Slurry

A Jet erosion tester is designed and used to study the relative erosion behavior of high chromium white cast iron (ASTM 532A) at specific concentration of silica sand as an abrasive material, 45° impact angle and two size of abrasive particles. A slurry pot was used which contains two propellers rotated at the speed required for uniform distribution. The test specimens are mounted on test fixture which is fixed and has a provision to move in different angular position to find out the wear for different angles. Two different experiments are conducted preliminarily by using silica sand as abrasive with particle size of 400-600 µm and 600-800 µm. Impact angle of 45° and solid abrasives of 20% wt. concentration are used as fixed parameters for 10 hours. It was found that the erosion resistance decreases with increasing the abrasive particle size.

In this paper, a dynamic model of a slurry mixing and pumping process is proposed. The centrifugal pump is modeled based on the hydraulic application, the hydraulic part and the induction motor models, taking into account the pumped slurry density. This paper also proposes a new approach to estimate the parameters of the pump's hydraulic part model based on the pump characteristic curves. Additionally, a dynamic simulation of the system is realized under MATLAB/Simulink environment and the variation effect of the process inputs on the outputs is studied.

This paper examines effective and environmentally friendly materials intended for noise insulation and soundproofing applications, starting with materials that have gained significant attention within last years. Foam-formed materials based on cellulose fibers have emerged as a promising solution. The aim of this study was to obtain a set of foam-formed, porous, lightweight materials based on cellulose fibers from a resinous slurry pulp source, and to investigate the impact of surfactant percentage of the foam mixtures on their noise insulation characterisitcs. The basic foam-forming technique was used for sample assembly, with three percentages of sodium dodecyl sulphate (as anionic surfactant) related to fiber weight, and a standardised sound transmission loss tube procedure was used to evaluate noise insulation performance. Results were obtained as observations of internal structural configurations and material characteristics, and as measurements of sound absorption/reflection, ...

Platinum-group element (PGE) deposits in the Bushveld Complex and other layered intrusions form when large, incompletely solidified magma chambers undergo central subsidence in response to crustal loading, resulting in slumping of semi-consolidated cumulate slurries to the centres of the intrusions and hydrodynamic unmixing of the slurries to form dense layers enriched in sulfides, oxides, olivine and pyroxene and less dense layers enriched in plagioclase. The most economic PGE, Cr and V reefs form in large, multiple-replenished intrusions because these cool relatively slowly and their central portions subside prior to termination of magmatism and complete cumulate solidification. The depth of emplacement has to be relatively shallow as, otherwise, ductile crust would not be able to flex and collapse. In smaller intrusions, cooling rates are faster, subsidence is less pronounced and, where it occurs, the cumulate may be largely solidified, resulting in insignificant mush mobility and mineral sorting. Layering is thus less pronounced and less regular and continuous and the grades of the reefs are lower, but the reefs can be relatively thicker. An additional factor controlling the PGE, Cr and V prospectivity of intrusions is their location within cratons. Intracratonic environments offer more stable emplacement conditions that are more amenable to the formation of large, layered igneous bodies. Furthermore, intrusions sited within cratons are more readily preserved because cratons are underlain by thick, buoyant keels of harzburgite that prevent plate tectonic recycling and destruction of crust.

Recently, polyacrylamide (PAM) has been widely used in polymer flooding technology to enhance oil recovery and oil production. However, the difficulty in removing hydrolysed PAM (HPAM) from wastewater still seriously blocks the further application of polymer flooding in the oilfields. Herein, we demonstrate the preparation of SiO 2 @TiO 2 :Eu 3+ @TiO 2 core double-shell microspheres (STT) through a two-step solvothermal and sol-gel coating strategy. The as-prepared STT exhibits an ideal photocatalytic activity for the photodegradation of HPAM. More importantly, by using STT as the model, the correlation between fluorescence intensity and photocatalytic activity of the photocatalysts is investigated. The results suggest their oppositional relationship. Since many kinds of photocatalysts are utilized in the degradation of organic pollutants, it is believed that our work will not only promote the development of photocatalysis in the field of oil extraction, but also offer a convenient method for evaluating the photocatalytic activity of the photocatalysts.

In the present investigation, the effect of plasma nitriding on the microabrasion behaviour of sintered unalloyed iron is investigated. Plasma nitriding was carried using two different sets of operative parameters in order to produce microstructures composed of different dominants iron nitrides, e.g. Fe 4 N (c9) and Fe 2-3 N (e), phases. Microabrasive wear tests were carried out in a 'free ball' microabrasion tester using SiC slurries. The tribological parameters were kept constant during the tests. The microstructures constituted of e-(Fe 2-3 N) phase presented a superior abrasion resistance.

The properties, types, and physical and chemical aspects of pig slurry used in the fermentation process were presented. Characterization of the pig slurry microflora for a controlled biogas production process was performed. A pilot biogas treatment installation was presented on the example of a farm with 1100 Dan Bred fatteners kept in a grate system. The research was carried out to measure the biogas flow rate resulting from the reference pressure in the fermentor. An independent assessment of the amount of biogas and the pressure drop in the skeletal deposit was carried out. The basis for assessing the hydrodynamics of gas flow through the adhesive bed is the flow characteristic, which results from the pressure that forces this flow. In each case, the determination of this characteristic consists in determining the influence of the biogas stream on the value of this overpressure, equivalent to the pressure drop (it is tantamount to determining the total biogas flow resistance thro...

The article reviews selected methods and techniques of agricultural biogas desulphurization. Presented is the current state of technological and measurement systems as well as raw biogas purification methods in terms of control and measurement-socio-economic aspects were also pointed out. On the example of a pilot agricultural biogas with the use of pig slurry, the required technical and technological criteria for the production and processing of agricultural biogas were indicated. The article presents the preliminary results of experimental studies on the course of changes in the volumetric composition of biogas on the basis of the average daily production of agricultural biogas.The amount of H2S in raw and purified biogas was analyzed with the proprietary biogas desulphurization method in terms of the process parameters. A novelty is the use of a developed carbon mixture (activated carbon) with turf ore (iron compounds), which allows for 100% desulfurization of raw agricultural bi...

Elevated As concentrations in shallow groundwater pose a major health threat in Bangladesh and similarly affected countries, yet there is little consensus on the mechanism of As release to groundwater or how it might be influenced by human activities. In this study, the rate of As release was measured directly with incubations lasting 11 months, using sediment and groundwater collected simultaneously in Bangladesh and maintained under anaerobic conditions throughout. Groundwater and grey sediment were collected as diluted slurries between 5 and 38 m depth, a range over which ambient groundwater As concentrations increased from 20 to 100 μg L -1 . Arsenic was released to groundwater in slurries from 5 and 12 m depth at a relatively constant rate of 21 ± 4 (2 σ) and 23 ± 6 μg As kg -1 yr -1 , respectively. Amendment with a modest level of acetate increased the rate of As release only at 12 m (82 ± 18 μg kg -1 yr -1 ). Although the groundwater As concentration was initially highest at 38 m depth, no release of As was observed. These results indicate that the spatial distribution of dissolved As in Bangladesh and local rates of release to groundwater are not necessarily linked. Iron release during the incubations did not occur concurrently with As release, providing further confirmation that the two processes are not directly coupled. Small periodic additions of oxygen suppressed the release of As from sediments at all three depths, which supports the notion that anoxia is a prerequisite for accumulation of As in Bangladesh groundwater.

Advancement in biotechnology and bioengineering has provided ways that resources, which hitherto were classified as wastes, now form the basis for energy production. Anaerobic digestion is a highly promising technology used for processing biomass materials (crop residue, human excreta, animal waste and food) in the absence of oxygen to a methane-rich biogas. This work developed a small-scale anaerobic digester to produce biogas from animal waste. The anaerobic digester consisted of three major components: bioreactor with an incorporated stirrer driven by an electric motor, gas scrubber and gas collector.  Batch feeding operation was adopted while pig waste was used as test material. Lime water was used as a scrubbing medium for methane enrichment.  Loading result revealed that there was seven days delay in gas production from day of loading. The daily temperatures and pH recorded for a period of 50 days were in the range of 29 - 34°C and 5.5 - 7.5 respectively, and the average yield...

The utilization of roadside-green-cuttings (grass) for anaerobic digestion increases provides an additional possible source of organic waste for use as a renewable energy source. Grass can be used as a substrate to increase biogas yield. Nevertheless, the anaerobic digestion of this kind of waste can be limited due to the fact that it could be contaminated with heavy metals, in particular from traffic emissions and industrial activity. For this reason the biogas production of grass from a busy road was assessed. Samples of roadside-grass were washed with an organosulphide, which is used for the removal of heavy metals from wastewater. A comparison of the anaerobic digestion of washed and unwashed roadside grass was performed. Results showed that the anaerobic digestion of the unwashed grass was much more effective than the washed grass. A second experiment was carried out and co-fermentation of manure and farm-grass was prepared for anaerobic digestion. Lead was added in the concentrations 500, 1000 and 2000 mg Pb 2+ /kg. The results showed that the higher the lead concentration, the lower the inhibition of the biogas yield. The grass could be acting as phytoremediator for high lead concentrations. The grass could contain organic compounds, which can assimilate heavy metals.

Production of biogas from animal wastes could lessen the problems of energy shortage and indiscriminate animal waste disposal. A study of anaerobic digestion of selected ratios of cattle, swine, and poultry wastes was carried out to evaluate their biogas yields. Cattle (C), swine (S), and poultry (P) wastes were mixed as C:S:

Ceramic layers based on calcium silicate non-substituted and substituted by Zn with different thickness, were developed by immersing porous Y-TZP disks into SiO 2 -CaO-ZnO-P 2 O 5 glass suspensions with ZnO contents in the range of 0-20 mol%. The effect of the disk surface porosity and the slip solid loading on the formation of the dip coated layer was investigated. Special emphasis was given to the ZnO content of the dip coating slurries and its influence on the thickness and composition of the sintered layer. The greater chemical stability of the 20 mol % ZnO-substituted glass powder during aqueous colloidal processing resulted in slips with low viscosity values; whereas the high dissolution rate of the glass having 10 mol% ZnO significantly increased the slip viscosity. The liquid entrainment mechanism at the initial stage was accelerated either by using 10 mol% ZnO-substituted glass slips or by increasing the slip solid loading. The casting rate for longer immersion times markedly increased by increasing the surface porosity of Y-TZP disks. Sintered layers with thickness ~30-70% lower were produced using the glass dip coating slip with 20 mol% ZnO in comparison to 10 mol% ZnO. The main crystalline phase of the coated sintered layers was Ca 3 Si 3 O 9 , Ca 2 ZnSi 2 O 7 and ZnSiO 4 for the glasses with 0, 10 and 20 mol% ZnO, respectively.

This paper investigates the impact of atmospheric carbon dioxide(CO2) on the electrical properties, viscosity, and surface tension of Carboxymethyl cellulose (CMCHV) and Polyanionic cellulose (PACLV) when dissolved in water used for oil extraction. The research reveals that as carbon dioxide concentrations increase, the conductivity, viscosity, and surface tension of these substances also increase, albeit to varying extents. The findings suggest that the presence of carbon dioxide in the atmosphere can alter the physical properties of CMCHV and PACLV when they are dissolved in water used for oil extraction in oilfields and wells. This is significant because these substances are commonly used in solid-laden and water-based drilling fluids, where high viscosity can impede the filtration rate of many water-based drilling fluids. Ideally, these substances should have low viscosity. The results of this study can be used to modify the physical properties of CMCHV and PACLV, particularly their viscosity, to mitigate the effects of carbon dioxide on their behavior

Organically enriched sediment has been found in water environments. The tsunami originating from the Great East Japan Earthquake in 2011 deposited large amount of sediment, thus providing evidence about its huge accumulation in coastal marine areas possibly due to human activities such as fish culture and marine product processing of industries. Here, degradation potential of organically enriched sediment deposited on a coastal site at Higashi-Matsushima, Miyagi, Japan was investigated under both sulfate-and iron-reducing conditions. Sediment slurry was prepared by mixing the sediment with artificial seawater. The effects of supplementation with sulfate and lepidocrocite (a crystalline Fe[III] oxide) on the structure and activity of the slurry microorganisms were examined by the combined physicochemical analyses and 16S rRNA deep sequencing. The sediment slurry was incubated for 5 days, during which the concentrations of TOC, sulfate, and ferrous iron remained at constant levels and the TG-DTA patterns did not change. The composition of dominant members of the microbial communities was stable, although the rare microbial populations slightly changed. The result in this study revealed that the organically enriched sediment was resistant to biodegradation under the sulfateand iron-reducing conditions.

Steel corrosion and erosion-corrosion have an important role in oil fields utilizing steel pipelines. Therefore; in the present work corrosion, erosion and erosion-corrosion tests are studied individually to investigate the interaction between corrosion and erosion processes and to quantify the synergy (that caused by erosion) in realistic flow environments.

In order to prolong the shelf life of the pineapple, one of the methods that can be applied is spray drying. Ultrasonic Spray Drying (USD) relies on an electromechanical device that vibrates at a very high frequency. The main objective of this work is to study the effect of maltodextrin concentrations and pre-heat slurry temperature in order to improve pineapple powder yield and moisture content. The spray dryer model used was equipped with ultrasonic system and the samples were run at different preheat slurry temperatures of 30°C , 40°C, and 50°C. Maltodextrin (MD) was used as a carrier agent at different concentrations ranging from 10% to 30% w/w. The pineapple powder then was analyzed for its yield, moisture content and colour. It was found that at higher pre-heat slurry temperature and MD concentration, the drying yield of pineapple powder had also increased. The moisture content of pineapple powder decreased with an increase of preheat slurry temperatures and MD concentration. The pineapple was found to be spray dried best at 40°C pre-heat slurry temperature with 20% w/w MD concentration highest yield recorded was 127 g. It was observed that the lightness colour of the powder is the highest at 40°C of slurry temperature and 20% w/w MD concentration. The pineapple slurry with high water to pineapple ratio resulted in low moisture content. In addition, the result shows that an increased amount of pineapple slurry and MD concentrations gives higher pineapple powder.

This research presents the case for design and development of Coal Water Slurry (CWS) Plant for industrial use in Pakistan. After exclusive comparison between coal quality quantification for CWS it was found that Darra mines at Pakistan provide best coal for CWS. Highly volatile, A and B Bituminous coal and Sub-Bituminous coal is selected for making CWS because of its low Sulfur contents, Ash contents and high heating value through experimentation. The purpose of this research was to present a complete blue print for the production of coal water slurry fuel in Pakistan. The measured viscosity and heat contents of the tested CWS are of the order 490 mPa-sec and 23.8 KJ/kg, respectively.

Plasma Sprayed coatings provide protection against corrosion, erosion and wear. Inconel-718 is a metallic coating which has good wear and erosion resistance. This is plasma sprayed on to Al6061 substrate and then subjected to slurry erosive wear tests. It is observed that the slurry wear rates of Al6061 decreased on coating the substrate material with

The key issue associated with the industries is the transportation and dumping of solids particulates in the form of slurry at the desired place using long length pipelines. In this perspective, numerical simulation of three-dimensional horizontal slurry pipeline of 0.0549 m diameter using Eulerian two-phase model with RNG kɛ turbulence closure is carried out. The glass -beads solid particulates having density (  = 2470 kg/m 3 ) and slurry concentration varies as 10% to 50% (by volume) for velocity ranges of 3-5 ms -1 . The computational modeling is done using available commercial software ANSYS Fluent for 125µm and 440 µm particulate size at different velocity and concentration range to know their effect on slurry flow characteristics. It is observed that for chosen particulate size pressure drop increases with increase in velocity at all solid concentration range. The pressure drop in slurry for 440 µm solid particulates is found higher as compared to the pressure drop of 125 µm solid particulates slurry. The percentage change in pressure drop is also reported in the paper due to particulate size effect at all velocity and solid concentration. The obtained results of predicted pressure drop are analytically compared with the available experimental results of literature and are in synchronism with that. A parametric study is carried out with the aim of visualizing and understanding the solid particulate size effect on slurry flow characteristics. Finally, the results of settling solid concentration contour, velocity contour, concentration profiles, velocity profiles and vector representation of concentration/velocity were also predicted for chosen particulates sized slurry.

Ceramic slurry wastes have a significant hazardous potential when dumped. Their recycling as raw material is a sustainable approach for the development of nature-friendly applications. The microstructure and mechanical properties play a key role in the success of this sustainable recycling. Ceramic slurry samples resulting from the wall and floor tiles production facility were analyzed. The mineral composition was investigated by XRD combined with mineralogical microscopy and the microstructure was investigated by SEM microscopy coupled with EDX spectroscopy and elemental mapping. The ceramic slurry contains: quartz, kaolinite, mullite and small amounts of lepidocrocite. Quartz and mullite particles have sizes in the range of 5-100 µm and kaolinite has small particles of around 1 to 30 µm. Iron hydroxide crystallized as lepidocrocite is finely distributed among kaolinite aggregates. It makes the slurry unable to be reused in the technological process because of the glaze staining risk, but it does not affect the material cohesion. Thus, the cylindrical samples were prepared at progressive compactions rates as follows: 1808.55; 1853.46; 1930.79 and 2181.24 kg/m 3 and dried. Thereafter, were subjected to a compression test with a lower compression strength of 0.75 MPa for lower density and a higher strength of 1.36 MPa for the higher density. Thus, slurry compaction enhances the kaolinite binding ability. The Young's Modulus slightly decreases with the compaction increasing due to local microstructure rigidizing. This proves the binding ability of kaolinite, which properly embeds quartz and mullite particles into a coherent and resistant structure. The fractography analysis reveals that fracture starts on the internal pores at low compaction rates and throughout the kaolinite layer in the samples with high compactness. The observed properties indicate that the investigated ceramic slurry is proper as a clay-based binder for sustainable ecological buildings, avoiding the exploitation of new clay quarries. Also, it might be utilized for ecological brick production.

Ferrous particles are usually found in atmospheric particulate matters due to the cars chassis oxidation. These particles are able forming conglomerates with the other mineral particles. Thus, the investigated carwash slurry (CS) reveals a high mineralized composition dominated by Quartz, Calcite and clay minerals with significant amount of iron hydroxides. We found some unusual bigger particles of ferrous conglomerate (FC) into the CS sample. XRD and mineralogical microscopy (MOM) reveal that FC sample is formed by a nanostructured mixture of 56 wt.% Calcite and 44 wt.% Goethite. SEM images and EDS spectra reveal submicron particles within the FC structure with a dense mixture of Ca and Fe. FTIR investigation reveal strong absorption bands for goethite and very weak ones for Lepidocrocite within the FC sample. The results indicates that the conglomerate weas formed on the car chassis rust by wet partial dissolution of calcite that locally forms Ca(OH)2 which further is re-crystallized as calcite due to the CO2 from the combustion gases. Fine crystallites of iron hydroxides are embedded into the re-crystallized

This paper deals with a comprehensive study of the semi-solid metal extrusion and deposition (SSMED) process and influencing parameters. This process could be considered as a non-powder based metal Additive Manufacturing (AM) method. Unlike the common methods of metal AM, it utilizes the extrusion of a metallic filament in a semi-solid state (thixo-extrusion) to build the final product from a CAD file in a layer-wise fashion. A continuous wire thixo-extruder was designed and mounted on a 3 axis table to deposit semi-solid slurry layer by layer. This work seeks to provide a better understanding of the impact of the principle process variables on the quality of this layer-wise freeform fabrication method. The process parameters related to the production and pre-treatment of the metallic filament, its thixo-extrusion, rheological and microstructural aspects are included in this study. The results show that wire pre-treatment process variables have strong effect on the globular microstructure of metallic filament and this in turn has great role in the alloy's thixo-extrudability. Proper design of a thixo-extruder and selecting accurate values for the influencing parameters is the key to a successful production. The quality of the fabricated part was influenced by several factors such as microstructural, geometrical and run time parameters. Semi-solid alloy's solid fraction was the most influential factor in the thixo-extrusion process. Alloys with solid fraction values in the range of 0.3-0.6 could be thixo-extruded. It was found that temperature distribution and feed rate had a great effect on the process performance. Also design guidelines for selecting the appropriate thixo-extrusion properties were presented for different operating conditions.

Exploration and production as one of the most important parts of the petroleum industry encounters different problems, usually resulting in nonproductive time and additional expenses. The most common and most expensive of them are related to wellbore instability and associated problems. Wellbore instability problems are usually related to drilling operation, but they can also appear during completion, workover, or the production stage of a certain well. The traditional solution for wellbore instability problems is composed from the early recognition of specific wellbore instability problems, the main cause identification and swift response. For more effective solution it is necessary to incorporate wellbore stability and risk assessment in the early phase of well design. This chapter gives one general overview of wellbore instability problems and their causes as well as an overview of actual approaches and methods in wellbore stability and risk assessment.

When tunnelling with a TBM (Tunnel Boring Machine) in rock and soil, mostly the machine is described and often reduced to a slogan. Such descriptions say little about geotechnical processes at the tunnel face that are key to the success of tunnel driving and must be considered when selecting a tunnelling system. In soil tunnels the tunnel face must be safely supported and extracting material must be possible. For a slurry shield the slurry must not escape and pressure must act on the face. In the literature mostly bentonite content is considered. With an Earth‐Pressure balance machine the soil has to have characteristics that it can be remoulded and transformed in a mass of adequate consistency with mechanical means, adding water and additives such that this mass can support the face and be extracted. Long‐term experience shows that the fine content and polymers are also important factors. Flow channels (pores) in open gravel may be clogged, and the face supported by seepage forces....

The present investigation aims at determining the optimum quantity of saw dust that can be substituted to the secondary ceramic slurry for increasing the porosity of the destroyable investment casting ceramic shells without affecting its adequate strength. Further, both the slurry responses, namely viscosity, density, plate weight and pH, and shell responses, namely thickness, porosity, green strength and fired strength, determined from the saw dust based secondary ceramic slurry were optimized using Taguchi's methodology. The input process parameters opted for the conduct of experiments were three different weight per cent of saw dust (3%, 5% and 7%), filler-tobinder ratio (1.5:1, 1.75:1 and 2:1) and slurry stirring time (18, 24 and 48 h). The optimum amount of saw dust that can be substituted in the secondary ceramic slurry for constructing the qualitative ceramic shells was found to be 5 wt%. The best combination of filler-to-binder ratio was established to be 2:1 for most of the responses except shell porosity. The range selected for slurry stirring time was found to be the insignificant process parameter influencing both slurry and shell responses.

for vertical flows of slurries of particles with diameters between 1.37 and 3.4 mm in pipes of diameter 26 and 40 mm. By expressing the wall shear stress as the sum of fluid and particle components, the wall stresses for the particles have been evaluated. The stresses increase with particle diameter and density, mean flow velocity and particle concentration. Measurements of the velocity of the particles closest to the pipe wall suggest that considerable distortion of the velocity distribution occurs, compared to that of the clear carrier fluid. The measurements confirm that a region of reduced particle concentration forms at the pipe wall, with coarse particles giving a pronounced change of this type. The wall stresses resemble those discovered by Bagnold for particles sheared in Couette flow. In Bagnold's experiments, wall stresses were found to be strongly dependent on solids concentration. Since the particle concentration at the wall was unknown in the present investigation, a correlation for wall stresses has been obtained in terms of the mean concentration. The correlation can be used to estimate pressure gradients for vertical flows of nearly isometric angular particles.

The study deals with experiments and predictions on turbulent flow and heat exchange in a fully developed slurry flow in a vertical upward pipe. Four slurries were considered: two with glass spheres particles with diameters of 0.125 mm and 0.240 mm, respectively, and two with sand spheres particles with diameters of 0.470 mm and 0.780 mm, respectively. The volume concentration of the particles was changed in the range of 10% to 40%. This study has indirectly demonstrated the existence of turbulence suppression to a degree dependent on the diameter of the solid particles. A mathematical model for heat transfer between slurry and pipe was developed using the two-equation turbulence model and a specially designed wall function, including particle diameter and solid concentration. The model assumed a constant wall temperature and heat flux. The study’s objective was to determine the influence of the diameter of the solid particles on the heat exchange. The Nusselt number was found to ch...

The study deals with the modelling and experiments of vertical solid-liquid turbulent flow with narrowly sized solid particles of average diameters equal to 0.125 mm, 0.240 mm and 0.470 mm, and solid concentrations by volume from 10% to 40%, called medium slurry. The physical model assumes that the slurry with solid particles surrounded by water is flowing upward through a vertical pipeline with solid concentrations from 10–40% by volume. Experiments with such slurries clearly indicated enhanced damping of the turbulence, which depends on the diameter of the solid particles. The mathematical model constitutes conservative equations based on time averages for mass and momentum. The closure problem was solved by taking into account the Boussinesque hypothesis and a two-equation turbulence model together with an especially designed wall damping function. The wall damping function depends on the average diameter of the solid particles and the bulk concentration. The predictions’ results...

Slurry flows commonly appear in the transport of minerals from a mine to the processing site or from the deep ocean to the surface level. The process of heat transfer in solid–liquid flow is especially important for the long pipeline distance. The paper is focused on the numerical modelling and simulation of heat transfer in a fine dispersive slurry, which exhibits yield stress and damping of turbulence. The Bingham rheological model and the apparent viscosity concept were applied. The physical model was formulated and then the mathematical model, which constitutes conservative equations based on the time average approach for mass, momentum, and internal energy. The slurry flow in a pipeline is turbulent and fully developed hydrodynamically and thermally. The closure problem was solved by taking into account the Boussinesque hypothesis and a suitable turbulence model, which includes the influence of the yield shear stress on the wall damping function. The objective of the paper is t...

The paper deals with simulation of mass and heat transfer of Kaolin slurry with a yield stress. The yield stress is caused mainly by very fine solid particles which are of non-settling type. Slurries with the yield stress appear frequently in chemical engineering, biotechnology, medicine, power and paper plants, food and mining industries and are often strongly influenced by heat exchange between the transported materials and the surroundings. The paper is focused on heat transfer in hydro-dynamically and thermally developed turbulent pipe flow of Kaolin slurry. The slurry contains solid particles with averaged diameter about 5 m, and concentration of solid phase which varies from 0% to 40% by volume. Experiments proved that such slurries exhibit enhanced damping of turbulence, so they require especially designed wall damping function. Simulation of slurry assumes that it is a single-phase flow with increased viscosity and density, and rheological properties can be described by Bin...

The paper presents validation of a mathematical model describing the friction factor by comparing the predicted and measured results in a broad range of solid concentrations and mean particle diameters. Three different types of solids, surrounded by water as a carrier liquid, namely Canasphere, PVC, and Sand were used with solids density from 1045 to 2650 kg/m3, and in the range of solid concentrations by volume from 0.10 to 0.45. All solid particles were narrowly sized with mean particle diameters between 1.5 and 3.4 mm. It is presented that the model predicts the friction factor fairly well. The paper demonstrates that solid particle diameter plays a crucial role for the friction factor in a vertical slurry flow with coarse solid particles. The mathematical model is discussed in reference to damping of turbulence in such flows. As the friction factor is below the friction for water it is concluded that it is possible that the effect of damping of turbulence is included in the KB f...

The paper deals with the mathematical modelling of fully developed turbu-lent flow of a Bingham hydromixture in a pipe. The mathematical model is based on time averaged Navier-Stokes equations and uses the apparent viscosity concept. The problem of closure of the turbulence stress tensor was solved by the two-equation turbulence model in which a modified turbulence damping function was taken into account. The final form of the mathematical model constitutes a set of three non-linear partial differential equations. The main aim of the paper is to demonstrate a significant decrease of turbulence near the pipe wall, as the friction factor is below that for a water flow. The paper presents results of numerical simulation of the frictional head loss and friction factor for slurry flows with low, moderate, and high yield stresses. Predicted frictional head losses have been compared with experimental data showing satisfying agreement. It is demonstrated that the frictional head loss and th...

The paper deals with a solid-liquid turbulent flow with moderate and high solids concentration, which appears widely in chemical and mining industries. The slurry transported through a straight pipe contains medium solid particles of averaged diameters higher than 0.1 mm and lower than 0.8 mm surrounded by water as a carrier liquid. Mathematical model assumed that that flow is turbulent, fully developed and axially symmetrical with steady viscosity equal to carrier liquid viscosity and density depending on solids concentration. The model uses time averaged momentum equation and the problem of closure is solved by two-equation turbulence model, which includes a new turbulence damping function specially developed for such slurry flows. The mathematical model is suitable to predict slurry flow with medium solid particles and solids concentration from 10% to 40% by volume. Numerical predictions were compared with measurements showing good accuracy. Possible reason of turbulence damping ...

The paper concerns simulation of fully developed and axially-symmetrical turbulent flow of coarse-dispersive slurry if all solid particles have similar size and shape with particles diameter from 1 mm to 5 mm, solid density from 1045 kg/m 3 to 3000 kg/m 3 , and solid concentration by volume from 20% to 40%. The author examines the influence of particle diameter on additional shear stress due to the 'particles-wall' interactions for moderate and high solid concentration. The mathematical model was developed using Bagnold's concept, and assumes that the total wall shear stresses are equal to the sum of 'liquid-wall' and 'particles-wall' shear stresses. The mathematical model was successfully verified with own measurements of frictional head loss in vertical coarse -dispersive slurry flow, named: 'sand-water', 'polystyrene-water ' and 'pvc-water', [10], . The mathematical model can predict 'particles-wall' shear stress, pressure drop and friction factor for coarse-dispersive turbulent slurry flow in a pipe, . The aim of the paper is to present qualitative and quantitative dependence of solid particle diameter, solid particle density, solid concentration, and Reynolds number for carrier liquid phase on the 'particles-wall' shear stress. It is demonstrated that the solid particle diameter plays crucial role in its dependence on the 'particleswall' shear stress. It was proved that in particular flow conditions the 'particles-wall' shear stress is much higher compared to the carrier liquid wall shear stress.

Limestone slurry appears in the lime production process as the result of rinsing the processed material. It consists of particles with diameter smaller than 2 mm and the water that is a carrier of solid fraction. Slurry is directed to the settling tank, where the solid phase sediments and the excess water through the transfer system is recovered for re-circulation. Collected at the bottom of the tank sludge is deposited in a landfill located on the premises. Rheological properties of limestone slurry hinder its further free transport in the pipeline due to generated flow resistance. To improve this state of affairs, chemical treatment of drilling fluid, could be applied, of which the main task is to give the slurry properties suitable for the conditions encountered in hydrotransport. This treatment consists of applying chemical additives to slurry in sufficient quantity. Such additives are called as deflocculants or thinners or dispersants, and are chemical compounds which added to aqueous solution are intended to push away suspended particles from each other. The paper presents the results of research allowing reduction of shear stress in limestone slurry. Results demonstrate rheological properties of limestone slurry with and without the addition of modified substances which causes decrease of slurry viscosity, and as a consequence slurry shear stress for adopted shear rate. Achieving the desired effects increases the degree of dispersion of the solid phase suspended in the carrier liquid and improving its ability to smooth flow with decreased friction.

for vertical flows of slurries of particles with diameters between 1.37 and 3.4 mm in pipes of diameter 26 and 40 mm. By expressing the wall shear stress as the sum of fluid and particle components, the wall stresses for the particles have been evaluated. The stresses increase with particle diameter and density, mean flow velocity and particle concentration. Measurements of the velocity of the particles closest to the pipe wall suggest that considerable distortion of the velocity distribution occurs, compared to that of the clear carrier fluid. The measurements confirm that a region of reduced particle concentration forms at the pipe wall, with coarse particles giving a pronounced change of this type. The wall stresses resemble those discovered by Bagnold for particles sheared in Couette flow. In Bagnold's experiments, wall stresses were found to be strongly dependent on solids concentration. Since the particle concentration at the wall was unknown in the present investigation, a correlation for wall stresses has been obtained in terms of the mean concentration. The correlation can be used to estimate pressure gradients for vertical flows of nearly isometric angular particles.

The paper deals with fully developed steady turbulent flow of slurry in a circular straight and smooth pipe. The Kaolin slurry consists of very fine solid particles, so the solid particles concentration, and density, and viscosity are assumed to be constant across the pipe. The mathematical model is based on the time averaged momentum equation. The problem of closure was solved by the Launder and Sharma k-ε turbulence model (Launder and Sharma, Lett Heat Mass Transf 1:131-138, 1974) but with a different turbulence damping function. The turbulence damping function, used in the mathematical model in the present paper, is that proposed by Bartosik (1997). The mathematical model uses the apparent viscosity concept and the apparent viscosity was calculated using two-and three-parameter rheological models, namely Bingham and Herschel-Bulkley. The main aim of the paper is to compare measurements and predictions of the frictional head loss and velocity distribution, taking into account two-and three-parameter rheological models, namely Bingham and Herschel-Bulkley, if the Kaolin slurry possesses low, moderate, and high yield stress. Predictions compared with measurements show an observable advantage of the Herschel-Bulkley rheological model over the Bingham model particularly if the bulk velocity decreases.

The article deals with the transportation of lime slurry from the reservoir to a settler in a chosen industrial enterprise. The slurry is non-Newtonian and viscoplastic. Such a slurry emphasises high viscosity and is difficult to transport under a high solid concentration in a pipeline. The amount of specially designed deflocculant was developed on the basis of rheological measurements. The addition of deflocculant allowed the reduction of friction in the pipeline and, as a consequence, allowed transportation with a higher solid concentration. This resulted in a decrease in the power consumption of the pump motor and significant energy savings in the slurry transport process. The paper presents the determination of the parameters of the transition from laminar to turbulent flow of lime slurry with the addition of a certain amount of deflocculant. The purpose of the investigation was to determine the critical value of the Reynolds number in the slurry flow with a volume concentration...

The soil slurry-sequencing bath reactor (SS-SBR) was studied to treat poorly graded sand with clay (SP-SC) contaminated by aged petroleum hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) with concentrations of 23000 mg/kg and 750 mg/kg respectively. An 8 L bioreactor was operated with a 10% solid concentration (0.1 kg dry soil/L slurry). The fill period was relatively instantaneous, and the draw period lasted approximately 1 minute so the react period comprised essentially the entire cycle time. In the draw period a fraction of slurry (10%) was removed from the SS-SBR weekly and it was replaced with untreated slurry. This volumetric replacement strategy provided 70 days hydraulic retention time (HRT). The process performance was assessed by monitoring total petroleum hydrocarbons (TPH) and PAH concentrations, pH, dissolved oxygen (DO), oxygen uptake rate (OUR) and colony forming units (CFU). Due to a high concentration of TPH, silica gel clean up was performed to specify PAH degradation. The results have shown high overall removal efficiency for TPH close to 97% whereas biodegradation of PAHs has been performed with a removal efficiency of 90%.

Polythionic acids, whose general formula is H 2 S n O 6 , with n greater than 2, were discovered in the aqueous solution of SO 2 and H 2 S, known as the Wackenroder liquid. Their reactions with each other and with other reagents are, mostly, difficult to characterize, since such compounds readily decompose and interconvert, especially in solution. Nevertheless, they play an important role in technical applications (e.g., gold leaching, magnesium milling, cooling in metal processing) and in reactions of inorganic chemistry of sulfur. A few years ago, Shell-Paques/ Paqell patented the first industrial process for the biological conversion of H 2 S into a colloidal mixture of sulfur and polythionates. Such hydrophilic sulfur can be used as a fertilizer and soil improver in agriculture in all but alkaline soils. Recently, Eni S.p.A. has developed to bench plant scale a new process, the HydroClaus process for the conversion of H 2 S into an acidic hydrophilic slurry of sulfur and polythionate ions. Such a slurry can be used as a soil improver where the very alkaline soil pH hinders the cultivation. The aim of this work is to study the laboratory-scale production of polythionates in view of the novel HydroClaus process scale-up at the industrial level. After the literature related to polythionates and their characterization has been revised, the sulfur-based mixture has been synthesized and the polythionate ions concentration has been determined. Also, the effect of the reaction operating conditions has been investigated to assess how they can influence the nature and the distribution of products in solution.

Slurry-phase hydrocracking is the most suitable technology for the conversion of heavy oils/residues. However, with conventional processes, the production of low-quality by-products is unavoidable. The newly developed Eni Slurry Technology (EST) process reaches total conversion of the feedstock to distillates. A nanosized MoS 2 catalyst provides hydrogenation activity, while cracking is mainly of thermal origin. An acid catalyst alone, which would enhance the cracking reaction, is rapidly deactivated under the severe process conditions, but the presence of nanosized MoS 2 protects the acid catalyst long enough for potential practical applications, thus allowing a more effective exploitation of unconventional oil resources.

The effective detachment of ink from the fibre surface and the prevention of its redeposition onto the surface before its removal in the flotation cell is important in deinking old newsprint (ONP). Magnesium Oxide (MgO) has been found to be a suitable replacement for sodium hydroxide (NaOH) in flotation deinking in the laboratory but not as effective in mill trials. The reason for the poorer pe~formance is discussed in this paper. The use of NaOH in the deinking cell was found to produce higher IS0 brightness, due to its contribution to peroxide bleaching of the fibres, than when MgO is used as the alkali source. Traditional brightness measurements are thus a poor indication of the deinking efficiency. Measurements of R700 or ERlC are needed to better assess the effect of the different alkalis and other factors on deinking efficiency. MgO has been found to cause more redeposition of ink onto the fibres than when NaOH is used as the alkali. To overcome this, the addition of soap to the pulper when using MgO is important. The addition of silicate and calcium were found to have a detrimental effect and appear to contribute to ink redeposition. Increasing the surface area of the MgO was found to increase its hydration and also improved the deinking efficiency of the MgO. The addition of the MgO a s a hydrated slurry was also found to increase deinking efficiency. Flotation deinking, magnesium oxide, ink detachment, ink redeposition, ERlC effective residual ink concentration, ink removal efficiency Electron Scanning Microscopy shows that liquid ink foms a thin film on the surface of fibres in newsprint and that there is no morphological characteristics Research Fellow and corresponding author,

The dihydrate phosphogypsum (PG) based binder workability kinetics were investigated regarding to waterbinder ratio (W/B) and chemical admixtures added to the composition of PG paste. PG was dried at 60 °C and homogenized to powder like particles with collision milling in disintegrator and calcium sulphate hemihydrate was obtained by heating PG at 180 °C. The obtained binder chemical, mineralogical and technological properties were tested and compared to commercial gypsum plaster. Early age (2 h) and 14 d compression strength was determined. The workability and setting time of both – PG and commercial gypsum was investigated with viscosimeter, ultrasonic pulse velocity and Vicat apparatus and correlation between testing methods was obtained. Results indicate that binder based on PG has slightly lower pH (pH 6.3) than commercial binder (pH 6.8) and finer particle size grading leading to increased W/B ratio and more rapid initial setting time. The set retarder could efficiently increa...

To determine residence time distribution (RTD) in the phosphate treatment reactor we apply radiotracer method. However this method becomes effective and profitable only if the radiotracer is the suitable one. The problem to resolve in our study is "which phase of the phosphate slurry our injected radiotracer is following?". For that we add radiotracer to the phosphate slurry and we proceed to phase separation using a filtration system. We follow simultaneously -using appropriate detectors-the behavior and the quantity of the radiotracer in both phases during the separation stage. The same experiment is applied twice using successively 99m Tc and 131 I radiotracers. The comparative study proves that 131 I is more suitable than 99m Tc for solid phase labeling of phosphate slurry.

Os meus agradecimentos são dirigidos a todos os que permitiram a realização deste trabalho e que, de uma forma ou de outra, nele estiveram envolvidos, mas em especial: À minha orientadora Prof.ª Drª Elizabeth Duarte e Drª. Rita Fragoso minha coorientadora, que durante a concretização deste trabalho me ajudaram quer pelos seus conhecimentos, conselhos e orientações, quer pela disponibilidade para ouvir as minhas dúvidas e tecer palavras de incentivo. Agradeço também a ajuda na elaboração da dissertação e artigo, que proporcionaram um maior enriquecimento dos seus conteúdos, não esquecendo a preciosa ajuda no inglês. Gostaria ainda de agradecer ao meu colega e amigo Henrique, pelo apoio e companhia no laboratório, e pela boa disposição com que realizamos as muitas experiências, mesmo após um dia de trabalho. Ao Senhor Domingos, pela simpatia e pela sua grande ajuda na realização de análises físico-químicas. A todos os amigos, em especial ao meu cunhado, que estiveram presentes nesta etapa e mesmo noutras, que também eles contribuíram para o meu crescimento pessoal. À minha família em geral mas de um modo muito especial aos meus queridos pais pelo exemplo de vida, ajuda, educação e amor que sempre me têm transmitido. Ao meu pequenino Gui, que queria sempre ajudar quando me via ao computador, ou pedia colo quando eu efectuava algum cálculo, mas que me ajudou imenso pela força e alegria de viver que tem imprimido a minha vida. Por último, mas não em último, à minha Mulher Michelle, a quem muito devo a realização desta tese, pelo seu apoio permanente, expresso ou silencioso, pelas minhas más disposições e nervosismo de tantas horas e pelo carinho com que sempre as suportou. Por tudo isto, o meu muito obrigado a todos. ii Face ao aumento da população mundial tem-se vindo a verificar uma crescente necessidade alimentar, levando à intensificação da produção pecuária. A suinicultura possui elevada expressão no panorama mundial de produção animal, seguindo a tendência de intensificação e crescimento. Consequentemente verifica-se a produção de grandes quantidades de efluentes, ricos em nutrientes e matéria orgânica. Diversos tipos de processos têm sido propostos para tratar estes efluentes, nomeadamente tratamentos físico-químicos entre os quais se inclui a coagulação/floculação. Essa tecnologia de tratamento foi selecionada como objeto de estudo, onde se analisaram remoções de sólidos suspensos totais, matéria orgânica expressa em carência química de oxigénio e nutrientes, no efluente bruto de modo a simular a realidade das unidades suínicolas intensivas. No trabalho desenvolvido comparou-se a eficiência de remoção de alguns parâmetros chave através da utilização de coagulantes convencionais e um biopolímero, após otimização da dose, velocidade, tempo de agitação e volume de lamas produzidas. O biopolímero usado foi o quitosano, devido a ser abundante e natural. O coagulante convencional selecionado foi o sulfato de alumínio (Al 2 (SO 4 ) 3 ) pois foi mais eficaz do que o cloreto férrico (FeCl 3 ). Concluiu-se, comparando com o estudo de sedimentação natural, realizado em simultâneo, que o processo é eficaz, pois melhora a turvação, remove da fracção líquida o triplo de CQO, remove os metais analisados em mais de 60% e no caso do fósforo entre 70% e 94% e reduz o volume da fracção sólida resultante em cerca de 38%. Palavras chave: cloreto férrico, coagulação/floculação, efluente suinicultura, gestão de chorume, quitosano, sulfato de alumínio.

Fine-grained hematite ore can be concentrated by the process of selective flocculation and dispersion, which relies on proper reagent selection and control of water chemistry. While many previous studies have been performed analyzing the effects of different reagents on this process in a laboratory environment, this paper focuses on investigating the water chemistry within the process in a pilot-scale continuous deslime thickener. The pH, sodium concentration, calcium concentration and magnesium concentration were varied to determine their effects on the iron concentrate grade and recovery, and the phosphorus concentrate grade and rejection in the pilotscale selective deslime thickener. The ideal pH for the iron grade and recovery of the process using a starch selective flocculant was found to be 10.5. Phosphorus rejection, however, was increased at lower pH values. Minimization of sodium concentration was shown to improve iron grade, iron recovery and phosphorus rejection. Calcium acted as a nonselective flocculant showing higher iron recovery, lower iron grade and lower phosphorus rejection with increasing concentration. Conclusions could not be drawn from the experiments that varied magnesium concentration. The zeta potential of the solid-liquid interface of particles in each sample taken was also analyzed to show relationships between zeta potential and process performance. In all cases, a maximization of the magnitude of zeta potential correlated with increased iron grade and recovery. This supports the hypothesis that a higher level of dispersion enhances the selective flocculation and separation process.

Filtration of hematite ore slurries can be a bottleneck in some hematite processing plants due to inadequate filtration rates caused by the dispersion of fine particles. Flocculation of fine particles in the slurry decreases the specific cake resistance of the filter cake allowing for increased filtration rates. CO 2 sparging of hematite slurry was shown to increase the filtration rate by altering the pH and the surface chemistry of the particles. It was shown that an increase in filtration rate of 278% can be accomplished by lowering the pH from 11 to 6.5 using CO 2 at a lab scale. This was attributed to increased flocculation of hematite and silica particles in the ore.