QLM型对撞式气流磨的粉碎机理与应用

ＱＬＭ型对撞式气流磨采用空气动力学原理和射流技术，使压缩空气形成超音速气流，夹带物料随气流加速而获得强大的动能，使相对高速运动的物料在相遇时发生强烈地撞击而粉碎。被粉碎的物料细度为１μｍ，磨入的机械铁小于万分之二。     

变频调速在气流磨微粉生产线中的应用

采用变频控制技术,控制流化床气流磨的分级机转速,可以确保微粉生产线产品质量。     

Comminution and structural changes in a jet mill

The energy of collision in jet mills which grind by means of high-velocity collisions results not only in highly intensive comminution, but certain changes take place in the structure of the material. Even the crystalline particles of so-called rigid materials are known to become microplastic and to accumulate a certain energy when their size is below 1 μm. The energy of collision may remove ions or atoms from the surface of the crystal lattice, producing thereby a mechanochemically activated state. Due to mechanical damage of the crystal structure and to plastic deformation the material may become partly or totally amorphous, and this too may be accompanied by an increase in free energy.Some mineral materials, such as dolomite, limestone, crystalline sulphur and, of the plastics, PVC powder, were ground in a jet mill type Fryma JMRS-80. Our work is part of the research aimed at the utilization of the rich sources of natural high pressure CO₂ occurring in Hungary. Changes in the structure of the material due to comminution were determined by means of differential thermal analysis and X-ray diffractometry.The results confirmed that in addition to producing intensive comminution, high-speed collision affects also the crystal structure of the materials and their internal energy content. If the ground products are destined for further processing, their more active state must be taken into consideration, that is, mechanochemical activation must be taken account of as forming part of the preparatory process.Cooling due to the expansion of the gas entering the milling zone over-compensates for the thermal energy generated there by the friction of the colliding particles. The high milling gas to solid ratio in the jet mill ensures the conduction of any eventual locally arising thermal energy, in contrast to systems in which milling is performed without a gas phase.If a structural change, i.e. disintegration of the pargicles, occurs in course of jet milling, the suggested mechanism is as follows: the mechanical energy introduced into the particles by their collision gives rise in the crystal lattice to oscillations which act by causing a mechanical strain on certain sites (lattice points, bonds) in such a way that local energy accumulation may lead to the disintegration of the particle or to other structural changes [1].Accumulation of the oscillation energy is analogous to the accumulation process of thermal energy, which can be expressed as a temperature rise. The observation of sharp chipped surfaces on jet milled PVC particles, without any sign of local softening, disagrees with the possibility of a local temperature increase.     

用气流粉碎分级法对超细WC粉末研磨

超细硬质合金具有高硬度、高耐磨性的优异性能,保证超细硬质合金的晶粒度小而且均匀的一个关键因素就是以粒度细小、分布均匀的超细WC粉末为原料.在超细WC粉末的制备过程中,对从氧化物还原、碳化后得到的WC粉末的后续处理非常重要,目前普遍采用的是球磨粉碎,但是经过机械方法粉碎后的超细粉末,很难使物料达到所需粒度要求,产品往往处于一个较大的粒度分布范围.文中讨论了一种新型的粉碎技术--气流粉碎分级技术,它兼有气流粉碎和气流分级,使得到的粉末在气流粉碎下细化、在气流分级下减小其粒度分布.气流粉碎分级技术是当今世界原材料加工技术的重要方面,将其应用于超细硬质合金的制备中有很重要的实际意义.     

Effective comminution of diatomaceous earth in a vertical type jet mill

Comminution characteristics of diatomaceous earth have been investigated in a vertical type jet mill of pilot plant scale; the diameter of the chamber of mill is 26.3 cm. Fluidization of the particles in the chamber has been proposed to enhance the comminution efficiency of the jet mill by promoting the effective contacting of powders with compressed air as well as the chamber wall. Effects of the pressures or densities of pulverizing-air and fluidizing-air and comminution time on the mean size of the particles and the rate of comminution have been examined. The statistical analysis of pressure fluctuations in the chamber of the mill has been utilized to predict the characteristics of the vertical-type jet mill taking advantage of the fluidization technique. The particle size and comminution rate have been correlated with the operating variables, respectively.     

The production and anatomy of a tungsten powder jet

A tungsten powder jet is a potential candidate technology for a particle production target in a future high power (i.e. Multi-MW) particle accelerator based facility, such as a so-called conventional neutrino Super Beam, a proposed Neutrino Factory, or a future neutron source. To test the viability of producing a suitable powder jet a few simple experiments were performed using standard pneumatic conveying equipment and the encouraging results are presented.     

Developing a technology for the production of high-strength insulating refractories

Conclusions We developed and tested, in industrial conditions, the main technical parameters for preparing chamotte lightweight refractories with a compressive strength of not less than 10 MPa. The pore formation of the bodies can be attained by using a porous filler of coarse grain-size composition, obtained by expanding fireclays by heat treatment, and with small additions of combustibles. On the basis of the results of these tests we can recommend the development of the technology for introduction into industry.Yu. G. Kruglik took part in the work.Translated from Ogneupory, No. 4, pp. 42–46, April, 1985.     

The use of excess activated sludge from municipal sewage treatment works in production of construction ceramics

The composition of a ceramic mixture for production of brick using excess activated sludge from municipal sewage treatment works is developed. The properties of the samples obtained meet the requirements imposed on ceramic construction products. Assessment of the environmental safety of the suggested material was carried out and the efficiency of utilization of activated sludge in production of construction materials was demonstrated. Translated from Steklo i Keramika, No. 5, pp. 31 – 34, May, 1998.     

Biodiesel production in a jet flow stirred reactor

The rate of biodiesel formation was assessed in a transesterification reactor stirred with a dual jet flow close loop. A blend of 85% of soybean and 15% of sunflower oil, methanol and NaOH were used to study the rate of conversion from vegetable oil to methyl esters. A 9 l cylindrical reactor with conical bottom discharge connected to two centrifugal pumps for fluid recirculation through dual opposite radial jet flows in its upper part was developed for the experiment. The system did not require a heating supply due that the frictional effect inside the recirculation hoses and nozzles produced self heating of the inlet fluid to the reactor. Four different diameters of ejector corresponding to initial Reynolds Number (Re) ranging between 1300 and 6470 were tested to assess the reactor heating profile along with the kinetics of biodiesel formation. Clear performance differences among ejector diameters and Reynolds Number values were observed showing that higher Re result in low relative conversion times along with higher final temperature in the reactor. For 98% of relative conversion to biodiesel, the ejector with Re = 6470 showed 88% reduction in transesterification time with respect to an ejector delivering a Re = 1300 and without requiring any external heat source.     

Dispersion mechanism of nano-particulate aggregates using a high pressure wet-type jet mill

A high pressure wet-type jet mill was employed to disperse nano-particle suspensions. Commercially available nano-particles, fumed silica (SiO₂) of primary particle diameter (d₀) ranging from 7 to 40 nm, alumina (Al₂O₃) of and titanium oxide (TiO₂) of were dispersed in the continuous phase up to viscosity . Ion exchanged water, aqueous ethylene glycol and aqueous polyethylene glycol solutions with molecular weight up to 2 000 000, were used as the continuous phase. Particle size distribution, zeta potential and suspension viscosity were measured under a wide range of process conditions. The smaller the d₀ was, the harder it was to disperse the aggregates. Zeta potential was largely dependent on d₀ at any process conditions and became dependent on η_c for . The energy barrier was evaluated by taking van der Waals attractive forces, electrostatic repulsive forces and dispersive forces into consideration. Cavitation measurements showed a negligible cavitation during the passage through the jet mill; therefore aggregate disruption was modeled for fully turbulent flow. Aggregate disruption occurred in inertia sub-range for and in viscous sub-range for . By balancing mechanical energy with turbulent disruptive energy, a mechanistic model was developed for each sub-range. The analysis of fractal dimensionality showed that nano-aggregates were made up by particle-particle collision in inertia sub-range and orthokinetic cluster-cluster collision in viscous sub-range. The rheological data obtained were expressed according to a modified Casson model.     

The use of basalt rocks from koitashskoe ore deposit in production of building ceramics and filter materials

The possibility of using recycled pyroxene scarn waste in the production of building ceramics is demonstrated. Translated from Steklo i Keramika, No. 1, pp. 17–18, January, 1999.