- Title
- Experimental and theoretical advances for innovative bypass pneumatic conveying system design
- Creator
- Chen, Bin
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2014
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Pneumatic conveying is a popular method of transporting materials in the resource and process industries because of its advantages of no dust emission, flexible conveying pipe routes and capability to convey poisonous and hazardous material. There are two primary modes of pneumatic conveying: dilute phase and dense phase. One of the significant advantages of dense-phase conveying over dilute phase is the ability to convey materials at relatively low conveying velocities, resulting in significantly reduced particle attrition and erosive wear of pipelines. For this reason, there has been a significant move towards dense-phase systems. However, whether a material can be dense-phase conveyed in conventional pipeline is critically governed by its physical properties. Bypass pneumatic conveying systems provide the capacity to transport materials that are not naturally suited to dense-phase conveying, and can significantly reduce the minimum dense-phase conveying velocity for some materials that are dense-phase conveyed in conventional pipelines. In both cases, the conveying velocity is significantly reduced, resulting in less particle degradation, lower pipeline wear and lower power consumption. Pressure drop, specific energy consumption and minimum conveying velocity are three major parameters for assessing system performance in bypass pneumatic conveying systems. An extensive experimental program was conducted as part of this study. The pressure drop was measured when transporting fly ash, alumina, sand and plastic pellets over a range of conveying parameters in a conventional pneumatic conveying system and a series of internal bypass systems of varying configurations. The bypass configuration variations included orifice diameter, internal bypass pipe diameter and flute spacing. In particular, comparisons between the conventional system and the bypass configurations were made with respect to isothermal energy consumption and minimum conveying velocity. To interpret the mechanism of material blockage inhibition associated with bypass systems, the differential pressure between the main pipe and the internal bypass pipe was measured, together with a high-speed video camera visualisation, which provided pressure and visual information on bypass pipeline flow regimes. Based on mass and momentum conservation and the ideal gas equation, a mathematical model was developed to simulate the internal bypass pneumatic conveying process considering the internal bypass pipe configuration. In the development of the model, it was necessary to determine the solids friction factor. Although a few equations have previously been proposed to predict this factor, none was found to provide sufficient accuracy. Therefore, a solids friction factor model was developed based on the partial least squares (PLS) method. Subsequently, the proposed mathematical model, together with this modified solids friction model, was applied to predict the pressure drop within bypass systems for different conveyed materials (i.e., fly ash, alumina and sand) and different bypass configurations of varying internal bypass pipe diameter, orifice diameter and bypass flute spacing. Bypass pipe diameter and bypass flute spacing are two crucial parameters for bypass system design to avoid any possible blockage and ensure reliable conveying. In this study, a design protocol for internal bypass pipe diameter and the frequency of bypass pipeline openings was established based on the physical properties of the materials to be conveyed. This analysis was based in the theories associated with de-aeration analysis, fluidisation analysis, the Darcy Equation and orifice plate theory. This research represents a significant step in improved understanding of blockage inhibition mechanisms within a bypass system, bypass system operational principles, bypass system modelling and design protocol and the influence of material properties and bypass configurations on specific energy consumption.
- Subject
- pneumatic conveying; bypass system; pressure drop; specific energy consumption; modelling; design
- Identifier
- http://hdl.handle.net/1959.13/1047942
- Identifier
- uon:14848
- Rights
- Copyright 2014 Bin Chen
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT01 | Abstract | 235 KB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 4 MB | Adobe Acrobat PDF | View Details Download |