Study of direct and indirect naphtha recycling to a resid FCC unit for maximum propylene production

To satisfy the increasing propylene demand, direct and indirect naphtha recycling schemes around an existing resid fluid catalytic cracking (FCC) unit were investigated. To this aim, light cracked naphtha (LCN), heavy cracked naphtha (HCN) and a PolyNaphtha (PN) oligomerisation product were cracked under a wide range of operating conditions over a commercial Y zeolite based equilibrium catalyst. Experimental data were acquired in three different units: a fixed bed bench scale unit, a fixed fluidised bed unit and an adiabatic circulating fluidised bed pilot plant. It was shown that FCC naphthas require high operating severities to crack, and that even then their conversion remains relatively moderate. Hence, direct recycling to the main riser does not seem a viable pathway to increase propylene product. Feeding FCC naphthas to a second reaction zone operating at high severity allows to increase the propylene yield in a significant manner. Increasing conversion, however, not only leads to higher LPG and propylene yields, but also results in very high dry gas yields. An alternative scheme was proposed, in which the olefinic C₄ and C₅ fractions are converted into a naphtha fraction through oligomerisation in a dedicated unit before being recracked in the secondary riser. As the highly olefinic oligomerised effluent mainly consist of dimerised and trimerised butenes and pentenes, this feed is more easily cracked and high conversions can be achieved. This indirect interconversion of butenes and pentenes into propylene therefore effectively allows to convert these butenes and pentenes into propylene, resulting in a significant increase in propylene yield. Each of the three main naphtha recycle options (directly to the main riser, directly to a secondary riser or indirectly via a light olefin oligomerisation unit) have been analysed and compared to a base case. In the evaluation of each of these schemes, all heat balance effects, both on the riser and the regenerator side, have been accounted for. The proposed process scheme with an indirect recycle via an oligomerisation unit enhances the already inherent flexibility of the FCC unit. The naphtha recycle can be turned on or off, the second reaction zone can be used to crack naphtha or to crack resid feed to maximise throughput, while the effluent of the oligomerisation unit can be recycled to the FCC unit for propylene production or hydrogenated and sent to gasoline and kerosene pool.     

Surface Attractive Forces of Glass Batch Particles

The forces of surface interaction between glass batch components are considered. A comparison between capillary and gravitational forces for particles of different sizes at different stages of glass batch preparation is carried out. The dependences of capillary force on the volume of liquid and the distance between particles are discussed.__________Translated from Steklo i Keramika, No. 3, pp. 7 – 9, March, 2005.     

Displacement Discontinuity Method for Fracture Mechanics Analysis of Reissner Plates: Static and Dynamic

This paper is concerned with the displacement discontinuity method applied to the shear deformable plates (Reissner’s and Mindlin’s theories) with cracks subjected to static and dynamic loads. Fundamental solutions of dislocation are derived using the Fourier transform method and the Laplace transformation technique. Boundary integral equations are presented in terms of rotations/displacement on the crack surfaces. The Chebyshev polynomials of the second kind are used to evaluate the integral equations with hypersingular kernels on the crack boundaries and determine the stress intensity factors at the crack tips. Comparisons are made with other numerical solutions to demonstrate the proposed method is accurate both for static and dynamic problems.     

Judgment: The Foundation of Professional Success.

Lists of core competencies or critical capabilities are popular and plentiful. This article makes the case that a single core competency or critical capability accounts for professional success: the exercise of judgment. Judgment is the critical determinant of the quality of professional decisions, actions, and evaluations. Practical models of judgment are presented. The elements and dynamics of judgment are detailed. Individual, group, and organization implications are explored. Coaching and consulting interventions are explained. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

All-Optical Vestigial Sideband Generation Using a Semiconductor Optical Amplifier

An all-optical setup to generate vestigial sideband signals based on self-phase modulation in a semiconductor optical amplifier is experimentally demonstrated at 10 Gb/s. Sideband suppressions higher than 15 dB are reported with improved eye opening. Wavelength-independent operation over 26 nm is demonstrated. Increased chromatic dispersion tolerance is verified: a receiver sensitivity penalty of 5.3 dB, relative to back-to-back, is obtained after transmission over 2720 ps/nm; whereas conventional double sideband is penalized by 4.0 dB after 1360 ps/nm     

Effects of solid retention time on the performance of submerged anoxic/oxic membrane bioreactor.

In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH(4+)-N to NO(3-)-N was readily achieved over a feed NH(4+)-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study.     

Synthesis by sol-gel route and characterization of Yttria Stabilized Zirconia coatings for thermal barrier applications

This paper deals with the development of new synthesis techniques for functional materials such as Yttria Stabilized Zirconia (YSZ) used in the field of thermal barriers coatings. Currently, Thermal Barrier Coatings (TBCs) are manufactured by dry route technologies (EB-PVD or plasma spray) but such methods are directional and often require costly investments and complicated operations. We have carried out significant work aimed at developing sol-gel routes, which are nondirectional methods, to prepare, by suitable chemical modifications, nanocrystalline materials with a controlled morphology. The main advantage of this method is to decrease the crystallization temperature, much lower than the conventional processes, allowing the synthesis of reactive powders with nanometric particles size. In this paper, the formulation of an alkoxide sol has been optimized in order to obtain homogeneous YSZ films. Nature and quantity of binders have been studied. Superalloys have been then immersed in the sol and withdrawn at several controlled rates before being annealed at different temperatures. The films microstructures have been investigated using scanning electron microscopy. It appears that the combination of a slower withdrawal speed (17 cm/min) with a 3 wt.% content of DBP allows to obtain the most homogeneous and the thicker coatings. Moreover, SEM-FEG observations have shown that the deposit is present all over the rough surface of the substrate and is composed of two morphologies: a YSZ thin covering film and a thicker discontinuous layer duplicating the substrate topography.