Combined static mixers for high viscous fluids mixing

A new static mixer Cross-over-Disc has been invented to strip off the boundary layer and to make strong radial mixing. The pressure drop of Cross-over-Disc is 12-26 times as large as that of empty pipe with equivalent diameter and length. The mixing performance of Cross-over-Disc with 14 elements has been investigated in the viscosity range of 190–250 Pa·s by decoloration method, and the gray analysis of images shows that mixing inhomogeneity is about 7.5% and 9.4% for the mixing ratio of 5:1 and 10:1, respectively. Furthermore, mixing inhomogeneity for a combination of static mixing elements (four from Cross-over-Disc and three pairs from Sulzer-type) can be decreased to 2.1%–3.1% within a reasonable range of pressure drop.     

Comparative analysis of different static mixers performance by CFD technique: An innovative mixer

The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD,with Reynolds numbers ranging from 20 to 160. The performance of the new mixer is compared with those of Kenics, SMX, and Komax static mixers. The pressure drop ratio(Z-factor), coefficient of variation(CoV), and extensional efficiency(α) features have been used to evaluate power consumption, distributive mixing, and dispersive mixing performances, respectively, in all mixers. The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation. CFD results are consistent with measured data and those obtained by available correlations in the literature. The new mixer shows a superior mixing performance compared to the other mixers.     

The numerical simulation of a new double swirl static mixer for gas reactants mixing

For the nitrogen oxide removal processes, high performance gas mixer is deeply needed for the injection of NH₃ or O₃. In this study, a new type of double swirl static mixer in gas mixing was investigated using computational fluid dynamics (CFD). The results obtained using Particle Image Velocimetry (PIV) correlated well with the results obtained from simulation. The comparisons in pressure loss between the experimental results and the simulation results showed that the model was suitable and accurate for the simulation of the static mixer. Optimal process conditions and design were investigated. When L/D equaled 4, coefficient of variation (COV) was < 5%. The inlet velocity did not affect the distributions of turbulent kinetic energy. In terms of both COV and pressure loss, the inner connector is important in the design of the static mixer. The nozzle length should be set at 4 cm. Taking both COV and pressure loss into consideration, the optimal oblique degree is 45°. The averaged kinetic energy changed according to process conditions and design. The new static mixer resulted in improved mixing performance in a more compact design. The new static mixer is more energy efficient compared with other SV static mixers. Therefore, the double swirl static mixer is promising in gas mixing.     

A general correlation for pressure drop in a Kenics static mixer

A new pressure drop correlation in a Kenics static mixer has been developed. Pressure drop data were generated from computational fluid dynamics (CFD) calculations, avoiding the experimental limitations in obtaining comprehensive data enough for developing a reliable pressure drop correlation. Dimensional analysis reveals that the pressure drop characteristic of the Kenics static mixer can be described by three dimensionless groups, i.e., the friction factor, Reynolds number (Re), and aspect ratio of a mixing element (AR). A systematic graphical analysis led to a single master curve governing the pressure drop behavior of the Kenics static mixer, which had never been achieved before. We derived a pressure drop correlation fitting well with the obtained master curve in a general form into which the AR effect on the pressure drop is directly incorporated. Unlike the already existing correlations available in the literature, the correlation proposed in this study can cover the whole range of Re from laminar to turbulence. The reliability of the proposed correlation was validated by the comparison with various pressure drop data reported in the literature.     

Scaling inline static mixers for flocculation of oil sand mature fine tailings

Operations to reclaim mature fine tailings (MFT) ponds involve flocculation using high‐molecular‐weight polymers, for which inline static mixers are suited. Three different commercial static mixers were utilized to determine mixing parameters corresponding to optimal dewatering performance of flocculated MFT. MFT was treated with polymer solution under different mixing conditions. The dewatering rates passed through a peak with increasing mean velocity, V and Reynolds number, Re of the fluid. The greater the number of mixer elements, the lower the V and Re at which the peak dewatering rate occurred. Mixing parameters such as G‐value, residence time, and mixing energy dissipation rate of the most rapidly dewatering flocculated MFT were dependent on mixer type and setup. In contrast, peak dewatering rates converged when scaled with respect to specific mixing energy, E, demonstrating that E is a suitable scale‐up parameter for inline static mixing to produce optimally dewatering MFT. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4402–4411, 2015     

Modelling the liquid-phase adsorption in packed beds at low Reynolds numbers: An improved hydrodynamic model

A hydrodynamic model including only one parameter (λ_O) for the prediction of both axial dispersion and external mass transfer in fixed-bed adsorbers at low Reynolds numbers (creeping flow regime) has been developed. The theoretical analysis is based on the application of the (two-dimensional) uniform dispersion model originally proposed by Bischoff and Levenspiel [1962a. Fluid dispersion—generalization and comparison of mathematical models—I. Generalization of models. Chemical Engineering Science 17, 245-255] to the representative capillary of a tube bundle model for describing the flow and mixing behaviour in packed beds. The combination of this model with the relationship between longitudinal and radial dispersion leads to the definition of the sole hydrodynamic parameter λ_O (one-parameter hydrodynamic model). Furthermore, the detailed investigation reveals that the one-parameter concept may be utilized for the application of the (one-dimensional) axial dispersed plug flow model as well. The functional dependence of the parameter λ_O on the flow conditions is elaborated from axial dispersion measurements. Both the new (one-parameter) hydrodynamic model and the classical model including axial dispersion and external mass transfer coefficients (two-parameter model) are utilized to simulate the breakthrough curves for the adsorption of naphthalene onto silica gel. This simulation study reveals that only the one-parameter hydrodynamic model is able to predict the adsorber dynamics over a large range of flow rates.     

含CO_2体系高压相平衡测定和关联

测定了ＣＯ２－Ｃ２Ｈ５ＯＨ和ＣＯ２－Ｈ２Ｏ体系的高压汽液平衡数据，并采用ＥＯＳ／ＧＥ模型推导出局部组成混合规则，用ＳＲＫ方程关联结果与实验值符合较好。     

Spalling and pore pressure in HPC at high temperatures

High-performance concrete (HPC) are subject to spalling under certain thermal and mechanical conditions. Spalling results mainly from two processes: a “thermo-mechanical” process in which the stress originates in the gradients of thermal deformation within the material, and a thermo-hydral process where spalling is due to the build-up of gas pressure fields in the porous network. This paper deals with the thermo-hydral process. An original device was designed in order to make simultaneous measurements of pressure and temperature at various positions in a concrete specimen (30×30×12 cm³) heated on one face up to 800°C. The specimen was also continuously weighed during the tests, thus, the mass loss, resulting mainly from water transport and loss, was recorded. This campaign was carried out on an ordinary concrete (OC) and a HPC (90 MPa). As expected, the pressure peaks were much higher than in HPC (40 bars) than in OC (20 bars). In HPC, these pressures exceeded the saturated vapor pressure. It is demonstrated that the thermal expansion of liquid water and the transport of water towards the inner part of the specimen play a significant role on the build-up of gas pressure. The experimental correlation between the pressure peaks and the plateau in the temperature curves confirmed the hypothesis that the drying front is preceded by a quasi-saturated layer that acts as a moisture clog.     

利用LNG冷能的轻烃分离高压流程

利用LNG冷能能以较低的能耗分离回收其中高附加值的C₂⁺轻烃资源,同时实现LNG气化,是LNG冷能利用的有效方式。本文提出一种新型的利用LNG冷能的轻烃分离流程,脱甲烷塔在较高的压力下运行,从而分离出的富甲烷天然气能以较低能耗压缩到管输压力;脱乙烷塔在常压下运行,可以直接得到常压液态乙烷及LPG产品,方便产品的储运。脱甲烷塔中再沸器的热耗由燃气提供,经计算只需消耗1%左右的天然气;脱乙烷塔中冷凝器所需的冷量由LNG提供。该流程轻烃回收率可达90%以上,其中乙烷回收率可达85%左右。以某气源组分为基础,考察了乙烷含量和乙烷价格变化对装置经济性的影响,结果表明,使用该流程进行轻烃回收效益可观。     

The effects of pressure and temperature on the catalytic oxidation of hydrogen sulfide in natural gas and regeneration of the catalyst to recover the sulfur produced

The influence of pressure up to 5600 kPa and temperature up to 175 °C on the oxidation of low concentrations of H₂S in natural gas was studied in a fixed bed reactor over an activated carbon catalyst. Operation of this system at 5600 kPa provides higher catalyst activity (virtually 100% H₂S conversion) over a longer period of time and with lower selectivity to SO₂ than when operated at atmospheric pressure. The desorption of sulfur from a loaded catalyst occurs first from the macropores (> 100 nm) of the catalyst which contain a substantial portion of the sulfur load and then from the micropores (< 100 nm). This study also indicated that the sulfur recovery process is both rapid and effective at 327°C.     

A high pressure solubility apparatus for gases of high solubility

An apparatus is described for measuring gas solubilities at high pressure for gases of moderate to high solubility. Solvent, supplied by a metering pump, is continuously saturated with gas as it flows down a spiral rod. Gas is continuously supplied by means of a calibrated piston pump to provide a constant pressure. The solubility is determined from the relation between the solvent rate and the gas consumption required to achieve saturation. The solubilities of two chemically reactive gases, propene and isobutene, are reported for the solvents n-butanol, chlorobenzene and n-octane for three temperaturres, 298, 323 and 343 K, and a range of pressures from 0.2 to 1.9 MPa.     

层流状态下高压高转速二氧化碳干气密封的惯性效应分析

借鉴考虑惯性效应的气体止推轴承理论,以维里三项截断式描述二氧化碳的实际气体行为,同时考虑阻塞流效应和密封端面间气膜的黏度变化,采用有限差分法分别分析了层流状态下惯性效应对泵入式、泵出式螺旋槽干气密封稳态性能的影响规律,并与理想气体无惯性假设模型的计算结果进行了对比。结果表明：与理想气体相比,惯性效应对二氧化碳实际气体干气密封性能的影响程度更高。惯性效应使泵入式螺旋槽干气密封泄漏率和开启力均减小,而对泵出式螺旋槽干气密封的影响程度恰好相反。以泵入式螺旋槽干气密封为例,惯性效应对二氧化碳干气密封性能（泄漏率、开启力）的影响分别随密封压力和转速的增大而增强,随气膜厚度的增大而减小,密封压力为10 MPa,气膜厚度为3 μm,转速为20000 r·min^-1时,惯性效应使泄漏率降低62.21%,开启力降低35.03%,使二氧化碳泵入式螺旋槽干气密封发生阻塞流动的临界进口压力提高。此外,二氧化碳的温度越接近其临界温度,惯性效应表现得越明显。     

Gas holdup in a two-phase vertical tubular reactor at high pressure

Gas holdup in a tubular reactor was measured at pressures from 5 to 14 MPa at 300°C using a differential pressure cell. The effects on gas holdup of gas density, liquid superficial velocity and gas superficial velocity were studied using vacuum tower bottoms from a Venezuelan feedstock with 95.1 wt% +524°C material. Hydrogen was used at superficial gas velocities from 0.7 to 2.0 cm/s. The feed density at 15°C (0.1 MPa), 300°C (5.57 MPa) and 400°C (13.9 MPa) was measured and showed a linear decrease with temperature. Increased gas density at a constant temperature of 300°C increased the gas holdup at all superficial gas velocities. An increase in the liquid flow rate from about 0.04 to 0.1 cm/s did not affect the gas holdup.     

N_2，H_2，Ar在正辛醇中高压溶解度的测定

测定了温度范围在０～４５℃，压力达到８４．６×１０￣５ｐａ时，Ｎ＿２，Ｈ＿２，Ａｒ在正辛醇中的７５点高压气体溶解度数据，并提出一个由高压实验数据回归常压溶解度的方法。     

Supported palladium-platinum catalyst for methane combustion at high pressure

Catalytic combustion of methane over a supported bimetallic Pd-Pt catalyst and a monometallic Pd catalyst has been investigated experimentally. Two different reactor configurations were used in the study, i.e. a tubular lab-scale reactor working at atmospheric pressure and a high-pressure reactor working at up to 15 bar. The results showed that the bimetallic catalyst has a clearly more stable activity during steady-state operation compare to the palladium only catalyst. The activity of the bimetallic catalyst was slightly higher than for the palladium catalyst. These results were established in both test facilities. Further, the impact of pressure on the combustion activity has been studied experimentally. The tests showed that the methane conversion decreases with increasing pressure. However, the impact of pressure is more prominent at lower pressures and levels out for pressures above 10 bar.     

Extraction of ethane from natural gas at high pressure by adsorption on Na-ETS-10

Methane/ethane separation was achieved using Na-ETS-10 as a packed-bed adsorbent over a pressure range of 450–5600 kPa at 298 K. At these pressures, pure methane gas raffinate streams were obtained prior to ethane breakthrough. The extract phase obtained following desorption from the packed-bed column was enriched in ethane. Extract phases containing up to 75% ethane were achieved following separations of a 93/7 methane/ethane feed mixture. Separation performance did not deteriorate as adsorption column pressures increased. Selective adsorption of a synthetic natural gas mixture using an Na-ETS-10 packed-bed column resulted in hydrocarbon outlet compositions ranging from pure methane (up to ∼60 bed volumes at standard temperature and pressure) to ∼93% methane, ∼5% ethane and ∼2% propane (∼150 to ∼850 bed volumes at standard temperature and pressure). In all cases, following desorption, the extract phase was highly enriched in the larger and more valuable hydrocarbons.     

An improved two layer model for horizontal slurry pipeline flow

A model for predicting head losses for coarse-particle or settling slurries has been obtained. Experimental data for isothermal flows of sand, gravel and coarse coal slurries in pipes of industrial scale have been used to obtain the correlations in the model. The model differs from previous versions in the way it deals with the concentration of the lower layer and in the role ascribed to the finest (–74 μm) particles. The fraction of contact load, which contributes sliding friction at the pipe wall, is found to be primarily a function of the ratio of the mean flow velocity to the settling velocity of the mass median particle size in the (+74 μm) fraction. The correlations are restricted to mixtures containing less than 35% (+ 74 μm) particles by volume.     

Measurements and correlations for gas liquid surface tension at high pressure and high temperature

Surface tension of water/nitrogen and water–phenol/nitrogen systems was successfully measured by the hanging drop method in a wide domain of temperature (from 100 to 300°C) and pressure (from 4 to 30MPa), conditions little explored in litterature. Results show that surface tension of water–phenol mixtures decreases as phenol mass fraction increases. This decrease is observed under saturated and unsaturated conditions and is more pronounced at low temperatures and does not seem to depend on pressure. The effect of saturation on surface tension in the water/nitrogen system has been correlated with water vapor pressure by using experimental points with a great accuracy. For the water–phenol/nitrogen system, experimental data obtained with different mass fraction of phenol were correlated using Macleod‐Sugden equation for mixtures. © 2018 American Institute of Chemical Engineers © 2018 American Institute of Chemical Engineers AIChE J, 64: 4110–4117, 2018     

An improved method for preparing monolithic aerogels based on methyltrimethoxysilane at ambient pressure Part II: Microstructure and performance of the aerogels

The microstructures, physical properties and mechanical properties of the methyltrimethoxysilane (MTMS) derived aerogels, prepared at ambient pressure using an improved method reported in Part I, have been comprehensively characterised in this paper, as Part II. The study has revealed sophisticated pore structures and morphologies of the aerogels produced, and demonstrated the relationships between the key processing conditions and microstructures of the resultant aerogels. The results of the study also help to further understand the effect of microstructure changes on the macrostructure, volume shrinkage and performances of the aerogels, and provide a general guide on how to manipulate the processing conditions to produce monolithic MTMS based aerogels with desirable structure and properties by ambient pressure drying.