Emeritus Professor Mark Jones

Pneumatic conveying is a frequently used method of material transport particularly for in-plant transport over relatively short distances. This is primarily to exploit the degree of flexibility it offers in terms of pipeline routing as well as dust minimization. Approximately 80 % of industrial systems are traditionally dilute phase system which uses relatively large amount of air to achieve high particle velocities to stay away from trouble, such as blocking the pipeline. However, for many applications higher velocities lead to excessive levels wear of pipelines, bends, and fittings. To combat these problems, many innovative bends have been designed. These designs have solved the problem of wear in the bends, but often introduce the wear problem in the area immediately after the bend due to the changed flow conditions. Wear in pneumatic conveying is a very complex problem and at present there is limited understanding of the wear mechanisms responsible for the severe wear in certain areas of a pneumatic conveying pipeline. The ability to determine the wear mechanisms in these areas holds the key for determining the service life of pneumatic conveying pipelines in industry. Even though the fly can be conveyed at low velocity dense phase mode, wear of pipeline conveying fly ash remained a critical issue for many power plant operators. In this paper the wear mechanisms in a fly ash conveying pipeline has been analyzed. Wear samples from fly ash conveying pipeline have been collected and analyzed for dominant wear mechanisms in the critical wear areas. Analysis of the worn pipeline showed continuous wear channels along the bottom of the pipeline consistent with the abrasive wear by larger particles. The other severe wear areas are the sections after the special bends used to reduce bend wear. Scanning electron microscope (SEM) analysis of the surfaces revealed that both erosive wear and abrasive wear mechanisms are present in these areas. Formation of a surface layer similar to transfer film in alumina conveying pipelines have been recognized in this analysis. These layers seem to be removed through brittle manners such as cracking and spalling. The wear mechanisms and the wear debris seen on the surface are consistent with wear by larger particles.

A wedged plane-flow hopper and horizontal belt feeder is employed to investigate the flow patterns and stress field redistribution at the hopper and feeder interface. The flow patterns are recorded by a high speed camera in conjunction with coloured material layers. The three-dimensional stress field in the feed zone and its influence on the feeder operation are discussed. The vertical stresses acting on the feeder for initial filling and flow conditions are measured along with longitudinal shear feeder loads. The experimental results are compared with theoretical values derived using relevant feeder load theories. The influences of different filling heights and clearance between the hopper bottom and feeder surface on feeder loads are presented. Numerical simulations using the Discrete Element Method (DEM) are carried out additionally to analyse feeder loads at the hopper and feeder interface, with the results being compared with those obtained experimentally.

Within the field of pneumatic conveying horizontal (Plug-1) and vertical plug flows have been investigated only in the context of cohesive fine powders. This paper considers a series of experiments using fuzzy cottonseeds, which greatly differ in particle and bulk properties from fine powders, to investigate plug formation. In this study, several possible dense phase behaviours were observed, which were consistent in vertical and horizontal orientations and mostly influenced by the batch size of feeding into the rig due to its influence on particle arrangement. Particle arrangement at the plug base or rear was found to be critical for achieving stable plugs, with a requirement of the rear or base batch having the length of more or equal to pipe diameter. This work sheds light on the general features and mechanisms governing horizontal and vertical plug formation.

This study used a 3D coupled CFD¿DEM model to assess how slugs tend towards steady state in single slug horizontal pneumatic conveying. Initial slug length, inlet velocity and initial stationary layer fractions were systematically varied for a total of 72 simulations. Previously made observation that slugs tend towards a steady state was confirmed via a theoretical derivation. The derivation shows that slugs move towards their steady state lengths exponentially. This allowed for a calculation of a characteristic time scale which is a measure of how quickly a slug tends towards the steady state. The theoretical estimate which is a function of slug porosity, steady length, velocity and stationary layer fraction has good agreement with simulated results. A link between steady slug length and solids loading ratio was also shown.

This paper presents the results of using an inertial measurement unit (IMU) to study various dynamic relationships in horizontal slug flow pneumatic conveying. The accuracy of the IMU was assessed and compared to particle image velocimetry (PIV) and once good agreement was confirmed it was used to investigate various aspects of slug flow. Relative movement between core particles and slugs tails and heads was assessed using relative pressures and quantified times spent in a slug. It was found that the propagation of particles backwards through a slug is relatively constant. Pressure-velocity relationship was observed that was theorised to be related to variations in stationary layer ahead of the slugs. Observations of further nuanced features of slug motion are also included to demonstrate the capabilities of IMUs in capturing the many dynamic aspects of the flow.

Background: Currently, there is no single validated biomarker which can prognosticate survival in patients with stage IV non-small cell lung cancer (NSCLC). This study examines the prognostic significance of four biomarkers: neutrophil to lymphocyte ratio (NLR), lymphocyte to monocyte ratio (LMR), platelet to lymphocyte ratio (PLR) and advanced lung cancer inflammation index (ALI) in patients with stage IV NSCLC. Methods: This study aimed to establish the relationship between NLR, LMR, PLR, ALI and overall survival (OS) at baseline and post first cycle of treatment using Cox univariate PH models. We also studied these biomarkers in the elderly (age =70 years). Clinical data was sourced from Calvary Mater Newcastle between 2010 and 2015. Results: Baseline NLR, PLR, LMR and ALI showed strong association with OS. Five unit increase in NLR and PLR was associated with an 11% and 0.5% increase in the hazard of death respectively while 1 unit increase in ALI resulted in 4% increase in hazard of death. Five unit increase in LMR was associated with a 50% reduction in hazard of death. Post-treatment NLR and low ALI correlated with shorter OS but no statistically significant relationship could be demonstrated for PLR nor LMR. Similar prognostic trends were noted for elderly. Conclusions: High NLR, high PLR, low LMR and low ALI at baseline are significantly associated with poor OS. High NLR and low ALI are significantly associated with poor OS post treatment. Findings are similar regardless of age.

Background: Neoadjuvant systemic therapy (NAST) is an increasingly used treatment option for women with large operable or highly proliferative breast cancer. With equivalent survival outcomes between NAST and up-front surgery, the situation-specific preference-sensitive nature of the decision makes it suitable for a decision aid (DA). This study aimed to develop and evaluate a DA for this population. Methods: A DA booklet was developed according to international standards, including information about adjuvant and neoadjuvant treatment, outcome probabilities, and a values clarification exercise. Eligible women, considered by investigators as candidates for NAST, were enrolled in a multi-institutional, single-arm, longitudinal study. Patient-reported outcome measure questionnaires were completed pre- and post-DA, between chemotherapy and surgery, and at 12 months. Outcomes were feasibility (percentage of eligible patients accessing the DA); acceptability to patients (percentage who would recommend it to others) and clinicians (percentage who would use the DA in routine practice); and decision-related outcomes. Results: From 77 eligible women, 59 were enrolled, of whom 47 (79.7%; 95% CI, 69.4-89.9) reported having read the DA; 51 completed the first post-DA questionnaire. Of these 51, 41 participants (80.4%; 95% CI, 69.5-91.3) found the DA useful for their decision about NAST. Of 18 responding investigators, 16 (88.9%; 95% CI, 74.4-103.4) indicated they would continue to use the DA in routine practice. Post-DA, decisional conflict decreased significantly (P<.01); anxiety and distress decreased significantly; and 86.3% (95% CI, 73.7-94.3) achieved at least as much decisional control as they desired. Conclusions: This DA was feasible and acceptable to patients and clinicians, and improvement in decision-related outcomes was demonstrated when used in combination with clinical consultations. This DA could safely be implemented into routine practice for women considering NAST for operable breast cancer.

This paper presents a review of numerical models for simulation of gas-solid flow in bypass pneumatic conveying. The kinetic theory, conventional frictional-kinetic model and a new modified frictional-kinetic model are described in some detail. The experimental results for pressure drops based on a number of test cases are presented and compared with numerical results obtained with different numerical models. The convergences of the modified frictional-kinetic model with different values of constants are also illustrated. Moreover, the fluidisation charts of different materials with flow mode boundaries are presented to provide guidance on what frictional approach to use for Computational Fluid Dynamics (CFD) analysis of gas-solid flow in a bypass pneumatic conveying system. Furthermore, a flow chart for the CFD simulation methodology of bypass pneumatic conveying is demonstrated. These outcomes and the associated design guidelines could assist in choosing the most appropriate models for simulation of pneumatic conveying.

Bypass pneumatic conveying is an alternative way to convey material which does not have dense phase transport capability. The computational fluid dynamics based commercial software Fluent 6.3 is used to investigate the pressure drop as well as the gas¿solid flow behaviour in a bypass pneumatic conveying system. The conveyed material was sand with a mean particle size of 378 µm and the solid loading ratio was in the range of 10¿123. The conventional frictional-kinetic model combining frictional and kinetic stresses simultaneously was applied for pressure drop prediction. The simulation results were then compared with experimental results from bypass pneumatic conveying tests. Selected image results from the computational fluid dynamics simulations were utilised and compared with images captured from high speed camera. In addition, a test case with low air mass flow rate and high solid loading ratio 82.49 was chosen as an example to show detailed gas¿solid flow behaviour in the simulation of highly dense flows. It was found that conventional frictional-kinetic model with modified packing limit and friction packing limit has greatly improved the pressure drop prediction result compared with kinetic theory without friction. The detailed analysis for the selected test case showed how the full bore dune formation and deformation of sand and bypass flutes interact. High amplitude fluctuations and variation in pressure and gas velocity were observed. The gas velocity vectors indicate a high degree of air penetration from the flute into the bypass pipe. This behaviour provides an aeration mechanism which is what makes the bypass system work and allows non-dense phase material to be conveyed in a dense mode of flow.

A new frictional-kinetic model is proposed and modified for pressure drop prediction of alumina in a bypass pneumatic conveying system. This new model is based on the conventional Johnson-Jackson frictional-kinetic model. The critical value of solids volume fraction and maximum packing limit are modified based on the fluidized bulk density and tapped bulk density, respectively. In addition, an offset solid volume fraction is introduced into the frictional pressure model as well as into the radial distribution functions which represents the correction factors to modify the probability of collisions between particles when solid phase becomes excessively dense. For the application of the model, computational fluid dynamics (CFD) simulations were conducted by using kinetic theory, conventional frictional-kinetic model and modified frictional-kinetic model. The simulation results were then compared with the experimental results. It was found that the modified frictional-kinetic model showed the largest improvement on pressure drop prediction results compared with results obtained from applying the kinetic theory and the conventional frictional-kinetic model, especially for denser flows with low air mass flow rates and high solid loading ratios (SLR). In addition, the solids volume investigation of CFD simulations shows a strong comparison to the actual flow conditions in the pipe, as transient slug type flow of alumina is observed.

Solids friction factor is a parameter required for predicting the pressure drop in a process of pneumatic conveying. It depends upon a number of non-dimensional parameters. In this paper, experimental data for a 2. m long section of a 173. m long pipeline has been used to develop a mathematical model for solids friction factor. The model predicts the pressure drop with a low error margin for the 2. m long pipeline. Although the model has been developed for a 2. m long straight pipeline with fly ash as the conveying material, it has also been scaled-up for a 173. m long straight pipeline. By scaling-up, the predicted pressure drop lies within an acceptable error margin. Since the model seems to be having less dependence upon the parameter of particle density, it predicts the pressure drop with less error margin for the experimental data of other conveying materials such as alumina and cement. The model shows high error in predicting pressure drop for the experimental data for a different pipeline configuration.

In order to reveal the unsteady features of gas¿solid flow, the pressure fluctuations were measured at different locations along the length of the pipeline while conveying powders through the pipeline. Power spectral density (PSD) functions were obtained for the analysis of the pressure fluctuation. Two types of powders (fly ash and alumina) were used in this analysis. The PSD analysis was conducted by taking into account different aspects such as flow conditions (dilute or dense), location of transmitter (top and bottom transmitters), location of transmitter along the length of the pipeline (three different locations), material property (fly ash or alumina), etc. Analysis of signals from top and bottom transmitters shows that it is not possible to identify the flow mode at upper and lower portions of pipeline. The magnitude of power is found to be higher for alumina as compared to fly ash. PSD parametric analysis reveals that frequency bandwidth and average power decreases exponentially with increase in solid loading ratio.

Fine powders (Formula presented.)) behave analogously to liquids when aerated by air. Hence, methods (e.g. Couette method) used to determine the flow performance of liquids can be adopted to investigate the similar flow properties (e.g. apparent shear resistance) of aerated powders. By this means, the understanding and handling techniques for aerated fine powders can be significantly enhanced. This research aims to investigate the apparent shear resistance of aerated fine powders through a specialised viscometer. Such a viscometer is combined with a fluidisation system and a common rotary viscometer. Three types of fine powders (alumina, cement and flyash) were selected as testing materials. Experimental results indicated that aerated fine powders behave similarly to Herschel¿Bulkley non-Newtonian fluids. Subsequently, the apparent shear resistance for three fine powders were modelled by modifying the original Herschel¿Bulkley rheology model. Consequently, the apparent shear resistance of a specific aerated powder can be measured and modelled using the bench scale system developed in this study, thus can be utilised to predict the flow performance of fine powders in pneumatic conveyors.

Two methods were developed to investigate the porosity of moving slugs in situ during horizontal slug flow pneumatic conveying. The first method consists in applying a permeability model in combination with measurements of pressure loss and fluid velocity along the slugs. A review of existing models describing the resistance of porous structures to fluid flow revealed that the semi-empirical model of Ergun is particularly suitable to investigate the porosity profile along moving slugs. The second method consists in a direct determination method involving a slug-catcher able to catch a moving slug in a fraction of a second and simultaneously separate it into three horizontal layers. Those two methods were applied to analyse the porosity of naturally occurring slugs during pneumatic transport of polypropylene pellets. It was found that in contrast to common belief, slugs are slightly fluidised structures that do not display any porosity gradient over the pipe cross-section height. The slug porosity appeared independent of the gas conveying velocity, all slugs displaying an average porosity around 0.41, which is slightly higher than the bulk porosity of 0.38. Most of the slugs displayed a rear that is denser than the front. However, some slugs had a front that is denser than the rear while other slugs displayed a relatively constant porosity over the entire length. Those unique results refuting the commonly used hypothesis that slugs are compact structures give a new incentive to the area of slug flow pneumatic conveying. While bulk solids mechanics can no longer be applied to explain the stresses induced by moving slugs, the validity of other theories that imply that slugs are fluidised structures should be investigated. © 2013 Elsevier B.V.

This paper presents the results of experimental investigations aimed at the determination of the loads exerted on support structures buried in gravity reclaim stockpiles. Structures, such as trestle legs to support load-out conveyors in open stockpiles, or columns to support roof structures and load-out conveyors of enclosed bulk solids storage sheds are subject to the loads exerted by the surrounding bulk solids. The complexity of these loads has been discussed recently (Roberts, 2007 [1], Katterfeld and Roberts, 2009 [2]). According to the theoretical approach proposed by Roberts, both active and passive stress states in bulk solids contribute considerably to the pressure distributions on these support columns. The findings of the preliminary experimental studies carried out by Roberts match with the theoretical predictions. However, follow-up work is required to further validate and improve the design equations for the determination of the loads on support columns. Based on Roberts' prediction model, a laboratory scale test rig was constructed to measure the loads on both the front and rear faces of a buried column. Tekscan tactile pressure sensors were employed in the pressure measurements. Stockpile tests under three different conditions were investigated, and the measured results correlate well with theoretical predictions from modified Roberts' theory. The outcome confirms that Roberts' theory can contribute to the design criterion regarding the loads on buried structures in stockpiles. © 2014 Elsevier B.V.

Moving slugs of plastic pellets were investigated in-situ during low velocity pneumatic conveying in horizontal pipelines. Slug characteristics including the profile of pressure, pressure gradient, particle velocity, porosity, radial and wall shear stresses, aspect and behaviour were combined to obtain a complete picture of moving slugs. The objective was to gain unique knowledge on the physical mechanisms involved in slug formation, transport, and decay and the occurrence of pipe blockage. Slugs in both stable and unstable states were analysed. A strong correlation between particle velocity and wall stresses was found, which suggests that the stresses responsible for the high pressure loss characterising slug flow may result mostly from the transfer of particle impulses to the pipe wall. Most slugs were found to be denser at the rear where particle velocity was the highest, thus leading to slug shortening over time. This phenomenon was successfully modelled using both Newton's 2nd law and the ideal gas law and prediction of particle velocity showed good agreement with experimental values. In contrast, other slugs were found to extend due to the particles at the front moving faster than the particles at the rear. Pipe blockage was found to result from insufficient permeation of the slug by the conveying gas, indicating that sufficient material permeability is a condition for slug flow to occur. © 2014 Elsevier B.V.

Pressure drop in fluidized dense phase pneumatic conveying involves frictional interactions among gas, particle and pipe wall. There have been numerous correlations proposed by different researchers for predicting the pressure drop in fluidized dense phase conveying. In this paper steady state flow equations have been written for different phases and these equations are solved by assuming certain factors for different conveying materials. For writing the flow equations, a single gas phase and certain number of solids phases (which are chosen based on the particle size distribution of the conveying material) have been considered. Experimental data have been used as initial conditions at the exit of the pipeline in order to solve for the value of the flow parameters at the inlet of the pipeline. Experimental data have also been used to find the maximum possible conveying distance or maximum possible conveying pipeline diameter by imposing certain limiting conditions of conveying. Scaling equations for the solids mass flow rate and the air mass flow rate have been used to predict the pressure drop for different pipeline diameters and pipeline lengths. © 2012 Elsevier B.V.

Mathematical models of pneumatic conveying in dilute mode of flow have been presented by many researchers. Continuum approach is the most commonly used approach of modeling this kind of flow. In the present work a mathematical model has been developed which is in the form of governing equations such as continuity, momentum and energy equation. Energy equation has been written including a parameter called granular temperature. In this model, the dilute mode of conveying has been described as chaotically moving particles as granular gas characterized by granular temperature. Simulations have been performed in order to predict different parameters. The predicted pressure drop values were found to be in good agreement with the experimental data. Variations of important parameters such as absolute pressure, granular temperature along the length of the pipeline have been analyzed for different values of normal and restitution coefficients. © 2013 Elsevier B.V.

Pressure drop in pneumatic conveying is due to frictional interaction among gas, particle, and pipe wall. Fictional forces due to solids can be calculated using a solids friction factor. Many correlations have been proposed for predicting solids friction factor in dilute phase pneumatic conveying. These correlations are calculated based on value of the parameters calculated for a long pipeline or value of the parameter at the inlet of the pipeline. Pneumatic conveying in long pipelines suggests that some of the flow parameters are not constant along the length of the pipeline. This article presents a modeling technique for predicting solid friction factor taking into account of the local value of flow parameter. In this method, the solids friction factor is presented in terms of coefficient and exponents. The values of coefficient and exponents are predicted for fluidized dense phase conveying using different types of conveying materials. Values of coefficient and exponents are found to be different for different types of conveying materials. Variations of different parameters are studied using the calculated optimum values of coefficient and exponents. Experimental data are also used to find the possible maximum conveying distance or pipe diameter by imposing certain limiting conditions of conveying. © 2013 Copyright Taylor and Francis Group, LLC.

Two commercially available tungsten carbide-based, Ni alloy binder plasma-transferred arc-welded (PTAW) overlays, which had both previously exhibited excellent resistance to slurry erosion (in substantially non-corrosive conditions) and abrasion, were assessed in a more corrosive slurry erosion environment. One overlay consisted of a 50 vol% mixture of crushed eutectic (WC/W 2C), spherical eutectic, and tungsten monocarbide (WC) particles in a NiBSi matrix, while the other contained 50 vol% WC in a NiCrBSi matrix. Initial microstructural examination of the mixed carbide/NiBSi overlay confirmed that substantial dissolution/degradation of the spherical eutectic and crushed eutectic carbides had occurred as a consequence of interaction with its matrix alloy constituent at the high temperatures encountered during arc deposition. Conversely, the WC-based overlay exhibited very limited carbide dissolution or degradation. The total erosion-corrosion (E-C) rate, as well as its separate components, namely, erosion, corrosion, and synergy, was established using a novel slurry pot erosion-corrosion (SPEC) tester. The E-C rate for the WC/NiCrBSi overlay was approximately four times less than the E-C rate for the mixed carbide/NiBSi overlay, which performed comparatively poorly. The mixed carbide/NiBSi overlay displayed a very large synergistic value, which accounted for 90% of the total erosion-corrosion rate, with the WC/ NiCrBSi showing a synergy level accounting for 50% of the total E-C rate. To establish and compare the damage mechanisms affecting both overlays, a novel technique was implemented where specific regions were examined using scanning electron microscopy (SEM) before and after SPEC testing. This procedure was applied to identify any preferential attack that was occurring and to elucidate the reasons for the significantly different E-C performance of the two products. The main reasons for the inferior performance of the mixed carbide/ NiBSi overlay were found to be caused by the attack of the non-Cr bearing matrix and preferential removal of the W/Ni-rich boundary layer and eta-carbides, formed around the eutectic carbides during deposition. © 2012, NACE International.

WC/Ni-based plasma transfer arc welded (PTAW) overlays are frequently used in the oil sands industry for applications requiring extremely high wear resistance.These overlays usually consist of a dense distribution of either tungsten monocarbide (WC) or cast tungsten carbides (WC/W2C) in a NiBSi or NiCrBSi matrix.A previous erosion-corrosion (E-C) study of cast tungsten carbide/NiBSi-based PTAW overlays not only highlighted the expected preferential E-C attack of the non Cr-bearing matrix but also the significantly greater effect that carbide dissolution of the cast tungsten carbides had on the overall E-C performance of the overlay.It is recognised that cast tungsten carbide particles are more susceptible to dissolution during deposition than WC. As a result, a new process that modifies the outer periphery of cast tungsten carbides by producing a tungsten monocarbide shell has been developed. Overlays consisting of these carbides in a NiBSi binder were subsequently produced with the aim of reducing the extent of dissolution during deposition.The aims of this study were (i) to assess the effectiveness of the tungsten monocarbide outer shell of cast tungsten carbides to resist dissolution during the PTAW deposition process; and (ii) to highlight any improvements in the E-C properties using a novel slurry pot erosion corrosion (SPEC) tester, which incorporates a three-electrode cell to enable the separate components of erosion, corrosion and synergy, to be established. Results were compared with a commercially available NiBSi PTAW overlay containing unmodified cast tungsten carbides. © 2011.

The erosion-corrosion properties of a range of ferrous-based materials that are currently being used or have potential for use in the resources industry have been assessed using a slurry pot erosion-corrosion (SPEC) test rig that has the capability of establishing the separate components of erosion, corrosion and synergy. Testing was performed, at 30 °C, in an aqueous slurry containing 35 wt% AFS 50-70 silica sand and a 3.5 wt% NaCl solution. Erosive action was supplied through high-speed rotation of a rubber-lined impeller. Erosion-corrosion performance of materials evaluated was related to composition/microstructure and hardness. Test data correlated with available service experience. The results showed that the cast Cr white irons with (i) a structure that was essentially a duplex stainless steel containing a distribution of hard carbides and (ii) a near eutectic Cr white iron exhibited the highest erosion-corrosion resistance of the materials tested. The evaluation of the Cr white irons also highlighted the influence of Cr and C levels on the E-C properties of these materials. E-C assessment of selected carbon steels confirmed that the erosion-only rates and synergistic levels showed a general decline with increasing carbon content and hardness. As expected, a low C steel pipe product displayed very mediocre erosion-corrosion behaviour as a consequence of its very low intrinsic corrosion resistance and inferior wear properties. This reflected service experience, however, such products are still being used, due to the comparatively low initial cost. A TiC particle-reinforced AISI 316 stainless steel exhibited an almost 45% improvement in the E-C resistance, when compared with an AISI 316L stainless steel. Crown Copyright © 2009.

Pneumatic conveying characteristics for 4 different materials such as fly ash, sand, cement and crushed bath have been established by testing in a low pressure pneumatic conveying test rig at Regional Research Laboratory, Bhubaneswar. The test rig consists of a low pressure (1 barg) roots blower (140 cfm (4 m3/min), 10 HP), 1.5 m3 top discharge blow tank, 54 m long, 53 mm ID, pipeline with 7 bends and a hopper. From the conveying characteristics it has been shown that fly ash (150 µm), sand (175 µm), cement and crushed bath (3 mm) can be conveyed successfully with maximum mass product flow rate of 4.2 t/h, 1.8 t/h, 4.1 t/h and 1.5 t/h at phase density of 25, 20, 30 and 9 and at air mass flow rates of 0.047 kg/s, 0.033 kg/s, 0.038 kg/s and 0.045 kg/s, respectively, at 1.0 bar conveying line pressure drop except crushed bath which is of the order of 0.7 bar conveying line pressure drop with ambient air temperature of 25 °C. With the minimum conveying air velocity of 16 m/s, 6.5 m/s, 6.5 m/s and 16 m/s for fly ash, sand, cement and crushed bath the mass product flow rate from conveying characteristics are found to be 2.8 t/h, 0.6 t/h, 1.3 t/h and 1 t/h at phase density of 20, 10, 20 and 7 with conveying line pressure drop of 0.6 bar, 0.4 bar, 0.5 bar and 0.5 bar respectively.

The two most common methods of blending industrial coals is either by use of feeder belts discharging onto a central conveyor belt, or by a compartment hopper discharging onto a common belt. These two methodologies are shown to give very similar levels of variance in the proportioning of component coals, over a wide range of discharge conditions. Very high levels of segregation can be expected in almost any heap formed when coal material is discharged from the belt in either of the two blending method.

Air-gravity conveyors, commonly referred to as air-slides, are widely used in industry to convey bulk materials with the advantages of low particle velocities, low levels of particle attrition, potentially very high conveying rates and low power consumption. Most current designs are based on empirical design charts and past experience as there have been relatively few investigations attempting to model the flow of aerated powders on air-gravity conveyor systems. In this paper, ANSYS FLUENT has been used to simulate the air-gravity flow, where a steady, three-dimensional fluidized granular flow is considered in a rectangular channel having frictional side walls for different flow conditions. The results of simulated bed heights along the air-gravity channel are discussed. Moreover, this paper reports on work which attempts to develop a fundamental conveying model for air-gravity conveyor flows in inclined channels with an emphasis on the conservation of momentum taking into account the rheology of the gas-solid mixture. The conveying model shows the relationship between mass flow rate and bed height. The developed model well predicts the steady flow bed heights for each mass flow rate. A sensitivity analysis has been carried out which demonstrates that the conveying model can be applied to powders in a fluidized state to predict the bed heights of the flow under inclination angles between 1° to 10°.

The stationary layer of material between slugs in horizontal slug flow pneumatic conveying is an important reflection on the state and dynamics of a system. The gas-liquid analogy model of Konrad has been shown to accurately predict the layer fraction for a range of cases but the model breaks down near blockage conditions and does not consider material properties. A new model based on the rate of change of the layer fraction with respect to slug velocity was developed that accounts for material properties and is applicable at blockage conditions. Results from tests on polypropylene pellets were compared to the new model and the model of Konrad with both models satisfactorily predicting the layer fraction in the range of slug velocities that were observed for the material. At the higher extremity of slug velocity the new model predicted an earlier onset of a change in flow types than the model of Konrad which was supported by experimental observations but not enough data was obtained on the test material to compare predictions near blockage conditions. A material dependent constant in the new model was found for polypropylene pellets with further investigations needed to explore this constant as a predictive or classifying tool for materials and their ability to slug.

Erosion is observed in many industrial situations such as pneumatic conveying pipelines, shot peening and sand blasting where interaction between particle and surface is expected. A number of particle impact parameters and material surface properties are involved in the erosion process. Extensive studies have been conducted to understand the effects of the process parameters on erosion; however, only limited studies can be found in the literature associated with material surface and subsurface properties. In order to get a better understanding of the material surface and subsurface behaviour due to particle impacts for different parameters, erosion tests were performed for different impact angles and different particle velocities using a micro-sandblaster. Angular silicon carbide (SiC) particles were impacted on two different ductile surfaces, mild steel and aluminium, with a constant particle flux. Wear mechanisms were studied in terms of particle kinetic energy. Subsequently, the worn surfaces and their cross-sections were observed using scanning electron microscope (SEM) to relate the subsurface damage characteristics to different impact conditions, and to wear mechanisms. Results showed that at a lower impact angle, material was removed through cutting mechanism, while at a higher angle; material removed through predominantly deformation process. Also, subsurface cracking and subsurface damage were observed up to a certain depth from the worn surface. It appears both the depth of subsurface cracking and subsurface damages increases with increasing impact velocity. The variation is consistent with increase in surface and subsurface temperature at higher velocities. With increased temperature, the depth of the heat affected zone increases, which increases the work hardening layer thickness. In addition, subsurface microstructural damage is consistent with attainment of higher temperature which can be explained through the high strain-rate deformation and thermo-physical properties of the surface.

Bypass pneumatic conveying systems provide the capacity of transporting some materials that are not naturally suited to dense phase flow in a low velocity, dense phase flow regime. Bypass pneumatic conveying systems also provide a passive capability to reduce minimum particulate transport velocities. Therefore, particle degradation and pipe line wear can be much reduced. In this paper, the operation of internal bypass system was investigated by both experiments and modelling. An entire bypass system was numerically modelled based on the mass conservation. An integrated version of the Ideal Gas Equation was applied to evaluate pressures at the central point of each node for air flow in the bypass pipe and the main pipe. The bypass pneumatic experimental system was built with a main pipe of 79mm in diameter and an internal bypass pipe with orifice plate flute arrangement. Fly ash and alumina were used in the tests. High speed video camera visualization and differential pressure transmitters were employed to investigate the operation of dense phase bypass pneumatic transport systems and the mechanism of material blockage inhibition provided by this system. The bypass system was found to consume more energy than conventional system when using the same air mass flow rate due to the increase of friction. The conveying velocity of alumina in bypass system was much lower than that of conventional pipelines, which resulted in much reduced specific energy consumption. In this system, particulate material blockages were inhibited in bypass systems due to the air penetration into the particulate volume, as was reflected in differential pressure transmitter measurement data and flow visualization.

Two commercially available tungsten carbide-based, Ni alloy binder PTAW overlays which had both previously exhibited excellent resistance to slurry erosion (in substantially non-corrosive conditions) and abrasion were assessed in a more corrosive wear slurry environment. One overlay consisted of a 50 vol.% mixture of crushed eutectic (WC/W2C), spherical eutectic and macrocrystalline WC particles in a NiBFeSi matrix, whilst the other contained 50 vol.% macrocrystalline WC in a NiCrBSi matrix. Initial microstructural examination of the mixed carbide/NiBSi overlay, confirmed that substantial dissolution/ degradation of the spherical eutectic and crushed eutectic carbides had occurred as a consequence of interaction with its matrix alloy constituent at the high temperatures encountered during arc deposition. Conversely, the macrocrystalline WC-based overlay exhibited very limited carbide dissolution or degradation. The total erosion-corrosion (E-C) rate, as well as the separate components of erosion, corrosion and synergy, was established using a novel Slurry Pot Erosion Corrosion (SPEC) tester. The E-C rate for the macro WC/NiCrBSi overlay was approximately four times less than the E-C rate for the mixed carbide/NiBSi overlay, which performed comparatively poorly. The mixed carbide/NiBSi overlay displayed a very large synergistic value, which accounted for 90% of the total erosion-corrosion (E-C) rate, with the macro WC/NiCrBSi showing a synergy level accounting for 50% of the total E-C rate. To establish and compare the damage mechanisms affecting both overlays, a novel technique was implemented where specific regions were examined using a Scanning Electron Microscope (SEM) before and after SPEC testing. This procedure was applied to determine any preferential attack that was occurring and to elucidate the reasons for the significantly different E-C performance of the two products. The main reasons for the inferior performance of the mixed carbide/NiBSi overlay were found to be due to attack of the non-Cr bearing matrix and preferential removal of the W/Ni-rich boundary layer and eta-carbides, formed around the eutectic carbides during deposition.

Two approaches are being utilized to assess a range of materials for service in erosion-corrosion (E-C) conditions that occur during processing and transportation of aqueous slurries in oil sands operation. These are (1) using a custom-built slurry pot erosion-corrosion (SPEC) evaluation system and (2) compiling E-C maps using data from separate slurry erosion and static corrosion tests. Using slurries containing 3.5wt% NaCl so ution and 20wt% silica sand, the SPEC system confirmed that bi-metallic high Cr steel pipe product and WC/Stellite 21 PTAW overlay have provided the highest erosion-corrosion resistance of materials tested to date. The E-C maps confirmed that Stellite Co-based alloys exhibited the superior corrosion resistance whilst WC-based overlays produced the best erosion resistance of the material classes evaluated. Despite having certain limitations, both approaches provide satisfactory means of assessing materials in erosion-corrosion environments. Test conditions for both systems can be tailored to simulate particular industrial operations.

Two approaches are being utilized to assess a range of materials for service in erosion-corrosion (E-C) conditions that occur during processing and transportation of aqueous slurries in oil sands operation. These are (1) using a custom-built slurry pot erosion-corrosion (SPEC) evaluation system and (2) compiling E-C maps using data from separate slurry erosion and static corrosion tests. Using slurries containing 3.5wt% NaCl so ution and 20wt% silica sand, the SPEC system confirmed that bi-metallic high Cr steel pipe product and WC/Stellite 21 PTAW overlay have provided the highest erosion-corrosion resistance of materials tested to date. The E-C maps confirmed that Stellite Co-based alloys exhibited the superior corrosion resistance whilst WC-based overlays produced the best erosion resistance of the material classes evaluated. Despite having certain limitations, both approaches provide satisfactory means of assessing materials in erosion-corrosion environments. Test conditions for both systems can be tailored to simulate particular industrial operations.