海水淡化多级离心高压泵振动原因分析

目前,国内在海水淡化系统中对多级卧式离心泵的振动分析研究较少,很多都无法检测其真正超标原因。文中通过对某电厂海水淡化系统反渗透多级高压泵振动问题,对运行试验数据分析以及对泵的拆解过程进行了详细的描述,并深入剖析原因,最终找出了影响振动超标的主要因素。此次振动超标分析,具有较强的借鉴和指导意义,可以避免不必要的经济损失。     

Comparable Characterization of Nanocellulose Extracted from Bleached Softwood and Hardwood Pulps

In this study, the characteristics of nanocellulose extracted from bleached softwood and hardwood pulps by formic acid hydrolysis followed by TEMPO-mediated oxidation were compared using transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared analysis (FT-IR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The experimental results showed that the nanocellulose products derived from spruce pulp exhibited a relatively larger particle size, higher crystallinity, and higher thermal stability, compared with the corresponding products obtained from aspen pulp under the same conditions. Furthermore, the study helped establish that the properties of the nanocellulose products were highly dependent on the nature of the starting materials under identical processing conditions.     

Exploring a novel ceramic (Ti,W)3SiC2 for interconnect of intermediate temperature solid oxide fuel cell

A solid solution (Ti,W)₃SiC₂ possessing good oxidation resistance and low area-specific resistance (ASR) after oxidation has been synthesized by an in-situ hot pressing process. The oxidation rate constant at 800 °C in air is 6.29 × 10^?14 g² cm^?4 s^?1 for (Ti,W)₃SiC₂. The formed single-layer oxide is composed of W doped rutile TiO₂ and amorphous SiO₂. SiO₂ is evenly inlaid in the communicative body frame of TiO₂. W doped in TiO₂ mainly exists as W⁶⁺. W doping not only hinders the outward diffusion of Ti by decreasing the concentration of native Ti interstitials in TiO₂, but also restrains the inward diffusion of oxygen by decreasing the concentration of O vacancies. Furthermore, W dopant in TiO₂ enhances the electrical conductivity of TiO₂ by increasing the concentration of semi-free electron. Therefore, the low ASR of (Ti,W)₃SiC₂ after oxidation owes to high electrical conductivity of TiO₂ as well as the reduced thickness of oxide scale. All the results render (Ti_1-xW_x)₃SiC₂ promising as interconnects for the intermediate temperature solid oxide fuel cell.     

High-quality freestanding flexible poly(5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1H-indole) film: Electrosyntheses,characterization, and optical properties

The electron-donating substituted indole is generally difficult to be polymerized into high-quality film. The electrochemical polymerization of the electron-donating 3,4-ethylenedioxythiophene (EDOT)-monosubstituted indole may be a challenge. Herein, we designed and synthesized a novel fluorescent comonomer based on the combination of indole and EDOT groups, namely, 5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1H-indole (EDTI), and subsequently electrodeposited into flawless freestanding flexible poly(5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1H-indole) (PEDTI) film with a resistance of 60 MΩ/cm in CH₂Cl₂ containing 0.1 M Bu₄NBF₄. Electrochemical results showed that the oxidation onset potential of EDTI was at 0.8 V vs Ag/AgCl, which was lower than those of indole (0.96 V vs Ag/AgCl) and EDOT (1.35 V vs Ag/AgCl). FTIR spectra indicated that the polymerization of EDTI occurred at the 5-position on thiophene ring and 2,3-positions on indole ring, forming the crosslinking polymer film. The colors of as-prepared PEDTI could switch reversibly from purple to brown under applied potentials of 1.3 and −1.3 V, which were distinctly different from those of polyindole, poly(3,4-ethylenedioxythiophene) (PEDOT), and poly(EDOT-bis-substituted indole) (PETI). Fluorescence spectral studies revealed that the comonomer and corresponding polymer were good blue-green light emitters. These results implied that PEDTI had potential applications for photoelectric devices such as electrochromic devices, light-emitting diodes, and fluorescence sensors. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47016.     

Improving room-temperature electrochemical performance of solid-state lithium battery by using electrospun La2Zr2O7 fibers-filled composite solid electrolyte

Low ionic conductivity at room temperature and poor interfacial compatibility are the main obstacles to restrain the practical application of polymer solid electrolytes. In this work, lanthanum zirconate (LZO) fibers were prepared by electrospinning method and used for the first time as fillers in sandwich polypropylene carbonate (PPC)-based solid electrolyte. Meanwhile, a graphite coating was applied on one surface of the composite solid electrolyte (CSE) membrane. The results show that the LZO fibers significantly increases the room-temperature electrochemical performance of the CSE, and the graphite coating enhances the interfacial compatibility between electrolyte and lithium anode. Furthermore, an ultra-thin PPC-LZO CSE with a total thickness of 22 μm was prepared and used in NCM622/CSE/Li solid-state cell, which shows an initial discharge capacity of 165.6 mAh/g at the current density of 0.5C and a remaining capacity of 113.0 mAh/g after 250 cycles at room temperature. Rise to 1C, the cell shows an initial discharge capacity of 154.2 mAh/g with a remaining capacity of 95.6 mAh/g after 250 cycles. This ultra-thin CSE is expected to be widely applied in high energy-density solid-state battery with excellent room-temperature electrochemical performances.     

Recovery of hydrogen from hydrogen sulfide by indirect electrolysis process

Recovery hydrogen from hydrogen sulfide is an effective way of utilizing exhaust gas. In this paper, removal of hydrogen sulfide by indirect electrochemical process was studied using acidic aqueous solution of Fe³⁺/Fe²⁺ as the electrochemical intermediate. Solid polymer electrolyte was applied to hydrogen production by indirect electrolysis of H₂S, in which the anode was graphite cloth, the cathode was the platinized graphite cloth, and the membrane was proton exchange membrane. The results of electrolysis experiments showed the relationship of current density as a function of electrolytic voltage at constant flow rate of electrolyte, temperature, and electrolyte composition. The effect of the cathode liquid velocity on current density was small. When the flow rate of anode electrolyte was greater than 200 L/hr., the current density tended to be stable. When [Fe³⁺]>0.20 mol/L, the concentrations of Fe²⁺ and Fe³⁺ ions in the anode solution had no significant impact on the current density. The current density gradually increased with temperature. In the electrolytic process of hydrogen production, the Fe²⁺ ions diffused from the anode to the cathode. The amount of diffusing Fe²⁺ ions gradually increased with time. The effect of Fe²⁺ ions diffusion from anode to cathode on hydrogen production was discussed.     

Design and synthesis of side-chain optimized poly(2,6-dimethyl-1,4-phenylene oxide)-g-poly(styrene sulfonic acid) as proton exchange membrane for fuel cell applications: Balancing the water-resistance and the sulfonation degree

Side-chain optimized poly (2,6-dimethyl-1,4-phenylene oxide)-g-poly (styrene sulfonic acid) (PPO-g-PSSA) is designed with balanced water-resistance and sulfonation degree. The PPO-g-PSSA is synthesized by controlled atom-transfer radical polymerization (ATRP) from brominated poly (2,6-dimethyl-1,4-phenylene oxide) (PPO-xBr) and ethyl styrene-4-sulfonate and followed by hydrolysis. A series of PPO-g-PSSA are prepared possessing different bromination degree (x) of PPO-xBr and polymerization degree (m) of the side-chains and the water-resistances of the fabricated membranes are investigated. The results show that a PPO-g-PSSA at relatively low x (x < 0.2) and high m (m > 4) exhibits good balance between the water-resistance and the sulfonation degree. Namely, it displays suitable proton conductivity with compromised water-resistance. Moreover, a maximum ion exchange capacity (IEC) of 3.24 mmol g^?1 is reached without the sacrifice of water-resistance. In addition, PPO-g-0.08PSSA-13 and PPO-g-0.14PSSA-4 are chosen characterized by thermogravimetric analysis, proton conductivities and mechanical properties. At 90% RH, the optimized PPO-g-0.08PPSA-13 possesses a proton conductivity of 37.9 mS cm^?1 at 40 °C and 45.5 mS cm^?1 at 95 °C, respectively.     

Improved biogas yield from organic fraction of municipal solid waste as preliminary step for fuel cell technology and hydrogen generation

Biogas utilization in fuel cell technology and hydrogen generation is a modern and economically viable approach. A pretreatment step prior to anaerobic digestion (AD) is obligatory to increase the hydrolysis, solubilize the complex matter present in organic fraction of municipal solid waste (OFMSW) and to achieve higher yield of biogas. This study was intended to find out the effects of thermal, chemical and thermochemical pretreatments on the properties and structure of OFMSW and also on biogas production. There was an increase in chemical oxygen demand of 6.87, 1.61 and 11.60% for thermal, chemical and thermochemical pretreatments, respectively. Also, the content of volatile solids was reduced by 2.36% by thermochemical pretreatment. FTIR, XRD and SEM analysis revealed that these pretreatments also caused chemical and morphological changes on the substrate, as a result reduced its crystallinity and enhanced the rate of hydrolysis. A significant increase of 54% in biogas yield was achieved after thermochemical pretreatment in comparison to untreated OFMSW sample.     

烤烟自然醇化和人工醇化过程中感官质量的变化

为明确烟叶最佳醇化方式和醇化时间，从而提高烟叶品质、节省醇化成本，以山东诸城复烤后的中部烤烟烟叶为试验材料，对人工醇化和自然醇化过程中烟叶感官评吸指标进行了评价分析。结果表明，两种醇化方式下诸城复烤烟样品的最佳醇化时间均为18个月左右；与自然醇化相比，人工醇化方式对烟叶品质提升效果更好。根据原料库存情况和品质需求采用合适的醇化方式和醇化时间，有利于卷烟企业提高烟叶质量、节约企业成本。