小型混合制冷剂天然气液化流程设计与分析

分析了IFP-Axens公司开发的混合制冷剂循环Liquefin工艺关键技术,在此基础上设计了一种全新的小型混合制冷剂液化流程。比较了三个流程的主要流程参数,综合分析了换热器冷热负荷曲线和温差曲线。结果表明,压缩机和换热器的损失是循环的主要损失,可以通过选用效率更高的压缩机,或者改变压缩系统结构减少损;提高返流轻组分节流后压力可有效降低换热温差,通过进一步优化制冷剂组成和运行压力,可使换热温差更加均匀,减少换热器损,提高流程的经济性。     

Comprehensive comparison of small-scale natural gas liquefaction processes using brazed plate heat exchangers

The brazed plate heat exchanger (BPHE) has some advantages over the plate-fin heat exchanger (PFHE) when used in natural gas liquefaction processes, such as the convenient installation and transportation, as well as the high tolerance of carbon dioxide (CO₂) impurities. However, the BPHEs with only two channels cannot be applied directly in the conventional liquefaction processes which are designed for multi-stream heat exchangers. Therefore, the liquefaction processes using BPHEs are different from the conventional PFHE processes. In this paper, four different liquefaction processes using BPHEs are optimized and comprehensively compared under respective optimal conditions. The processes are compared with respect to energy consumption, economic performance, and robustness. The genetic algorithm (GA) is applied as the optimization method and the total revenue requirement (TRR) method is adopted in the economic analysis. The results show that the modified single mixed refrigerant (MSMR) process with part of the refrigerant flowing back to the compressor at low temperatures has the lowest specific energy consumption but the worst robustness of the four processes. The MSMR with fully utilization of cold capacity of the refrigerant shows a satisfying robustness and the best economic performance. The research in this paper is helpful for the application of BPHEs in natural gas liquefaction processes.     

Exergy analysis of multistage cascade refrigeration cycle used for natural gas liquefaction

This paper provides an exergy analysis of the multistage cascade refrigeration cycle used for natural gas liquefaction. The equations of exergy destruction and exergetic efficiency for the main cycle components such as evaporators, condensers, compressors, and expansion valves are developed. The relations for the total exergy destruction in the cycle and the cycle exergetic efficiency are obtained. Also, an expression for the minimum work requirement for the liquefaction of natural gas is developed. It is shown that the minimum work depends only on the properties of the incoming and outgoing natural gas, and it increases with decreasing liquefaction temperature. The minimum work for a typical natural gas inlet and exit state is determined to be 456.8 kJ kg^?1 of liquefied natural gas (LNG), which corresponds to a coefficient of performance (COP) of 1.8. Using a typical actual work input value; the exergetic efficiency of the multistage cascade refrigeration cycle is determined to be 38.5% indicating a great potential for improvements. Copyright © 2002 John Wiley & Sons, Ltd.     

Energy and exergy analyses of five conventional liquefied natural gas processes

In this paper, five conventional LNG processes were investigated by energy and exergy analysis methods. On the basis of the energy analysis, three‐stage process of Linde AG and Stat oil (mixed fluid cascade [MFC]) has less energy consumption than the other ones (0.254 kWh/kg liquefied natural gas). Also, coefficient of performance of the cycles of this process is higher compared with the other ones. Exergy analysis results showed that the maximum exergy efficiency is related to the MFC process (51.82%). However, performance of the MFC process in terms of quality and quantity of energy consumption is considerable. But using three cycles in this process needs more components and consequently more fixed costs. In this study, sensitivity of coefficient of performance, specific energy consumption, and indexes of exergy analysis were also analyzed versus important operating variables for all cases. Copyright © 2014 John Wiley & Sons, Ltd.     

Study on a novel process for CO2 compression and liquefaction integrated with the refrigeration process

In order to transport and store the captured CO₂ from coal‐fired power plants, it is necessary to compress and liquefy CO₂ first. However, the power consumption of conventional process is enormous. In this paper, a novel process for CO₂ compression and liquefaction based on the analysis of the power consumption of traditional method is proposed. The new process integrates the refrigeration process driven by the lower level heat from the coal‐fired power plant. This paper analyzes and compares the energy consumptions of conventional process and new process for CO₂ compression and liquefaction. The research result indicates that, when CO₂ needs to be compressed and liquefied and an abundant low quality heat is available, the new process has obvious superiority in lowering the energy consumption. The new process for CO₂ compression and liquation integrated with the exhaust heat powered refrigeration can greatly reduce the work consumption of CO₂ compression and liquefaction. The refrigeration temperature has great effects both on the coefficient of performance of refrigeration process and work consumption of compressors. The refrigeration temperature can be selected by optimization. Using refrigerator with double stages of evaporation can further reduce the amount of the extracted steam and lower the total energy consumption for CO₂ compression and liquation. Recovering the cool energy of CO₂ is beneficial to the reduction of the total work consumption. The achievements obtained from this paper will provide a useful reference for CO₂ compression and liquefaction with the lower energy consumption. Copyright © 2012 John Wiley & Sons, Ltd.     

钢铁企业余热吸收制冷

调查和分析了钢铁企业余热利用的现状,得出余热制冷是钢铁企业余热利用的重要途径之一．以鞍钢为例介绍了吸收式制冷机组在钢铁企业的主要用途,具体分析了不同余热载体（蒸汽、热水、烟气）作为吸收制冷机组的驱动热源的应用情况,并介绍了国内外吸收式制冷最新研究情况,最后探讨了余热制冷在钢铁企业中经济性应用方案。     

Extending existing combined heat and power plants for synthetic natural gas production

In this work, integration of a synthetic natural gas (SNG) production process with an existing biomass CHP steam power cycle is investigated. The paper assesses two different biomass feedstock drying technologies—steam drying and low‐temperature air drying—for the SNG process. Using pinch technology, different levels of thermal integration between the steam power cycle and the SNG process are evaluated. The base case cold gas efficiency for the SNG process is 69.4% based on the lower heating value of wet fuel. The isolated SNG‐related electricity production is increased by a factor of 2.5 for the steam dryer alternative, and tenfold for the low‐temperature air dryer when increasing the thermal integration. The cold gas efficiency is not affected by the changes. Based on an analysis of changes to turbine steam flow, the integration of SNG production with an existing steam power cycle is deemed technically feasible. Copyright © 2011 John Wiley & Sons, Ltd.     

Energy optimization for liquefaction process of natural gas in peak shaving plant

One of the most important sections in the gas peak shaving plant regarding the energy consumption is the liquefaction process of natural gas (NG). Thus, selection and development of this process with the lowest energy consumption, offer huge potential energy and cost benefits. Here, a single-stage mixed refrigerant (SMR) cryogenic cycle with two compression stages has been selected for producing Liquefied Natural Gas (LNG). Energy consumption of the process as an objective function is optimized by describing key variables of the design. The proposed process’s calculations of thermodynamic concepts and properties are applied in MATLAB software to generate the objective function; furthermore Genetic Algorithm (GA) is used as an optimization method. Concerning works done in this area, more key parameters – related directly to the objective function – are introduced in this paper. A low irreversibility is due to enhanced values of key parameters in the LNG heat exchanger observed under a low temperature difference between hot and cold composite curves. Finally, the exergy lost of equipments in the proposed process are evaluated and analyzed in details.     

Energetic and exergetic performance evaluation of a combined heat and power system with the micro gas turbine (MGTCHP)

This study deals with the energetic and exergetic performance assessment of a combined heat and power system with micro gas turbine (MGTCHP). Quantitative energy and exergy balance for each component and the whole MGTCHP system was considered, while energy and exergy consumption within the system were determined. The performance characteristics of this MGTCHP system were evaluated using energy and exergy analyses methods. The energetic and exergetic efficiencies of the MGTCHP system are calculated as 75.99% with 254.55 kW (as 99.15 kW—electrical and 155.40 kW—hot water_{@363.15 K}) and 35.80% with 123.61 kW (as 99.15 kW—electrical and 24.46 kW—hot water_{@363.15 K}), respectively. The maximum energy loss and exergy consumption occur at 44.03 kW in the stack gas and 129.61 kW in the combustion chamber, respectively. Copyright © 2007 John Wiley & Sons, Ltd.     

天然气压力能透平回收分析与联合循环研究

从热力学第二定律角度分析透平膨胀过程中降的构成,对管输天然气做功能力进行理论分析,得出了温度、压力、化学的计算方法和透平膨胀输出轴功极限能力的评价因子。在理论分析的基础上,进一步给出了现有的基于冷电联产的联合循环方式,从机电一体化角度提出了该领域基于总能系统理论的多学科的研究思路。     

利用油田污水余热热泵供暖系统的热力经济分析

介绍了油田余热资源的现状和充分回收采油污水余热的吸收式热泵供暖系统。并与燃油锅炉和燃气锅炉供暖系统对比 ,对吸收式热泵供暖系统进行技术经济分析     

Conceptual design and optimization of a novel hydrogen liquefaction process based on helium expansion cycle integrating with mixed refrigerant pre-cooling

Due to the safety of operation and the development of high-efficiency helium refrigerators, the development of helium refrigeration cycles in hydrogen liquefaction is continuously promoted. To reduce the energy consumption and exergy loss of this energy-intensive process, a novel hydrogen liquefaction process integrating with mixed refrigerant (MR) pre-cooling is simulated by Aspen HYSYS and optimized by genetic algorithm (GA) to improve performance under the premise of safe production and multi-faceted analyzed based on the helium expansion refrigeration cycle. A new MR with reasonable composition and ratio is used in the pre-cooling cycle to improve the matching of heat transfer curves. Energy, exergy and economic analyses are applied to evaluate the liquefaction process, and horizontal comparison is also used to evaluate the rationality and superiority of the process design. The output of 5 t/d of liquid hydrogen (21.7 K, 1.5 bar) can be achieved and the overall specific energy consumption (SEC), exergy efficiency (EXE) and coefficient of performance (COP) are 9.703 kWh/kg _LH2, 39.1%, and 0.1333, respectively. Compared with similar processes, the proposed process shows better performance and potential development prospects.     

Power generation and cooling capacity enhancement of natural gas processing facilities in harsh environmental conditions through waste heat utilization

Most natural gas (NG) producers in the Persian Gulf face increasing challenges in meeting their domestic gas demands and therefore seek to reduce their NG consumption. Concurrently, the on‐site power generation and cooling capacities of local NG processing facilities are constrained by extreme climatic conditions. A combined cooling and power scheme based on gas turbine (GT) waste heat‐powered absorption refrigeration is techno‐economically assessed to reduce the NG consumption of a major gas processing plant in the Persian Gulf. The scheme utilizes double‐effect water‐lithium bromide absorption refrigeration activated by steam generated from GT exhaust gas waste heat to provide both GT compressor inlet air and process gas cooling. Based on a thermodynamic analysis, recovery of 150 MW of GT waste heat is found to enhance the plant cooling capacity by 195 MW, thereby permitting elimination of a 32.6 MW GT and existing cooling equipment. On‐site power generation is enhanced by 196 GWh annually through GT compressor inlet air cooling, with energy efficiency (i.e., 64%) improved by 35% using cogeneration relative to the existing power generation plant. The overall net annual operating expenditure savings contributed by the combined cooling and power system are of $US13 million to 34 million based on present and projected local utility prices, with an economic payback period estimated at 2 to 5 years. These savings translate to approximately 94 to 241 MMSCM of NG per year, highlighting the potential of absorption refrigeration to both enhance the power generation and cooling capacity of hydrocarbon processing plants exposed to harsh environmental conditions and to realize substantial primary energy savings. Copyright © 2014 John Wiley & Sons, Ltd.     

Energy,exergy, and economical analyses of a photovoltaic thermal system integrated with the natural zeolites for heat management

In this study, the first time in the literature, natural zeolite has been employed for photovoltaic thermal (PVT) and experimentally tested as a thermal energy storage material. The main aim of the paper is to introduce natural zeolite as a heat storage material for PVT systems. The PVT systems integrated with phase change materials and natural zeolite were designed, the components of the system were explained, the thermodynamical modelling including the first and second laws was presented, the system performances were evaluated, performance parameters were investigated, energy and exergy efficiencies were determined, and economical analyses of each system were performed. Besides, all results were compared with a conventional PVT system. The average overall energy efficiency values for PVT experiments were 33% for paraffin, 37% for stearic acid, 40% for zeolite, and 32% for conventional PVT systems. The payback period of the PVT system with paraffin, zeolite, stearic acid, and conventional PVT was calculated as 10, 8, 9, and 9 years, respectively. The results show that the natural zeolite is a material with significant potential to be used for heat management in PVT for any meteorological condition.     

Life‐cycle‐integrated thermoeconomic and enviroeconomic assessments of the small‐scale‐liquefied natural gas cold utilization systems

Small‐scale‐liquefied natural gas (LNG) cold‐utilized power generation systems are the sustainable solutions in the rural and inland areas where the large‐scale power generation is infeasible. This study investigates three different small‐scale LNG cold‐utilized power generation systems, which are called as the single, combined, and carbon dioxide (CO₂)–reduced combined systems according to their design details. The assessments are done according to the life‐cycle‐based enviroeconomic and life‐cycle‐integrated thermoeconomic assessment (LCiTA) models that are recently developed and new approaches, in order to better monitor their feasibilities in real operations. The life‐cycle‐based enviroeconomic assessment shows that the combined system has the lowest environmental payback period with 7.35 years that is nearly 6 months and 1 year lower than the single and CO₂‐reduced combined systems, respectively. The LCiTA study deduces that the combined system has the minimum levelized product cost while the single system has the highest values. The integration of CO₂ capture components increases the levelized product cost nearly by 16.0% in the combined design, but the levelized product cost value is still found lower than the single system. Moreover, the sustainability performance of the systems is evaluated according to the improved sustainability index calculated by the life‐cycle‐integrated fuel and destruction costs. The index value of the combined system is twice that of the single system. The multiobjective optimization study is performed in cases of closed operation rooms. The best trade‐off points are found in the close ambient air temperature range between 300.50 and 302.00 K. To observe the dynamic outdoor performance, the finite sum approach is applied for the LCiTA model. The highest fluctuations are seen for the CO₂‐reduced combined system while the smallest fluctuations belong to the combined system.     

The regional economic impact of oil and gas extraction in Texas

This paper empirically investigates the regional economic impact of oil and gas extraction in Texas during the recent shale oil boom. Regressions with county-level data over the period 2009–2014 support smaller multiplier effects on local employment and income than corresponding estimates drawn from popular input–output-based studies. Economic impacts were larger for extraction from gas wells than oil wells, while the drilling phase generated comparable impacts. Estimates of economic impacts are greater in a dynamic spatial panel model that allows for spillover effects across local economies as well as over time.     

Thermo‐economic investigation: an insight tool to analyze NGCC with calcium‐looping process and with chemical‐looping combustion for CO2 capture

In this work, three kinds of natural gas‐based power generation processes for CO₂ capture and storage, that is, natural gas‐combined cycle with pre‐combustion decarburization (NGCC‐PRE), NGCC‐PRE with calcium‐looping process, and NGCC‐PRE with chemical‐looping combustion (NGCC‐CLC), are analyzed by Aspen Plus. The effects of two decisive variables (i.e., steam‐to‐natural gas (S/NG) ratio and oxygen‐to‐natural gas (O/NG) ratio) on the thermodynamic performances of individual process, such as energy and exergy efficiencies, are investigated systematically. Based on simulation outcomes, all the three processes are favored by operating at S/NG = 2.0 and O/NG = 0.65. Furthermore, comparisons of individual system efficiencies and exergy destruction contributor are herein involved. The results show that the highest system efficiencies and lowest exergy destruction are achieved in the NGCC‐CLC process. In addition, capital investment, dynamic payback period, net present value, and internal rate of return are used for deciding the economic feasibility and surely are involved in this work for comparison purpose. Copyright © 2016 John Wiley & Sons, Ltd.     

The influences of hydrogen on the performance and emission characteristics of a heavy duty natural gas engine

Because blending hydrogen with natural gas can allow the mixture to burn leaner, reducing the emission of nitrogen oxide (NO_x), hydrogen blended with natural gas (HCNG) is a viable alternative to pure fossil fuels because of the effective reduction in total pollutant emissions and the increased engine efficiency.In this research, the performance and emission characteristics of an 11-L heavy duty lean burn engine using HCNG were examined, and an optimization strategy for the control of excess air ratio and of spark advance timing was assessed, in consideration of combustion stability. The thermal efficiency increased with the hydrogen addition, allowing stable combustion under leaner operating conditions. The efficiency of NO_x reduction is closely related to the excess air ratio of the mixture and to the spark advance timing. With the optimization of excess air ratio and spark advance timing, HCNG can effectively reduce NO_x as much as 80%.     

Geothermal energy extraction using abandoned oil and gas wells: Techno-economic and policy review

Retrofitting depleted oil wells to extract geothermal energy is considered as one of the promising proposals to extend the overall economic life of oil and gas well. For successful implementation of this initiative, a comprehensive overview covering all aspects of geothermal energy extraction from abandoned oil well should be taken into account including technical, economic considerations as well as regulations and policies of respective local governments. Unfortunately, most reported studies have been focused only on one or two aspects, primarily on technical and economic aspects. Little or no study has focused on the policy sector. Moreover, these findings have been scattered, creating difficulties to extract essential information and dragging further development of the technology. This paper is therefore prepared with the objective to provide a comprehensive overview on the geothermal energy extraction from abandoned oil well, technical challenges in its implementation, economical consideration on the conversion of the well and government policy on energy especially geothermal energy and regulation on the utilization of abandoned oil well. To achieve this objective, extensive literature reviews are conducted with more attention given to recent studies on the field. Challenges on the development of this technology are discussed from technical, economic, and policy perspectives. Based on the identified challenges, required research and development as well as necessary policies for further advancement of this technology are outlined and discussed. By providing this comprehensive information, this review paper may serve as a good foundation and guidelines on the conversion of abandoned oil wells into geothermal energy wells.