San Luis Obispo, CA, United States
San Luis Obispo, CA, United States

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Maynard E.,Jenike and Johanson Inc.
Chemical Engineering Progress | Year: 2010

Several approaches need to be employed to address pneumatic conveying problems and to significantly increase efficiency and reliability of pneumatic conveying systems. The first step in troubleshooting conveying problems is to gather data regarding pressure, temperature, feeder speed, and gas flowrate under startup and steady-state conveying conditions. The hopper is to be modified to promote a mass-flow discharge pattern, whereby all of the material is in motion during discharge, will produce a uniform discharge with a consistent bulk density. Mass flow can be achieved by changing the hopper geometry to give it a steeper angle, or by providing a smoother interior or both. The maximum flowrate in a dilute-phase line can be achieved by using the least amount of air required to achieve the minimum conveying velocities necessary to entrain the solids and prevent saltation. The leakage within a vacuum system should be corrected promptly to avoid pneumatic conveying problems.

Barnum R.,Jenike and Johanson Inc.
Glass International | Year: 2014

The article explores some of the underlying issues of furnace feed bins and suggests features that should be considered during their design. The specific characteristics of a material that affect flow, which can be measured, are known as flow properties. Requirements for achieving mass flow during bin discharge include sizing the outlet large enough to prevent an arch from forming and ensuring the converging hopper walls are steep and smooth enough to promote flow along them. The flow performance of a furnace feed bin can substantially impact its effectiveness as surge capacity and ultimately product quality.

Carson J.W.,Jenike and Johanson Inc.
Practice Periodical on Structural Design and Construction | Year: 2015

Numerous codes and standards specify means to calculate material-induced loads that are needed to design silos. The three most commonly used of such codes do not provide users with consistent information, and many common silo design conditions are not covered. A brief description of each code and its limitations is provided, and common design conditions not covered by any code are identified. © 2014 American Society of Civil Engineers.

Barnum R.,Jenike and Johanson Inc.
Glass International | Year: 2012

Roger Barnum explains how new batch handling systems can be designed to prevent problems with the use of material flow property data in a glass manufacturing factory. The flow performance of a batching and furnace feed system can have a significant effect on glass quality and plant reliability. Once mixed, the batch material is conveyed and elevated to a surge bin. In the float process, these bins tend to be short in the direction of furnace feed and wide, generally covering the full width of the furnace. Consistency of the batch material is critical for producing high quality glass. Variations can result in changes of glass density, which can lead to areas of weakness, as well as visible defects such as seeds, blisters and stones. Sifting segregation can also occur when an active flow channel forms within a bed of stagnant material. This is referred to as a funnel flow pattern, and is common in storage silos, surge hoppers and feed bins.

Pittenger B.,Jenike and Johanson Inc.
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2012

This paper describes four basic flow properties of powders and bulk solids and how these properties may be used in diagnosing flow problems in existing handling processes. Included are cohesive strength, frictional properties, permeability, and segregation tendencies. Examples of common flow problems in typical handling systems are provided as well as how a specific flow property may be the controlling factor. Using these properties, a system may be evaluated, and corrective actions developed to eliminate the flow-related problems.

Sagarnaga J.C.,Jenike and Johanson Inc.
Structures Congress 2014 - Proceedings of the 2014 Structures Congress | Year: 2014

Silo structures are used all around the world to store granular bulk solids such as grains, coal, plastic pellets, and mineral ore among many others. As bulk solids processes increase in complexity and size in industrial facilities due to plant improvements and increased global demand for products, many storage silos are designed or modified to discharge eccentrically. Even though those designs or modifications meet all the requirements at the basic and functional engineering level for the envisioned process, they may have severe implications for the storage structural system. Silo shells are efficient structures if internal pressures are applied uniformly. However, eccentric discharge changes the loading behavior to non-uniform pressures around the circumference of the silo. These non-uniform pressures cause high membrane stresses in thin metal silos which may deform the shell and, in some cases, cause catastrophic failure. In concrete silos, these non-uniform pressures result in bending moments that may cause severe damage to the walls by developing dangerous cracks. These structural damages are intimately related to the loading pattern which, in turn, is related to the bulk solids behavior developed during eccentric discharge of silos. Design of new or modified silos discharging eccentrically is a challenging task that requires not only understanding the structural analysis and design of these types of structures, but also bulk solids flow behavior as well as their loading patterns. © 2014 American Society of Civil Engineers.

Mehos G.,Jenike and Johanson Inc. | Mehos G.,Tech Forum
Chemical Engineering Progress | Year: 2011

The article describes the solids-flow property tests that should be performed and explains how to design an effective dust collector based on these properties. As dust-laden gas enters the baghouse and passes through the filter bags, particulates collect on the bags' fabric. Overtime, the buildup of dust causes the pressure drop across the fabric to rise, and the filter media must therefore be periodically cleaned, either by shaking or by applying a reverse-flow high-pressure pulse of air. The collector's outlet must therefore be equipped with an airlock to seal the hopper against the suction vacuum. A rotary valve is most commonly used for this because of its relatively low cost and simplicity. For dust collection hoppers with elongated outlets, sealing is accomplished by locating the airlock at the screw feeder discharge. The rotary valve or double flap valve must operate at a rate faster than the instantaneous rate of the screw feeder.

Maynard E.,Jenike and Johanson Inc.
Chemical Engineering Progress | Year: 2012

An overview of common segregation mechanisms is provided, key sampling techniques are highlighted, and practical guidance on preventing and solving segregation problems is offered. The forces acting on particles can strongly influence segregation potential. Vibrations and air flowing counter to the solids flow are two such forces that can radically alter a blends uniformity. If the particle properties are coupled to particle size, then blend uniformity or material consistency can be negatively affected as the vessel empties. Dusting segregation becomes prevalent when the mean particle size is around 50 μm, and is common below 10 μm. The accuracy of thief sampling results can be improved with stratified sampling and statistical analysis to differentiate between actual powder variability and errors in sampling, sample collection, or laboratory analysis.

Orlando A.D.,Jenike and Johanson Inc. | Shen H.H.,Clarkson University
Granular Matter | Year: 2013

Discrete element simulations are performed to examine the kinematics of granular shear flows in an annular shear cell at high shearing rates. The interstitial fluid is absent and gravity is included. To investigate the feasibility of using annular shear cells as rheometers for rapidly sheared dense granular materials, this study focuses on the coupled effect of boundary conditions and the relative particle to shear cell size. Four different particle diameters and three different boundary types are used in the same annular shear cell. These cases correspond to physical experiments reported earlier by the authors. For many cases both shearing and non-shearing regions coexist. The transition from partially to fully shearing flow is shown to depend on the particle diameter, solids concentration, and the boundary conditions. The particles form layers at high solids concentration and with larger particles, as evidenced by the reduction of the flow diffusivity. The slip velocity at the bottom boundary is absent; at the top it varies. This variation is sensitive to the type of boundaries but insensitive to bulk solids concentration. This study shows the interconnectivity of the boundary, the particle to shear cell size, and the flow condition in an annular shear cell. Prior to using these cells as rheometers, a thorough understanding of this interconnectivity needs to be developed. © 2013 Springer-Verlag Berlin Heidelberg.

Bharadwaj R.,Jenike and Johanson Inc.
Chemical Engineering Progress | Year: 2012

The discrete element method (DEM) is a numerical technique developed by Peter Cundall and Otto Strack to study problems in rock mechanics. It also models the behavior of individual particles to provide insight into the behavior of the bulk material. The user first creates the geometry of the system and defines the boundary motion of the moving parts within that geometry. The particles are then generated within the domain and are assigned certain grid coordinates. The simulation advances using small incremental time steps, and the total force on each particle is determined at every instant in time. Each particle's linear and angular velocities along with its displacements are calculated using a central-difference integration scheme by time. The primary limitation of DEM is its inherent computational intensity. Another major concern is the validation of the DEM model results. The most common way to validate or calibrate a model is by qualitative visualization of flow profiles or quantitative measurement of macroscopic quantities.

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