Mathematical Model of Natural Gas Desulfurization Based on Membrane Absorption

Models of mass transfer kinetics combined with mass transfer differential equation and mass transfer resistance equation were established on the basis of double-film theory. Mass transfer process of H2 S absorption by means of polypropylene hydrophobic microporous hollow fiber membrane contactor was simulated using MDEA(N-methyldiethanolamine) as the absorption liquid and corresponding experiments of natural gas desulfurization were performed. The simulation results indicated that the removal rate of hydrogen sulfide showed positive dependence on the absorption liquid concentration and gas pressure. However, the desulfurization rate showed negative dependence on gas flow. The simulated values were in good agreement with the experimental results. The in-tube concentration of hydrogen sulfide at the same point increased with increase in the gas velocity. Axial concentration of hydrogen sulfide decreased rapidly at the beginning, and the decrease saw a slowdown during the latter half period. Hydrogen sulfide concentration dropped quickly in the radial direction, and the reduction in the radial direction was weakened with the increase of axial length due to the gradual reduction of hydrogen sulfide concentration along the tube. The desulfurization rate under given operating conditions can be predicted by this model, and the theoretical basis for membrane module design can also be provided.

Reduction of VOC emissions by a membrane-based gas absorption process

A membrane-based gas absorption （MGA） process was evaluated for the removal of volatile organic compounds （VOCs） based on C6H6/N2 mixture. The absorption of C6H6 from a C6H6/N2 mixture was investigated using a hydrophobic polypropylene hollow fiber membrane contactor and the aqueous solution of N-formyl morpholine （NFM） as absorbent. The effects of various factors on the overall mass transfer coefficient was investigated. The experimental results showed that the removal efficiency of C6H6 could reach 99.5% in present studied system. A mathematical model based on resistance-in-series concept was presented to predict the value of overall mass transfer coefficient. The average error between the predicted and experimental values is 7.9%. In addition, conventional packed columns for VOCs removal was also evaluated for comparison.

Bio-reduction of nitrate from groundwater using a hydrogen-based membrane biofilm reactor

A hydrogen-based membrane biofilm reactor （MBfR） using H2 as electron donor was investigated to remove nitrate from groundwater. When nitrate was first introduced to the MBfR, denitrification took place on the shell side of the membranes immediately, and the effluent concentration of nitrate continuously decreased with 100% removal rate on day 45 under the influent nitrate concentration of 5 mg NO3^--N/L, which described the acclimating and enriching process of autohydrogenotrophic denitrification bacteria. A series of short-term experiments were applied to investigate the effects of hydrogen pressures and nitrate loadings on deniWification. The results showed that nitrate reduction rate improved as H2 pressure increasing, and over 97% of total nitrogen removal rate was achieved when the nitrate loading increased from 0.17 to 0.34 g NO3^--N/（m^2.day） without nitrite accumulation. The maximum deniwification rate was 384 g N/（m^3.day）. Partial sulfate reduction, which occurred in parallel to nitrate reduction, was inhibited by denitrififcation due to the competition for H2. This research showed that MBfR is effective for removing nitrate from the contaminated groundwater.

Easy removing of phenol from wastewater using vegetable oil-based organic solvent in emulsion liquid membrane process

Phenol is considered as pollutant due to its toxicity and carcinogenic effect.Thus,variety of innovative methods for separation and recovery of phenolic compounds is developed in order to remove the unwanted phenol from wastewater and obtain valuable phenolic compound.One of potential method is extraction using green based liquid organic solvent.Therefore,the feasibility of using palm oil was investigated.In this research,palm oil based organic phase was used as diluents to treat a simulated wastewater containing 300×10^(-6) of phenol solution using emulsion liquid membrane process(ELM).The stability of water-in-oil(W/O) emulsion on diluent composition and the parameters affecting the phenol removal efficiency and stability of the emulsion;such as emulsification speed,emulsification time,agitation speed,surfactant concentration,pH of external phase,contact time,stripping agent concentration and treat ratio were carried out.The results of ELM study showed that at ratio7 to 3 of palm oil to kerosene,5 min and 1300 r·min^(-1) of emulsification process the stabile primary emulsion were formed.Also,no carrier is needed to facilitate the phenol extraction.In experimental conditions of500 r·min^(-1) of agitation speed,3%Span 80,pH 8 of external phase,5 min of contact time,0.1 mol·L^(-1) NaOH as stripping agent and 1:10 of treat ratio,the ELM process was very promising for removing the phenol from the wastewater.The extraction performance at about 83%of phenol was removed for simulated wastewater and an enrichment of phenol in recovery phase as phenolate compound was around 11 times.

INFLUENCE OF ALCOHOL-BASED NONSOLVENTS ON THE FORMATION AND MORPHOLOGY OF PVDF MEMBRANES IN PHASE INVERSION PROCESS

Through the preparation of PVDF membranes using various nonsolvent coagulation baths following the phase inversion process, the influence of alcohol-based nonsolvents on the formation and structure of PVDF membranes were investigated. The light scattering and light transmission measurements were used to characterize the equilibrium phase diagram and the gelation speed, respectively. The locations of the crystallization-induced gelation boundaries for various systems and precipitation processes were explained from the corresponding thermodynamic and kinetic parameters. It was found that the better affinity between alcohol-based nonsolvents and DMAc solvent caused the gelation boundaries further away from the PVDF-DMAc axis with the coagulation bath varying from water, methanol, ethanol to iso-propanol. Due to the lower exchange rate of DMAc and alcohols, the delayed demixing took place for the membrane-forming using alcohols as baths, and the delayed time became longer when the coagulation bath was changed from methanol, ethanol to iso-propanol. The characterization results of membranes indicate that the influence of nonsolvents on the phase diagram and the precipitation process are in agreement with those on the membrane morphology. The better thermodynamic stability and a low exchange diffusion rate of PVDF/DMAc/alcohols favor the liquid-solid phase separation in gelation process, and therefore yield the membranes with a porous upper surface, a particular bottom surface and symmetrical structure.

Corn Umbilicus Tissue-Based Membrane Biosensor for Pyruvate

Pyruvate, a final metabolite of glycogen, is widely distributed over many kinds of tissue fluids of human bodys. The determination for its contents is of clinical importance in gynaecology. Titrimetry, colorimetry and chromatography are common used methods. In recent years, enzymatic mthod has proved to be one of the most important determination techniques for its simplicity and fastness. However, in some cases, the use of purified enzymes as biocatalysts yields systems with a short useful lifetime owing, to enzyme instability A tiss

Studies on synthesis and property of novel acid-base proton exchange membranes

Sulfonated poly（phthalazinone）s （SPPENK, SPPESK and SPPBEK） were prepared by direct polymerization reaction from sulfonated monomers. The novel acid-base membranes were composed of sulfonated polymers as the acidic compounds, and polyetherimide （PEI） as the basic compounds, casting from their N-methylpyrrolidone （NMP） solution directly onto clean glass plates at 60 ℃ aiming at enhancing membrane toughness and other relative properties. The resulted acid-base composite membranes had excellent resistance to swelling, thermo-stability, hydrolysis resistance and oxidative resistance properties with highly ion-exchange capacity （IEC）.

Recent advances on the membrane processes for CO_2 separation

Membrane separation technology has popularized rapidly and attracts much interest in gas industry as a promising sort of newly chemical separation unit operation. In this paper, recent advances on membrane processes for CO_2 separation are reviewed. The researches indicate that the optimization of operating process designs could improve the separation performance, reduce the energy consumption and decrease the cost of membrane separation systems. With the improvement of membrane materials recently,membrane processes are beginning to be competitive enough for CO_2 separation, especially for postcombustion CO_2 capture, biogas upgrading and natural gas carbon dioxide removal, compared with the traditional separation methods. We summarize the needs and most promising research directions for membrane processes for CO_2 separation in current and future membrane applications. As the time goes by, novel membrane materials developed according to the requirement proposed by process optimization with increased selectivity and/or permeance will accelerate the industrialization of membrane process in the near future. Based on the data collected in a pilot scale test, more effort could be made on the optimization of membrane separation processes. This work would open up a new horizon for CO_2 separation/Capture on Carbon Capture Utilization and Storage(CCUS).

Studies of the Methane Steam Reforming Reaction at High Pressure in a Ceramic Membrane Reactor

The effects of temperature and pressure on the steam reforming of methane （CH4＋H2O→← 3H2＋CO） were investigated in a membrane reactor （MR） with a hydrogen permeable membrane. The studies used a novel silica-based membrane prepared by using the chemical vapor deposition （CVD） technique with a permeance for H2 of 6.0×10^-8 mol·m^-2.s^-1.Pa^-1 at 923 K. The results in a packed-bed reactor （PBR） were compared to those of the membrane reactor at various temperatures （773-923 K） and pressures （1-20 atm, 101.3-2026.5 kPa） using a commercial Ni/MgAl2O4 catalyst. The conversion of methane was improved significantly in the MR by the countercurrent removal of hydrogen at all temperatures and allowed product yields higher than the equilibrium to be obtained. Pressure had a positive effect on the hydrogen yield because of the increase in driving force for the permeance of hydrogen. The yield of hydrogen increased with pressure and reached a value of 73× 10^-6 mol·g^-1 .s^-1 at 2026.5 kPa and 923 K which was higher by 108% than the value of 35×10^-6 mol·g^-1.s^-1 obtained for the equilibrium yield. The results obtained with the silica-based membrane were similar to those obtained with various other membranes as reported in the literature.

An agent-based simulation with NetLogo platform to evaluate forward osmosis process(PRO Mode)

Forward osmosis(FO), as an emerging technology, is influenced by different factors such as operating conditions,module characteristics, and membrane properties. The general aim of this study was to develop a suitable(flexible,comprehensive, and convenient to use) computational tool which is able to simulate osmosis through an asymmetric membrane oriented in pressure retarded osmosis(PRO) mode in a wide variety of scenarios. For this purpose, an agent-based model was created in NetLogo platform, which is an easy-to-use application environment with graphical visualization abilities and well suited for modeling a complex system evolving over time. The simulation results were validated with empirical data obtained from literature and a great agreement was observed. The effect of various parameters on process performance was investigated in terms of temperature,cross-flow velocity, length of the module, pure water permeability coefficient, and structural parameter of the membrane. Results demonstrated that the increase in all parameters, except structural parameter of the membrane and the length of module led to the increase of average water flux. Moreover, nine different draw solutes were selected in order to assess the influence of net bulk osmotic pressure difference between the draw solution(DS) and feed solution(FS)(known as the driving force of FO process) on water flux. Based on the findings of this paper, the performance of FO process(PRO mode) can be efficiently evaluated using the NetL ogo platform.

A 10kW-scale Distributed Power Plant of Natural Gas-Proton Exchange Membrane Fuel Cell

A 10 kW-scale natural gas fueled proton exchange membrane fuel cell(PEMFC) distributed power plant is presented in this paper,which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system,the reformed fuel with CO molar fraction less than 10-5 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform,a rapid control prototype(RCP) is developed for real-time condition management,signal tracking and parameter tuning,data storing,and man-machine interaction. In a typical running with 4.3 kW stack power,the hydrogen production efficiency,gross power generation efficiency and heat recovery efficiency approach to 76%,41% and 50%,respectively. The peak stack power reaches 7.3 kW. Though there is still considerable dis-tance to long-term operation at 10 kW-scale net power generation,it is a milestone for the PEMFC-based stationary application in China.

Metal Salts Assisted Enzyme-Based Extraction of Stevioside from the Leaves of <i>Stevia rebaudiana</i>Bertoni

Stevioside, extracted from the leaves of Stevia rebaudiana Bertoni, is a natural, high intensity, lowcaloric sweetener with wide therapeutic activities. Conventional stevioside extraction methodologies involve the use of non-green solvents, supercritical fluids, microwaves, etc., however, all these processes are expensive, time-consuming and eco-unfriendly. Therefore an alternative process is desired for the isolation of stevioside. In this study, a novel enzyme-mediated extraction (EME) method has been developed. The dry stevia leaves were pre-treated with hydrolytic enzymes aided by transition metal salts (FeCl3). This was followed by pressurized hot water extraction (PHWE) to release stevioside. The crude extract was purified and clarified through multi-stage membrane filtration. The results confirm that metal salt-assisted cellulase pre-treatment enhanced the yield of stevioside to 72%, with 98% purity, which was higher in comparison to existing methods. Thus, the methodology developed establishes a simple, “green”, enzyme-mediated process for the efficient isolation of stevioside under economical and eco-friendly conditions.

Optimized Conditions for the Delivery of Small Membrane Impermeable Compounds into Human Cells Using Hypotonic Shift

Cell-based assays represent a major end point of high throughput screening (HTS) but a key limitation of such assays is the potentially poor membrane permeability of test compounds. In this study, we optimized the conditions for the delivery of the membrane impermeable compound 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) into human cells using hypotonic shift;a method that can promote the uptake of molecules from the extracellular fluid into cell cytoplasm via endocytosis. We showed that uptake of HPTS by cells was a function of hypotonic buffer osmolarity and that delivery was highly efficient with almost 100% of cells displaying uptake. Delivery of HPTS was equally effective at 25°C and 37°C, with delivery of compound proportional to incubation time and concentration of HPTS within the loading medium. The experimental conditions identified in this study could be applied to HTS drug discovery studies providing an effective method of delivering small membrane impermeable compounds into cells.

缓控释肥硅基膜材的制备与表征

以钙镁磷肥、硅丙树脂为主要原料,加入甲基硅酸钠作粘结剂,制备了缓控释肥硅基膜材,并采用撒粉离心包衣、底喷式流化床工艺制备了密封型硅钙镁磷肥、粘结型硅钙镁磷肥、改性硅丙树脂3种包膜尿素,通过静水试验研究了此3种包膜尿素的释放特征。结果表明,3种包膜尿素的释放周期分别为60、79、96 d,在水中均能保持完整球形,耐水性较好。通过扫描电镜、红外光谱、X-射线衍射法对膜材形貌特征和结构进行表征,发现钙镁磷肥和硅丙树脂为成膜材料;甲基硅酸钠作为密封剂和防水剂参与了成膜反应,有效增加了膜材的塑性和韧性,此复合材料可用作缓控释肥的胶结剂和包膜剂。

PEFT聚酯的制备及PEFT纳滤膜的截留性能

为了解决聚对苯二甲酸乙二醇酯(PET)材料制品使用后降解缓慢和聚2,5-呋喃二甲酸二甲酯(PEF)韧性差的问题,开发一种新型嵌段共聚酯聚2,5-呋喃二甲酸-乙二醇-co-对苯二甲酸酯(PEFT),可通过酯交换-熔融缩聚法合成,且PEFT拥有与PEF相媲美的热力学性能。利用FTIR及NMR等对聚酯结构进行表征,结果表明该方法成功制备了PEFT聚酯。通过TG、DSC和紫外光照表征,结果表明PEFT聚酯热学性能优良,且在紫外光照射下可快速降解。又将PEFT聚酯材料通过非溶剂致相分离法(NIPS)制备了不同铸膜液浓度的PEFT纳滤膜,用于对染料离子及金属盐溶液的截留,而后对其表面粗糙度、水接触角、荷电性、染料和金属盐离子的截留能力等方面进行了测试。结果表明:PEFT纳滤膜对甲基蓝(Mr=799.8)染料、酸性品红(Mr=585.4)染料都具有良好的截留性能,最高截留率可达99%和87.7%,并且纳滤膜经长期循环后仍具有较高的稳定性,但对金属盐(MgSO4)溶液截留性能不佳,截留率最高不超过35%。综合研究发现PEFT纳滤膜在染料截留方面性能突出。

印染废水处理用MOFs基光催化分离膜的制备及改性

MOFs基光催化分离膜综合了膜分离和光催化技术的优点,能够高效处理染料废水,降低膜污染,在印染废水处理领域中具有独特优势。介绍了MOFs光催化材料的类型和特点,概述了MOFs基光催化分离膜的制备方法,包括相转化法、界面聚合法、真空过滤法、静电纺丝法和原位生长法等,重点分析了光催化分离膜的改性方法,包括配体修饰、贵金属沉积、助催化剂修饰、固定聚氧金属酸盐和构筑异质结等。指出了MOsF基光催化分离膜目前实际应用中面临的主要问题和未来的研究方向。

胶囊形气膜结构风致气弹响应及风振系数研究

针对1/3矢跨比胶囊形气膜结构进行了气弹模型风洞试验,研究了结构的风致气弹响应变化规律,并给出了可供设计参考的风振系数。研究发现:结构平均变形呈迎风面凹陷,顶部隆起,横风向向外凸出的趋势,且这种变形趋势随着内压减小和风速增大越来越明显。0°风向角时的平均变形和振幅大于45°风向角时的平均变形和振幅大于90°风向角时的平均变形和振幅,结构合位移均值的极值出现在迎风面与顶面中心点;0°和45°风向角下,顶点竖向振幅>顺风向振幅>横风向振幅,结构以1阶模态振动为主;90°风向角下,顶点横风向振幅大于其他两个方向,结构以1阶和2阶模态叠加振动为主。各工况下结构的内压均有不同程度的减小。最后给出了考虑流固耦合效应的响应风振系数。

激光熔覆原位Ti-C-B-Al复合涂层的结构特征与力学性能

以钛粉、铝粉和碳化硼粉末为原料,采用同步同轴激光熔覆系统在Ti6Al4V钛合金表面制备含原位自生TiC、TiB以及TiAl金属间化合物增强钛基的Ti-C-B-Al复合涂层,研究了复合涂层的显微组织、物相构成、显微硬度和微纳米力学性能。结果表明,三种粉末在高能激光束的作用下充分反应并生成了TiC、TiB以及TiAl金属间化合物增强相。复合涂层表面光滑,涂层内部无气孔及裂纹,与基体间形成了良好的冶金结合,增强相在涂层内分布均匀,相比于基体,熔覆涂层具有较优的力学性能。涂层硬度在460HV_(0.3)~510HV_(0.3)之间,同时涂层的纳米力学性能与显微硬度具有较好的对应关系,其中当m(Ti)∶m(Al)∶m(B_(4)C)=84∶12∶4时,制得的涂层具有较优的力学性能。

适应软土地基的港口铁路路基方案优化

利用软土吹填造陆形成的港区,地基基底承载力通常较差,对铁路路基的设计要求较高。结合港口铁路货运虽然重载、但是多为尽端线路,或装卸线居多,运行速度较低等特点,以黄骅港某铁路路基工程为例,结合目前软土地基上路基设计基本方案,提出改进的路基设计方案。通过技术经济分析,优化改进适应港口软土地基、技术上满足承载力要求,经济上更合理的铁路路基结构形式,并在工程中应用。