机械喂料条件下利用石粒作钙源的可行性

为探索机械动力送料过程中石粒为钙源蛋鸡饲粮的营养成分变化及对蛋壳品质的影响,在L鸡场的两栋鸡舍进行试验。在每栋鸡舍选择四条料线和在每一料线不同位点采饲粮样,测定其钙、总磷,同时取蛋样测定了相应位置的蛋壳品质.结果表明,各料线和位点的饲粮钙含量差异均不显著(P>0.05),位点间总磷含量差异不显著(P>0.05),但距料塔最远的料线上饲粮总磷含量均显著(P<0.05和P<0.01)高于其他各料线,在不同料线和位点上所取蛋样的蛋壳强度和蛋壳率差异不显著(P>0.05).

老龄母鸡饲养中添加砂砾或用石粒作钙源的效果

用106只75周龄京白品种淘汰母鸡研究了添加砂砾(Ⅰ组)和以全石粒(Ⅱ组)、全石粉(对照组)作钙源的效果。结果表明,三组产蛋性能(软蛋率除外)和料蛋此无显著差异(P>0.05),Ⅱ组蛋壳显著比Ⅰ(P<0.05)和对照组(P<0.01)薄,其他蛋壳品质指标组间无显著差异(P>0.05);Ⅱ组从蛋内容物与蛋壳中回收的钙显著高于另两组;停喂砂砾和石粒190—191小时后,仍有砂砾或石粒滞留于肌胃内。

粉体和天然石粒的表面积测量

简化氮吸附装置是一种改进的真空容量法装置,已发展到用于测量0.2M_2/g～1000M^2/g范围的固体比表面用。此法测定活性炭、催化剂、粉体和天然石粒的不同压力下氮吸附量,在相对平衡压力0.05～0.3范围内,均可用二参数BET方程计算。实验证明,装置适合在设计的测量范围内使用。

颗石藻颗石粒形态的原子力显微观测方法:以赫氏艾密里藻为例

颗石藻(coccolithophore)作为一种模式生物,在重建古海洋气候和环境以及预测未来全球气候变化中起着很重要的作用,赫氏艾密里藻(Emiliania huxleyi)是颗石藻最为典型的代表种。钙质颗石粒(coccolith)是颗石藻形态分类的主要依据,有着非常精细和复杂的结构,在样品收集过程中很容易遭到破坏,这是颗石藻鉴定中经常遇到的一个技术问题。国际上还没有统一的颗石藻定量采样和样品分析方法。本文采用原子力显微方法(atomic force microscopy,AFM)对赫氏艾密里藻的颗石粒形态进行了超显微观察研究,获取不同扫描范围的高度图(height image)和形貌图(deflection image)以观测其形态结构,并建立了针对颗石藻的原子力显微样品制备方法。通过离心与膜过滤两种方法收集赫氏艾密里藻,比较后得出了一种简单、快速的适合于观测颗石藻在大气环境成像的样品处理、制备和图像采集方法:3,000–4,000 rpm,20℃离心5 min,收集颗石藻,去除有机杂质后取白色沉淀,将沉淀物悬浮于0.05 M NH_4HCO_3溶液中,悬浮液滴加于盖玻片表面,20℃晾干后于样品台在AFM接触模式(contact mode)下原子级扫描,扫描范围50μm,频率1 Hz,可以得到优质的颗石粒形态图像,有助于颗石藻的分类鉴别。该方法可用于室内不同环境梯度或参数下的颗石粒形态结构及颗石藻藻华的检测与研究。

一种具有开发潜力的微藻——圆石藻

文章介绍了一种具有开发潜力的海洋浮游微藻———圆石藻的开发前景。圆石藻属于定鞭藻门 ,为光能自养单细胞藻类。圆石藻细胞内富含高级不饱和脂肪酸 (ω—3PUFA)、钙、蛋白质及其他多种生物活性物质 ,同时 ,圆石藻还可以吸收外源维生素B12 ,并转化成具有生物活性的VB12 类似物富集在细胞内。因此 ,圆石藻在食品添加剂、保健食品方面具有很大的开发潜力。同时 ,由于圆石藻特殊的生物钙化作用 ,在环境保护方面同样具有应用前景。

Effect of ore size and heap porosity on capillary process inside leaching heap

The capillary process coexists with gravity flow within leaching heap due to the dual-porosity structure. Capillary rise is responsible for the mineral dissolution in fine particle zones and interior coarse rock. The effect of particle size and heap porosity on the capillary process was investigated through a series of column tests. Macropore of the ore heap was identified, and its capillary rise theory analysis was put forward. Two groups of ore particles, mono-size and non-uniform, were selected for the capillary rise test. The result shows that particle size has an inverse effect on the capillary ultimate height, and smaller particles exhibit higher capillary rise. Meanwhile, the poorly graded group exhibits small rise height and velocity, while the capillary rise in the well-graded particles is much greater. The relationship between porosity and fitting parameters of capillary rise was obtained. Low porosity and high surface tension lead to higher capillary height of the fine gradation. Moisture content increases with the capillary rise level going up, the relationship between capillary height and moisture content was obtained.

Collision and attachment behavior between fine cassiterite particles and H_2 bubbles

Particle-bubble interaction during electro-flotation of cassiterite was investigated by determining the recovery of cassiterite and the collision mechanism of cassiterite particle and H2 bubble. Flotation tests at different conditions were conducted in a single bubble flotation cell. The recovery of cassiterite was found to be affected by cassiterite particle and bubble size. A matching range, in which the best recovery can be obtained, was found between particle and bubble size. Collision, attachment, and detachment of the particle-bubble were observed and captured by a high-speed camera. Particle-bubble collision and attachment were analyzed with the use of particle-bubble interaction theory to obtain the experimental results. An attachment model was introduced and verified through the photos captured by the high-speed camera. A bridge role was observed between the bubbles and particles. Particle-bubble interaction was found to be affected by bubble size and particle size, which significantly influenced not only the collision and attachment behavior of the particles and bubbles but also the flotation recovery of fine cassiterite particles.

3D characterization and analysis of pore structure of packed ore particle beds based on computed tomography images

Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional images of specimens with single particle size of 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 ram. Based on the in-house developed 3D image analysis programs using Matlab, the volume porosity, pore size distribution and degree of connectivity were calculated and analyzed in detail. The results indicate that the volume porosity, the mean diameter of pores and the effective pore size （d50） increase with the increasing of particle size. Lognormal distribution or Gauss distribution is mostly suitable to model the pore size distribution. The degree of connectivity investigated on the basis of cluster-labeling algorithm also increases with increasing the particle size approximately.

Electro-flotation and collision-attachment mechanism of fine cassiterite

In order to discuss the particle-bubble interaction during the electro-flotation of cassiterite,the recovery of cassiterite with different particle sizes was investigated,and the collision mechanism between the cassiterite particles and H2 bubbles was explored.The flotation tests were carried out in a single bubble flotation cell.The results show that cassiterite particles 10 μm,10-20 μm,20？38 μm and 38-74 μm match with bubbles with size of 50-150 μm,about 250 μm,74 μm and 74 μm,respectively,and a better recovery can be obtained.It is demonstrated that the recovery of cassiterite is influenced by the size of cassiterite particles and bubbles.Furthermore,the probabilities of collision,adhesion,detachment and collection were calculated using the collision,attachment and collection models.Theoretical calculation results show that the collision probability decreases sharply with decreasing particle size and increasing bubble size（below 150 μm）.The attachment probability would increase from the effective collision,leading to the increase of recovery.

Mineralogical characterization of tin-polymetallic ore occurred in Mengzi,Yunnan Province,China

A detailed mineralogical characterization of a tin-polymetallic ore from Mengzi,Yunnan Province,China,was undertaken by automated electron microprobe-based mineral mapping and quantitative analysis methods.The results show that the most valuable metal is Sn（0.98%,mass fraction）.The main tin minerals are cassiterite and stannite,which account for 94.90% of total tin.Other metals,such as Cu（0.261%）,Zn（0.612%） and Pb（0.296%） can also be seen as valuable metal to be recovered.Minerals such as pyrrhotite,pyrite,arsenopyrite,sphalerite,galena and chalcopyrite are disseminated in the ore.Quartz,sericite and dolomite are the main gangue.The optimal grinding fineness should be chosen as 0.037 mm to make sure that most of the tin minerals can be liberated from other minerals.

Support vector machines approach to mean particle size of rock fragmentation due to bench blasting prediction

Aiming at the problems of the traditional method of assessing distribution of particle size in bench blasting, a support vector machines （SVMs） regression methodology was used to predict the mean particle size （X50） resulting from rock blast fragmentation in various mines based on the statistical learning theory. The data base consisted of blast design parameters, explosive parameters, modulus of elasticity and in-situ block size. The seven input independent variables used for the SVMs model for the prediction of X50 of rock blast fragmentation were the ratio of bench height to drilled burden （H/B）, ratio of spacing to burden （S/B）, ratio of burden to hole diameter （B/D）, ratio of stemming to burden （T/B）, powder factor （Pf）, modulus of elasticity （E） and in-situ block size （XB）. After using the 90 sets of the measured data in various mines and rock formations in the world for training and testing, the model was applied to 12 another blast data for validation of the trained support vector regression （SVR） model. The prediction results of SVR were compared with those of artificial neural network （ANN）, multivariate regression analysis （MVRA） models, conventional Kuznetsov method and the measured X50 values. The proposed method shows promising results and the prediction accuracy of SVMs model is acceptable.

Model of limestone calcination / sulfation under oxy-fuel fluidized bed combustion

The characteristics of the simultaneous calcination/ sulfation of limestone under oxy-fuel fluidized bed combustion were studied and compared with those of the sulfation of precalcined CaO. During the calcination stage, SO2 can react with product CaO and slow down the CaCO3 decomposition rate by the covering effect of the CaSO4 product. The sulfation rate of simultaneous calcinatiort/sulfation is slower than that of precalcined CaO, but with a long enough sulfation time, the calcium conversion of simultaneous calcination/sulfation is higher than that of the precalcined CaO. A grain-micrograin model is established to describe the simultaneous calcination, sintering and sulfation of limestone. The graln-micrograln model can reflect the true reaction process of the calcination and sulfation of limestone in oxy-fuel fluidized bed combustion.

Multi-scale impact crushing characteristics of polymetallic sulphide ores

The effects of crushing energy, ore hardness and particle size of cassiterite polymetallic sulphide ore and lead-zinc polymetallic sulphide ore on the crushing characteristics during impact crushing were investigated by mineral liberation analyzer(MLA) and drop weight test. The results show that both ores contain pyrrhotite, sphalerite, jamesonite, gangue mica and quartz except cassiterite. Cassiterite is closely associated with sulphide and quartz to form aggregates, which are mixed with each other in the form of intergrowth or symbiotic disseminated fine grains. Cassiterite has a significant impact on ore crushing characteristics. Ore hardness is negatively correlated with the product of crushing parameters of A and b, i.e. A×b, the effect of crushing energy on crushing fineness is related to crushing parameters A and b, and the influence degree increases with the increase of A. The influence degree increases with the increase of b when crushing energy ECS is less than 1 kW·h/t, and the influence degree decreases with the increase of b when crushing energy ECS is greater than 1 kW·h/t. The impact of crushing energy on crushing fineness is greater than that of ore particle size when the crushing energy is lower;on the contrary, the impact of ore particle size on crushing fineness is greater than that of crushing energy when crushing energy is higher.

Dissolution kinetics of low grade complex copper ore in ammonia-ammonium chloride solution

The leaching kinetics of Tang-dan refractory low grade complex copper ore was investigated in ammonia-ammonium chloride solution.The concentration of ammonia and ammonium chloride,the ore particle size,the solid-to-liquid ratio and the temperature were chosen as parameters in the experiments.The results show that temperature,concentration of ammonia and ammonium chloride have favorable influence on the leaching rate of copper oxide ores.But,leaching rate decreases with increasing particle size and solid-to-liquid ratio.The leaching process is controlled by the diffusion of the lixiviant and the activation energy is determined to be 23.279 kJ/mol.An equation was also proposed to describe the leaching kinetics.

High Performance Ultraviolet Photodetector Fabricated with ZnO Nanoparticles-graphene Hybrid Structures

Ultraviolet （UV） photodetector constructed by ZnO material has attracted intense research and commercial interest. However, its photoresistivity and photoresonse are still unsatisfied. Herein, we report a novel method to assemble ZnO nanoparticles （NPs） onto the reduced graphite oxide （RGO） sheet by simple hydrothermal process without any surfactant. It is found that the high-quality crystallized ZnO NPs with the average diameter of 5 nm are well dispersed on the RGO surface, and the density of ZnO NPs can be readily controlled by the concentration of the precursor. The photodetector fabricated with this ZnO NPs- RGO hybrid structure demonstrates an excellent photoresponse for the UV irradiation. The results make this hybrid especially suitable as a novel material for the design and fabrication of high performance UV photodector.

Damage mechanism of soil-rock mixture after freeze-thaw cycles

As a widely distributed geological and engineering material,the soil-rock mixture always undergoes frequentative and short-term freeze-thaw cycles in some regions.Its internal structure is destroyed seriously,but the damage mechanism is not clear.Based on the damage factor,the damage research of properties of soil-rock mixture after different times of freeze-thaw cycles is investigated.Firstly,the size-distributed subgrade gravelly soil samples are prepared and undergo different times of freeze-thaw cycles periodically(0,3,6,10),and indoor large-scale triaxial tests are completed.Secondly,the degradation degree of elastic modulus is considered as a damage factor,and applied to macro damage analysis of soil-rock mixture.Finally,the mesoscopic simulation of the experiments is achieved by PFC3D,and the influence on strength between soil-rock particles caused by freeze-thaw cycles is analyzed.The results show that freeze-thaw cycles cause internal damage of samples by weakening the strength between mesoscopic soil-rock particles,and ultimately affect the macro properties.After freeze-thaw cycles,on the macro-scale,elastic modulus and shear strength of soil-rock mixture both decrease,and the decreasing degree is related to the times of cycles with the mathmatical quadratic form;on the meso-scale,freeze-thaw cycles mainly cause the degradation of the strength between soil-rock particles whose properties are different significantly.

Effect of mechanical activation on alkali leaching of chromite ore

Mechanical activation was used to improve the extraction of chromium in molten NaOH.It is observed that the extraction ratio reaches 97% after leaching for 200 min when chromite ore is mechanically activated for 10 min,but only 34% if not activated.Mechanical activation can decrease the particle size,increase the surface area,and enhance the lattice distortion.Further,the mechanisms for mechanical activation were exposed.The results show that the mechanical activation mainly focuses on chromite ore particle size decrease and the lattice distortion.The formation of aggregation weakens the strengthening effect of mechanical activation for releasing high surface energy.

Adsorption mechanism of mixed salicylhydroxamic acid and tributyl phosphate collectors in fine cassiterite electro-flotation system

Two reagents including salicylhydroxamic acid(SHA) and tributyl phosphate(TBP) were tested as collectors either separately or together for electro-flotation of fine cassiterite(<10 μm).Subsequently,the flotation mechanism of the fine cassiterite was investigated by adsorbance determination,electrophoretic mobility measurements and Fourier transform infra-red(FT-IR) spectrum checking.Results of the flotation experiments show that with SHA as a collector,the collecting performance is remarkably impacted by the pulp pH value as the floatability of cassiterite varies sharply when the pH changes,and flotation with SHA gives distinct maximum at about pH 6.5.Additionally,the floatability of cassiterite is determined by using SHA and TBP as collectors.The range of pulp pH for good floatability is broadened in the presence of TBP as auxiliary collector,and the utilization of TBP improves the recovery of cassiterite modestly.Moreover,the optimum pH value for cassiterite flotation is associated with adsorbance.The results of FT-IR spectrum and the electrophoretic mobility measurements indicate that the adsorption interaction between the collectors and the cassiterite is dominantly a kind of chemical bonding in the form of one or two cycle chelate rings due to the coordination of carbonyl group,hydroxamate and P=O group to the metal tin atoms,where the oxygen atoms contained in carbonyl group,hydroxamate and P=O group of the polar groups have the stereo conditions to form five-membered rings.In addition,the adsorption interactions of SHA and TBP on the surfaces of cassiterite are also dominated by means of hydrogen bonds.

Pore structure of ore granular media by computerized tomography image processing

The pore structure images of ore particles located at different heights of leaching column were scanned with X-ray computerized tomography (CT) scanner, the porosity and pore size distribution were calculated and the geometrical shape and connectivity of pores were analyzed based on image process method, and the three dimensional reconstruction of pore structure images was realized. The results show that the porosity of ore particles bed in leaching column is 42.92%, 41.72%, 39.34% at top, middle and bottom zone, respectively. Obviously it has spatial variability and decreases appreciably along the height of the column. The overall average porosity obtained by image processing is 41.33% while the porosity gotten from general measurement method in laboratory is 42.77% showing the results of both methods are consistent well. The pore structure of ore granular media is characterized as a dynamical space network composed of interconnected pore bodies and pore throats. The ratio of throats with equivalent diameter less than 1.91 mm to the total pores is 29.31%, and that of the large pores with equivalent diameter more than 5.73 mm is 2.90%.