Fluid dynamics in channel reactors stirred by submerged gas injection

This work describes the fluid flow and associated local and longitudinal mixing phenomena which influence the behavior and characteristics of continuous flow reactors, such as the Noranda reactor and the Q-S process. In the present work, mixing in channel reactors agitated by submerged gas injection along the length has been studied using a water model. The effects of gas injector separation, gas flow rate, depth of water, lateral configuration of injectors, submersion depth of gas injectors, and width of the channel have been investigated. It has been found that the longitudinal mixing depended significantly on the locations of the gas injectors. For constant values of other variables, there existed an optimum injector separation at which maximum longitudinal mixing was found. Industrial applications of this study are described.     

Fluid dynamics in channel reactors stirred by submerged gas injection

This work describes the fluid flow and associated local and longitudinal mixing phenomena which influence the behavior and characteristics of continuous flow reactors, such as the Noranda reactor and the Q-S process. In the present work, mixing in channel reactors agitated by submerged gas injection along the length has been studied using a water model. The effects of gas injector separation, gas flow rate, depth of water, lateral configuration of injectors, submersion depth of gas injectors, and width of the channel have been investigated. It has been found that the longitudinal mixing depended significantly on the locations of the gas injectors. For constant values of other variables, there existed an optimum injector separation at which maximum longitudinal mixing was found. Industrial applications of this study are described.     

Necrotizing pneumonia caused by Penicillium chrysogenum

We report a case of necrotizing pneumonia due to Penicillium chrysogenum in a 57-year-old woman operated on for lung cancer. The residual right lower pulmonary lobe was infiltrated by Penicillium chrysogenum. The patient underwent a second pulmonary right lobectomy and was successfully treated with oral itraconazole. To our knowledge, this is the first case of pneumonia due to P. chrysogenum.     

Production and purification of Penicillium citreoviride toxin and its effect on TPP-dependent liver transketolase

The production isolation and purification of a yellow mycotoxin from Penicillium citreoviride NRRL 2579 in different culture media was described. When injected subcutaneously to albino rats it alters the kinetic pattern of transketolase (EC 2.2.1.1) in liver in vivo in a competitive manner. In vitro, the inhibition is noncompetitive in nature. However, addition of thiamine diphosphate (TPP) to the in vitro system relieved the inhibitory effect. These findings suggested a relationship between citreoviridin-induced beriberi and the probable antithiamine effect of the toxin.     

Application of stirred mill to upgrading of graphite concentrate by flotation

It is difficult to obtain high-grade concentrates for layered minerals, such as graphite, by mineral processing due to the existence of impurities between interlayers. Conventional grinding mills are inefficient in liberating the mineral layers. Upgrading a graphite concentrate by re-grinding with a designed stirred mill is investigated in this paper. Better liberation of mineral layers was achieved, compared with a ball mill and a rod mill. Through re-grinding with the stirred mill followed by a two-stage cleaning flotation process, a low-grade graphite concentrate containing 84.59% fixed carbon could be refined to a high-quality concentrate containing 98.62% fixed carbon with a graphite recovery of 94.15%. It is demonstrated that the stirred mill is more suitable for selective grinding, mineral flake protection and upgrading of layered minerals.     

Sialic acid-dependent recognition of laminin by Penicillium marneffei conidia

Immunofluorescence microscopy demonstrated that laminin bound to the surface of Penicillium marneffei conidia. Attachment of P. marneffei conidia in an adherence assay was inhibited by soluble laminin and anti-laminin antibody. N-Acetylneuraminic acid abolished adherence, indicating an interaction mediated by a sialic acid-specific lectin.     

Calbistrins, novel antifungal agents produced by Penicillium restrictum. I. Production, taxonomy of the producing organism and biological activity

Over a 14-year period, from 1971 to 1985, there were 15 patients referred to the Princess Margaret Hospital in Toronto for postoperative radiotherapy to the cervical lymph nodes following radical neck surgery for metastatic cancer. An intensive investigation failed to yield a primary site in any patient. All of the patients had extensive neck disease with significant indications for postoperative radiotherapy (massive neck nodes, invasion of extra nodal structures or fixation to unresectable adjacent structures). Of this highly selected group of patients with advanced neck disease: 4/15 (27%) died within one year of uncontrolled local disease, a further 2/15 (13%) died within four years of metastatic/recurrent disease, 6/15 (33%) died of intercurrent disease and 3/15 (20%) were alive with at least four years follow-up. Although all patients presented with advanced disease, survival and significant palliation was possible in this select group of patients.     

Mixing-time correlation in top gas stirred melts

An experimental study is conducted to study the factors affecting the mixing-time of a top gas stirred metal bath in absence and presence of melting scrap by a chemical decolouration model method. The results obtained on mixing-time are presented and discussed. Mixing-time results are correlated successfully with the modified Froude number.     

Numerical modelling of gas stirred ladles

Abstract

A finite element analysis of the flow in a gas stirred vessel is presented. Turbulence is modelled using the two equation k–L predictor/ε corrector scheme algorithm; two alternative studies are compared, with and without flotation in k and ε transport equations. The biphasic zone is considered as an homogeneous fluid with a reduced density – the quasi-single phase approach. This reduced density is estimated taking into account the slip velocity between the rising bubbles and the liquid according to correlations from the literature. The numerical results are compared with experimental water model data and then used to predict the flow in two industrial liquid steel ladles with twin eccentric Ar injectors.     

Microbial depyritisation of three different coals by Acidithiobacillus ferrooxidans in a batch stirred tank reactor

Abstract

The present study aimed to investigate the depyritisation potential of Acidithiobacillus ferrooxidans on two different types of coals, namely lignite and anthracite collected from three different countries (Korea, China and Indonesia). The experimental work was conducted on a batch mode in a stirred tank reactor. All the batch biooxidation of pyrite in the different coal samples were conducted in a pH controlled condition (pH?=?1·5). The growth medium employed for the batch biooxidation of pyritic coal was free from iron supplement. At. ferrooxidans oxidised mineral pyrite of Korean anthracite at a greater rate (98%) compared to 96 and 92% of pyrite oxidation for Indonesian and Chinese lignite respectively. The ratio of bioleach residue to the feed was reasonably good with range of 8·56–9·06 stating the net mass loss of 9–14. Coal depyritisation was carried out by the available Fe³⁺ ion in the inoculum producing Fe²⁺ ion as a product and this Fe²⁺ ion was further oxidised to Fe³⁺ ion by At. ferrooxidans. This Fe³⁺ ion produced by At. ferrooxidans continued the oxidation of the residual pyrite in the coal until all pyrite content was oxidised completely. The three different coals were found to be feasible for biological depyritisation of the coal could be scaled up for further studies in a continuous stirred tank bioreactor.

L’étude présente avait pour but d’examiner le potentiel d’enlèvement de la pyrite par Acidithiobacillus ferrooxidans dans deux types de charbons, soit le lignite et l’anthracite, récoltés dans trois pays, soit la Corée, la Chine et l’Indonésie. On a effectué le travail expérimental dans un mode en vrac, dans un réacteur agité. On a effectué toute la bio-oxydation en vrac de la pyrite des échantillons de charbon à un pH contrôlé de 1·5. Le médium de croissance utilisé pour la bio-oxydation en vrac du charbon pyritique ne contenait pas de supplément de fer. At. ferrooxydans oxydait le minerai de pyrite de l’anthracite coréen en plus grande proportion (98%) que l’oxydation de la pyrite du lignite indonésien (96%) ou chinois (92%), respectivement. Le rapport de résidu de biolixiviation à l’alimentation était raisonnablement bon, avec une gamme de 8·56 à 9·06, établissant la perte de masse nette de 9 à 14. L’enlèvement de la pyrite du charbon était effectué par l’ion Fe³⁺ disponible dans l’inoculum, donnant lieu à l’ion Fe²⁺ comme produit et cet ion Fe²⁺ était davantage oxydé en ion Fe³⁺ par At. ferrooxidans. Cet ion Fe³⁺ produit par At. ferrooxidans continuait l’oxydation de la pyrite résiduelle dans le charbon jusqu’à ce que toute la pyrite soit complètement oxydée. On a trouvé qu’il était possible d’effectuer l’enlèvement biologique de la pyrite des trois charbons et d’augmenter l’échelle pour des études futures dans un bioréacteur en continu agité.     

Fluid flow behaviour of liquid in cylindrical vessels stirred by one or two air jets

In the present paper, based on the two‐phase model (Eulerian‐Eulerian model), the three‐dimensional fluid flow in water system and liquid steel system stirred by one or two gas jets is simulated. A new modified k‐? turbulence model is introduced to consider the bubbles movement contribution to k and ?. The mathematical simulation agrees well with the experimental results. Calculation indicates that the distance of the two jet nozzles has a big effect on the fluid flow behaviour. Placing two gas injection nozzles at the half radii of one diameter of the bottom generates a much better mixing than that injected by only one nozzle with the same total gas flow rate.     

Crystallization of a faceted primary phase in a stirred slurry

Stirring of an Al-19 pct Si alloy during primary solidification resulted in coarsening of the primary silicon particles relative to unstirred melts, although increasing rates of cooling or of stirring reduced the final particle size. The latter refinement is attributed to increasing rates of nucleation with higher cooling rate or shear rate. Crystal fragmentation may contribute to apparent nucleation rates. Coalescence of particles due to stirring was most pronounced at low fraction solid. Fragmentation was more probable at high fraction solid.     

The growth of off-eutectic composites from stirred melts

Theoretical arguments are presented which indicate that it should be possible to grow aligned off-eutectic composites from stirred melts. To obtain off-eutectic growth in an alloy of given composition, the convective mixing must be less than a critical amount. An open system is proposed which would be much better suited to the production of constant composition composites. The convective mixing offers the advantage of enabling higher temperature gradients to be maintained in order to stabilize the planar eutectic interface at the off-eutectic compositions.     

Grain refinement in magnetically stirred GTA welds of aluminum alloys

The mechanisms of grain refinement have been examined for magnetically stirred gas tungsten arc (GTA) welds completely penetrating thin sheets of several aluminum alloys. Grain refinement in unstirred welds may be brought about by adding sufficient titanium to produce heterogeneous nucleation by Ti-rich particles. In some alloys magnetic stirring is shown to extend the range of welding conditions which produce a partially equiaxed structure, and to widen the equiaxed fraction of partially equiaxed welds. This is attributed to magnetic stirring lowering the temperature gradient, allowing nucleation and growth of Al-rich grains further ahead of the columnar interface growing in from the fusion boundaries. In alloys with low Ti levels, magnetic stirring may cause refinement by sweeping grains from the partially molten zone ahead of the advancing solidification interface. This mechanism requires that the partially molten zone be sufficiently wide, and that the grain size in this zone remain small.     

A plug-in minielectrode for measurements in stirred photometric cuvettes

A device is described to perform potentiometric measurements with ion-sensitive electrodes in stirred photometric cuvettes. Its design allows to make additions to the reaction medium with microliter syringes during measurements. Originally, this plug-in electrode was designed to register the free Ca2+ concentrations in the incubation medium of mitochondrial suspensions during measurements of the free matrix Ca2+ concentration with a permeant fluorescent Ca2+ indicator. However, numerous other applications can be easily realized, such as the combination of mitochondrial light-scattering measurements and ion-transport measurements, the combination of the permeabilized cell technique with fluorescence measurements of intracellular organelles or simply the calibration of the fluorescence of Ca2+ indicators with a Ca2+ ion-sensitive minielectrode. Compared with the use of a second fluorescent indicator the use of an electrode has the advantage that the signal can be transformed into ion concentrations already during the measurements.     

带搅拌管式反应器中的流动特性

以NaCl溶液为示踪剂,采用脉冲示踪法考察了搅拌转速、流量及液位对带机械搅拌装置的管式反应器内停留时间分布（RTD）曲线的影响．用Peclet操作准数表征轴向扩散特性．结果表明：增加搅拌装置后,反应器内的流动型态仍接近活塞流;随流量的减小和液位的升高,流体流动愈向活塞流靠近,即减小流量或者升高水位有利于减小返混;当搅拌转速超过100r／min时,搅拌转速对停留时间分布的影响不大．     

Xanthofulvin, a novel semaphorin inhibitor produced by a strain of Penicillium

A new semaphorin inhibitor xanthofulvin was isolated from the cultured broth of a fungus Penicillium sp. SPF-3059 along with a known compound vinaxanthone by solvent extraction and bioassay-guided fractionation. The tautomeric structure of xanthofulvin was determined by spectroscopic analyses. The two compounds exhibited significant semaphorin inhibitory activity with IC50 values of 0.09 and 0.1 microg/ml, respectively, in semaphorin3A-induced growth cone collapse assay using cultured chick dorsal root ganglia neurons.