Mitigating fines plugging in high pressure/temperature hydrotreaters using an induced-pulsing trickle-bed filtration approach

The fine particles deposition/detachment process under liquid flow shear shock or forced periodic operation conditions in a high pressure/temperature trickle-bed reactor was analyzed theoretically using a dynamic multiphase flow deep-bed filtration model. The model incorporates physical effects associated with detachment of the fine particles from the collector surface as a result of colloidal forces in the case of Brownian particles or by the hydrodynamic forces for non-Brownian particles. An important finding of the work was that for non-colloidal fine particles, forced periodic operation procured improvements (assessed in terms of reduction in specific deposit and pressure drop) in the mitigation of plugging in trickle-bed reactors. However, due to the highest critical shear stress values for fine particles in the colloidal range, forced periodic operation did not substantiate useful practical effect. In the circumstances when Brownian fine particles are involved, reduction of plugging may take place under liquid flow shock conditions.     

Electrostatic Beneficiation Apparatus for Fluidized Iron and Other Ores

The paper presents a new apparatus for electrostatic beneficiation of fluidized ores. The apparatus comprises a fluidized bed, an optional metallic screen electrode located above the bed, and a series of collecting U-or V-shaped troughs. The troughs are moving horizontally below the screen. The vertical electric field traversing the fluid bed was produced by applying high voltage to a porous metallic plate on the floor of the bed and grounding the troughs and screen.     

Expansive sulphate aluminate cements

The possibility to prepare expensive sulphate aluminate masses from certain wastes (phosphogypsum and belitic waste) and usual raw materials (limestone, bauxite) has been investigated. The chemical and minerological composition of these synthetic clinkers as well as the nature of their hydration products has been determined by current methods. The mechanism of cement expansion and the factors affecting the correlation between mechanical strength and expansion have been also studied.     

Onset of pulsing in trickle beds with non-Newtonian liquids at elevated temperature and pressure—Modeling and experimental verification

The onset of pulse flow in trickle-bed reactors involving gas-non-Newtonian liquid systems was predicted from a stability analysis of the solutions around equilibrium steady-state trickle flow of a transient two-fluid model based on the volume-average mass and momentum balance equations. The model was developed for the versatile Herschel-Bulkley constitutive rheological equation from which special solutions for plastic Bingham fluids, power-law shear-thinning and thickening fluids, as well as Newtonian fluids were derived. The impact of yield stress, consistency and power-law indices, and temperature and reactor pressure on the trickle-to-pulse flow transition was analyzed theoretically. Model predictions of the trickle-to-pulse transition for gas-non-Newtonian liquid systems were confronted with elevated temperature and pressure experimental transition data obtained for air-0.25 and 0.5 mass(carboxymethylcellulose) CMC solution systems measured by means of an electrical conductivity technique. In addition the model version offspring corresponding to the Newton case (n=1,k=μ_?,τ₀=0), confronted with measured high temperature/pressure-transition data from this work and high-pressure transition data from Wammes et al. [1990. The transition between trickle flow and pulse flow in a cocurrent gas-liquid trickle-bed reactor at elevated pressure. Chemical Engineering Science 45, 3149; 1991. Hydrodynamics in a cocurrent gas-liquid trickle bed at elevated pressures. A.I.Ch.E. J. 37, 1849] and Burghardt et al. [2002. Hydrodynamics of a tree-phase fixed-bed reactor operating in the pulsing flow regime at an elevated pressure. Chemical Engineering Science 57, 4855] proved equally successful.     

Quantifying eventual consistency with PBS

Data store replication results in a fundamental trade-off between operation latency and data consistency. At the weak end of the consistency spectrum is eventual consistency providing no limit to the staleness of data returned. However, anecdotally, eventual consistency is often “good enough” for practitioners given its latency and availability benefits. In this work, we explain why eventually consistent systems are regularly acceptable in practice, analyzing both the staleness of data they return and the latency benefits they offer. We introduce Probabilistically Bounded Staleness (PBS), a consistency model which provides expected bounds on data staleness with respect to both versions and wall clock time. We derive a closed-form solution for versioned staleness as well as model real-time staleness under Internet-scale production workloads for a large class of quorum-replicated, Dynamo-style stores. Using PBS, we measure the latency–consistency trade-off for partial, non-overlapping quorum systems, including limited multi-object operations. We quantitatively demonstrate how and why eventually consistent systems frequently return consistent data within tens of milliseconds while offering significant latency benefits.     

On a general method for the synthesis of the path approximation mechanismsAllgemeines entwurfsverfahren für getriebe zur angenäherten erzeugung von kurven

The purpose of this paper is to give a general method for the synthesis of the path approximation mechanisms. The method is based on matrix algebra and is adjusted for use with a digital computer. The procedure described for applying the proposed method of synthesis is made on the one-loop spatial mechanism with seven links having constrained motion, but it may be employed for the synthesis of any type of simple closed or poly-loop mechanism.     

Comparative study of aromatic polyimides containing methylene units

Two series of aromatic polyimides have been synthesized by solution polycondensation of certain aromatic dianhydrides with two aromatic diamines containing methylene groups; one of the diamines has also a methyl substituent on each benzene ring. These polymers have been studied with regard to their solubility, thermal stability, film forming ability, and mechanical properties of their films.     

Design of a Three-Phase Flux Reversal Machine

A comprehensive design of a novel doubly-salient, stator-permanent magnet (PM) three-phase flux reversal machine (FRM) is presented in this paper. FRM has a robust and easy-to-build structure and is suitable for high-speed applications. Detailed design procedures and formulae are given. All of the dimensions of the FRM are derived. Basic parameters are calculated. The most important aspect of this design is to consider the wide operating speed range. The work presented may serve as a guideline for the general principle of design on three-phase FRM. Furthermore, the methodology and formulae introduced in this paper are also applicable to other types of PM and/or reluctance machine.