GTSP重钙工艺减少反应料浆含水量的初步研究

1 引言 我国耕地严重缺磷的面积所占比例高达2/3,而目前施肥的磷/氮比例又远远低于国际平均水平,如此的比例失调将严重影响农业增产.在当前施用的磷肥中,普钙和重钙占了很大的比例.由于重钙是用磷酸而非硫酸酸解磷矿,所以不含硫酸钙杂质,有效五氧化二磷的含量也由16～21%提高到45～52%,肥效比普钙提高两到三倍.为此国家"八五"重点项目引进了Hy dro GTSP工艺2×40万吨/年重钙装置.该装置于1999年3月试车以来难以达到满负荷生产. 作者通过对生产工艺各环节的分析,指出反应料浆含水量偏高是影响装置生产负荷的主要因素.料浆中水分的重要来源之一是二次球磨.     

Milling of Organic Solids in a Jet Mill. Part 2: Checking the Validity of the Predicted Rate of Breakage Function

The particle size distribution of fine chemicals in the solid state, like active pharmaceutical ingredients, is often a critical parameter. To achieve the desired particle size distribution, milling of such materials is usually the method of choice. Since these chemicals are often scarcely available, experimental optimization of milling is not possible. Therefore, a model to predict the milling conditions has been developed. The model estimates the rate of breakage function, and needs mechanical properties like hardness and yield strength as input to calculate the rate of breakage function. This paper attempts to check the validity of the model by a series of experiments. A comparison of the experimental results with the outcomes of the model using five different model compounds has been performed. It appears that the rate of breakage function can be estimated by: The model is able to rank the compounds by degree of fracture as an effect of milling. It was also possible to perform a quantitative prediction of the impact of milling pressure on the milling behavior. Finally, it appeared that the prediction of the large particles in the distribution was significantly better than small ones. Because the oversized material is usually the most critical parameter, the conclusion is that the model has acceptable practical applicability.     

A microfluidic magnetic bead impact generator for physical stimulation of osteoblast cell

We developed a novel microfluidic cell culture device in which magnetic beads repetitively collide with osteoblast cells, MC3T3‐E1, owing to attractive forces generated by pulsed electromagnetic fields and consequently the cells were physically stimulated by bead impacts. Our device consists of an on‐chip microelectromagnet and a microfluidic channel which were fabricated by a microelectromechanical system technique. The impact forces and stresses acting on a cell were numerically analyzed and experimentally generated with different sizes of bead (4.5, 7.6 and 8.4 μm) and at various pulse frequencies (60 Hz, 1 kHz and 1 MHz). Cells were synchronized at each specific phase of the cell cycle before stimulation in order to determine the most susceptible phase against bead impacts. The cells were stimulated with different sizes of bead at various pulse frequencies for 1 min at G1, S and G2 phases, respectively, and then counted immediately after one doubling time. The growth rate of cells was highly accelerated when they were stimulated with 4.5 μm beads at G1 phase and a pulse frequency of 1 MHz. Almost all of the cells were viable after stimulation, indicating that our cell stimulator did not cause any cellular damage and is suitable for use in new physical stimulus modalities.     

Hydrogen electrosorption in nanocrystalline Ti-based alloys

The electrochemical behavior in alkaline solution (1 M NaOH) of nanocrystalline Ti:Ru:Fe:O (2:1:1:2) prepared by high-energy ball milling was studied over its whole electroactivity domain, with a particular emphasis on the hydrogen evolution reaction (her). Comparison has also been made with nanocrystalline Ti:Ru:Fe (2:1:1) and a mixture of Ti:TiO:Ru:Fe₂O₃ (3/2:1/2:1:1/2). It was shown by cyclic voltammetry, open circuit potential decay and chronopotentiometry measurements that hydrogen absorption in the electrode material occurs during hydrogen discharge. The electrochemical behavior of nanocrystalline Ti:Ru:Fe:O (2:1:1:2) closely follows that of Ti:Ru:Fe (2:1:1), but differs radically from that of Ti:TiO:Ru:Fe₂O₃ (3/2:1/2:1:1/2). This is due to the fact that the former two compounds contain a significant fraction of B2 phase (59 and 97 wt.%, respectively), while the latter does not. In steady state conditions, the ratio H/B2 phase in nanocrystalline Ti:Ru:Fe:O (2:1:1:2) is 0.15, about 1.6 times less than that for the O-free nanocrystalline compound. The coefficient of diffusion of hydrogen in nanocrystalline Ti:Ru:Fe:O (2:1:1:2) is 2.6×10⁻¹³ cm² s⁻¹, more than three times less than that in nanocrystalline Ti:Ru:Fe (2:1:1). The difference between the hydrogen absorption characteristics of both nanocrystalline compounds are tracked down to the fact that their B2 phases have different stoichiometries.     

Synthesis of boron suboxide (B6O) with ball milled boron oxide (B2O3) under lower pressure and temperature

Boron reacted with ball milled boron oxide under pressures between 1 and 5 GPa and at temperatures between 1300 and 1700 °C to afford boron suboxide (B₆O). Icosahedral B₆O grains with diameters ranging from 100 nm to 1.3 μm were prepared. The factors that affect the synthesis of B₆O are investigated. The best sample with crystal size up to 1.3 μm is obtained at 2 GPa and 1400 °C for 6 h. The indentation experiment gave an average Vickers hardness of 32.3 GPa for bulk B₆O sample, which is consistent with previous reports. Bulk B₆O sample exhibits oxidation resistance in air up to 1000 °C and mild oxidation in the temperatures of 1000-1200 °C, which is more oxidation resistant than diamond. It is possible that B₆O could be used as a substitute for diamond in industry because of its relatively mild synthesis conditions, high thermal stability and high hardness.     

On-line renewable solid-phase extraction hyphenated to liquid chromatography for the determination of UV filters using bead injection and multisyringe-lab-on-valve approach

For the first time, an automatic sample pre-treatment/detection method is proposed for the multiclass determination of UV filters (namely, benzophenone-3, ethylhexylmetoxycinnamate, butylmethoxydibenzoylmethane and homosalate) in environmental samples. The new methodology comprises in-line solid-phase extraction (SPE) of the target analytes by exploiting the bead injection (BI) concept in a mesofluidic lab-on-valve (LOV) format, with subsequent determination by liquid chromatography (LC). The proposed microanalytical system, using a multisyringe burette as propulsion unit, automatically performed the overall SPE steps, including the renewal of the sorbent in each analytical cycle to prevent sample cross-contamination and the post-extraction adjustment of the eluate composition to prevent chromatographic band broadening effects. In order to expedite the LC separation, a C₁₈ monolithic column was applied and an accelerated isocratic elution was carried out by using a cationic surfactant as mobile phase additive. The LOV-BI-LC method was proven reliable for handling and analysis of complex matrices, e.g., spiked swimming pool water and seawater, with limits of detection ranging between 0.45 and 3.2 μg L⁻¹ for 9 mL sample volume. Linear calibration was attained up to 160 μg L⁻¹ for homosalate and up to 35 μg L⁻¹ for the other target analytes, with good reproducibility (RSD < 13%, for 5 different SPE columns). The hyphenated scheme is able to process a given sample simultaneously and within the same time frame than the chromatographic separation/determination of the formerly pre-treated sample, providing concentration values every 9 min. Hence, the sample throughput was enhanced up to 33 times when compared with previously reported off-line SPE methods. A drastic reduction in reagent consumption and effluent production was also attained, contributing to the development of an environment-friendly analyzer.     

High heat generation ability in AC magnetic field for nano-sized magnetic Y3Fe5O12 powder prepared by bead milling

Nano-sized magnetic Y₃Fe₅O₁₂ ferrite having a high heat generation ability in an AC magnetic field was prepared by bead milling. A commercial powder sample (non-milled sample) of ca. 2.9 μm in particle size did not show any temperature enhancement in the AC magnetic field. The heat generation ability in the AC magnetic field improved with a decrease in the average crystallite size for the bead-milled Y₃Fe₅O₁₂ ferrites. The highest heat ability in the AC magnetic field was for the fine Y₃Fe₅O₁₂ powder with a 15-nm crystallite size (the samples were milled for 4 h using 0.1 mm? beads). The heat generation ability of the excessively milled Y₃Fe₅O₁₂ samples decreased. The main reason for the high heat generation property of the milled samples was ascribed to an increase in the Néel relaxation of the superparamagnetic material. The heat generation ability was not influenced by the concentration of the ferrite powder. For the samples milled for 4 h using 0.1 mm? beads, the heat generation ability (W g⁻¹) was estimated using a 3.58×10⁻⁴ fH² frequency (f/kHz) and the magnetic field (H/kA m⁻¹), which is the highest reported value of superparamagnetic materials.     

Magnetic properties of iron nitride-alumina nanocomposite materials prepared by high-energy ball milling

The structural and magnetic properties of the granular iron nitride-alumina composite materials, (Fe_xN)_0.2(Al₂O₃)_0.8 and (Fe_xN)_0.6(Al₂O₃)_0.4, fabricated using high-energy ball milling have been determined by using X-ray diffraction, Mössbauer spectroscopy, and magnetization measurements. The Mössbauer spectra, fit with a distribution of hyperfine fields between zero and 40 T, indicate that the weighted average field decreases with increasing milling time. The isomer shift increases with milling time because of a reduced iron 4s-electron density at the grain boundaries. Coercive fields as high as 325 and 110 Oe are obtained for (Fe_xN)_0.2(Al₂O₃)_0.8 at 5 and 300 K, respectively; the increase in the coercive field upon cooling indicates the presence of superparamagnetic particles. The coercive field increases with milling time because of the reduced particle size. The decrease in the magnetization results from the increase in both the superparamagnetic fraction and the concentration of surface defects with increased milling time.     

Phase Transformations in Fe–Mn Alloys Induced by Ball Milling

Hyperfine Interactions - We have studied the dependence on the milling time of the amounts of metastable fcc and hcp phases produced by ball milling on Fe-13.7 wt% Mn alloys by Mössbauer...     

Direct In Situ Investigation of Milling Reactions Using Combined X‐ray Diffraction and Raman Spectroscopy

The combination of two analytical methods including time‐resolved in situ X‐ray diffraction (XRD) and Raman spectroscopy provides a new opportunity for a detailed analysis of the key mechanisms of milling reactions. To prove the general applicability of our setup, we investigated the mechanochemical synthesis of four archetypical model compounds, ranging from 3D frameworks through layered structures to organic molecular compounds. The reaction mechanism for each model compound could be elucidated. The results clearly show the unique advantage of the combination of XRD and Raman spectroscopy because of the different information content and dynamic range of both individual methods. The specific combination allows to study milling processes comprehensively on the level of the molecular and crystalline structures and thus obtaining reliable data for mechanistic studies.