Effect of the mechanical failure of catalyst pellets on the pressure drop of a reactor

The effect of the mechanical failure of catalyst pellets on the pressure drop across a laboratory-scale catalyst packing has been examined by experiment. Results reveal that, along with the mechanical failure of the pellets, there exists a point of maximum curvature around which the slope of pressure drop increases rapidly. This rapid increase is attributed to a mutation of the packing structure, occurring as the amount of failed pellets reaches a certain critical value. The secondary breakage of the pellets contributes much to the mutation of the packing and to the pressure drop. It has been observed that a trilobite catalyst is more susceptible to a mechanical stress than a cylindrical catalyst, and that a catalyst with a smaller diameter is much easier to result in an increase in the pressure drop. The measurement of the pressure drop across a laboratory-scale catalyst packing as the failure of pellets under a mechanical stress has a satisfactory reproducibility, and has a close meaning to the mechanical reliability of a fixed bed converter, and hence is recommended as a method for catalyst assessment. The multi-scale and multi-disciplinary nature of catalyst mechanical reliability is also discussed.     

Theory of yield of cohesive powders

In many problems in process technology, the influence of the adhesion forces on the mechanics of fine powders plays a considerable role. The existing knowledge is characterized by intensive experimental and theoretical investigations into the mechanism of adhesion for single particle contacts without consolidation by external forces. On the other hand, the mechanical behaviour of cohesive powders has been investigated mainly on the basis of continuum mechanics.For science and technology, it is useful to combine the particles approach and the continuum approach in order to provide a better understanding of the mechanical properties of cohesive powders. A theoretical model has therefore been developed which takes into account the forces acting in interparticle contacts. The theory especially considers the increase in the adhesion forces transmitted in interparticle contacts with increasing consolidation. Contrary to the commonly used phenomenological view, this theory yields a physically based understanding of the effective yield locus for steady-state flow which is reduced to material properties of the solid particles and is therefore shown to be an invariant of a respective powder.The opinion found in the literature that a single yield locus uniquely belongs to one consolidation locus is shown to be not valid. The microstructural view of a cohesive powder is able to show that, contrary to the continuum mechanical view, in the general case a cohesive powder is mechanically anisotropic due to its loading history.     

过碳酸钠洗涤性能和稳定性能影响因素的研究

过碳酸钠 (PC)是一种碳酸钠与过氧化氢的络合物 ,其特点是对环境无污染。作者以洗涤剂中含有过碳酸钠为前提 ,从洗涤剂最常见的原料对PC的活性与稳定性能的影响方面进行了研究 ,通过实验证明Na2 CO3 、Na2 SO4 、十二烷基苯磺酸钠 (LAS)、三聚磷酸钠 (STPP)、MgSO4 、Na2 SiO3 、四乙酰乙二胺 (TAED)对PC的活性和稳定性都有影响。发现Na2 CO3 对过碳酸钠漂白的促进作用在过碳酸钠质量浓度低的时候尤其明显 ;随着Na2 SO4 、LAS用量的增加 ,白度值上升 ,在达到一定值后白度下降 ;而STPP恰恰相反 ,质量浓度增大 ,白度增大 ,当STPP质量浓度达到一定值时 ,作用反而更显著 ;MgSO4 很敏感 ,在窄区间有一峰值 ;Na2 SiO3 的用量在 2 5 %以内时 ,白度升高的趋势很强 ;TAED对PC起活化作用且和温度有关。最后设计出一个配方与标准粉比较去污比值是 2 2 1。     

Foam separation of complexed cyanide: Studies of rate and of pulsed addition of surfactant

An experimental investigation is presented of the foam separation of cyanide complexed with ferrous iron, using a cationic surfactant, ethylhexadecyldimethylammonium bromide. With a 25 min. foaming time, an initial iron to total cyanide ratio of 0·351:1 and an initial surfactant to complexed cyanide ratio of about 0·34:1 suspensions containing from 1·54 to 3·08 mM total cyanide can be reduced to about 0·11 mM in complexed cyanide and 0·29 mM in non-complexed cyanide. The rate of surfactant removal was satisfied by a first-order relationship, similar to that obtained with colloidal ferric oxide. The rate of complexed cyanide removal was satisfied by a reversible, approximately first-order relationship eliminating the residual surfactant concentration. The pulsed addition of surfactant in three dosages during the course of an experiment, compared with a single dose at the beginning of an experiment, produced lower residual concentrations of complexed cyanide and higher foam volumes. At an iron to total cyanide ratio of 0·351:1,90% of the complexed cyanide concentration could be removed by one fifth less surfactant, using pulsed addition, compared with a single dose.     

Experimental validation of a theoretical analysis of the range of operation of catalyst poisons

A formula to calculate theminimum quantity of material necessary to poison or promote a supported metal catalyst, based on theoretical criteria of poisoning range, has recently been proposed (R.W. Joyner and J.B. Pendry, Catal. Lett. 1 (1988) 1). This paper reports experimental tests of this formula for chlorine, sulphur and iodine poisoning of a Pd/C catalyst for the hydrogenation of cyclohexene. For chlorine and sulphur a significant excess of poison is required compared to the estimate, while the results for iodine are in excellent agreement with the calculation. The theory is also compared with a number of literature studies of sulphur poisoning and appears to have wide validity.     

Calculation of the ignition sensitivity of dust clouds of varying size distributions

For a cloud of flammable dust in air to ignite, the temperature of the air must be a specific value that depends upon properties of the dust material and of the dust cloud.First, a theoretical treatment is used to explain variations in experimental ignition temperatures in terms of particle size. The theory modifies Cassel and Liebman's method to take account of residence time of dust in experimental furnaces or in hot air. It is shown that it is possible for the ignition temperature of mono-sized coal particles (about 50 μm diameter) to be minimal under a limited residence time.The theory is extended to deal with dust clouds with a distribution in particle size. It is shown that there exists a range of size distributions for which the possibility of ignition is at a maximum. The calculated results are presented in the form of Rosin—Rammler charts indicating the distribution most sensitive to ignition.     

Principles of Isotachophoresis and Dynamics of the Isotachophoretic Separation of Two Components

Abstract

This paper reviews the principles of isotachophoresis, a separation method in which a migrating steady-state zone structure is established through electrical transport. Prior to attaining steady state, a moving transient system of homogeneous zones is gradually reduced to consecutive sample zones of constant length, where all boundaries migrate with equal velocity. The separation process of a pair of sample components is discussed to illustrate the dynamics of this unique electrophoretic method. Solutions in terms of separation time, separation rate, and separation distance are given. Furthermore, techniques for the enhancement of the maximum sample load of a column are discussed. The features of isotachophoresis are presented to illustrate the advantages of multichannel zone detection in an isotachophoretic instrument.     

Co-carbonization of solvent fractions of hydrogenated and alkylated SRC pitches in studies of formation of needle-cokes

The optical texture of cokes from two SRC pitches of different coking properties, from co-carbonizations of these materials and of hydrogenated and alkylated products has been studied. The objective, relative to formation of needle-cokes, is to correlate the optical texture of cokes with the chemical structure of the pitch materials using both benzene-soluble (BS) and insoluble (BI) fractions of the pitches. Hydrogenation improved the compatibility of the BS fraction of the inferior SRC pitch (No. 2) with the BI fractions of the two pitches (non-hydrogenated) using a ratio of only 1 to 9. Before hydrogenation, a ratio of BS to BI of 8 to 2 did not give a needle-coke. In contrast, alkylation destroyed the compatibility of the BS fraction of the superior SRC pitch (No. 1) with the BI fraction (non-alkylated) using a ratio of 6 to 4, and which gave a needle-coke before alkylation. Hydrogenation of the alkylated material restored the compatability. The relevance of these studies to industrial carbonization processes is discussed in terms of chemical treatment and the hydrogen economy.     

乙炔清净废次钠水循环利用工艺

通过研究新鲜次氯酸钠有效氯含量、pH值等因素对新、废次氯酸钠混合过程及效果的影响,开发了废次氯酸钠溶液循环利用的新工艺。     

Hydrophobicity of Thin Films of Compounds of Low‐Electronegativity Metals

Hydrophobic materials capable of withstanding harsh conditions are required for various applications. Here, we show that oxides and nitrides of various low‐electronegativity metals are hydrophobic hard ceramics. We attribute their hydrophobicity to low Lewis acidity of the low‐electronegativity cations implying a low ability of the cations on the surface to form coordinate bonds with water oxygen anions. Furthermore, we observe a systematically stronger hydrophobic behavior of nitrides compared with the corresponding oxides, which we attribute to nitrogen being a poorer Lewis base than oxygen due to a reduced number of lone pairs of electrons, implying a lower ability of nitrogen anions on the surface to form hydrogen bonds with water hydrogen cations. Most of the oxides and nitrides investigated exhibit high values of hardness. Therefore, oxides and nitrides of low‐electronegativity metals should find application as hydrophobic materials in harsh conditions.     

Effect of the cooling rate of the melt on the structure of electrosmelted forsterite refractories

Conclusions The quenching in water of a forsterite composition makes it possible to obtain a finecrystalline material which contains no glass phase.Obtaining a refractory forsterite material by quenching in water makes it possible to shorten the production cycle and, as a result, to eliminate the cooling of massive blocks and their primary crushing. The development and stabilization in the material of a dendrite structure producing a strengthened interphase bond makes it possible to increase the strength of the refractory products.Translated from Ogneupory, No. 2, pp. 27–29, February, 1987.     

A Self-Delamination Method of Measuring the Surface Energy of Adhesion of Coatings

A self-delamination technique is presented to assess the surface energy of adhesion of coatings. By measuring the debond area resulting from a circular hole cut in a film adhered onto a substrate, the surface energy may be determined if the tensile modulus, Poisson's ratio and residual stress level of the film are known. This method is useful for coating thicknesses greater than a critical thickness for self-peeling. Using this technique, the surface energy for a polyimide film (cured up to 220°C) on a glass plate was determined to 3.2 Nm^-1.     

Effect of level of application on the relative effectiveness of rock phosphate

Responses of yellow serradella, slender serradella and subterranean clover to applications of superphosphate and Queensland apatite rock phosphate were compared in a field experiment in Western Australia. The rock phosphate was applied as a fine powder to a very sandy soil with a low buffering capacity for phosphate and for pH. At low levels of application, rock phosphate was about a tenth as effective as superphosphate — that is, ten times as much was required to give the same yield. With increasing levels of application, the relative effectiveness of rock phosphate declined to well below one per cent and hence more than 100 times as much was required to give the same yield. The decreasing relative effectiveness was incorporated into response equations. These were used to demonstrate that the decreasing relative effectiveness can be statistically tested and shown to be highly significant.A simulation study using the model of Kirk and Nye showed that a decrease in relative effectiveness with increasing level of application is especially likely when the particles of rock phosphate are very small, when the levels of application are high, and when the soil's buffering capacity for phosphate and for pH is low.     

注塑机拉杆三角螺纹端卸载槽的多目标优化

针对注塑机拉杆三角螺纹在近卸载槽处发生早期断裂的问题，在用ANSYS软件对近卸载槽处三角螺纹进行有限元分析的基础上，就拉杆三角螺纹端卸载槽的几何特性建立参数优化模型，以控制三角螺纹在近卸载槽附近的最大应力、卸载槽的最大应力以及卸载槽加工量最小化为统一的目标函数。通过对拉杆在单向拉伸力作用下的多目标优化，可使拉杆三角螺纹牙根在卸载槽处的最大应力降低55％，在偏载作用下，其最大应力降低21．4％。在单向拉伸力作用下，拉杆卸载槽的最大应力比平均单向拉伸应力提高26．5％，使卸载槽能够较好地发挥其卸载的作用。     

Determination of fuming propensity of bituminous materials

A procedure for measuring the fuming propensity of bituminous materials has been developed. This is based on the response of a flame-ionization detector to hydrocarbon vapours emanating from a large-size sample heated at a controlled rate of temperature rise and swept with a slow, constant flow rate of an inert gas. The fuming propensity is related to the temperature of equal volatility, defined by the measured temperature recorded for a specific, arbitrarily chosen, peak height produced on the flame-ionization-detector chart. The quantity of fumes generated from heated bituminous material is inversely related to the temperature of equal volatility.     

The determination of the coefficient of dynamic friction of organic powder compacts on steel

A practical experimental model system has been successfully used to study the frictional response of organic powder compacts sliding across a polished steel plate, representative of the die bore of a production compaction system. This system offers a controlled approach to the study of frictional phenomena occurring during compaction and facilitates a more detailed investigation into the fundamental mechanisms of friction than a simple resolution of forces within a punch and die apparatus.For acetylsalicyclic acid sliding on steel, the dynamic friction coefficient was found to be dependent on the displacement and, to a lesser extent, the initial normal load, whereas for PTFE on steel, the dynamic friction coefficient was independent of displacement and load and estimated at 0.09. Thus, soft organic materials exhibit very different frictional characteristics to those of brittle materials. These differences reflect the differing importance and magnitude of the three frictional components, adhesion, shear and ploughing.     

Fingerprinting of fatty acid composition for the verification of the identity of organic eggs

Organic products (such as organic eggs) usually have a higher price than the corresponding conventional products. This makes organic products susceptible to fraud. Administrative controls are conducted to detect this type of frauds. However, an analytical verification of the organic identity of food products would be very useful in this respect. It is unlikely that there is a single compound, or a few compounds, that differ sufficiently between organic and conventional eggs to be used as a marker of organic identity. Instead, fingerprinting of the organic products (that is to say, analyzing a wide range of compounds instead of only a few) might be used as a tool for their verification. Here, we have used the fatty acid composition of egg yolks as a fingerprint to verify the organic identity of eggs. From the fingerprints, chemometric models were built which predict the identity of eggs (organic or conventional) with high success rates.     

Improved utilization of marine species of low commercial value through the elaboration of hydrolysates

Although Mexico is a country with a great fishing potential, fish consumption remains very low. An important reason for this situation is the difficulty faced in regard to its preservation and distribution, a factor which notably increases the final price of the product. As is known, in some countries fish preservation is carried out through autolysis, using high concentrations of sodium chloride. This was the type of work carried out by us, in an effort to adapt the procedure to the species and conditions prevalent in Mexico. The raw material was selected according to its availability and cost. The selected species were mojarra (Archosargus unimaculatus) and sardine (Sardinops caerula). Three different fish-to-salt ratios were tested (1.5:1, 4:1 and 6:1), with incubation periods ranging from 4 to 24 weeks, at both 20 to 23 degrees C, and 37 to 39 degrees C. Results indicated that a fish-to-salt ratio of 4:1, at a temperature of 37 degrees C and an incubation period of 12 weeks, represent the optimun conditions for obtaining a fish sauce which is acceptable in flavor, with a protein content of 12% per 100 ml, and a storage life of at least 90 days. The recovery of the final product was 22%, reaching 35% in a second extraction. Sensory evaluation tests were undertaken by adding the sauce to cooked unsalted rice. According to the results, there was a favorable acceptance of the final product. The price calculated for the elaboration of the sauce at the household or rural level was lower, as compared with the price of protein from meat or egg which is 3-to-4-fold higher.     

Methodological framework for choice of intensified equipment and development of innovative technologies

Process intensification is recognized as a promising strategy to satisfy the objectives of sustainable development and economic competitiveness. Unfortunately, no general methodology still enables to choose the best available technologies from the many potential solutions. This work describes a step-by-step methodology that guides engineers from a given problem to a list of existing appropriate intensified devices. The first step of the methodology consists in identifying the process limitation among a list of 16 possibilities that cover a large spectrum of cases. Then, the methodology relates, through a pre-filled connection matrix, the identified limitations to a set of intensification strategies such as geometric (micro)structuring, periodic operation or multi-scale design. The third step relates these strategies to a list of technologies that apply these strategies or in which they can be applied. The matrices enable to sort these technologies by relevance with respect to the initial problem. The final step provides quantitative charts to compare the characteristics of these potential solutions with the specifications of the problem. The methodology not only yields to a short list of appropriate solutions to be technically designed and economically assessed, but also to a list of innovation strategies.