Highest Exergy Destruction Research Articles

Energy, exergy and economic analyses and performance assessment of a trigeneration system for power, freshwater and heat based on supercritical water oxidation and organic Rankine cycle

The chemical energy contained in organic sewage is not fully utilized. By using organic sewage as a renewable energy source, a novel trigeneration hybrid system consisting of a supercritical water oxidation process and an organic Rankine cycle system for power, freshwater and heat is proposed. The system is evaluated by multiple approaches including parametric sensitivity analysis, exergy and economic analyses. It is found that the proposed hybrid system with the organic sewage mass flow of 5020 kg/h (12% mass fraction) has a power capacity of 286.5 kW and heat capacity of 1081 kW. The electricity efficiency, thermal efficiency, energy efficiency and exergy efficiency could reach up to 9.56%, 44.93%, 53.47% and 22.45%, respectively. The overall exergy flow destruction of the hybrid system is 1706.1 kW. The four components with the highest exergy destruction are reactor, valve, the first stage of preheater and the evaporator of organic Rankine cycle system. The calculated net annual income value is 739.861 k$. The four components with the highest equipment cost are two turbines, cooling water pump and reactor, with the equipment costs of 571.31 k$, 1554.65 k$, 670.50 k$ and 460.91 k$, which account for 32.09%, 19.40%, 8.37% and 5.75%, respectively. The dynamic payback period and the simple payback period of the system are 16.41 and 11.02 years. These results reveal that the proposed hybrid system is efficient, self-sufficient and clean for both power, heat and freshwater generation, which could be a promising candidate as advanced energy conversion technology in practical applications.

Energy and Exergy Analysis of an Organic Rankine Cycle with Internal Heat Exchanger

Bu çalışmada R1234yf, R1234ze ve R134a çalışma akışkanlarının kullanıldığı iç ısı değiştiricili bir Organik Rankine Çevriminin (ORC) enerji ve ekserji analizi yapılmıştır. Farklı çalışma sıcaklıkları için ORC sisteminin enerji ve ekserji performansları analiz edilmiştir. Yapılan analizden kazan, yoğuşturucu ve aşırı soğutma sıcaklıklarının hem enerji hem de ekserji verimlerini önemli derecede etkilediği görülmüştür. Kazan ve aşırı soğutma sıcaklığının artmasıyla enerji ve ekserji verimlerinin arttığı, yoğuşturucu sıcaklığının artmasıyla enerji ve ekserji verimlerinin azaldığı görülmüştür. Ayrıca her bir elemana ait ekserji yıkımları belirlenmiştir. Türbin ve pompa izentropik kabul edildiği için bu elemanlardaki ekserji yıkımları ihmal edilmiştir. En fazla ekerji yıkımının %72 oranında yoğuşturucuda, en düşük ekserji yıkımının da %1 oranında ısı değiştiricide olduğu belirlenmiştir. Sonuç olarak, R134a çalışma akışkanına alternatif olarak seçilen R1234yf akışkanının ORC sistemi için kullanılabilecek en uygun akışkan olduğu gözlemlenmiştir.

Effect of supplementary firing on the performance of a combined cycle power plant

In categorizing various power plants, the combined cycle power plant is used as the base load power plant or the frequency control (load following) power plant of the electricity grid. The mechanism of supplementary firing is one of the common methods of increasing the generating power of combined cycle units especially for slow changes in the demands of the electricity grid. In this research, field study of the performance changes of a real combined cycle unit with and without supplementary firing in three various modes of operation has been performed from energy and exergy viewpoints. Studies show that in all operation modes subject to research, using supplementary firing causes an increase in power generation up to 26.3 MW, energy efficiency of steam cycle about 2.43% and decreases the exergy destruction of steam flow control valves. But this mechanism has a negative impact on energy and exergy efficiencies of the whole combined cycle, which at the worth case about 1.17% decreases energy efficiency. In addition, it was specified that the power plants operation in the partial loads causes high exergy destruction in the cycle which supplementary firing system cannot fully compensate in the steam cycle. It was also found that the more is the role of gas turbines in the cycle, the less the positive effect of supplementary firing system on the increasing power.

Energy/exergy analysis of solar driven mechanical vapor compression desalination system with nano-filtration pretreatment

The performance of the mechanical vapor compression desalination system is limited due to the required vacuum pressure and associated high temperature scaling problem. Thus, a new solar driven mechanical vapor compression desalination plant with nano-filtration pretreatment operating at atmospheric pressure is developed for a production of 500 m3/day. The electrical and thermal energies of the new system are generated using the integration of solar photovoltaic modules and parabolic trough collectors. To evaluate the performance of the new system, energy/exergy analysis is performed by employing a MATLAB package and a Graphical User Interface (GUI) tool. Also, an economic evaluation for the plant's direct, indirect, and unit product costs ($/m3) is presented. The predicted results are validated with the available measurements. The effects of different design parameters such as feed water temperature, distilled and brine water temperature difference, salt rejection and recovery ratio on plant performance are investigated. The proposed plant's exergy efficiency is found to vary from 14.59 to 20% consistently with design parameters. The enhancement in exergy efficiency is estimated to be 153.7%, 56.3%, 32.63% and 27% compared with Multi-Effect evaporation mechanical and conventional vapor compression, forward feed multi-effect mechanical vapor compression and reverse osmosis systems, respectively. The salt rejection and recovery ratio are found to be the most significant parameters to enhance the plant exergy efficiency. Furthermore, the photovoltaic unit has a significant effect on exergy destruction of the plant with a percentage of 85.79%. The parabolic trough collectors also have high exergy destruction of about 69.53%. The economic analysis reveals that the unit water price for the proposed plant is equal to 1.54 $/m3. Therefore, the developed solar-NF-MVC system suits small scale units for remote communities.

Thermodynamic performance evaluation of a heat pump system with textile based solar air heater for heating process

In this study, a newly system is designed and tested which integrates air-to-water heat pump and solar air collector having fabric absorber for the shortcoming of frost depositing on the evaporator in heating condition. Thus, it can achieve synchronous and heat exchange in one integrated system between R410A, gaseous and liquid heat source. In addition, the system performance is evaluated in comparison with those of the standard heat pump and the flat-plate solar air collector assisted heat pump under the same climatic conditions. In this respect, experimental tests are performed for winter season and the thermodynamic inefficiencies’ changes are monitored by real-time exergy analysis under climate conditions of the Muğla province/Turkey. This approximation allows the designer and the manufacturer to see the progress. The results of the study indicate that the textile based solar air collector assisted heat pump shows superior performance with 5.11 COP and 56% exergy efficiency when compared to the other two heat pumps. The equipment with the highest exergy destruction is determined as evaporator. In low temperatures, the problem of frost depositing on the evaporator is solved faster with the use of solar air collector. With the use of a textile-based solar air collector on heat pump, the electrical consumption of the compressor is reduced by 8.3%. Consequently, the proposed system clearly demonstrated its applicability as an independent and reliable system for the building heating process due to its benefits like energy saving, protection against environmental conditions and evaporator’ anti-frost deposit behavior.

Effect of evaporation on the energy conversion of a supercritical water oxidation system containing a hydrothermal flame

Hydrothermal flame is an effective solution to avoid coking and salt plugging in the preheating section of a supercritical water oxidation (SCWO) system with a transpiring wall reactor (TWR). An SCWO system with an evaporation module (SCWOE) is proposed in this work to concentrate the wastewater and promote the formation of a hydrothermal flame. The SCWOE system is simulated using Aspen Plus, and the simulation model is validated by comparing with the experimental data on the migration of organics in evaporation. The introduction of the evaporation module greatly reduces the exergy input. The exergy destruction mainly comes from the TWR, electric heater, and heat exchangers. The highest exergy destruction in the TWR appears in the reaction section, and the total exergy destruction in the TWR due to the transpiring water injection reaches 89.9%. The increase in concentration ratio (α) and feed concentration (ω) can lower the exergy input and improve the energy efficiency, and an energy self-sufficient rate of 79.7% occurs at ω = 15% and α = 2. Moreover, the involatile property of organics is conducive to improving energy self-sufficient rate, and the volatilization rate of phenol in wastewater must be controlled in this system.

Evaluation of Different Flare Gas Recovery Alternatives with Exergy and Exergoeconomic Analyses

Natural gas flaring is considered one of the significant sources of greenhouse gas emissions in the upstream oil and gas industry. It plays an essential role in reducing the energy efficiency of oil and gas production. Depending on flare gas properties, it can be used for different destinations. Herein, we have evaluated the main flare gas recovery alternatives, including sweet gas production, Gas to Liquid (GTL), and power generation, by using exergy and exergoeconomic analysis tools. For this purpose, flare gas condition in two phases of the Pars Special Economic Energy Zone in south of Iran was chosen as a case study. The mass sensitivity analysis is conducted to examine the processes in different flare gas volumes. Mass flow fluctuation analysis is carried out to analyze the effect of mass flow fluctuation as an intrinsic characteristic of flare systems. Results indicate that the production of electrical power from flaring gas is an economical method regarding the exergoeconomic criteria. While the power generation process has disadvantages such as high exergy destruction and high capital cost, advantages such as higher revenue, local potentials for designing, equipment, and construction should be regarded. On the other hand, the sweetening plant has the highest exergetic efficiency rather than other substitutes. This method also has a lower exergoeconomic factor, especially in lower flaring volume. The mass flow sensitivity analysis in these processes shows the GTL production unit's appropriate performance in low flare gas volume. The results also offer the superior performance of sweetening plants in high flare gas volume. Combined Cycle Power Plant (CCPP) process shows an acceptable performance in a broad range of flare gas volumes. Additionally, mass flow fluctuation analysis has been conducted to determine the effect of mass flow fluctuation in these alternatives. The investigation suggested that the CCPP process has lower fluctuation in terms of cycle product (power generation).

A new pre-concentration scheme for brine treatment of MED-MVC desalination plants towards low-liquid discharge (LLD) with multiple self-superheating

Multi-effect distillation units discard brine at high volume to the environment which results in numerous environmental pollutions, low thermodynamic performance, high exergy destruction rate, and high unit cost for the fresh water. This study aims at introducing a new method of pre-treatment for the brine discarded from each stage of the desalination plant to increase its concentration. The new method per-concentrates the brine by superheating the steam produced in the previous stage via recovering valuable thermal heat of the same effect. Due to a low temperature difference between the heat sink and heat source of this self-superheating scheme (i.e., the temperature difference between the steam and brine at each effect), low electrical power is required. Thermodynamic and component-based cost analysis indicate that, in comparison with the conventional MED-MVC unit, the new scheme lowers the specific work consumption (SWC) and unit cost of distilled water (UCDW) by 25.45% and 1.2%, respectively (under electrical power supply of 1845 kW). In addition, the new desalination plant has 25.57% higher exergy efficiency than the conventional MED-MVC unit under the same electrical power supply. Among all elements, the first effect had the highest exergy destruction rate of 397.6 kW, contributing around 15.67% of the total exergy rate of fuel or 21.78% of the total exergy destruction rate. It is also found that the exergy destruction rate of the last effects increases significantly with the new proposed method since the concentration of brine is substantially accumulated at the final stages. Several new dimensionless metrics are defined in order to quantitatively measure the amount of fresh water increment, discarded brine decrement, brine salinity increment (useful for salt production), and steam cost savings achieved at each stage. The results indicated that the steam cost savings were achieved from the number of effects larger than 3.

CO2 capturing from flue gases injected into the NDDCT: Feasibility study, exergy and economic investigation of simultaneously MEA-solvent chemical absorption and flue gas injection

There are several methods to reduce CO2 emissions, including optimization of energy consumption by increasing the efficiency of a powerplant, using renewable energy, and Carbon Capture Plant (CCP). In this study, the methods of increasing efficiency and the application of CCP have been performed simultaneously. To increase efficiency, the newly proposed method of Heat Recovery Steam Generator (HRSG) Flue-Gas Injection (FGI) into the Heller tower of the powerplant was developed. Then, the CO2 captured plant (using MEA chemical Absorption), which is embedded inside the Heller towers, was investigated. Energy and exergy analysis was performed for each component and finally for the whole powerplant under crosswind conditions.The results show that the addition of the CCP inside the tower will even reduce the efficiency of the base cycle by as much as 9%, and in windy conditions, this reduction will be even greater. However, by using the FGI in the Heller tower, the cycle efficiency will increase by 1%.The highest destruction of exergy (41% relatively) happened in the combustion chamber. The CCP had the second-highest exergy destruction, which was estimated to be about 22% for no injection mode and 20% for injection mode relatively. HRSG and the cooling tower had the highest exergy destruction after the CCP.Finally, in view of rising carbon prices in the coming years, among the three proposals, the second plan (FGI with CCP) is economically feasible from 2030 with a return-on-investment rate of 35.63% and the Net Present Value (NPV) of 142480. Moreover, this plan is worthwhile from the environmental point of view.

Exergy Analysis of a Natural Gas-Fired Gas Turbine Combined Cycle Power Plant with Post-Combustion Carbon Capture

Post-combustion carbon capture (PCC) plays an important role in reducing the greenhouse gas emissions. In the present study, an exergy analysis is conducted to assess the exergy destruction and exergetic efficiency of a natural gas-fired combined cycle gas turbine (CCGT) system coupled with the PCC unit. The overall exergetic performance of the system is compared against the baseline CCGT by using realistic data. The working temperature and composition of the exhaust flue gas are two critical parameters that have significant impact on the performance of the absorption liquid and equipment operation. Results show that the highest exergy destruction occurs in the combustion chamber and condenser are 15.69 MW and 11.78 MW, occupying more than 45 % of the exergy destruction of the overall system for the conventional CCGT system. For the CCGT system with PCC unit, the exergy destruction of absorber is relatively high with an exergetic efficiency of 56.18 %. The highest exergetic efficiency is found in the units of combustion chamber and heat recovery steam generator (HRSG), which are 90.23 % and 87.01 %, while the condenser has the lowest efficiency. Identification of the low efficiency component presents an opportunity for improvement of the system.

Assessment and apply of an enhanced exergy analysis for an argon liquefaction system

Argon basically and widely liquefied by three different liquefaction methods such as cryogenic, pressure swing adsorption, and membrane. The cryogenic method with the highest purity rate constitutes the method of this study. In the present work, conventional and enhanced exergy analyses were applied to the liquefaction process of argon. In the enhanced exergy analysis, splitting the exergy destruction into endogenous/exogenous and avoidable/unavoidable parts represents a new direction. In the study, forward exergy analysis is performed for each component and endogenous, exogenous, unavoidable, and avoidable values of these components were calculated. When the convectional exergy analysis is examined, the exergy efficiency of the argon liquefaction system is calculated as 51.77%. When the enhanced exergy analysis of the system is examined, it is found that the highest exergy destruction occurred in the turbine as 614.3 kW. Furthermore, the highest endogenous exergy destruction was found as 494 kW (80.4%) in the turbine.

Energy and exergy analysis of a spray-evaporation multi-effect distillation desalination system

The saline, thermal, and chemical pollution associated with the direct discharge of concentrated brine from various desalination processes are the main negative environmental impacts of seawater desalination. Thus, a novel spray-evaporation multi-effect distillation (SE-MED) desalination system is proposed to eliminate wastewater discharges and achieve zero liquid discharge, in which the spray evaporation technology was adopted for the recovery of freshwater and salts from the brine concentrate disposal. A three-level energy recovery process was adopted in the SE-MED desalination system to improve the thermal efficiency and freshwater productivity. A comprehensive thermodynamic study for the integrated system was carried out to investigate its parametric sensitivity. A three-effect SE-MED desalination system with effects temperature difference of 4.5 °C and heat source temperature of 500 °C was prove suitable for the integrated SE-MED system to balance the system performance, capital cost, and system reliability. Exergy analysis was also conducted for a better understanding of the SE-MED system. The highest exergy destruction (67.76%) occurred in the spray evaporation tank. The useful exergy efficiency was 1.13% and a large amount of surplus exergy is wasted in the process of achieving ZLD.

Theoretical energy and exergy analysis of a combined cooling, heating and power system assisted by a low concentrated photovoltaic recuperator

Supporting energy generation systems with photovoltaic thermal systems is one of the important issues discussed in the literature. With photovoltaic thermal systems, some of the solar energy is directly converted into electrical energy, and the waste heat generated in the photovoltaic module is used for different purposes (heat source, preheater, etc.). In this study, unlike the literature studies, the integration of the photovoltaic module into a recuperator and its use in a combined cooling, heating, and power generation system was investigated thermodynamically. The fossil-fueled energy generation system consists of a Brayton cycle, an organic Rankine cycle, and an absorption refrigeration cycle. The photovoltaic recuperator was placed in the organic Rankine cycle to enhance cooling, heating, and electricity generation. The thermodynamic analyses were performed for different concentration ratios, direct normal irradiation values, mass flow rates, module lengths, and fluid saturation pressures. For the photovoltaic recuperator use, depending on the parameter values, enhancements were achieved in the range of 0–141% for cooling capacity, 32–35.5% for heating capacity, and 1.6–2.1% for net power output. Thus, the overall energy efficiency of the system increased. However, the low contribution of the photovoltaic recuperator to exergy output and the high exergy destruction rate in the photovoltaic recuperator caused the overall exergy efficiency of the system to decrease. The results showed that the location of the photovoltaic recuperator in the combined cooling, heating, and power generation system provided enhancements in a greater number of system outputs, given the results of the literature studies.

Performance of sorption-enhanced chemical looping gasification system coupled with solid oxide fuel cell using exergy analysis

Coal gasification system integrated with solid oxide fuel cell (SOFC) provides a promising energy conversion way owing to its high efficiency. To get a deep insight into the energy performance of this system, a thermodynamic evaluation is implemented. Meanwhile, the technologies of chemical looping and CO2 sorption are introduced into this integration system. It is found that the addition of oxygen carrier and sorbent into coal gasification system can promote the output power of the SOFC with a higher exergy destruction, where the exergy efficiency of most modules in the system can reach 80% except tar separation. The results also reveal that a suitable improvement of gasifying agent amount is beneficial to the energy performance of the system. When the H2O/C molar ratio is increased to 3.0, the SOFC exergy efficiency of 97% can be achieved.

Thermodynamic performance assessment of a geothermal energy assisted combined system for liquid hydrogen generation

The main goal of this work is to achieve comprehensively performance and environmental examines of the geothermal based integrated plant for useful commodities. For this purpose, the geothermal energy-assisted system having different sub-systems is proposed, which are the Kalina Cycle, Organic Rankine Cycle (ORC), hydrogen production, and hydrogen liquefaction sub-processes. Energy, exergy, environment, and sustainability assessments are performed by using different thermodynamic equilibrium. In this regard, the effects of some significant indicators such as reference temperature, geothermal water temperature, and turbines' isentropic efficiency, on the proposed plant performance are addressed. In addition, for a sustainable future, the carbon dioxide emission and sustainability index are evaluated. Performance analyses of the system indicated that the energetic and exergetic efficiencies of the studied model are 25.62% and 52.69%. Furthermore, the energy and exergy analyses of the hydrogen generation and liquefaction subsystem are computed as 27.89% and 46.62%. Besides, exergy destruction analysis is performed to evaluate the irreversibilities of geothermal energy-based plant's components and the highest exergy destruction is seen in the heat exchanger 2.

Exergy Evaluation of a Water Distribution System

The water supply system is one of the most important elements in a city. Currently, many cities struggle with a water deficit problem. Water is a commonly available resource and constitutes the majority of land cover; however, its quality, in many cases, makes it impossible to use as drinking water. To treat and distribute water, it is necessary to supply a certain amount of energy to the system. An important goal of water utility operators is to assess the energy efficiency of the processes and components. Energy assessments are usually limited to the calculation of energy dissipation (sometimes called “energy loss”). From a physical point of view, the formulation of “energy loss” is incorrect; energy in water transport systems is not consumed but only transformed (dissipated) into other, less usable forms. In the water supply process, the quality of energy—exergy (ability to convert into another form)—is consumed; hence, a new evaluation approach is needed. The motivation for this study was the fact that there are no tools for exergy evaluation of water distribution systems. A model of the exergy balances for a water distribution system was proposed, which was tested for the selected case studies of a water supply system and a water treatment station. The tool developed allows us to identify the places with the highest exergy destructions. In the analysed case studies, the highest exergy destruction results from excess pressure (3939 kWh in a water supply system and 1082 kWh in a water treatment plant). The exergy analysis is more accurate for assessing the system compared to the commonly used energy-based methods. The result can be used for assessing and planning water supply system modernisation.

Performance assessment and optimization of a novel geothermal combined cooling and power system integrating an organic flash cycle with an ammonia-water absorption refrigeration cycle

The organic flash cycle is an efficient low-grade energy conversion technology. However, a large space is left for the organic flash cycle to improve the useful energy output due to the throttling processes. To utilize the thermal energy before the low-pressure throttling process in the organic flash cycle driven by the geothermal energy, an ammonia-water absorption refrigeration cycle is adopted to generate cooling by using this part of heat, thereby forming a novel geothermal combined cooling and power (Geo-CCP) system. Eight different organic flash cycle working fluids are investigated, including n-Nonane, n-Octane, n-Heptane, Cyclopentane, i-Pentane, n-Pentane, R365mfc, and R245fa. Detailed thermodynamic modeling, thermoeconomic analysis, parametric analysis, system optimization, and exergy analysis are carried out for the proposed system. The results show that the total product unit cost and exergy efficiency of the proposed systems are 6.52–11.03% lower and 4.10–5.31%pt (percentage point) higher than those of the geothermal separate cooling and power systems. Among the eight considered organic fluids, the n-Nonane brings the lowest total product unit cost and highest exergy efficiency to the Geo-CCP system (11.20 $·GJ−1 and 37.58%). Exergy analysis indicates that the flasher and condenser-I have the first and second highest exergy destructions.

Energy, exergy and exergoenvironmental analyses on gas-diesel fuel marine engine used for trigeneration system

This study has addressed a trigeneration system driven by dual fuel marine engine. The marine engine manufacturers have developed the dual fuel (DF) version to improve the combustion and reduce the pollutant gaseous emissions. The aim was evaluated the performances of gas diesel fuel and full diesel based on exergy and exergoenvironmental analyses. The energy, exergy and exergoenvironmental balances were conducted considering the effect of pollutant emissions. The specific exergy cost (SPECO) approach was applied, which use the fuel and product definition. The diesel marine engine original produced 6.90 MW of electrical power, 28.16 kW of cooling water and 278.2 and 588 kW of heating. The findings revealed that the effect of gas diesel fuel has reduced the energy and exergy efficiencies by 87% in relation to full diesel mode. The diesel engine has the highest exergy destruction with 3051 kW. The NO emission has a portion of 92% of environmental impact rate associated to pollutant formation. The lowest energy and exergetic efficiencies and the highest environmental impact rates of components were investigated. The environmental impact rate per exergy unit of electricity power, cooling water of absorption chiller and heating water were presented. The reduction of environmental impact rate of pollutant formation is the main responsible for the better environmental performance of gas diesel fuel marine engine. Despite the reduction in energy and exergy efficiencies, the dual fuel (DF) technology was able to controlling pollutant emissions and improved the exergoenvironmental performance without great modification into engine. Further recommendations were proposed.

Thermodynamic and thermoeconomic analyses and energetic and exergetic optimization of a turbojet engine

In this study, a thermal model for a turbojet engine is proposed. Besides the engine’s performance, the cost flow rate of each component is evaluated by performing the energetic, exergetic and exergoeconomic analyses. The compressor pressure ratio (πAC), flight Mach number (Ma) and turbine inlet temperature (TIT) are three operating variables, which affect the performance of the whole system. Therefore, a sensitivity analysis is carried out to survey the effect of these variables on objective functions (i.e., energy efficiency, exergy efficiency, and exergy destruction). It is found that there are some contradictions between exergy efficiency and exergy destruction, which by increment in TIT energy efficiency increases, while the exergy destruction decreases. Therefore, an optimization should be applied on the presented system. The results show that the highest exergy destruction, unit exergy cost, and cost rate are 34.96 GJ h−1, 34.85 US$ GJ−1 and 437.37 US$ h−1 occur in the combustion chamber, compressor’s outlet flow and combustion chamber outlet stream, respectively. The energetic and exergetic optimization solution is obtained as the Pareto frontier. Final decision-making methods such as TOPSIS, LINMAP are employed for choosing the optimal solution. Design points of LINMAP and TOPSIS having 65.86%, 66.95% thermal efficiency and 12.51 GJ h−1, 12.65 GJ h−1 exergy destruction, respectively.

Exergy analysis and multi-objective optimisation for energy system: a case study of a separation process in ethylene manufacturing

In chemical industry, most processes face the challenge of high energy consumption. The approach presented in this study can reduce the energy footprint and increase efficiency. The energy system of a separation process in ethylene manufacturing is used to demonstrate the effectiveness of the approach. The chilling train system of the separation process in a typical ethylene plant consumes most cooling and provides appropriate feed for distillation columns. The steady state simulation of system was presented and the simulation results were proved accurate. The conventional exergy analysis identifies that Dephlegmator No.1 (a heat exchange and mass transfer device) has the highest exergy destruction (1401.28kW). Based on advanced exergy analysis, Dephlegmator No.1 has the highest rate of avoidable exergy destruction (89.04 %). Finally, a multi-objective optimisation aiming to maximise system exergy efficiency and to minimise operational cost was performed and the Pareto frontier was obtained. The multi-objective optimized exergy efficiency is 79.53 % (improved by 0.61 %) and the operational cost is 0.02031 yuan/kg (saved by 11.19 %). This study will guide future research to reduce energy consumption in process manufacturing.