Carbon Dioxide Liquefaction Research Articles

Techno-economic analysis on a hybrid system with carbon capture and energy storage for liquefied natural gas cold energy utilization

For cold energy utilization in the liquefied natural gas (LNG) regasification process, integrated cryogenic CO2 capture using high-grade cold energy is a mainstream method. However, high-grade cold energy for carbon capture may lead to a decrease in cold energy utilization efficiency. This paper aims to propose a hybrid system in which high-grade cold energy is used for liquid air energy storage (LAES) and post-combustion amine scrubbing technology is considered to replace cryogenic carbon capture for improved working efficiency. The medium and low-grade cold energy is utilized for similar working processes, e.g., organic Rankine cycle (ORC), carbon dioxide liquefaction, and data center cooling for comparison. Results show that the proposed hybrid system can produce 437.7 MW of power, 28.8 t·h−1 of CO2 capture capacity, and 23.0 MW of cooling capacity, respectively. The levelized cost of electricity and the annual revenue are 112.3 $·MWh−1 and 2.17 million $, respectively. LNG cold energy utilization efficiency, system energy efficiency, and cold exergy efficiency are 53.4 %, 24.0 %, and 51.5 %, higher than similar processes using cryogenic CO2 capture. It is demonstrated that the proposed system could be a promising method for cold energy utilization and post-combustion capture.

Techno-economic assessment of the modified Allam cycle configurations with multi-stage pump/compressor for efficient operation in hot regions

The Allam cycle is renowned for its zero-carbon power generation and high efficiency. However, it faces challenges in hot regions where there is no available cold source for carbon dioxide liquefaction, leading to deterioration in its performance. In this study, a multi-stage pump/compressor is introduced, aiming to enhance the net electric efficiency of the conventional Allam cycle. Various potential enhancement methods are explored and analyzed through comprehensive thermodynamic and economic analyses. Among the configurations under consideration, the Allam cycle combined with two-stage pump/compressor and bypass compressor exhibits the best performance, achieving a 6.71 % increase in the efficiency of the conventional cycle. For the conventional Allam cycle, the efficiency decreases by 0.42 % for every 1 ℃ increase in ambient temperature, however, it is 0.17 % for the Allam-MPC cycle, which indicates it is less responsive to changes in ambient temperature. Moreover, the economic performance of the proposed cycle is better than that of the conventional cycle, which has higher revenue and lower levelized cost of electricity. The capital costs of the modified equipment represent around 1.43 % of the total capital costs of the conventional Allam cycle, and the investment-increment payback period is less than 0.5 years when the ambient temperature exceeds 30 ℃. Sensitivity analyses suggest that the proposed cycle will be more economically viable in hot regions with lower natural gas prices and higher electricity prices. Overall, this study provides a promising approach to improving the performance of Allam cycle in hot regions and offering valuable references for its practical implementation.

이산화탄소 액화를 위한 증기 재압축 냉동 공정과 액체질소 냉열을 이용한 냉동 공정의 비교 연구

이산화탄소 액화를 위한 증기 재압축 냉동 공정과 액체질소 냉열을 이용한 냉동 공정의 비교 연구

UTILIZATION OF CARBON DIOXIDE TAKING INTO ACCOUNT THE CLIMATIC CHARACTERISTICS OF THE REGION

Based on a review of the literature, it is shown that there are a large number of qualified specialists in the cultivation of microalgae to absorb carbon dioxide in the country, despite the apparent complexity of this method in comparison with the method of injecting it into the layer. Since the absorption by microalgae of the genus chlorella occurs using the energy of sunlight, then with a sufficient amount of it, emissions of additional carbon dioxide are dispensed with. This technology, like no other, depends on climatic conditions: in a climate with an average annual temperature below 0 °C, algae cultivation is impractical, here the only acceptable technology is carbon dioxide liquefaction and its injection into the layer. In a temperate climate, where the largest number of enterprises and cities in Europe and Russia are located, it is necessary to alternate technologies, that is, in summer, cultivate large areas of chlorella according to the technology proposed in the article, and in winter, reduce the area and pump some of carbon dioxide into storage.

Comprehensive performance evaluation and optimization of a liquid carbon dioxide energy storage system with heat source

• Two liquid compressed carbon dioxide energy storage systems are proposed. • The modified cycle enhances the recovery of the turbine exhaust energy. • The relative cost difference of the modified cycle has decreased by 6.86%. • Insights are obtained by parametric analysis and multi-objective optimization. The investigation of advanced large-scale energy storage systems is needed due to the installation and grid-connected generation of instability renewable energy. As the compression heat tends to low temperature, in this paper, a liquid carbon dioxide energy storage system with heat source and its modification are proposed, in which an ice storage carbon dioxide liquefaction scheme and a modified recuperator layout are specially designed. Firstly, thermodynamic and exergoeconomic models are developed to evaluate the proposed systems; Then, a comprehensive understanding of the proposed system is obtained by parametric analysis and multi-objective optimization; Finally, a comparative analysis shows the attractiveness of the proposed system. The results show that the modified recuperator configuration improves the system performance by recovering more turbine exhaust energy, and the relative cost difference is reduced by 6.86%. The efficiency and economy of the system are greatly influenced by the compressor and turbine performance. Multi-objective optimization obtained compromise results of total exergy efficiency and unit output cost of 68.79% and 34.04 $/GJ. The comparative analysis reflects that the proposed system has certain superiorities.

Techno-economic and multi objective optimization of zero carbon emission biomass based supercritical carbon dioxide oxy combustion system integrated with carbon dioxide liquefaction system and solid oxide electrolyzer

Consumption of fossil fuels and their scarcity of resources as a global challenge has posed a major problem for the energy sector. To this end, four sub-systems including oxy-fuel production and combustion, hydrogen production, power generation and liquefaction and storage of carbon dioxide were integrated to obtain a new power generation system. The proposed system was evaluated based on techno-economic analyses and multi-objective optimization. Syngas was used as a fuel where syngas was obtained through biomass gasification. Linde-Hampson liquefaction system was used to facilitate storage and transport of carbon dioxide. Solid Oxide Electrolyzer was employed to save the extra energy of system efficiently and supercritical carbon dioxide cycle was used because it is environmentally friendly. The results showed that the obtained values of the levelized cost of electricity are 0.6019 $/kWh, 0.7117 $/kWh, 0.5059 $/kWh, and 0.42114 $/kWh, respectively, for the configurations of power generation, power + hydrogen production, power + hydrogen + liquid carbon dioxide production cycle, and power + liquid carbon dioxide production cycle. Integration of carbon dioxide liquefaction cycle into the system is a desirable factor so that causes 30% and 29% reduction in the levelized cost of electricity when it is integrated with power generation, power + hydrogen production. If the cash flow of the system and the levelized cost of electricity are selected as the objective functions in system optimization, the cost of electricity and cash flow will be 0.36 $/kWh and $ 3.8 million at the selected optimal point, respectively.

초임계 조건에서 이산화탄소 혼합물의 점성 측정

The purpose of this study was to experimentally investigate the viscosity for carbon dioxide with nitrogen and methane impurities under supercritical conditions. The experimental setup was comprised of a test section, a condensation section for the liquefaction of carbon dioxide before entering the pump, and a heating section for controlling the temperature of the entrance of the test section. The test section was comprised of a capillary tube with a length of 300 mm and a ⅛ inch diameter. The experiment was performed under a mass flux of 200~400 kg/(m²s) at a impurities concentration of 1.0~5.0 mol%. The viscosity of nitrogen mixture was lower by 0.5% for 1% mole fraction, 4.9% for 3% mole fraction, and 23.5% for 5% mole fraction compared with that of pure CO₂. The viscosity of methane mixture was lower by 7.3% for 1% mole fraction, 11.2% for 3% mole fraction, and 24.4% for 5% mole fraction compared with that of pure CO₂. A model for predicting the viscosity of CO₂ mixtures under the supercritical condition was developed by the multi-variable regression analysis. The model included the non-dimensional parameters for temperature, pressure, and density.

Purification of thermal power plant emissions from carbon dioxide by the liquefaction method as part of a turboexpander unit

The purpose of this work is to estimate the energy costs for the utilization of carbon dioxide generated by thermal power plants operating on various types of fuel by the liquefaction method as part of a turbo-expander installation, as well as a general assessment of the efficiency of the TPP during the utilization of carbon dioxide. The energy costs for the liquefaction of carbon dioxide in the turbo-expander unit from the combustion products of thermal power plants running on coal, natural gas and heating oil differ slightly and amount to about 5 MJ/kg of fuel burned. The practical application of purification of combustion products of thermal power plants from carbon dioxide by the liquefaction method as part of a turboexpander installation is possible as part of combined-cycle power plants with a simultaneous reduction in electrical efficiency by more than 10 % to a level of less than 50 %.

Development of an Integrated Structure for the Tri-Generation of Power, Liquid Carbon Dioxide, and Medium Pressure Steam Using a Molten Carbonate Fuel Cell, a Dual Pressure Linde-Hampson Liquefaction Plant, and a Heat Recovery Steam Generator

Due to the increase in energy consumption and energy prices, the reduction in fossil fuel resources, and increasing concerns about global warming and environmental issues, it is necessary to develop more efficient energy conversion systems with low environmental impacts. Utilizing fuel cells in the combined process is a method of refrigeration and electricity simultaneous production with a high efficiency and low pollution. In this study, a combined process for the tri-generation of electricity, medium pressure steam, and liquid carbon dioxide by utilizing a molten carbonate fuel cell, a dual pressure Linde-Hampson liquefaction plant and a heat recovery steam generator is developed. This combined process produces 65.53 MW of electricity, 27.8 kg/s of medium pressure steam, and 142.9 kg/s of liquid carbon dioxide. One of the methods of long-term energy storage involves the use of a carbon dioxide liquefaction system. Some of the generated electricity is used in industrial and residential areas and the rest is used for storage as liquid carbon dioxide. Liquid carbon dioxide can be used for peak shavings in buildings. The waste heat from the Linde-Hampson liquefaction plant is used to produce the fuel cell inlet steam. Moreover, the exhaust heat of the fuel cell and gas turbine would be used to produce the medium pressure steam. The total efficiency of this combined process and the coefficient of performance of the refrigeration plant are 82.21% and 1.866, respectively. The exergy analysis of this combined process reveals that the exergy efficiency and the total exergy destruction are 73.18% and 102.7 MW, respectively. The highest rate of exergy destruction in the hybrid process equipment belongs to the fuel cell (37.72%), the HX6 heat exchanger (8.036%), and the HX7 heat exchanger (6.578%). The results of the sensitivity analysis show that an increase in the exit pressure of the V1 valve by 13.33% would result in an increase in the refrigeration energy by 2.151% and a reduction in the refrigeration cycle performance by 9.654%. Moreover, by increasing the inlet fuel to the fuel cell, the thermal efficiency of the whole combined process rises by 18.09%, and the whole exergy efficiency declines by 12.95%.

The optimization and thermodynamic and economic estimation analysis for CO2 compression-liquefaction process of CCUS system using LNG cold energy

Compression and liquefaction of carbon dioxide are important parts of the carbon capture, utilization, and storage (CCUS) process. A CCUS project with an actual workload of 1 million tons/year of China is simulated and analyzed in this paper. A new process scheme of compressed liquefaction of CO2 in the CCUS project by using liquid natural gas (LNG) cold energy through CO2 pipeline transportation is proposed to save energy and reduce consumption. The CO2 hydrate prediction models were compared. Based on the thermodynamic path of the CO2 compression liquefaction process, the energy consumption of four process models is compared. The relevant factors, which affect the economy of the new process are investigated, and the technical and economic model is optimized for the new technology scheme of CO2 pipeline. The total cost of the new process of economic is evaluated and the effective quantitative distances for energy saving are obtained. The results show that when the moisture content of CO2 is below 500ppmMol, the new technology will not cause hydrate blockage. The economic viability of the new process (Three stage compression with compressor + liquefaction by using cold energy + pump) is significantly affected by the distance between the LNG receiving station and thermal power plant, and the total cost will be reduced by 30%, 23%, and 8% at a distance of 25, 50 and 100 km, respectively. The distance between LNG receiving station and gas power plant is 125 km, the application of new technology can bring about energy saving and consumption reduction. Through the sensitivity analysis based on NPV and IRR of the new process, the results are economically feasible, and CO2 profit is the most sensitive factor.

Thermodynamic and economic evaluation of biomethane and carbon dioxide liquefaction process in a hybridized system of biogas upgrading process and mixed fluid cascade liquefaction cycle

In recent years, the use of liquefied biogas in the power plant for peak shaving and transportation industries from an environmental and economic perspective has been considered. Simultaneous design of biogas purification and liquefaction processes reduces the number of equipment required and energy consumption. In this paper, a novel purification and liquefaction integrated structure includes a biogas upgrading process by cryogenic separation and amine scrubbing methods and a biomethane liquefaction cycle based on the mixed fluid cascade. In this integrated structure, 2.393 kg/s biogas and 2730 kW power are consumed and 0.5387 kg/s bioLNG, 0.1280 kg/s bioCH4, and 0.2102 kg/s liquid bioCO2 are produced along with 1.625 kg/s hot water. The required cooling of cryogenic biogas upgrading and required heat for the biogas upgrading by amine scrubbing method are provided through mixed refrigerant cascade cycles and waste heat in the integrated structure, respectively. The total thermal energy and exergy efficiencies are 73.11 % and 72.58 %, respectively. The specific power consumption and coefficient of performance of the mixed fluid cascade cycle are calculated to be 0.4761 kW h/kg bioLNG and 3.675, respectively. The economic analysis illustrates that the prime cost of product and return period are 0.2399 US$/kg LNG and 2.122 years, respectively.

Application of advanced exergy analysis for optimizing the design of carbon dioxide pressurization system

The pressurization of carbon dioxide is an integral step of the carbon capture and storage process; a key technology frontier for the decarbonization of power and heat industry. Effective measures to improve the pressurization scheme directly translate into the reduction of process costs. This study aimed to reduce the energy expenditure of the carbon dioxide pressurization process by assisting the conventional carbon dioxide multi-stage compressors with an Ammonia (R717) or Propane (R290) based heat-pump system. In these systems, carbon dioxide is liquefied in the heat-pump after being compressed to an intermediate liquefaction pressure. The liquefied carbon dioxide is subsequently pumped to the target pressure. In this study, the advanced exergy analysis, in addition to the conventional energy analysis is applied to design and optimize the carbon dioxide liquefaction system using a heat pump. The initial conventional exergy analysis reveals that 43.76% of total fuel exergy is destroyed and lost. Subsequently, the advanced exergy analysis is performed to pinpoint the source of total irreversibility (exergy destruction), calculate the avoidable exergy destruction in the system and figure out potential measures to improve the system’s performance. The advanced exergy analysis reveals the avoidable exergy destruction is 48.85% and 51.20% of the total exergy destruction for R290 and R717, respectively. Furthermore, the avoidable exogenous exergy destruction is 16% and 19%, respectively. The results also show that for R717, the extent of improvement is in the following order, Condenser > Compressor > Evaporator > Expansion valve. With this information, a systematic approach is devised and followed to optimize the operating parameters and design of the heat-pump system. Furthermore, in the proposed system, 2328.6 kW of exergy is lost to the environment. To recover this exergy loss, the heat pump-assisted pressurization scheme is integrated with a supercritical carbon dioxide power cycle which generated 1191.00 kW of electric power. The results reveal that the electrical power consumed by the proposed system optimized through advanced exergy analysis is 15.5% lower than that consumed by a benchmark system. The study demonstrates the effectiveness of advanced exergy analysis and the approach presented here can be extended to other energy conversion systems to maximize the energy and exergy savings for sustainable development.

질소 포함 이산화탄소의 증발열전달 특성 연구

The characteristics of boiling heat transfer were experimentally investigated for carbon dioxide with nitrogen impurities. The experimental setup was composed of a test section, a condensation section for the liquefaction of carbon dioxide before entering the pump, and a heating section for controlling the temperature of the entrance of the test unit. The test section was comprised of a double tube heat exchanger. A copper tube with a length of 4 m and a 1/2-inch diameter was located inside and the PVC pipe used for heating was outside. T-type thermocouples were installed in the annulus space of the test section to measure the brine temperature in the PVC and the surfaces of the copper tube. The experiment was performed under a mass flux of 200~700 kg·m<SUP>-2</SUP>s<SUP>-1</SUP> at a nitrogen concentration of 1.0~5.0 mol% and 0.1~0.9 of vapor quality. The boiling heat transfer coefficient of carbon dioxide with impurities decreased by an average of 14.7% compared to pure carbon dioxide.

Novel integrated structure of carbon dioxide liquefaction energy storage system using solar energy

Humans turned to use renewable energies by underground resource reduction and carbon dioxide emissions increase. One of the ways to reduce carbon dioxide and generate power at the consumption peak is using solar energy to compression and liquefaction of carbon dioxide. At the peak power consumption, the liquid carbon dioxide is gasified to generate power. In this article, a new integrated structure for carbon dioxide liquefaction to power generation using parabolic trough solar collectors is developed and analyzed. This process implements an absorption–compression refrigeration cycle that can generate refrigeration of 17.4 MW to liquefy carbon dioxide at -56 °C in the charging mode. In the discharge mode, a two-stage cryogenic ORC plant and a gas turbine power cycle produce 7.872 MW. This integrated structure has an electricity storage efficiency of 67.87% and a round-trip efficiency of 41.22%. Exergy analysis shows that total exergy efficiency and irreversibility are 83.84% and 2265 kW, respectively. HYSYS and TRNSYS software and MATLAB programming with the geographical conditions of Tehran in Iran are used to simulate the process. The economic analysis by the annualized costs of system method shows that the period of return and the prime cost of product are 5.12 years and 8.55 cents per kWh of electricity, respectively. Finally, the effects of the drastic parameters on the performance of the process are studied investigated.

Energy minimization of carbon capture and storage by means of a novel process configuration

Carbon capture and storage is considered a key technology for decarbonizing the heat and power industries and achieving net zero emission targets. However, the significant energy requirements of the process as currently utilized hinders its widespread implementation. This work presents a novel process configuration by which the energy expenditures of carbon capture and storage can be minimized. This configuration is intended to enhance heat integration during the capture process through an innovative combination of three stripper modifications, namely lean vapor compression, a rich solvent split with vapor heat recovery and reboiler condensate heat recovery using a stripper inter-heater in a single flow-sheet. For carbon dioxide compression, a novel pressurization strategy involving carbon dioxide multi-stage compressors, a heat pump system and a supercritical carbon dioxide power cycle was designed and evaluated. The heat pump was used for carbon dioxide liquefaction while the supercritical carbon dioxide power cycle was employed to recover the intercooling heat. Through a comprehensive parametric investigation of the proposed configuration, the optimum value of the key operating parameters i.e., the split fraction, flash pressure, stripper inter-heater location, stripper inter-heater solvent flowrate, carbon dioxide liquefaction pressure and supercritical carbon dioxide cycle turbine pressure ratio were estimated. The performance of the proposed design at the optimized condition was quantified in terms of the reboiler heat duty, the carbon dioxide pressurization power and the equivalent work and compared to a baseline case post-combustion carbon capture and storage process. The proposed case reduced the reboiler heat duty from 3.36 GJ/TonneCO2 to 2.65 GJ/TonneCO2 and the electric power required for carbon dioxide compression from 16,691 kW to 14,708 kW. The results demonstrate that the new design can significantly reduce the reboiler duty, compression power and equivalent work by 21.1%, 11.88%, and 15.8%, respectively.

Conversion and storage of solar energy in the forms of liquid fuel and electricity in a hybrid energy storage system using methanol and phase change materials

The utilization of solar-assisted hybrid energy systems is an appropriate way to generate green power. To this aim, an innovative hybrid charging/discharging system comprised of solar dish collectors, methanol synthesis unit, power cycles, and carbon dioxide liquefaction process as well as phase change materials, is introduced and thermodynamically assessed. An ammonia/water absorption refrigeration cycle is applied for the carbon dioxide liquefaction process. The proposed structure is simulated by using HYSYS, TRNSYS, and MATLAB, and a thermodynamics framework is conducted to assess the integrated system performance. The proposed structure successfully produces 8.449 kg/s and 11.49 kg/s of methanol liquid carbon dioxide, respectively. Energy analysis of this integrated system indicates that, the overall thermal efficiency of the charging and discharging modes are 0.8486 and 0.4076, respectively. The results of exergy evaluation reveal that the largest exergy destruction in the charging and discharging modes are related to collectors with 34.07% and reactors with 56.58%, respectively. In addition, the overall exergy efficiency of the charging and discharging cycles are 57.11% and 42.32%, respectively. A comparison between the proposed system and similar works show that the energy efficiencies of the power cycles are higher than similar studies. Finally, sensitivity analyses on the influence of various parameters such as useful energy collected by collectors, stored heat of phase change materials, solar collector thermal efficiency, irreversibility, and exergy efficiency in the cycle and collector are performed.

Exergy and economic analyses of a novel hybrid structure for simultaneous production of liquid hydrogen and carbon dioxide using photovoltaic and electrolyzer systems

Power-to-X technology that converts renewable electricity to chemicals and liquid fuels will be a key component of the energy turnaround. However, for a successful transition toward fossil-free energy alternatives, serious issues associated with renewable energy storage have to be addressed. Here, we report an innovative power-to-liquid hydrogen and carbon dioxide plant. The proposed integrated plant is composed of five subsystems: power generation using grid-connected solar photovoltaic (PV) subsystem, hydrogen and oxygen gas production using an electrolyzer, oxyfuel power plant for power and heat generation, carbon dioxide liquefaction using an absorption–compression refrigeration subsystem, and a hydrogen liquefaction subsystem. This hybrid structure produces 3.359 kg/s (∼300 ton/day) liquid hydrogen and 10.04 kg/s liquid carbon dioxide. The total exergy efficiency and specific energy consumption of the hydrogen liquefaction system are 94.87% and 3.368 kWh/kgLH2, respectively. Exergy analysis of this integrated structure shows that the largest contribution of exergy destruction (30.58%) is associated with the photovoltaic system and the lowest exergy efficiency (25.28%) belongs to the Turbine in an oxy-fuel subsystem where it, interestingly produces over 70% of the total energy consumption of the plant. Furthermore, the economic analysis of the plant indicates that the time required for the return of capital is 4.794 years, where the prime price of the product and the value added are 0.1921 US$/kgLH2 and 0.5433 US$/kgLH2, respectively. This work can certainly provide a new approach to producing liquid hydrogen and carbon dioxide for long-distance transportation and CO2 reduction using solar as the renewable energy source.

Exergetic and economic evaluation of carbon dioxide liquefaction process in a hybridized system of water desalination, power generation, and liquefied natural gas regasification

In the past, water and energy crises were resolved with fossil fuels and groundwater resources. Nowadays, several research and engineering activities are focusing on combined design of the units and integrated processes due to reduction of underground resources and increased carbon dioxide emissions. In this paper, an integrated structure is developed that includes a cryogenic air separation unit, an organic Rankine cycle (ORC), a liquefied natural gas (LNG) regasification, an oxy-fuel power plant, and a multi effect distillation or desalination (MED). This integrated process produces 309.1 MW power, 17.36 kg/s fresh water, and 88.4 kg/s liquid carbon dioxide. A heat recovery operation on the heat produced from the oxy-fuel power plant is performed to provide the heat required for the ORC, MED unit, and regasification system. In the integrated structure, the total thermal energy and exergy efficiencies are 74.19% and 91.73%, respectively. The exergy analysis of the integrated system reveals that the highest exergy destruction occurs in the reactors with a magnitude of 57.30%, followed by the heat exchanger (14.97%). It is also found that the total thermal energy and exergy efficiencies of the developed integrated configuration are 11.71% and 33.17% higher than those of similar structures reported in the literature. Using the annualized cost method, the economic analysis shows that the investment return period and the prime cost of product are equal to 3.186 years and 0.1480 US$/kWh, respectively. A systematic sensitivity analysis is then conducted to optimize the design and operation of the integrated system. This research work offers useful theoretical and practical tips/guidelines to develop an optimal hybridized process for power generation, carbon dioxide capture, and fresh water production.

Development of a new integrated structure for simultaneous generation of power and liquid carbon dioxide using solar dish collectors

The simultaneous design of units and the integration of processes reduce the amount of required equipment and energy consumption. Types of research in recent years have turned their attention to improving the efficiency of thermal and heat recovery systems. This paper aims to develop an integrated structure for simultaneous generation of power and liquefaction of carbon dioxide. The hybrid system consists of four sections: oxy-fuel power plant for power generation with CO2 capture, pure oxygen production using the air separation unit, carbon dioxide liquefaction system using an absorption refrigeration cycle and heat supply using solar dish collectors. The integrated design has the capacity of producing 26.27 kg/s of liquid carbon dioxide and 179 MW of power. Exergy analysis shows that the maximum exergy destruction belongs to the distillation towers at 24.73%, and the minimum exergy destruction is for air coolers at 0.113% compared to other equipment. Accordingly, the total exergy efficiency of the whole integrated structure is 60.74% and the total exergy destruction is 416 MW. The economic analysis of the integrated structure shows that the period of return is 3.3 years, and the prime cost of the product is 3.04 cents/kWh. Furthermore, by using sensitivity analysis the important and effective parameters of the developed integrated structure was investigated.

Introducing a hybrid oxy-fuel power generation and natural gas/ carbon dioxide liquefaction process with thermodynamic and economic analysis

Oxy-fuel power generation and carbon dioxide capture as a downstream process is a near-zero emission energy system. The captured carbon dioxide can be liquefied but carbon dioxide liquefaction process needs considerable amounts of energy. Liquefied natural gas plays an important role in natural gas transportation. However, its production is known as an energy-intensive process. In this study, a novel integrated process of liquefied natural gas production, oxy-fuel electrical power generation cycle and cryogenic carbon dioxide capture and liquefaction is proposed and investigated by chemical process simulators. Effective operating parameters of the process and its components are thermodynamically analyzed. In this regard, effect of the turbine inlet temperature and pressure ratio, oxidant, oxygen and propane flow rates on the power generation and electrical efficiency of the oxy-fuel cycle, carbon dioxide liquefaction temperature and pressure and liquefied natural gas production rate are examined. The obtained results indicate that, the proposed process can be used to design of the actual plants with optimal operating performance. Specific power consumption of the liquefied natural gas process is about of 0.281 kWh/kg LNG. Also, to verify the accuracy of the process performance, the exergy analysis was performed for the process and all of its components. Through this analysis the exergy efficiency of the oxyfuel power cycle and natural gas liquefaction process are gained 69% and 51% respectively. Economic analysis of the process shows that prime cost of the product and period of return are 0.299US$/kgLNG and 2.392 years respectively.