CFD modelling and simulation of an industrial scale continuous fluidized bed roaster

In the present work, computational fluid dynamics (CFD) based modelling of an industrial scale continuous fluidised bed roaster (FBR) has been carried out to study its performance at different operating conditions, so that the sulphide-sulphur content in the product is within 0.4% at the designed feed rate of 39.75 DMT/h. Eulerian-Eulerian multiphase model, considering four granular phases and one gas phase has been implemented to investigate the velocity and mass fraction profile of the particles in the FBR. The heat and species mass balance calculations have been performed external to CFD, by dividing the roaster into several sections. The conversion of ZnS to ZnO at various sections of the roaster has been estimated using reaction kinetics under isothermal condition (1203 K). The heat liberated and possible temperature rise at each section was predicted based on the heat of reaction and sensible heat of the solid and gaseous products. The CFD model was validated with the plant data for a feed rate of 36.5 DMT/h, air flow rate of 65,000 Nm³/h and O₂ content of 21%. The proposed model predicted the sulphide-sulphur content in the product to be 0.4% for the designed feed rate of 39.75 DMT/h, when the O₂ content in the inlet air was increased to 25%.     

Application of Response Surface Methodology to Optimize Roasting Conditions in Cocoa Beans Subjected to Superheated Steam Treatments in Relevance to Antioxidant Compounds and Activities

Roasting is an essential technological process used to produce high-quality cocoa-based products. Response surface methodology (RSM) was employed to optimize the roasting conditions in cocoa beans based on antioxidant compounds (total phenolic, total flavonoids) and their activity (percentage inhibition of 1,1-diphenyl-2-picrylhydrazyl [DPPH] radical and ferric-reducing antioxidant power assay) using two variables: temperature and time. Cocoa beans were roasted at temperature ranging between 150 and 250°C for 10–50 min using superheated steam. The effects of the roasting conditions on the antioxidant properties of cocoa beans were investigated using a second-order central composite design. Results showed that roasting temperature and time significantly affect antioxidants in cocoa beans. Numerical optimization and superimposed contour plots suggested the optimal roasting conditions to be 192°C for temperature with 10 min of roasting time (R ² = 0.99). These conditions can be used for roasting of cocoa beans to produce high-quality cocoa products in terms of antioxidant properties.     

甘肃某微细粒混合铁矿石开发利用研究

甘肃某矿山所产铁矿石矿物组成复杂,主要铁矿物为磁铁矿、赤铁矿和菱铁矿,含量基本相近,其次还有少部分褐铁矿,采用单一工艺无法获得较好的选别指标。根据矿石性质特点,本次研究主要进行了弱磁选-强磁选联合流程、弱磁选-焙烧磁选及工业焙烧-磁选试验。3种方案中以工业焙烧磁选方案的选别指标相对较好,可以获得与酒钢现生产接近的选别指标,达到了利用标准。     

Magnetic properties of ilmenite, hematite and oilsand minerals after roasting

To recover heavy minerals from the Athabasca oil sands tailings, a roasting step is necessary to burn off the residual bitumen. However, most of the previous researchers, using a roasting step, did not seem to be able to separate the Fe-bearing titanium minerals (ilmenite and leucoxene) from the Fe-free titanium minerals (rutile and anatase). An investigation was therefore carried out to study the changes in magnetic properties after roasting to the types of minerals contained in the oil sands tailings. Ilmenite, hematite, and a rutile concentrate (LR Rutile) produced from the oil sands tailings (containing mainly leucoxene and rutile), were used in the study. It was observed that the magnetic susceptibility of ilmenite increased after either oxidation or reduction roasting at some intermediate temperatures and roasting time. For hematite, reduction roasting increased its magnetic susceptibility and oxidation roasting did not seem to have any effect. Reduction roasting of the LR Rutile resulted in an increase in its magnetic susceptibility, and this increase was mainly due to the contaminating Fe-bearing minerals (leucoxene). Upgrading of the LR Rutile was possible either by using low intensity magnetic separation following reduction roasting, or by using high intensity magnetic separation directly.     

炭质板岩型石煤焙烧条件的实验研究

系统地研究了用CaO作为添加剂进行氧化焙烧炭质板岩型石煤的实验方法.实验过程中对矿的焙烧时间、温度、CaO的用量和粒度等影响因素进行了正交实验设计,选出最佳焙烧条件为:焙烧温度910℃、焙烧时间2h、CaO用量7%(重量比)、物料粒度-100目(0.147mm).     

贵州某赤铁矿提铁降钾技术研究

分析了贵州清镇地区赤铁矿为鲕状赤铁矿,主要脉石矿物为硅和铝,采用重选、磁选和磁化焙烧-磁选-反浮选等工艺进行了选矿试验研究。试验研究表明,磁化焙烧-磁选-浮选工艺可以获得较好的指标,精矿铁品位61.27%,回收率87.39%,钾含量降到了0.20%。     

煤气热值对焙烧氧化铝粒度的影响

分析焦炉煤气和发生炉煤气的燃烧特性．从焙烧过程对粒度的影响方面，阐述了加热温度及工艺条件对生成氧化铝粒度的影响。     

鲕状赤铁矿焙烧磁选—酸浸工艺研究

采用焙烧磁选—酸浸工艺处理贵州赫章鲕状赤铁矿,研究了焙烧磁选、酸浸因素对提铁脱磷的影响。试验结果表明,焙烧温度、磨矿细度对提铁脱磷影响较大。随着焙烧温度增加,铁品位和回收率均先增加后降低,磷含量先降低后增加;随着磨矿细度增加,铁品位先降低后增加,回收率先增加后降低,磷含量逐渐降低;采用酸浸可将焙烧磁选精矿中的磷含量降到0.20%以下。当焙烧温度800℃,焙烧时间40 min,加入煤粉量占原矿量5.00%时获得的焙烧矿样,经过磨矿,采用一次粗选、一次精选弱磁选工艺流程,获得含铁59.21%,回收率70.32%,含磷0.43%的铁精矿;磁选精矿采用酸浸,获得含铁60.43%,含磷0.18%的铁精矿。