Xiaogang Shi

• PhD
• Professor (Associate) at China University of Petroleum, Beijing

A method to develop a simplified particle model (SPM) for the torrefaction of a centimeter-sized biomass particle has been proposed. The SPM was developed based on reasonable assumptions, and these assumptions were validated with a comprehensive particle model (CPM) from Shi et al. (2016), which considers the detailed transport phenomena and chemic...

A three-dimensional finite element model for the pyrolysis of a centimeter-sized biomass particle was developed by coupling the transport phenomena and the kinetic reactions considering both the primary biomass devolatilization and the secondary homogeneous and heterogeneous conversion of the tarry vapors within the particle. Validating the model a...

Catalyst loss is a typical fault that impacts the long-term operation of the fluidized catalytic cracking (FCC) in the oil refining process. The FCC disengager is a critical place for separating the catalyst from oil gas. A fast and precise fault-cause judgment of catalyst loss is vital for avoiding catalyst loss failures. In this study, a novel fa...

Investigating the thermal hysteresis and its effect on the kinetic behaviors and reaction model of vacuum residue pyrolysis is of significant importance in industry and scientific research. Effects of heating rate and heating transfer resistance on the pyrolysis process were examined with the thermogravimetric analysis. The kinetic characteristics...

This study utilized a thermogravimetric analyzer to assess the thermal decomposition behaviors and kinetics properties of vacuum residue (VR) and low-density polyethylene (LDPE) polymers. The kinetic parameters were calculated using the Friedman technique. To demonstrate the interactive effects between LDPE and VR during the co-pyrolysis process, t...

The accuracy of the computational fluid dynamics simulations of mass transfer process in bubble columns is significantly influenced by the mass transfer models. Various mass transfer models have been developed based on different theories. However, it is still confusing on the choice of mass transfer models when performing the simulations of mass tr...

The sub-millimeter bubble technique can enhance the gas-liquid inter-phase mass transfer by significantly reducing the bubble size and increasing the gas-liquid interfacial area. To accurately describe the flow and mass transfer characteristics, it is necessary to characterize bubble parameters. High-speed photography followed by image processing i...

In trickle bed reactor (TBR), the gas-liquid mass transfer is closely related to the thickness of liquid film and the wetting of catalyst particles. Therefore, knowledge on the flow and distribution of liquid film on particle surface is critical for evaluating the performance of TBR. In this work, high-speed camera was used to study the flow behavi...

In this work, a cluster-based mass transfer and reaction model was proposed according to large number of simulation results by conducting ozone decomposition inside spherical cluster, which is more realistic compared with the conventional homogeneous description of mass transfer and chemical reaction process. Then, this model was coupled with three...

In turbulent fluidized bed (TFB), the superficial gas velocity usually varies since chemical reactions can change the number of gas moles. However, information from the study without considering the variation of gas velocity is usually used to guide the design and operation of industrial TFB reactors. In order to reveal the difference of constant a...

This paper reviews the recent advances in multi-scale computational fluid dynamics (CFD) simulations of biomass pyrolysis in fluidized bed reactors. The interconnection among molecular-scale, particle-scale, CFD cell-scale, and reactor-scale are first introduced, together with the Eulerian-Lagrangian (E-L) and Eulerian multi-fluid model (MFM) frame...

A data-driven model framework integrating Feature Subset Selection (FSS), production pattern clustering analysis and prediction was proposed for predicting ethylene yield of steam cracking process by using the massive sensing data recorded by the Distributed Control System (DCS) of petrochemical enterprises. Firstly, an Ensemble-Filter FSS model ba...

The pyrolysis of coal mixing with CaO can produce uniform mixture of residual char and CaO, which can be further converted into calcium carbide for providing alternative way of ethyne production. Therefore, knowledge on the pyrolysis behavior of coal at the presentation of CaO is important for the industrial production of such mixture of residual c...

Gas-liquid reactors containing bubbles are intensively used in the chemical industry. However, the gas-liquid mass transfer rate is usually the rate-limiting step. One possible way to intensify the mass transfer is aeration with sub-millimeter bubbles (1-1000 μm) which efficiently increase interfacial area. However, previous studies usually focus o...

With the rapid development of artificial intelligence and the corresponding supporting data system, chemical process modeling technology has been developed to a new and high level. The hybrid modeling method combining multiple mechanism models and data-driven models in a reasonable structure can fully use the first principle and process data of che...

Pyrolysis of low-rank coal at the presence of CaO can result in uniform mixture of residual char and CaO, which can further produce calcium carbide for providing alternative way of ethyne production. Large mixture (i.e. with the addition of CaO) coal particle at centimeter-scale is usually used in such industrial pyrolysis process, for which intrap...

Gas-solids drag model is crucial for the accurate prediction of gas-solids flow in turbulent fluidized bed (TFB). A four-zone drag model based on cluster was proposed to describe the gas-solids interactions in TFB. The model considers the cluster effect in the bottom dense bubbling zone while regards the particles as discrete ones in the top dilute...

The gas-solids flow in high-density downers with FCC particles was simulated by Computational Particle Fluid Dynamics (CPFD) approach. A drag model was proposed based on the equivalent diameter of cluster with the analysis of force balance on particle cluster. A global sensitivity analysis method was used to analyze the influencing factors of clust...

The difference of gas-solids flow between a circulating fluidized bed (CFB) downer and riser was compared by computational particle fluid dynamics (CPFD) approach. The comparison was conducted under the same operating conditions. Simulation results demonstrated that the downer showed much more uniform solids holdup and solids velocity distribution...

Computational Particle Fluid Dynamics (CPFD) simulation was performed to study coal pyrolysis in a Circulating Fluidized Bed (CFB) downer containing binary particles (coal particles and heat carrier particles). A suitable drag model, which considers the cluster effect by assuming dynamic equilibrium for particles in and out cluster, was incorporate...

Finite element modeling was performed to study the pyrolysis of centimeter‐sized biomass particles. The model proved to be accurate in predicting the intraparticle heat transfer during the pyrolysis of biomass particles at different operating conditions and for various particle properties. It was further applied to find the dominant factors of biom...

A combined Computational Fluid Dynamics and Population Balance Model (CFD-PBM) was developed to study the flow hydrodynamics of the slurry bed. The CFD-PBM applied a modified drag force model by considering the reduced drag force between gas and liquid phases at the presence of particle. Results show that the CFD-PBM with the modified drag force mo...

The interactions of gas and solids are important in determining the flow structures in the Circulating Fluidized Bed (CFB) downer. Proper description of the interphase drag model is thus crucial for simulating the downer. Considering that cluster with several numbers of particles can be present in the downer, an interphase drag model was developed...

With the development of computing power, the simulation of circulating fluidized bed (CFB) has developed from riser-simplified simulation to riser-only simulation, then to full-loop simulation. This paper compared these three methods based on pilot-scale CFB experiment data to find the scope of application of each method. All these simulations, usi...

Biomass slow pyrolysis inside a screw reactor was studied using three-dimensional (3D) computational fluid dynamics (CFD) modeling. A multi-component (cellulose, hemicellulose and lignin with detailed elemental composition), multi-step kinetic model was incorporated into the CFD model. Modeling results were compared with experimental results with r...

Three-dimensional (3D) computational fluid dynamics (CFD) simulations were performed to study solids flow dynamics and solids back-mixing behavior in a screw reactor (designed for thermal conversion of dry biomass particles) based on the Eulerian-Eulerian method. Simulation results were compared against experimental data with respect to filling deg...

Bubbling fluidized bed is extensively used in petrochemical and other process industries. The performance of the bubbling fluidized bed can be improved through the placement of various internals, among which structured packing is proposed to be a promising type of internal. To address the advantage of such packing over the bubbling fluidized bed wi...

In order to study the system hydrodynamics in a circulating fluidized bed (CFB), a 3D full‐loop simulation was conducted for a pilot‐scale CFB. The Eulerian‐Eulerian two‐fluid model with the kinetic theory of granular theory helped to simulate the gas‐solids flow in the CFB. The system hydrodynamics including pressure balance, vectors of gas and so...

Computational fluid dynamics (CFD) simulation can provide in‐depth knowledge on hydrodynamics in slurry‐bed reactors. The accuracy of CFD simulation is highly depending on the description of the interactions between gas phase and slurry phase with the drag model. Conventional drag models were usually developed for gas‐liquid systems without conside...

Three-dimensional (3D) Computational Fluid Dynamics (CFD) simulations were performed to study gas flow, heat transfer and catalytic reactions of vacuum gas oil (VGO) inside spherical and ellipsoidal clusters consisting of FCC catalyst particles. Simulation results with respect to the gas flow inside the cluster and the convective heat transfer betw...

With the Computational Particle Fluid Dynamic (CPFD), which is based on the scheme of Multi-Phase Particle-In-Cell (MP-PIC), the present work studied the flow hydrodynamics and solids back-mixing behaviors in the riser with smooth and abrupt exit geometries. It was found that the flow hydrodynamics and solids back-mixing behaviors are quite differe...

A Computational Particle Fluid Dynamics (CPFD) approach was applied to investigate the solids residence time distribution (RTD) and back-mixing behavior in a circulating fluidized bed (CFB) riser. The comparison between the simulation results and the experimental data indicates that the CPFD method was capable to predict the hydrodynamics and solid...

Industrial CFB risers usually handle polydisperse mixtures with broad size distribution, which significantly influenced the performance of the reactors. However, traditional Computational Fluid Dynamics (CFD) models usually assumed that the particle followed the mono-disperse distribution. In the present work, the method of computational particle f...

Solids back-mixing significantly influences the performance of circulating fluidized bed (CFB) risers. A better understanding of the solids back-mixing behavior is greatly essential for the design and operation of CFB risers. Computational particle fluid dynamics (CPFD) modeling based on the multiphase particle-in-cell (MP-PIC) method was applied t...