流化床气流磨粉碎制备超细SiC片晶的实验研究

超细SiC片晶由于其高强度、高弹性模量和导热系数已成为替代价值昂贵、制备技术复杂SiC晶须的理想的增韧材料。本文中通过对流化床气流磨粉碎机理,以及粉碎腔内工质压强与喷嘴个数对SiC颗粒形貌影响的研究,得出工质压强、喷嘴个数等参数对粉碎的颗粒形貌有很大的影响的结论,其中粉碎腔采用高的工质压强以增加粉碎强度。采用两喷嘴以增加颗粒互相撞击的几率是制备片状SiC粉的有效方法;采用流化床式气流磨加多级涡轮分级机的粉碎系统可以制备产品质量较好的多级别超细SiC片晶微粉。     

气流磨粉碎原理及在钛白粉生产中的应用

引言气流磨作为超细粉碎的一种重要设备,广泛应用于非金属矿物及化工原料的超细粉碎,产品粒度上限取决于混合气流中的固体含量,与单位能耗成反比。气流粉碎产品除粒度细以外,还具有粒度分布窄,颗粒表面光滑、颗粒形状规则,纯度高、活性大、分散性好等特点。由于粉碎过程中压缩气体绝热膨胀产生焦耳-汤姆逊降温效应,因而还适用于低熔点、热敏性物料的超细粉碎。下面就气流磨分类及粉碎原理作一介绍。1气流磨分类工业型气流粉碎自40年代问世以来发展很快,目前工业上应用的气流磨有以下五种类型:1.水平圆盘式(扁平式)气流磨2.循环管式气流磨3.靶式气流磨4.对喷式气流磨5.流化床对喷式气流磨2气流磨粉碎原理气流磨的一般原理:将干燥无油的压缩空气或过热蒸汽通过喷嘴高速喷出,高速射流带动物料作高速运动,使物料碰撞,摩擦而粉碎。被粉碎的物料随气流到达分级区,达到细度要求的物料,最终由收集器收集。没有达到要求的物料,再返回粉碎室继续粉碎,直到达到所需细度并被捕集为止。由于喷嘴附近速度梯度很高,因此绝大多数的粉碎作用发生在喷嘴附近。在粉碎室中,颗粒与颗粒间碰撞的频率远远高于颗粒与器壁的碰撞。也即气流磨中的主要粉碎作用是颗粒之间的冲击或摩擦。虽然气流...     

流化床对撞式气流磨对三七的超细粉碎

利用流化床对撞式气流磨对中药三七进行超细粉碎 ,然后分析粉体颗粒的微观形貌、粒度分布及表面积 ,结果表明 ;粉碎效果良好 ,达到了超细粉碎的目的 ,且粒度分布比较均匀     

价廉物美、我国90年代先进产品：LCF系列流化床式超细气流粉碎分级机

价廉物美、我国９０年代先进产品：ＬＣＦ系列流化床式超细气流粉碎分级机ＬＣＦ系列流化床式超细气流粉碎分级机由流化床式气流粉碎机、气流分级机、收集器、除尘器】排风机、空气压缩机、空气净化和干燥装置、电系＃＄Ｊ．％统’＼大部分组成。各项性能参数已达到８０年...     

流化床式气流磨关键技术及其进展

介绍了流化床式气流磨的工作原理及特点,对喷嘴、粉碎、分级等关键部分相关的技术研究进展分别进行了阐述,表明改进和提高喷嘴、粉碎宝、分级机等核心部件的性能和协调各个部分最优化工作能够使流化床式气流粉碎系统达到最佳工作状态,从而提高产品产量和质量。     

控制性气流粉碎技术制备等积球形墨粉

采用自制的控制性气流粉碎机制备等积球形墨粉,通过改变粉碎强度、第一级分级机转速和第一级分级机二次风量来控制墨粉的颗粒形貌,通过改变第二级分级机转速和第二级分级机二次风量来控制墨粉粒度分布的集中性。结果表明,在流化床粉碎强度为0.6 MPa,流化床底部二次风量为86 m3/h,第一级分级机电机变频器频率为17 Hz,第二级分级机电机变频器频率为36 Hz,第二级分级机二次风量为287 m3/h时,制得墨粉的粒度分布最集中,形貌最均匀,球形度最高,此时第二级分级机产量为72.5 kg/h,成品率为79.2%。     

流化床式气流磨制备超微粉的特性

非金属矿深加工是指对原料或其产品进行超细、超高纯、改性、复合等工艺的处理。深加工的非金属矿物除大大拓宽产品本身的应用领域外，还给国家和企业带来可观的经济效益，因此发展非金属矿加工技术得到了世界各国的重视。上海化工机械三厂是化工部粉碎中心、上海市粉体工程中试基地，十多年来长期致力于粉体设备的研制与开发。除了现有扁平式、靶式、对冲式、循环管式等系列气流磨外，近年来成功地开发了流化床式气流磨。气流磨是利用高压气体通过喷嘴产生的高速气流所孕育的巨大的动能，使物料颗粒发生互相冲击碰撞达到粉碎目的。由气体动…     

气流粉碎干燥制备超细磷酸铁锂粉的工艺

采用LNJST-120HT型闭路循环氮气保护气流粉碎分级系统对磷酸铁锂粉进行超细加工、干燥;对粉碎、分级、收集、输送和包装系统的操作参数、设备结构及系统运行过程中出现的流动性、水分增加等问题进行分析探讨,并优化改进;通过加工超细磷酸铁锂粉的工业试验,对改进后的超音速气流磨进行测试。结果表明,控制螺杆加料机和分级机转速分别为62和1 072 r/min,气源压力和温度分别为0.5 MPa和120℃,包装房露点温度控制在-20℃以下,磷酸铁锂粉成品水分含量维持在0.35‰~0.55‰,成品粒径d_(50)=0.8~1.2μm、d_(100)<8μm,产量为200~230 kg/h。     

过热蒸汽动能磨超细粉碎固硫灰的实验研究

采用过热蒸汽动能磨制备固硫灰超细粉,考察分级机转速、粉碎压力和蒸汽入口温度等工艺参数对固硫灰超细粉粒度和产量的影响,分析固硫灰超细粉的形貌特征。结果表明:分级机转速为1 500 r/min时的固硫灰超细粉产量比转速为900 r/min时的减少了34.1%,粒径变小,粒度范围变窄;粉碎压力为0.5 MPa时的固硫灰超细粉产量比粉碎压力为0.25 MPa时的提高了31.8%;蒸汽入口温度为300℃时的固硫灰超细粉产量比蒸汽入口温度为200℃时的提高了46.8%;提高蒸汽入口温度和增大粉碎压力同样会使固硫灰超细粉的粒径变小,粒度范围变窄;在实际生产过程中,粉碎压力与蒸汽入口温度均不宜过高,应根据物料特性控制在合理范围内;经过过热蒸汽动能磨超细粉碎的固硫灰具有良好的形貌特征。     

微粉分级技术研究

通过对ALPINE公司的 2 0 0AFG流化床对喷式气流磨分级系统的分级原理、结构配置、制造工艺性分析 ,对影响成品粉粒度的各参数及变化规律进行了探索。提出了提高成品粉品级 ,扼制大颗粒偶入成品粉 ,提高设备使用寿命与降低气流磨能耗的看法和建议 ,为今后设计新型流化床对喷式气流磨提供了理论依据 ,也将对目前我国粉体工业流行的分级机有关技术指标的完善与提高给予帮助     

Jet mill grinding of portland cement,limestone, and fly ash: Impact on particle size,hydration rate,and strength

While the majority of commercial ordinary portland cement (OPC) is ground using a ball mill or a vertical roller mill, other industries have shown that jet mill grinding can be an alternative approach for grinding materials. This paper investigates the potential application of jet mill grinding for two systems. The first system is a blend of OPC and 15% limestone, and the second system is a blend of OPC and 40% fly ash. It was observed that when jet mill grinding is used, the average particle size of the powders is decreased to approximately 4 μm or less with a narrower particle size distribution than that achieved using ball milling. In addition to evaluating the size and shape of the particles obtained from the jet mill grinding process, this paper focuses on evaluating, using isothermal calorimetry, the effect these changes in particle size and distribution have on the extent and rate of hydration as well as their effect on the compressive strength of cement pastes or mortars.This study also investigated differences between inter-grinding and blending separately ground materials to form an OPC/limestone mixture. Both inter-ground and separately ground OPC/limestone mortars demonstrated an accelerated hydration at early ages accompanied by an increase in early age strength. This appears to be primarily due to the increased surface area of the finer particles that provides more available surface for the hydration reaction. The inter-grinding appeared to be more effective than grinding the materials separately because an improved graded particle size distribution was obtained. The inter-ground OPC/limestone mixture shows accelerated initial hydration at water to powder ratios (w/p, where powder = cement + limestone) of 0.50 and 0.35 when compared with the samples before grinding. At the lower w/p of 0.35, the OPC/limestone mixture appears much more efficient. In the OPC/fly ash mixture, jet mill grinding also accelerates the rate of hydration and strength development.     

气流磨粉磨超细矿渣粉的粉体性能和微观形貌研究

煤炭、粉煤灰及矿渣是用于水泥生产的原料或混凝土的掺合料,而细度是影响粉体材料性能的因素之一。本文以矿渣为材料,利用JFC-5对撞式流态化床气流磨制备了超细矿渣粉,对超细矿渣粉的粉体性能和微观形貌进行了研究。研究表明,气流磨粉磨超细矿渣粉存在粉磨平衡,超细矿渣粉颗粒分布集中,分选机转速过大,得到的矿渣粉体出现团聚现象。     

Degradation of PCDD/Fs by mechanochemical treatment of fly ash from medical waste incineration

The potential of mechanochemical treatment (MC) to degrade PCDD/Fs contained in fly ash was tested via grounding with and without calcium oxide (CaO) under atmospheric pressure. Three types of fly ash collected from medical waste incineration were compared, originating either from rotary kiln fluidized bed multi-stage incinerator using activated carbon spray (FA1, FA2), or a simple stoker incinerator without activated carbon spray (FA3). In test I: CaO to FA1 mixed at ratio of 6-60% was milled at rotational speed of 350 rpm; in test II: FA2 and FA3 without CaO were milled at rotational speed of 400 rpm. The duration of the tests was 2h. The results from the present study indicate that (1) under two test conditions of with and without CaO, PCDD/Fs contained in real fly ash both can be degraded by mechanochemical treatment, (2) under condition of blending with CaO, the degradation efficiency of PCDD/Fs increased with increasing ratio of CaO, (3) the degradation efficiency of PCDD/Fs may increase with rotational speed increasing and (4) the destruction and dechlorination are major mechanism for PCDD/Fs degradation. These results show that mechanochemical treatment is a high potential technology for PCDD/Fs degradation in fly ash.     

超细SiC片晶的制备方法

超细SiC片晶由于其高强度、高弹性模量和高导热系数已成为替代价值昂贵、制备技术复杂的SiC晶须的理想的增韧材料SiC片晶的制备方法有化学制备法和机械制备法。本文中详细介绍了用机械方法制备SiC片晶的设备与工艺过程,阐述了各种制备方法的工作原理及其优缺点,通过对各种制备方法的比较得出采用气流磨与分级机结合工艺是目前制备系列超细SiC片晶有效的和最经济的生产工艺。     

醋酸钙/飞灰复合脱硫脱硝剂热解性能实验研究

为了提高脱硫脱硝效率同时合理利用火电厂产生的飞灰,研究了醋酸钙中加入飞灰制备的复合脱硫脱硝剂的热解性能。对不同条件下制得的醋酸钙/飞灰复合脱硫脱硝剂的热重特性、X射线衍射图谱、比表面积、扫描电镜结果等进行了分析,结果表明:利用醋酸钙和飞灰水合制备的脱硫脱硝剂具有比单纯的醋酸钙和飞灰更大的比表面积;经过900℃煅烧后脱硫脱硝剂孔隙结构最好;脱硫脱硝剂经过900℃煅烧后的热解产物(SiO2、Al2O3、Fe2O3和CaO)有助于脱除烟气中的硫氧化物和氮氧化物。     

The behaviour of Al in MSW incinerator fly ash during thermal treatment

Fly ash from municipal solid waste (MSW) incinerators contains leachable metals, including potentially hazardous heavy metals. The metal content of the fly ash can be reduced by thermal treatment, which vaporizes the volatile metal compounds. After heat treatment of fly ash at 1000 degrees C for 3 h, less metal was able to be leached from the thermally treated ash than from the ash without thermal treatment. Al and Cr were the exceptions. These metals were more soluble in the ash that had been thermally treated. This paper focuses on the leaching behaviour of Al only. Both simple and sequential extraction leaching tests showed that the leachable Al for the heat-treated fly ash is about twice that of the untreated fly ash. The sequential test further revealed that (i) the majority of the leachable Al is associated with Fe-Mn oxides in the fly ash, and (ii) most of the unleachable Al resides in the silicate matrices of the heat-treated and untreated fly ash. Pure chemicals, Al(2)O(3), CaO and CaCl(2), simulating the relevant ingredients in the fly ash, were used for studying their reactions at 1000 degrees C. The aluminum compounds were identified by X-ray Diffraction (XRD). Two new chemical phases produced by the thermal treatment were identified; Ca(AlO(2))(2) and 12CaO.7Al(2)O(3). Their formation suggests a mechanism whereby thermal treatment of fly ash would produce more soluble Al.     

Removal mechanism of phosphate from aqueous solution by fly ash

This work studied the effectiveness of fly ash in removing phosphate from aqueous solution and its related removal mechanism. The adsorption and precipitation of phosphate by fly ash were investigated separately in order to evaluate their role in the removal of phosphate. Results showed that the removal of phosphate by fly ash was rapid. The removal percentage of phosphate in the first 5min reached 68-96% of the maximum removal of phosphate by fly ash. The removal processes of phosphate by fly ash included a fast and large removal representing precipitation, then a slower and longer removal due to adsorption. The adsorption of phosphate on fly ash could be described well by Freundlich isotherm equation. The pH and Ca2+ concentration of fly ash suspension were decreased with the addition of phosphate, which suggests that calcium phosphate precipitation is a major mechanism of the phosphate removal. Comparison of the relative contribution of the adsorption and precipitation to the total removal of phosphate by fly ash showed that the adsorption accounted for 30-34% of the total removal of phosphate, depending on the content of CaO in fly ash. XRD patterns of the fly ash before and after phosphate adsorption revealed that phosphate salt (CaHPO4 x 2H2O) was formed in the adsorption process. Therefore, the removal of phosphate by fly ash can be attributed to the formation of phosphate precipitation as a brushite and the adsorption on hydroxylated oxides. The results suggested that the use of fly ash could be a promising solution to the removal of phosphate in the wastewater treatment and pollution control.     

Effect of curing conditions and ionic additives on properties of fly ash-lime compacts

In the present work the reaction between fly ash and lime in fly ash-lime compacts under water curing and steam curing conditions was studied thoroughly in relation to the processing conditions. Fly ash from different sources were collected, characterized, mixed with lime in different ratios and compacted. The compacts were cured with water and steam separately. The reduction in the free CaO content in these compacts was measured as a function of curing time and curing process. Role of two ionic additives, FeCl₃ and MgCl₂, on the reaction between fly ash and lime was also investigated by measuring the free CaO content. Kinetics of these reactions was studied by determining the reaction order and rate constants with respect to the free CaO content and it was observed that the curing conditions and additives affected the reaction kinetics significantly.     

过热蒸汽制备石油焦粉体的试验研究

利用玻璃厂中工业余热转化的过热蒸汽对石油焦粉体的制备工艺进行现场工业试验,对分级机轴承、除尘器等进行温度测试与分析。结果表明,当过热蒸汽温度为280℃,压力为0.65 MPa,质量流量为2.6 t/h时,测试石油焦粉体产量为5 t/h;粒径为165、38μm的产品通过率分别为100%、61%,出料水分的质量分数为0.2%;分级机轴承和布袋除尘器均处于安全工作状态,蒸汽磨机能连续稳定运转;通过蒸汽磨机制备石油焦,比传统机械磨单位产量能耗节能38.9%,节电80.7%。     

Classifier performance during dynamic fine grinding in fluidized bed opposed jet mills

Dry grinding of particles to sizes below 10 µm can be realized in fluidized bed opposed jet mills. In these mills the energy for comminution is supplied by pressurized gas, which is introduced through focused nozzles. The gas transports the material towards an internal classifier, which separates the fines from the coarse material. The fines are discharged whereas the coarse material is recycled. Within this study special attention is paid to separation at the classifying wheel. Limestone batch grinding experiments were performed in a fluidized bed opposed jet mill equipped with on-line and in-line probes: The particle size distributions (PSDs) of the product flow and the solid concentration below the classifier were determined on-line. The flow field around the classifier was recorded by a high-speed camera and off-line measurements of the mill inventory and its PSD were performed. Our measurements reveal that the solid transport from the milling zone to the classifier and the classifier performance strongly depend on solid concentration. Increasing the solid feed concentration or the classifier wheel speed leads to unwanted accumulation of product-sized particles inside the mill. In particular, we find high solid loadings of up to 1.05 g?g^?1 and strong cluster formation (local zones of high solid concentration) in the vicinity of the classifier blades. Estimated separation efficiency curves of the classifier show a strong “fish-hook effect” which increases with the solid concentration. Our findings are relevant for future process optimization by careful tuning of grinding performance, holdup and classifier speed.