Silo Process Research Articles

Flow of asymmetric elongated particles

Shear induced orientational ordering of asymmetric elongated particles is investigated experimentally. Corn grains and pegs with one end sharpened are studied using x-ray computed tomography during quasistatic shearing and silo discharge. We show that asymmetries can be detected in the orientational distributions of the particles, which are related to the modulated rotation of the particles during shear flow. Namely, when the particles rotate in a plane that is not horizontal, they spend more time with the sharper (lighter) end pointing up, which can be explained using energetic arguments. We quantify the resulting asymmetry of the orientational distribution in a split bottom Couette cell and in a silo discharge process.

Research on the effect of the cone-in-cone insert on the discharge behaviour of conical silo

During silo unloading, the reliability of the silo can be improved by adding inserts with appropriate parameters to improve the flow pattern. In this study, DEM was used to study the influence of the cone-in-cone insert parameters on the silo discharge behaviour. The contact parameters were measured through a series of experiments, and the DEM model was established and verified. Furthermore, the silo unloading process with different insert parameter combinations was simulated, and the flow patterns were characterized by the Mass flow index (MFI). The simulation results revealed that the insert angle β and the height from the silo port H1 significantly affect the flow pattern. To realize the mass flow, H1, H2 and D2 should be reasonably selected under the β > 135°. After adding an insert with the β > 130°, the normal pressure along the silo wall was evenly distributed, and there was less wear.

A fast region homogenization method based on experimental data for pebble flow

Particle movement in pebble bed has important applications in engineering. A fast region homogenization method based on experimental silo discharging process is proposed in this paper. It can obtain the particle information from the particle motion image, and quickly calculate the homogenization information of the region. Hough transform is applied to the image of silo unloading process in order to obtain the information of particle centroid and radius. The particle tracking velocimetry (PTV) algorithm processes two continuous images to realize particle matching. Based on the trajectories of the particle, a fast region homogenization method is developed to obtain the homogenization information of the region. By analyzing the possible relative geometric relationships between mesh elements and particles, the hash set is constructed in advance to quickly calculate the regional homogenization parameters. Compared with the traditional integral method, the calculation speed is greatly accelerated on the premise of ensuring the calculation accuracy. Finally, the particle area characteristics (average velocity and filling rate) of the near wall area and the central area of the pebble bed are compared.

Continuum simulation of non-local effects in a granular silo discharge flow using a regularized μ(I) rheology model

The effect of non-local momentum transport on a silo discharge process is numerically investigated using a continuum simulation with the μ(I) rheology model in which the gradient expansion model is adopted to account for the non-local effects due to the non-uniform field of inertial number I [Bouzid et al., Phys. Rev. Lett. 111, 238301 (2013)]. The singularity for I = 0 is handled with a regularization scheme [Lin and Yang, J. Comput. Phys. 420, 109708 (2020)]. Compared to the discharge dynamics predicted with the local μ(I) rheology model, the non-local effect enhances the velocity field to increase the volume discharge flow rate Q, especially when the silo orifice L is narrower. Both the local and non-local flow simulations conform to the Beverloo relation Q=Cρg(L−kd)3/2, where d is the intrinsic grain diameter but the non-local effects appear to lessen the orifice reduction effect coefficient k. The difference between the local and the non-local flow rates ΔQ¯, made dimensionless by ρgd3/2, grew monotonically with decreasing L/d with a slight enhancement if the silo height-to-width aspect ratio deviates from unity. Finally, we evaluated the ratio of the shear strain rate to the instantaneous maximum value to define a high-shear zone when the ratio is above a threshold and studied its evolution from the onset to the end of the discharge process. Interestingly, non-local momentum transport helped to reduce the size of the high-shear zone to give a more uniformly fluidized central zone above the orifice.

Comment on Maraveas, C. Concrete Silos: Failures, Design Issues and Repair/Strengthening Methods. Appl. Sci. 2020, 10, 3938

Current silo analysis and design methods developed from Janssen’s theory focus mainly on the flow of the granules inside the silo by assuming that the overall silo structure is infinitely rigid. A silo structure during discharge is technically a time varying mass dynamic problem, where the properties of the overall silo structure and the discharge rate and material properties also contribute to the development of the load. The physics of a silo system requires equilibrium between the granules inside the silo, the silo structure as a whole and the surrounding air. The established scientific principles and experimental data require fulfilling such equilibrium to accurately predict the dynamic loads during discharge. This correspondence explains how the equilibrium between the granules inside the silo, the silo structure as a whole and the surrounding air can be achieved to better predict and control the dynamic loads generated by the silo discharge process.

Control system of the silo aeration process at the cement production

The article developed a control system for the silo aeration process. The object of control is cement silo. Cement silo is a container for storing dry cement, building mixtures or other finely dispersed materials used in the construction or production of building elements for various purposes. The task is to improve the silo control system for cement storage. Recommended ventilation times for aeration sections for commonly used cement silos are presented in terms of silo volume and the amount of material loaded. A silo aeration algorithm was compiled with alarm signals at the operator’s workstation. Four different silo operation modes were compiled to control the storage of material inside the silo: “normal emptying”, “emptying the outer ring sector”, “emptying the chambers”, “complete emptying”. A control program was developed for the cement silage aeration process in the Unity Pro XL program in FBD language.

Experimental substantiation of new criteria for silage quality evaluation

Purpose. To substantiate new criteria for evaluation of corn silage quality with bio-preservatives. Methods. Zootechnical method to determine feed digestibility in animal experiments. It is incorporated in amphorae of 1.8 tons of corn silage mass of the beginning of wax ripeness. The first amphora was without preservative, the second was with bio preservative No. 1 and the third one was with bio preservative No. 2. The silo of 3 amphorae according to the standard was evaluated. In all 3 amphorae, the silo was of good quality, but the digestibility of dry matter in the balance experiments on the rams was different. Results. The most commonly accepted criteria for evaluating silo quality are its pH value and the solids content. The high quality silo has a pH of water extract in the range of 3.6—3.9. Such pH values are created by the high content of lactic acid and low ammonia content. Under these conditions, the nutrient retention in the silage feed is the highest compared to other acidity parameters. Thus, under pH higher than 4.4 and dry matter content of 30 %, the fermentation in the silo process takes place by the proteolytic type and, as a result, butyric acid, amines and ammonia, not lactic acid, are formed. Due to the fact that butyric acid is much weaker than lactic acid and thus has a low preservative capacity, the silo is of poor quality. Therefore, high levels of ammonia, amines and butyric acid cause poor quality of the silo. High quality silo contains up to 20 % free acids (2/3 – lactic acid and 1/3 acetic acid). Our research has shown that silage packed with bio-preservatives based on lactic and propionic acid bacteria has a higher digestibility of nutrients than the same starting mass (raw material), which is ensiled without a bio-preservative. Lactic acid bacteria synthesize B vitamins (B1, B2, B5 and B7) and essential amino acids, and propionic bacteria further synthesize vitamin B12, forming mucus and giving the silage a specific, pleasant taste, providing better feed for animals, e.g. cows, substances, which is a consequence of the higher productive action of the feed. Digestibility of dry matter of silage, which was incorporated without a biological preservative, was at the rate of 53.9 %, and it was 8.8 % higher with bio-preservative No. 1. Studies conducted with an air-dry matter of 3 silos to obtain a suspension have provided the basis for evaluating bacterial preservatives for their ability to stimulate the growth of microbial protein in the silage. Conclusions. On the basis of the conducted researches new criteria for evaluation of corn silage quality were experimentally substantiated. Indicators of high-quality silage, namely, pH, total acidity, lactic, content of acetic and butyric acids and ammonia, include the digestibility of dry matter in animals, and the determination of bacterial protein as an important factor in the influence of lactic and propionic acid bacteria of bio-preservatives on the biological value of feed protein, which is a criterion for evaluating biological preservatives for the ability to stimulate bacterial protein gain in silage.

Decoupling Geometrical and Kinematic Contributions to the Silo Clogging Process.

Based on the implementation of a novel silo discharge procedure, we are able to control the grains velocities regardless of the outlet size. This allows isolating the geometrical and kinematic contributions to the clogging process. We find that, for a given outlet size, reducing the grains velocities to extremely low values leads to a clogging probability increment of almost two orders of magnitude, hence revealing the importance of particle kinematics in the silo clogging process. Then, we explore the contribution of both variables, outlet size and grains velocity, and we find that our results agree with an already known exponential expression that relates clogging probability with outlet size. We propose a modification of such expression revealing that only two parameters are necessary to fit all the data: one is related with the geometry of the problem, and the other with the grains kinematics.

A web analytics approach for appraising electronic resources in academic libraries

University libraries provide access to thousands of journals and spend millions of dollars annually on electronic resources. With several commercial entities providing these electronic resources, the result can be silo systems and processes to evaluate cost and usage of these resources, making it difficult to provide meaningful analytics. In this research, we examine a subset of journals from a large research library using a web analytics approach with the goal of developing a framework for the analysis of library subscriptions. This foundational approach is implemented by comparing the impact to the cost, titles, and usage for the subset of journals and by assessing the funding area. Overall, the results highlight the benefit of a web analytics evaluation framework for university libraries and the impact of classifying titles based on the funding area. Furthermore, they show the statistical difference in both use and cost among the various funding areas when ranked by cost, eliminating the outliers of heavily used and highly expensive journals. Future work includes refining this model for a larger scale analysis tying metrics to library organizational objectives and for the creation of an online application to automate this analysis.

3D Segmentation of Funnel Flow Boundary During Silo Emptying

Abstract The paper presents an automatic method for segmenting 3D tomography images of a funnel flow area, during silo emptying process. For generating 3D images the silo model was scanned using X-ray Computed Tomography (CT) system. The method has been applied for a chosen single slice from 3D image. The image segmentation is based on the variance of pixels calculation in defined interrogation window (or kernel). The analysis of Signalto- Noise-Ratio (SNR) of the given image allows to improve the contrast in the image and facilitate the detection the boundary between funnel area and stagnant zone. The obtained results of image segmentation show a high potential in the silo flow investigation using in-situ experiment using X-ray visualization. Additionally, the study indicates that, the separation of the silo area into the funnel and stagnant zone parts is a very challenging task especially for the top and bottom area of silo where the contrast is the smallest.

Systemic Analysis of an Industrial System: Case Study of a Grain Silo

The objective of this paper is to present firstly the issues involved in the upgrading process of industrial systems and secondly the difficulty of the transition into an automated system. Two interesting methods of analysis have been applied on an example of a grain silo process: SADT (Structured Analysis and Design Technique) and OOPP (Objective Oriented Project Planning). These methods can be applied on a systemic analysis of industrial processes. The paper briefly discusses the design of automated systems and shows some advantages of the application of systemic analysis on the upgrading of industrial systems. Afterwards, the basic principles of the two methods applied on the grain silo are presented. Finally, the different results obtained from the two methods are discussed.

Anomalous diffusion in silo drainage

The silo discharge process is studied by molecular dynamics simulations. The development of the velocity profile and the probability density function for the displacements in the horizontal and vertical axis are obtained. The PDFs obtained at the beginning of the discharge reveal non-Gaussian statistics and superdiffusive behaviors. When the stationary flow is developed, the PDFs at shorter temporal scales are non-Gaussian too. For big orifices a well-defined transition between ballistic and diffusive regime is observed. In the case of a small outlet orifice, no well-defined transition is observed. We use a nonlinear diffusion equation introduced in the framework of non-extensive thermodynamics in order to describe the movements of the grains. The solution of this equation gives a well-defined relationship (gamma = 2/(3 - q)) between the anomalous diffusion exponent gamma and the entropic parameter q introduced by the non-extensive formalism to fit the PDF of the fluctuations.

Silo Discharge: Measurement and Simulation of Dynamic Behavior in Bulk Solids

AbstractThis paper deals with the experimental investigation and the numerical simulation of silo discharge processes, including dynamic interactions between the silo filling and the elastic silo walls. The discharge process is described by a system of nonlinear differential equations. Via the Finite Element Method (FEM) based on an EULERian reference frame, the deformation rate, the velocity field, the porosity, and the stress distribution can be calculated without the need of re‐meshing the FE‐grid. To compare simulation results with measured data, the numerical simulation examples are chosen to be similar to an experimental test‐silo of the Institute of Mechanical Process Engineering at the Technical University of Braunschweig. Optical measurement techniques are applied to investigate the flow profile, and load cells on the silo walls register the stress evolution, e.g., a stress peak (switch) moving from the outlet to the transition from hopper to shaft.

Management Guidelines During Harvest and Storage of Silage

Management techniques during harvest and storage can have marked effects on the quality of forages stored as silage. Wilting to correct moistures and chopping forages to recommended particle lengths will help during the silo packing process. High cutting of corn silage may be an option for some producers to consider in the future. However, no recommendations can be made until more research is completed. Mechanical processing of corn silage can help to improve its nutritive value by improving starch and fiber digestion. Rapid packing to recommended densities and excluding air from the forage mass stimulates a more optimal fermentation in the silo. To help with the ensiling process, microbial inoculation encourages a more efficient fermentation. When forages are drier than 40% DM, inoculants are more effective if applied in a liquid form. All silage additives should be added such that they are distributed evenly throughout the forage mass. Covering bunk and pile silos with plastic is a cost efficient mechanism to save nutrients during storage. Finally, good feedout and silo face management can also help to maintain silages with a high nutritive value.

Isolation design comparisons for 0.5 μm CMOS technology using SILO process

SILO process with R.T.N. of silicon is an alternative isolation scheme, which provides both small field encroachment and rigorous isolation with 0.8 μm active area spacing. Two field doping processes were developed for 0.5 μm CMOS technology and were extensively compared.

Optimisation of isolation for 0.5 μm CMOS technology using SILO process with R.T.N. of silicon

A complete process for field isolation, applicable to a 0.5 μm CMOS technology, has been developed using SILO process with Rapid Thermal Nitridation of Silicon (R.T.N.). Adequate isolation was achieved for 0.9 μm active area spacing and n+ to p+ distance of 2.0 μm with conventional diffused twin wells. Three p+ field doping processes were compared in terms of narrow width effect and reliability.

Finite-Element Simulation of Local Oxidation of Silicon

In this paper, various numerical models for finite element simulation of local oxidation of silicon are investigated. The simplest one contains linear diffusion of oxidizing species and elastic displacements of dioxide layers. The limitations of this model and the influences of pad-oxide and nitride mask thicknesses as well as temperature are illustrated by computer simulations. The local effects of mechanical stresses on the diffusion mechanism are simulated and an elasto-visco-plastic model is proposed so that a wide range of temperatures can be covered. Finite-Element simulation of semi-Rox, full-Rox, and SILO processes are presented.