碳酸钙在流动过冷沸腾条件下的结垢机理研究

Fouling of heat transfer surfaces during subcooled flow boiling is a frequent engineering problem in process industries. It has been generally observed that the deposits in such industrial systems consist mainly of calcium carbonate （CaCO3）, which has inverse solubility characteristics. This investigation focused on the mechanism to control deposition and the morphology of crystalline deposits. A series of experiments were carried out at different surface and bulk temperatures, fluid velocities and salt ion concentrations. It is shown that the deposition rate is controlled by different mechanism in the range of experimental parameters, depending on salt ion concentration. At higher ion concentration, the fouling rate increases linearly with surface temperature and the effect of flow velocity on deposition rate is quite strong, suggesting that mass diffusion controls the fouling process. On the contrary, at lower ion concentration, the fouling rate increases exponentially with surface temperature and is independent of the velocity, illustrating that surface reaction controls the fouling process. By analysis of the morphology of scale, two types of crystal （calcite and aragonite） are formed. The lower the temperature and ion concentration, the longer the induction period and the higher the percentage of calcite nreciDitated.     

CHARACTERISTICS OF NEW CATHODE MATERIAL FOR LTSOFC INVESTIGATED BY IMPEDANCE SPECTROSCOPY

The characteristics of a new Li-NiO cathode were investigated. The crystal structure of Li-NiO was explored by XRD. Electrochemical behaviors of Li-NiO composite cathode were revealed by impedance spectroscopy from 400℃ to 650℃. The diameter of deformed arc increased with the decrease of temperature. Above the melting point of the eutectic salt in composite electrolyte, the Li-NiO curves are similar with two deformed semicircular arcs at high frequency which partially overlaps each other and corresponds...     

Model for seawater fouling and effects of temperature,flow velocity and surface free energy on seawater fouling☆

A kinetic model was proposed to predict the seawater fouling process in the seawater heat exchangers.The new model adopted an expression combining depositional and removal behaviors for seawater fouling based on the Kern–Seaton model.The present model parameters include the integrated kinetic rate of deposition(k d)and the integrated kinetic rate of removal(k r),which have clear physical signi ficance.A seawater-fouling monitoring device was established to validate the model.The experimental data were well fitted to the model,and the parameters were obtained in different conditions.SEM and EDX analyses were performed after the experiments,and the results show that the main components of seawater fouling are magnesium hydroxide and aluminum hydroxide.The effects of surface temperature,flow velocity and surface free energy were assessed by the model and the experimental data.The results indicate that the seawater fouling becomes aggravated as the surface temperature increased in a certain range,and the seawater fouling resistance reduced as the flow velocity of seawater increased.Furthermore,the effect of the surface free energy of metals was analyzed,showing that the lower surface free energy mitigates the seawater fouling accumulation.     

Preparation and Application of Nano-composite Poly(vinyl alcohol) Gel Electrolyte in Electrochemical Capacitor

A nano-composite polymer gel electrolyte was prepared using titanium oxide nanowire, poly(vinyl alcohol) (PVA), lithium salt and organic solvent N-methyl-2-pyrrolidone (NMP). The obtained electrolyte has the potential for application in electrochemical capacitor, the PVA in it is in an amorphous state. The ionic conductivities of electrolytes increased after addition of the nanowire, and the electrolyte with 3%(w) of nanowire exhibited the highest ionic conductivity of 3.2 mS/cm at 20℃, as measured by electrochemical impedance spectroscopy. The temperature dependence of the conductivity was found to be in agreement with the Arrhenius equation. Functioning as separator and electrolyte, this nano-composite PVA gel electrolyte was used to assemble the electrochemical capacitor with active carbon film as electrodes. The compositing of nanowire may extend the life of electrochemical capacitors as they keep more than 90% of their capacitance after 5000 cycles of charging and discharging.     

绝热固定床反应器甲醇脱水合成二甲醚的实验和模型研究

One-dimensional heterogeneous plug flow model was employed to model an adiabatic fixed-bed reactor for the catalytic dehydration of methanol to dimethyl ether. Longitudinal temperature and conversion profiles predicted by this model were compared to those experimentally measured in a bench scale reactor. The reactor was packed with 1.5 mm γ-Al2O3 pellets as dehydration catalyst and operated in a temperature range of 543-603 K at an atmospheric pressure. Also, the effects of weight hourly space velocity (WHSV) and temperature on methanol conversion were investigated. According to the results, the maximum conversion is obtained at 603.15 K with WHSV of 72.87 h－1.     

强制对流传热的换热表面结垢特性实验研究

An experimental study was conducted to investigate the fouling process of calcium carbonate on the heat transfer surface, during forced convective heat transfer. The dynamic monitoring apparatus of fouling resistance was set up for the present experiments. The fouling behavio（s were examined under different factors including fluid velocity, hardness,alkalinity, solution temperature, and wall temperature. Asymptotic fouling curves varying with time were obtained. The fouling rate and asymptotic fouling resistance increased and the induction periods were shortened with the fluid velocity decreasing, hardness andalkalinity increasing, and solution temperature and heat transfer surface temperature increasing. Thecomponents of fouling that formed on the heat transfer surface included crystallization fouling and particulate fouling. The thermal performance parameter of fouling,ρfhf, varied from 380 to 2600 kg·W·（m^4·K）^-1, increasing with growing velocity and decreasing solution temperature, hardness or alkalinity. Furthermore, the thermal conductivity of fouling, λf, varied from 1.7 to 2.2 W·（m·K）^-1 .     

Fouling characteristics of 90° elbow in high salinity wastewater from coal chemical industry

Due to the high salt content of coal chemical wastewater, pipeline fouling often occurs during wastewater treatment. Fouling will cause the diameter of the pipe to shrink or even block, which is not conducive to the safe and stable operation of the wastewater treatment process. In this paper, the experimental device was designed by using FLUENT software and the fouling deposition mechanisms at different flow velocities and different positions in a 90 deg bend were studied. The experimental results show that when the flow velocity is between 0.2 m·s~(-1) and 0.3 m·s~(-1), the thickness of fouling layer was positively correlated with the flow velocity; when the flow velocity is equal to 0.4 m·s~(-1), the formation of fouling is the most serious; when the flow velocity is between 0.4 m·s~(-1) and 0.7 m·s~(-1), the thickness of fouling layer was negative correlation with the flow velocity; with the increase of inlet velocity, the time for sediment point to develop into sediment surface is shortened. The fouling layer is easy to fall off because of the large shear force on the wall surface of the inner bend of the 90° elbow, so the density of sediment at this position is high.     

A robust predictive tool for estimating CO2 solubility in potassium based amino acid salt solutions

The acid gas absorption in four potassium based amino acid salt solutions was predicted using artificial neural network(ANN). Two hundred fifty-five experimental data points for CO_2 absorption in the four potassium based amino acid salt solutions containing potassium lysinate, potassium prolinate, potassium glycinate, and potassium taurate were used in this modeling. Amine salt solution's type, temperature, equilibrium partial pressure of acid gas, the molar concentration of the solution, molecular weight, and the boiling point were considered as inputs to ANN to prognosticate the capacity of amino acid salt solution to absorb acid gas. Regression analysis was employed to assess the performance of the network. Levenberg–Marquardt back-propagation algorithm was used to train the optimal ANN with 5:12:1 architecture. The model findings indicated that the proposed ANN has the capability to predict precisely the absorption of acid gases in various amino acid salt solutions with Mean Square Error(MSE) value of 0.0011, the Average Absolute Relative Deviation(AARD) percent of 5.54%,and the correlation coefficient(R~2) of 0.9828.     

常压盐溶液脱硫石膏转化生成α-半水石膏

Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pres-sure was investigated.The effects of temperature,salt species,salt concentration,solids content,pH and modifier were examined.The crystals obtained under different conditions and solubility of calcium sulfate in contact with solid gypsum were also determined.α-Calcium sulfate hemihydrate crystals of stubby columnar shape and regular pentahedral sides were obtained under the following conditions:salt concentration 20%-30%,operation tempera-ture 95-100 °C,solids mass content in the slurry 10%-30% and neutral pH.Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium sulfate hemihydrate occurs because of the difference in solubilities between the two solid gypsum phases in this system.     

Effect of heat flux and inlet temperature on the fouling characteristics of nanoparticles

In order to study the effect of heat flux and inlet temperature on the fouling characteristics of nanoparticles, and to further reveal the fouling mechanism for insights into proper operating conditions, γ-Al_2O_3/water suspensions were chosen as the subject of this research. The particulate fouling characteristics of γ-Al_2O_3/water suspensions on the surface of stainless steel have been experimentally studied by varying the heat flux and the inlet temperature under single-phase flow and subcooled-flow boiling conditions. The results show that in the condition of single-phase flow, the asymptotic value of fouling resistance decreases with increasing of heat flux and inlet temperature. The asymptotic value of fouling resistance under single-phase flow is much higher than for the subcooled-flow boiling condition. The effect of heat flux on the fouling resistance under the two flow states has an inverse relationship, and there exists a minimum value of fouling resistance between these two states. For subcooled-flow boiling, the asymptotic value of fouling resistance increases with increasing heat flux, whereas the effect on fouling resistance by the inlet temperature is negligible.     

MAS阻垢剂的合成及性能评价

以含有羧基、磺酸基等官能团的烯类单体为原料,以过硫酸铵和亚硫酸氢钠组成的氧化-还原体系为引发剂,采用水溶液法进行加成聚合,合成了三元共聚物MAS,并采用静态阻垢实验对MAS的阻垢效果进行了评定。结果表明,MAS具有很好的络合Ca2+能力,最佳投加质量浓度为16 mg/L。     

几种难溶垢及常用清洗药剂

介绍济宁新格瑞水处理有限公司近年在无机垢、有机物料垢、油脂类污垢清洗剂开发方面的技术成果、经验与产品应用案例,并指出了清洗药剂开发面临的瓶颈问题,对未来清洗技术的发展进行了展望。     

萨南油田管道成垢原因及治理措施研究

对大庆萨南油田各种水质及垢堵塞物成分进行分析,确定主要成垢因素。针对成垢的影响因素,结合生产实际,提出相应的物理防、清垢措施,有效地降低了垢对油田生产造成的影响。     

新型硫酸钡阻垢剂的合成与性能评价

以马来酸酐(MA)、丙烯酸(AA)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)和丙烯酸甲酯(MAC)为单体,采用水溶剂聚合法,合成了一种新型四元共聚物阻垢剂;研究了聚合条件对共聚物阻硫酸钡垢性能的影响,确定了最佳合成条件,单体摩尔比n(MA): n(AA): n(AMPS): n(MAC)=7: 6: 2: 4,引发剂...     

聚环氧琥珀酸的合成及其阻垢性能研究

研究了各种合成条件对聚环氧琥珀酸钠阻垢性能的影响,得到了合成聚环氧琥珀酸钠的最佳工艺条件为:环氧琥珀酸钠与氢氧化钙的量比为1:0.016,反应时间3h,反应温度95℃。通过对产物的红外光谱分析,证明产物与聚环氧琥珀酸钠有相同的基团。通过对不同投加量的PESA阻垢性能测试表明:在投加量分别为10和80mg/L时,对硫酸钡垢、硫酸锶垢的阻垢率可达100%。并初步探讨了其阻垢机理。     

水垢防治技术研究进展

简要介绍了水系统的成垢机理及几种典型的化学、物理防垢方法,总结了各防垢方法的发展情况与存在问题:化学法简单易行、稳定高效,但对环境易造成危害,物理法控制简便、经济环保,但效果不稳定、原理复杂。指出开发环境友好型阻垢剂及高效的物理防治方法将是水垢防治的发展方向。     

石化设备油垢焦垢化学清洗技术分析

对石化设备的油垢类型与形成作了分析 ,并对化学清洗方法的选用、清洗剂组成作了讨论与举例 .     

含醚键的四元共聚物防垢剂的制备及性能

针对油田三元复合驱过程产生的硅垢和钙垢,本文以马来酸酐、次亚磷酸钠、丙烯酰胺、聚乙二醇4000为单体,过硫酸铵-亚硫酸氢钠为引发剂,合成了一种新型四元共聚物防垢剂。确定了最佳合成条件,考察了防垢剂的防垢效果。结果表明,防垢剂加量100 mg/L、60 ℃时,测定硅垢防垢率为67.2%;70 ℃时,测定CaCO3垢防垢率为96.3%。指出四元共聚物防垢剂中的4种官能团的协同作用机理主要是晶格畸变与静电斥力作用;而由于聚乙二醇价格高,寻找价格低廉可降解的含醚键化合物是以后实验的主要研究方向。     

浅析PET装置的规模效应

介绍了大型PET装置与传统小型PET装置的区别,分析了大型PET装置因规模大而在建设投资、运行成本、生产运行等方面产生的规模效应,通过年产50万t与年产20万t装置的对比,量化了大型PET装置因规模效应而带来的建设投资和运行成本等方面的效益和好处。     

我国阻垢剂的研究进展

介绍了阻垢剂的4种阻垢机理,即螯合增溶作用、凝聚与分散作用、静电斥力作用、晶体畸变作用,综述了天然聚合物阻垢剂、含磷类聚合物阻垢剂、共聚物阻垢剂、绿色新型阻垢剂的性能及特点,重点对绿色新型阻垢剂聚环氧琥珀酸和聚天冬氨酸进行了讨论,并展望了阻垢剂的发展方向。