Yue Guangxi

Catalytic oxidation and kinetics of oxidation of coal-derived pyrite by electrolysis

Abstract The catalytic oxidation of coal-derived pyrite (CDP) into SO 4 2− and Fe 3+ and kinetics of oxidation of coal-derived pyrite by electrolysis were studied in a batch reactor. In this paper, the influence of electrolysis conditions on the pyrite conversion rate, such as particle size, electrolysis potential, reaction time, etc. was reported. It is obvious that the rate of conversion of pyrite ( C r ) increases with the increase of the electrolysis potential, reaction time, temperature, acidity and the concentration of catalyst (MnSO 4 ), but decreases with the increase of concentration of pyrite. The experimental data show that the reaction is marching with shrinking core model. The reaction-controlling step was found to be the reaction between Mn 3+ and pyrite. The active energy for oxidation of CDP into SO 4 2− and Fe 3+ by electrolysis is 29.6 kJ/mol.

A six-parameter model to predict ash formation in a CFB boiler

Abstract Because of the large fraction of ash in bed inventory, the ash formation data, i.e. ash initial size distribution, fragment and attrition characteristic, are of significance to determine the design parameters of a CFB boiler. A laboratory method was developed earlier for determining the coal ash formation characteristics with the ash formation database for six coal types. The behavior of ash particles mainly depends on the mechanical strength and the fragmentation and attrition resistance. Analysis of this ash formation database showed that the distribution of the ash mixture from a narrow coal size fraction is of bimodal nature, with both the fine soft component (earth ash and dust ash) and coarse hard component (stone ash) following the Rosin–Rammler (R–R) distribution. This paper presents a six-parameter model to predict the ash composition and the size distribution of the ash components of a coal boiler. The cumulative size distribution curves of earth ash and stone ash could be calculated by using the model, and the results are in good agreement with the experimental data.

Characterization of Pressure Signals in Fluidized Beds Loaded with Large Particles Using Wigner Distribution Analysis: Feasibility of Diagnosis of Agglomeration

Abstract An experimental verification is reported on the early predicting index of agglomeration in bubbling fluidized bed. Coarse quartz sand, which has the same density but larger diameter than the bed material, was used to simulate the initial agglomerated particle. Wigner distribution was used to analyze the pressure fluctuation of the tested bed, and the average amplitude of local domain frequency (LDF) and local peak weighted average frequency (LPWA) under different operating conditions were measured and compared. The results showed that the LDF is sensitive to the agglomeration phenomena and had quick response to the incipient agglomeration in fluidized beds. It can be concluded from the results that these two parameters could be taken as the characteristic indexes to the agglomeration in fluidized beds.

Effects of the Secondary Oxygen Injection on the Performance of a Staged-Entrained Flow Coal Gasifier

In a staged entrained flow coal-slurry gasifier, the secondary oxygen was injected into the gasifier in order to protect the refractory in the dome region, to improve the mixing process as well as gasification performance. Based on a proposed 3-D numerical model, simulations were conducted for the staged gasifier at different mass flow rates of the secondary oxidizer. The characteristics of the gasification flames were analyzed as well as the influence of the secondary flow on the flow field of the staged gasifier. As the mass flow rate of the secondary oxidizer decreases, the secondary gasification flame curves up according to the backflow region and wall temperature increases. When the mass flow rate of the secondary oxidizer is less than 10% of the total oxidizer mass flow rate, there is an obvious change of the turbulent mixing in the staged gasifier.