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Martinis J.,Bryan Research and Engineering | Froment G.F.,Texas A&M University
11AIChE - 2011 AIChE Spring Meeting and 7th Global Congress on Process Safety, Conference Proceedings | Year: 2011

A deterministic approach to molecular reconstruction of VGO was combined with single-event kinetics in the simulation of a hydrocracking process unit targeting maximum diesel production. Three different process flow configurations combining pre-treatment, reaction, fractionation, and recycle were studied. At the core of the simulation model, a computer-generated reaction network consisting of 126 million elementary steps and 18 million species described the chemistry of hydrocracking. Rate parameters of the elementary steps were modeled by the Single-Event concept, thus reducing the number of model parameters to be determined from plant data to a realistic level. A rigorous model for trickle-flow in packed-bed reactors was validated for extreme limiting conditions, e.g., local hydrogen depletion and transition to complete vaporization. This is an abstract of a paper presented at the 2011 AIChE Spring Meeting & 7th Global Congress on Process Safety (Chicago, IL 3/13-17/2011). Source

Atkinson B.R.,Bryan Research and Engineering | Prim E.,Pilot Energy Solutions LLC | Baker N.,Pilot Energy Solutions LLC
Hydrocarbon Engineering | Year: 2011

Hydrate formation in natural gas processing is examined and a model is created using ProMax® that simulate the behavior of water in an existing system. No level of natural gas liquid (NGL) recovery is found at 472 psig that does not have a potential for solids formation on one or more stages or streams. A shift in the hydrate curve is observed as the C3 recovery rate is increased. The conditions at 115 bpd of C3 recovery are in a solids forming zone, with three solutions to the hydrate curve at the operating pressure. Dehydration of the gas is observed in glycol systems allowed C 3 recoveries into the 100 bpd range. A molecular sieve unit would be effective in lowering water content even further, but this comes at a greatly added cost. Increased dehydration performance, even into the upper reaches of economical stripping gas flows, only moved the propane recovery ceiling out to approximately 35% or 100 bpd. Source

Zhang T.,Texas A&M University | Zhang T.,China University of Petroleum - Beijing | Leyva C.,Texas A&M University | Leyva C.,Research Center en Ciencia Applicada y Tecnologia Avancada | And 2 more authors.
Industrial and Engineering Chemistry Research | Year: 2014

A bench-scale experimental unit based on a Robinson-Mahoney reactor with completely mixed gas and liquid phases was used to study the hydrocracking of a light vacuum gas oil on two base metal sulfide containing acid catalysts, characterized by their textural properties, NH3-TPD and pyridine-adsorbed Fourier-transformed infrared (Py-FTIR) acidity. The reactor effluent was analyzed in great detail by means of online gas chromatography and gas chromatography-mass spectrometry which evidenced the role of the catalyst acidity. The detailed analysis allowed the reaction scheme to be expressed at the level required by the kinetic analysis in terms of the fundamental Single Event Kinetics approach and thus drastically reduce the number of independent kinetic parameters to be determined from the experimental data. Reactor simulations illustrate the detailed predictions made possible by this approach. © 2014 American Chemical Society. Source

Martinis J.M.,Bryan Research and Engineering
12AIChE - 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety, Conference Proceedings | Year: 2012

A series of algorithms were formulated to solve the formidable problem of generating detailed reaction networks for a given set of species following well-established rules governing the underlying chemistry of the process. In the particular case of hydroprocessing, computer science fundamentals, e.g., object-orientation, functional programming, and recursive operations, on relational sets are applied to generate consistent reaction networks starting from the fundamentals of transition-metal catalysis and carbenium ion chemistry. As a result, reaction networks at the elementary step level are generated for catalytic reforming, hydroisomerization, hydrodewaxing, and hydrocracking. This is an abstract of a paper presented at the 2012 AIChE Spring Meeting and 8th Global Congress on Process Safety (Houston, TX 4/1-5/2012). Source

Davila G. Y.O.,Pdvsa | Martinis C. J.M.,Pdvsa | Martinis C. J.M.,Bryan Research and Engineering
Industrial and Engineering Chemistry Research | Year: 2011

A method based on graph theory has been formulated to estimate some key thermochemical properties commonly utilized in modeling acid-catalyzed transformations of hydrocarbons at the elementary step level. Presently, modeling techniques for these transformations frequently convey the computer-aided generation of reaction networks involving a very large number of molecules and intermediate species such as carbenium ions. Although quantum mechanical calculations have been widely used to estimate thermodynamic properties of carbenium ions accurately, the current performance of such techniques is yet insufficient for very large sets of species. The proposed method handles this problem by simply analyzing the connectivity of the carbon atoms within a molecule, which is less demanding from a computational point of view. Thus, it is possible to obtain information on the contributions from different structural groups and their indistinguishability, making property estimation straightforward. This work presents a set of rules for calculating the symmetry numbers of hydrocarbons with up to 2 rings, and Benson-like structural contribution groups for estimating the enthalpy of carbenium ions. © 2011 American Chemical Society. Source

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