Natural Gas Cold Energy Research Articles

Study on the process of submerged combustion vaporizer flue gas membrane-cryogenic hybrid carbon capture for coupled liquefied natural gas cold energy power generation

ABSTRACT Under the background of “carbon peaking and carbon neutrality goals,” China has put forward the requirements for the low-carbon development of Liquefied Natural Gas (LNG) industrial chain. Carbon capture technology is an effective means to reduce direct carbon emissions and can promote the decarbonization of the LNG industry chain. So far carbon capture is still an energy-intensive process. Based on the traditional membrane-cryogenic hybrid CO2 capture process, a membrane-cryogenic hybrid CO2 capture process coupled with Liquefied Natural Gas cold energy generation was proposed in this paper. In the proposed process, LNG cold energy and high temperature flue gas heat energy were used to drive Organic Rankine Cycle power generation and reduced carbon capture energy consumption. The effects of key parameters (membrane pressure, membrane temperature, cryogenic pressure, and cryogenic temperature) on the performance of the process (CO2 purity, CO2 recovery, and specific energy consumption) were analyzed by single factor analysis. The process parameters were optimized by response surface analysis, the optimized system resulted in an CO2 purity of 98.39%, CO2 recovery of 90.16%, and specific energy consumption of 605 kJ/kg which was much lower than that of the same type of carbon capture process. This process opens up a new technological path for the development of low energy consumption in carbon capture and the decarbonization of the LNG industry chain, and provides a new solution to meet the challenges in the context of “dual carbon.”

4E assessment of a geothermal-driven combined power and cooling system coupled with a liquefied natural gas cold energy recovery unit

4E assessment of a geothermal-driven combined power and cooling system coupled with a liquefied natural gas cold energy recovery unit

Modeling of Liquefied Natural Gas Cold Power Generation for Access to the Distribution Grid

Cold energy generation is an important part of liquefied natural gas (LNG) cold energy cascade utilization, and existing studies lack a specific descriptive model for LNG cold energy transmission to the AC subgrid. Therefore, this paper proposes a descriptive model for the grid-connected process of cold energy generation at LNG stations. First, the expansion kinetic energy transfer of the intermediate work mass is derived and analyzed in the LNG unipolar Rankine cycle structure, the mathematical relationship between the turbine output mechanical power and the variation in the work mass flow rate and pressure is established, and the variations in the LNG heat exchanger temperature difference, seawater flow rate, and the turbine temperature difference in the cycle system are investigated. Secondly, based on the fifth-order equation of state of the synchronous generator, the expressions of its electromagnetic power, output AC frequency, and voltage were analyzed. Finally, the average equivalent models of the machine-side and grid-side converters are established using a direct-fed grid-connected structure, thus forming a descriptive model of the overall drive process. The ORC model is built in Aspen HYSIS to obtain the time series expression of the torque output of the turbine; based on the ORC output torque, the permanent magnet synchronous generator (PMGSG) as well as the direct-fed grid-connected structure are built in MATLAB/Simulink, and the active power and current outputs of the grid-following-type voltage vector control method and the grid-forming-type power-angle synchronous control method are also verified.

Design, multi-aspect investigation and economic advantages of an innovative CCHP system using geothermal energy, CO2 recovery using a cryogenic process, and methanation process with zero CO2 footprint

The significance of devoting attention to environmental pollution control strategies is widely recognized as an effective means of mitigating the harmful environmental effects caused by fossil fuels in industrial and power plant sectors. Carbon dioxide (CO2) capture and recovery technologies have opened up the possibility of utilizing this pollutant gas. Hence, the current study suggests a methodology for the CO2 hydrogenation of the flue gas leaving a power plant. This approach facilitates methane generation via a methanation reactor, subsequently is utilized as fuel for a power plant. For this purpose, a cryogenic method using liquefied natural gas cold energy facilitates CO2 recovery. Moreover, the whole system utilizes geothermal energy to launch a power plant for power generation and supply the power demands of a hydrogen production unit, relying on a water electrolysis process. The hydrogen generated is employed for CO2 hydrogenation, while the oxygen produced is utilized for the combustion reaction. Heating provider units and an absorption chiller are also included in the design. The system is modeled utilizing Aspen HYSYS software. This study incorporates a sensitivity analysis alongside energy, exergy, environmental, and economic assessments. The energy and exergy efficiencies, as determined by the thermodynamic analysis, are 30.87 % and 48.61 %, respectively. Additionally, according to the economic study, the levelized energy cost amounts to 16.65 $/MWh, demonstrating a substantial reduction of 87.6 % compared to the power generation mode. One notable merit of the suggested system lies in its zero CO2 footprint framework, showing a noteworthy supremacy when compared with previous studies.

Thermodynamic analysis of a cascade organic Rankine cycle power generation system driven by hybrid geothermal energy and liquefied natural gas

The combination of renewable energy and liquefied natural gas (LNG) cold energy can effectively improve energy utilization efficiency and achieve the goal of energy conservation and emission reduction, which is one of the important directions of future development. This work proposed a cascade organic Rankine cycle (ORC) driven by a geothermal heat source and an LNG heat sink. Seven organic fluids are chosen as candidates to form different working fluid pairs. The effects of the main design parameters on system performance are carried out through the thermodynamic analysis. Then, the optimal design conditions and fluid selection schemes are searched based on the single-objective optimization results. Finally, the exergy destruction study is conducted under the optimal design conditions and working fluid pair. Results showed that the cascade ORC system using the working fluid pair of R601/R290 had the highest exergy efficiency, which could reach 20.02%. At the same time, under the optimal design conditions, the secondary cycle condenser and LNG direct expansion brought high exergy destruction, which was respectively 29.3% and 25.8%, and followed by the two turbines in the cascade ORC system, which were 16.1%, 11.2% and 7.7%.

Thermodynamic performance analysis of a new air energy storage multigeneration system

This paper proposes a chemical looping hydrogen generation-solid oxide fuel cell combined cooling, heating, and power system that utilizes compressed air energy storage and liquefied natural gas, aiming to address the issues of instability in renewable energy power generation and waste of liquefied natural gas cold energy. The scheme achieves CO2 capture and efficient power generation while also addressing grid fluctuations and the utilization of waste cold energy. The compressed air energy storage system is employed to supply air centrally, eliminating the power consumption of traditional air compressors while improving discharging efficiency. Aspen Plus software and embedded Fortran are used for system simulation. The system is comprehensively evaluated through energy analysis, exergy analysis, and sensitivity analysis. The results indicate that the discharging efficiency, energy round-trip efficiency, and round-trip electrical efficiency are 87.56%, 81.57%, and 67.82%, respectively. The purity of CO2 capture is 99.72%. Sensitivity analysis indicates that the outlet pressure of the air storage tank and fuel flow are the main influencing parameters for system performance. Increasing the fuel flow can effectively enhance system power output, but efficiency will decrease. The outlet pressure primarily influences the power output of the gas turbine and discharging time. Overall, this system provides theoretical guidance and new ideas for efficient energy utilization.

Thermo-enviro-economic analyses of a landfill biogas-fed polygeneration process combined with a liquefied natural gas cold energy utilization unit

Landfill biogas offers a promising opportunity to supply society’s energy requirements, following the waste-to-energy approach, which issuitable for sustainable production. However, structural modification for its utilization is the main gap, requiring additional research efforts. Considering this issue, the current study aims to design an eco-friendly polygeneration method for landfill biogas utilization for a cutting-edge heat recovery system that integrates a cold energy recovery and utilization unit for liquefied natural gas. The liquefied natural gas recovery section, the organic Rankine cycle with a zeotropic mixture, and the Kalina cycle are all started using the flue gas from the combustion of biogas in a cascade process. In addition, the waste heat of the Kalina cycle is recovered by a single-effect desalination cycle and liquefied natural gas recovery section. Also, a water electrolysis process is integrated into the whole system. As a result, the products include hydrogen, electricity, natural gas, hot and cold water, and freshwater. The Aspen HYSYS software is utilized to design the system and investigate its thermodynamic, environmental, and economic aspects. The results demonstrate an energy efficiency of 57.54 % and an exergy efficiency of 18.78 %. Also, the carbon dioxide footprint associated with the system equals 0.34 kg/kWh, and the specific cost of products is 73.96 $/GJ. An optimal exergy efficiency of 25.8 % and a specific cost of products of 69.7 $/GJ are obtained by means of an intelligent optimization approach that ultimately makes use of non-dominated sorting genetic algorithm-II and artificial neural networks.

Comparison and analysis on comprehensive performance of CO2 multiphase refrigeration systems using liquefied natural gas cold energy

In order to fully apply liquefied natural gas (LNG) cold energy to the refrigeration system, four different types of CO2 multiphase refrigeration systems using LNG cold energy are designed. In this paper, (1) CO2 single-stage compressed solid and gas phase refrigeration cycle (SSCC1), (2) CO2 single-stage compressed solid and solid phase refrigeration cycle (SSCC2), (3) CO2 double-stage compressed solid and gas phase refrigeration cycle (DSCC1), and (4) CO2 double-stage compressed solid and solid phase refrigeration cycle (DSCC2) are combined with CO2 liquid phase secondary refrigerant cycle (RC), respectively, to effectively use LNG cold energy. The performance analysis, exergy analysis, economic analysis, and CO2 emission analysis of the proposed systems are carried out by establishing the mathematical models. The results show that the intermediate pressure of DSCC1-RC and DSCC2-RC reaches the best performance at 0.3 MPa, and the system performance decreases with the increase in intermediate temperature. The refrigerating capacity of the CO2 liquid phase secondary refrigerant cycle, the COP, and the exergy efficiency of four kinds of CO2 multiphase refrigeration systems decrease with the increase in the refrigerating capacity of the CO2 refrigeration cycle, while the power consumption of SSCC2-RC and DSCC2-RC decreases, SSCC1-RC and DSCC1-RC increased. The system with the shortest exergy loss is DSCC2-RC at 654.01 kW, while the system with the shortest payback period is SSCC2-RC at 0.88 years, and DSCC2-RC has the smallest CO2 emission. Four CO2 multiphase refrigeration systems and the ammonia combined refrigeration system with the same total refrigerating capacity are compared and analyzed, respectively; the results show that the performance, economy, and CO2 emission of CO2 multiphase refrigeration system are better than those of ammonia combined refrigeration system; and the exergy loss of CO2 multiphase refrigeration system is generally larger than that of ammonia combined refrigeration system because of the large temperature difference in heat transfer.

Thermodynamic analysis of trigeneration system with controlled thermal-electric ratio by coupling liquefied natural gas cold energy and biomass partial gasification

Efficient utilization of biomass energy is crucial for addressing environmental challenges. However, the low calorific value of syngas from biomass gasification poses subsequent utilization issues. This study proposes a trigeneration system integrating biomass partial gasification and LNG cold energy to address surge problems using syngas combined cycle systems. The design includes air separation units, combined cycle, and biomass gasifier, achieving an adjustable thermal-electric ratio. An air separation unit and two-stage Organic Rankine Cycle fully utilize LNG cold energy. A thermodynamic model was established in Aspen Plus, and energy, exergy, and economic analyses were conducted to assess feasibility, followed by a sensitivity analysis. Results show that with a mix burning ratio and carbon conversion rate of 0.6 and 0.7, the system's exergy, energy, and electrical efficiencies are 36.94 %, 60.14 %, and 33.32 % in cooling mode. The unit exergy cost and CO2 emissions are 0.0748$ and 95.29 kg/s, respectively. Analysis reveals variations in efficiency and outputs with changes in mix burning ratio and carbon conversion rate. Adjusting operational parameters enhances the system's ability to regulate the thermal-electric ratio, demonstrating its potential for efficient biomass energy utilization and environmental sustainability.

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.

Thermodynamic and parametric analyses of a zero-carbon emission SOFC-based CCHP system using LNG cold energy

A novel zero-carbon emission combined cooling, heating and power (CCHP) system is currently proposed. The thermal energy of the solid oxide fuel cell (SOFC) exhaust is recovered in a transcritical CO2 (T- CO2) power cycle. Relying on the efficient utilization of liquefied natural gas (LNG) cold energy, CO2 capture has been achieved at low energy consumption. The thermodynamic performance is evaluated by using energy and exergy analysis methods for this hybrid process. The electrical, exergy, and CCHP efficiencies are obtained as 60.37 %, 62.83 %, and 79.09 %, respectively. The CO2 condenser, with the largest exergy destruction ratio (18.60 %) and a low exergy efficiency (37.16 %), is regarded as the weakest point in terms of thermodynamic perfectibility. In addition, the influences of the current density, stack temperature and pressure, and fuel utilization rate have also been studied from different aspects of system performance. The current density, stack temperature, stack pressure, and fuel utilization rate are recommended as 0.3 A/cm2∼0.4 A/cm2, 900 °C, 5 bar, and 85 %, respectively. This research provides practical reference and pragmatic guidance for the integration, analysis, and optimization of SOFC-based CCHP systems.

Simulation study of a novel methanol production process based on an off-grid Wind/Solar/Oxy-fuel power generation system

Power-to-methanol technology represents a promising energy storage solution to manage the fluctuating supply and demand of renewable energy effectively. A novel methanol production process based on an off-grid wind/solar/Oxy-fuel power plant is presented in the paper, which consists of solar-wind energy, oxy-fuel combined cycle, proton exchange membrane electrolyzer, and carbon dioxide hydrogenation to methanol unit. The hydrogen produced by the proton exchange membrane electrolyzer is used to synthesize methanol, and the by-product oxygen is used in the oxy-fuel combined cycle. At the same time, low-cost carbon capture is achieved with liquefied natural gas cold energy utilization, and the collected carbon dioxide is used to synthesize methanol. The system carbon emission is negative, about −0.344 kg carbon dioxide/kg methanol, the system has no other products except methanol. The structure of renewable energy has a significant impact on the technical and economic performance of the system. Therefore, a comparative analysis of different wind/photovoltaic installed capacity ratios is carried out. The case study shows that the proposed system has the best performance when the wind/photovoltaic installed capacity ratio is 25 %/75 %, with a renewable energy utilization of 97.62 %, methanol production cost of 1.34 $/kg methanol, and an energy efficiency of 63.5 %. The proposed system may be a practical solution for methanol production from renewable energy.

Design and analysis of steam methane reforming hydrogen liquefaction and waste heat recovery system based on liquefied natural gas cold energy

To improve the utilization rate of liquefied natural gas (LNG) cold energy, reduce hydrogen (H2) liquefaction cost, recover waste heat and reduce carbon dioxide (CO2) emission, this study designs a steam methane reforming (SMR) H2 liquefaction and waste heat recovery system based on LNG cold energy for the production of 10 tons of liquid hydrogen (LH2) per day. Parameters analyses and optimization, exergy analyses and economic analyses of the system are carried out and compared with other H2 liquefaction systems. The results show that: under the optimal conditions, the values of specific energy consumption (SEC), coefficient of performance (COP) and exergy efficiency (ƞex) were 5.93 kWh/kg LH2, 0.2225 and 53.24%, respectively. Exergy losses of system is mainly distributed in heat exchange equipment and compressors. Decreasing the heat exchange equipment cold and heat sources inlet temperature difference and reducing the compressors compression ratio were beneficial to reduce equipment exergy losses. The pre-cooling performance of LNG is better than that of liquid nitrogen (LN2) and mixed refrigerant (MR). Compared with the pre-cooling H2 liquefaction system without waste heat recovery, the SEC decreased by 0.26 kWh/kg LH2 and ƞex increased by 2.28%. Research results are conducive to resource conservation and environmental protection.

Introducing and performance evaluation of a novel Multi-Generation process for producing Power, fresh Water, oxygen and nitrogen integrated with liquefied natural gas regasification and carbon dioxide removal process

The objective of this paper is to develop and evaluate a new integrated multigenerational system comprised of cryogenic air separation, hydrate-based desalination, combined cycle and oxyfuel power plants, carbon dioxide amine absorption, and transcritical carbon dioxide power cycle, employing liquefied natural gas cold energy. This integrated multi-generation system, applicable for liquefied natural gas importer terminals with access to seawater, produces approximately 2,533 MW net output power and 1,985 kg/h fresh water. In addition, this integrated multi-generation process produces 16,735,861 kg/h high-purity liquid oxygen (100 mol%), 4,773,633 kg/h liquid nitrogen with 99.71 mol% purity, more than 31,724,465 kg/h high-purity gaseous nitrogen (99.9 mol%), and 90,903,230 kg/h low-purity gaseous nitrogen (83.38 mol%). About 5907.3 MW of produced power is generated by liquefied natural gas expander. The performance of this system is evaluated by energetic methods. The results of energy analysis show the specific energy consumptions of the air separation products are 0.551 kW/kg and 1.93 kW/kg for liquid oxygen and nitrogen, respectively. Moreover, in the hydrate-based desalination subsystem, the specific energy consumption is 0.5 kW/m3 for produced pure water. The combined cycle power plant includes two gas turbines, three steam turbines, and a three-pressure level heat recovery steam generation. The thermal efficiencies of gas turbine cycles (Bryton), steam turbine cycles (Rankine) and combined power cycles are 26.3 %, 29.6 %, and 36.2 %, respectively. The flue gases from power plants enter the carbon dioxide amine absorption subsystem. The separated carbon dioxide is used as a working fluid to produce 372.1 MW power in transcritical carbon dioxide cycle. The results of energy analysis for carbon dioxide amine absorption subsystem show that the specific energy consumption, the ratio of captured carbon dioxide per unit mass of liquefied natural gas and the carbon dioxide removal efficiency are 6.60 kW/kg, 33.91 kg/tone, and 90.06 %, respectively. Approximately 2,905,000 kg/h of liquid carbon dioxide is obtained as the byproduct of this multi-generation process. Additionally, sensitivity analysis is conducted to determine key parameters influencing the main energetic indexes. Finally, the amount of attainable regasified natural gas reaches 257,523 tone/h by applying this multi-generation system with total 86 % energy efficiency.

Realization of high cryogenic thermoelectric performance for MgAgSb base alloy by regulation heat-treatment process

MgAgSb alloy has attracted wide attention due to its inherent low thermal conductivity, excellent thermoelectric (TE) properties, and environmental friendliness. Although the TE performance has been deeply investigated for the temperature range over 300–700 K, while cryogenic range has seldom report. In this study, a systematic investigation on cryogenic TE performance of α-MgAgSb has been performed. α-MgAgSb alloy has been synthesized by ordinary ball milling followed spark plasma sintering process and then further regulated by heat treatment. The power factor of MgAgSb alloy after 10 days of heat-treating increased by 230%, which is attributed to the reduction of the impurity phase and the improvement of the crystallinity achieved by the optimization of heat treatment. The total thermal conductivity decreased by 18% to 1.15 W m−1 K−1, and the maximum ZT reached 0.264 at 173 K, which is 300% enhancement to untreated one. The ZTavg reached to 0.45 over 173–298 K, located at the pinnacle among cryogenic TE materials. In addition, the ZTeng value of 0.23 related to the highest device conversion efficiency of 5.2% demonstrates good device potential. This work reveals that the purity and the cryogenic TE properties of α-MgAgSb alloy can be effectively improved by heat-treating, and demonstrates the greatly potential of MgAgSb materials in the field of liquefied natural gas's cold energy recovery.

Evaluations of energy, exergy, and economic (3E) on a liquefied natural gas (LNG) cold energy utilization system

The LNG cold energy utilization system primarily integrates additional power cycles during the gasification process to harness the cold energy released in this process efficiently. This study introduces a combined cooling and power (CCP) system, which comprises a cascade organic Rankine cycle (ORC), an air conditioning refrigeration (ACR), and a direct expansion cycle (DEC). Furthermore, the thermodynamic and economic analyses of the CCP system were evaluated, and the optimization of each influence parameters was performed by the genetic algorithms, such as the composition of the quaternary mixed working fluid (Methane: Ethane: Propane: i-Butane), condensation pressure, evaporation pressure, and the first-stage expansion pressure within the system. According to the simulation results, the suggested overall exergy destruction of the CCP system proposed by this work is reduced by 13.18% under optimized conditions, with a maximum net power generation of 230.38 kW and an exergy efficiency of 45.58%. Economic analysis reveals that the system's investment cost, annual economic benefits, and levelized energy cost are 2.02 × 106 $, 2.75 × 105 $, and 0.10 $/kWh, respectively. With the system's official operation, the investment cost will be recovered within 8.61 years.

Design and thermo-enviro-economic analyses of a novel thermal design process for a CCHP-desalination application using LNG regasification integrated with a gas turbine power plant

Designing and studying processes with reduced thermodynamic irreversibility and environmental impact is imperative to improve the global applicability of the stand-alone gas turbine cycles. Hence, the present study introduces a novel cascade heat integration tool for a gas turbine cycle combined with a liquefied natural gas cold energy utilization and regasification process. A saltwater desalination subsystem, an absorption chiller, and an organic Rankine cycle are also included in the integrated system. Therefore, the developed system demonstrates an environmentally friendly combined cooling, heating, power, and freshwater production framework, improving the performance of the system in comparison to previous research. This configuration is simulated within the Aspen HYSYS software for comprehensive energy, exergy, environmental, and economic assessments. The findings demonstrate that the whole configuration yields energy and exergy efficiencies of 92.92% and 63.5%, respectively. In comparison, these efficiencies in the single-generation mode are found to be 45.92% and 43.72%, correspondingly. The environmental analysis reveals that the carbon dioxide footprint equals 0.1792 kg/kWh when operating in the multigeneration mode and 0.4591 kg/kWh in the single-generation mode. Furthermore, the economic evaluation exhibits that the cost of energy equals 67.2 $/MWh and 135.92 $/MWh for the multigeneration and single-generation operational modes, respectively.

Thermo-enviro-economic analysis of a novel landfill gas-fueled CCHP-desalination process combined with a liquefied natural gas cold energy recovery unit

This paper proposes utilizing landfill gas, obtained from landfilling activities, as a viable substitute for fossil fuels. In this study, an innovative heat design process for a landfill gas-fueled power plant is employed, representing a novel contribution to system development. The innovative cascade heat recovery process utilized in this method facilitates an eco-friendly multigeneration practice, resulting in reduced thermodynamic irreversibility and air pollution as well as an increase in the capacity of main products. Hence, the entire system consists of a bio power plant, a transcritical CO2 cycle, a low-pressure steam generation unit, a refrigeration cycle, a multi-effect desalination, and a liquefied natural gas cold utilization unit. The simulation is conducted by the Aspen HYSYS software, examining various aspects such as energy, exergy, economics, and environment. The results indicate that the energy and exergy efficiencies of the process are 79.96% and 32.93%, respectively. Moreover, the cost per unit exergy and specific CO2 emissions amount to 87.16 $/GJ and 0.2732 kg/kWh, respectively. Besides, a parametric study is performed based on the gas turbine's outlet pressure, the flue gas temperature leaving the transcritical CO2 cycle and multi-effect desalination, and the liquefied natural gas flow rate. Obtained results demonstrate that the specific CO2 emissions and cost per unit exergy face an increase with increasing the gas turbine's outlet pressure. Moreover, the increase in the flue gas temperature leaving the transcritical CO2 cycle exhibits a reduction in the CO2 emissions and an escalation in the cost per unit exergy.

Performance analysis of a modified Allam cycle combined with an improved LNG cold energy utilization method

The Allam cycle is a promising power cycle that could achieve 100% carbon capture as well as high efficiency. In order to further enhance system operating performance, here we propose a modified Allam cycle with an improved liquified natural gas (LNG) cold energy utilization method. The flow rate fluctuation of LNG is suppressed by variable speed adjustment of the air compressor, and the cold energy of LNG is transferred to liquid oxygen, which could implement a stable cold energy supply. The whole process is modeled including air separation unit and LNG supply path. Furthermore, the system thermodynamic and economic performance is evaluated through parametric analysis, and the proposed system superiority is highlighted by comparing with conventional Allam-LNG cycle. The results indicate that the system could achieve 70.93% of net thermal efficiency, 65.17% of electrical efficiency, and $403.63 million of net present value, which performs 5.76% and 6.48% enhancement of efficiency and 11% improvement of economic revenue. Moreover, the system off-design operation is assessed; 87% to 100% of compressor speed adjustment range is determined that could cope with −13% to 9% of LNG flow rate fluctuation.

A fuel gas waste heat recovery-based multigeneration plant integrated with a LNG cold energy process, a water desalination unit, and a CO2 separation process

Development of the multigeneration plants based on the simultaneous production of water and energy can solve many of the current problems of these two major fields. In addition, the integration of fossil power plants with waste heat recovery processes in order to prevent the release of pollutants in the environment can simultaneously cover the environmental and thermodynamic improvements. Besides, the addition of a carbon dioxide (CO2) capturing cycles with such plants is a key issue towards a sustainable environment. Accordingly, a novel waste heat recovery-based multigeneration plant integrated with a carbon dioxide separation/liquefaction cycle is proposed and investigated under multi-variable assessments (energy/exergy, financial, and environmental). The offered multigeneration system is able to generate various beneficial outputs (electricity, liquefied CO2 (L-CO2), natural gas (NG), and freshwater). In the offered system, the liquified natural gas (LNG) cold energy is used to carry out condensation processes, which is a relatively new idea. Based on the results, the outputs rates of net power, NG, L-CO2, and water were determined to be approximately 42.72 MW and 18.01E+03, 612 and 3.56E+03 kmol/h, respectively. Moreover, the multigeneration plant was efficient about 32.08% and 87.72%, respectively, in terms of energy and exergy. Economic estimates indicated that the unit product costs of electricity and liquefied carbon dioxide production, respectively, were around 0.0466 USD per kWh and 0.0728 USD per kg-CO2. Finally, the total released CO2 was about 0.034 kg per kWh. According to a comprehensive comparison, the offered multigeneration plant can provide superior environmental, thermodynamic, and economic performances compared to similar plants. Moreover, there was no need to purchase electricity from the grid.