Respirometry Studies of the Bioleaching of a Copper Ore in a Large Isothermal Column

2009 ◽  
Vol 71-73 ◽  
pp. 405-408
Author(s):  
Jochen Petersen ◽  
Sanet H. Minnaar ◽  
Chris A. du Plessis
Keyword(s):  
Linear Correlation ◽  
Large Scale ◽  
Energy Requirement ◽  
Population Decline ◽  
Growth Yield ◽  
Low Grade ◽  
Copper Ore ◽  
Oxidation Rates ◽  
Co2 Consumption ◽  
Air Stream

During large-scale column tests at BHP Billiton’s Johannesburg Technology Centre (JTC) during 2005/6 on a low-grade copper ore, the concentrations of both oxygen and CO2 were continuously monitored in feed and exit gas as well as at various intermediate positions over the height of the column. This paper describes results from a test run at 40 °C fed with an air stream enriched to between 1000 and 2000 ppm CO2. Oxygen consumption very closely tracks iron and copper leaching. CO2 is consumed rapidly from the bottom up, resulting in significant depletion midway through the column, even though an enriched feed was used. Oxidation rates decline in CO2 depleted zones, but were not observed to cease completely. This rate of decline is postulated to be linked to a slowly decaying population unable to regenerate itself. Comparison between O2 and CO2 consumption rates shows a linear correlation beyond a minimum oxidation rate. This minimum rate corresponds to a non-growth maintenance energy requirement, and the slope of the linear correlation to the growth yield. Both are functions of available CO2 in the range 50 to 1000 ppm, with maintenance declining and yield increasing. The findings of this study imply that CO2 supplementation in bioheaps will stimulate microbial growth and CO2 consumption, but not necessarily increase the rate of oxygen uptake and hence leaching. Absence of CO2 is expected to result in gradual population decline, but a degree of oxidation continues on the basis of maintenance. In tall heaps CO2 depletion with height is likely and may therefore result in impaired leaching in the upper zones.

Insights into Heap Bioleaching at the Agglomerate-Scale

2017 ◽  
Vol 262 ◽  
pp. 185-188 ◽  
Author(s):  
Alison Cox ◽  
Christopher G. Bryan
Keyword(s):  
Interstitial Cell ◽  
Cell Concentration ◽  
Low Grade ◽  
Dissolved Metals ◽  
Copper Ore ◽  
Cell Numbers ◽  
Liquid Phases ◽  
Heap Bioleaching ◽  
Cell Concentrations ◽  
The Difference

Previous agglomerate-scale heap bioleaching studies have outlined the variations in cell numbers of the liquid and attached phases during colonisation of sterilised ore by a pure culture. In this study, a mixed mesophilic culture was used in agglomerate-scale columns containing non-sterilised low-grade copper ore. Over a six - month period, columns were harvested at various intervals to provide snapshots of the metal distribution and the quantity, location, and ecological variations of mineral-oxidizing microbes within the ore bed. The initial colonisation period in this experiment was dissimilar to previous work, as the indigenous community was retained within the ore-bed throughout acid agglomeration. The overall colonisation phase lasted for approximately 1,000 hours until cell concentrations stabilised. In each column, less than 0.05% of the total cells were found in the leachate, 15-20% in the interstitial phase and the remaining ~80% were attached to the mineral surface. Once cell numbers had stabilised, interstitial cell concentrations were approximately 2,000× greater than those in the leachate. This difference persisted for the duration of the experiment. Copper concentrations in the two liquid phases generally decreased over time, but were on average 50× higher in the interstitial phase. Iron concentrations were more stable, but again were 30× higher in the interstitial phase. This demonstrates that that the difference in cell concentration between the leachate and interstitial phases cannot be explained through diffusion gradients within the system as it is much greater than those observed for the dissolved metals. It also shows that the specific environmental conditions of the interstitial and attached cells are very different to those inferred through analysis of leachates alone.

A numerical study of the transition of jet diffusion flames

1990 ◽  
Vol 431 (1882) ◽  
pp. 301-314 ◽  
Keyword(s):  
Reynolds Number ◽  
Diffusion Coefficient ◽  
Large Scale ◽  
Numerical Study ◽  
Small Scale ◽  
Surface Model ◽  
Flame Surface ◽  
Transition Mechanism ◽  
Air Stream ◽  
Scale Fluctuation

A numerical study on the transition from laminar to turbulent of two-dimensional fuel jet flames developed in a co-flowing air stream was made by adopting the flame surface model of infinite chemical reaction rate and unit Lewis number. The time dependent compressible Navier–Stokes equation was solved numerically with the equation for coupling function by using a finite difference method. The temperature-dependence of viscosity and diffusion coefficient were taken into account so as to study effects of increases of these coefficients on the transition. The numerical calculation was done for the case when methane is injected into a co-flowing air stream with variable injection Reynolds number up to 2500. When the Reynolds number was smaller than 1000 the flame, as well as the flow, remained laminar in the calculated domain. As the Reynolds number was increased above this value, a transition point appeared along the flame, downstream of which the flame and flow began to fluctuate. Two kinds of fluctuations were observed, a small scale fluctuation near the jet axis and a large scale fluctuation outside the flame surface, both of the same origin, due to the Kelvin–Helmholtz instability. The radial distributions of density and transport coefficients were found to play dominant roles in this instability, and hence in the transition mechanism. The decreased density in the flame accelerated the instability, while the increase in viscosity had a stabilizing effect. However, the most important effect was the increase in diffusion coefficient. The increase shifted the flame surface, where the large density decrease occurs, outside the shear layer of the jet and produced a thick viscous layer surrounding the jet which effectively suppressed the instability.

DEMOGRAPHIC CRISIS IN UKRAINE: STATE, CONSEQUENCES AND PROSPECTS OF OVERCOMING IT

2021 ◽  
Vol 296 (4) ◽  
pp. 114-120
Author(s):  
IRYNA KRAVETS ◽  
Keyword(s):  
Reproductive Behavior ◽  
Large Scale ◽  
Social Protection ◽  
Work Motivation ◽  
Population Aging ◽  
Population Decline ◽  
Child Rearing ◽  
Noncommunicable Diseases ◽  
Endogenous Factors ◽  
Natural Movement

The article analyzes the demographic situation in Ukraine, which has acquired signs of a demographic crisis. There has been an unprecedented decline in Ukraine’s population, which has lost a fifth in the years since independence. The current trends of population decline in the regional context have been studied. It is established that the prospects of depopulation are quite disappointing, given the low overall fertility rate, as well as the predominance of mortality over fertility. The natural movement of the population has been studied, the main causes of its high mortality, especially in working age, due to increased morbidity, in particular the high prevalence of risk factors for noncommunicable diseases, which form more than 80% of mortality in Ukraine, under the influence of endogenous, exogenous and quasi-endogenous factors. The causes of low birth rate, as well as modern features and orientations of reproductive behavior of the population are revealed. In Ukraine, there is a tendency of low life expectancy and population aging compared to some European countries. It is concluded that under such conditions large-scale depopulation will be inevitable. The peculiarities of modern migration processes, in particular labor migration, which can give impetus to alternative migration, have been clarified. The interaction of demographic processes and socio-economic development of the country is determined. Ways to overcome the demographic crisis are a set of demographic measures (organization and conduct of the census, which was not conducted for two decades, the formation of population registers, increasing financial assistance to mothers at birth in accordance with modern requirements, etc.) and socio-economic measures to strengthen reproductive behavior, flexible employment for childbirth and child rearing, improving the level and quality of life of citizens, increasing work motivation in Ukraine, social protection of citizens, etc.

The Fully Developed Wake of a Circular Cylinder

1949 ◽  
Vol 2 (4) ◽  
pp. 451 ◽  
Author(s):  
AA Townsend
Keyword(s):  
Circular Cylinder ◽  
Diffusion Coefficients ◽  
Large Scale ◽  
Turbulent Transport ◽  
Turbulent Energy ◽  
Small Scale ◽  
Mean Velocity ◽  
Turbulent Fluid ◽  
Air Stream ◽  
Scale Motion

Extending previous work on turbulent diffusion in the wake of a circular-cylinder, a series of measurements have been made of the turbulent transport of mean stream momentum, turbulent energy, and heat in the wake of a cylinder of 0.169 cm. diameter, placed in an air-stream of velocity 1280 cm. sec.-1. It has been possible to extend the measurements to 960 diameters down-stream from the cylinder, and it 1s found that, at distances in excess of 600 diameters, the requirements of dynamical similarity are very nearly satisfied. To account for the observed rates of transport of turbulent energy and heat, it is necessary that only part of this transport be due to bulk convection by the slow large-scale motion of the jets of turbulent fluid emitted by the central, fully turbulent core of the wake, which had been supposed previously to perform most of the transport. The remainder of the transport is carried out by the small-scale diffusive motion of the turbulent eddies within the jets, and may be described by assigning diffusion coefficients to the turbulent fluid. It is found that the diffusion coefficients for momentum and heat are approximately equal, but that for turbulent energy is considerably smaller. On the basis of these hypotheses, it is possible to calculate $he form of the mean velocity distribution in good agreement with experiment, and to give a qualitative explanation of the apparently more rapid diffusion of heat.

1-D Model Analysis of Tesla Turbine for Small Scale Organic Rankine Cycle (ORC) System

2017 ◽  
Author(s):  
Jian Song ◽  
Chun-wei Gu
Keyword(s):  
Large Scale ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Axial Flow ◽  
Rankine Cycle ◽  
Expansion Ratio ◽  
Working Fluid ◽  
Small Scale ◽  
Low Grade ◽  
D Model

Energy shortage and environmental deterioration are two crucial issues that the developing world has to face. In order to solve these problems, conversion of low grade energy is attracting broad attention. Among all of the existing technologies, Organic Rankine Cycle (ORC) has been proven to be one of the most effective methods for the utilization of low grade heat sources. Turbine is a key component in ORC system and it plays an important role in system performance. Traditional turbine expanders, the axial flow turbine and the radial inflow turbine are typically selected in large scale ORC systems. However, in small and micro scale systems, traditional turbine expanders are not suitable due to large flow loss and high rotation speed. In this case, Tesla turbine allows a low-cost and reliable design for the organic expander that could be an attractive option for small scale ORC systems. A 1-D model of Tesla turbine is presented in this paper, which mainly focuses on the flow characteristics and the momentum transfer. This study improves the 1-D model, taking the nozzle limit expansion ratio into consideration, which is related to the installation angle of the nozzle and the specific heat ratio of the working fluid. The improved model is used to analyze Tesla turbine performance and predict turbine efficiency. Thermodynamic analysis is conducted for a small scale ORC system. The simulation results reveal that the ORC system can generate a considerable net power output. Therefore, Tesla turbine can be regarded as a potential choice to be applied in small scale ORC systems.

scholarly journals Case Report: Efficacy of Pyrotinib in ERBB2 Amplification Pulmonary Adenoid Cystic Carcinoma

2021 ◽  
Vol 11 ◽  
Author(s):  
Zhongben Tang ◽  
Feng Lin ◽  
Jiarong Xiao ◽  
Xiaojun Du ◽  
Jian Zhang ◽  
...  
Keyword(s):  
Targeted Therapy ◽  
Adenoid Cystic Carcinoma ◽  
Large Scale ◽  
Case Reports ◽  
Growth Factor Receptor ◽  
Low Grade ◽  
Adenoid Cystic ◽  
Epidermal Growth ◽  
Low Incidence ◽  
Current Report

Primary pulmonary adenoid cystic carcinomas are salivary tumors that are low-grade malignant and prone to recurrence and metastasis. Surgery is currently the main treatment, but there is no standard with regard to postoperative adjuvant therapy. Adenoid cystic carcinoma is more sensitive to radiotherapy and patients benefit less from chemotherapy, but few studies have focused on targeted therapy, and their conclusions are inconsistent. With respect to primary pulmonary adenoid cystic carcinoma, large-scale studies cannot be conducted due to its low incidence, and studies on the targeted therapy of it are very scarce. A few case reports indicate that targeted therapy can be effective however, suggesting that it may be a good option. The current report is the first on the occurrence of human epidermal growth factor receptor 2 amplification in pulmonary adenoid cystic carcinoma. The patient was treated with pyrotinib for 6 months and achieved stable disease.

The Analysis and Application of Energy-Internet in the Low-Carbon Community

2010 ◽  
Author(s):  
Hao Liang ◽  
Weiding Long ◽  
Yingqian Song ◽  
Fang Liu
Keyword(s):  
Renewable Energy ◽  
Large Scale ◽  
Energy Use ◽  
Optimal Path ◽  
Energy Generation ◽  
Hot Water ◽  
Low Grade ◽  
Low Carbon ◽  
Urban District ◽  
Energy Internet

The energy-Internet is a new energy supply method based on urban compact and densely populated community in a low-carbon city. The principle is to connect small energy generation stations and combined heat and power system (CHP) based on distributed energy technology and renewable energy into a network in the urban district. In this way, the cooling, heating and electricity could all back each other up. Each building of the community could collect the energy and then put that energy into the energy-internet to supply the heating and power to buildings. The power in the energy-internet could also be used for charging electric vehicles. So the energy use in the urban community would be basically self-sufficient. The energy generation stations in the energy-internet could be solar power, wind power, biomass cogeneration (including refuse power generation), household fuel cell, low-grade heat in rivers, lakes, urban sewage and soil. In this way, large-scale renewable energy and unused energy could be fully used and applied in a compact and dense community. If the energy-internet is suitable designed, the equipment capacity, energy consumption and CO2 emission of the community could be greatly reduced, energy efficiency could be optimized and improved and the heat island effect could also be alleviated. This article explores three major problems of the construction of energy internet and their solutions: namely, the location and layout of the energy station, the environmental economic dispatch model of the energy internet with power dispatching as an example, the optimal path design of hot water pipe network combined with graph theory and genetic algorithms.

Diffusion Driven Desalination for Simultaneous Fresh Water Production and Desulfurization

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Jameel R. Khan ◽  
James F. Klausner ◽  
Donald P. Ziegler ◽  
Srinivas S. Garimella
Keyword(s):  
Fresh Water ◽  
Fluid Transport ◽  
Transport Model ◽  
Waste Heat ◽  
Feed Water ◽  
Low Grade ◽  
Water Production ◽  
Air Stream ◽  
Mass Transport Model ◽  
Air Streams

The diffusion driven desalination (DDD) process has been previously introduced as a process for distilling water using low-grade waste heat. Here, a configuration of the DDD process is introduced for simultaneously distilling water and scrubbing sulfur dioxide (SO2) out of heated air streams, which is also known as flue gas desulfurization (FGD). This novel DDD/FGD process utilizes the low-grade waste heat carried in industrial discharge air streams. There are many applications, where the industrial air discharge also contains SO2, and in order to utilize the waste heat for the DDD process, the SO2 must be scrubbed out of the air stream. The two major components of the DDD process are the diffusion tower and the direct contact condenser. In the present work, a thermal fluid transport model for the DDD/FGD process, that includes SO2 scrubbing, is developed. It is an extension of the heat and mass transport model previously reported for the DDD process. An existing laboratory scale DDD facility was modified and tested with SO2 in the air stream and with seawater as the feed water to the diffusion tower. The experimental investigation has been completed to evaluate the fresh water production and SO2 scrubbing potential for the DDD/FGD process. The experimental results compare favorably with the model predictions. Chemical analysis on the condenser water demonstrates the capability of the DDD/FGD process to produce high quality fresh water using seawater as the input feed water to the process.

scholarly journals Hydrodynamic and Flotation Kinetic Analysis of a Large Scale Mechanical Agitated Flotation Cell with the Typical Impeller and the Arc Impeller

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 79 ◽  
Author(s):  
Zhengchang Shen ◽  
Ming Zhang ◽  
Xuesai Fan ◽  
Shuaixing Shi ◽  
Dengfeng Han
Keyword(s):  
Large Scale ◽  
Hydrodynamic Performance ◽  
Collision Probability ◽  
Collision Kernel ◽  
Low Grade ◽  
Performance Parameters ◽  
Effective Volume ◽  
Mineral Particles ◽  
Flotation Cells ◽  
Flotation Cell

The processing of low grade mineral ores using large scale flotation cells is obviously more advantageous than smaller-scale processing. Large-scale flotation cells have become increasingly important for effective volume scale-up. In this study, the latest and largest flotation cell in China, with an effective volume of 680 m3, is considered. Hydrodynamics and flotation kinetics analyses are conducted using computational fluid dynamics (CFD) simulation. It is demonstrated that the flotation cell with a typical impeller produces suitable hydrodynamics for mineral particles based on analysis of the flow pattern, gas dispersion and solid suspension. The performance of the large-scale flotation cell is studied using hydrodynamic performance parameters. The variation of the performance parameters, such as the power number (Np), the Froude number (Fr), the air flow number (Na), and so on, with the flotation cell volumes, followed trends similar to that of previous cells of a different size, which were proven to be effective for engineering applications. To decrease the detachment of mineral particles, a new type of impeller, for which the impeller plate is a hyperbolic curve, viz. an arc impeller, was developed. Compared with the typical impeller, the arc impeller expands and lifts the low circulating flow, thereby shortening the transportation distance of the mineral particles. The data indicates that kinetic eddy dissipation plays a key role in determining the collision kernel and collision probability profile. The newly designed arc impeller leads to a higher collision probability than the typical impeller, resulting in better flotation performance. This research should aid in the optimization of the structure of the 680 m3 flotation cell.

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