Tianwei Wu

Flow Characteristic of Two-Phase Bubble Reactor for Slag Waste Heat Recovery

In order to recover the waste heat of molten blast furnace slag, a reactor with top-submerged lance was established. The numerical simulation and experiment study of the flow characteristic in the reactor were conducted. The mathematical model of reactor was established and the Euler-Euler model was employed to simulate the gas-liquid flow in molten slag bath. Meanwhile, the experiment results were obtained and compared with the simulation to testify the accuracy of the established model. According to the bubble behavior in bath, there were four stages: initial expansion stage, bubble detachment stage, freedom lift up stage and bubble broken stage. When the flow field in bath fully developed, the gas fraction decreased with the increasing of bath depth. During injection process, the area near the nozzle and lower the bath would first generate two symmetric heliciform flow regime, and then the flow regime in whole bath would become irregular because of bubble lifting up and rupturing. The gas fraction in bath, the average velocity and turbulence energy of slag would decrease before it increased to maximum and then it would keep fluctuate in a range.

Numerical Simulation and Optimization of Slag Bath Coal Gasification Reaction

Molten blast furnace slag(BFS) is a huge waste energy in iron and steel industry, the waste heat recovery of the molten BFS has attracted more and more attentions in recent years. A new process for generating hydrogen-enriched syngas by the coal gasification using molten BFS as heat carrier is built, based on this, numerical simulation of coal gasification reaction in the gasifier is carried out with finite rate/eddy dissipation model using ANSYS FLUENT, the distribution of gas components in the molten pool is analyzed and the effect of steam coal ratio(S/C) on the composition of syngas is investigated. At the same time, the coal gasification reaction process is optimized by using matrix analysis method based on orthogonal experiment. Results show that the main gas components in the molten pool are steam, H2, CO and CO2. The steam and CO in the molten pool are mainly distributed outside of the bubble, while H2 and CO2 are mainly distributed in the center of the bubble. Meanwhile, the high S/C ratio will reduce the content of CO in the syngas, which is not conducive to the process of coal gasification. After optimization, the gas holdup in the molten pool increases to 9.429%, the turbulent kinetic energy of molten BFS rises to 12.88x10-3m2/s2, and the splashing rate of molten BFS drops to 2.024. The flow of molten BFS and the mixing degree of gas-liquid phase in the molten pool are enhanced, and the effective composition and calorific value of outlet syngas are also improved.

Manganese-based catalyst for NO removal at low temperatures: thermodynamics analysis and experimental validation

Abstract Selective catalytic reduction of nitrogen oxides with loaded urea is a novel method for removing NO under excess oxygen and low temperature conditions. In present work, a comprehensive thermodynamic study for NO removal is executed based on the Gibbs free energy change. This research mainly includes the detailed analyses of NO removal mechanism, the feasibility analyses for manganese as the active element and the experimental study for synthesized manganese-based catalyst (preparation, characterization and performance test). The catalyst in present study can reach 82% NO conversion and near 98% N2 selectivity at 50 °C, which validates the correctness of the thermodynamic calculations.

Energy and exergy assessments of dehydrogenation of propane for propene production

ABSTRACT The energy and exergy assessments of the dehydrogenation of propane for propene production process were performed. The results show that when the reaction temperature rises from 400°C to 1000°C, the range of inlet and outlet exergy is 2268∼2376 and 2265∼2341 kJ/mol C3H6, respectively, and the range of exergy destruction is 6.31∼33.24, 9.93∼35.15 and 3.59∼31.99 kJ/mol C3H6 at 5, 25 and 45°C reference environment temperature, respectively. The range of exergy efficiency at discussed reference environment and reaction temperature is 98.52∼99.84%, and decreases with the increasing of reaction temperature and increases with the decreasing of reference environment.

Energy analysis of chemical looping oxidative dehydrogenation of propane

ABSTRACT Feasibility and energy analysis of chemical looping oxidative dehydrogenation of propane (CL-ODHP) process is performed by thermodynamic method. Results show that Mn2O3/MnO can be used for CL-ODHP, after one redox looping, about 100 kJ/mol energy can be generated. Energy analysis indicates that the process requires 8432.82 kJ/kgpropene external fuel input at reaction temperatures with commercial propane conversion and propene selectivity. And process energy consumption decreases with decreasing of dehydrogenation and regeneration temperatures and increasing of propane conversion and propene selectivity. Recovering waste heat of hot streams from two reactors can cut by nearly 45% energy consumption of the process.

Optimal synthesis of YBaCo4O7 oxygen carrier for chemical looping air separation

ABSTRACT Optimal synthesis parameters of YBaCo4O7 had been done. The X-ray diffraction (XRD) results show that YBaCo4O7 samples are all single phase. The Scanning electron microscope (SEM) results indicate that with increasing calcination temperature, calcination time, and decreasing cooling rate, grain transformed from porous agglomerates of sphere or sphere-like to agglomerates of irregular polyhedron, as well as the grain size increased. YBaCo4O7+δ with oxygen storage capacity of 102.52 wt.%, maximum rate of intaking oxygen temperature of 339.7°C, and maximum rate of releasing oxygen temperature of 369.8°C can be obtained by the optimal synthesis parameters, calcination temperature of 1100°C, calcination time of 30 h, air-cooling, and solid-state reaction method.