Dynamic modeling of a multiple hearth furnace for kaolin calcination

A dynamic model of a multiple hearth kaolin calciner has been developed and is presented in this article. This model describes the physical‐chemical phenomena taking place in the six furnace parts: the solid phase, gas phase, walls, cooling air, rabble arms, and the central shaft. The solid phase movement, in particular, is described by a novel mixing model. The mixing model divides the solid bed in a hearth into volumes and the distribution of their contents, after one full central shaft rotation, is identified by the pilot experiments. First, the model is validated by the industrial data, and then the dynamics of the multiple hearth furnace is studied by introducing step changes to the three manipulated variables: the feed rate, and the gas, and air flows supplied. The responses of the gas phase temperature and solid bed component profiles are analysed and the results are discussed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3683–3698, 2015     

注塑成型工艺试验优化设计

针对注塑成型工艺中存在的缺陷,引入正交试验设计方法,进行模具结构和工艺参数的优化设计。以模具温度、保压压力、保压时间和模内冷却时间作为影响因素,以体积收缩率、缩痕指数和熔接痕长度作为评估指标,通过利用Moldflow软件模拟熔体在型腔内的流动,得到各工艺参数影响制品成型质量的趋势图。通过正交试验设计分析,得到各工艺因素对体积收缩率、缩痕指数和熔接痕影响的程度,结合极差分析、方差分析法综合比较各组试验模拟结果,获得最优化的工艺参数组合。     

Ablation behavior of ZrB2–SiC protective coating for carbon/carbon composites

Ablation behavior of ZrB₂–SiC protective coating for carbon/carbon composites during oxyacetylene flame test at 2500 °C was investigated by analyzing the microstructure differentiation caused by the increasing intensity of ablation from the border to the center of the surface. After ablation, a continuous SiO₂ scale, a porous SiO₂ layer inlaid with fine ZrO₂ nuclei, and a continuous ZrO₂ scale respectively emerged in the border region, the transitional region, and the center region. In order to investigate the ablation microstructure in the initial stage, the sub-layer microstructure was characterized and found to be mainly formed by coral-like structures of ZrO₂, which showed huge difference with the continuous structure of ZrO₂ on the surface layer. A kinetic model concerning the thickness change induced by volatilization and oxidation during ablation was built to explain the different growth mechanisms of the continuous ZrO₂ scale and the coral-like ZrO₂ structure.     

二步法低温制备六铝酸钙/镁铝尖晶石复相陶瓷

以白云石和工业Al(OH)3为原料,采用水热合成和低温煅烧二步法工艺制备六铝酸钙-镁铝尖晶复相陶瓷,探索了水热处理温度对前驱体性能及六铝酸钙/镁铝尖晶石复相陶瓷物相组成和形貌的影响。结果表明:200℃水热处理后的前驱体中,板状三水铝石转变为多孔薄片状薄水铝石;前驱体高温分解后可为复相陶瓷的生成提供高活性原料和六铝酸钙片状形貌的生长空间;二步法工艺可使烧成温度降低100℃以上。白云石添加量为13%时,配料经200℃水热、1 400℃煅烧3 h即可制备出主晶相为六铝酸钙和镁铝尖晶的复相陶瓷,六铝酸钙形貌发育完整,呈交叉片状存在。复相陶瓷的体积密度为1.56 g/cm3,气孔率为61.5%,孔径分布在0.2~1.1μm之间。未水热处理配料于1 500℃保温3 h,制备出六铝酸钙/镁铝尖晶石复相陶瓷,六铝酸钙和镁铝尖晶石晶体衍射峰强度较弱,六铝酸钙片状形貌发育不完整。     

中低温固化高性能环氧树脂TGDDM体系性能研究

为解决二氨基二苯甲烷四缩水甘油醚(TGDDM)成型过程中高温固化引起的内应力增加、不易操作和低温固化所带来的低热稳定、低力学强度的问题,采用中温固化剂(JH)和高温固化剂(DDS)同时固化TGDDM,考察了三元复配体系的固化行为、力学性能及热稳定性。结果显示,当共混体系中TGDDM,DDS,JH的组成比例为100∶10∶30(TSJ–3)时,体系初始固化温度下降至50℃左右,且TSJ–3体系表现出最佳的弯曲性能和最好的热稳定性,满足了中低温固化,同时具有出色的热稳定性和较好的力学性能的要求。     

聚丙烯切片样品粒度与用量对其熔融曲线的影响

在差示扫描量热分析过程中,通过改变样品粒度及用量,考查了对聚丙烯切片热行为的影响。结果表明:样品粒度变大或样品用量增加会导致熔融峰顶温度升高,同时会使熔融焓有轻微变化。因此在仪器的灵敏度可满足的情况下,为得到切片真实结晶结构参数的有效方法是减少样品用量(例如5 mg以下)。     

自调温相变木塑复合材料挤出工艺与性能研究

将相变材料引入木塑复合材料中,研究了复合材料的挤出工艺以及加热和冷却过程中复合材料表面温度随时间的变化关系,分析得出相变材料的加入减缓了温度的变化速度,使得木塑复合材料具有储能的作用。     

鱼类低温保鲜研究进展

低温保鲜是鱼类最常用的保鲜方法,如何保证鱼类在长时间内保持新鲜度、防止腐败以及营养物质的变质,一直是人们研究的热点。这其中用到了很多物理或化学原理或设备,其发展也与化工化学等工业的发展密切相关。本文以鱼类低温保鲜领域的专利申请为研究基础,从专利申请量、专利申请人以及专利研究技术内容等方面分析了国内外鱼类保鲜领域的研究内容以及发展演变过程,梳理了该领域的技术发展脉络。     

高铁铝土矿低温磁化焙烧-磁选工艺试验研究

基于我国存在大量高铁铝土矿的现状,对高铁铝土矿进行了低温磁化焙烧-磁选工艺的研究。经过大量的试验,研究了焙烧温度、焙烧时间、煤矿比以及磁场强度、给矿时间、液固比对实验结果的影响。该工艺与高温处理高铁铝土矿的工艺相比,大大降低了能耗,节约成本,同时能综合利用此类矿中的铁和铝,取得了较理想的效果。     

基于STM32的无线温湿度控制器

以STM32控制器为控制核心,进行温湿度控制器的设计,给出了部分主控电路和RS232收发电路。通过温湿度传感器检测温度和相对湿度,根据数字增量式PID控制算法控制环境温湿度接近给定值。通过系统软、硬件联机调试,该控制器实现了高精度的温湿度控制与无线传输,且工作可靠。