高炉冷却壁与炉气之间的换热特性

 基于边界条件替换方法建立了高炉冷却壁本体和捣打料与炉气之间的换热系数计算模型。用试验测量冷却壁近热面温度来推算冷却壁热面温度，与冷却壁温度场计算模型结合，确定了炉气温度在500~1 248 ℃范围内，高炉冷却壁与炉气之间的换热系数。结果表明，本模型的计算值与前苏联学者的试验结果吻合。     

低热值煤气Ⅰ型辐射管烧嘴的实验研究

通过实验研究,得到一种超低热值煤气Ⅰ型辐射管烧嘴,该烧嘴可适用煤气最低热值达4598 kJ/m3(1100kcal/m3).点火实验结果表明:烧嘴火焰检测信号随着煤气热值下降逐步减弱,随着空气消耗系数的增加而增强,随着供气流量的加大而增强.实验烧嘴除可适用低热值煤气外,同时还具有热效率高、加热温度均匀性好和有害气体排放低等优点.     

Development of a mathematical model for multihearth roasters

A simultaneous heat and mass transfer model has been developed for the multiheart roasters, considering dead roasting of chalcopyrite as a typical roasting reaction. Various mass and energy balances have been worked out during the development of this model yielding coupled nonlinear partial differential equations with highly complex boundary conditions. These equations have been solved numerically using a line-by-line finite difference approach to obtain profiles of gas temperature, solid temperature, oxygen concentration, and solid fraction reacted in the roaster. The trend of the computed results appears to be realistic and can be easily explained from simple physical considerations. The effects of gas preheating and the heat transfer coefficient between the solid and the gas upon the roasting process are examined. The results show that gas preheating is beneficial for the roasting process, and the process parameters, such as particle size, gas flow rate,etc., must be adjusted so as to give the desirable value of the heat transfer coefficient needed for proper roasting.     

Mass Transfer of Ozone in Semibatch Stirred Reactor

The mass transfer of ozone from the gaseous phase into the aqueous phase plays an important role in determining the efficiency of ozonation. In this study, a mass-transfer model has been developed to simultaneously predict concentrations of the dissolved and outlet gaseous ozone in a semibatch reactor. A model in which the liquid phase is described as well mixed and the gas phase is described as a plug-flow system was used to estimate the mass transfer of ozone in both laboratory and pilot reactors. The self-decomposition of ozone was also incorporated into the model. The mass-transfer coefficient was found to increase with increasing gas flow rate, temperature, and ionic strength in the solution. Using a sensitivity analysis, the partition coefficient α was found to be the most sensitive factor that affects the concentration profile of dissolved ozone. However, the outlet gaseous concentration of ozone is quite insensitive to all physical parameters investigated in this study.     

Analysis of bath smelting processes for producing iron

A simulation model on bath smelting processes for the production of iron was developed which predicts the coal, flux, ore, and oxygen consumptions and the off gas volume, temperature and composition. The model is comprehensive in that it takes into account all of the important variables including coal composition, metal composition, ore composition, slag basicity, post combustion ratio, (PCR), prereduction degree (PRD), heat transfer coefficient (HTC), flux, scrap charge, and heat losses. Four basic cases were considered: I. 30% PRD–50% PCR; II. 90% PRD–0% PCR; III. 60% PRD–30% PCR; and IV. 0% PRD–50% PCR. Several different coals were considered and a sensitivity analysis of the critical variables was performed. The model also estimates the sulfur content of the metal. The major conclusions are: Post combustion siginificantly reduces coal consumption but above 20% PCR little reduction of FeO to Fe can be performed with the off gas. Prereducing to FeO (case I) and having as much post combustion as consistent with good heat transfer is an attractive process. This process only requires a simple prereducer, uses less coal, and is relatively insensitive to the type of coal used. High off-gas temperatures may pose a potential problem. The off-gas temperature can be reduced by using an O₂–air mixture for post combustion, limiting post combustion or adding water to the gas. The use of CaCO₃ in place of CaO or of supplemental electricity does not appear attractive. The melting unit is theoretically an energy efficient scrap melter. For case I using 200 kg of scrap as part of the charge the coal consumption decreases by about 80 kg. With PCR > 30% the FeO content of the slag is expected to be 2–5%, and the metal will not be saturated with carbon. These factors and the increased sulfur load since coal is the fuel indicate the sulfur content of the metal may exceed 0.25%.     

Modeling of porosity during spray forming: Part II. Effects of atomization gas chemistry and alloy compositions

In this article, the effects of gas chemistry and alloy composition on the level of porosity in deposited materials are investigated by using a porosity model established in Part I of this article. The calculated results reveal that atomization gas chemistry has a significant influence on the level of porosity during spray forming, which can be rationalized on the basis of the influence of gas properties such as gas density, viscosity, and gas constant on the melt flow rate. The alloy properties that predominantly affect the variation of porosity with melt flow rate include melt viscosity, density, surface tension, solvent melting point, liquidus temperature, and equilibrium partition coefficient. A material property factor, μ _mγ_m/ρ ² _m , plays an important role in determining the processing conditions required to attain a minimum amount of porosity in deposited materials.     

铜精炼阳极转炉氧化期烟气的传热特性

根据能量平衡原理,建立烟气对铜液的传热模型,并对不同空气过剩系数下的烟气平均温度和传热强度进行计算。结果表明:随着空气过剩系数的增大,烟气平均温度和传热强度均有明显下降。为增强烟气对铜液的传热能力,必须适当地减小空气过剩系数。此外,针对燃烧室排烟温度较高的问题,提出采用余热装置回收烟气余热的合理建议。     

Small intrapulmonary artery lung prototypes. Mathematical modeling of gas transfer

Two diffusion models have been developed to analyze gas transfer data previously measured in an intravascular artificial lung consisting of a central gas supply catheter from which are tethered a large number of blind-ended microporous fibers of equal length. A convective-diffusion model (CD) describes the countercurrent transfer of a binary gas pair when gas is supplied at constant pressure conditions, and a well mixed (WM) cycled pressure model predicts transfer when the gas supply pressure is time cycled between compression and vacuum conditions. Regression of gas to gas and liquid to gas excretion data with the CD model resulted in estimates of the liquid phase mass transfer coefficient kAI. Because these values were intermediate between the kAI expected for flow parallel to a cylinder and for flow normal to a cylinder, gas transfer was influenced by both the tethered region of the fiber that was nearly perpendicular to the axis of the test section and the free end of the fiber that rested along the wall of the test section. With a time cycled gas supply pressure, the enhanced carbon dioxide and oxygen excretion predicted by the WM model was similar to the data, but a loss in transfer efficiency with fiber length was not accounted for by the theory.     

纳微米级孔隙气体流动数学模型及应用

对纳微米级孔隙多孔介质内的气体流动进行了研究.利用克努森数划分流态,绘制了流态图版,阐明了不同区域的流动特征.基于Beskok-Karniadakis模型,对渗透率校正系数进行了改进,引入多项式修正系数,将Beskok-Karniadakis模型简化为二项式方程,并利用最小二乘法分段拟合得出多项式修正系数的取值.模型对比显示,简化后的模型具有较高的精确度.应用此模型推导出了纳微米级孔隙气体流量的计算公式.进行了室内微观渗流模拟实验,得到气体平面单向渗流规律,与由纳微米级孔隙气体流量公式计算所得渗流特征进行对比,结果显示本模型与实验数据拟合较好.采用本模型进行编程计算,对其影响因素进行分析,发现气体流量随压力平方差增加而增大,且增加趋势越来越快,并随多孔介质渗透率和克努森扩散系数的增加而增大.      

FeNiCrSiMoMnC合金气雾化熔滴的运动与传热行为模拟分析

气雾化过程中合金液流被高压气流破碎后,要飞行一段距离才开始冷却凝固,这称为熔滴的飞行过程。本文以重载耐磨耐腐蚀激光熔覆涂层用FeNiCrSiMoMnC合金为对象,通过建立熔滴飞行过程的模型,并对该过程进行数值模拟,计算讨论了雾化气体初始速率、熔滴直径对熔滴的速度、传热系数等参数的影响。结果表明,熔滴速度呈现先增大至最大值后逐渐减小的趋势,且随熔滴直径的增大,熔滴速度最大值点逐渐降低;传热系数与速度曲线相反,呈先下降后上升的趋势,极小值为2kg/d,熔滴直径越大,与气体速度差越小,传热系数越小;随气体初始速率的增大,熔滴最大速度点上移,同时传热系数也逐渐增大。     

Mass Transfer of Ozone in a Novel In Situ Ozone Generator and Reactor

A porous tubular reactor that also served as an electrode for ozone generation was studied in this research to determine the effects of in situ ozone generation on mass transfer and reaction rates. Experimental data over a range of gas flow rates and ozone generation rates gave KLa values in the range 0.77–1.14?min?1. These values are more than double the values typically reported for bubble columns, and about 30% higher than that for packed beds. The specific power requirement for the laboratory-scale in situ reactor is an order of magnitude lower than that for bubble columns and stirred tank reactors that are used for ozone dissolution. A compartments-in-series fluid flow model was developed to describe the reactor system, and this model provides a good comparison to the experimental data for dissolved ozone and off-gas concentrations in the reactor. Sensitivity analyses indicate that the dissolved and off-gas ozone profiles are most sensitive to the gas–liquid partition coefficient and the overall mass transfer coefficient.     

A Mathematical Model to Characterize RH Desulfurization Process

A physical model based on similarity principles was built to simulate RH desulfurization process. In order to quantitatively analyze RH desulfurization process, a mathematical model was proposed. By analyzing experimental results with the mathematical model, an empirical formula whose determination coefficient was 0.98 was given to express the relationship between transient desulfurization efficiency and time. All the determination coefficients of four fitted curves based on four repeated experiments with different gas flow rates were more than 0.94, which was the exact evidence of the rationality of the empirical formula. Meanwhile, it was found that transient desulfurization ability increased firstly and then decreased with increasing gas flow rate and reached the maximum value when the gas flow rate was 1.8 m^3/h. A plenty of repeated trials showed the same rule, which validated the mathematical model and the conclusions obtained from physical experiments.     

页岩气渗流特征及压裂井产能

依据分子运动学理论,对含纳米孔隙页岩储层气体渗流规律进行理论分析,建立适用于多尺度介质的气体运动方程和页岩气输运数学模型,得到径向流条件下的压力分布公式,形成页岩气井控制区域计算方法,建立了压裂井三区耦合非线性渗流产能方程.采用牛顿迭代法进行数值计算,研究分析了生产压差、裂缝半长、裂缝导流能力、扩散系数等参数对页岩气井产量的影响.计算结果表明:气井产量随扩散系数的增大而增大,对于含纳米孔隙的页岩储层中扩散效应对气井的产量贡献不容忽视;在一定的储层和生产条件下,气井产量随裂缝半长的增大而先快速增大后趋于平缓,因此存在一个最佳范围,各参数应进行定量的、合理的优化配置.      

Oxygen Transfer Model for a Flow-Through Hollow-Fiber Membrane Biofilm Reactor

A mechanistic oxygen transfer model was developed and applied to a flow-through hollow-fiber membrane-aerated biofilm reactor. Model results are compared to conventional clean water test results as well as performance data obtained when an actively nitrifying biofilm was present on the fibers. With the biofilm present, oxygen transfer efficiencies between 30 and 55% were calculated from the measured data including the outlet gas oxygen concentration, ammonia consumption stoichiometry, and oxidized nitrogen production stoichiometry, all of which were in reasonable agreement. The mechanistic model overpredicted the oxygen transfer by a factor of 1.3 relative to the result calculated from the outlet gas oxygen concentration, which was considered the most accurate of the measured benchmarks. A mass transfer coefficient derived from the clean water testing with oxygen sensors at the membrane-liquid interface was the most accurate of the predictive models (overpredicted by a factor of 1.1) while a coefficient determined by measuring bulk liquid dissolved oxygen underpredicted the oxygen transfer by a factor of 3. The mechanistic model was found to be an adequate tool for design because it used the published diffusion and partition coefficients rather than requiring small-scale testing to determine the system-specific mass transfer coefficients.     

Hydrodynamics of gas stirred melts: Part II. Axisymmetric flows

A predictive model of gas stirred melt is presented. Based on the differential approach and following a review of previous models, the importance of natural convection or buoyancy driven phenomena is underscored. Predicted flow patterns are shown to be consistent with laboratory and pilot scale experiments, and with the macroscopic plume model in Part I of this paper.     

Inactivation of Cryptosporidium Oocysts in a Pilot-Scale Ozone Bubble-Diffuser Contactor. I: Model Development

A mathematical model was developed to simulate the performance of a pilot-scale ozone bubble-diffuser column. The reactor hydrodynamics was represented with the axial dispersion reactor model. An analytical solution was developed for the liquid and gas phase ozone mass balances in which dissolved ozone decomposes by first-order kinetics. Numerical approximations were provided for the mass balances for viable microorganisms and the more general case of dissolved ozone decomposition through a second-order reaction with fast ozone demand in natural organic matter. Model components required to predict the liquid and gas phase ozone concentration and viable microorganism number density profiles throughout the bubble-diffuser column included input parameters (liquid and gas flow rates, influent gas and dissolved ozone concentrations, temperature, and countercurrent or cocurrent operation mode), empirical correlations (dispersion number, volumetric mass transfer coefficient, Henry’s law constant), and batch or semibatch kinetic information (ozone decomposition rate constants and fast-ozone demand, and microorganism inactivation lag phase and rate constant). A sample model run for the case of first-order ozone decomposition revealed that the analytical and numerical solutions were practically identical.     

High-performance liquid chromatographic determination of clindamycin in human plasma or serum: application to the bioequivalency study of clindamycin phosphate injections

This paper presents an assay of clindamycin phosphate injection in human plasma or serum. A 0.5-ml volume of plasma was used with the internal standard, propranolol. The sample was loaded onto a silica extraction column. The column was washed with deionized water and then eluted with methanol. The eluates were evaporated under nitrogen gas. The residue was reconstituted with the mobile phase and injected onto the high-performance liquid chromatographic system: a 5-micron, 25 cm X 4.6 mm I.D. ODS2 column was used with acetonitrile, tetrahydrofuran and 0.05 M phosphate buffer as the mobile phase and with ultraviolet detection at 204 nm. A limit of quantitation of 0.05 microgram/ml was found, with a coefficient of variation of 11.6% (n = 6). The linear range is between 0.05 and 20.00 micrograms/ml and gives a coefficient of determination (r2) or 0.9992. The method has been successfully applied to the bioavailability study of two commercial preparations of clindamycin phosphate injection (300 mg each) in twelve healthy adult male volunteers.     

三维分格式焦炉蓄热室传热分析与数值模拟

通过构建真实比例的三维分格式焦炉蓄热室模型,利用CFD软件,模拟计算了实际炼焦过程中蓄热室内周期性非稳态的传热过程,计算值与实际测量值相吻合。结果表明,分格式焦炉蓄热室顶部空间处,在加热期内容易产生较强的气体涡流运动,加强了其与格子砖的换热作用,导致了加热初期的温度梯度异常;得到了不同高度的焦炉格子砖内气固两相温度的周期性变化规律。还考察了格子砖导热系数以及废气流量分配系数对于蓄热室换热效果的影响,发现格子砖导热系数的增大,将导致蓄热室温度效率降低、出口气体温降升高,变化规律呈线性相关;发现操作条件下最佳的废气流量分配系数约为0.94,该废气流量分配系数下的空气与煤气蓄热室的温度效率最为接近。     

Perturbation Solutions for Thermal Process of Honeycomb Regenerator

 A parameter perturbation for the unsteady state heat transfer characteristics of honeycomb regenerator is presented. It is limited to the cases where the storage matrix has a small wall thickness so that no temperature variation in the matrix perpendicular to the flow direction is considered. Starting from a two phase transient thermal model for the gas and storage matrix, an approximate solution for regenerator heat transfer process is derived using the multiple scale method for the limiting case where the longitudinal heat conduction of solid matrix is far less than the convective heat transfer between the gas and the solid. The regenerator temperature profiles are expressed as Taylor series of the coefficient of solid heat conduction item in the model. The analytical validity is shown by comparing the perturbation solution with the experiment and the numerical solution. The results show that it is possible for the perturbation to improve the effectiveness and economics of thermal research on regenerators.     

CO2吸收模型中容积传质系数的确定

气泡微细化是“原位机械搅拌法铁水炉外脱硫技术”的关键.气液传质系数是研究气液吸收过程的基本参数.本文根据相似性原理建立水模型实验装置,并通过测定NaOH吸收CO2的速率来研究气泡微细化过程,同时根据吸收原理定量计算出容积传质系数Ak及CO2气体利用率η.当溶液pH值从12降低到9的过程中,容积传质系数为2.938×10 4m3/s,本实验所用CO2的利用率的公式可简化为:η=18.98/Qt.本论文的研究结果可为进一步研究吸收速率提供理论依据.