Experimental studies on a Turbuflow system: a pneumatic conveying system with economical power consumption

Abstract: 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.

Abstract: Dense phase pneumatic conveying is critically dependent on the physical properties of the materials to be conveyed. However, many materials, such as alumina and coarse fly ash, which are highly abrasive, do not have dense phase conveying capacity. Bypass pneumatic conveying systems provide a dense phase capability to non-dense phase capable bulk materials. These systems also provide the capacity of lower the conveying velocity and therefore lower pipeline wear and lower power consumption occurs. The objectives of this work were to study the energy consumption and wear of bypass pneumatic transport systems. Pneumatic conveying of alumina experiments were carried out in a 79 mm diameter main pipe with a 27 mm inner diameter bypass pipe with orifice plate flute arrangement. High-speed camera visualizations were employed to present flow regimes in a horizontal pipe. The experimental result showed the conveying velocity of bypass system is much lower than that of conventional pipelines; thus, specific energy consumption in the conveying process is reduced. The service life of the bypass line has also been estimated.

Abstract: The behaviour of solids fluidized by gases falls into four clearly recognizable groups, characterized by density difference (ϱs–ϱf) and mean particle size. The most easily recognizable features of the groups are: powders in group A exhibit dense phase expansion after minimum fluidization and prior to the commenment of bubbling; those in group B bubble at the minimum fluidization velocity; those in group C are difficult to fluidize at all and those in group D can form stable spouted beds. A numerical criterion which distinguishes between groups A and B has been devised and agrees well with published data. Generalizations concerning powders within a group can be made with reasonable confidence but conclusions drawn from observations made on a powder in one group should not in general be used to predict the behaviour of a powder in another group.

Abstract: Two sizes of fine coal have been transported at room temperature at pressures up to 82.7 bar through horizontal lines 6.25, 9.19 and 12.5 mm in diameter and up to 105 m long using nitrogen, hydrogen, and carbon dioxide. Pressure differentials were established between two pressure vessels and solids and gas flow rates were measured. Solids fluxes up to 2000 kg/(m 2 ·s) were achieved at superficial gas velocities between 0.8 and 10 m/s in dense phase conveying. Separate pressure drop measurements were made over the acceleration zone and across bends, and correlations are presented for the contributions made to the total pressure drop by bends, acceleration and solids friction.

Abstract: Drying of porous materials containing binary mixtures changes the composition of the moisture to a certain extent. Generally the more volatile component is removed preferentially, especially when the drying rate is low. At sufficiently high drying rates the moisture always evaporates with constant composition; the drying is nonselective. This effect is due to the liquid-side mass transfer resistance. Nonselective drying is also obtained when the moisture has a pseudo-azeotropic composition; this depends on the relative volatility, the gas-side mass transfer and the residence time of the gas in the dryer. If such a pseudo-azeotropic composition does exist, then even the less volatile component may be removed preferentially, provided the initial composition is above the pseudo-azeotropic one. The selectivity of the drying process also depends on the size of the drying sample as well as upon whether the drying process is run continuously or intermittently. The complex interactions of phase equilibria, gas- and liquid-side mass transfer and capillary flow for given drying conditions were analyzed first for the case of evaporation of binary mixtures from a free liquid surface and second for the case of drying single porous bodies containing binary mixtures. In both cases experimental results were obtained with mixtures of isopropyl alcohol and water. They confirm the phenomena and tendencies as predicted from theoretical considerations.

Abstract: Die pneumatische Forderung bei niedrigen Gasgeschwindigkeiten ist wegen der Verstopfungsgefahr der Forderleitung normalerweise schwierig. Es wurde daher ein neues Fordersystem mit Nebenleitung entwickelt, das eine stabile Forderung einander folgender Gutpfropfen ermoglicht. Die Forderung arbeitet bei Konzentrationen von mehr als 100 kg Gut/kg Gas und bei Gasgeschwindigkeiten zwischen 2 und 12 m/s. Messungen an einzelnen Propfen und an einer Versuchsforderstrecke klaren die Vorgange bei der Forderung.

Abstract: Low-velocity dense-phase pneumatic conveying promises low power consumption with reduced attrition and abrasion. However, under certain circumstances, particles wedge together to form immovable plugs. Experimental and theoretical results on plug behaviour are briefly reviewed, illustrating means of avoiding blockage. Some existing low-velocity systems of the turbulence-generating, plug-forming and plug-destroying types are then examined. The optimum choice depends on the properties of the conveyed material. .