Design modification of iron ore bearing transfer chute using discrete element method

Purpose The dryer feed chute of the pellet plant plays an important role in the pelletizing process. The chute discharges sticky and moist iron ore fines (<1 mm) to the inline rotary dryer for further processing. Since the inception of the installation of the dryer feed chute, the poor flowability of the feed materials has caused severe problems such as blockages and excessive wear of chute liners. This leads to high maintenance costs and reduced lifetime of the liner materials. Constant housekeeping is needed for maintaining the chute and reliable operation. The purpose of this study is to redesign the dryer feed chute to overcome the above challenges. Design/methodology/approach The discrete element method (DEM) has been used to model the flow of cohesive materials through the transfer chute. Physical experiments have been performed to understand the most severe flow conditions. A DEM material model is also developed for replicating the worst-case material condition. After identifying the key problem areas, concept designs were proposed and simulated to assess the design improvements to increase the reliability of chute operation. Findings Flow simulations correlated well with the existing flow behavior of the iron ore fines inside the chute. The location of the problematic areas has been validated with that of the previously installed chute. Subsequently, design modifications have been proposed. This includes modification of deflector plate and change in slope and cross-section of the chute. DEM simulations and analysis were conducted after incorporating these design changes. A comparison in the average velocity of particle and force on chute wall shows a significant improvement using the proposed design. Originality/value Method to calibrate DEM material model was found to provide accurate prediction and modeling of the flow behavior of bulk material through the real transfer chute. DEM provided greater insight into the performance of the chute especially modeling cohesive materials. DEM is a valuable design tool to assist chute designers troubleshoot and verify chute designs. DEM provides a greater ability to model and assess chute wear. This technique can help in achieving a scientific understanding of the flow properties of bulk solids through transfer chute, hence eliminate challenges, ensuring reliable, uninterrupted and profitable plant operation. This paper strongly advocates the use of calibrated DEM methodology in designing bulk material handling equipment.

Testing noncohesive geogrid-reinforced soil in triaxial shear apparatus under cyclic loading

In road base layers, geogrids assume the reinforcement or stabilization function where good interaction between geogrid and unbound base material is important. The cyclic triaxial test can be used for analysing interaction between geogrid and unbound base material. The paper includes an overview of research where cyclic triaxial test is primarily used for assessing the influence of parameters such as geogrid stiffness, geometry and aperture size, position and number of geogrid layers, on the interaction with the base layer material. The cyclic triaxial test can be used to determine contribution the geogrid application in non-cohesive materials has on the reduction of permanent deformations.

Long-Term Cyclic Loading Impact on the Creep Deformation Mechanism in Cohesive Materials

Long-term cyclic loading is observed in a wide range of human activities, as well as in nature, such as in the case of ocean waves. Cyclic loading can lead to ratcheting which is defined as progressive accumulation of plastic deformation in a material. Long-term cyclic loading causes a time effect (creep), which is a secondary compression effect. In this article, we conducted 15 triaxial tests on four types of cohesive materials in undrained conditions to evaluate the damage and failure mechanism. To characterize the strain and pore pressure development, we modified the Yanbu resistance concept. On the basis of the static creep tests, we concluded that the stress paths for undrained creep behavior have to take into account the pore pressure developed during long-term cyclic loading. Pore pressure build-up and plastic strain accumulation during long-term cyclic loading are dependent on the number of loading cycles. Finally, we proposed the failure criterion, which was based on the Modified Cam-Clay constitutive model.

Gels for constant and smart delivery of insulin

The focus of this review is the role of gelatinous materials for oral, transdermal and peritoneal insulin platforms as alternatives to the ubiquitous subcutaneous depot approach. Hydrogels that form hydrated, cohesive materials and the topologically complex micellar types can add ligand interaction, bond vulnerability and rheological characteristics to develop reliable programmed release, including closed loop (automated basal and bolus) activity in non-oral routes. In addition, the potential protection of the protein and likely increased paracellular uptake mean that orally active insulin is feasible. While unlikely to be suitable for closed loop delivery, the driver for gut absorption is not only to increase the convenience and decrease dosage trauma, but to target the mesentery-portal vasculature rather than peripheral tissue, thus improving hepatic glycogen equilibrium and reducing the obesogenic effect and hypoglycaemic episodes.

ANALYSIS OF STATIC ANGLE OF REPOSE WITH RESPECT TO POWDER MATERIAL PROPERTIES

This paper investigates the Angle of Repose (AoR) of powder materials with respect to their morphological and rheological properties. Glass beads, sand, flour and semolina of different particle sizes were used as the experimental materials. The investigated material was analysed with respect to particle shape and size. The rheological properties of the material were obtained by a shear cell test. The AoR was analysed in terms of cohesion, bulk density, particle size and circularity. More cohesive materials such as the flour samples exhibited the largest AoR &gt; 40°, indicating their poor flowability. Glass bead samples with a high circularity value had significantly lower AoR than the flour. The Angle of Internal Friction values were not dependent on those of the AoR. Using a dimensional analysis, a mathematical model was developed to determine the AoR values based on the material properties. By the application of this model, highly accurate calculation of the value of AoR is made possible.