Flow Properties Of Bulk Solids Research Articles

Flow characteristic evaluation of iron ore for design of bunkers and chutes with different liner materials

Powders and bulk solids have to be handled and stored in all industries, ranging from powders, food, and pharmaceutical substances to raw materials such as cement, coal, and iron ore, as well as dry materials such as fly ash and moist bulk solids such as filter cake and clay. All these materials must be transported, conveyed, or otherwise handled. Thus, the characterization of powders and bulk solids in terms of flow properties is critical. The objective of this paper is to establish the flow characteristics of typical Indian iron ore for the design of test rig bunkers and chutes at different moisture levels.In this paper, the effect of moisture content on the iron ore's flow properties and its interaction with various liner materials is studied. Experimental tests were carried out for various moisture levels to determine the critical levels of moisture which adversely affecting the flow properties of bulk solids. A Jenike ring shear tester (RST) is used to find flow properties like bulk density, wall yield locus, internal friction angle, and wall friction angle of iron ore when it is interacting with different liner materials, i.e. SS 304 2B, Hardox400, Sailhard, and Chromium carbide. The results shows that 11.9% is the critical moisture level. Further, based on this, conical hopper half angle and critical opening size are evaluated for the design of mass flow bunkers and chutes.

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.

Influence of temperature on the flow properties of bulk solids

The flow behaviour of bulk solids depends upon a number of parameters. Shear tests are often used to determine the flow behaviour at room temperature. This paper aims to look at the influence of temperature on the flow behaviour of bulk solids. A newly developed ring shear test shows that the flow behaviour of some specific bulk solids depends upon the temperature.

Influence of Particle Size Distribution, Moisture Content, and Particle Shape on the Flow Properties of Bulk Solids

There has been a great deal of research on characterising bulk solids. However, some of the characteristics, particularly the time‐dependent and random changes of properties, still remain insufficiently understood. The focus of this article is to study the influence of particle size, size distribution, moisture content, and particle shape on the unconfined yield strength of bulk solids. We present some interesting results about the influence of the particle size distribution on the unconfined yield strength of a bulk solid and a new method for determining the influence of particle shape on the unconfined yield strength of a bulk solid, which was made possible by the design and use of a novel attritor.

Review on testers for measuring flow properties of bulk solids

The author was asked by the International Fine Particle Research Institue (IFPRI) to write a critical review on shear testers for IFPRI-members. The review was delivered to IFPRI in summer 1999. Following the contract with IFPRI it was not allowed to publish the review elsewhere for at least two years. Granular Matter invited the author to submit the review in the original form; during the refereeing process (besides other changes) it turned out that some remarks should be added here for clarification: - Since 1999, the author is not aware of a really new device for testing bulk solid properties, which could lead to a change of the general comments and conclusions provided in the review.

The Influence of Air Permeation on the Flow Properties of Bulk Solids

AbstractThis paper considers the influence of low air permeation on the flow properties of slightly consolidated bulk solids in steady state flow. A ring shear device was built that enables the powder sample to be permeated during the shear test from below, upwards with flow velocities below the onset of fluidization. Furthermore, a mathematical model predicting the dependence of both the shear stress as well as the location of the shear zone in the shear cell on the aeration degree was developed. This model predicts a reduction of the shear stress with increasing air feed pressure and a sudden displacement of the shear zone from the cover to the bottom of the shear cell for a high degree of aeration. The good agreement between the measured results and the model predictions proves that the influence of the permeation on the flow properties of bulk solids can be traced back to the change of the normal stresses in the shear zone.

Consolidation and flow of cohesive bulk solids

The strength and the flow properties of bulk solids can be determined by performing shear tests. A shear test always consists of two parts, consolidation and measurement of strength. The measured strength depends on the way and degree of consolidation. During consolidation a stress history is impressed on the bulk solid sample which only vanishes after steady state flow. Since the consolidation is normally done nonhydrostatically, the strength will depend on the direction of stress application (anisotropy). Thus, the strength of a bulk solid sample strongly depends on its stress history and it can show anisotropic behaviour. These effects have to be considered when comparing available shear testers.

Measurement of flow properties of bulk solids

Flowability can best be described by using the flow function as being the relationship between the unconfined yield strength and the major principal stress at steady state flow. The exact measurement of the flow function is possible only with testers, and expensive regarding time and equipment. For special applications such as quality control, simpler testers or simpler procedures may be used to get the required data.

Flow Studies on Maltodextrins as Directly Compressible Vehicles

AbstractAn evaluation of different methods of investigating the flow properties of bulk solids has been carried out on four new excipients for direct compression: Maltrin® M 150, Maltrin® M 510, Maltrin® QD M 500 and Maltrin® QD M 550.Rheological properties of the excipients like parameters from shear test, bulk density, compressibility, flow rate, dynamic angle of repose as well as mean weight and variation coefficients are reported.Although dynamic angle of repose as well as shear cell method provided similar results for the four maltodextrins under study, we observe a different behavior between the Maltrin® Ml50 and the other excipients under study in the flowmeter, being Maltrin® Ml50 the only excipient which did not flow through any orifice of the flowmeter.Therefore, our flowmeter, whose results also shows a good correlation with the coefficient of variation of the weight seems to be the most useful technique in providing a parameter which allows assessing better the difference in flowability for si...

Evaluation of an adequate method of estimating flowability according to powder characteristics

An evaluation of different methods of investigating the flow properties of bulk solids has been carried out on two new direct compression excipients, Ludipress ® and Maltrin ® M150, in order to establish a better validation of the study of the flowability of pharmaceutical powders according to their characteristics. A good correlation among all the methods was found. Also, both excipients showed different behavior, maybe due to the stickiness of Maltrin ® M150 and the size and shape of its particles. Finally, as far as an appropriate procedure is concerned, the most suitable method of estimating the flowability of powders is based on the flow rate system design, however, if it does not flow the shear cell method provides useful information about the reasons why this is so.

Effects of sudden pressure changes in the surrounding gas phase on flow properties of bulk solids

AbstractThe variation in the behaviour of bulk solids as a result of sudden pressure changes in the surrounding gas phase is of interest in the application of lock hoppers for transfer of bulk solids into pressure vessels. By using such sluice systems, problems occur due to consolidation of the pressurized bulk solids. This paper presents the results of experimental and theoretical research, which allow to describe the influence of several parameters on pressure compensation and the degree of consolidation. With reference to the forces and mechanisms responsible for consolidation, it is possible to describe the different consolidation behaviour of incompressible (limestone) and compressible (hard coal) bulk solids.

Measurement of flow properties of bulk solids

To design reliable devices for the handling of bulk solids, knowledge of the flow properties of these bulk solids is essential. For the measurement of flow properties, numerous types of shear testers are available. This paper reviews developments in the design of new shear testers. Some new results of the experimental work carried out with shear testers are presented. After a short description of the measured flow properties of bulk solids and the basic principles of shear testers, the design and/or results of some devices (Jenike shear tester, unconfined yield strength test, triaxial tester, True Biaxial Shear Tester, ring shear tester, wall friction tester) are presented. The developments and investigations reported were made with two considerations in mind. On the one hand, knowledge of the behaviour of bulk solids should be enlarged. For this goal, very specialised shear testers, e.g. the True Biaxial Shear Tester or the triaxial tester, are required. On the other hand, simpler testers have been developed to permit straightforward measurement of the flow properties used for practical applications, e.g. silo design. In addition, it is shown that the results obtained with a shear test are dependent on the kind of shear tester and the shear procedure.

Comparing the Flow Properties of Bulk Solids by Tri-axial Shear, Unconfined Yield and Direct Shear Tests [Translated]<sup>†</sup>

Comparing the Flow Properties of Bulk Solids by Tri-axial Shear, Unconfined Yield and Direct Shear Tests [Translated]<sup>†</sup>

三軸，一軸圧縮試験および直接せん断試験による粉粒体の力学物性値の比較

三軸，一軸圧縮試験および直接せん断試験による粉粒体の力学物性値の比較

An investigation into the effects of sinusoidal and random vibrations on the strength and flow properties of bulk solids

This paper is concerned with the determination of the effects of vibration frequency, amplitude and energy input on the shear strength, yield loci and flow function of bulk solids. A modified Jenike shear cell fitted with a vibration exciter is used, the equipment being designed to permit the shear strength to be measured during the application of both discrete frequency and broad band random vibrations. Studies using pyrophyllite and iron ore show that the shear strength and flow function can be reduced significantly by transverse vibrations, there being particular frequency bands over which the shear strength is minimised. Measurements of compressibility during lateral vibrations are obtained and the results are compared with the frequency versus shear data. Dynamic system identification analysis is performed to provide information on the dynamic properties of bulk materials, particularly with regard to the distribution of vibration energy as a function of frequency.

Stresses of Granular Materials in Vertical-Wall Section of Bunkers

The initial stress exerted by bulk solids in the vertical-wall section of a bunker depends on the filling rate of solids. The flow stress is independent of the discharge rate of solids, The initial stress is ordinarily smaller than the flow stress. In the range of high filling rate of solids, however, the initial stress is similar to the flow stress. As a result, the upper bound of stresses can be established only and is estimated from the Janssen equation. In this case, the ratio of the horizontal to vertical stress, k, is represented by the equation k=(1-sin2φ)/(1+sin2φ) where φ is the frictional angle between solids and the vertical bunker walls. The stress ratio is therefore smaller than unity in the vertical-wall section of the bunker. The estimated stresses agree with the present data and early data of other sources. The wall coefficient of friction is the most important of the flow properties of bulk solids.