Jicheng Bi

Characteristics of residues from thermal and catalytic coal hydroliquefaction

Abstract The properties of residues from thermal or catalytic coal hydroliquefaction experiments were characterised by the ultimate, proximate analyses. The relations between the properties of the residues and the liquefaction reaction conditions, such as temperature, time, catalyst, H-donor solvent and atmosphere were investigated. Variations in H/C ratio and organic volatile matter (OVM) content of the residues with liquefaction conditions and coal conversion were studied. Results show that liquefaction temperature and time are main factors that control the organic properties of the residues. The roles of the Fe–S catalyst and H-donor solvent are to reduce the proportion of condensation products in the residue rather than increase the extent of polymerisation. Consequently, coal liquefaction conversion is improved by 100% by the catalyst, but H/C ratio and OVM content of the residues are not significantly decreased.

Computational fluid dynamics for dense gas-solid fluidized beds

Abstract Many computational fluid dynamics (CFD) models for describing the hydrodynamics of dense gas-solid flows in fluidized beds have been put forward in the past few decades. These models treat the solid phase as continuum or discrete particles, which leads to Eulerian-Eulerian or Eulerian-Lagrangian formulations, respectively. Different governing equations and closure relations essentially result from an insufficient understanding of the complex gas-particle and particle-particle interactions for gas-solid flows. The current status of these models is discussed briefly in this paper. All the approaches in the literature modify only the solid phase momentum balance equcation introducing various forms of the solid phase stress tensor and the solid phase pressure drop in the Eulerian-Eulerian models. Taking them into consideration, a new model for predicting the fluid behavior of dense gas-solid flows in fluidized beds has been developed, which contains new terms in both the particle and gas phase moment...

A numerical simulation of a jetting fluidized bed coal gasifier

A numerical simulation study was conducted for a jetting fluidized bed coal gasifier with a conical distributor. It was based on a steady-state model which took account of hydrodynamics, mass heat transfer and reactions in the grid zone, bubble zone and freeboard zone of the gasifier. Temperature of the particles and gas in the jet, compositions in the dilute phase and the dense phase, and some hydrodynamic characteristics were calculated. Effects of some operating conditions such as oxygen and steam flow rates, bed temperature and bed pressure on the temperatures in the jet and gas compositions in the gasifier were numerically investigated.

Prediction of temperature and composition in a jetting fluidized bed coal gasifier

A steady-state numerical simulation model, which takes account of hydrodynamics, mass transfer, heat transfer and reactions, was proposed for the grid zone of a jetting fluidized bed coal gasifier with a conical distributor. Temperatures of the particle and gas in the jet, compositions in the jet and the annulus as well as gas velocity, particle velocity, particle hold-up in the jet were calculated based on this model. The results have shown that the calculated particle temperature in the jet and compositions in the jet and annulus coincide with the experimental ones those were measured in a laboratory scale jetting fluidized bed gasifier.

Analysis of local reactions in a laboratory scale jetting fluidized bed coal gasifier

Abstract A model for coal gasifiers was proposed from the combination of the KuniiLevenspiel bubbling bed model and our own grid zone model. Based on the model, local contribution of individual reaction was analyzed and local concentration profile was predicted in the grid and bubbling zones of a laboratory scale fluidized coal gasifier. The effects of lateral temperature and bed height on CO, H 2 and CO 2 concentration were discussed by comparison with experimental results. The results showed that the numerical predictions are corresponding to the experimental ones. It has been verified that combustion occurs mainly nearby the jet region, steam gasification both in the annulus and emulsion regions and CO 2 gasification mainly in the emulsion region. It is clearly shown that the contribution of the progress of the reactions in the grid zone to total gasification performance is high.

Jet Particle Velocity in a Jetting Fluidized Bed with Conical Distributor

Jet particle velocity and concentration were measured by optic fiber method in a jetting fluidized bed with a conical distributor under various operating conditions. A simplified numerical hydrodynamic model was proposed to estimate the particle velocity and concentration in the jet. Factors affecting the velocity and concentration were investigated. It has been found that the jet height, jet particle velocity and concentration are affected not only by the inlet gas velocity but also by the gas flow from the jet to annulus and the particle entrainment rate from annulus to jet.

Strong metal–support interactions between Ni and ZnO particles and their effect on the methanation performance of Ni/ZnO

A Ni/ZnO system was prepared by coprecipitation and characterized after reduction at different temperatures (350, 400, 450 and 500 °C) using TG-MS, H2-TPR, N2 physisorption, XRD, SEM, H2 and CO chemisorption, TEM, EPR and XPS. H2 and CO chemisorption experiments combined with XRD, SEM and TEM analyses showed evidence for strong metal–support interactions (SMSI) between Ni and ZnO particles, and the degree of SMSI strengthened as the reduction temperature rose. TEM, EPR and XPS studies revealed that the generation of SMSI was attributed to the geometric decoration of Ni particles by ZnO and electron transfer from ZnO to Ni atoms as well as the chemical interaction between Ni and ZnO leading to the formation of a NiZn alloy. Methanation of CO was used as a probe reaction to characterize the effect of SMSI on the catalytic performance of Ni/ZnO. The results showed that SMSI in general had a remarkable suppression effect on the methanation activity, but a light-degree SMSI state facilitated enhancement of the selectivity and stability of CO methanation. Interestingly, the suppressed activity can also be restored with different degrees via re-oxidization and re-reduction treatments under mild conditions. The discovery of SMSI between Ni and ZnO gives a new understanding of the interaction between Ni and supports, and provides a way to tune the interaction between Ni and supports as well as a way to regulate the methanation performance of the Ni/ZnO catalyst or Ni-based catalysts.