直接还原转底炉转速控制系统设计

直接还原转底炉因其工艺独特,能够有效处理冶金污泥粉尘、红土镍矿、复杂难选矿等物料,日益受到治金行业的关注。直接还原转底炉工艺控制最核心部分之一就是还原物料的周期,即必须按照生产工艺的要求的时间完成一个旋转周期,转速控制精度要求高,误差小。文章介绍了直接还原转底炉液压系统原理、控制系统组成、程序设计。     

高炉灰中未燃煤粉含量检测方法研究

为提高高炉灰中未燃煤粉含量的检测效率及准确性,提出了一种矿相分析和化学成分分析相结合的新型检测方法。该方法利用研磨样代替镶嵌样,并用高炉灰化学成分分析对矿相分析进行验证。结果表明:铁与未燃煤粉含量的检测结果标准差分别为1.01%和0.62%,小于统计学的规定要求,说明该新型检测方法准确性良好。     

旋转叶片电加热防冰系统设计与应用

在开展结冰试验时，结冰风洞风扇叶片前缘有结冰风险，影响风洞安全运行。针对大型旋转叶片结冰问题，提出了旋转叶片电加热防冰系统设计方法，研制了大型结冰风洞旋转叶片电加热防冰系统。首先，研制了内置电加热单元和温度反馈的防冰叶片。针对叶片复杂的工作环境，提出一种新的旋转叶片电加热防冰功率计算方法，通过精确测量和方案优化，设计了基于特殊环境的分半式、大尺寸、高线速度、碳刷自动移开/压紧的导电滑环。最后，采用变结构分级温度闭环和试验参数连锁防冰控制策略解决了旋转叶片结冰问题。该系统已应用于大型结冰风洞，运行中加热电流和叶片温度反馈信号传输连续，所有旋转叶片前缘快速加热且温度分布均匀，防冰效果好。     

Innovative focused ultrasound-based sealing method of flexible packaging films—Principles and characteristics

A key process to package goods is the closure procedure. It ensures the good protection against the environment and vice versa. Ultrasonic sealing presents the advantage of converting locally ultrasound into heat, which is optimal for temperature sensitive goods. The disadvantages remain, however, the equipment cost, the noise generation, and the process sensitivity to materials. It is necessary to develop a sealing process to decrease the acquisition cost of the sealing equipment and cover a wide range of polymer films. This paper focuses on a new sealing method based on high-intensity focused ultrasound. The principles and characteristics of this process are discussed and underpinned with experimental results. Both the acoustic and thermal effects of the sealing process are summarized. A study of the process parameter impact on the seam strength in static and dynamic operating is proposed. Low-density polyethylene films with a carrier layer of bi-oriented polypropylene and polyethylene terephthalate are used. A first test bench generates point-shaped seam. The heat generation is recorded with an infrared thermography system. A second test bench, a horizontal form fill and seal machine, produces longitudinal seams. The seam quality is controlled by tensile test and tightness test. A quick heating of the polymer films is found. Point seams and longitudinal seams are successfully generated. The seams behave similarly to the ones generated with ultrasonic sealing process. However, the sealing velocity is limited to 3 m/min. This work provides a summary of the characteristics and principles of the new sealing method in packaging applications.     

关于高炉炉缸长寿的关键问题解析

 高炉长寿化是大型高炉发展的必然趋势,实现高炉长寿的关键在于弄清高炉侵蚀的根本原因。从高炉炉缸侵蚀机理、高炉炉缸象脚型侵蚀原因、高炉炉缸圆周方向侵蚀不均匀性、高炉冷却强度与冷却效率以及高炉炉缸维护技术等5个方面探讨了高炉长寿存在的共性问题,指出高炉炉缸炭砖损毁的本质是碳不饱和铁水对炭砖的溶蚀。具体结果表明,首先,高炉炉缸象脚型侵蚀最严重部位位于高炉炉缸死料柱的根部位置;其次,阐明了直接导致高炉存在不均匀侵蚀的主要原因在于冷却系统的冷却水量和送风系统的风量在高炉周向方向分配不均匀;然后,阐明了冷却系统的作用本质是降低耐火材料热面温度,并提出了高炉冷却强度指数及高炉冷却效率指数;最后,分析了采用无钛矿护炉和钛矿护炉两种模式的高炉炉缸维护技术。     

Potential of plasmonic microreactor for Photothermal hydrogen-enriched fuel production from biomethane

In the present article, a series of coupled computational physics - fluid dynamics models were developed aiming at assessing the feasibility of photothermal synthetic fuel production from biogas (biomethane) and steam blends using plasmonic nanostructure Ag/TiO₂ substrate (each, 0.1 μm in thickness) inside a thermal, momentum and mass transport boundary layer in a microreactor. A chain of partial and complete biogas reforming and water-gas shift reactions were modelled as the dominant chemical reactions responsible for synthetic fuel production from biomethane. Using equilibrium analysis, plausible thermodynamic operating conditions were identified and applied to the computational models. The effect of light wavelength (λ) on the reaction rate, chemical conversion extent, syngas quality, exergy partitioned in synthetic fuel, and composition of gas products were investigated. The results showed that the performance of the microreactor is wavelength-dependent. It was found that the highest production rate for the synthetic fuel was achieved at 580 nm < λ < 620 nm. Within the same wavelength range, the chemical conversion of biomethane to synthetic fuel reached 85% at steam to methane ratio of 3 and the synthetic fuel quality was >2.05, which is suitable for a Fischer-Tropsch process. It was also identified that the syngas quality of the synthetic fuel can be regulated by adjusting the wavelength of the light. The exposure time was also identified to be a critical parameter affecting the performance of the microreactor. For an exposure duration of up to 10 ns, high quality of synthetic fuel >2.05 can be achieved within the optimum wavelength range of 580 nm < λ < 620 nm.     

真空热处理炉布料矩阵优化仿真分析

为了获得更高的加热效率和更好的温度均匀性,采用有限元软件建立了真空热处理炉加热过程仿真模型,并耦合PID算法用于温度控制。通过与实测温度对比,验证了仿真模型的准确性。借助该模型,模拟研究了布料矩阵对两种典型形状零件在真空热处理炉内加热特性的影响。模拟装炉时基于零件几何形状特征,对圆棒形工件采用顺排、叉排和环形排列3种形式,对圆盘形工件采用横排式和竖排式。研究结果表明:尽管零件形状和数量相同,但是随着布料矩阵的变化,加热效率和温度均匀性都会改变。对于圆棒形工件,采用环形排列不仅可以提高内部工件的加热速率,而且相较于叉排式可以将最大温差减小36 ℃;对于圆盘形工件,由水平式改为竖直式布料可以将最大温差由248 ℃减小至171 ℃。     

基于脉冲燃烧控制的退火炉热负荷分配模型

 脉冲燃烧控制技术以其良好的动态响应性、较高的炉温控制精度、较低的燃气消耗及污染物排放水平等优点,广泛应用于各类加热炉。对于立式退火炉而言,常见的加热模型有3种,即比例模型、窄带钢模型、正常模型。生产中操作人员可以根据带钢在加热段跑偏、瓢曲风险选择相应的模型,但上述这3种模型均无法避免因烧嘴频繁开启和关闭导致的辐射管骤冷骤热,进一步引起辐射管变形、开裂,点火电极、控制阀消耗异常以及煤气压力波动大等问题。为了降低烧嘴开启、关闭频次,达到降低烧嘴故障率、减缓辐射管开裂趋势等目的,提出了一种针对脉冲控制的退火炉专用“爬楼梯”式热负荷输出分配模型。通过拟合加热段板温控制器输出值与加热段各列热负荷输出值之间的关系,采用插值法得到加热段热负荷输出分配模型的修正函数,满足了模型计算值与板温控制器输出值相等的要求。通过调整加热段每一列热负荷输出上、下限,使加热段每列热负荷输出呈现“爬楼梯”式分布,实现了立式退火炉低功率加热段入口区域烧嘴不燃烧和出口区域烧嘴一直燃烧的功能。经过测试,在一个完整的燃烧周期内,爬楼梯式分配模型可大幅度降低烧嘴开启和关闭频次。当加热段板温控制器输出为89.6%时,传统模型控制下烧嘴开关频次达到324次,而“爬楼梯”式分配模型仅为32次。