Influence of milling media on the structure and agglomeration behaviour of some hardmetal powder

This paper presents the influence of milling media on the structure and morphology of WC–Co powders for sintered tools. WC–Co powders have been milled in two different organic media, acetone and isohexane. The characterisation of the as-milled samples has been done by X-ray diffraction, scanning electron microscopy (SEM) and differential scanning calorimetry. The mean crystallite size decreases with milling time for the samples processed in acetone, while in the case of isohexane, the crystallite size stays at a relatively constant value when increasing the milling duration. The calculated mean crystallite size is below 50?nm for any milling duration, with larger values for acetone (16–46 nm) as compared to isohexane samples (10–12 nm). The SEM revealed that the dried powder is composed of agglomerated submicronic particles, and at high magnification, the presence of nanoparticles is noticed. The density of the aggregates was linked to the polarity of the solvents, which influences the sedimentation kinetics.     

用活性炭回收挥发性有机溶剂的研究进展

简要介绍了挥发性有机溶剂的危害、回收意义和常见的回收技术。重点阐述了用活性炭回收挥发性有机溶剂的技术,就最常见的汽油回收炭、丙酮回收炭、丁酮回收炭为例,阐述了活性炭在溶剂回收方面的研究进展。     

高浓度丙酮VOCs高温预热近极限贫燃预混火焰特性的数值分析

为进一步对一种丙酮挥发性有机化合物（VOCs）焚烧炉进行设计优化和运行参数调节,本文对其在不同的燃料当量比、预热温度下的火焰特性进行了数值模拟,分析了其绝热火焰温度、着火延迟时间、火焰传播速度和一维火焰产物分布特性。研究结果表明：典型当量比（约0.113）下的绝热火焰温度为850~900℃,属于中低温燃烧,绝热火焰温度随预热温度和当量比（0.06~0.4）的升高均线性升高。预热温度和化学当量比对着火延迟时间的影响十分敏感。在其典型贫燃条件下,层流火焰传播速度随预热温度升高呈指数函数关系增大,随化学当量比增大而缓慢升高,且其层流火焰传播速度不超过150cm/s。反应过程首先发生丙酮的分解和部分氧化,并持续时间较长,仅当混合物的温度升高一定程度后才发生较剧烈的CO氧化。     

添加有机前体物质对发酵生产HA的影响研究

研究了摇瓶发酵过程中添加物对兽疫链球菌Streptococcus zooepidemicus发酵生产透明质酸的影响。结果表明：在发酵5h时,装液量80mL／500mL,转速300rpm,添加1．0％的丙酮可以使HA产量提高23．25％。丙酮可以作为一种有效的添加物应用于HA的生产。     

电伴热系统在苯酚丙酮装置氧分析仪的应用

介绍了苯酚丙酮装置氧分析仪使用的电伴热系统的结构及原理,分析比较了蒸汽伴热和电伴热系统的经济效益、维护量及使用效果;阐述了电伴热系统在苯酚丙酮装置氧分析仪使用效果、使用注意事项及优势。     

非晶态Ag表面修饰NiFe2O4的制备及对丙酮气体的气敏性能

采用微波诱导低温固相反应法合成NiFe2O4纳米粉体,并通过浸渍法在其表面修饰Ag,通过X射线衍射分析(XRD)、扫描电镜(SEM)和X射线光电子能谱(XPS)研究修饰前、后粉体的结构及形貌,并对修饰不同含量Ag的旁热式气敏元件的气敏性能进行测试.结果表明:表面修饰的Ag为非晶态,能够有效阻止NiFe2O4纳米颗粒的团聚及长大,当表面修饰1.5％Ag后,NiFe2O4气敏元件的最佳工作电压为4.5 V,对丙酮气体具有较高的灵敏度,达到43,且响应(l s)和恢复(～l0 s)时间快,优于直接固相反应法掺杂1.5％Ag所得的NiFe2O4气敏元件的气敏性能.     

高效液相色谱法测定棉籽仁中棉酚的含量

目的：建立棉籽仁中棉酚含量的高效液相色谱测定方法。方法：采用ODS-C18 色谱柱(4.6mm × 200mm,5μm),柱温25℃,流动相为甲醇- 体积分数1% 磷酸溶液(85:15,V/V),流速1.0mL/min,检测波长235nm。结果：棉酚质量浓度在1.9～34.9μg/mL 范围内线性关系良好;棉酚的加标回收率为97.8%～100.3%,RSD值为0.4%～1.2%。结论：此法操作简便、快速、灵敏、准确,样品处理简便易行,适于测定棉籽仁中棉酚的含量。     

Destruction and removal efficiency of PICs by various iron ores during sintering-exploratory testing

Worldwide,iron ore sintering is the largest industrial single source of dioxin emissions^1-3.Conversely, some ores may help in reducing emissions,because of their aptitude of（a） adsorbing and（b） oxidising or decomposing TOC and dioxins^4,5.Such dioxin abatement abilities were tested for five types of ores,representing major ore origins（Australia,Brazil,and South Africa ）,minerals（magnetite,haematite,goethite,pisolite ）,and properties,e.g.porosity,and Loss on Ignition（LOI） values.In total,11 exploratory experimental runs were conducted on iron ores,to test the oxidation in air of four different organic trace test substances:acetone, chloroform,n-hexane,and toluene contained in a test gas were led simultaneously over the ore over a preestablished temperature program.Each test comprehends a first part with a programmed temperature rise,a brief soaking period at the temperature maximum（>400℃）,and a ballistic cooling part.The concentration of the four organics is continuously monitored by Mass Spectrometry（MS） operating in a full-scan mode（m/e < 100）. Exploratory experiments allowed differentiating the ores tested according to the Destruction & Removal Efficiency（DRE） attained.To check the results the products of oxidation in the effluent were sampled on Tenax and identified.Also,the dioxin load remaining on several test residues was examined and found to be quite limited （pg I-TEQ/g）.     

变压精馏分离甲醇-丙酮的工艺模拟及优化

采用Aspen Plus软件,以塔釜能耗为目标,以甲醇、丙酮纯度为约束函数,对双效变压精馏分离甲醇-丙酮工艺过程进行模拟。分析了操作压力、理论板数、回流比、进料位置和进料温度等参数对精馏过程的影响。确定了最优工艺参数：减压塔操作压力40 kPa,理论板数37,回流比2.4,进料塔板数26,进料温度25 ℃;常压塔理论板数30,回流比4.2,进料塔板数23。减压塔所得甲醇质量分数为99.0%,常压塔所得丙酮质量分数为99.7%。对比变压精馏和萃取精馏过程,变压精馏更容易得到高纯度丙酮产品,节能约13.4%。模拟结果对工业设计和设备改造具有一定指导意义。     

Mg/Al复合氧化物催化丙酮和碳酸二甲酯合成乙酰乙酸甲酯

利用先共沉淀后水热处理的方法制备出水滑石前体,将其焙烧后,得到具有不同Mg/Al摩尔比的复合氧化物,并借助电感耦合等离子原子发射光谱、XRD、CO2-TPD和氮气吸脱附等手段对其进行表征。结果表明,Mg/Al摩尔比对催化剂的结构和碱性质有较大的影响,并且在催化丙酮和碳酸二甲酯合成乙酰乙酸甲酯的反应中,其比单纯的氧化镁和氧化铝表现出了更高的催化活性。进一步的研究表明,在该反应中是复合氧化物的中强碱性位起催化活性的作用,当Mg/Al摩尔比为2时,催化剂具有最高的活性。此外,重复性实验表明,这些催化剂具有较好的稳定性和重复使用性。