Expulsive force in the development of CO 2 sequestration: application of SC-CO 2 jet in oil and gas extractionWang, Haizhu;Li, Gensheng;Shen, Zhonghou;He, Zhenguo;Liu, Qingling;Zhu, Bin;Wang, Youwen;Wang, Meng
2019 "Frontiers in Energy"
doi: 10.1007/s11708-017-0458-6
Abstract With the rapid development of global economy, an increasing amount of attention has been paid to the emission of greenhouse gases, especially CO2. In recent years, dominated by the governments around the world, several significant projects of CO2 sequestration have been conducted. However, due to the huge investment and poor economic effects, the sustainability of those projects is not satisfactory. Supercritical CO2 (SC-CO2) has prominent advantages in well drilling, fracturing, displacement, storage, plug and scale removal within tubing and casing, which could bring considerable economic benefits along with CO2 sequestration. In this paper, based on physicochemical properties of SC-CO2 fluid, a detailed analysis of technical advantages of SC-CO2 applied in oil and gas development is illustrated. Furthermore, the implementation processes of SC-CO2 are also proposed. For the first time, a recycling process is presented in which oil and gas are extracted and the CO2 generated could be restored underground, thus an integrated technology system is formed. Considering the recent interests in the development of enhancing hydrocarbon recoveries and CO2 sequestration, this approach provides a promising technique that can achieve these two goals simultaneously.
Cathodes with MnO 2 catalysts for metal fuel batteryWei, Songbo;Liu, He;Wei, Ran;Chen, Lin
2019 "Frontiers in Energy"
doi: 10.1007/s11708-019-0611-5
Abstract A series of cathodes with MnO2 catalysts of metal fuel battery were prepared. The catalyst slurry was treated by ultrasonic dispersion under the ultrasonic time of 20 min, 40 min and 60 min. The cathodes were also dried with the temperature of 90°C, 120°C and 150°C. Besides, the microstructures of the cathodes and discharging performance were investigated. The results indicated that the ultrasonic time and drying temperature had a remarkable influence on the electric current densities, but had little effect on the open-circuit voltage. The effects of oxygen on the current density and voltage of cathode were also studied, and it was found that the method of blowing oxygen to cathode could increase the current density of the metal fuel battery.
Constant temperature control of tundish induction heating power supply for metallurgical manufacturingYue, Yufei;Xu, Qianming;Guo, Peng;Luo, An
2019 "Frontiers in Energy"
doi: 10.1007/s11708-018-0572-0
Abstract The tundish induction heating power supply (TIHPS) is one of the most important equipment in the continuous casting process for metallurgical manufacturing. Specially, the constant temperature control is greatly significant for metallurgical manufacturing. In terms of the relationship between TIH load temperature and output power of TIHPS, the constant temperature control can be realized by power control. In this paper, a TIHPS structure with three-phase PWM rectifiers and full-bridge cascaded inverter is proposed. Besides, an input harmonic current blocking strategy and a load voltage feedforward control are also proposed to realize constant temperature control. To meet the requirement of the system, controller parameters are designed properly. Experiments are conducted to validate the feasibility and effectiveness of the proposed TIHPS topology and the control methods.
Metal-based direct hydrogen generation as unconventional high density energyXu, Shuo;Liu, Jing
2019 "Frontiers in Energy"
doi: 10.1007/s11708-018-0603-x
Abstract Metals are unconventional hydrogen production materials which are of high energy densities. This paper comprehensively reviewed and digested the latest researches of the metal-based direct hydrogen generation and the unconventional energy utilization ways thus enabled. According to the metal activities, the reaction conditions of metals were generalized into three categories. The first ones refer to those which would violently react with water at ambient temperature. The second ones start to react with water after certain pretreatments. The third ones can only react with steam under somewhat harsh conditions. To interpret the metal-water reaction mechanisms at the molecular scale, the molecule dynamics simulation and computational quantum chemistry were introduced as representative theoretical analytical tools. Besides, the state-of-the-art of the metal-water reaction was presented with several ordinary metals as illustration examples, including the material treatment technologies and the evaluations of hydrogen evolution performances. Moreover, the energy capacities of various metals were summarized, and the application potentials of the metal-based direct hydrogen production approach were explored. Furthermore, the challenges lying behind this unconventional hydrogen generation method and energy strategy were raised, which outlined promising directions worth of further endeavors. Overall, active metals like Na and K are appropriate for rapid hydrogen production occasions. Of these metals discussed, Al, Mg and their alloys offer the most promising hydrogen generation route for clean and efficient propulsion and real-time power source. In the long run, there exists plenty of space for developing future energy technology along this direction.
Performance analysis of cogeneration systems based on micro gas turbine (MGT), organic Rankine cycle and ejector refrigeration cycleBo, Zemin;Zhang, Kai;Sun, Peijie;Lv, Xiaojing;Weng, Yiwu
2019 "Frontiers in Energy"
doi: 10.1007/s11708-018-0606-7
Abstract In this paper, the operation performance of three novel kinds of cogeneration systems under design and off-design condition was investigated. The systems are MGT (micro gas turbine) + ORC (organic Rankine cycle) for electricity demand, MGT + ERC (ejector refrigeration cycle) for electricity and cooling demand, and MGT + ORC + ERC for electricity and cooling demand. The effect of 5 different working fluids on cogeneration systems was studied. The results show that under the design condition, when using R600 in the bottoming cycle, the MGT + ORC system has the lowest total output of 117.1 kW with a thermal efficiency of 0.334, and the MGT + ERC system has the largest total output of 142.6 kW with a thermal efficiency of 0.408. For the MGT + ORC + ERC system, the total output is between the other two systems, which is 129.3 kW with a thermal efficiency of 0.370. For the effect of different working fluids, R123 is the most suitable working fluid for MGT + ORC with the maximum electricity output power and R600 is the most suitable working fluid for MGT + ERC with the maximum cooling capacity, while both R600 and R123 can make MGT + ORC + ERC achieve a good comprehensive performance of refrigeration and electricity. The thermal efficiency of three cogeneration systems can be effectively improved under off-design condition because the bottoming cycle can compensate for the power decrease of MGT. The results obtained in this paper can provide a reference for the design and operation of the cogeneration system for distributed energy systems (DES).
Simulation analysis of municipal solid waste pyrolysis and gasification based on Aspen plusDeng, Na;Li, Dongyan;Zhang, Qiang;Zhang, Awen;Cai, Rongchang;Zhang, Biting
2019 "Frontiers in Energy"
doi: 10.1007/s11708-017-0481-7
Abstract To predict and analyze the municipal solid waste (MSW) pyrolysis and gasification process in an updraft fixed bed more veritably and appropriately, numerical modeling based on Gibbs energy minimization was executed using the Aspen plus software. The RYield module was combined with the RGibbs module to describe the pyrolysis section, while the RGibbs module was used for the gasification section individually. The proposed model was used to forecast and analyze the target performance parameters including syngas composition, lower heating value (LHV) and carbon conversion rate under different conditions of the gasification temperatures, and ratios and types of gasifying agents. The results indicate that there is a good agreement between the experimental data and the simulated data obtained using this model. The predicted optimum gasification temperature is approximately 750°C, and the best ratio of water vapor as gasifying agent is around 0.4. The mixture of flue gas and water vapor has an economical and recycled prospect among four commonly used gasifying agents.
Application of AI techniques in monitoring and operation of power systemsGao, David Wenzhong;Wang, Qiang;Zhang, Fang;Yang, Xiaojing;Huang, Zhigang;Ma, Shiqian;Li, Qiao;Gong, Xiaoyan;Wang, Fei-Yue
2019 "Frontiers in Energy"
doi: 10.1007/s11708-018-0589-4
Abstract In recent years, the artificial intelligence (AI) technology is becoming more and more popular in many areas due to its amazing performance. However, the application of AI techniques in power systems is still in its infancy. Therefore, in this paper, the application potentials of AI technologies in power systems will be discussed by mainly focusing on the power system operation and monitoring. For the power system operation, the problems, the demands, and the possible applications of AI techniques in control, optimization, and decision making problems are discussed. Subsequently, the fault detection and stability analysis problems in power system monitoring are studied. At the end of the paper, a case study to use the neural network (NN) for power flow analysis is provided as a simple example to demonstrate the viability of AI techniques in solving power system problems.
Reactive power deployment and cost benefit analysis in DNO operated distribution electricity markets with D-STATCOMGupta, Atma Ram;Kumar, Ashwani
2019 "Frontiers in Energy"
doi: 10.1007/s11708-017-0456-8
Abstract The aim of this paper is to analyze unbalanced radial distribution systems (UBRDS) with the distribution static compensator (D-STATCOM). The main objectives of this paper are D-STATCOM allocation in UBRDS with an objective of providing reactive power support to enhance voltage profile and reduce line losses of the distribution network, determination of optimal D-STATCOM rating subjected to minimization of total cost, and impact of D-STATCOM placement on improving power factor and savings in cost of energy loss. The analysis is conducted on a large industrial load model with light, medium and high loading scenarios. Further, the impact of load growth is also considered for better planning of the power distribution system. The results are obtained on standard 25-bus UBRDS to check the feasibility of the proposed methodology.
A novel flow-resistor network model for characterizing enhanced geothermal system heat reservoirGuo, Jian;Cao, Wenjiong;Wang, Yiwei;Jiang, Fangming
2019 "Frontiers in Energy"
doi: 10.1007/s11708-018-0555-1
Abstract The fracture characteristics of a heat reservoir are of critical importance to enhanced geothermal systems, which can be investigated by theoretical modeling. This paper presents the development of a novel flow-resistor network model to describe the hydraulic processes in heat reservoirs. The fractures in the reservoir are simplified by using flow resistors and the typically complicated fracture network of the heat reservoir is converted into a flow-resistor network with a reasonably simple pattern. For heat reservoirs with various fracture configurations, the corresponding flow-resistor networks are identical in terms of framework though the networks may have different section numbers and the flow resistors may have different values. In this paper, numerous cases of different section numbers and resistor values are calculated and the results indicate that the total number of flow resistances between the injection and production wells is primarily determined by the number of fractures in the reservoir. It is also observed that a linear dependence of the total flow resistance on the number of fractures and the relation is obtained by the best fit of the calculation results. Besides, it performs a case study dealing with the Soultz enhanced geothermal system (EGS). In addition, the fracture numbers underneath specific well systems are derived. The results provide insight on the tortuosity of the flow path between different wells.
Design of packing cup interference fit value of hypercompressors for low density polyethylene productionLei, Da;Li, Xuehong;Li, Yun;Ren, Xiwen
2019 "Frontiers in Energy"
doi: 10.1007/s11708-017-0450-1
Abstract The hypercompressor is one of the core facilities in low density polyethylene production, with a discharge pressure of approximately 300 MPa. A packing cup is the basic unit of cylinder packing, assembled by the interference fit between an inner cup and an outer cup. Because the shrink-fitting prestresses the packing cup, serious design is needed to gain a favorable stress state, for example, a tri-axial compressive stress state. The traditional method of designing the interference fit value for packing cups depends on the shrink-fit theory for thick-walled cylinder subject to internal and external pressure. According to the traditional method, critical points are at the inner radii of the inner and external cup. In this study, the finite element method (FEM) has been implemented to determine a more accurate stress level of packing cups. Different critical points have been found at the edge of lapped sealing surfaces between two adjacent packing cups. The maximum Von Mises equivalent stress in a packing cup increases after a decline with the rise of the interference fit value. The maximum equivalent stress initially occurs at the bore of the inner cup, then at the edge of lapped mating surfaces, and finally at the bore of the outer cup, as the interference radius increases. The traditional method neglects the influence of axial preloading on the interference mating pressure. As a result, it predicts a lower equivalent stress at the bore of the external cup. A higher interference fit value accepted by the traditional method may not be feasible as it might already make packing cups yield at the edge of mating surfaces or the bore of the external cup. Along with fatigue analysis, the feasible range of interference fit value has been modified by utilizing FEM. The modified range tends to be narrower and safer than the one derived from the traditional method, after getting rid of shrink-fit values that could result in yielding in a real packing cup.