卸油鹤管的气阻问题及解决措施

油罐车在高温季节和高原地区接卸汽油时经常产生鹤管气阻,导致罐车下部的油料不能下卸。针对这一问题,分析了鹤管气阻产生的机理,提出了鹤管气阻的校核方法。根据分析和研究,提出了几种新的气阻防治措施。     

化工过程常见气阻现象及其解决措施

气阻现象是管道输送故障的一个类型,有气体且能集聚在一起,是发生气阻的必要条件,在化工生产中,它的产生会影响液体的输送效率或对管路、泵造成损害,甚至造成管路断流。本文结合工程实例,对气阻现象产生的原因进行分析,从工艺流程、管道布置的设计,以及管路使用过程等方面提出了一些预防和解决措施,对有效地解决气阻现象问题进行了有益的探讨。     

离心泵的汽蚀原因及预防措施

汽蚀现象是离心泵使用中常见的问题,针对离心泵的汽蚀现象,分析了汽蚀产生的原因及危害,通过对汽蚀理论中有效汽蚀余量和必须汽蚀余量的研究,探讨了增强离心泵抗汽蚀性能的方法,从离心泵的设计、安装等角度提出了预防汽蚀发生的措施,以避免汽蚀发生,提高泵的运行效率。     

煤气化装置除氧水泵汽蚀振动的探讨及处理

为了解决气化装置除氧水泵频繁出现振动故障的实际问题,对进口管道布置、泵出口流量、泵壳温度、进口压力及联轴器同心度引起振动的原因进行了分析,并叙述了优化、处理措施。结果显示,泵进口管道布置的缺陷导致管道内易积渣或结垢,使管道有效尺寸减小,出现汽蚀现象;泵出口最佳效率点流量近似为215 m3/h,偏离最佳效率点流量较大时,会使泵壳温度升高,引起汽蚀振动;泵进口压力在300~320 k Pa范围、泵壳温度低于115℃时,不会发生汽蚀现象,振动值较小;泵与电机之间联轴器的同心度偏差大时,泵振动值会增大。     

屏蔽泵汽蚀的防护措施及评价

针对屏蔽泵的结构特点。分别从泵体和屏蔽电机等方面着手分析其发生汽蚀的原因和机理，从而提出对泵汽蚀的防护措施，并做出相应的评价。     

化工装置中离心泵气蚀现象及实例探讨

文章主要通过笔者的工作实践,阐述了离心泵的工作原理,提出了离心泵的气蚀余量及发生气蚀的部位,探讨了离心泵气蚀的危害性,提出了离心泵的气蚀的预防措施,并结合工程实例,针对某石化公司离心泵在运行过程中出现严重汽蚀的问题,从离心泵产生汽蚀的机理及流体力学方面的基本公式,分析超流量对泵汽蚀的影响,并总结出引起离心泵汽蚀的常见原因及其解决方法。     

焦化装置放空塔底泵汽蚀原因分析及改善措施

某延迟焦化装置正常生产期间,放空系统塔底泵在冷焦处理生产节点频繁发生汽蚀现象,因而经常引发生产波动及设备故障等问题,通过分析确定该泵发生汽蚀以及导致汽蚀现象加剧的本质原因,结合装置生产特性及相关参数历史趋势,最终确定了针对性改善措施:控制该泵运行流量;改善放空塔底油性质;改善塔底抽出过滤器;优化塔底液位与塔内压力。随着各项措施的相继实施,明显改善了放空塔底泵的汽蚀现象。文章最后提出了进一步的改善方向。     

铁路卸油气阻问题探究及工艺优化

铁路卸油过程中在鹤管的最高远端极易形成气阻断流。在高温天气卸油时,此问题更加突出。为了解决此问题,国内一些学者已经提出了多种较为完善的卸油工艺。本文通过对气阻问题和已有工艺的分析和研究,来进一步优化铁路卸油工艺以取得更好的效果和经济效益。     

P-206B泵气蚀及管线振动的原因分析

将针对贫吸收液泵出入口管线异常振动,容易发生汽蚀,流量和压力不稳定,分析了产生振动合汽蚀的原因。通过计算核对泵的出入口管线安装、机械结构设计,到泵的高度,提出了减缓泵振动的措施。结果表明,机泵实际安装高度不合理,但是改变泵的安装高度从经济方面考虑不合理,只能从改变泵的入口管线和将泵发生汽蚀易损坏的部件,进行存在升级更换为抗汽蚀的304L不锈钢材质,来减缓汽蚀对泵造成的损坏。     

CNF40-250屏蔽电泵的修复技术

CNF40-250屏蔽电泵在运行过程中,轴向平衡不良和泵发生汽蚀现象造成轴承损坏,从几方面加以分析,提出了改进及修复措施,使问题得到了解决。     

汽油饱和蒸汽回收方法

阐述了汽油蒸汽回收的重要意义,介绍了吸附法、吸收法、冷凝法及膜分离法等油气回收技术的原理和应用。     

水蒸气透过率、透过量与透过系数的应用

详细介绍了3项透湿性参数——水蒸气透过率、透过量和透过系数的定义、应用范围以及相互之间的差异和换算关系,同时对于目前国际国内标准中定义不清晰的情况给予了说明。     

气相结晶技术模型在合成氟化氢铵工艺中的应用

研究了氟化氢铵气相合成新工艺,应用气相结晶理论验证了气相结晶过程,拟舍得到了适合于该过程的气相结晶模型,确定了颗粒平均粒径和流体流速之间的关系。并通过实验来验证了该气相结晶技术模型的正确性。通过实验确定了优化反应条件：反应温度为250℃,冷却器温度控制在80℃,反应物进料配比为NH3：HF=0．75：2,氨气流量为0．04m^3/h载气流量为0．6m^3/h。氟化氢铵含量达99．5％。     

DRYING OF POROUS MATERIALS AT LOW MOISTURE CONTENT

ABSTRACT

Drying experiments were conducted using packed beds of glass beads with initial moisture content near or slightly above the irreducible moisture content. The objective was to validate the vapor phase diffusion coefficient determined in earlier experiments and to quantify the effect of temperature gradient on vapor phase diffusion in the presence of irreducible saturation. The resulls indicate that for isothermal drying the enhancement factor, β, which is the ratio of the diffusion coefficient in the packed bed to that in free space, is slightly less than unity. This is consistent with previous results. However, the results for non-isothermal drying show little effect of temperature gradient for temperature gradients either assisting the concentration gradient or opposing the concentration gradient. This is contrary to the traditional thinking about enhanced vapor diffusion originally proposed by Philip and deVries (1957).     

不同蒸气压力下Marangoni凝结换热特性

在蒸气流速4 m·s^-1的条件下,通过实验研究了不同蒸气压力下纯水、纯酒精和不同酒精浓度水-酒精混合蒸气沿重力方向流过竖直铜平板表面上的凝结换热特性,并实现了实验的可视化,同时从理论上初步分析了混合蒸气压力对Marangoni凝结换热特性的影响.实验及理论分析结果表明,在相同蒸气浓度、蒸气流速和表面过冷度条件下,高压下的凝结换热强度比低压的大.且蒸气压力对凝结换热的影响因混合蒸气酒精浓度的不同而不同,在低浓度1%、2.28%和高浓度22%、51%时压力的增加对凝结换热特性的影响较小,而在中间浓度5.1%和9.8%时凝结换热系数随压力的增加明显.     

尿素水解系统波动分析

化肥厂采用的是斯塔米卡邦(Stamicarbon)公司的尿素水解、解吸技术,自2011年4月中旬以来,水解出现了频繁的波动。本文首先简要介绍水解与解析原理,通过水解波动各种现象与数据分析各种可能的波动原因。并提出几点建议。     

Analysis of a mechanical vapor compression desalination system

The mechanical vapor compression (MVC) desalination system is based on distillation of seawater. The system is basically a heat exchanger that is an evaporator/condenser. The heat required to evaporate water which flows on one side of a heat transfer surface is supplied through the simultaneous condensation of the distillate-producing vapor on the other side of the surface. That is, the latent heat is exchanged in the evaporation—condensation process within the system. A compressor is the driving force for this heat transfer and provides the energy required separating the solution and overcoming dynamic pressure losses and other irreversibilities. In this study, the operation characteristics of a low-temperature MVC desalination system are investigated. In the modeling, the overall energy balance and mass balance equations and LMTD method for heat transfer are used. The tube diameter and the tube length were taken at 0.025 m and 9 m, respectively. The main dependent parameters, the compressor work and the mass flow rate of the distilled water, were investigated against the independent parameters, the evaporation side pressure, the condensation side pressure, and the water inlet temperature.     

Textures of pyrolytic carbon formed in the chemical vapor infiltration of capillaries

Capillaries, 1.1 mm in diameter and 17.0 or 32.5 mm in length, were infiltrated at a temperature of 1100 °C and methane pressures from 5 to 30 kPa. Layer thickness and carbon texture were determined at cross-sections of 2, 16 and 32 mm from the open end of the capillaries using polarized light microscopy. Average deposition rates, determined from layer thickness and infiltration time, as a function of methane pressure indicate a rate increase up to a saturation adsorption at pressures between 10 and 15 kPa (range 1) and a strong rate increase above these pressures (range 2). This result implies carbon formations based on the growth mechanism in range 1 and the nucleation mechanism in range 2. The carbon texture shows a maximum in range 1 and a minimum in the transition from range 1 to range 2 followed by a clear increase in range 2. The maximum in range 1 corresponds to the particle-filler model describing formation of various textures of carbon by the ratio of aromatic species to C₂ species. Increasing texture degrees in range 2 suggest that the nucleation mechanism may lead to high textured carbon provided that the residence time for intramolecular rearrangments of polycyclic aromatic hydrocarbons is sufficient.     

混合流体饱和汽相体积的测定与计算

用作者建立的实验装置测定了二氧化碳－丙酮、二氧化碳－乙醚、二氧化碳－二氯甲烷三个二元体系露点压力下的饱和汽相体积和Ｐ，Ｔ，ｙ数据，测定结果用修正的ＰＲ状态方程进行了关联。     

Water‐vapor‐permeable polyurethane resin

The reaction of methylene diphenylene diisocyanate with ethylene glycol, dimethyl dimethoxysilane, dimethyl diethyloxysilene, and other additives in the presence of N,N‐dimethylformamide and toluene to form the structure of water‐vapor‐permeable polyurethane (PU) resin was proven with Fourier transform infrared spectra. Experimental results clearly showed that the amount of oxygen that permeated the film made with the PU resin increased with an increase in the concentration of ethylene glycol, diethylene glycol, or triethylene glycol. This was due to an increased number of hydrophilic groups attached to the backbone of the PU resin molecules. These hydrophilic groups, because of the intermolecular interactions between PU resin molecules, made PU resin molecules form an expanded conformation with large porosities. Interestingly, the water vapor permeability of the PU resin appeared to increase with an increasing concentration of ethylene glycol, dimethyl dimethoxysilane, or dimethyl diethoxysilane but not to increase with an increasing concentration of diethylene glycol, triethylene glycol, or poly(ethylene glycol) with dimethyl dimethoxysilane. The former was due to intermolecular interactions resulting in an expanded conformation with large porosities, but the latter was due to intramolecular interactions resulting in a compact conformation or a micellelike structure with small porosities. Therefore, the water vapor permeability of the former increased, but the latter remained unchanged or decreased. Our experimental results suggest that the use of poly(ethylene glycol) 400, ethylene glycol, dimethyl dimethoxysilane, and other strong hydrophilic compound in the preparation of modified PU resins substantially raises the amount of water vapor diffusing into films made with these resins. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2002–2010, 2002