Natural gas‐fueled multigeneration for reducing environmental effects of brine and increasing product diversity: Thermodynamic and economic analyses

Water scarcity threatens human life and it is likely to be a main concern in the next century. In this work, a novel multigeneration system (MGS) is introduced and assessed with energy, exergy, and economic analyses. This MGS includes a gas cycle, multieffect distillation, an absorption refrigeration cycle, a heat recovery steam generator, and electrodialysis. Electrodialysis is integrated into this configuration to produce sodium hydroxide and hydrogen chloride from brine to prevent its release to the environment with harmful impacts. The other products are electricity, cooling, and demineralized water. For the evaluation of the proposed system, one computer code is provided in engineering equation solver software. For physical properties calculation, the library of this software is used. The MGS produces 614.7 GWh of electrical energy, 87.44 GWh of cooling, 12.47 million m3 of demineralized water, and 0.092 and 0.084 billion kg of sodium hydroxide and hydrogen chloride over a year. Energy and exergy evaluations demonstrate that the MGS energy and exergy efficiencies are 31.3% and 18.7%, respectively. The highest and lowest value of exergy destruction rate is associated with the combustion chamber and pump, respectively. The economic evaluation indicates that the net present value of this proposed system is 3.8 billion US$, while the internal rate of return and payback period, respectively, are 0.49 and 2.1 years.


| INTRODUCTION
Water covers 70% of the earth as lakes, rivers, seas, and oceans, but only 3% of this resource is freshwater. Twothirds of this freshwater is frozen and nonaccessible for use. Thus, the fresh shortage is a considerable issue for humanity. 1 According to statistical data, 2 around 1.2 billion people cannot access adequate water throughout the year. In addition, 2.7 billion people encounter a lack of water for 1 month of a year and 2.4 billion people are exposed to water diseases annually, with 2 million casualties each year. 2 According to terminology, water shortage is usually named water scarcity. Water scarcity means an imbalance between the production and consumption of freshwater. It can happen throughout the year or for a limited time. Water scarcity is a significant concern for humanity since freshwater is an essential requirement for health and life. In addition, nonpotable water is needed for agriculture, industry, and energy production. This need grows as the global population increases. Other environmental and social factors influence water scarcity, including climate change and living standards. 3 Desalination technologies have been developed for over 50 years. Early studies were conducted during World War II and research has continued until now. 4 Desalination processes are classified by approach 5 :

Thermal distillation
This method is based on evaporation and condensation to continuously purify water and separate dissolved solids (DSs), such as salt. 5 This method is common in the Middle East due to the cheap price of oil and natural gas (NG). This method can be divided into multieffect distillation (MED) and multistage flash (MSF).

Membrane separation
This method is based on filtration. Seawater (SW) flows through a membrane and non-DSs are separated from the water. This method does not require any thermal energy and only electrical energy is consumed to meet the electrical energy needs of the reverse osmosis (RO) pumps. This method can be divided into RO 6 and forward osmosis (FO) 7 processes.

Other approaches
Several other desalination methods also exist, such as humidification-dehumidification, 8 membrane distillation, 9 freezing, and solar stills. 10 When comparing thermal distillation and membrane separation, thermal separation is preferred at a large scale due to lower operation and maintenance costs (OMCs) and the possibility to use the energy of hot exhaust gas from various industries. 11 One of the oldest distillation methods is MED. This technology is used on a large scale and has been improved in recent years. In comparison with MSF, MED is preferable due to its low-temperature operation, higher capacity to produce potable water (PW), better heat transfer, and lower electrical power consumption of pumps. 11 One of the disadvantages of the desalination process is the environmental concern of brine disposal. Brine disposal methods can be classified as injection to well, surface water, and land disposal. 12 All of these methods are harmful to the environment, by threatening marine life, degradation of soil and groundwater quality, and so forth. So, the conversion of exhaust brine from the desalination plant to useful and valuable materials has many economic and environmental benefits. 13 A gas turbine (GT) power generation system was introduced 70 years ago. Over the last 20 years, its usage has increased 20-fold, especially in regions with high NG resources. 14 GT power generation systems have two major weaknesses 15 : 1. Low efficiency (~20%-45%) due to the dissipation of exhaust hot gas to the atmosphere. 16 2. Significant effect of air temperature increase on GT efficiency. 17 There are various technologies to fix these defects, such as inlet air cooler systems, bottom cycles to produce extra electrical power by utilizing the hot exhaust gases via a heat recovery steam generator (HRSG), 18 air bottom cycles, 19 integration with renewable energy resources for performance enhancement, 20 integration with other power generation systems, such as solid oxide fuel cells (SOFCs), 21 multigeneration systems (MGSs) for production of various products simultaneously, such as hydrogen, 22 urea, and PW. 23 Thus, integration of MED with a gas cycle (GC) has benefits due to enhancing system performance. It has also further benefits if the portion of the plant downstream of the MED is integrated with a system that converts the brine to useful products to further increase system efficiency and reduce environmental impacts.
Considerable research has been done on MGS, especially the integration of GCs with MED. Mokhtari et al. 24 performed thermoeconomic and exergy evaluations of a GC/MED/RO system. This proposed system produced 79.2 × 10 6 kWh/year of electricity and 10.3 × 10 3 m 3 /day PW. Rensonnet et al. 25 performed a thermoeconomic investigation for four different configurations, including GC/RO, combined cycle (CC) with RO, CC/MED, and CC/ MED/RO. The configuration of CC/MED/RO had the lowest unit cost at 0.15 US$/kWh. Ahmadi et al. 26 evaluated the integration of the MED with a GC (GC capacity of 48 MW). This integration produced 12,294 m 3 /day PW with a 1.6 US$/m 3 cost. The system exergy efficiency was 38.9%. In a similar study, Shakouri et al. 23 evaluated and optimized the integration of GC with MED from an economic point of view. They found that the three-effect MED is the best choice with 0.51 kg/s distilled water (DW) production and 2 US$/m 3 unit product cost.
The integration of SOFC with GC, and MED is another interesting topic. Mohammadnia and Asadi 27 evaluated a hybrid system, including GC, SOFC, HRSG, and MED with a thermal vapor compressor (TVC), in terms of energy, exergy, and economics (3Es). They calculated the gross output ratio (GOR), net output power, DW production, system total product cost (TPC), and system exergy efficiency as 7.6, 3219.3 kW, 3.2 kg/s, 0.02 US$/s, and 59.4%, respectively. In a similar study, Ahmadi et al. 28 performed the exergoeconomic optimization of a system consisting of GC, SOFC, and MED-TVC with a genetic algorithm (GA). The authors determined an increase in the system exergy efficiency from 57% to 63.5% and a drop in the electricity cost to 0.064 US$/kWh. Several systems were proposed as MGS for various products. Nazari and Porkhial 29 proposed an MGS, including GC, organic Rankine cycle (ORC), Rankine cycle (RC), and absorption refrigeration cycle (ARC). This system used NG, biogas (BG), and solar energy via a parabolic trough collector (PTC), simultaneously. The products of the MGS were PW, cooling, and electrical power. The system exergy efficiency and TPC were 21.5%, and 77.3 US$/h, respectively. You et al. 30 assessed an MGS, including GC, MED-TVC, ORC, and steam ejector refrigerator to produce PW, electricity, heating, and cooling. This MGS can produce 31.2 MW of electricity, 1.1 MW of heating, 4.2 MW of cooling, and 85.9 kg/s of PW. The calculated system exergy efficiency is 41.3%. In another study, Moghimi et al. 31 introduced an MGS consisting of GC, HRSG, MED, and an ejector refrigerator system. This MGS produced 85.6 kg/s PW, 2 MW cooling, and 30 MW electricity. The calculated system exergy efficiency is 36%.
Considering the previous studies, the research gap in the literature is as follows: • Treatment of brine discharge downstream of MED to avoid environment harmfully. • Nonuse of brine or converting it to useful products.
In this article, a new MGS consisting of GC, HRSG, MED-TVC, ARC, and electrodialysis (ELECD) is proposed to convert the brine to NaOH and HCl as valuable products. The system products are electricity, cooling, PW, NaOH, and HCl. This MGS is powered by NG. All aspects of this new MGS are examined by 3E analyses. In summary, The novelties of this research are as follows: • Presenting a new multiple production system with the aim of eliminating the environmental effects of brine. • 3E analyses of the proposed system.
2 | MODELING 2.1 | System layout and description Figure 1 illustrates the layout of the proposed MGS. In the GC, NG is compressed in the booster compressor (BC) (points 1 and 2). Then, it is reacted by pressurized air from the compressor (C) (points 3 and 4) in the combustion chamber (CC) to produce hot gas (point 5) that rotates the GT and generator for electrical production (point 6). Then, it flows through the HRSG to produce superheated steam (point 7). After, it flows through the ARC to supply the electricity required by the generator of the ARC and produce cooling (point 8). In the steam cycle (SC), the pressurized water (point 11) exchanges the heat with exhaust GT hot gas to produce the superheated steam (point 9). The superheated steam is injected into the MED/ TVC for DW production from the SW (point 9). After, it goes to pump 1 (P1) (point 10). Figure 2 depicts the layout of the MED. The MED converts the SW (point 12) to DW (point 13) and dissipated brine (point 14). This system operates based on successive evaporation and condensation and has several stages named effects and one condenser. In the MED, TVC works by the superheated steam (point 19: motive steam) and it pressurizes the part of water vapor generated in the last effect (entrained steam). Produced steam supplies the energy needed by MED.
In the first effect of the MED, the exit steam of the TVC goes in the tubes to evaporate the SW sprayed on them in the first effect. The steam in the tubes is condensed. The evaporated SW in the first effect is collected with evaporated brine in the flash boxes and goes into the tubes of the second effect. In flash boxes, a small pressure drop causes a small portion of brine to evaporate. This process continues until the last effect. It is important to mention that number of effects is clarified based on the requested capacity of DW. To improve the performance of the MED, the SW is preheated in the preheater with distillate vapor (DV) in each effect.
Part of the dissipated brine is injected into the ELECD and it is converted to NaOH and HCl by electrolyzing the SW using electricity. This MGS has several subsystems: GC, SC, MED, ARC, and ELECD. The products are electricity, cooling, DW, NaOH, and HCl (points 15 and 16). The EHYAEI ET AL.
| 1027 connections between the subsystems are depicted in Figure 3.
For the modeling, the following assumptions are considered 32 : 1. The reference environment temperature and pressure are 15°C and 101.3 kPa, respectively. 2. Heat loss is ignored. 3. The thermodynamic processes in the C and GT are polytropic. 4. Kinetic and potential energies are ignored. 5. The efficiency of the CC is 98%. 6. For the BC, C, and GT, the polytropic efficiencies are, respectively, 85%, 85%, and 78%. 7. DV and brine have an effective temperature at the exit. 8. The DV is slightly superheated and completely pure. 9. The overall heat transfer coefficients in the MED are a function of temperature. 10. The temperature difference in each effect is assumed equal. 11. The feed water in the MED is distributed equally.

| Energy and mass balance
The combustion reaction in the CC can be written as follows: where x i and y i specify the mass and mole fractions of i and r a depicts the air/fuel ratio. The NG molar composition used in the GC is presented in Table 1. 34 EHYAEI ET AL.

| 1029
The mass and energy balance equations for each component of the GC and SC are presented in Table 2.
The COP and η mean the coefficient of performance (ARC) and efficiency. Subscript HX means heat exchanger.

| Multieffect distillation
The effect of temperature difference is considered as follows 35 : Here, T and N denote the temperature and effects number. The subscript i specifies the number of effects.
The temperature of the vapor inside the effects should be considered as follows 36 : Here, subscript v shows the vapor. Boiling point elevation (BPE) is a factor that determines the salt effect on evaporation. 36 The temperature in the flash boxes can be determined as follows due to nonequilibrium allowance (NEA) 37 : where NEA is determined by 37 The SW mass flow rate in each effect is calculated as follows 35 : Mass and concentration balance relations are as follows 38,39 : where x denotes the salt concentration. The energy balance equation for each effect can be calculated as follows 38,39 : Here, ff and L denote flashing fraction and latent heat, while subscript r means entrained steam.
The overall surface area of each effect, condenser, and preheater is calculated with the following relations 39,40 : T A B L E 2 Mass and energy rate balance equations for the component of the GC and SC

No.
Component Mass balance Energy balance Subscripts cond and ph represent, respectively, condenser and preheater of the MED.
The coefficient U for the effects, cond, and ph of the MED can be expressed, respectively, as follows 39 The ratio of entrained steam (ṁ) N

DV,
to motive steam (m ṁ oṙ) m 9 can be expressed as follows 41 : Ra is calculated by 38 Here, P denotes the pressure.
The TVC outlet stream is described as follows 38 : where subscript s represents the outlet steam of the TVC. For evaluation of the MED, two factors should be calculated named recovery gained output ratio (GOR) and recovery ratio (RR):

| Electrodialysis
In the ELECD, the following reaction takes place driven by electricity 42 : The precondition of this reaction in ELECD is that the salt concentration should exceed 26%. This subsystem requires 0.73 kWh of electrical energy per kilogram of NaOH.

| Energy efficiency (ENE) evaluation
The ENE of the GC, GC/SC/MED/ARC, and system is considered by the following relations:

| Exergy analysis
Specific exergy is divided into four kinds (chemical, kinetic, physical, and potential) as considered below 43,44 : Here, x and Ψ denote the mass fraction and specific exergy, respectively. Also, g is the gravitational acceleration, V and z are the velocity and height, y and s denote the mole fraction and specific entropy, and subscripts 0, i, and ch denote dead state, species, and chemical, respectively. Table 3 shows the EDR for each component of the MGS.

| Exergy efficiency evaluation
The exergy efficiency of the GC, GC/SC/MED/ARC, and the system can be written as follows:

| Economic investigation
The annual income (AI) of this proposed system is calculated based on product sales over a year minus the cost of the NG consumed in the MGS and is calculated as follows 45,46 : Here, c represents the products specific costs which can be found in Table 4, and Y denotes the annual products of the MGS. [46][47][48] Subscript elec denotes the electricity. Note that the monetary values used in this article are 2021 US dollars.
The purchased equipment cost of each component is presented in Table 5.
According to the method explained in Bejan et al., 59 the total capital investment (TCI) is divided into three categories: direct cost (DC), indirect cost (IC), and other costs (OC).
The effect of the inflation rate on the TCI is shown below: i .
Here, n and i, respectively, are the number of years and the inflation rate (3.1%). 60 The OMC is calculated based on 3% of the TCI. 45,46 So, the total cost (TC) can be written as follows 59 : The simple payback period (SPP) can be calculated by 45,46 SPP = TC AI (39) and the payback period (PP) as 45,46 (40) where r denotes the discount factor (3%). 45,46 Net present value (NPV) can be expressed as follows 45,46 : where N presents the project lifetime (25 years). 59 The internal rate of return (IRR) can be calculated by 46,61 

| RESULTS AND DISCUSSION
For the MGS a computer code was written in the engineering equation solver (EES). For the physical and thermodynamic properties of different flows (air, hydrogen, steam, SW, brine, DW, NaOH, HCl, NG, and hot exhaust gas), the existing library in EES was used. Table 6 shows the input data for the computer code. Figure 4 shows a flowchart of the procedure followed by the developed code. Sources: Ehyaei et al., 16 Shamoushaki et al., 21 Shakouri et al., 23

| Model validation
It is important to validate the results of energy analysis both theoretically and experimentally. For validation of the GC, Ghazikhani et al. 63 are used, in which the GE-F5 GC is considered. Figure 5 shows the comparison of the model results and the results from Ghazikhani et al. 63 In Figure 5, the specific work output of the GC model is compared with the results of Ghazikhani et al. 63 for three compression ratios of the compressor. The difference is around 4%. The comparison between the GC exergy efficiency of the model and the results from Ghazikhani et al. 63 is depicted in Figure 6 for three compression ratios of the compressor. Similar to Figure 6, the difference is around 4%. For the HRSG validation, Polyzakis et al. 64 are used, in which the pinch temperature, condenser, and boiler pressures are 30 K, 0.03, and 16 bar, respectively. The validation of the model confirms that the ENE is 25% with a CC temperature of 1375 K. The obtained value by the model is 24.1%. The calculated difference is 3.6%.
For validation of the MED, the cycle presented in Shakouri et al. 23 is considered, as it is similar to the MGS proposed in this article. Table 7 shows the results of a   23  comparison between the MED of Shakouri et al. 23 and the proposed model. The difference is less than 4.3% for all comparisons.
Since the ELECD power consumption is calculated based on real conditions, a validation of this subsystem is not needed.

| Results of energy and exergy analyses
The thermodynamic properties in each stream of the proposed MGS are shown in Table 8. The specification of the MED is presented in Table 9. Table 10 shows the electricity produced and consumed by various components and net electrical power produced by the MGS, as well as cooling production by the ARC. The annual products of the EHYAEI ET AL.

| 1035
MGS are presented in Table 11. The MGS produces 614.7 GWh of electrical energy, 97.44 GWh of cooling, 0.092 million tonnes of NaOH, 0.084 million tonnes of HCl, and 12.48 million m 3 of DW throughout the year. The ratio of cooling to electrical energy is equal to 15.8%. The ratio of cooling to electrical power is 15.8%. Figure 7 shows the GC, GC/HRSG/MED/ARC, and system energy and exergy efficiencies. By adding the MED and ARC to GC, the system ENE is increased from 25.3% to 32%, while adding the ELECD slightly decreased the system ENE from 32% to 31.3%. The reason for this increase is that the ELECD consumes a high amount of electrical energy and products of this subsystem (in the form of enthalpy of products) cannot supply its electrical power consumption. The exergy efficiency of the GC increases by adding MED/ ARC from 19.6% to 20%. This increase is not considerable. Similar to system ENE, adding the ELECD decreases the exergy efficiency from 20% to 18.7% for the same reason explained previously.
The EDR percentage for each component of the MGS is presented in Figure 8. The highest percentage of EDR is related to CC and MED due to combustion reaction taking place in the CC and phase change (water to vapor and vice versa) taking place in the MED. After these two components, C features the highest EDR due to the electrical power consumption of C which is summed with the EDR (row 1 of Table 3). P1 features the lowest percentage of the EDR due to the low mass flow rate of water through it and a minor difference between inlet-and outlet-specific exergies T A B L E 10 Electrical power produced and consumed by components and net electrical power productions of the MGS, as well as, cooling production by ARC

Parameter
Unit Value  of P1. Another low percentage of EDR is related to GT since this component produces electrical power which is subtracted from the EDR. Figure 9 shows the percentage of TC for each subsystem. The highest and lowest percentages of TC are related to HRSG and ARC, respectively. The MED and GC represent 23.6% and 22.4% of TC, respectively. Figure 10 shows the NPV, PP, and IRR for three cases, including GC, GC/HRSG/ARC/MED, and the total system. Adding HRSG, ARC, and MED to GC increases the NPV from 1.2 to 2.3 billion US$. IRR also increased from 0.29 to 0.34. PP decreased from 3.6 to 3.2 years. This can be justified because the economic values of extra products (cooling, DW) overcome the extra cost due to the addition of MED, HRSG, and ARC.

| Economic survey results
By adding the ELECD to the previous case, the MGS becomes more economically viable. The NPV and IRR increased by around 65% and 44%, respectively, and PP decreased from 3.2 to 2.1 years. The previous justification for this result also applies in this case. Figure 11 shows the variation of GC/HRSG/MED/ARC and MGS, ENE, and exergy efficiency versus the number of effects (N). It is clear that by increasing N from 4 to 10, GC/HRSG/MED/ARC ENE is increased from 28.6% to 48.7%. Also, the MGS ENE increased from 28% to 47.2%. It can be concluded that N has a considerable effect on the system performance improvement from the energy point of view. The effect of increasing N on GC/HRSG/ MED/ARC and MGS exergy efficiency is not considerable. This means that GC/HRSG/MED/ARC exergy efficiency is only increased from 19.9% to 20.8% by increasing N from 4 to 10. For the MGS exergy efficiency, the inverse trend is observed. That is, by increasing N from 4 to 10, the MGS EXE is decreased from 18.9% to 18.2%. The reason for this phenomenon is that the specific exergy of DW, NaOH, and HCl is low. Figure 12 shows the variation of GOR and RR of MED with N. Both of these factors are increased with increasing N and this increase is nearly linear. Although the increase of N is beneficial for the production of higher DW, economic and technical restrictions are noted. The value of N F I G U R E 9 Percentage of the TC for each subsystem. ARC, air bottom cycle; ELECD, electrodialysis; GC, gas cycle; HRSG, heat recovery steam generator; MED, multieffect distillation; TC, total cost. F I G U R E 10 NPV, PP, IRR for GC, GC/HRSG/ARC/MED, and total system. ARC, air bottom cycle; GC, gas cycle; HRSG, heat recovery steam generator; IRR, internal rate of return; MED, multieffect distillation; NPV, net present value; PP, payback period. should be calculated and justified based on DW needs, budget, and so forth. Figure 13 shows the variation of NPV and PP for GC/ HRSG/MED/ARC and MGS with N. Increasing N from 4 to 10 causes an increase in NPV in both cases. The percentage increases of NPV for GC/HRSG/MED/ARC and MGS are 62.4% and 91%, respectively. The PP of GC/ HRSG/MED/ARC and MGS are reduced from 3.4 and 2.3 to 3.3 and 2.1 years, respectively.

| Parametric study
The variation of ENE of GC, GC/HRSG/MED/ARC, and MGS with r a is presented in Figure 14. Increasing r a causes a reduction of ENE in all three cases. For GC, this decrease is more than for the two other systems. Increasing r a results in increasing the CC exhaust HOT gas mass flow rate and decreasing the CC temperature.
The first effect causes an increase in the net power production of the GC while the second leads to an opposite effect. Integration of GC with HRSG/MED/ARC dampens this considerable reduction of ENE since a higher exhaust hot gas mass flow rate from the GT increases the heat transfer rate in the HRSG and causes more steam production in the HRSG than is used in the MED for DW production. The trend of GC/HRSG/MED/ ARC is similar to that for MGS. Figure 15 shows the variation of exergy efficiency of GC, GC/HRSG/MED/ARC, and MGS versus r a . Similar to Figure 14, increasing r a causes a reduction in exergy efficiency in all three cases. The slope of reduction for exergy efficiency is also much higher than for ENE, of the three considered systems.
The variation of PP in the three cases (GC, GC/HRSG/ MED/ARC, and MGS) versus r a is shown in Figure 16. The PP in all three cases is increased since TC increases due to increasing the size of components. Considering Figure 15, ENE in all three cases is also reduced. Considering these F I G U R E 12 Variation of GOR and RR of MED with N. GOR, gross output ratio; MED, multieffect distillation; RR, recovery ratio. two reasons, PP is increased in all three cases. The slope of the curve is higher for GC in comparison with GC/HRSG/ MED/ARC, and MGS. For example, when increasing r a from 2.1 to 4.5, the PP of GC is increased from 2.2 to 28.6 years. For GC/HRSG/MED/ARC and MGS systems, the PP is 6.6 and 3.5 years, respectively, which is much lower than for GC, since in these cases, increasing r a helps increase the MED and ELECD product outputs. Figure 17 shows the variation of GC, GC/HRSG/MED/ ARC, and MGS energy efficiency with compressor pressure ratio. It seems that increasing the compressor pressure ratio is not beneficial due to the reduction in ENE. The compressor pressure ratio cannot be selected as low as possible since the GT power production is reduced. The selected GT expansion ratio is slightly lower than the compressor pressure ratio for avoiding backflow in the exhaust of GT. The variation of GC, GC/HRSG/MED/ARC, and MGS exergy efficiency versus compressor pressure ratio is depicted in Figure 18. The trend of the exergy efficiency evolution is similar to that for ENE ( Figure 17). Figure 19 shows the variation of ENE for GC, GC/ HRSG/MED/ARC, and MGS energy efficiency versus air temperature. For the GC, the design is based on a constant volumetric flow rate. So, increasing air temperature causes a reduction in air density. Decreasing air density causes a reduction in air mass flow rate, power production, ENE, and exergy efficiency of the GC. This phenomenon has been reported elsewhere. 14,16,64 Considering Figure 20, the integration of GC with HRSG/MED/ARC as well as ELECD cannot offset entirely the reduction of exergy efficiency due to increasing air temperature, but it can dampen it. When increasing air temperature from 278 to 310 K, the GC energy efficiency is reduced by around 24% while it is reduced to 12% for MGS. Figure 20 shows the variation of PP for GC, GC/ HRSG/MED/ARC, and MGS with inflation rate (i). By increasing the inflation rate from 1% to 20%, the PP of MGS is increased from 2.07 to 2.87 years. This increase is the highest for the GC, at 79.8%. For the GC/HRSG/ MED/ARC configuration, PP increases by around 63%. By comparing the percentages of PP increasing, it can be concluded that integrating GC with other subsystems can overcome the effect of the inflation rate.

| CONCLUSIONS
In this study, a new MGS configuration was proposed and evaluated by 3E analyses. The products of this system are electricity, cooling, DW, NaOH, and HCl. This proposed system included GC, SC, ARC, HRSG, MED, and ELECD. The ELECD is used in this proposed system to produce useful products and avoid the release of brine into the marine ecosystem. With this configuration, the proposed system becomes more environmentally friendly. It is clear that, if superheated steam produced in HRSG is used in the SC to produce electricity, the MGS ENE and exergy efficiency are improved. Decision-making about the products of an MGS is based on the needs of customers and investors considering that the point is to purchase their products and the promotion of enhanced energy and exergy efficiencies for the MGS.
The main findings of this paper are as follows: • The following future research is merited: • Integration of GC with SOFC can be attractive while other subsystems can be the same as in the present work. • Superheated steam produced in HRSG is used for electrical production in the steam turbine. The produced electricity can be fed to RO to produce PW. This system can then be compared with the present work.