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1.
Dimensionless selection functions for the grinding of material in continuous gratedischarge mills can be scaled in terms of normalized quantities of feed rate, geometric mean size of the particles and the mill length-to-diameter ratio. Simulations using the scale-up criteria together with the lumped-parameter grinding model yield results for mills of different lengths and operating at different feed rates that are in excellent agreement with the observed values. 相似文献
2.
Regrinding is an essential step in many mineral processing flowsheets as a final preparatory step for mineral separation. It is normally carried out in open-circuit ball mills or rod mills. Wide fluctuations occurring in the hardness and size distribution of feed materials to regrinding mills result in a nonuniform product fineness and processing inefficiency. Using a previously developed regrinding model, this paper presents the dynamic analysis and design considerations of a control system for open-circuit grinding, using the traditional P-, PI-, and PID-control algorithms. This study shows the utility of simple analysis techniques in designing a mineral process control system with special attention given to the effect of sampling and analysis time on control system performance. 相似文献
3.
The effect of mechanical activation on the reduction behavior of a hematite concentrate has been examined using a combination of simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscope (SEM) analysis, and laser diffraction. The samples were activated in vibratory and planetary mills. 相似文献
4.
铀水冶尾矿库地下水流特征与模拟分析：以某矿为例 总被引：4，自引：1，他引：3
张金辉 《水文地质工程地质》1998,25(2):38-41
铀水冶尾矿库中地下水流动特征控制了核素向周围环境扩散与迁移。本文以某矿山谷型尾矿库为例,运用二维有限元模拟了库内地下水分布及流动,结合水文地质条件进行了分析与讨论。 相似文献
5.
The difficulties associated with slurry transportation in autogenous (ag) and semi-autogenous (sag) grinding mills have become more apparent in recent years with the increasing trend to build larger diameter mills for grinding high tonnages. This is particularly noticeable when ag/sag mills are run in closed circuit with classifiers such as fine screens/cyclones. 相似文献
6.
Neil R. Seifried 《Geoforum》1992,23(4)
Within the recent upswing of the pulp and paper investment cycle, the province of Alberta dramatically expanded its industry by attracting several billion dollars of new and expanded plants. An important precondition for these events was the global shift to hardwoods which made the mixed forests on the plains of Alberta useful and desirable for forest products firms. Beyond this, the government of Alberta aggressively fostered expansion through an array of measures to attract investment. Alberta was made competitive, in cost terms, by cost concessions within its industrial and forestry policies. In part, this was necessary because of relatively high standards in its environmental regulations. With the surge of investment, unforseen problems arose when several mills were located on individual rivers, and there were concerns over downstream water quality for which there were no clearcut answers. The lightning rod of public concern was the giant Alpac mill, one of the last to be proposed, which gained official approval after an extended approval process led to a change in process technology. However, official approval for the various mills has not allayed public misgivings and legal challenges over environmental impacts of various steps in the process from tree extraction to pulp and paper production. 相似文献
7.
A mathematical model for distribution function is developed considering the distribution of the number of fractures that can occur in a particle. It is shown as a consequence of the model that selection and distribution functions are intimately related through a single parameter — expected number of fractures per unit original size. This parameter can be comparatively easily obtained from batch experiments and can later be used to simulate industrial-scale grinding mills. Predictions of the model are amply confirmed by preliminary experimental results and other published observations. A correlation is developed to predict the parameter of the model from known equipment and operating variables for the particles used in the present study. 相似文献
8.
This paper presents the experimental results of the mechanical production of silica and carbonate colloidal particles below 100 nm using two types of stirred bead mills (i.e., DCP Superflow 12 and PML H/V). It is shown that the stirred bead mill with very small beads can be used as an efficient equipment for the production of the colloidal particles in nanoscale from the feed materials of several microns in sizes at high energy consumptions. The DCP Superflow mill with high power densities is superior for the effective size reduction and production rate, compared to the conventional PML H/V mill with lower power densities. The smaller particles could be produced by the DCP Superflow mill at the same level of high energy inputs as from the PML H/V mill. The “grinding limit” for the processes in the mills has been discussed. 相似文献
9.
The general assumption that the breakage distribution function is independent of time is critically reviewed. Though this assumption is shown to be generally valid for tumbling mills, introduction of the concept of time-dependent distribution functions is shown to reduce the number of steps required for the calculation of product distribution drastically. It is shown that the optimum time equivalent of a stage of calculation for tumbling mills is the maximum time up to which the parameter C of the model is proportional to time. Then the parameter C evaluated at this time should be used to obtain the distribution function. For attrition it is shown that the time equivalent of a stage equals the whole time of operation and hence the parameter C should be evaluated at the time corresponding to the residence time of particles in the system. A few empirical forms of distribution functions are also given which may be useful where the theoretical expression is not valid. 相似文献
10.
James D. Felley 《Estuaries and Coasts》1987,10(4):321-329
From September 1985 to August 1986, nekton species were sampled monthly by seine in three waterways that feed the upper Calcasieu Estuary of southwestern Louisiana. Of the three bayous sampled, Choupique Bayou has been elast modified by man. Contraband Bayou and Bayou d’Inde have been highly modified-both have been dredged and channelized along portions of their lengths, and both receive wastes from municipal sewagetreatment plants. Additionally, Bayou d’Inde receives industrial waste from a large petrochemical complex. To identify different nekton assemblages of the three bayous, detrended correspondence analysis (DCA) was performed on a species-by-sample matrix containing numbers of individuals of all species sampled at all locations. This analysis differentiated between freshwater assemblages found in a bayou’s upper reaches and estuarine assemblages found in downstream reaches, and demonstrated seasonal changes in species composition of these assemblages. The freshwater and estuarine assemblages contained some species in common. In particular, several estuarine, species appeared in high numbers throughout the bayous, moving into freshwater as postlarvae and small juveniles. These freshwater reaches comprise an important nursery area for many estuarine species (including commercially important forms). However, the value of estuarine and freshwater nursery areas is compromised by human activities. Choupique Bayour was quite rich in species, with an average of 23.7 species sampled each month. The species found in Contraband Bayou were a subset of those found in Choupique Bayou. Contraband Bayou averaged 14.8 species each month, lacking many oxygen-sensitive species found in Choupique Bayou. Species found in Bayou d’Inde were a restricted subset of those found in Contraband Bayou (average of 10.1 species sampled each month). Most of the species inhabiting Bayou d’Inde were relatively less abundant than in Contraband Bayou. These results showed that human activities dramatically reduced the number of species found in a bayou and reduced the value of a bayou as a nursery area for commercially important species. 相似文献
11.
An Evaluation of the Effects of Primary and Cross‐Contamination during the Preparation of Rock Powders for Chemical Determinations 
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下载免费PDF全文 José P. Sertek Sandra Andrade Horstpeter H. Ulbrich 《Geostandards and Geoanalytical Research》2015,39(3):381-397
Quartz crystals from the Batatal site, Minas Gerais, southern Brazil, were used to determine quantitatively primary contamination when submitting the samples to milling processes. Crushing devices used were a primary steel jaw crusher (br1), a secondary tungsten carbide (WC) crusher (br2) and a hydraulic press with stainless steel plates (pr). Fragments with suitable sizes were then ground in different Fritsch planetary mills, equipped with agate, WC and chromium‐steel rings for 7, 4 and 3 min, respectively. Solutions of the powders were analysed initially with the TotalQuant? method in a quadrupole ICP‐MS instrument, providing semi‐quantitative results for seventy‐five elements. Contamination from crushers and mills was visible in major and minor elements such as Fe, Mn and Ti, and noticeable in trace elements such as Cr, Co, Ni, Cu and also V, Zr, Sc; significant contamination was observed from W, Mo, Co, Ta and Nb (mainly by use of the WC devices). Little or no contamination was observed for Pb, REE, Sr and Rb, elements that are important in routine isotopic determinations. Cross‐contamination was tested by grinding either a granite or a basalt sample, followed by conventional cleaning with mica‐free quartz sand, before the working quartz powder was prepared. 相似文献
12.
13.
Neil W. Perk Laurence A. Coogan Jeffrey A. Karson Emily M. Klein Heather D. Hanna 《Contributions to Mineralogy and Petrology》2007,154(5):575-590
A suite of samples collected from the uppermost part of the plutonic section of the oceanic crust formed at the southern East
Pacific Rise and exposed at the Pito Deep has been examined. These rocks were sampled in situ by ROV and lie beneath a complete
upper crustal section providing geological context. This is only the second area (after the Hess Deep) in which a substantial
depth into the plutonic complex formed at the East Pacific Rise has been sampled in situ and reveals significant spatial heterogeneity
in the plutonic complex. In contrast to the uppermost plutonic rocks at Hess Deep, the rocks studied here are generally primitive
with olivine forsterite contents mainly between 85 and 88 and including many troctolites. The melt that the majority of the
samples crystallized from was aggregated normal mid-ocean ridge basalt (MORB). Despite this high Mg# clinopyroxene is common
despite model predictions that clinopyroxene should not reach the liquidus early during low-pressure crystallization of MORB.
Stochastic modeling of melt crystallisation at various levels in the crust suggests that it is unlikely that a significant
melt mass crystallized in the deeper crust (for example in sills) because this would lead to more evolved shallow level plutonic
rocks. Similar to the upper plutonic section at Hess Deep, and in the Oman ophiolite, many samples show a steeply dipping,
axis-parallel, magmatic fabric. This suggests that vertical magmatic flow is an important process in the upper part of the
seismic low velocity zone beneath fast-spreading ridges. We suggest that both temporal and spatial (along-axis) variability
in the magmatic and hydrothermal systems can explain the differences observed between the Hess Deep and Pito Deep plutonics.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
SIWAN M. DAVIES WIM Z. HOEK SJOERD J. P. BOHNCKE J. JOHN LOWE SEAN PYNE O''DONNELL CHRIS S. M. TURNEY 《Boreas: An International Journal of Quaternary Research》2005,34(2):123-135
Three distal tephra layers or cryptotephras have been detected within a sedimentary sequence from the Netherlands that spans the last glacial-interglacial transition. Geochemical analyses identify one as the Vedde Ash, which represents the southernmost discovery of this mid-Younger Dryas tephra so far. This tephra was found as a distinct horizon in three different cores sampled within the basin. The remaining two tephras have not been geochemically 'fingerprinted', partly due to low concentrations and uneven distributions of shards within the sequences sampled. Nevertheless, there is the potential for tracing these tephra layers throughout the Netherlands and into other parts of continental Europe. Accordingly, the possibilities for precise correlation of Dutch palaeoenvironmental records with other continental, marine and ice-core records from the North Atlantic region are highlighted. 相似文献
15.
The compression index is a one of the important soil parameters that is essential to geotechnical designs. As the determination of the compression index from consolidation tests is relatively time-consuming, empirical formulas based on soil parameters can be useful. Over the decades, a number of empirical formulas have been proposed to relate the compressibility to other soil parameters, such as the natural water content, liquid limit, plasticity index, specific gravity, and others. Each of the existing empirical formulas yields good results for a particular test set, but cannot accurately or reliably predict the compression index from various test sets. In this study, an alternative approach, an artificial neural network (ANN) model, is proposed to estimate the compression index with numerous consolidation test sets. The compression index was modeled as a function of seven variables including the natural water content, liquid limit, plastic index, specific gravity, and soil types. Nine hundred and forty-seven consolidation tests for soils sampled at 67 construction sites in the Republic of Korea were used for the training and testing of the ANN model. The predicted results showed that the neural network could provide a better performance than the empirical formulas. 相似文献
16.
Liner design and lifter geometry in tumbling mills are very important in comminution kinetics and energy consumption. In terms of the parameters of the batch grinding model, the breakage rate function decreases as lifter size increases while the breakage distribution function is independent of the lifter size. However, the specific energy consumption is not a function of lifter size. Reducing the lifter height from 2.54 cm to 0.32 cm increases the production from this mill by 37%. When the mill is operated without any lifters, the charge apparently slips inside the shell resulting in lower breakage kinetics and higher energy consumption. 相似文献
17.
CHARLES K. PAULL WILLIAM USSLER III W. STEVEN HOLBROOK TESSA M. HILL HAFLIDI HAFLIDASON WILLIAM WINTERS THOMAS LORENSON IVANO AIELLO JOEL E. JOHNSON EVE LUNDSTEN 《Sedimentology》2010,57(6):1409-1429
Deposits within the floor of the Norwegian Basin were sampled to characterize the deposition from the Storegga Slide, the largest known Holocene‐aged continental margin slope failure complex. A 29 to 67 cm thick veneer of variable‐coloured, finely layered Holocene sediment caps a homogeneous, extremely well‐sorted, poorly consolidated, very fine‐grained, grey‐coloured sediment section that is >20 m thick on the basin floor. This homogeneous unit is interpreted to represent the uppermost deposits generated by a gravity flow associated with the last major Storegga Slide event. Sediments analogous to the inferred source material of the slide deposits were collected from upslope on the Norwegian Margin. Sediments sampled within the basin are distinguishable from the purported source sediments, suggesting that size sorting has significantly altered this material along its flow path. Moreover, the very fine grain size (3·1 ± 0·3 μm) suggests that the >20 m thick homogeneous unit which was sampled settled from suspension after the turbulent flow was over. Although the turbulent phase of the gravity flow that moved material out into the basin may have been brief (days), significantly more time (years) is required for turbid sediments to settle and dewater and for the new sea floor to be colonized with a normal benthonic fauna. Pore water sulphate concentrations within the uppermost 20 m of the event deposit are higher than those normally found in sea water. Apparently the impact of microbial sulphate reduction over the last ca 8·1 cal ka bp since the re‐deposition of these sediments has not been adequate to regenerate a typical sulphate gradient of decreasing concentration with sub‐bottom depth. This observation suggests low rates of microbial reactions, which may be attributed to the refractory carbon composition in these re‐deposited sediments. 相似文献
18.
工作面建模一般通过三维地震、井巷和钻孔测量等探测手段获取工作面的实际展布情况,然后利用插值算法建立相应模型。其中,采样数据是工作面建模的基础,插值算法是工作面模型实现的必经途径。插值算法和采样数据量的大小在不同程度上影响工作面模型的精确性,定量研究工作面模型精确度影响因素将对插值算法优选和采样数据获取量提供重要的参考价值。在工作面探测资料的基础上,通过交叉验证的方法,分别计算对比函数插值、光滑离散插值(DSI插值)和克里金插值的插值误差。为了解决透明工作面建模采样量大的问题,提出相对间距误差,并计算得到13组不同采样比例时模型的相对间距误差。结果表明:(1)透明工作面模型构建过程中,DSI插值、克里金插值和函数插值的平均绝对误差分别为0.015 5、0.022 5、0.231 2,因此,DSI插值算法构建的模型精确度最高,克里金插值算法次之,函数插值算法最差。(2)随着采样数据量的增加,模型的误差逐渐减小,当采样数据量小于10%时,插值误差下降幅度很大;但当采样数据量大于10%时,其下降幅度趋于平缓,建议在构建工作面模型时采样数据量大于10%。(3)在透明工作面模型实际构建过程中,建议采用DSI插值算法;同时根据最低采样数据量分析得到的最佳更新距离和最佳采样间距进行采样,提高工作面局部数据量。 相似文献
19.
A. Vorobiev 《冰川冻土》2004,26(Z1):175-178
The tailing dump of concentrating mills is specific ground massifs in permafrost areas, which -impacts on geological environment heavily. The deposits are important, namely, the sources of the rare metals in the Norilsk industrial area. The engineering process of the permafrost tailing dump mining is discussed in this paper based on the study of the artificial cryogenesis. 相似文献
20.
Roger Hayter 《Geoforum》1979,10(2):163-177
This paper examines determinants of labour sheds for new industrial ventures located in isolated communities and analyses comparatively several geographic and socioeconomic characteristics of workers hired by pulp and paper mills recently established in north-central British Columbia. 相似文献