Zhen Hou

Molecule-based modeling of heavy oil

A molecular-level kinetics model has been developed for the pyrolysis of heavy residual oil. Resid structure was modeled in terms of three attribute groups: cores, inter-core linkages, and side chains. The concentrations of attributes were constrained by probability density functions (PDFs) that were optimized by minimizing the difference between the properties of the computational representation—which were obtained by juxtaposing the attributes—to measured properties, which were obtained by analytical chemistry measurements. Computational tools were used to build a reaction network that was constructed based upon model compounds and their associated kinetics. For cases with an intractable number of species, equations were written in terms of the three attribute groups and the molecular composition was retained implicitly through the juxtaposition. These modeling methods were applied to the Shengli and Daqing resids. The composition of the simulated molecular feedstock fit well with analytical chemistry measurements. After simulated pyrolysis, both resids showed representative increases in the weight fractions of lighter hydrocarbons. Relevant end-use properties were predicted for the product mixtures.

Enhancing the value of detailed kinetic models through the development of interrogative software applications

Abstract A suite of user-friendly software tools was developed to help increase the accessibility of detailed kinetic models to a wide range of users from modelers to research collaborators to process engineers. The aims of these users were the basis for the software development. The tools are illustrated for development, analysis and usage of a detailed catalytic naphtha reforming model. After initial model construction, the Reaction Network Visualizer and KME (Kinetic Model Editor) Results Analyzer helped in understanding the characteristics of the reaction pathways, molecular profile and also assisted in tuning the kinetic parameters. The I/O (Input/Output) Converter permits execution of a molecular-level model in a manner which focuses on only measurable inputs and outputs. The KME Reactor Flowsheet tool increased the core kinetics model capabilities by allowing the model building to be based on data from a pilot or commercial reactor, including schemes with split feed streams and reactor bypasses.

Molecular-Level Composition and Reaction Modeling for Heavy Petroleum Complex System

A new methodology for the molecule-based modeling of heavy petroleum mixtures has been developed. Molecules in the heavy feedstock have been described in terms of three essential structural attributes (cores, side chains, and inter-core linkages) and then statistically juxtaposed into a set of representative molecular compositions that can be constrained by a set of probability density functions (pdfs). In order to obtain the optimal molecular composition, an optimization loop was employed to minimize an objective function in terms of available measurements via adjusting the limited parameters of the pdfs. An example of resid feedstock containing 400,000 components was created using only O(30) parameters. To limit the kinetic model to a practical size, the reaction model was described in terms the reactions of the three constituent types and a set of irreducible molecules. Subsequent product property estimation was a straightforward juxtaposition of attributes. For example, a model for resid coking was built in terms of 2,839 attributes and equations but kept the full compositional details of the 400,000-molecule mixture.