Analysis of process variables via CFD to evaluate the performance of a FCC riser

Feedstock conversion and yield products are studied through a 3D model simulating the main reactor of the fluid catalytic cracking (FCC) process. Computational fluid dynamic (CFD) is used with Eulerian-Eulerian approach to predict the fluid catalytic cracking behavior. The model considers 12 lumps with catalyst deactivation by coke and poisoning by alkaline nitrides and polycyclic aromatic adsorption to estimate the kinetic behavior which, starting from a given feedstock, produces several cracking products. Different feedstock compositions are considered. The model is compared with sampling data at industrial operation conditions. The simulation model is able to represent accurately the products behavior for the different operating conditions considered. All the conditions considered were solved using a solver ANSYS CFX 14.0. The different operation process variables and hydrodynamic effects of the industrial riser of a fluid catalytic cracking (FCC) are evaluated. Predictions from the model are shown and comparison with experimental conversion and yields products are presented; recommendations are drawn to establish the conditions to obtain higher product yields in the industrial process

Cracking Piles of Brittle Grains

A model which accounts for cracking avalanches in piles of grains subject to external load is introduced and numerically simulated. The stress is stochastically transferred from higher layers to lower ones. Cracked areas exhibit various morphologies, depending on the degree of randomness in the packing and on the ductility of the grains. The external force necessary to continue the cracking process is constant in wide range of values of the fraction of already cracked grains. If the grains are very brittle, the force fluctuations become periodic in early stages of cracking. Distribution of cracking avalanches obeys a power law with exponent $\tau = 2.4 \pm 0.1$.Comment: RevTeX, 6 pages, 7 postscript figures, submitted to Phys. Rev.

A study on surface cracking in extrusion of aluminium alloy AA2014

Surface cracking is generally recognised as one of the main defects occurring during the process of aluminium extrusion, especially in the case of the so called hard aluminium alloys. Previous experiments suggest that this type of defect is caused by the rise in temperature as the process proceeds. Some experiments indicate that the surface quality is good even though the temperature may be high during extrusion. It is also well known that crack criteria have been adopted to explain the cracking that occurs in extrusion, blanking and rolling, etc. In this study, a finite element method (FEM) is used in different ways to predict surface cracking during hot extrusion. The crack criteria are integrated into the FEM code FORGE12.0. The effectiveness of these criteria in predicting surface cracking in the case of hot extrusion is discussed. The FEM simulation also provides some other quantitative data, such as the temperature rise during extrusion from different initial temperatures. In addition, the principal stresses at the die land area at different extrusion stages are also shown

How Does Silo Storage Time Affect Pavement Durability in Cold Weather Climates?

One of the most significant problems in asphalt pavements in cold weather climates like New England is thermal cracking. Thermal cracks allow water to penetrate into a pavement, significantly weakening the entire structure which necessitates expensive maintenance and repair. The main goal of this research project was to investigate how heated silo storage time, a process during asphalt production, impacts how likely asphalt pavement is to experience thermal cracking related problems. Asphalt concrete specimens aged for various amounts of time in a storage silo were tested using the Disk-Shaped Compact Tension test, a laboratory test that evaluates asphalt specimens\u27 thermal cracking susceptibility. Although the results were not definitive, the data analysis indicated that silo storage time is having certain negative effects on asphalt’s thermal cracking resistance. Ideally, the results from this research will give transportation agencies and private contractors a better understanding of how production processes impact the performance of asphalt concrete

Stress corrosion cracking evaluation of precipitation-hardening stainless steel

Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure

Strain-age cracking in Rene 41 alloy

Weldability test determines the effects of material and process variables on the occurrence of strain-age cracking, and demonstrates effective and practical means for its reduction. Studies consist of tensile, impact, and stress-rupture tests

Hygrothermal effects on mechanical behavior of graphite/epoxy laminates beyond initial failure

An investigation was conducted to determine the critical load levels and associated cracking beyond which a multidirectional laminate can be considered as structurally failed. Graphite/epoxy laminates were loaded to different strain levels up to ultimate failure. Transverse matrix cracking was monitored by acoustic and optical methods. Residual stiffness and strength that were parallel and perpendicular to the cracks were determined and related to the environmental/loading history. Results indicate that cracking density in the transverse layers has no major effect on laminate residual properties as long as the angle ply layers retain their structural integrity. Exposure to hot water revealed that cracking had only a small effect on absorption and reduced swelling when these specimens were compared with uncracked specimens. Cracked, moist specimens showed a moderate reduction in strength when compared with their uncracked counterparts. Within the range of environmental/loading conditions of the present study, it is concluded that the transverse cracking process is not crucial in its effect on the structural performance of multidirectional composite laminates

Environmental fatigue of an Al-Li-Cu alloy. Part 3: Modeling of crack tip hydrogen damage

Environmental fatigue crack propagation rates and microscopic damage modes in Al-Li-Cu alloy 2090 (Parts 1 and 2) are described by a crack tip process zone model based on hydrogen embrittlement. Da/dN sub ENV equates to discontinuous crack advance over a distance, delta a, determined by dislocation transport of dissolved hydrogen at plastic strains above a critical value; and to the number of load cycles, delta N, required to hydrogenate process zone trap sites that fracture according to a local hydrogen concentration-tensile stress criterion. Transgranular (100) cracking occurs for process zones smaller than the subgrain size, and due to lattice decohesion or hydride formation. Intersubgranular cracking dominates when the process zone encompasses one or more subgrains so that dislocation transport provides hydrogen to strong boundary trapping sites. Multi-sloped log da/dN-log delta K behavior is produced by process zone plastic strain-hydrogen-microstructure interactions, and is determined by the DK dependent rates and proportions of each parallel cracking mode. Absolute values of the exponents and the preexponential coefficients are not predictable; however, fractographic measurements theta sub i coupled with fatigue crack propagation data for alloy 2090 established that the process zone model correctly describes fatigue crack propagation kinetics. Crack surface films hinder hydrogen uptake and reduce da/dN and alter the proportions of each fatigue crack propagation mode

Study of the Influence the Acidity Level of Sulphuric Acid to Thermal Cracking and Triglyceride Saturation of Crude Palm Oil by Using Two Stages Electrochemical Thermal Cracking

Crude Palm Oil (CPO) was experienced with electrolyze by using two stages electrochemical thermal cracking reactor, zeolyte as catalyst, silver as cathode and cuprum as anode. In this research, we used electrolyte solution for 2 kinds of concentrate which was 40 and 60% of sulphuric acid (H2SO4). It worked in 1 atm with electrolyze for 1 hour, heating till reaching temperature 80oC for 1 hr, fogging process for 1 hr, and heating without electrolyze nor fogging about 30 minutes. From lubricity analyze, this product is a fuel with high lubricity. The analyzer showing that cracking of triglyceride of crude palm oil has same characteristics with diesel