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Determination of the rate equation df carbide formation from reduced iron and formulation of mathematical model for the reaction in fluidized bed

还原铁形成碳化物的速率方程 df 的确定和流化床反应数学模型的建立

基本信息

批准号：
10305056
负责人：
IGUCHI Yoshiaki
金额：
$ 8.06万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

In pressurized conditions of 0.1-0.6MPa, 0.15-0.21mm particles of a hematite ore and a limonite ore were reduced in H_2-H_2S mixtures with α_s=Q.1-0.6 and carbupzed in CO-H_2-H_2S mixtures. In the study using the hematite ore,(1) we have gravimetrically measured the carbide formation rate from reduced iron in the reaction gas of 0.1-0.6MPa at 500-700ーC, and formulated the rate for the carbide formation and determined the rare parameters.(2) We have studied the carbide formation in a laboratory scale fluidized bed in the reaction gas of 0.1-0.6MPa at 873K by using the hematite ore, and(3) we have tried to magnetically separate the iron carbide from gangue materials after the limonite ore blocks were reduced and carburized to cementite. We describe the results of the experiments blow.(1) We have concluded that the carbide formation rate nearly obeys the integrated rate equation for the first order reaction -ln(1-f_θ)=g(p_bT)t as well as the rate at the atmospheric pressure does it. The c … More arburization rate g(p_bT) obtained from the gradient in -ln(1-f_θ) versus t plot and the dependency of g(p_bT) on the composition, total pressure p_r and temperature T was investigated. As a result, we have found out that the value of g(pb_T) is piortional to the power of 1 at 600℃ and 1.4 to 1.5 at 700℃ to Pr. Based on the dependence, we have concluded that the rate controlling step is the dissociative adsorption step of CO at 600℃ but it gradually shifts to the mixed control of the dissociative adsorption step and the adsorbed oxygen removing step by CO and H_2. From the elementary reaction mechanism, an overall rate equation was derived for the carbide formation and the rate parameters were determined, from which the calculation of the carbide formation rate was enabled with the fluidjzed bed. The influence of reduction and carburization temperature on the carbide formation was also investigated.(2) We have measured the carbide formation rate from reduced iron in a fluidized bed with the reaction gas under the pressurized condition. Carbide formation curves were established from the composition of samples, which were taken every 600-900s interval and determined by XRD and carbon analysis. Also for the bed, the curves nearly obeyed the integrated first order reaction rate equation and the value of g(p_bT) was obtained as the gradients in -ln(1-f_θ) versus t plot. And we found that the g(p_bT) is proportional to the 1 power to p_r at 600℃. Furthermore, by analyzing the composition of the outlet gas from the fluidized bed, we have determined the relative contribution to the total removal of the adsorbed oxygen ; by O(ad)+H_2→H_2O and O(ad)+CO→CO_2. As a result, the oxygen removal for carbide formation is mainly based on the former reaction and the oxygen removal for free carbon is mainly based on the latter reaction. Furthermore, we proved that pressurizing enhances the carbide formation rate. We have proposed two reaction models, I.e. plug flow reaction model and bubble assemblage model and indicated the applicability of the models to the carbide formation curves. These models can contribute thescale up of the carbide formation in fluidized bed.(3) We produced iron carbide by reducing a limonite ore block and carburizing the reduced iron. After pulverization, we tried to separate the iron carbide from gangue materials by magnetic separation method. As a result, we have found out that we can hardly separate the gangue materials, which contains at most 8 mass% gangue materials, from iron carbide even by using magnetic separation method. Less

在0.1-0.6MPa的加压条件下，0.15-0.21mm的赤铁矿和褐铁矿在α_s= 0.1 -0.6的H_2-H_2S混合气体中还原，在CO-H_2-H_2S混合气体中碳化。在以赤铁矿为研究对象的研究中，（1）用重量法测定了还原铁在0.1-0.6MPa、500-700 ℃的反应气体中的碳化物生成速率，并对碳化物生成速率进行了公式化，确定了稀有参数。(2)在实验室规模的流化床中，研究了赤铁矿在873 K、0.1-0.6MPa的反应气体中碳化物的生成。（3）褐铁矿块经还原、碳化成褐铁矿后，尝试从脉石中磁选出碳化铁。我们描述了实验的结果。(1)结果表明，碳化物的生成速率与常压下的碳化物生成速率一样，几乎服从一级反应积分速率方程ln（1-f_θ）=g（p_bT）t ...更多信息由In-ln（1-f_θ）-t曲线求得渗碳速率g（p_bT），并研究了g（p_bT）与成分、总压p_r和温度T的关系。结果表明，在600℃时，g（pb_T）与Pr的1次方成正比，700℃时，g（pb_T）与Pr的1.4 ~ 1.5成正比。600℃时的速率控制步骤为CO的解离吸附步骤，但逐渐转变为解离吸附步骤和CO脱除吸附氧步骤的混合控制，H_2。从基元反应机理出发，导出了碳化物生成的总速率方程，确定了速率参数，并由此计算了流化床中碳化物的生成速率。研究了还原温度和渗碳温度对碳化物形成的影响。(2)在加压条件下，测定了还原铁在流化床中与反应气体反应生成碳化物的速率。碳化物形成曲线由样品的组成建立，每隔600- 900 s取样，并通过XRD和碳分析测定。在床层中，反应速率曲线基本上服从一级积分速率方程，g（pbT）值可用-ln（1-f θ）-t曲线的梯度表示。发现在600℃时，g（p_bT）与p_r的1次幂成正比。此外，通过分析流化床出口气体的组成，确定了O（ad）+H_2→H_2O和O（ad）+CO→CO_2对吸附氧总脱除的相对贡献。因此，碳化物形成的除氧主要基于前一反应，游离碳的除氧主要基于后一反应。此外，我们证明了加压提高碳化物的形成速率。提出了两种反应模型，即塞流反应模型和气泡聚集模型，并指出了这两种模型对碳化物形成曲线的适用性。这些模型对流化床中碳化物的形成有一定的促进作用. (3)我们通过还原褐铁矿块并将还原铁渗碳来生产碳化铁。煤矸石粉碎后，尝试用磁选法分离其中的碳化铁。结果，我们发现，即使通过使用磁性分离方法，我们也几乎不能将包含至多8质量%脉石材料的脉石材料与碳化铁分离。少