Hydrogen as a new energy plays a vital role in the future energy development.Hydrogen production from electrolyzed water includes two reactions of hydrogen evolution and oxygen evolution, which has the advantages of low price, no pollution, abundant reserves, and the oxygen evolution reaction is a rapid step in hydrogen production from electrolyzed water. A simple co⁃precipitation method was proposed to recombine carbon materials onto Co9S8 catalytic materials, and the oxygen evolution properties were characterized. Compared with Co9S8 without composite carbon material, a small amount of carbon material could significantly improve the oxygen production performance of Co9S8.The structure, morphology and electrochemical properties of the materials were tested by X⁃ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), polarization curves, chronoamperometry and AC impedance. The results show that the prepared Co9S8/C material has no impurity phase. When the current intensity is 10 mA/cm2, the overpotential is 350 mV, and the Tafel slope is 102 mV/dec, it has high electrocatalytic oxygen production performance.
The oxidation⁃extraction process was used to desulfurize of the visbreaking diesel oil, O3 was used as oxidant, formic acid was used as catalyst, and polar oxides such as sulfoxide and sulfone were extracted and separated from diesel oil by polar organic solvent. The effects of oxidation time, oxidation temperature, ratio of extractant to oil and amount of formic acid on the desulfurization rate of diesel oil in the reaction system were investigated, and the optimum reaction conditions were determined. The results showed that the sulfur content of visbreaking diesel oil decreased from 4 980 μg/g to 490 μg/g and the desulfurization rate was 90%. By comparing the properties of visbreaking diesel oil before and after oxidation, it can be concluded that the oxidation⁃extraction method can also improve the chromaticity and acidity of visbreaking diesel oil.
In the process of foam flooding in heavy oil fields, the performance of single foaming agent is unstable. In view of this difficult problem, a new foaming agent system for foam flooding is designed in this paper. The foam synthesis index and temperature and salt resistance are taken as the evaluation indexes by Waring⁃Blender agitation method four kinds of foaming agents such as betaine, CTAB, SDBS and SDS were selected. The best foaming agents were betaine and CTAB. Through the experimental selection of different proportion of foaming single agent, the oil washing ability test and sand filling tube simulation experiment of CTAB and betaine system with 2∶1 ratio were carried out. The results show that the foaming agent system have good temperature and salt resistance and strong oil washing ability. In the sand⁃filled pipe simulation experiment, the two displacement modes of steam flooding plus foam flooding and steam foam alternating injection flooding are compared. The results show that the oil recovery can reach 60.7% by alternately injecting steam and foam fluid into the reservoir, which has certain reference value.
In order to explore the effect of different types of anionic⁃nonionic surfactants on the emulsification effect of heavy oil and obtain a reliable structure⁃activity relationship. In this paper, six monomeric anionic⁃nonionic surfactants C14E3C, C14E5C, C14E7C, C14E9C, C16E3C, C18E3C and two Gemini anionic⁃ nonionic surfactants OP4, OP15 were selected for a heavy oil block in Shengli Oilfield. By using a spinning drop interfacial tensiometer, stability analyzer, we investigated the effects of surfactant mass fraction, oil⁃water mass ratio, and polymer addition on oil⁃water interfacial tension, particle size and stability of crude oil emulsion. The results show that: the type of monomer has little effect on the stability of the emulsion with the increase of the oxyethylene (EO) group, and the growth of the alkyl chain can increase the stability of the emulsion to a small extent. For Gemini⁃type anionic⁃nonionic surfactants, the increase of the number of oxyethylene (EO) groups can increase the stability of the emulsion slightly. The monomer type has a smaller molecular size than the Gemini type, and the interfacial tension steady state value is generally low. At the same time, the addition of the polymer can increase the stability of the emulsion.
The heat transfer effect of nanofluid in electric heater was studied. Fe3O4⁃water nanofluid was prepared by two⁃step method. The effect of Fe3O4⁃water nanofluid with various nanoparticle concentrations (mass fraction of 0.1%~2.0%) on heating efficiency of the electric heater with or without magnetic field was studied. Mechanism of enhanced heat transfer by Fe3O4⁃water nanofluids under a magnetic field was also discussed. Results show that the Fe3O4⁃water nanofluid with a mass fraction of 1.0% obtains 18.2% enhancement of heat transfer on environment temperature compares to without a magnetic field. The Fe3O4⁃water nanofluid with a mass fraction of 1.0% obtains 35.1% enhancement of heat transfer on environment temperature with an external magnetic field. This research provides an important reference for enhancements of natural convective heat transfer in nanofluid applications.
Photoelectrocatalytic technology can provide an energy conservation and environmental protection way for environmental governance and chemical production. High efficient photoanodes materials are one of the challenges in the practical application of photoelectrocatalytic technique, therefore, high performance photoanode materials have been designed and developed for enhancing the application efficiency of photoelectrocatalytic technique. Fe2O3 has become a hot spot in the field of photocatalysis because of its narrow band gap, high stability and low price. In order to develop the high performance Fe2O3 photoanodes materials, many studies focused on the energy band position, conductivity and photogenerated the hole diffusion length. This review summarized the preparation techniques (hydrothermal method, spray pyrolysis, chemical vapor deposition, atomic layer deposition, etc), modification methods (“junction” construction, doping, morphological control, ect) and modified hydrogen production of the Fe2O3 photoanodes materials, the challenges and opportunities in this promising research area were proposed.
In solvent⁃free condition, a new 1D chain holmium phosphite Ho(H2PO3)4(C6N2H16)0.5 (compound 1) decorated by phosphite groups has been synthesized using N,N'⁃Dimethylpiperazine (Me2ppz) as structure directing agent, and further been characterized by powder XRD, infrared spectroscopy, thermogravimetric, inductively coupled plasma and CHN elemental analyses. Single crystal X⁃ray diffraction analysis reveals that compound 1 crystallizes in the monoclinic crystal system with the P21/c space group. The structure of compound 1 is constructed by HoO6 octahedra and [H2PO3]- pseudo⁃pyramids units via vertex oxygen atoms. It is worth noting that compound 1 is the first rare earth phosphite compound which is synthesized in solvent⁃free condition. Moreover, a pair of left⁃ and righ⁃handed helical chains are present in the structure. In addition, coordination mode and geometry of lanthanide phosphonate, phosphate and phosphite are listed in this paper.
With the developments of deep sea and marginal oil fields, FPSO has been widely used in offshore oil and gas field development.FPSO, as an oil and gas production device with both energy production and consumption, takes an economic energy distribution scheme on the premise of meeting its energy demand, which not only helps to reduce construction costs, but also helps to improve the energy efficiency of the entire system and promote energy conservation. Taking the annual total cost of energy system as the objective function, the MILP model of FPSO distributed energy system is established and solved under the conditions of energy balance and technical constraints to determine the equipment selection and capacity, and the corresponding operation plan to achieve the purpose of energy conservation and consumption reduction. The model is validated by an example of FPSO in the Bohai sea. The results show that the cost of distributed energy system can be reduced by 14.6% compared to traditional operating schemes. In addition, considering the impact of different energy prices on the economy of the system, it is found that the increase in natural gas prices has a great impact on the design and operation of DES.
Methane hydrate can be used as a carrier to store and transport natural gas. However, they generate slowly under natural conditions,so it is necessary to improve the rate of methane hydrate formation.To this end, the effect of the amphoteric surfactant LAD⁃40 on the methane hydrate formation rate in various mass fractions (10~500 μg/g) was examined. The results show that when the pressure is constant, compared with the nucleation temperature of methane hydrate formation under pure water conditions, adding any mass fractions of LAD⁃40, the nucleation temperature of methane hydrate changes little, which fails to improve the thermodynamic conditions of methane hydrate formation; because of the existence of LAD⁃40, the gas⁃liquid contact area was increased, the nucleation time was shortened, and the hydrate form in the reactor phase. As the LAD⁃40 mass fraction increases, the methane hydrate formation rate increases linearly, and the gas consumption does not change much, however, compared with methane hydrate formation under pure water conditions, it is significantly improved.
In order to explore the influence of deep sea T⁃tube flow difference and pipe diameter abrupt change on the flow characteristic parameters of the vertical pipe, a certain oil and gas field in the South China Sea was taken as the research object, and the numerical simulation method was used. The results show that the influence of flow rate difference is related to the sum of the total flow rate instead of the each flow; the effect of changing diameters of riser pipe on relevant parameters can be divided into three stages: DC=0.03 m, DC=0.06~0.12 m and DC=0.24 m. And when the vertical riser has a sudden change, the flow parameters are mainly related to its minimal pipe diameter.
Taking geothermal heat as the heat source, KCS⁃11, KCS⁃34 and KSG⁃1 as the bottom cycles respectively, the thermodynamic and thermoeconomic performance of three systems combining flash⁃Kalina cycle and absorption refrigeration cycle (F⁃KCS11⁃ARC, F⁃KCS34⁃ARC, F⁃KSG1⁃ARC) were compared and analyzed. The results show that the total exergy loss of the F⁃KCS11⁃ARC system is 5.3% and 2.7% lower than that of the F⁃KCS34⁃ARC system and the F⁃KSG1⁃ARC system,respectively,and the component with the largest exergy loss is the heat exchanger 1. The F⁃KCS34⁃ARC system has the highest thermal efficiency, but the F⁃KCS11⁃ARC system has the highest heat recovery efficiency when the geothermal source temperature is in the range of 155～220 °C, and the smaller geothermal source temperature and flash pressure can make the system obtain higher heat recovery efficiency.Thermal economic analysis shows that pump 1 is the most expensive component in all three systems, the next is steam turbine 2. The F⁃KCS11⁃ARC system has the lowest cost, the highest annual net income, and the smallest investment recovery period, with values of 2.09×106 $, 6.61×105 $ and 3.72 years, respectively.
As a new type of high⁃efficiency mixing equipment, static mixers are widely used in industrial production due to their good mixing effect and simple operation. In this paper, the SK type static mixer was introduced into the crude oil storage tank to solve the problem of uneven distribution of crude oil density. The three⁃dimensional incompressible flow field was numerically simulated by FLUENT. The Eulerian multiphase flow model was used to simulate the velocity field, concentration field, temperature field and pressure field of the fluid in the static mixer. The results show that: under the action of the spiral blades of the static mixer, the crude oil moves cyclically along the opposite direction of the blade and changes periodically. Through the cutting, shearing and rotating action of the crude oil, the oil is almost completely mixed at the exit,which shows that SK static mixer has better mixing effect and less pressure loss and can reduce the energy consumption cost.
The problems of deformation failure of vertical storage tank under wind load were studied. The floating roof tank was established by using the Workbench software. The eigenvalues were used for buckling analysis and the buckling deformation diagrams of the tank were plotted. The modal maps of different orders were read by software to analyze the locations and causes of deformation of the tank. And by changing the wind speeds, the changes of the stress on the windward and leeward sides of the tank were studied. The results show that the displacement of the shell is mainly radial displacement. As the height increases, the stress caused by wind load is mainly changed from axial stress to circumferential stress. The equivalent stress is generally rising at the circumferential angle of 0°. The equivalent stress of the tank wall at the circumferential angle of 180° decreases first and then increases. The research results can provide reference for the wind resistant design of storage tanks.
The problem of mixed H∞ and passive model reference tracking control for a class of discrete switched systems with Discrete time⁃delay based on asynchronous switching was studied. By using the piecewise Lyapunov functional theory and average dwell time method, sufficient conditions for the Discrete time⁃delay switched systems to be exponentially stable with asynchronous mixed H∞ and passive model reference tracking performance were given in the form of linear matrix inequalities. Finally, a simulation example was provided to illustrate the effectiveness of the proposed method.
In this paper, an improved RBF prediction model was proposed to solve the problems of cumbersome calculation and many influencing factors in the process of coking energy consumption. In the energy consumption prediction model, target flue temperature, flue suction, moisture, volatile matter and coking time were taken as input variables, and coking energy consumption as output variables. Because RBF network had many shortcomings such as poor learning ability and slow convergence speed, an energy consumption prediction model based on improved differential evolution algorithm was proposed. By using the differential evolution algorithm with strong global search ability, the optimal values of the center value, width and output weight of the basis function in RBF network were selected as the center value, width and output weight of RBF neural network. The results show that the improved RBF prediction has high accuracy, stability and training speed, which is of great significance for reducing coking energy consumption, increasing coke output and improving economic benefits of enterprises.
