To optimize existing iron ore reduction processes or to develop new ones, it is necessary to know the reduction kinetics of the iron ore of interest under the relevant operating conditions. In this work the reduction kinetics of hematite fine iron ore was studied for industrial-scale processes using the fluidized bed technology. Especially designed batch tests were performed in a laboratory-scale fluidized bed reactor fluidized with H 2 , H 2 O, CO, CO 2 , N 2 at atmospheric and elevated pressures to simulate the relevant process conditions. To obtain the reduction rates and the degree of reduction, the concentrations of H 2 O, CO, and CO 2 in the outlet gas were analyzed by FT-IR spectroscopy.Preliminary reduction tests showed a strong effect of the sample weight on the reduction rates, especially in the early stages of reduction. The optimum sample weight was determined by partly replacing the hematite with silica sand. Additionally, the silica sand provided a constant and stable flow pattern throughout the reduction tests. The effects of temperature, gas composition, particle size and pressure on the rates of reduction were tested and discussed.Rate analysis showed the existence of two phases with different rates during the reduction tests. Additional investigations (microscope analysis, SEM) demonstrated that in the first phase the rates were controlled by mass transport in the gas phase and in the second phase by the reduction process within the small grains of the iron ore particles.KEY WORDS: iron ore reduction; high temperature fluidized bed; reduction kinetics; elevated pressure; H 2 -CO gas mixture.

The aim of this work was to develop a model for the iron ore sintering process with special focus on heat front propagation through the packed bed and to provide a powerful tool ("SinterSim v1.1") for the simulation of the sintering process. Special interests were paid to the sub-models of fluid flow through the packed bed, oxidation of carbon monoxide, coke combustion, melting and solidifying of the bed material and the thermal decomposition the of ore components. Base case calculations were done showing very good agreement compared to values gained in test runs of the sintering process in a sinter pot. Numerous calculations with varied parameters were carried out to evaluate the behavior of the sintering process in means of a sensitivity coefficient for the specific variation. For duration of the sintering process and height of the sintering zone the most sensitive parameters turned out to be the mean diameter of the sinter mix material, void fraction inside the packed bed, the amount of coke breeze in the bed, the humidity of the green sinter mix and the amount of Fe 2 O 3 in the ore.

Gasification of biomass is an attractive technology for combined heat and power (CHP) production. A dual fluidized bed steam gasifier is in commercial operation at the biomass CHP plant in Guessing/Austria since 2002. For circulating fluidized bed applications the bed material consumption is economically crucial. Thus, cyclones for circulating fluidized beds need to be designed properly. Some erosion and caking in the cyclone of the gasifier could be observed with increasing hours of operation. The influences of these effects as well as the influence of the solid circulation rate between the two units on the separation efficiency were investigated by fluid-dynamic investigations using a scaled cold model. The results show that due to erosion and caking elutriation rates are increased, especially for smaller particles. However, the cyclone achieves fractional separation efficiencies of more than 99.9%.

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A process is under development for the steam gasification of biomass to produce a hydrogenrich gas for use with a fuel cell to generate electricity on a local scale. A pilot plant is currently under construction in southern Italy operated with a circulating fluidized bed, and to predict the fluid dynamic conditions within the plant, a cold laboratory rig was built according to existing scaling laws, and experimental studies were carried out. In this paper, we present the experimental results concerning the solids residence time of particles introduced into the system and the particle mixing in the "gasifier" section of the model. Both parameters are of fundamental importance for the operation of the pilot plant as they determine the performance of the gasification process. It is shown that the biomass particles spend sufficient time in the gasifier to be fully gasified, and an equation is derived to predict the mean residence time of the biomass particles as a function of the dimensionless mass turnover of the circulating bed material. In addition, it is shown that the biomass particles are well mixed within the circulating bed material. One reason for this is a result of the geometric design of the apparatus.