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Moonyong Lee - One of the best experts on this subject based on the ideXlab platform.

  • impact of Mixed Refrigerant selection on energy and exergy performance of natural gas liquefaction processes
    Energy, 2020
    Co-Authors: Ning Mao, Moonyong Lee, Muhammad Abdul Qyyum, Zuming Liu, Ashak Mahmud Pravez
    Abstract:

    Abstract Selection of Mixed Refrigerant has a significant impact on the performance of the single Mixed Refrigerant process for natural gas liquefaction. However, current studies mainly focus on optimizing the fraction of the Mixed Refrigerant with pre-fixed components which cannot guarantee the optimal solution. To address this issue, a simulation-based optimization methodology was proposed for simultaneously determining the components and their respective fractions in a Mixed Refrigerant. The methodology selected the optimal Mixed Refrigerant components from a database of the potential Refrigerants with different objective functions. Then, four case studies of Mixed Refrigerants with three, four, five, and six components were optimized to determine their optimal combination of components and the fraction of each component by minimizing the specific energy consumption. Subsequently, the energetic and exergetic analyses were conducted to reveal the relationships between the Mixed Refrigerant components and the process performance. The results showed that the minimum specific energy consumption for the Mixed Refrigerant comprising three, four, five and six components was 0.721 (A3), 0.403 (B10), 0.392 (C10) and 0.343 (D14) kWh/kg respectively. The specific energy consumption declined drastically by 44.11% in moving from three (A3) to four (B10) components, with a less pronounced decrease of 14.9% in moving from four (B10) to six (D14) components. Moreover, the exergy efficiency of A3, B10, C10, and D14 was 36.74, 55.39, 56.44, and 61.66%, respectively. The results indicated that the energetic and exergetic efficiencies were severely influenced by the selection of components for the Mixed Refrigerant. Therefore, the proposed methodology provides a viable method of simultaneously determining the Refrigerant components and fractions for Mixed Refrigerant-based processes to achieve the minimum specific energy consumption and maximum exergy efficiency.

  • dual Mixed Refrigerant lng process uncertainty quantification and dimensional reduction sensitivity analysis
    Applied Energy, 2019
    Co-Authors: Muhammad Abdul Qyyum, Sanggyu Lee, Le Quang Minh, Pham Luu Trung Duong, Moonyong Lee
    Abstract:

    Abstract The dual Mixed Refrigerant (DMR) liquefaction process is complicated and sensitive compared to the competitive propane pre-cooled Mixed Refrigerant liquefied natural gas (LNG) process. When any uncertainty is introduced to the process operation conditions, it is necessary for the DMR process to be re-optimized to maintain efficient operation at a minimal cost. However, in actual operation, re-optimization is a challenging task when the process operational input variables are varied, typically owing to the lack of information regarding the nature, impact, and levels of uncertainty. Within this context, this study investigates the uncertainty levels in the overall energy consumption and minimum internal temperature approach (MITA) inside LNG heat exchangers with variations in the operational variables of the DMR processes. Moreover, a global sensitivity analysis is conducted to identify the influence of random inputs on the process performance parameters. The required energy is significantly influenced by the variations in the variables in the cold Mixed Refrigerant (approximately 63%), while changes in the warm Mixed Refrigerant (WMR) section only slightly affect the uncertainty of the required specific energy. Furthermore, the probability distribution of the approach temperature (MITA1) inside the WMR exchanger is mainly affected by changes in the compositions of methane, ethane, and propane, as well as the high pressure of the cold Mixed Refrigerant (approximately 97%). Conversely, the flow rate of ethane and low pressure of the WMR significantly affect the uncertainty of the approach temperature (MITA2) inside the cold Mixed Refrigerant exchanger.

  • coal to clean energy energy efficient single loop Mixed Refrigerant based schemes for the liquefaction of synthetic natural gas
    Journal of Cleaner Production, 2019
    Co-Authors: Muhammad Abdul Qyyum, Wahid Ali, Kinza Qadee, Yus Donald Chaniago, Moonyong Lee
    Abstract:

    Abstract Higher air-pollutant (CO2, SO2, particulates, etc.) emission from coal burning prohibits the direct use of coal. The demand for clean and sustainable energy is increasing with the growth of population and living standards. Considering the current energy challenges, coal-enriched countries have focused on the green utilization of coal by converting it to a clean energy source, such as synthetic natural gas (SNG). To fulfill the global clean energy demand, liquefaction is a promising and feasible approach enabling safe storage and transportation. However, the liquefaction of SNG is an energy- and cost-intensive process, primarily owing to the presence of low-boiling impurities such as hydrogen and nitrogen. This paper describes the major challenges and issues associated with the SNG liquefaction process for its commercialization and attempts to solve the issues inherent to the SNG liquefaction industry. The optimal energy-efficient single-loop Mixed-Refrigerant-based liquefaction schemes, with the separation of low-boiling impurities (hydrogen and/or nitrogen), are presented as a major contribution of this study. The proposed SNG liquefaction schemes are analyzed in comparison with the latest SNG liquefaction study. Liquefied SNG can be produced with energy savings of up to 30.4% compared to the published base case.

  • hydrofluoroolefin based novel Mixed Refrigerant for energy efficient and ecological lng production
    Energy, 2018
    Co-Authors: Muhammad Abdul Qyyum, Moonyong Lee
    Abstract:

    Abstract To satisfy the worldwide demand for energy, the liquefied natural gas (LNG) industry has grown significantly in the past three decades owing to its low CO2 emissions and high thermal efficiency compared to the other available energy resources. However, the process of natural gas liquefaction is generally considered to be energy-intensive. In this context, a novel hydrofluoroolefin (HFO-1234yf)-based Mixed Refrigerant, with the advantages of zero ozone depletion and minimal global warming potential, is proposed to liquefy natural gas in an ecological and energy-efficient manner. A new liquefaction cycle using the HFO-based Mixed Refrigerant is developed to fully utilize its potential. The results reveal that the overall energy requirement for natural gas liquefaction can be reduced by 46.4% compared with a single Mixed Refrigerant process, 42.5% compared with a dual Mixed Refrigerant process, and 36.3% compared with the Linde–single Mixed Refrigerant process. Economic analysis based on the capacity parameters of each equipment is also performed to emphasize the commercial feasibility of the proposed LNG process. The proposed HFO-based Mixed Refrigerant system provides an innovative solution to improve the ecological aspects and energy efficiency of natural gas liquefaction processes.

  • energy efficiency enhancement of a single Mixed Refrigerant lng process using a novel hydraulic turbine
    Energy, 2018
    Co-Authors: Muhammad Abdul Qyyum, Nguye Van Duc Long, Wahid Ali, Mohd Shariq Kha, Moonyong Lee
    Abstract:

    Abstract The advancement in hydraulic turbine (HT) technology was exploited for energy and cost benefits in natural gas liquefaction. Replacing the conventional Joule–Thompson (JT) valve with HT has the potential to recover the work input. This research investigated the effect of replacing the JT valve with HT in the energy efficiency enhancement of a single Mixed Refrigerant (SMR) process. To fully take the potential benefit of the HT, the proposed SMR schemes were optimized by using a modified coordinate descent optimization method, which was implemented in Microsoft Visual Studio environment and linked to the rigorous HYSYS® model. The results showed that the required energy of the proposed HT based SMR process could be saved up to 16.5% in comparison with the conventional SMR process using the JT valves. Utilization of the recovered energy into boosting the natural gas feed pressure could further reduce the energy requirement up to 25.7%. Exergy efficiency analysis also showed that whole exergy efficiency of the enhanced SMR process can be increased by about 11% as compared to the base case. The proposed HT based liquefaction technology can be extended to other natural gas liquefaction processes as an attractive option for enhancing the energy efficiency.

Maoqiong Gong - One of the best experts on this subject based on the ideXlab platform.

  • thermodynamic analysis of a petroleum volatile organic compounds vocs condensation recovery system combined with Mixed Refrigerant refrigeration
    International Journal of Refrigeration-revue Internationale Du Froid, 2020
    Co-Authors: Haocheng Wang, Hao Guo, Yanxing Zhao, Xueqiang Dong, Maoqiong Gong
    Abstract:

    Abstract Thermodynamic analysis of a volatile organic compounds (VOCs) condensation recovery system combined with Mixed-Refrigerant J-T (MRJT) refrigeration is illustrated in this paper, which provides an effective and economical choice for petroleum plants. VOCs is compressed, cooled by its recuperation process and separated in two simple rectification columns with 3–5 stages. The cooling powers for condensers at column top are provided by a high efficiency dual MRJT refrigerator at 100 K and 232 K, respectively. The cooling and separation characteristics of petroleum VOCs are also analyzed comprehensively. It is indicated that most of VOCs condensation load locates in high temperature region (≥ 235 K approximately). It might be feasible to cool VOCs from 235 K to 110 K by cold purified air through recuperation. For a typical petroleum VOCs, non-methane hydrocarbon residual of 56 mg Nm−3 is achieved with specific power consumption (SPC) of 0.1289 kWh Nm−3, free of additional purifying units. According to the analysis on the effects of variable VOCs composition and pressure, the cooing loads of top condensers are close related to the performance of VOCs recuperation. C1 and C2 are key components to enhance recuperation at low temperatures and reduce SPC. Exceed C3 could enlarge cold stage condenser load and SPC due degraded cold stage recuperation; while exceed C4-C6 could reduce condenser loads and SPC. Higher VOCs pressure could also decrease SPC.

  • thermodynamic comparison of small liquid nitrogen generators driven by Mixed Refrigerant j t refrigerators and gas expansion cycles
    IOP Conference Series: Materials Science and Engineering, 2020
    Co-Authors: Haocheng Wang, Hao Guo, Gaofei Che, Qinglu Song, Maoqiong Gong
    Abstract:

    The thermodynamic comparison of small Mixed-Refrigerant J-T (MRJT) and gas expansion (Kapitza cycle) LN2 generators are conducted by the exergy method in this paper. Both of two types are employed for low pressure N2 liquefaction and air separation (< 9.0 bar). Pure N2, PSA units or cryogenic air separation columns are used for LN2 production. The MRJT type is driven by single-stage compressors. It is indicated that the efficiency of MRJT type is higher than Kapitza type. With pure N2 at 8.0 bar, the figures of merit (FOM) of MRJT and Kapitza types are 26.86% and 12.79%, respectively. With mini air separation columns, the FOM of MRJT and Kapitza types are 21.42% and 11.34%, respectively. The large exergy losses in the compressor unit and non-isentropic expansion are the main reasons of the inferior efficiency of the Kapitza type. In addition, the Kapitza type requires larger total compressor displacement than the MRJT type. The MRJT type is recommended to be used in small LN2 generators.

  • development and performance test of a miniature movable Mixed Refrigerant liquid nitrogen generator
    Cryogenics, 2018
    Co-Authors: Haocheng Wang, Hao Guo, Gaofei Che, Y X Zhao, Maoqiong Gong
    Abstract:

    Abstract In order to cover long-term but small quantity liquid nitrogen requirements of laboratory or field users, a miniature movable Mixed-Refrigerant liquid nitrogen generator (MRLN) was developed and tested here, based on a precooled Mixed-Refrigerant J-T (MRJT) refrigerator. With the full air-cooled, skid-mounted structure, this MRLN was built utilizing off-the-shelf refrigeration components like commercial single-stage oil-lubricated compressors to reduce construction cost greatly. Bottled pure N2, pressure swing adsorption (PSA) unit and mini cryogenic rectification column could be employed to supply N2 in different operation modes respectively. In pure N2 mode, N2 was directly liquefied by the MRJT refrigerator. With feed N2 at 0.8 MPa, the specific power consumption (SPC) was 1.79 kWh L−1, and figure of merit (FOM) was 6.27%. The estimated SPC in PSA mode was 2.68 kWh L−1. For column mode, the SPC was 4.59 kWh L−1, with FOM of 3.38%. A closed N2 cycle could convey cooling capacity between flammable Refrigerant and air. This MRLN could be a convenient and low-costing choice for some liquid nitrogen users.

  • thermodynamic design and analysis of movable small scale Mixed Refrigerant liquid nitrogen generators
    International Journal of Refrigeration-revue Internationale Du Froid, 2018
    Co-Authors: Haocheng Wang, Hao Guo, Gaofei Che, Y X Zhao, Xuezhi Dong, Maoqiong Gong, O Gao
    Abstract:

    Abstract Thermodynamic design and analysis of small scale liquid nitrogen generators based on Mixed-Refrigerant Joule–Thomson cycle (MR JT) are illustrated in this paper, providing low-cost choices for remote and field users. Bottled pure nitrogen, PSA unit or mini air separation column are utilized in different processes, with feed gases liquefied in the MR JT refrigerators driven by single-stage compressors. Problems in the application of low pressure gas source and mini column are investigated, including column simplification, air liquefaction in flammable MR JT, etc. System exergy analysis is conducted. For pure N2 at 8.0 bar, specific power consumption (SPC) of 0.53 kWh L−1 and figure of merit (FOM) of 24.46% are achieved. With PSA unit, SPC is 0.85 kWh L−1. In the process with column, a closed N2 cycle is employed to deliver cooling capacity from flammable Mixed-Refrigerant to air. Optimal SPC of 0.84 kWh L−1 and FOM of 19.96% are reached.

  • experimental investigation on the miniature Mixed Refrigerant cooler driven by a mini compressor
    Tri-Technology Device Refrigeration (TTDR) III, 2018
    Co-Authors: Gaofei Che, Maoqiong Gong
    Abstract:

    Three miniature Joule-Thomson cryogenic coolers and a testing set up were built to investigate the cooling performance in this work. Shell-and-tube heat exchanger and plate fin heat exchangers with rectangular micro channels were designed to achieve high specific surface area. The main processing technology of micro Mixed Refrigerant cooler (MMRC) was described. The design and fabrication processing of the plate fin heat exchangers were also described. The new developed micro plate-fin type heat exchanger shows high compactness with the specific heat surface larger than 1.0x104 m 2 /m 3 . The results of experimental investigations on miniature Mixed Refrigerant J-T cryogenic coolers driven by a Mini-Compressor were discussed. The performance evaluation and comparison of the three coolers was made to find out the features for each type of cooler. Expressions of refrigeration coefficient and exergy efficiency were pointed out. No-load temperature of about 112 K, and the cooling power of 4.0W at 118K with the input power of 120W is achieved. The exergy efficiency of the SJTC is 5.14%.

Jinping Liu - One of the best experts on this subject based on the ideXlab platform.

  • a strategy to optimize the charge amount of the Mixed Refrigerant for the joule thomson cooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2016
    Co-Authors: Weiqiang Pang, Jinping Liu
    Abstract:

    Abstract The performance of the Mixed Refrigerant (MR) Joule–Thomson cooler is mainly dependent on the MR circulation composition for a given hardware. However, it is difficult to charge the MR to the desired circulation composition, due to the composition shift. In the present study, a novel strategy was proposed to solve this problem. In this strategy, the MR Joule–Thomson cooler is first charged with the initial charge amount, which is obtained by estimating the MR inventory in the cooler using the homogeneous model. Afterwards, the cooler is started and the MR circulation composition is adjusted to the corresponding optimal composition by adding the MR charge amount stepwise. Additionally, this strategy was verified by an experiment with a ternary mixture of methane, ethane and i-butane. The experimental results indicated that the MR circulation composition was able to be adjusted to the corresponding optimal circulation composition approximately within the relative deviation of ±5%.

  • Robustness analysis of the Mixed Refrigerant composition employed in the single Mixed Refrigerant (SMR) liquefied natural gas (LNG) process
    Applied Thermal Engineering, 2016
    Co-Authors: Le Cao, Jinping Liu, Xiongwen Xu
    Abstract:

    The SMR system is widely used in the small- and medium-scale LNG plants. The optimization of the Mixed Refrigerant composition is a multi-variable, nonlinear and strong coupling issue. The optimization of the Mixed Refrigerant composition can reach high exergy efficiency by making the heat exchange curves match rationally. However, adjusting the Mixed Refrigerant composition in a practical SMR system is very complex. In this paper, the robustness of the Mixed Refrigerant composition was mainly investigated by optimizing the SMR system with GA and Aspen Plus. The degree of freedom in the variables was reduced to verify the robustness of the Mixed Refrigerant, and to ensure that the control and adjustment will be convenient and reliable. The results showed that the robustness of the Mixed Refrigerant composition was very strong because the exergy efficiency is maintained about 0.40, even though the ratio of the Mixed Refrigerant was restrained. This work discusses both the heat exchange process and the exergy loss in the recuperative heat exchanger. Meanwhile, a novel method for adjusting the Mixed Refrigerant is proposed to achieve a high efficiency in the SMR system.

  • Experimental study on the Mixed Refrigerant heat transfer performance in a plate-fin heat exchanger during a single-stage cryogenic cycle
    Applied Thermal Engineering, 2016
    Co-Authors: Le Cao, Fayong Zhang, Rixin Li, Shizhe Huang, Jinping Liu, Xiongwen Xu
    Abstract:

    Plate-fin heat exchangers (PFHEs) are mostly employed in small- and medium-sized LNG plants. However, studies on the heat transfer performance of Mixed Refrigerant in a PFHE under low-quality have rarely been conducted. In this paper, an experimental setup that utilized a single-stage cryogenic cycle with commercial compressors and a customized PFHE was established to study the heat transfer performance of the PFHE throughout the cool-down process. The components of the Mixed Refrigerant included nitrogen, methane, ethylene, propane and isobutane. Several experiments were conducted to obtain a refrigeration temperature as low as -160 °C. The characteristics of the cool-down process and the temperature difference change in the RHE were discussed. Meanwhile, five sets of condensation correlations and 13 sets of flow boiling correlations were selected to predict the HTC in the PFHE. The experimental overall HTC of the PFHE based on the hot sides was approximately between 11.88 and 37.74 W m-2 K-1. However, most of the existing correlations were not able to correctly predict the HTC of the PFHE in this work. Meanwhile, some suggestions regarding the PFHE design in a Mixed Refrigerant cryogenic system were proposed.

  • thermal performance of brazed plate heat exchangers for a Mixed Refrigerant joule thomson cooler
    International Journal of Refrigeration-revue Internationale Du Froid, 2016
    Co-Authors: Weiqiang Pang, Jinping Liu
    Abstract:

    Abstract The objective of the present work is to contribute to the development of a brazed plate heat exchanger as the recuperative heat exchanger for a Mixed Refrigerant Joule–Thomson cooler. In this study, the thermal performance of the recuperative heat exchanger is experimentally investigated. For the recuperative heat exchanger, the overall heat transfer coefficient varies from 38.3 to 362.5 W m −2  K −1 and the exergy efficiency is in the range of 54.2–85.7%. Moreover, four condensation correlations and ten evaporation correlations were utilized to assess the mixture's two-phase overall heat transfer coefficient, with the modification of the mixture's mass transfer resistance. The experimental data are well-predicted by two correlation combinations with mean absolute errors of 17.1% and 15.8%, respectively. Hence, these two correlation combinations are recommended for use. Finally, the thermal resistances of the mixture's two-phase transfer process are evaluated by the correlation combination, that best predicts the experimental data.

  • Mixed Refrigerant composition shift due to throttle valves opening in auto cascade refrigeration system
    Chinese Journal of Chemical Engineering, 2015
    Co-Authors: Jinping Liu, Le Cao
    Abstract:

    Abstract Auto cascade refrigeration (ACR) cycle with phase separators is widely used in the cryogenic system. The composition of Mixed Refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of Refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.

Il Moo - One of the best experts on this subject based on the ideXlab platform.

  • economic optimization of dual Mixed Refrigerant liquefied natural gas plant considering natural gas extraction rate
    Industrial & Engineering Chemistry Research, 2017
    Co-Authors: Inkyu Lee, Il Moo
    Abstract:

    This study mainly focuses on the profit optimization of the natural gas liquefaction process considering extraction rate. The target process is the dual Mixed Refrigerant (DMR) process with 1 million tons per annum (MTPA) capacity. The liquefaction ratio and the amount of boil-off gas (BOG) varies according to the natural gas extraction rate to meet the liquefaction capacity. Therefore, utilizing produced BOG and minimizing wasted BOG is key from an economic point of view. This study performed profit optimization with various extraction rates. Moreover, the energy and cost optimizations are performed to analyze the extraction rate effect. As results for the profit maximization, the total compression energy requirement and the plant cost show optimum values between the energy and cost optimization results. The profit increases by 22.5% with 93.2% liquefaction ratio through the optimization. The result shows that producing BOG as the amount of the fuel requirement for the compression energy supply is the op...

  • Economic Optimization of Dual Mixed Refrigerant Liquefied Natural Gas Plant Considering Natural Gas Extraction Rate
    2017
    Co-Authors: Inkyu Lee, Il Moo
    Abstract:

    This study mainly focuses on the profit optimization of the natural gas liquefaction process considering extraction rate. The target process is the dual Mixed Refrigerant (DMR) process with 1 million tons per annum (MTPA) capacity. The liquefaction ratio and the amount of boil-off gas (BOG) varies according to the natural gas extraction rate to meet the liquefaction capacity. Therefore, utilizing produced BOG and minimizing wasted BOG is key from an economic point of view. This study performed profit optimization with various extraction rates. Moreover, the energy and cost optimizations are performed to analyze the extraction rate effect. As results for the profit maximization, the total compression energy requirement and the plant cost show optimum values between the energy and cost optimization results. The profit increases by 22.5% with 93.2% liquefaction ratio through the optimization. The result shows that producing BOG as the amount of the fuel requirement for the compression energy supply is the optimal extraction rate. Resultingly, the optimal design of the profit max DMR process is also found through the profit optimization

  • Strategies for Process and Size Selection of Natural Gas Liquefaction Processes: Specific Profit Portfolio Approach by Economic Based Optimization
    2017
    Co-Authors: Inkyu Lee, Il Moo
    Abstract:

    This study focuses on the strategies for process and size selection of various natural gas liquefaction processes by economic based optimization. As various types of liquefaction processes can be differentiated by their energy efficiency and equipment requirements, the energy requirement and cost of a liquefaction process have to be considered simultaneously to find the optimal process for a given plant size. Herein, we developed two mathematical models, i.e., the thermodynamic model and cost model, based on the unit equipment that were integrated into a profit optimization model that could be applied to various natural gas liquefaction processes and plant sizes. In this study, the profit optimization model was applied to three representative natural gas liquefaction processes: single Mixed Refrigerant (SMR), dual Mixed Refrigerant (DMR), and propane precooled Mixed Refrigerant (C3MR) processes. The capacity of the plants ranged from 1 to 7 million tons per annum (MTPA). As a result of profit optimization, specific profit portfolios were obtained and the economical plant size ranges were figured out: 1–2.2 MTPA for the SMR process, 2.2–4 MTPA for the DMR process, and 4–7 MTPA for the C3MR process

  • total cost optimization of a single Mixed Refrigerant process based on equipment cost and life expectancy
    Industrial & Engineering Chemistry Research, 2016
    Co-Authors: Inkyu Lee, Il Moo
    Abstract:

    This study mainly focuses on minimizing the total cost of the single Mixed Refrigerant (SMR) process based on the equipment cost equations considering equipment life expectancy. Moreover, the energy and cost analyses are performed by comparing optimization results with two different objectives. The objective functions to be minimized include the total compression energy and the total annual cost, which is the sum of the annual capital cost and annual operating cost. By the compression energy minimization, the operating cost is significantly reduced by 16.2% because the largest part of this cost is taken by electricity for the compression energy requirement. In addition, a 14.0% capital cost saving is realized by the energy minimization. The results of total cost minimization show a 16.0% operating cost reduction from the base case, which is a little lower compared to energy minimization, but the capital cost saving is dramatically higher at 28.3%. Through the cost analyses, it is found that the compressor...

  • Total Cost Optimization of a Single Mixed Refrigerant Process Based on Equipment Cost and Life Expectancy
    2016
    Co-Authors: Inkyu Lee, Il Moo
    Abstract:

    This study mainly focuses on minimizing the total cost of the single Mixed Refrigerant (SMR) process based on the equipment cost equations considering equipment life expectancy. Moreover, the energy and cost analyses are performed by comparing optimization results with two different objectives. The objective functions to be minimized include the total compression energy and the total annual cost, which is the sum of the annual capital cost and annual operating cost. By the compression energy minimization, the operating cost is significantly reduced by 16.2% because the largest part of this cost is taken by electricity for the compression energy requirement. In addition, a 14.0% capital cost saving is realized by the energy minimization. The results of total cost minimization show a 16.0% operating cost reduction from the base case, which is a little lower compared to energy minimization, but the capital cost saving is dramatically higher at 28.3%. Through the cost analyses, it is found that the compressors greatly affect not only the operating cost but also the capital cost. Two major variables that determine the energy requirement and cost of compressor are the compression ratio and flow rate. The compression ratio affects the operating cost more than the flow rate but for the capital cost, it is the other way around. Therefore, finding the optimal design for the compressor is the key consideration in minimizing the cost. This study found the optimal design and operating conditions to obtain the minimum total cost. As a result of cost minimization, the total cost can be reduced by 19.2% with a 15.61 total compression ratio and 520.7 t/h Refrigerant flow rate

Hao Guo - One of the best experts on this subject based on the ideXlab platform.

  • thermodynamic analysis of a petroleum volatile organic compounds vocs condensation recovery system combined with Mixed Refrigerant refrigeration
    International Journal of Refrigeration-revue Internationale Du Froid, 2020
    Co-Authors: Haocheng Wang, Hao Guo, Yanxing Zhao, Xueqiang Dong, Maoqiong Gong
    Abstract:

    Abstract Thermodynamic analysis of a volatile organic compounds (VOCs) condensation recovery system combined with Mixed-Refrigerant J-T (MRJT) refrigeration is illustrated in this paper, which provides an effective and economical choice for petroleum plants. VOCs is compressed, cooled by its recuperation process and separated in two simple rectification columns with 3–5 stages. The cooling powers for condensers at column top are provided by a high efficiency dual MRJT refrigerator at 100 K and 232 K, respectively. The cooling and separation characteristics of petroleum VOCs are also analyzed comprehensively. It is indicated that most of VOCs condensation load locates in high temperature region (≥ 235 K approximately). It might be feasible to cool VOCs from 235 K to 110 K by cold purified air through recuperation. For a typical petroleum VOCs, non-methane hydrocarbon residual of 56 mg Nm−3 is achieved with specific power consumption (SPC) of 0.1289 kWh Nm−3, free of additional purifying units. According to the analysis on the effects of variable VOCs composition and pressure, the cooing loads of top condensers are close related to the performance of VOCs recuperation. C1 and C2 are key components to enhance recuperation at low temperatures and reduce SPC. Exceed C3 could enlarge cold stage condenser load and SPC due degraded cold stage recuperation; while exceed C4-C6 could reduce condenser loads and SPC. Higher VOCs pressure could also decrease SPC.

  • thermodynamic comparison of small liquid nitrogen generators driven by Mixed Refrigerant j t refrigerators and gas expansion cycles
    IOP Conference Series: Materials Science and Engineering, 2020
    Co-Authors: Haocheng Wang, Hao Guo, Gaofei Che, Qinglu Song, Maoqiong Gong
    Abstract:

    The thermodynamic comparison of small Mixed-Refrigerant J-T (MRJT) and gas expansion (Kapitza cycle) LN2 generators are conducted by the exergy method in this paper. Both of two types are employed for low pressure N2 liquefaction and air separation (< 9.0 bar). Pure N2, PSA units or cryogenic air separation columns are used for LN2 production. The MRJT type is driven by single-stage compressors. It is indicated that the efficiency of MRJT type is higher than Kapitza type. With pure N2 at 8.0 bar, the figures of merit (FOM) of MRJT and Kapitza types are 26.86% and 12.79%, respectively. With mini air separation columns, the FOM of MRJT and Kapitza types are 21.42% and 11.34%, respectively. The large exergy losses in the compressor unit and non-isentropic expansion are the main reasons of the inferior efficiency of the Kapitza type. In addition, the Kapitza type requires larger total compressor displacement than the MRJT type. The MRJT type is recommended to be used in small LN2 generators.

  • development and performance test of a miniature movable Mixed Refrigerant liquid nitrogen generator
    Cryogenics, 2018
    Co-Authors: Haocheng Wang, Hao Guo, Gaofei Che, Y X Zhao, Maoqiong Gong
    Abstract:

    Abstract In order to cover long-term but small quantity liquid nitrogen requirements of laboratory or field users, a miniature movable Mixed-Refrigerant liquid nitrogen generator (MRLN) was developed and tested here, based on a precooled Mixed-Refrigerant J-T (MRJT) refrigerator. With the full air-cooled, skid-mounted structure, this MRLN was built utilizing off-the-shelf refrigeration components like commercial single-stage oil-lubricated compressors to reduce construction cost greatly. Bottled pure N2, pressure swing adsorption (PSA) unit and mini cryogenic rectification column could be employed to supply N2 in different operation modes respectively. In pure N2 mode, N2 was directly liquefied by the MRJT refrigerator. With feed N2 at 0.8 MPa, the specific power consumption (SPC) was 1.79 kWh L−1, and figure of merit (FOM) was 6.27%. The estimated SPC in PSA mode was 2.68 kWh L−1. For column mode, the SPC was 4.59 kWh L−1, with FOM of 3.38%. A closed N2 cycle could convey cooling capacity between flammable Refrigerant and air. This MRLN could be a convenient and low-costing choice for some liquid nitrogen users.

  • thermodynamic design and analysis of movable small scale Mixed Refrigerant liquid nitrogen generators
    International Journal of Refrigeration-revue Internationale Du Froid, 2018
    Co-Authors: Haocheng Wang, Hao Guo, Gaofei Che, Y X Zhao, Xuezhi Dong, Maoqiong Gong, O Gao
    Abstract:

    Abstract Thermodynamic design and analysis of small scale liquid nitrogen generators based on Mixed-Refrigerant Joule–Thomson cycle (MR JT) are illustrated in this paper, providing low-cost choices for remote and field users. Bottled pure nitrogen, PSA unit or mini air separation column are utilized in different processes, with feed gases liquefied in the MR JT refrigerators driven by single-stage compressors. Problems in the application of low pressure gas source and mini column are investigated, including column simplification, air liquefaction in flammable MR JT, etc. System exergy analysis is conducted. For pure N2 at 8.0 bar, specific power consumption (SPC) of 0.53 kWh L−1 and figure of merit (FOM) of 24.46% are achieved. With PSA unit, SPC is 0.85 kWh L−1. In the process with column, a closed N2 cycle is employed to deliver cooling capacity from flammable Mixed-Refrigerant to air. Optimal SPC of 0.84 kWh L−1 and FOM of 19.96% are reached.

  • performance comparison of single stage Mixed Refrigerant joule thomson cycle and pure gas reverse brayton cycle at fixed temperatures from 80 to 180 k
    International Journal of Refrigeration-revue Internationale Du Froid, 2017
    Co-Authors: Haocheng Wang, Hao Guo, Gaofei Che, Y X Zhao, Xuezhi Dong, Maoqiong Gong
    Abstract:

    Abstract Performance comparison of single-stage Mixed-Refrigerant Joule–Thomson refrigeration cycle (MJTR) and pure-gas reverse Brayton cycle (RBC) at fixed-temperatures from 80 to 180 K was made in this paper. The simulation was mainly conducted under nonideal conditions with extrinsic irreversibilities. Exergy efficiency and volumetric cooling capacity are two main evaluation parameters. Exergy loss distributions along the cycles were analyzed. Under ideal conditions, RBC achieved the highest exergy efficiency at all temperatures, but lower volumetric cooling capacity than MJTR at middle-high temperatures. Under nonideal conditions, both the exergy efficiency and volumetric cooling capacity of MJTR were obviously superior to RBC from 100 to 180 K, but inferior to RBC at 80 K. Two reasons account for the sharp performance degradation of MJTR: The high fraction of neon resulted in large entropy generation and exergy loss in throttling process. Larger recuperator duty and WLMTD lead to larger losses in the recuperator.