The activity of commercial water gas shift catalysts

Published kinetic data for commercial water gas shift catalysts are interpreted in terms of pore diffusional effects. The Arrhenius plots of apparent activity show the curvature typical of the transition from reaction to pore diffusion control and the apparent activities of different catalyst pellets vary quite widely. Effective diffusivity data are used to calculate intrinsic rate constants from the apparent activity data and it is found that the intrinsic activities of the catalysts considered are all similar. Furthermore the intrinsic activities, calculated in this way, give linear Arrhenius plots and activation energies which are in good agreement with values obtained experimentally using small catalyst particles (22–27 K. Cals). The effect of pressure on apparent catalyst activity is also discussed and it is shown that this effect may be accounted for satisfactorily by pore diffusional effects and it is not necessary to assume a change in the intrinsic rate equation at least at pressures below 20 atms.     

Experimental investigation and numerical analysis of the dynamic characteristics of a laminated hybrid composite bed

To maximize the productivity of precise products in manufacturing industries, machine tools should be operated at high speeds. The machine tools should withstand higher cutting speeds, higher acceleration and deceleration and should be cost effective to give high quality products. The aforesaid expectations cannot be fulfilled simultaneously if conventional metal such as cast iron is employed. Hence, there is a need to replace cast iron with alternative materials. In the present work an attempt is made to replace the mini lathe bed made of cast iron with laminated hybrid composites, carbon, and glass/epoxy, to attain superior dynamic properties with less weight. The manufactured composite bed weighs 3.5 times less than that of the existing cast iron bed. Numerical and experimental modal analysis was done for both the cast iron and composite bed. The results show that the experimentally obtained fundamental natural frequency and damping ratio of composite bed are superior, 37% and 3 times, than that of the existing cast iron bed. POLYM. COMPOS., 38:20–26, 2017. © 2015 Society of Plastics Engineers     

异常高压气藏动态预测研究

在异常高压气藏开发过程中,由于应力敏感性造成的渗透率变化无法忽略,因此在建立二项式渗流方程时必须考虑由于应力敏感性造成的渗透率的变化情况,定义新的拟压力形式的渗流方程。再以物质平衡原理为基础,导出定容异常高压气藏的压降方程,并与井筒流动方程相结合,建立动态预测模型。由于该模型很好的考虑到了应力敏感性造成的影响,使得更适用于实际生产过程中,对于异常高压气藏生产动态的预测有较好的效果。     

浮头式废热锅炉转化气流动特性的试验研究

通过大比例尺模型试验，测定了浮头式废热锅炉的环室、分配套筒和辐射状横掠管束的转化气沿轴向和环向流动的不均匀性。分析了造成流动不均匀性的原因及对传热的影响，给出了改进分配套筒多孔结构的方法，为大型合成氨厂的浮头式废热锅炉的设计和改造提供了试验依据。     

Effects of tar model compounds on commercial water gas shift catalysts

One attractive application of the catalytic water gas shift (WGS) reaction is the production of a syn-gas with high hydrogen concentration from gasification of solid combustibles. The catalyst's behavior can be affected by the hydrocarbons with high molecular weight (tar) still present in the gas after its purification. In this work the effect of some tar model compounds on two typical commercial WGS catalysts were investigated. A low temperature catalyst composed of Cu/Zn/Al and a high temperature catalyst based mainly on Fe and Cr were tested. N-hexadecane, fluorene, phenol, and octanol were used as tar model compounds. Besides these compounds, the effect of biodiesel was also investigated. In all cases a concentration of 0.5 g/Nm³ was used. Generally it was observed that a low concentration is often sufficient to produce a rapid deactivation. Catalysts were characterized by means of BET and XRD.     

Experimental and numerical investigation of supported rhodium catalysts for partial oxidation of methane in exhaust gas diluted reaction mixtures

The partial oxidation of methane/oxygen mixtures with large exhaust gas dilution (46.3 vol% H₂O and 23.1 vol% CO₂) has been investigated experimentally and numerically over Rh/CeO₂-ZrO₂, Rh/ZrO₂ and Rh/α-Al₂O₃ catalysts. Experiments were carried out in a short-contact-time reactor at 5 bar and included exhaust gas analysis, temperature measurements along the reactor, and catalyst characterization. Additional experiments were performed in an optically accessible channel-flow reactor and involved in situ Raman measurements of major gas-phase species concentrations over the catalyst boundary layer and laser-induced fluorescence (LIF) of formaldehyde. A full elliptic two-dimensional numerical code that included elementary hetero-/homogeneous chemical reaction schemes and relevant heat transfer mechanisms in the solid was used in the simulations. The employed heterogeneous reaction mechanism, including only active Rh sites, reproduced the experiments with good accuracy. The ratio of active to geometrical surface area, deduced from hydrogen chemisorption measurements, was the single model parameter needed to account for the effect of different supports. This indicated that water activation occurring on support sites, resulting in inverse OH spillover from the support to the noble metal sites, could be neglected under the present conditions with high water dilution. An evident relationship between noble metal dispersion and catalytic behavior, in terms of methane conversion and synthesis gas yields, could be established. Both measurements and predictions indicated that an increasing Rh dispersion (in the order Rh/α-Al₂O₃, Rh/ZrO₂, and Rh/CeO₂-ZrO₂) resulted in higher methane conversions, lower surface temperatures, and higher synthesis gas yields.     

Experimental investigation of gas combustion regularities in narrow tubes

Combustion wave propagation in flowing combustible gas has been studied experimentally in tubes with inner diameters larger and smaller than the critical diameters. Combustion wave velocity has been shown to depend on the material of the tube walls, the tube inner diameter, the mixture composition, and the gas flow rate. In a tube which has an inner diameter larger than the critical diameter, two flame-propagation regimes exist.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 1, pp. 42–47, January–February, 1996.     

用于机动车排气净化的含Pd催化剂初步研究

本文制备出一种含Pd催化剂,用于治理机动车排气中的CO、HC和NOx的排放,初步研究了其催化效果,包括空燃比特性和温度特性。实验结果表明,该催化剂具有较好的催化能力。     

商用蜂窝式SCR催化剂脱除NO_x试验研究

为了评价燃煤电厂广泛采用的选择性催化还原工艺对不同形态NO_x的脱除效果,以某商用蜂窝式SCR催化剂为例,在SCR脱硝试验装置上研究了氧量、温度、空速、氨氮摩尔比等反应条件对NO、N_2O和NO_2脱除过程的影响。结果表明,氧量可以促进NO氧化以及NO与氨的催化还原反应;高温可以促进NO的脱除和氨气氧化为N_2O;空速升高会导致NO脱除率先升高后降低;氨氮摩尔比提高在促进NO脱除的同时会增加氨逃逸;与NO_2可以完全脱除相反,N_2O与氨气不发生反应。因此,为真正实现NO_x的超净排放,应适当控制锅炉运行参数避免N_2O的生成。     

Progress towards the commercial application of gold catalysts

Now that gold catalysis is a valuable and exciting new field of catalysis as a whole, the exploitation of gold catalysts for commercial applications is being pursued. This is being assisted by new work on preparation and utilization methods to increase their durability during use. Other factors, including a substantial increase in investment in gold catalysis R&D, need to be considered before widespread application will occur. We show that new opportunities for commercial exploitation can be monitored via patent mapping, followed by careful examination of key patents.     

尿素水溶液液滴的蒸发特性

在石英管式炉上通过挂滴法来观察单个尿素水溶液（urea-aqueous-solution,UAS）液滴的具体蒸发过程,比较了不同环境温度以及不同初始直径大小下液滴的蒸发特性。结果表明,尿素溶液液滴在100～1300 ℃的温度范围内呈现出了不同的蒸发行为。在较高的温度下,液滴的蒸发行为较为复杂,如气泡的产生、液滴的变形以及发生微爆的现象;但是,随着环境温度的降低,这些现象就变得非常微弱甚至消失。同时,还定量分析了稳态蒸发常数与温度、液滴初始直径之间的变化关系,发现在初始直径为2.5 mm、温度在100～600 ℃之间变化的情况下,稳态蒸发常数从0.02075 mm2/s增加到了0.23953 mm2/s,增大了10倍左右。此外,还对气流流速为0.25～1.25 m/s范围内的液滴蒸发特性作了实验研究。当液滴周围有强迫气流存在时,液滴与气体间的换热方式由导热转变为对流换热,从而增强了液滴表面的传热传质能力,促进了液滴的蒸发。     

An experimental study of the expansion characteristics of gas fluidized beds of fine catalysts

Experimental tests have been carried out on four commercial fine catalysts fluidized by three different gases to characterize the particulate expansion range, the minimum bubbling point, the dense-phase permeability and bubble hold-up in the aggregate regime.The results provide answers to some practical questions regarding the applicability of a recently proposed model of the fluidized state (the ‘particle bed model’) which offers a comprehensive fluid dynamic interpretation of gas and liquid fluidization.     

氧化锌法处理低浓度SO2烟气的试验研究和生产实践

论述用氧化锌法处理低浓度SO2气体的基本原理、试验研究和生产实践。采用pH值约5的氧化锌浆液吸收气体中的SO2，然后用硫酸分解或蒸汽加热分解产生的亚硫酸锌，获得高浓度SO2和氧化锌或硫酸锌，SO2和氧化锌重新使用，硫酸锌作为副产品。试验及生产实践均证明，氧化锌法吸收效率高、流程简单，由于原料容易获得，特别适合于铅锌冶炼厂低浓度SO2烟气或硫酸装置尾气的处理。     

双切环流气体分布器性能的实验研究

湿空气透平(HAT)循环被誉为21世纪最有竞争力的先进动力循环,HAT循环的核心部件饱和器采用了填料塔的结构形式,为了提高整塔的性能,改进并设计了双切环流气体分布器.目前,双切环流气体分布器设计依然主要依靠经验进行设计,而实验的方法依然是分布器性能最可靠的研究方法.文中利用直径φ800 mm的饱和器实验台,对改进后的双...     

Two-phase flow through pressure safety valves. Experimental investigation and model prediction

Due to the lack of experimental data regarding two-phase flow through safety relief valves, a number of different calculation methods are presently available in the literature for their sizing. All these models mainly refer to the flow through an ideal nozzle, so that, in order to match the measured values, a discharge coefficient is to be introduced in the calculation, the coefficient thus depending on the model adopted. Furthermore, most of the available data are referred to a few operating conditions. As a result, none of the available models is presently considered sufficiently accurate to be used in a wide range of operating conditions.In the present paper, new data are produced on a steam/water flashing system through a real valve with different values of the main operating parameters (vapour quality, inlet pressure, mass flow rate, and backpressure). The measurements are compared with the predictions of a commonly used homogeneous equilibrium model (HEM), the so-called ω method, and show that the model markedly underestimates the mass flow rate in the whole range of conditions investigated. This unexpectedly implies the introduction of a two-phase discharge coefficient much higher than the vapour coefficient.Finally, a new correlation for the discharge coefficient as a function of the main operating parameters is proposed.     

板式换热器以松花江水为冷却水条件下的污垢特性

为研究板式换热器在天然水下的污垢特性,实验采用BR0.015F型板式换热器,研究了其在不同的流速和温度下的污垢特性,用扫描电镜观察了已经结垢的换热表面。结果表明：此板式换热器松花江水的污垢类型为渐进型且不存在诱导期,随着流速的增大污垢热阻降低的幅度减小。冷却水温度在27.5～28.5 ℃时污垢热阻较大,温度升高污垢热阻降低;换热表面的混合污垢成片的附着于换热面,有少量的难溶盐析出的晶体生成。     

弓形折流板换热器动态特性试验研究

建立了可进行壳管式换热器动态特性试验研究系统,通过试验研究的方法对以水-油为换热工质的弓形折流板换热器动态特性进行了试验研究,进口流量扰动为等百分比流量特性.研究了四种流量扰动方式下水和油出口温度的动态响应.同时研究了在一定Re数下,异侧不同的流体扰动量对换热器进出口温升的影响.实验表明液液换热系统温度的动态响应时间比较长,在正负的流量扰动下,弓形折流板换热器进出口温度变化呈现线性变化,进出口温升在正负流量扰动下其变化趋势具有对称特征.     

Experimental investigation of particle contact time at the wall of gas fluidized beds

The contact time of particles at the walls of gas fluidized beds has been studied using a radioactive particle tracking technique to monitor the position of a radioactive tracer. The solids used were sand or FCC particles fluidized by air at room temperature and atmospheric pressure at various superficial velocities, covering both bubbling and turbulent regimes of fluidization. Based on the analysis of tracer positions, the motion of individual particles near the walls of the fluidized bed was studied. The contact time, contact distance and contact frequency of the particles at the wall were evaluated from these experimental data. It was found that in a bed of sand particles, the mean wall contact time of the fluidized bed of sand particles decreases by increasing the gas velocity in the bubbling and increases in the turbulent fluidization. In other words, the particle-wall contact time is minimum at the onset of turbulent fluidization in the bed of sand particles. However, the mean wall contact time is almost constant in both regimes of fluidization in the bed of FCC particles. All the existing models in the literature predict a decreasing contact time when the gas velocity in the bed is increased. It was also shown that the contact distance increases monotonously by increasing the gas velocity in the bed of sand particles, while it is almost constant for the bed of FCC particles. Contact frequency has a trend similar to that of the contact time for both sand and FCC particles.