# The Feasibility Study, Exergy, and Exergoeconomic Analyses of a Novel Flare Gas Recovery System

^{1}

^{2}

^{3}

^{4}

^{5}

^{*}

## Abstract

**:**

## 1. Introduction

_{x}) are released into the atmosphere, which can be very harmful to human health, especially at high concentration. (2) The waste gases resulting from flares contain chemical substances such as SO

_{x}, CO

_{2}, and H

_{2}S featured as weak acids which are corrosive in the presence of rainfall and result in acidic rain. Acidic rain inflicts damage to crops and buildings and can also cause problems for the ecosystem. (3) CO

_{2}, which is one of the main products of gas burning in flares, is a major greenhouse gas, and its accumulation in the atmosphere is the main reason for the global warming phenomenon in recent years [3].

_{2}, CO, and NO

_{X}in the furnaces, dehumidifier, and flare reduces by 100%, 100%, and about 57%, respectively [8]. Studies by Ojijiagwo et al. found that gas to wire (GTW) technology can be economically viable as part of gas flare management. The investigation conducted a cost-benefit analysis of the GTW technology and its potential impact [9]. An experimental study was conducted to determine the flare gas’s composition and flow rate by Comodi et al. [6]. It was estimated how much energy can be recovered each year and an economic evaluation was performed. Khalili-Garakani et al. reviewed different flare gas recovery technologies to assess the potential of their implementation in the gas and petroleum industries in Iran. According to their findings, flare gas recovery systems can both reduce emissions and generate a significant profit [10]. Asadi et el. investigated and optimized the performance of a novel flare gas recovery process in which compression and treatment of flare gas are carried out simultaneously [11]. Exergy analysis attributes as a sound thermodynamic analysis technique which is evolved from the Second Law of Thermodynamics and also provides a rational and meaningful setting to evaluate and scrutinize processes and systems [12]. Exergy analysis has been widely used in various processes such as sweet gas production [13,14,15], Liquefied Natural Gas (LNG), and Natural Gas Liquids (NGL) production processes [16,17], Gas to Liquid (GTL) [18], and power generation [19,20,21].

## 2. Process Description

## 3. Numerical Implementation

#### 3.1. Exergy Analysis

_{0}and pressure P

_{0}must exchange heat with the environment. This means that when a system has no difference in temperature, pressure, etc., with its surroundings, it does not have the power to go through the process. Accordingly, the dead state is defined as a system in balance with its surrounding environment, where the system is in balance in density, heat, and mechanics with its surroundings.

#### 3.1.1. Exergy Efficiency

_{F,K}is exergy rates of fuel and E

_{P,K}and E

_{D,K}are the exergy rates of product and destruction, respectively. As previously stated, an element’s exergy efficiency is defined as the product-to-fuel ratio. This means that both exergy efficiency and exergy destruction can be calculated simultaneously.

#### 3.1.2. Physical Exergy

_{0}and P

_{0}) [12]:

#### 3.1.3. Chemical Exergy

_{0}and P

_{0}), by a reversible process that includes only heat and mass transfer, and contraction and expansion, the amount of work obtained is equal to chemical exergy. According to what has been said, in order to obtain chemical exergy, in addition to the physical condition of the material stream (temperature and pressure), its chemical composition should also be determined. Chemical exergy for a flow is obtained from the following equation [12]:

#### 3.1.4. Irreversibility

#### 3.1.5. Exergy Balance

## 4. Exergoeconomic Analysis

#### 4.1. Economic Model Assumption

#### 4.2. Calculation of Revenue Requirements

#### 4.3. Costs Levelizing

_{L}) can be determined by [28,29]:

_{j}, BL, CRF, and i

_{eff}denote the revenue requirement in the jth year of operation, the economic life cycle of the system (in years), capital recovery factor, and the average yearly rate of effective system devaluation, respectively. Here, the assumption is that all financial transfers take place at the end of each year. The capital recovery factor can be determined by the following expression [28,29]:

_{w}represents a constant associated with the electricity cost that is assumed to be 0.071 (USD/kW h). The following equation is used to calculate electricity cost in the jth year:

_{FC}and CRF. The following is the formula for calculating the annual levelized operation and maintenance cost (OMCL) [16,31]:

_{th}element cost in the system to the total purchasing cost of system equipment (PEC

_{tot}= ${\sum}_{\mathrm{K}}\mathrm{PEC}$) [16,29]. The first step for this analysis is to estimate the purchasing cost of devices in the process by using purchasing equations in Table 4.

_{k}denotes the cost of purchase of the kth element and s represents the system operating time (working hours) in a 1-year period at full capacity. The term Z

_{k}shows the rate of costs related to capital investment as well as operating and maintenance costs for the kth element. Using the preceding equations:

^{CI}and Z

^{OM}and C

_{F}are often utilized as input parameters for the exergoeconomic analysis. As shown in Table A3, the cost results are the total purchase, repair, and maintenance costs of each device for FGRS.

#### 4.4. Cost Balance Equations

_{j}) is multiplied by the flow exergy rate (Ė

_{j}) on the cost per exergy unit (c

_{j}):

_{j}, c

_{q}, and c

_{w}.

#### 4.5. Exergoeconomic Variables

_{F,k}is related to the location of the equipment in the whole system and the interactions between that device and other process equipment. The average product unit cost for each piece of equipment is evaluated by [16]:

_{k}) is calculated using the following equation [16]:

## 5. Results and Discussion

#### 5.1. Exergy Analysis Results

#### 5.2. Exergoeconomic Analysis Results

#### 5.3. Sensitivity Analysis

## 6. Conclusions

- In exergy destruction cost, ejectors are the most important components since the highest exergy destruction cost in the system is that of the EJ-3 ejector, which is 89.01 USD/h;
- From the exergoeconomic analysis, it can be deduced that the investment cost of air fans and compressors should be reduced due to their high exergoeconomic factor to reduce the system’s total cost;
- The performance of the ejectors should be enhanced due to their low exergoeconomic factor to lower the total system cost. Moreover, the irreversibility of ejectors is very high compared with air fans and compressors.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Nomenclature

BL | Book life | $\mathsf{\epsilon}$ | Exergy Efficiency |

c | Unit exergy cost (USD/kJ) | Superscripts | |

$\dot{\mathrm{C}}$ | Exergy cost rate (USD/h) | CI | Capital investment |

S | Entropy (kJ/kg °C) | OM | Operating and maintenance |

h | Enthalpy (kJ/kg) | Subscripts | |

CC | Carrying charge | 0 | Index for first year of operation |

CRF | Capital recovery factor | a | Air |

c_{w} | Unit cost of the generated electricity (USD/kWh) | D | Destruction |

$\mathrm{e}$ | Specific flow exergy (kJ/kg mole) | F | Fuel |

$\dot{\mathrm{E}}$ | Exergy rate (kW) | i | Inlet |

Ex | Exergy (kW) | k | kth component |

F | Exergoeconomic factor (%) | L | Levelized |

FC | Fuel cost (USD/s) | o | Outlet |

I | Irreversibility (kW) | P | Production |

i_{eff} | Average annual discount rate (cost of money) | tot | Total |

j | jth year of operation | Abbreviations | |

$\dot{\mathrm{m}}$ | Flow rate (kg mole/s) | AC | Air cooler |

OMC | Operating and maintenance cost | C | Compressor |

PEC | Purchase equipment cost (USD) | D | Flash drum |

$\dot{\mathrm{Q}}$ | Heat duty (kW) | EJ | Ejector |

r | Relative cost difference (%) | TE | Tee |

r_{FC} | Annual escalation rate for the fuel cost | MIX | Mixer |

r_{OM} | Annual escalation rate for the operating and maintenance cost | V | Expansion valve |

TRR | Total revenue requirement | Ph | Physical |

W | Work transfer rate (kW) | Ch | Chemical |

$\dot{\mathrm{W}}$ | Power (kW) | FGRS | Flare Gas Recovery System |

$\dot{\mathrm{Z}}$_{k} | Total cost rate of kth component including capital investment and operating–maintenance cost | ||

$\dot{\mathrm{Z}}$^{CI} | Rate of capital investment of kth component | ||

${\dot{\mathrm{Z}}}_{\mathrm{K}}^{\mathrm{OM}}$ | Rate of operating and maintenance cost of kth component | ||

Greek letters | |||

$\mathsf{\tau}$ | Annual operating hours (h) |

## Appendix A

Equipment | Exergy Destruction | Exergy Efficiency |
---|---|---|

Compressor | $\mathrm{I}={\mathrm{Ex}}_{\mathrm{i}}-{\mathrm{Ex}}_{\mathrm{o}}=\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}+\mathrm{w}-\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}$ [34,35] | $\mathsf{\epsilon}=\frac{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}\text{}-\text{}\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}}{\mathrm{W}}$ [34,36] |

Ejector | $\mathrm{I}={\mathrm{Ex}}_{\mathrm{i}}-{\mathrm{Ex}}_{\mathrm{o}}=\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}-\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}$ [34,35] | $\mathsf{\epsilon}=\frac{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}}{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}}$ [34,35] |

Expansion valve | $\mathrm{I}={\mathrm{Ex}}_{\mathrm{i}}-{\mathrm{Ex}}_{\mathrm{o}}=\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}-\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}$ [34,35] | $\mathsf{\epsilon}=\frac{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}}{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}}$ [34,35] |

Air cooler | $\mathrm{I}={\mathrm{Ex}}_{\mathrm{i}}-{\mathrm{Ex}}_{\mathrm{o}}=\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}+{\mathrm{e}}_{\mathrm{ai}}+\mathrm{w}-\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}-{\mathrm{e}}_{\mathrm{ao}}$ [35,36] | $\mathsf{\epsilon}=\frac{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}\text{}+\text{}{\mathrm{e}}_{\mathrm{ao}}}{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}\text{}+\text{}\mathrm{W}}$ [35,36] |

Pump | $\mathrm{I}={\mathrm{Ex}}_{\mathrm{i}}-{\mathrm{Ex}}_{\mathrm{o}}=\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}+\mathrm{w}-\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}$ [34,35] | $\mathsf{\epsilon}=\frac{\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{i}}\text{}-\text{}\sum {(\dot{\mathrm{m}}.\mathrm{e})}_{\mathrm{o}}}{\mathrm{W}}$ [34,35] |

**Table A2.**Economic constants and assumptions [16].

Economic Parameters | Value |
---|---|

The average annual rate of the cost of money $({\mathrm{i}}_{\mathrm{eff}}$) | 10% |

Average nominal escalation rate for the operating and maintenance cost (r_{OMC}) | 5% |

Average nominal escalation rate for fuel (r_{FC}) | 5% |

Plant economic life (book life) | 25 years |

Total annual operating hours of the system operation at full load | 7300 |

Equipment | Ż (USD/h) | Ż^{OMC} (USD/h) | Ż^{CI} (USD/h) |
---|---|---|---|

C-1 | 34.47 | 0.58 | 33.89 |

C-2 | 17.28 | 0.29 | 16.99 |

C-3 | 12.15 | 0.20 | 11.94 |

AC-1 | 9.95 | 0.17 | 9.78 |

AC-2 | 9.66 | 0.16 | 9.50 |

AC-3 | 9.43 | 0.16 | 9.27 |

EJ-1 | 1.84 | 0.03 | 1.81 |

EJ-2 | 1.97 | 0.03 | 1.94 |

EJ-3 | 2.08 | 0.03 | 2.04 |

## References

- Rahimpour, M.R.; Jokar, S.M. Feasibility of flare gas reformation to practical energy in Farashband gas refinery: No gas flaring. J. Hazard. Mater.
**2012**, 209, 204–217. [Google Scholar] [CrossRef] - Rahimpour, M.; Jamshidnejad, Z.; Jokar, S.; Karimi, G.; Ghorbani, A.; Mohammadi, A. A comparative study of three different methods for flare gas recovery of Asalooye Gas Refinery. J. Nat. Gas Sci. Eng.
**2012**, 4, 17–28. [Google Scholar] [CrossRef] - Soltanieh, M.; Zohrabian, A.; Gholipour, M.J.; Kalnay, E. A review of global gas flaring and venting and impact on the environment: Case study of Iran. Int. J. Greenh. Gas Control.
**2016**, 49, 488–509. [Google Scholar] [CrossRef] - Fallah, T.; Belghaieb, J.; Hajji, N. Analysis and simulation of flare gas recovery in oil and gas producing company. Energy Sources Part A Recovery Util. Environ. Eff.
**2019**, 1–7. [Google Scholar] [CrossRef] - Yazdani, E.; Asadi, J.; Dehaghani, Y.H.; Kazempoor, P. Flare gas recovery by liquid ring compressors-system design and simulation. J. Nat. Gas Sci. Eng.
**2020**, 84, 103627. [Google Scholar] [CrossRef] - Comodi, G.; Renzi, M.; Rossi, M. Energy efficiency improvement in oil refineries through flare gas recovery technique to meet the emission trading targets. Energy
**2016**, 109, 1–12. [Google Scholar] [CrossRef] - Haidl, J.; Mařík, K.; Moucha, T.; Rejl, F.J.; Valenz, L.; Zednikova, M. Hydraulic characteristics of liquid–gas ejector pump with a coherent liquid jet. Chem. Eng. Res. Des.
**2021**, 168, 435–442. [Google Scholar] [CrossRef] - Mousavi, S.M.; Lari, K.; Salehi, G.; Torabi Azad, M. Technical, economic, and environmental assessment of flare gas recovery system: A case study. Energy Sources Part A Recovery Util. Environ. Eff.
**2020**, 1–13. [Google Scholar] [CrossRef] - Ojijiagwo, E.; Oduoza, C.F.; Emekwuru, N. Economics of gas to wire technology applied in gas flare management. Eng. Sci. Technol. Int. J.
**2016**, 19, 2109–2118. [Google Scholar] [CrossRef] [Green Version] - Khalili-Garakani, A.; Iravaninia, M.; Nezhadfard, M. A review on the potentials of flare gas recovery applications in Iran. J. Clean. Prod.
**2021**, 279, 123345. [Google Scholar] [CrossRef] - Asadi, J.; Yazdani, E.; Dehaghani, Y.H.; Kazempoor, P. Technical evaluation and optimization of a flare gas recovery system for improving energy efficiency and reducing emissions. Energy Convers. Manag.
**2021**, 236, 114076. [Google Scholar] [CrossRef] - Dincer, I.; Rosen, M.A. Exergy: Energy, Environment and Sustainable Development; Elsevier: Amsterdam, The Netherlands, 2020. [Google Scholar]
- Mohamadi-Baghmolaei, M.; Hajizadeh, A.; Zendehboudi, S.; Duan, X.; Shiri, H. Advanced exergy analysis of an acid gas removal plant to explore operation improvement potential toward cleaner production. Energy Fuels
**2021**, 35, 9570–9588. [Google Scholar] [CrossRef] - Mohamadi-Baghmolaei, M.; Hajizadeh, A.; Zahedizadeh, P.; Azin, R.; Zendehboudi, S. Evaluation of hybridized performance of amine scrubbing plant based on exergy, energy, environmental, and economic prospects: A gas sweetening plant case study. Energy
**2021**, 214, 118715. [Google Scholar] [CrossRef] - Mohamadi-Baghmolaei, M.; Hajizadeh, A.; Zendehboudi, S.; Duan, X.; Shiri, H.; Cata Saady, N.M. Exergy and Exergoeconomic Assessment of an Acid Gas Removal Unit in a Gas Refinery Plant. Ind. Eng. Chem. Res.
**2021**, 60, 14591–14612. [Google Scholar] [CrossRef] - Mehrpooya, M.; Ansarinasab, H. Exergoeconomic evaluation of single mixed refrigerant natural gas liquefaction processes. Energy Convers. Manag.
**2015**, 99, 400–413. [Google Scholar] [CrossRef] - Ghorbani, B.; Mehrpooya, M.; Hamedi, M.-H.; Amidpour, M. Exergoeconomic analysis of integrated natural gas liquids (NGL) and liquefied natural gas (LNG) processes. Appl. Therm. Eng.
**2017**, 113, 1483–1495. [Google Scholar] [CrossRef] - Greyling, S.; Marais, H.; Van Schoor, G.; Uren, K.R. Application of exergy-based fault detection in a gas-to-liquids process plant. Entropy
**2019**, 21, 565. [Google Scholar] [CrossRef] [Green Version] - Eghtesad, A.; Afshin, H.; Hannani, S.K. Energy, exergy, exergoeconomic, and economic analysis of a novel power generation cycle integrated with seawater desalination system using the cold energy of liquified natural gas. Energy Convers. Manag.
**2021**, 243, 114352. [Google Scholar] [CrossRef] - Alirahmi, S.M.; Assareh, E. Energy, exergy, and exergoeconomics (3E) analysis and multi-objective optimization of a multi-generation energy system for day and night time power generation-Case study: Dezful city. Int. J. Hydrogen Energy
**2020**, 45, 31555–31573. [Google Scholar] [CrossRef] - Zaresharif, M.; Vatani, A.; Ghasemian, M. Evaluation of Different Flare Gas Recovery Alternatives with Exergy and Exergoeconomic Analyses. Arab. J. Sci. Eng.
**2022**, 47, 5501–5520. [Google Scholar] [CrossRef] - Hyprotech HYSYS v71.1 User Guide; Aspen Technology Inc.: Burlington, MA, USA, 2009.
- Vatani, A.; Mehrpooya, M.; Palizdar, A. Energy and exergy analyses of five conventional liquefied natural gas processes. Int. J. Energy Res.
**2014**, 38, 1843–1863. [Google Scholar] [CrossRef] - Yazdanfar, J.; Mehrpooya, M.; Yousefi, H.; Palizdar, A. Energy and exergy analysis and optimal design of the hybrid molten carbonate fuel cell power plant and carbon dioxide capturing process. Energy Convers. Manag.
**2015**, 98, 15–27. [Google Scholar] [CrossRef] - Rivero, R.; Rendón, C.; Gallegos, S. Exergy and exergoeconomic analysis of a crude oil combined distillation unit. Energy
**2004**, 29, 1909–1927. [Google Scholar] [CrossRef] - Farshi, L.G.; Mahmoudi, S.S.; Rosen, M. Exergoeconomic comparison of double effect and combined ejector-double effect absorption refrigeration systems. Appl. Energy
**2013**, 103, 700–711. [Google Scholar] [CrossRef] - Cengal, Y.A.; Boles, M.A. Thermodynamics: An Engineering Approach; Highstown McGraw Hill: Hightstown, NJ, USA, 1998. [Google Scholar]
- Institute, E.P.R. Technical Assessment Guide (TAG) Electricity Supply 1993; EPRI Palo Alto: Washington, DC, USA, 1993. [Google Scholar]
- Seshadri, K. Thermal Design and Optimization; Bejan, A., Tsatsaronis, G., Moran, M., Eds.; Wiley Interscience, John Wiley Sons Inc.: New York, NY, USA; Pergamon: Berlin, Germany, 1996. [Google Scholar]
- Lazzaretto, A.; Tsatsaronis, G. SPECO: A systematic and general methodology for calculating efficiencies and costs in thermal systems. Energy
**2006**, 31, 1257–1289. [Google Scholar] [CrossRef] - Naderi, M.; Ahmadi, G.; Zarringhalam, M.; Akbari, O.; Khalili, E. Application of water reheating system for waste heat recovery in NG pressure reduction stations, with experimental verification. Energy
**2018**, 162, 1183–1192. [Google Scholar] [CrossRef] - Couper, J.R.; Penney, W.R.; Fair, J.R.; Walas, S.M. Chemical Process Equipment: Selection and Design; Gulf Professional Publishing: Houston, TX, USA, 2005. [Google Scholar]
- Lazzaretto, A.; Tsatsaronis, G. On the quest for objective equations in exergy costing. In Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Dallas, TX, USA, 16–21 November 1997; pp. 197–210. [Google Scholar]
- Tirandazi, B.; Mehrpooya, M.; Vatani, A.; Moosavian, S.A. Exergy analysis of C2+ recovery plants refrigeration cycles. Chem. Eng. Res. Des.
**2011**, 89, 676–689. [Google Scholar] [CrossRef] - Vatani, A.; Mehrpooya, M.; Palizdar, A. Advanced exergetic analysis of five natural gas liquefaction processes. Energy Convers. Manag.
**2014**, 78, 720–737. [Google Scholar] [CrossRef] - Mehrpooya, M.; Hossieni, M.; Vatani, A. Novel LNG-based integrated process configuration alternatives for coproduction of LNG and NGL. Ind. Eng. Chem. Res.
**2014**, 53, 17705–17721. [Google Scholar] [CrossRef]

**Figure 4.**Exergy destruction (

**A**), exergy efficiency (

**B**), exergy destruction cost (

**C**), exergoeconomic factor (

**D**), and relative cost difference (

**E**) changes relative to recovered gas flow rate.

**Figure 5.**Exergy destruction (

**A**), exergy destruction cost (

**B**), exergoeconomic factor (

**C**), and relative cost difference (

**D**) variation versus flare gas pressure.

Stream No. | Temperature (°C) | Pressure (psi) | Enthalpy (kJ/kg) | Entropy (kJ/kg °C) | Flow Rate (kg/h) |
---|---|---|---|---|---|

1 | 35 | 3 | −3853.1 | 10.9 | 7000 |

1a | 35 | 3 | −3853.1 | 10.9 | 5000 |

1b | 35 | 3 | −3853.1 | 10.9 | 2000 |

1c | 35 | 3 | −3853.1 | 10.9 | 2000 |

2 | 35 | 3 | −3853.1 | 10.9 | 2500 |

2a | 35 | 3 | −3853.1 | 10.9 | 5000 |

2b | 35 | 3 | 0 | 0 | 0 |

3 | 35 | 3 | −3853.1 | 10.9 | 2500 |

4 | 40 | 60 | −3846.2 | 9.6 | 2500 |

4a | 208.5 | 20 | −3425 | 11.1 | 2500 |

4b | 40 | 20 | −3843.3 | 10.1 | 2500 |

4c | 101.5 | 40 | −3702.8 | 10.2 | 2500 |

4d | 40 | 40 | −3844.7 | 9.7 | 2500 |

4e | 75.6 | 60 | −3765.1 | 9.8 | 2500 |

5 | 45.3 | 210 | −4469.9 | 9.9 | 463,716 |

6 | 45 | 200 | −4469.9 | 9.9 | 463,716 |

6a | 45 | 200 | −4469.9 | 9.9 | 66,000 |

6b | 45 | 200 | −4469.9 | 9.9 | 132,000 |

6c | 45 | 200 | −4469.9 | 9.9 | 265,716 |

7 | 40.6 | 60 | −4466.6 | 10.5 | 466,216 |

7a | 39 | 15.9 | −4447.4 | 11.1 | 68,500 |

7b | 39.7 | 34.7 | −4462.2 | 10.7 | 200,500 |

8 | 40.5 | 60 | −4463.3 | 10.5 | 468,716 |

Equipment | Component Name | Heat Duty (kW) | Air Flow Rate (kg/h) | Outlet Air Temperature (°C) | Power (kW) |
---|---|---|---|---|---|

Air coolers | AC-1 | −290.5 | 422,800 | 27.44 | 32 |

AC-2 | −98.5 | 424,000 | 25.83 | 26 | |

AC-3 | −56.3 | 424,200 | 25.47 | 21 | |

Equipment | Component Name | Adiabatic Efficiency (%) | Pressure Ratio | Outlet Temperature (°C) | Power (kW) |

Compressors | C-1 | 75 | 6.67 | 208.5 | 297.26 |

C-2 | 75 | 2 | 101.5 | 97.6 | |

C-3 | 75 | 1.5 | 75.61 | 55.28 |

Stream No. | Physical Exergy (kW) | Chemical Exergy (kW) | Total Exergy (kW) |
---|---|---|---|

1 | −416.80 | 98,196.04 | 97,779.04 |

1a | −297.71 | 70,140.03 | 69,842.32 |

1b | −119.08 | 28,056.01 | 27,936.93 |

1c | −119.08 | 28,056.01 | 27,936.93 |

2 | −148.86 | 35,070.02 | 34,921.16 |

2a | −297.71 | 70,140.03 | 69,842.32 |

2b | 0 | 0 | 0 |

3 | −148.86 | 35,070.02 | 34,921.16 |

4 | 131.99 | 35,070.02 | 35,202.00 |

4a | 100.42 | 35,070.02 | 35,170.44 |

4b | 29.42 | 35,070.02 | 35,099.44 |

4c | 107.21 | 35,070.02 | 35,177.22 |

4d | 94.22 | 35,070.02 | 35,164.24 |

4e | 137.54 | 35,070.02 | 35,207.55 |

5 | 50,243.97 | 6,619,283.05 | 6,669,527.01 |

6 | 49,339.23 | 6,619,238.05 | 6,668,622.27 |

6a | 7022.38 | 94,112.59 | 949,134.97 |

6b | 14,044.76 | 1,884,225.18 | 1,898,269.93 |

6c | 28,272.09 | 3,792,945.28 | 3,821,217.38 |

7 | 26,895.53 | 6,654,292.38 | 6,681,187.91 |

7a | 241.06 | 977,139.26 | 977,380.32 |

7b | 7074.40 | 2,861,354.50 | 2,868,428.89 |

8 | 27,026.77 | 6,689,313.73 | 6,716,340.50 |

**Table 4.**The cost estimation equations of each equipment [32].

Equipment | Cost Estimation Equations |
---|---|

Compressor | PEC_{C} = 7900(HP)^{0.62} |

Air cooler | PEC_{AC} = 30(A)^{0.4} |

Ejector | PEC_{EJ} = 13.3(f_{1}f_{2}f_{3}X^{0.41}) |

Equipment | Main Equations | Equipment | Main Equations |
---|---|---|---|

EJ-1 | Ċ_{3} + Ċ_{6a} + Ż_{EJ1} = Ċ_{7a} | C-1 | Ċ_{2} + Ċ_{W-C1} + Ż_{C1} = Ċ_{4a} |

EJ-2 | Ċ_{7a} + Ċ_{6b} + Ż_{EJ2} = Ċ_{7b} | C-2 | Ċ_{4b} + Ċ_{W-C2} + Ż_{C2} = Ċ_{4c} |

EJ-3 | Ċ_{7b} + Ċ_{6c} + Ż_{EJ3} = Ċ_{7} | C-3 | Ċ_{4d} + Ċ_{W-C3} + Ż_{C3} = Ċ_{4e} |

TE-1 | Ċ_{1} = Ċ_{1a} + Ċ_{1b} | AC-1 | Ċ_{4a} + Ċ_{W-AC1} + Ż_{AC1} = Ċ_{4b} |

TE-2 | Ċ_{2a} = Ċ_{2} + Ċ_{3} | AC-2 | Ċ_{4c} + Ċ_{W-AC2} + Ż_{AC2} = Ċ_{4d} |

TE-3 | Ċ_{6} = Ċ_{6a} + Ċ_{6b} + Ċ_{6c} | AC-3 | Ċ_{4e} + Ċ_{W-AC3} + Ż_{AC3} = Ċ_{4} |

Mix-1 | Ċ4 + Ċ7 = Ċ8 |

Equipment | Auxiliary Equations |
---|---|

TE-1 | (Ċ1a/Ė1a) = (Ċ1b/Ė1b) |

TE-2 | (Ċ2/Ė2) = (Ċ3/Ė3) |

TE-3 | (Ċ6a/Ė6a) = (Ċ6b/Ė6b) = (Ċ6c/Ė6c) |

Flow No. | C (USD/Gj) | Ċ (USD/h) |
---|---|---|

1 | 1.220 | 429.4 |

1a | 1.220 | 306.7 |

1b | 1.220 | 306.7 |

1c | 1.220 | 306.7 |

2 | 0 | 0 |

2a | 1.220 | 153.4 |

2b | 1.220 | 306.7 |

3 | 0 | 0 |

4 | 1.220 | 153.4 |

4a | 2.320 | 294.1 |

4b | 1.695 | 214.7 |

4c | 1.8 | 227.5 |

4d | 2.003 | 253.6 |

4e | 2.098 | 265.6 |

5 | 2.231 | 282.7 |

6 | 2.923 | 70,182 |

6a | 2.923 | 70,182 |

6b | 2.923 | 9989 |

6c | 2.923 | 19,978 |

7 | 2.923 | 40,215 |

7a | 2.925 | 70,341 |

7b | 2.883 | 10,144 |

8 | 2.917 | 30,124 |

Equipment | Ė_{F} (kW) | Ė_{P} (kW) | Ė_{D} (kW) | ε (%) |
---|---|---|---|---|

C-1 | 297.26 | 249.28 | 47.99 | 83.86 |

C-2 | 97.60 | 77.79 | 19.81 | 79.70 |

C-3 | 55.28 | 43.32 | 11.96 | 78.36 |

AC-1 | 132.42 | 120.42 | 12 | 90.94 |

AC-2 | 133.21 | 121.22 | 11.99 | 91 |

AC-3 | 158.54 | 143.99 | 14.55 | 90.82 |

EJ-1 | 984,056.13 | 977,380.32 | 6675.81 | 99.32 |

EJ-2 | 2,875,650.25 | 2,868,428.89 | 7221.36 | 99.75 |

EJ-3 | 6,689,646.27 | 6,681,187.91 | 8458.35 | 99.87 |

Equipment | Ė_{D} (kW) | C_{F} (USD/Gj) | C_{P} (USD/Gj) | ĊD (USD/h) | Ż (USD/h) | ε (%) | r (%) | f (%) |
---|---|---|---|---|---|---|---|---|

C-1 | 47.99 | 19.72 | 61.92 | 3.41 | 34.47 | 83.86 | 214.01 | 91 |

C-2 | 19.81 | 19.72 | 86.44 | 1.41 | 17.28 | 79.70 | 338.34 | 92.47 |

C-3 | 11.96 | 19.72 | 103.05 | 0.85 | 12.15 | 78.36 | 422.59 | 93.47 |

AC-1 | 12 | 19.72 | 44.63 | 0.85 | 9.95 | 90.94 | 126.31 | 92.11 |

AC-2 | 11.99 | 19.72 | 43.81 | 0.85 | 9.66 | 91 | 122.14 | 91.90 |

AC-3 | 14.55 | 19.72 | 39.90 | 1.03 | 9.43 | 90.82 | 102.31 | 90.12 |

EJ-1 | 6675.81 | 2.92 | 2.94 | 70.25 | 1.84 | 99.32 | 0.7 | 2.55 |

EJ-2 | 7221.36 | 2.92 | 2.93 | 75.99 | 1.97 | 99.75 | 0.26 | 2.53 |

EJ-3 | 8458.35 | 2.92 | 2.93 | 89.01 | 2.08 | 99.87 | 0.13 | 2.28 |

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Parivazh, M.M.; Mousavi, M.; Naderi, M.; Rostami, A.; Dibaj, M.; Akrami, M.
The Feasibility Study, Exergy, and Exergoeconomic Analyses of a Novel Flare Gas Recovery System. *Sustainability* **2022**, *14*, 9612.
https://doi.org/10.3390/su14159612

**AMA Style**

Parivazh MM, Mousavi M, Naderi M, Rostami A, Dibaj M, Akrami M.
The Feasibility Study, Exergy, and Exergoeconomic Analyses of a Novel Flare Gas Recovery System. *Sustainability*. 2022; 14(15):9612.
https://doi.org/10.3390/su14159612

**Chicago/Turabian Style**

Parivazh, Mohammad Mehdi, Milad Mousavi, Mansoor Naderi, Amir Rostami, Mahdieh Dibaj, and Mohammad Akrami.
2022. "The Feasibility Study, Exergy, and Exergoeconomic Analyses of a Novel Flare Gas Recovery System" *Sustainability* 14, no. 15: 9612.
https://doi.org/10.3390/su14159612