten carbonate fuel cell subsystem in the developed integrated process. Parameter

Value

Parameter

Value

(Stream 113)

744.4  C

Current

150265617 A 15  C

Inlet Oxidant temperature (Stream 105) Inlet air pressure Power output Fuel utilization Current density Cell voltage Power per cm2 Effective area per cell



298 C 2.5 bar 72000 kW 0.8 0.1928 A/ cm2 0.52 V 0.09355 W/ cm2 100 cm2

Ambient temperature Ambient pressure Anode thickness Cathode thickness Electrolyte thickness Inverter Efficiency Cell number

1 bar 0.0008 m 0.00004 m 0.000035 m 0. 9 7793979

2.2. Simulation The proposed process is simulated by HYSYS and MATLAB softwares. Peng-Robinson (PR) is used for calculation of the thermodynamic properties of the process (Peng and Robinson, 1976). The main assumptions considered in this simulation, can be expressed as follows:    

This hybrid system operates under steady state conditions. Variations of the potential and kinetic energies are neglected. 25  C and 1 bar are considered as the dead state. A constant adiabatic efficiency is considered for compressors (75%) and pumps (70%).  Steam formed in each unit of the desalination subsystem, has no salt (Ghorbani et al., 2018a).  Heat loss from the desalination subsystem is negligible [19]. 3. Exergy analysis Exergy evaluation is based on the second law of thermodynamics (Sheikhi et al., 2014). Exergy analysis is performed in order to evaluate quality of the energy and irreversibility of a system (Sheikhi et al., 2015). Exergy can be defined as the maximum useful work which is achieved when the system reaches to the standard state (25  C, 1atm)(Cengel and Boles, 2002). The material stream exergy is splitted into four parts: chemical exergy, physical exergy, kinetic exergy and potential exergy (Fabrega et al., 2010). Exergy destruction can be expressed as follows (Sonntag et al., 1998):

_ ¼ T S_ Ex D 0 gen

(17)

In this equation, T0 (K) and S_gen (kW/K) are temperature of the standard conditions and entropy generation, respectively. Exergy efficiency is expressed as (product exergy rate)/(fuel exergy rate) concept which can be formulated as follows (18).

Table 8 Different definitions of the process efficiency. Parameter Final electrical efficiency (HHV Base) Final electrical efficiency (LHV Base) Overall thermal efficiency (HHV Base) Overall thermal efficiency (LHV Base)

Equation

helec;HHV

Value (%) _ _ _ _ W Turbine100;101 þ W MCFC  W Compressur1;2;3  W Pump101;102;103 ¼ m_ fuel
HHVfuel

40.06

_ _ _ _ W Turbine100;101 þ W MCFC  W Compressur1;2;3  W Pump101;102;103 m_ fuel
LHVfuel

44.44

helec;LHV ¼

hthermal;HHV ¼ hthermal;LHV ¼

_ _ _ _ _ W MCFC þ W Turbine100;101 þ W equal;Absorbtion  W Compressur1;2;3  W Pumps100;101;102;103 m_ fuel
HHVfuel _ _ _ _ _ W þW þW W W MCFC

Turbine100;101

equal;Absorbtion

Compressur1;2;3

m_ fuel
LHVfuel

Pumps100;101;102;103

54.37 60.32

B. Ghorbani et al. / Journal of Cleaner Production 220 (2019) 1039e1051

hex ¼

1047

eph ¼ ðh  h0 Þ  T0 ðs  s0 Þ

_ Ex P

(18)

_D _ or h ¼ 1  Ex Ex F ex _

ech ¼

ExF

_ ðkWÞ ; Ex _ ðkWÞ and Ex _ ðkWÞ are production exergy Where, Ex P F D rate, fuel exergy rate and exergy destruction rate, respectively. Exergy of the material stream that consists of four terms and is expressed as follows (Soufiyan et al., 2017):

e ¼ eK þ eP þ ePh þ ech

X

e ¼ ePh þ ech

(20)

Specific physical and chemical exergies can be written as follows (Ghorbani and Roshani, 2018):

X

xi Gi

(22)

In these relations, h0 (kJ/kg) and s0 (kJ/kg) are specific enthalpy and specific entropy at dead state. Also xi is mole fraction, e0i ðkJ/ kgmol) is standard chemical exergy of component i and G (kJ/ kgmol) is the Gibbs free energy. Rate of exergy of the heat stream can be calculated by equation (23) (Soufiyan et al., 2016):

(19)

Where, eK (kJ/kg), eP (kJ/kg), ePh (kJ/kg) and ech (kJ/kg) are specific kinetic exergy, potential exergy, physical exergy and chemical exergy, respectively. By neglecting kinetic and potential terms, specific exergy can be expressed as follows:

xi e0i þ G 

(21)

_ Ex Q ¼

! T0 _ 1 Q Tj

(23)

In this equation, Q_ (kW) is rate of the heat transfer that occurs at Tj (K). For a system under steady state conditions, exergy balance for each equipment can be written as follows (SHARIATI et al., 2017):

_ _ _ _ _ _ Ex in þ ExQin ¼ Exout þ ExQout þ W shaft þ ExD

(24)

Table 9 Physical, chemical and total exergy rate of each stream of the development integrated process. Stream No.

Physical Exergy Rate (kW) Chemical Exergy Rate (kW) Total Stream Exergy Rate (kW) No.

100 101 102 103 104 105 106 107 108 110 111 113 114 115 116 117 118 119 120 122 123 124 125 126 200 201 202 203 300 301 302 303 304 305 306 307 308 309 310 311 312 313

10834 645 3 9645 8827 11235 18515 14810 548568 5650734 5728088 5723624 0 5610662 450448 5221994 5150941 70254 130 100322 70138 38713 6922 3097 426 25417 18446 5 15541 9544 8578 8840 8685 1769 960 18369 494 217 2303 80 423 3

656 210477 2565 2565 213022 213022 225209 225209 11604411 12923356 12797910 12797305 0 14525134 13172572 1352587 1333908 18193 41827 18763 18763 18763 18763 18763 977095 977095 977095 977095 1130287 533854 533854 533854 533854 533854 533854 598458 598458 598458 1130287 1130287 1130287 256977

11491 211121 2568 12211 221849 224257 243724 240019 12152979 18574090 18525998 18520929 0 20135795 13623020 6574581 6484849 88448 41957 119084 88901 57476 25685 21860 977521 1002512 995541 977100 1145828 543398 542432 542694 542539 535624 534814 616827 598952 598675 1132589 1130366 1130709 256980

314 315 316 317 318 319 320 321 322 323 400 401 402 403 404 405 406 407 408 409 410 416 417 418 419 420 421 423 424 425 426 427 429 430 431 433 435 437 438 NG NG1 AIR

Physical Exergy Rate (kW) Chemical Exergy Rate (kW) Total Exergy Rate (kW) 268 5 407 15660 13648 13021 10782 1179 2 140 3074 159 3699 78 3531 158 111 158 3336 3492 3212 2954 2672 179 158 340 517 483 32 2 1 77 2826 1884 0 641 160 160 77 2 0 28

256977 390410 390410 984087 387050 653336 653336 119501 134742 134742 42588 83915 83915 42588 41846 42078 41846 83915 83915 125994 40978 40967 40967 83915 83915 127982 211899 211393 475 30 468 42120 124290 124290 184428 335660 83915 83915 42120 210477 41827 656

257245 390415 390817 999748 400698 666357 664118 120680 134744 134882 45662 84073 87614 42666 45377 42236 41957 84073 87250 129486 44190 43921 43639 84094 84073 128322 212416 211876 507 32 469 42196 127116 126174 184428 336301 84075 84075 42197 210478 41827 684

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4. Results and discussion

4.1. Energy analysis

In this part, results of the energy, exergy and sensitivity assessment are presented in tables and figures. Also, analyses and discussion of the results is performed.

Table 4 presents specifications of the process components. The highest and lowest power consumption is related to C1 (13394 kW) and C2 (809.2 kW) compressors, respectively. Among the heat exchangers, E104 in the ARC subsystem, has the highest

Table 10 Specifications of the input, output and destroyed exergy rate in the developed integrated process equipment. Components

E_ F ðkWÞ

E_ P ðkWÞ

E_ D ðkWÞ

Components

E_ F ðkWÞ

E_ P ðkWÞ

E_ D ðkWÞ

E100 E101 E102 E103 E104 E105 E106 E107 E108 E109 E110 E111 E112 E113 E114 C1 C2 C3 GT100 GT101

998109 1066422 465573 1523004 1747537 801101 800379 1078055 68108 130279 129451 128263 127994 311545 1057224 14078 211288 41990 119084 1002512

989310 1059988 464276 1521183 1744780 799000 799677 1077508 67882 129736 129207 128020 127733 310955 1043210 11491 211121 41957 115781 1001673

8799 6434 1297 1821 2757 2100 702 547 227 544 243 244 262 590 14013 2587 166 33 3304 839

P100 P101 P102 P103 D1 D2 D3 D4 D5 MCFC Reformer Combustion V1 V2 V3 V4 V5 V6 T100 Ejector

2569 42197 977596 1130713 87614 129486 172243 212416 664118 251510 19467 130405 598952 542694 84075 84075 84075 84075 20490 46756

2568 42197 977521 1130709 87614 129486 172243 212416 664078 160450 16250 119084 598675 542539 84073 84073 84073 84073 14398 45662

0.709 0.088 75.05 3.411 0.025 0.006 0.012 0.0148 39.7 91062 3216 11320 277.3 155.3 1.877 1.966 2.019 1.776 6092 1093

Table 11 The exergy efficiency of the developed integrated process components. Components and exergy efficiency expression

Component identifier Exergy efficiency (%) Component identifier Exergy efficiency (%)

Heat Exchangers "P # Pm n _ _ ðmDeÞ 1 ðmDeÞ hex ¼ 1   Pm Pn1 _ _ 1 ðmDhÞ h 1 ðmDhÞ c

E100 E101 E102 E103 E104 E105 E106 E107 C1 C2 P100 P102

78.32 86.08 60.26 96.25 97.22 87.48 97.81 90.36 80.68 79.45 80.26 84.90

E108 E109 E110 E111 E112 E113 E114

96.19 98.08 97.11 95.16 93.22 91.87 98.67

C3

79.82

P101 P103

77.45 96.02

GT100

89.05

GT101

87.97

76.32 61.27 50.46

V4 V5 V6

46.17 67.16 57.12

83.47

Combustion

91.32

Compressors(Ghorbani et al., 2016b) P P _ o _ i ðm:eÞ ðm:eÞ hex ¼ W Pumps (Ghorbani et al., 2016a) P P _ o _ i ðm:eÞ ðm:eÞ hex ¼ W Turbines W P hex ¼ P _ i _ o ðm:eÞ ðm:eÞ Ejector P _ o ðm:eÞ hex ¼ P _ i ðm:eÞ Expansion valves T R T T  T0 eDT  eD i dh ePh ¼ eDT þ eDp , hex ¼ oDp eDT ¼ T 0 p T ei  eD o

97.66

V1 V2 V3

Reactors P

Reformer _ o ðm:eÞ _ i ðm:eÞ 70.27 Column (Sheikhi et al., 2014) P P Wmin Wmin ¼ hex ¼ Ex  ExLW ¼ T0 DSirr ¼ Lost Work Wmin þ LW in to stream Out of stream

hex ¼ P

MCFC(Ghorbani et al., 2018e) P _ o ðm:eÞ hex ¼ P _ i ðm:eÞ Overall Exergy efficiency Total irreversibility in cycle hex ¼ 1  Total consumed power in cycle

63.79

88.95

B. Ghorbani et al. / Journal of Cleaner Production 220 (2019) 1039e1051

1049

heat duty by 99160 kW. Table 5 illustrates specifications of the multi-effect desalination subsystem in the process. This system can provide 118944 kg/h fresh water by consuming 0.3916 W electricity and receiving 27939 kW heat. Table 6 indicates specifications of the absorption refrigeration cycle in the process. This ARC system utilizes exhausted heat from the power plant. This cycle can provide 32090 kW refrigeration duty at 27.89  C, by consuming 346.6 kW power by P103 pump. Also COP of the cycle is gained 0.4915. Table 7 presents specifications of the molten carbonate fuel cell subsystem. This subsystem is the major power generation source by producing 72000 kW power. Table 8 depicts the overall electrical and overall thermal efficiencies of process, based on the higher heating value (HHV) and lower heating value (LHV) definitions. Fig. 5. Exergy destruction pie chart in the various equipment of the developed integrated process.

4.2. Exergy analysis The main purpose of exergy analysis is to determine the location and amount of irreversibilities in the processes. For comparing performance of the process equipment, exergy destruction rate and exergy efficiency should be calculated. Next, it is possible to propose solutions such as changing operating conditions, replacing equipment with more suitable items and changing structure of the process, in order to reduce irreversibility and increase exergy efficiency. The exergy efficiency of the expansion valves is lower than other equipment of the developed integrated process. However, they have a low exergy destruction rate. It can be seen that, performance of the components should be analyzed simultaneously for irreversibility and exergy efficiency. Table 9 indicates the physical, chemical and total exergy rate of the developed integrated process streams. It is found that, streams 115 and 110 have the greatest total exergy rates by 20135795 and 18574090 kW, respectively. Table 10 presents the inlet, outlet and destroyed exergy rates of the equipment. According to this table, MCFC and D2 flash drum have the highest (91062 kW) and lowest (0.006 kW) exergy destruction rate, respectively. Also among the heat exchangers, E114 with 14013 kW has the greatest exergy destruction rate and the lowest exergy destruction rate occurs in E108 with 227 kW. Among the compressors, the greatest exergy destruction rate is related to C1 by 2587 kW. P102 has the highest irreversibility, among the pumps by 75.05 kW. Among the flash drums and expansion valves, D5 (39.7 kW) and V1 (277.3 kW) have the highest exergy destruction rate. Table 11 illustrates exergy efficiencies of the developed integrated process equipment. Expansion valves and heat exchangers have the lowest and highest exergy efficiency than other components, respectively. The highest exergy efficiency belongs to E114 heat exchanger by 98.67%, followed by the E109 (98.08%), E106 (97.81%) and E104 (97.22%) heat exchangers. The least exergy efficiency is related to V4 expansion valve with the value of 46.17%. Also, overall exergy efficiency is gained 88.95% that indicates the proposed process has an acceptable performance. Fig. 5 demonstrates the percentile contributions of the developed integrated process equipment to the exergy destruction rate. MCFC has the highest contribution (56.6%) to the exergy destruction rate. The next largest contributions are related to the heat exchangers (25.2%) and Combustion chamber (7%), respectively. Fig. 6 illustrates the percentile contributions of the heat exchangers to the exergy destruction rate. The greatest contribution is related to the E114 (34.5%). The next highest contributions is related to E100 (21.6%), E101 (15.8%) and E104 (6.7%), respectively. Fig. 7 shows exergy destruction rate of each subsystem per total exergy destruction rate. The highest irreversibility is related to the molten carbonate fuel cell subsystem (62.25%).

Fig. 6. Exergy destruction pie chart in the heat exchangers of the developed integrated process.

4.3. Sensitivity analysis Fig. 8 illustrates variations of the overall thermal efficiency and MCFC output power in the developed integrated process versus fuel utilization factor in molten carbonate fuel cell. By increasing the fuel utilization factor in constant inlet fuel mass flow rate, the amount of consumed hydrogen (H2) increases and exhaust gasses from the fuel cell reduces. However, due to high temperature of the exhaust gases and natural gas injection in the combustion chamber, overall thermal efficiency and MCFC output power increases by fuel utilization factor (Uf). Fig. 9 indicates variations of the overall thermal efficiency and final electrical efficiency in the process versus fuel utilization factor in MCFC. By increasing the fuel utilization factor (Uf), in constant inlet fuel mass flow rate, overall thermal efficiency and final electrical efficiency increases. Fig. 10 demonstrates variations of the overall exergy efficiency and total irreversibility in the developed integrated process versus mole fraction of the methane in NG. By increasing mole fraction of the NG feed, heat value increases. So, for a constant current density in the anode of the fuel cell, fuel utilization coefficient (Uf) must be reduced. Also by increasing heat value of the natural gas and reducing the fuel utilization coefficient, exhaust gas from the fuel cell, includes more amount of methane for burning in the catalytic burner. So exhaust gas from the combustion chamber can produce more power in GT100 turbine. Since increasing power generation of the integrated process is more than increasing the heat value, so

1050

B. Ghorbani et al. / Journal of Cleaner Production 220 (2019) 1039e1051

Fig. 10. Variations of overall exergy efficiency and total irreversibility in the developed integrated process versus diverse mole fraction of the methane in NG feed. Fig. 7. The exergy destruction of each subsystems per total exergy destruction of the developed integrated process.

with the increase of mole fraction of the methane in NG feed, overall exergy efficiency increases and total irreversibility decreases. Fig. 11 shows variations of the refrigeration duty and mass flow rate of the desalinated water versus mole fraction of the methane. Exhausted gas leaves the gas turbine at a higher temperature by increasing amount of the methane in natural gas. Therefore, it is more capable for supplying the required heat in the absorption refrigeration cycle and multi-effect desalination subsystems.

5. Conclusion In this paper, an integrated system of simultaneous power generation, refrigeration and desalination cycle, by using molten carbonate fuel cell is proposed and evaluated. The main outcomes obtained, can be listed as follows:

Fig. 8. Changes of the overall thermal efficiency and MCFC output power in the developed integrated process according to the changes in fuel utilization factor (Uf).

Fig. 9. Variations of overall exergy efficiency and total irreversibility in the developed integrated process versus diverse mole fraction of the methane in NG feed.

 This hybrid system can provide 18146 kW net power, 32090 kW refrigeration duty and 33.04 kg/s potable water.  Final electrical efficiency of the process, based on HHV and LHV is 40.06% and 44.44%, respectively.  Overall thermal efficiency of the system, based on HHV and LHV is 54.37% and 60.32%, respectively.

Fig. 11. Variations of the refrigeration duty and mass flow rate of the desalinated water versus diverse mole fraction of the methane in NG feed.

B. Ghorbani et al. / Journal of Cleaner Production 220 (2019) 1039e1051

 Hhighest and lowest exergy efficiencies are related to Generator (98.67%) and V4 expansion valve (46.17%), respectively.  Overall exergy efficiency of the process is 88.95%, which shows most of the equipment of the process have an acceptable performance.  The greatest exergy destruction rate occurs in molten carbonate fuel cell (MCFC) (91062 kW), followed by E114 heat exchanger (14013 kW) and Combustion chamber (11320 kW). So, how to reduce irreversibility rate in these equipment can improve energy saving of the process.  By increasing the fuel utilization factor, output power of the MCFC, overall exergy efficiency, overall thermal efficiency (LHV base) and final electrical efficiency (LHV base) increase.  By increasing mole fraction of the methane in NG, overall exergy efficiency, produced refrigeration load and mass flow rate of the desalinated water increase and total irreversibility in the cycle decreases. References Alelyani, S.M., Fette, N.W., Stechel, E.B., Doron, P., Phelan, P.E., 2017. Techno-economic analysis of combined ammonia-water absorption refrigeration and desalination. Energy Convers. Manag. 143, 493e504. Bataineh, K.M., 2016. Multi-effect desalination plant combined with thermal compressor driven by steam generated by solar energy. Desalination 385, 39e52. Cengel, Y.A., Boles, M.A., 2002. Thermodynamics: an engineering approach. Sea 1000, 8862. Costamagna, P., Magistri, L., Massardo, A., 2001. Design and part-load performance of a hybrid system based on a solid oxide fuel cell reactor and a micro gas turbine. J. Power Sources 96 (2), 352e368. Deng, J., Wang, R., Han, G., 2011. A review of thermally activated cooling technologies for combined cooling, heating and power systems. Prog. Energy Combust. Sci. 37 (2), 172e203. Fabrega, F., Rossi, J., d'Angelo, J., 2010. Exergetic analysis of the refrigeration system in ethylene and propylene production process. Energy 35 (3), 1224e1231. Ghaebi, H., Abbaspour, G., 2018. Thermoeconomic analysis of an integrated multieffect desalination thermal vapor compression (MED-TVC) system with a trigeneration system using triple-pressure HRSG. Heat Mass Transf. 54 (5), 1337e1357. Ghorbani, B., Hamedi, M.-H., Amidpour, M., 2016a. Exergoeconomic evaluation of an integrated nitrogen rejection unit with LNG and NGL Co-production processes based on the MFC and absorbtion refrigeration systems. Gas Process. 4 (1), 1e28. Ghorbani, B., Hamedi, M.-H., Amidpour, M., Mehrpooya, M., 2016b. Cascade refrigeration systems in integrated cryogenic natural gas process (natural gas liquids (NGL), liquefied natural gas (LNG) and nitrogen rejection unit (NRU)). Energy 115 (1), 88e106. Ghorbani, B., Mehrpooya, M., Ghasemzadeh, H., 2018a. Investigation of a hybrid water desalination, oxy-fuel power generation and CO 2 liquefaction process. Energy 158, 1105e1119. Ghorbani, B., Mehrpooya, M., Sadeghzadeh, M., 2018b. Developing a tri-generation system of power, heating, and freshwater (for an industrial town) by using solar flat plate collectors, multi-stage desalination unit, and Kalina power generation cycle. Energy Convers. Manag. 165, 113e126. Ghorbani, B., Mehrpooya, M., Shirmohammadi, R., Hamedi, M.-H., 2018c. A comprehensive approach toward utilizing mixed refrigerant and absorption refrigeration systems in an integrated cryogenic refrigeration process. J. Clean. Prod. 179, 495e514. Ghorbani, B., Roshani, H., 2018. Advanced exergy and exergoeconomic analysis of the integrated structure of simultaneous production of NGL recovery and liquefaction. Transp. Phenom. Nano Micro Scales 6, 8e14. Ghorbani, B., Shirmohammadi, R., Mehrpooya, M., 2018d. A novel energy efficient LNG/NGL recovery process using absorption and mixed refrigerant refrigeration cycleseEconomic and exergy analyses. Appl. Therm. Eng. 132, 283e295. Ghorbani, B., Shirmohammadi, R., Mehrpooya, M., Mafi, M., 2018e. Applying an integrated trigeneration incorporating hybrid energy systems for natural gas liquefaction. Energy 149, 848e864. Gude, V.G., Nirmalakhandan, N., 2010. Sustainable desalination using solar energy. Energy Convers. Manag. 51 (11), 2245e2251. Kalinowski, P., Hwang, Y., Radermacher, R., Al Hashimi, S., Rodgers, P., 2009. Application of waste heat powered absorption refrigeration system to the LNG recovery process. Int. J. Refrig. 32 (4), 687e694. Koh, J.-H., Kang, B.S., Lim, H.C., 2000. Effect of various stack parameters on temperature rise in molten carbonate fuel cell stack operation. J. Power Sources 91

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