Molecular dynamic investigation on sulfur migration during hydrogen production by benzothiophene gasification in supercritical water

Benzothiophene (BT) is a key sulfur-containing intermediate product in the thermal conversion process of coal and heavy oil. The migration process of the sulfur element may affect the thermal utilization design of BT. In this paper, BT was used as a model compound to simulate the supercritical water gasification (SCWG) process by molecular dynamics with a reactive force field (ReaxFF) method, and the laws of hydrogen production and sulfur migration mechanisms were obtained. Increasing the molecule number of supercritical water (SCW) and increasing the reaction temperature can enhance the generation of hydrogen and promote the conversion of organic sulfur to inorganic sulfur. Water was the main source of H₂, and H₂S was the main gaseous sulfur-containing product. SCW had a certain degree of oxidation due to a large number of hydroxyl radicals, which could increase the valence of sulfur. The conversion process of BT in SCW was mainly divided into four stages, including thiophene ring-opening; sulfur separation or carbon chain broke with sulfur retention; carbon chain cleaved, and gas generation. The lumped kinetic parameters of the conversion of sulfur in BT to inorganic sulfur were calculated, and the activation energy was 369.98 kJ/mol, which was much lower than those under pyrolysis conditions. This article aims to clarify the synergistic characteristics of hydrogen production and sulfur migration in the SCWG process of BT from the molecular perspective, which is expected to provide a theoretical basis for pollutant directional removal during hydrogen production by sulfur-containing organic matters in SCW.     

Charging strategy through analysis of charging influence factors of ultra-light hydrogen storage with polyethylene terephthalate liner

A lightweight type 4 vessel with a polyethylene terephthalate (PET) liner is analyzed. The derived heat transfer coefficients between the gas and wall are applied, and a parametric study is performed. An optimized charging strategy is also developed. Firstly, when the injected hydrogen temperature decreases, the charging time increases, and the charged gas temperature decreases. Secondly, the higher the ambient temperature, the shorter the charging time, and the higher the charged gas temperature. Thirdly, the larger the mass flow rate, the shorter the charging time, and the higher charged gas temperature. Fourthly, as the initial pressure inside the vessel increases, the charging time shortens, and the charged gas temperature decreases. Fifthly, using the formulated charging strategy, during summer, the charged gas temperature decreases by approximately 9 °C. In winter, the charging time is reduced by approximately 58 s. The results provide important information of temperature control for ensuring vessel safety.     

High-performance Ag nanowires/PEDOT:PSS composite electrodes for PVDF-HFP piezoelectric nanogenerators

Journal of Materials Science: Materials in Electronics - The highly transparent and conductive poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS)/Ag nanowires (NWs) composite...     

Elastic gels based on flaxseed gum with konjac glucomannan and agar

Food Science and Biotechnology - In this study, we prepared hydrocolloid gels in which flaxseed gum (FSG), konjac glucomannan (KGM), and agar (AG) were blended in different ratios for use as a...     

Fabrication of an electrolyte-supported protonic ceramic fuel cell with nano-sized powders of Ni-composite anode

Composite anodes of nano-sized Ni and Ba(Zr_0.85Y_0.15)O_3-δ (BZY) were fabricated by infiltrating a single precursor solution of BZY and Ni into the BZY scaffold, and decreasing the calcination temperature to 1173 K. This decrease in the fabrication temperature of the Ni-cermet anode prevents the chemical reaction between the electrolyte and nickel, thus preventing a reduction in the conductivity of the electrolyte. By optimizing the amount of Ni in the Ni-cermet and infiltrating additional catalysts such as CeO₂ and Pd, the non-ohmic ASR of the Ni-cermet anode could be optimized. This resulted in a smaller non-ohmic ASR of anode than one that was fabricated by the conventional co-sintering method. Consequently, a high power density of 790 mW/cm² at 973 K can be obtained from electrolyte-supported cells.     

Efficient fault diagnosis method of PEMFC thermal management system for various current densities

The temperature of a fuel cell has a considerable impact on the saturation of a membrane, electrochemical reaction speed, and durability. So thermal management is considered one of the critical issues in polymer electrolyte membrane fuel cells. Therefore, the reliability of the thermal management system is also crucial for the performance and durability of a fuel cell system. In this work, a methodology for component-level fault diagnosis of polymer electrolyte membrane fuel cell thermal management system for various current densities is proposed. Specifically, this study suggests fault diagnosis using limited data, based on an experimental approach. Normal and five component-level fault states are diagnosed with a support vector machine model using temperature, pressure, and fan control signal data. The effects of training data at different operating current densities on fault diagnosis are analyzed. The effects of data preprocessing method are investigated, and the cause of misdiagnosis is analyzed. On this basis, diagnosis results show that the proposed methodology can realize efficient component-level fault diagnosis using limited data. The diagnosis accuracy is over 92% when the residual basis scaling method is used, and data at the highest operating current density is used to train the support vector machine.     

动态循环荷载下大坝混凝土拉压转换损伤本构模型构建及影响研究

目前混凝土坝抗震安全评价中,对于动态循环荷载下大坝混凝土损伤本构模型中从受拉状态向受压状态转变过程(拉压转换)中的混凝土弹性模量变化,一般都基于商用软件ABAQUS的"单边效应"假设,认为混凝土弹性模量立即恢复为初始弹性模量。上述假设的合理性缺乏试验验证,直接影响混凝土坝抗震安全评价的可靠性。通过对全级配大坝混凝土拉压转换全过程试验成果的观察分析,发现混凝土从受拉状态进入受压状态后弹性模量并非立即恢复为初始弹性模量,而是由损伤后弹性模量连续渐进恢复至初始弹性模量,期间原有的受拉残余应变在压应力作用下迅速减小到较小数值,因此ABAQUS的"单边效应"假设并不符合实际情况。本文以全级配大坝混凝土拉压转换全过程试验成果为基础,提出受拉损伤发生后,拉压转换时受压应力应变关系采用双折线模型的思路,据此推导了相应的应力-应变关系解析表达式,构建了更接近混凝土拉压转换时真实状况的本构关系数值模型。通过实际工程的计算分析,发现常用的受压弹性模量立即恢复为初始弹性模量的损伤本构模型过高估计了坝体刚度,可能带来偏于不安全的评价结果。     

Strain-rate-dependent constitutive and damage models for a low-yielding-strength steel under dynamic loadings

Journal of Mechanical Science and Technology - The low-yielding-strength (LYS) steel is promising for energy-absorbing devices due to its outstanding plasticity. Although the mechanical properties...