Conveying Of Solids Research Articles

Management of suspended solids accumulation on a tidally inundated stormwater canal

Low-relief coastal cities have experienced increased flooding due to climate change. During high tides or swell surges, stormwater canals or pipes can be inundated by coastal waters, causing suspended solids to accumulate at the conduits’ outfall. The Chilean city Valparaiso is currently upgrading its stormwater network with costly underground stormwater aqueducts such as the coastal Argentina stormwater canal (ASC). However, soon after the ASC was put in operation, seawater intrusion and bidirectional flow at the lowest sectors of the canal decreased its water-conveying capacity, and suspended solids that otherwise would have been carried to Valparaiso Bay accumulated in the lower sectors of the canal, close to its outfall. Urban growth and a reduction in pervious land covers could worsen the current situation. Therefore, the current ASC outfall seems to be an unsustainable solution for the conveyance of rainwater and suspended solids. In this article, a hydrodynamic model of Valparaiso Bay and the ASC is presented and the current ASC hydrodynamic regime is described. The validated hydrodynamic model was used to explore the feasibility of using a submarine outfall to transport the accumulated muddy water to an offshore location. The effects of sea-level rise on the existing stormwater canal were studied and its potential to further prevent efficient conveyance of rainwater from the city to Valparaiso Bay was explored.

Comparative Analysis of the Solid Conveying of Regrind, Virgin and Powdery Polyolefins in Single-Screw Extrusion

The shape and size of processed materials play a crucial role in the solid conveying characteristics of single-screw extruders. Thus, the increasing amount of plastic regrind leads to new challenges in screw extrusion. This work investigates the conveying behavior of three distinctly different material shapes in an axially as well as a helically grooved solid conveying zone. A uniform virgin polypropylene (PP) granule, an irregularly plate-shaped PP regrind and a powdery polyethylene (PE) are processed at screw speeds up to 1350 rpm. Thereby, frictionally engaged conveying in the grooves is visualized for the utilized powder. Similarly, the virgin granule is subject to forced conveying by interlocking in the grooves. The experimentally determined throughput is furthermore compared to analytical calculations which assume a so-called nut–screw conveying. It is found that these calculations perfectly predict the throughput when processing the virgin granule and the powder in a helically grooved barrel. In contrast, the analytical calculation significantly underestimates the throughput for the regrind. This underestimation is expected to be mainly caused by its plate shape and a difference in bulk density. The actual bulk density in the extruder is probably significantly higher due to both orientation and compaction effects compared to the measured bulk density that is used for the analytical calculation. Additionally, the regrind exhibits a fluctuating throughput due to the non-constant bulk density, which results from an irregular regrind shape and a broad size distribution.

Experimental Investigation of the Solid Conveying Behavior of Smooth and Grooved Single-Screw Extruders at High Screw Speeds.

Single-screw extrusion at high screw speeds is established nowadays since it allows for a high mass throughput at a comparatively small extruder size. Compared to conventional extrusion at low screw speeds, a considerable non-linearity in mass throughput appears by exceeding a certain threshold screw speed. In this study, the solid conveying behavior of different plastic granules with varying geometries was investigated in a smooth, a helically and an axially grooved solid conveying zone for screw speeds up to 1350 rpm. These experimental findings are compared to classical analytical predictions in the literature. It is found for the first time that both the shape and size of the plastic granules play a decisive role in determining the threshold screw speed at which a non-linear mass throughput is observed. It is shown that small and spherical granules exhibit a later onset of non-linear throughput compared to larger lenticular and cylindrical shaped granules. Moreover, it is revealed that the mass throughput equalizes for an axially and a helically grooved solid conveying zone at high screw speeds. This is contrary to the low screw speed range where the axially grooved barrel results in a significantly higher throughput than the helically grooved barrel. Thus, the maximum throughput at high screw speeds is limited by the granule stream provided by the hopper opening and is no longer governed by the groove angle.

Modeling of Solid Conveying Pressure Throughput Behavior of Single Screw Smooth Barrel Extruders under Consideration of Backpressure and High Screw Speeds

AbstractThe task of the solid conveying section is to collect the entering material and transfer it to the melt dominated sections. Therefore, its upstream interface is the hopper and its downstream interface is the section in which the first melting occurs. Beneath the hopper opening, the screw rotation collects and conveys the material forward. It is hereby assumed that the friction forces among the particles are higher than the transferring forces on the screw and barrel. For that reason commonly known models for describing the solid conveying in single screw extruders assume that the screw channel is always completely filled so that a plug flow occurs. At high screw speeds, however, these assumptions are no longer valid. To analyze and mathematically describe the solid conveying behavior at screw speeds up to 2000 rpm, simulations based on the Discrete Element Method have been executed in previous investigations. Based on this, a model for describing the solid conveying behavior was developed which enables a variation of general screw and hopper geometry parameters but neglects the backpressure that inhibits the solid movement. For that reason, further investigations based on the Discrete Element Method are presented in this paper, which enable a consideration of the backpressure and pressure build-up in the feeding zone. Astonishingly, at high screw speeds a low filling degree in the screw channel was observed which did not fulfill the expectations of an always fully filled channel due to a backpressure forced particle backlog. Based on the investigations, a mathematical model has been developed which now fully comprehends the effects occurring in the solid conveying section. The conducted simulations were subsequently validated by experimental investigations. Therefore, a test bench was designed which enables solid conveying analysis with adjustable backpressures. The results indicate a good agreement with the formulated model which now enables the calculation of solid conveying zones with consideration of the pressure build-up and filling degrees.

Short Converging Pneumatic Conveyor Used for Conveying of Solids Modelling, Analysis, and Simulation of Manufacturing Processes

Short Converging Pneumatic Conveyor Used for Conveying of Solids Modelling, Analysis, and Simulation of Manufacturing Processes

Discussion on N-Lamina Model of Non-Plug Flow Solid Conveying in Feeding Section by Single-Screw Extrusion Molding

This paper analyzed several important issues in theory of non-plug flow solid conveying, which is about the extrusion molding process of the single screw extruder, they are mainly: compressive stress on the front and rear ends of the surface, and ; an increase trend of compressive stress , ; pressure in feeding compression section of the screw, .

Numerical Simulation of Extrusion Pressure of Non-Plug Flow Solid Conveying in Feeding Section

According to the theory of extrusion pressure by molding in barrel of the single screw extruder specially designed for pure UHMWPE, extrusion pressure generated during the process must be sufficient while extrusion molding with single-screw extruder. The mathematical model for formation of extrusion pressure in feeding section during single-screw extrusion molding has been established. This paper conducted a research on theory of extrusion pressure which is part of n-lamina model of non-plug flow solid conveying in feeding section by single-screw extrusion molding.

N-Lamina Model of Extrusion Pressure of Non-Plug Flow Solid Conveying in Feeding Section by Single-Screw Extrusion Molding

While extrusion molding with single-screw extruder, extrusion pressure comes into being from feeding section; it is one of the basic conditions to ensure that extrusion process can be carried on normally, in order to ensure molding process goes smoothly, it must meet the following requirement: extrusion pressure generated during the process must be sufficient. Therefore it has certain engineering significance to design structure of a single screw correctly that a mathematical model for formation of extrusion pressure during single-screw extrusion molding will have to be established. This paper conducted a research on theory of extrusion pressure when powder of pure UHMWPE resin is still in feeding section by molding in barrel of the single screw extruder specially designed for pure UHMWPE, and established a n-lamina model of powder materials or grain materials which is in feeding section and at the state of non-plug flow solid conveying, and it provided a method to calculate extrusion pressure of the n-lamina model, thus it enriched and perfected theory of single-screw extrusion molding.

Prediction of Pressure Drop & Aerodynamic Slip Velocity in the Established Zone in the Pneumatic Conveyance of Solids in the Horizontal Conduit

An expression for the pressure drop for the established zone of pneumatic conveying system has been derived by equating the gravitational force to the resistances offered to a particle moving with terminal settling velocity. The ratio of calculated and experimental pressure drop has been defined as K, which has been correlated in terms of system variables such as particle size, density, length of the conduit and velocity of the fluid. The coefficient of correlation has been found to be 0.92 and standard error of estimates (Syx) is 0.086. It has been compared with the literature 1 data and has been found in excellent agreement. In designing the pneumatic conveying system, estimation of pressure variation along the length of the conduit is essential which is again greatly influenced by the slip velocity (us) in the line, which in a multiphase flow system is defined as the variation in the solid particle velocity (up) from the fluid velocity (uf). A correlation for us/uf has been developed. The coefficient of correlation for which has been found to be 0.9041 and the standard error of estimate (Syx) is 0.0487. The correlated and experimental values are in good agreement.

An Experimental Correlation for Friction Factor in Horizontal Pipe with Trapezoidal Section Inner Longitudinal Slots for Conveying of Solids

In order to increase the efficiency of the conveyance of the granular solids, a new experimental set-up is designed. The test rig has longitudinal trapezoidal slots in its conveying pipes. Through experimentation, a correlation for friction factor in terms of solid mass flow rate, fluid flow rate and Froude number is presented. It is shown that the mixture friction factor for pipes with inner trapezoidal slots is 40% smaller than that of pipes with inner rectangular slots. As a result, the arrangement helps to convey materials to longer distances for a given pressure setting.

Editorial: Selected Papers from 5th Int. Conf. on Conveying and Handling of Particulate Solids (Part. Part. Syst. Charact. 4-5/2007)

Particle & Particle Systems CharacterizationVolume 24, Issue 4-5 p. 251-251 Editorial Editorial: Selected Papers from 5th Int. Conf. on Conveying and Handling of Particulate Solids (Part. Part. Syst. Charact. 4-5/2007) Haim Kalman, Haim KalmanSearch for more papers by this authorAlan Roberts, Alan RobertsSearch for more papers by this author Haim Kalman, Haim KalmanSearch for more papers by this authorAlan Roberts, Alan RobertsSearch for more papers by this author First published: 20 November 2007 https://doi.org/10.1002/ppsc.200790015AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume24, Issue4-5Special Issue: Selected Papers from 5th Int. Conf. on Conveying and Handling of Particulate SolidsNovember, 2007Pages 251-251 RelatedInformation

Schüttgutumschlageinrichtung für schwer fließende Schüttgüter

Within the process- and processing technology numerous problems appear when it comes to the storage and the conveyance of bulk solids and with it connected dimensions of the conveyor technique. This paper introduces a new solution principle for the storage of bulk solids as well as its storage and removal. It concerns a turnover wheel which rotates around itself. It is rotary bedded at the superior edge of a container and depending on the fill level will be adopted automatically to the levelling. The Bulk solids envelope takes place according to the principle of “Last in – First out”. The system has been especially designed for storage in bunkers. It is arranged modular and is supposed to be applied at a diameter of four to approximately 25 meters. Possibilities of adjustment of the removal organs have been adjusted to the bulk solids and its special attributes. This enables an improvement concerning the discharge- and drive capacity. Typical flow problems of the bulk solids at the bunker and silo storage, which appear with conventional removal technology, can be avoided by the introduced principle.

Studies on the Solid Conveying Process in Micro Injection Molding Machine

Understanding the solid conveying process is important for the optimal design of micro injection molding machines. To solve problems such as starve feeding and process instability during plastication of polymers, which deteriorate product qualities, studies have been carried out on the conveying process of discrete polymer pellets. The effect of screw axis inclination on the speed of solid conveying is investigated with both simulation and experimental approaches. A discrete element modeling method (DEM) specially designed for simulating polymer particle movements in screw channels, which takes into account the effect of gravity while maintaining the simplicity of calculations, has been developed. The agreements between results of simulations and experiments verify the integrity of the models developed herein. The proposed modeling method is capable of optimizing the design of plasticizers of micro injection molding machines.

Simulation for Mixing Process in the Solid Conveying Zone of a Twin-screw Extruder

Mixing process of polymer pellets in solid conveying zone of a twin-screw extruder (TSE) is numerically investigated by using the discrete element method. It was clarified that the mixing of pellets was mainly performed in the intermeshing part of the TSE from the results of two-dimensional simulations. Moreover, a course of simulation with different conditions was performed to obtain information for improving the mixing performance. The effects of barrel property, tip-clearance, and screw-rotational speed were studied. The results suggested that the shear deformation on particle clusters at the tip-clearance is the most important factor in promoting mixing at the intermeshing part of the TSE. A preliminary result of a three-dimensional simulation with an actual geometry of conveying screws is also shown.

Special Issue on Conveying and Handling of Particulate Solids

Special Issue on Conveying and Handling of Particulate Solids

Simultaneous Simulation of Solid Conveying, Melting and Melt Flow between Parallel Plates: An Approximation to the Flow in a Screw Extruder

Instead of separate analyses of the polymeric flow in the solid conveying, melting and melt flow regions of a screw extruder, a simultaneous finite element simultation of the flow in the three zones of an extruder is presented. The flow in the helical channel of a screw extruder is approximated by a flow between two parallel plates. The effect of various processing variables, design parameters and material properties on the flow rate and the length of channel required for melting the polymer is analyzed.

Electrical Capacitance Tomography Measurements on the Pneumatic Conveying of Solids

We have evaluated the usefulness of electrical capacitance tomography (ECT) as a tool for monitoring pneumatic conveying in horizontal ducts. Power spectra of solids concentration fluctuations obtained from single-plane ECT data were used to identify the various flow regimes, and these were confirmed through visual observation. From single-plane ECT data, the instantaneous and time-averaged distributions of particle concentration over the cross section of the conveying pipe have been determined in various flow regimes. Propagation velocities of patterns were evaluated from cross correlation of twin-plane ECT data. The solids mass flow rate, determined independently by load cell measurements, was found to be roughly proportional to the product of the pattern velocity, the particle density, and the average solids holdup in the pipe, and the proportionality factor depended on the material being transported through the pipe. In our experiments involving flows past a 90° smooth bend, ECT was able to detect significant temporal and spatial nonuniformity in particle concentration in the postbend region.

Modeling and Simulation of the Solids Conveying and Unfilled Regions in Polymer Extrusion

This paper considers the important aspects of solids conveying and unfilled channels in a single screw extruder. An analytical and numerical study is carried out to obtain the compaction of powdery material as it is conveyed downstream. The associated temperature and pressure rise are also determined. The effects of operating conditions, extruder geometry and friction factors at the surface are studied. For unfilled regions, experimental data are used to obtain an expression for the filled channel length. The flow in the filled region of the extruder is simulated to obtain the pressure and temperature rise, along with other quantities. Comparisons with experimental results on both of these aspects show good agreement. The results obtained will be useful in the simulation of the entire extrusion process.

A Composite Model for Solid Conveying, Melting, Pressure and Fill Factor Profiles in Modular Co -Rotating Twin Screw Extruders

Abstract A composite model simulation of solids conveying, melting and melt flow in a modular co-rotating twin screw extruder has been developed. This is based on combining existing melt conveying models with new melting and solids conveying models for the various elements of a modular twin screw extruder. Computations are made for axial fill factor, pressure, temperature, melting profiles and also the power consumption, torque, specific energy consumption and average residence times. The results are compared with experiment.

Industrial Applications of Electrical Tomography to Solids Conveying

Industrial Applications of Electrical Tomography to Solids Conveying