| Rotary Hearth Furnace(RHF) has showed a good development momentum in processing of metallurgical dust and environment protection, and it has a great market prospects. In this paper, from the perspective of combustion characteristic of the gas in the RHF and emission characters of the bed, through numerical simulation, explored the influence rules of the related parameters of the RHF and precipitation characteristics of material layer on temperature field, flow field and concentration field in the RHF, all of this are aiming at laying a theoretical foundation for the design and optimization of the RHF.A mathematical model of the gas combustion in the RHF was established based on a RHF owned by a company. First of all, the influence of the related structure parameters of the RHF and the relevant technological parameters of the inlet gas was explored on the temperature field, flow field and concentration field in the RHF, and after comparison, parameters combinations was obtained. Secondly, emission characters and weight-loss characters of the carbon-containing pellets was explored through the experiment in different carbon oxygen mole ratio, different reducing agent and different heating rate. Through the theoretical calculation and data fitting, based on the experimental data, the relation equation in the direct reduction was established between CO production rate and heat absorption rate of the material layer and the furnace bottom angle. Lastly, CO from layer and absorbed heat of the layer was added into the FLUENT in the form of source item to explore the temperature field, flow field and concentration field in the RHF during the direct reduction of the layer. The following conclusions were obtained.(1) Through numerical simulation has confirmed the suitable mixed-gas combustion model and radiation model in the RHF are Non-Premixed Combustion Model and DO radiation model. Temperature air highest in reduction section, unload section are second, and preheating section are lowest in the RHF. Along the rotation direction of RHF, gas velocity decrease on the bottom and pressure increase in the RHF.(2) Geometry parameters of RHF, such as burner height(h) and inclination angle(a) and barricade height(H), have a great effect on temperature field, flow field and pressure field. When h =0.6m or a=-16°, there has a local overheating in the reduction section. Barricades can reduce mutual interference of temperature and pressure between sections, and the lower barricades, the higher pressure in unload section and reduction section. When h=0.8m, a =16° and H=0.6m, temperature field, flow field and pressure field in hearth is more reasonable.(3) Air excess coefficient(n), air preheating temperature(T) and gas flow rate(Q) have a great effect on temperature in RHF as well. By comparing the calculated results of n=1,1.05, 1.1 and 1.15, when n=1.05, temperature in furnace is highest. By comparing the calculated results of T=300K, 573 K, 673 K and 773 K, the higher air preheating temperature the higher temperature in furnace, and when air preheating temperature increase 100 K, gas temperature increase about 10 K on outlet. The more of the gas flow rate the higher temperature in furnace as well.(4) Boudouad reaction in Carbon-containing pellets starts at about 810?, and C/O almost have no effect on it. For the carbon-containing pellets of iron ore concentrate with coke, C/O=1.2 is more than C/O=1 in final weight loss of pellets. When C/O=1.0, the faster the heating rate the less in final weight loss of pellets. And reducing property of cokecarbon-containing pellets are better than coalcarbon-containing pellets in same condition.(5) CO generated by material layer are mainly concentrated on the outer edge of the furnace bottom. O2 concentration is very low in unloading section and reduction section, which are contributing to preventing secondary oxidation of metal reduced in pellets. Because of combustion of CO generated by layer and unburned CO in heating section and unload section with excess air, high-temperature area in reduction section expanded to heating section. |
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