Inside Column Research Articles

Bioleaching of a lateritic ore (Piauí, Brazil) in percolators

Heap leaching of laterites for extraction of nickel and cobalt is an attractive alternative to capital and energy intensive high pressure acid leaching, the dominant hydrometallurgical processing technology for limonitic laterites. Conventional approach for heap leaching of laterites is leaching with sulfuric acid. Consumption of sulfuric acid during heap leaching is substantial and industrial-scale operations require construction of a sulfuric acid production plant on site. In this study, heap bioleaching of laterites was simulated in laboratory scale column percolators and bioleaching of nickel and cobalt from lateritic material was successfully demonstrated for the first time. The process is based on biooxidation of the bacterially modified “wet sulfur” inside column percolators by sulfur-oxidizing acidophilic bacteria Acidithiobacillus thiooxidans. The “wet sulfur“ was generated in a bioreactor with the bacterial culture, harvested, and mixed with lateritic ore before forming agglomerates to be filled in the percolator columns. Liquid was circulated with a flow rate of 8 mL/min. Maximum metal extraction was 66% nickel, 95% cobalt, 10% iron, 55% magnesium and 89% manganese from the Piauí lateritic ore after one month bioleaching. For comparison, chemical leaching with 1 M sulfuric acid with or without addition of 10 g/L of ferrous sulfate heptahydrate as reductant resulted in extraction of approximately 80% nickel, 86% cobalt, 33% iron, 50% magnesium and 81% manganese. With bioleaching a higher cobalt but lower nickel and iron extraction was achieved, i.e. a better selectivity of nickel over iron extraction, as well as a relatively higher pH of the pregnant leach solution requiring less limestone and, consequently, lower CO2 emission and generation of iron cake waste in case of laterite bioleaching. Overall, the results are promising and show potential of laterite heap bioleaching to be further developed to application on industrial scale.

A multiphase dynamic programming algorithm for the shortest path problem with resource constraints

The shortest path problem with resource constraints (SPPRC) finds a least cost path between two nodes in a network while respecting constraints on resource consumption. The problem is mainly used as a subproblem inside column generation for crew scheduling and vehicle routing problems. The standard approach for the subproblems is based on dynamic programming (DP). This class of methods is generally effective in practice when there are only a few resources, but it seems to be time-consuming for huge instances with many resources. To handle this issue, we propose a new exact primal algorithm called the multiphase dynamic programming algorithm (MPDPA) to solve the SPPRC in acyclic networks. The proposed approach splits the state-space into small disjoint subspaces. These subspaces are sequentially explored in several iterations, where each iteration builds on the previous ones, to reduce the dimension of the subspaces to explore and to quickly generate better paths. Computational experiments on vehicle and crew scheduling instances show the excellent performance of our approach compared to the standard DP method. On the one hand, MPDPA returns optimal solutions while achieving time reduction factors between 1.44 and 3.59 on average compared to DP. On the other hand, MPDPA is able to generate feasible paths with up to 90% of the optimal cost in less than 10% of the time required by standard DP. This feature is useful in column generation and may greatly reduce the computational effort, because we can stop the MPDPA solution process once columns with sufficiently negative reduced costs are obtained.

Slope stability analysis due to infrastructure development of Ratu Boko site Yogyakarta Indonesia under earthquakes loading

The Ratu Boko site is a cultural heritage that has a high historical value and located about 30 kilometers to the east of Yogyakarta. Instability of the slope occurred due to the Yogyakarta earthquake in 2006, and it was indicated by the occurrence of cracks in the resto building that built on the top of the hill. The first reinforcement of the columns and foundations of the outside building was used a reinforced concrete that built-in 2012. The similar reinforcement on the inside building column and foundation was finished in 2017. In this research the displacement of the reinforced foundation, and slope stability generally both in safety factor and deformation were evaluated. The deformation and displacement analysis of the foundation were solved using Finite Element Analysis. On the other hand, for the safety factor of the slope, Limit Equilibrium Method was used. The simulation is divided into several stages, starting from the existing condition, after the first and second reinforcement, and also after increasing load due to development plan. Based on the numerical simulation, the horizontal displacement on the foundation of Plaza Andrawina decreases after the first and second reinforcement was installed. The horizontal displacement is significantly decreased in both foundations for 9.44 mm and 8.03 mm. Furthermore, the safety factor of the slope increases after the first and second reinforcement was installed. The slope safety factor using a maximum acceleration of 0.30g is 1.318. These obtained results are relatively safe from slope failures.

An experimental study on reactive filter bed for aluminium removal from water

AbstractIn this study, batch and column experiments were conducted to adsorb Aluminium (Al3+) from aqueous solution. The study examined the possibility of using proposed reactive filter bed media (packed with hematite or hematite sand mixture) for contaminated water treatment. Batch experiments were carried out at pH 7 ± 0.5 and initial Al3+ concentration of 1.5 mg/L. Adsorption equilibrium was achieved in more than 2 hours for hematite and 1 hour for hematite coated sand while conducting batch experiment and the maximum adsorption qm was found to be 3.38 mg/g for hematite mixture sand. From column experiment, the maximum Al adsorption capacity from four different columns was calculated to be approximately 2.2 mg/g and it was found in columns 1 and 3 packed with hematite sand mixture particles. The results indicated that both electrostatic attraction and chemical sorption could be the mechanism for Al3+ removal by hematite sand mixture particles from aqueous solution. Redox values (250 to 300 mV) inside column 3 suggested oxidizing condition during column operation. The continuous changes in redox potential (Eh) and pH indicated the occurrence of redox reactions between Al3+ and reactive media under the prevailing experimental conditions.

10.19: The steel and fibre‐reinforced concrete circular hollow section composite column exposed to fire

ABSTRACTThe recent development in technology of production and transport of the steel fibre‐reinforced concrete enables its utilization in composite steel‐concrete structures. This work is focused on development of mechanical behaviour and design model of circular hollow section (CHS) composite steel and fibre‐concrete (SFRC) column at elevated temperature. Research includes two levels accuracy/complexity, allowing simplified or advanced approach to design following the coming changes in European standard for composite member design in fire (EN1994‐1‐2:2005) [1]. Experimental studies of the project include mechanical tests of heated fibre‐concrete samples in tension and compression, thermal behaviour under uniform and non‐uniform loading of stubs of CHS and tests of full scale SFRC CHS columns in steady‐state and transient‐state regimes. Developing advanced finite element method (FEM) simulation of global mechanical behaviour of SFRC CHS columns is a multi‐levelled composite mechanical and thermo‐model and provide numerous numerical experiments. Together with standard steel material model in fire, FEM model of mechanical behaviour of fibre‐reinforce concrete at elevated temperature is prepared. Validated simplified and advanced thermal model of SFRC CHS at elevated temperature gives temperature fields and moisture distribution inside section which depends on direction, heat flux, sizes and gives possibility to model different fire cases of full‐scale columns in bending and buckling at elevated temperature.Prepared analytical and simplified FEM mechanical model of column is taking in account degradation of mechanical properties, analytical models of transfer of heat inside column section and provides simplified solutions for designers.

Is the growth of microorganisms limited by carbon availability during chalcopyrite bioleaching?

Microorganisms, which play a key role during mineral dissolution in bioleaching processes, require O2 to promote the oxidation processes of sulfide mineral dissolution and CO2 or more complex molecules as carbon source for cell growth. Preliminary models have been proposed for relating the microbial succession in bioleaching heaps with the activity of different CO2 fixation pathways. The increase of internal heap temperature during bioleaching improves the rate of chalcopyrite dissolution. However, it also negatively affects CO2 and O2 availability, consequently the microbial community changes and only the best adapted microorganisms are capable of growing under the limiting conditions. In this work we attempt to elucidate how microbiological succession proceeds in a semi-industrial bioleaching column test system, with emphasis in determining the identity of the microorganisms participating and the metabolic dynamics of carbon fixation pathways. In silico reconstruction of the carbon fixation metabolisms based on available genomes and the gene expression studies using microarray and RNA-seq were performed. The physicochemical conditions and the metallurgical parameters were also included in the analysis. Although the investigation is based on a non-homogeneous system - which leads to some seemingly contradictory data - the results showed a clear change in the structure of the microbial community as well as in the expression of pathways for CO2 fixation, as the column test progressed. These changes were directly related to two factors, the temperature inside column and the CO2 availability. The gene expression analyses confirmed the temporal distribution of microorganisms as a function of the temperature and the different pathways for CO2 fixation. The evidences obtained here support the fact that low CO2 availability becomes an important asset to the microbial population survival and growth promotion in the bioleaching environments. The determination of the expression level of the key genes is a good opportunity to improve a sound understanding of the high temperature bio-assisted heap leaching of chalcopyrite and to optimize the technology.

Wall effects on the thermocapillary migration of single gas bubbles in stagnant liquids

In this paper, the governing continuum conservation equations for two-phase flow are solved using the commercial software package (Ansys-Fluent 1) to investigate the thermocapillary movement of a single bubble in stagnant liquid under zero-gravity condition. The current results show that different temperature gradients lead to different bubble migration velocities, and bubble migration velocity varies linearly with the temperature gradient for the given conditions. Furthermore the inside column diameter was found to have a significant influence on the thermocapillary migration of the bubble. Calculation were made in columns with inside diameters Dr 15, 20, 30, 40, 60, 80, 100 and 120 mm. Reduction on bubble migration velocity only occurred when the ratio of the bubble diameter to the column diameter, db/Dr, is greater than 0.267 due to column wall effect. On the other hand, the influence of the column diameter on the rise velocity is negligible when db/Dr is equal to or smaller than 0.267. No bubble shape deformation were observed and the bubble were spherical in shape for all column width. Present investigation of the shape and trajectory of bubble motion driven by surface tension-gradient in different column width is a new area of study and aims to support research into space applications which can help to determine the new migration time and speed.

Discussion of “Plugging effect of open-ended piles in sandy soil”

Discussion of <b>“</b>Plugging effect of open-ended piles in sandy soil”

Comparison of a plant based natural surfactant with SDS for washing of As(V) from Fe rich soil

This study explores the possible application of a biodegradable plant based surfactant, obtained from Sapindus mukorossi, for washing low levels of arsenic (As) from an iron (Fe) rich soil. Natural association of As(V) with Fe(III) makes the process difficult. Soapnut solution was compared to anionic surfactant sodium dodecyl sulfate (SDS) in down-flow and a newly introduced suction mode for soil column washing. It was observed that soapnut attained up to 86% efficiency with respect to SDS in removing As. Full factorial design of experiment revealed a very good fit of data. The suction mode generated up to 83 kPa pressure inside column whilst down-flow mode generated a much higher pressure of 214 kPa, thus making the suction mode more efficient. Micellar solubilisation was found to be responsible for As desorption from the soil and it followed 1st order kinetics. Desorption rate coefficient of suction mode was found to be in the range of 0.005 to 0.01, much higher than down-flow mode values. Analysis of the FT-IR data suggested that the soapnut solution did not interact chemically with As, offering an option for reusing the surfactant. Soapnut can be considered as a soil washing agent for removing As even from soil with high Fe content.

Short term effects of cassava processing waste water on some chemical properties of loamy sand soil in Nigeria

The short term changes in the concentration of some of the major constituents of cassava waste water and their corresponding effects on some of the soil exchangeable cations were studied following surface application of cassava waste water. The leaching experiment with de – ionized water was carried out on soil inside column under conditions of saturated flow. Samples of leachate were taken at 10 cm interval down the soil columns and were analyzed for NO3-, Cl-, Ca2+, Mg2+ and Na+. After the column leaching, soil samples were collected from the columns at the depth of 10, 20, 30, 40 and 50 cm for the analysis of pH, soil organic matter and some exchangeable cations. Cassava waste water application caused a distinct decrease in the concentrations of the anions and cations introduced through the waste water. However, concentration of the anion in the samples of the leachate collected down the soil columns on the average decreased with the depth of the soil column while the concentration of the cations increased with the depth of the column. The application of cassava waste water also caused a distinct rise in soil organic matter at all the depths of sampling. However, the application resulted in a distinct fall in the soil pH. Highest values of soil pH were observed at 0 to 10 cm depth while the lowest were observed at 10 to 20 cm depth for the control, 5 and 10 days resident time experiments. The highest Na+ concentration of 0.75 cmol/kg was observed at the soil depth of 20 cm while the lowest (0.47 cmol/kg) was at 10 cm soil depth. The highest soil Ca2+concentration of 2.80 cmol/kg was at the soil depth of 20 cm while the lowest concentration of 2.60 cmol/kg was at the soil depth of 30 cm. The lowest soil Mg2+ concentration of 0.34 cmol/kg was at the depth of 10 cm while the highest of 0.72 cmol/kg was at the depth of 50 cm. Key words: Short term, cassava, wastewater, chemical properties, loamy sand soil.

EVALUATION OF BEARING STRENGTH OF CONCRETE FILLING IN STEEL COLUMNS

This paper describes the bearing strength of concrete filling in a steel column. Single or double tubular column specimens filled with concrete that have mechanical shear keys, were tested under compressive and tensile load. The test results verified that the width to thickness ratio of column influenced on the bearing strength of concrete filling in a steel column, and the influence of number of the mechanical shear keys, embedded depth of the inside column and eccentricity of the inside column were small. Local stress states near the mechanical shear keys were modeled and the yield condition by Mohr-Coulomb applied to the stress state. Based on the model, the equations of evaluating the bearing strength were derived and its validity was confirmed.

Analysis of Multiple Jets in the Schwarz Melt-Blowing Die Using Computational Fluid Dynamics

Melt-blowing dies are used industrially to fabricate fine polymer fibers. The Schwarz die is a type of melt-blowing die that uses multiple columns of polymer orifices and associated air jets. This arrangement contrasts with the single column of orifices that is used in the slot, or Exxon, die. The experimental measurements of the air flow field from a Schwarz die can be reproduced using a k-e turbulence model. Six different multihole die geometries were simulated in 3D with this model. In comparison with the flow field of a single jet, the velocity maximums occurred closer to the die face for an array of jets. The spreading rates for the center jets of the multihole dies were similar to each other, and close to 0.5, while the spreading rate of a single annular jet has been observed to be close to twice this value. In addition, the differences in the air fields of the multihole geometries lead to observations concerning multiple jet interactions. The distance required for the inside column of jets to affec...

Effect of spandrel beams on strength and behaviour of column-slab connections

Spandrel beams are commonly used to strengthen the connections between slabs and edge columns in flat slab structures. The present study uses experimental and analytical means to improve understanding of the behaviour of these connections, especially when spandrel beams are used. The parameters considered are the spandrel beam size and reinforcement ratio, the width of the inside column slab interface, and the type of straining actions to be transferred through the connection. The efficiency of using a slab extension (beyond column outer face) instead of a spandrel beam is also studied. Based on the failure mechanism observed during the tests, a new analytical method to predict the strength of edge column-slab connections is suggested. A second analytical method is also developed while being based on a simplified failure surface. The accuracy and reliability of both methods are thoroughly assessed in this study.

LIQUID PHASE DISPERSION IN A PACKED COLUMN WITH COUNTERCURRENT TWO-PHASE FLOW

The axial dispersion in the liquid phase through a packed column was studied with air-water flowing counter-currently in a 10.16 cm inside diameter column packed with Percelain Raschig rings. The dispersion coefficient or Peclet number and mean residence time were calculated by comparing the moments of the responses measured at two points along the column. Effects of gas flow rate (0-0.37 kg/m2 sec), liquid flow rate (2.1-18.5 kg/m2 sec) and packing size (1.27,0.95,0.64 cm R.R.)on the liquid phase Peclet number and hold-up were investigated and compared with previous results.

A Theoretical Study of the Compensating Downward Motions Associated with Cumulus Clouds

Abstract An attempt is made to investigate theoretically the controlling influence of compensating downward motions on the development of cumulus clouds and the size of the cloudless areas associated with them. The model consists of two circular concentric air columns, the inside column corresponding to the updraft (cloud) region and the outside concentric annular column to the downward motion region. The combined cell is surrounded by the atmospheric at rest. The governing equations of both the updraft and the compensating downward motion are derived from the conservation equations of momentum, heat, moisture and mass. The differential equations are solved numerically to compute the vertical velocity, temperature, specific humidity and liquid water content in and out of the cloud as functions of height and time. Two experiments were performed with and without the effect of compensating downward motion. The main conclusions are the following: Without the effect of the compensating motion, the structure of...

細胞状積雲対流の特性について

A study is made of cellular cumulus convection in a conditionally unstable atmosphere which is unstable for moist ascending motion and stable for dry descending motion. The convection cell under consideration is confined in a cylindrical column : the inside column corresponds to a moist ascending region and the outside annular column corresponds to a dry descending region, while there are an inflow in the lower layer and an outflow in the upper layer.Attention is focused mainly on the evaluation of steady upward heat transport for various values of the size of the cell and the ratio between the ascending and descending areas. A preferred mode of convection is determined by assuming that convection must develop to maximize upward heat transport. It is shown that the present model reduces to a buoyant plume model as a special case when the horizontal scale of the convection cell becomes small compared to its depth and the descending area becomes large.