Pneumatic conveying dense phase

Pneumatic conveying dense phase pressure pressure, batch Cycle time 1-4 min charge 10 s convey 0.5-3 min 20-50 batches/h. nominal gas velocity horizontal 4.5-35 m/s with usual 6-10 m/s vertical 1.5-27 with usual 3 m/s. Solids loading horizontal 12-130 kg/kg air vertical 10-800 with usual 250-400 kg solids/kg air. Blow tank < 15 m. Line diameter 3-10 cm. Power 3-5.5 kJ/kg. Watch for humid air and line plugging. Pressures 0.17-0.45 MPa abs. 

Pneumatic conveying dense phase No jJow or flow < design plugged line/mal-function of line boosters because of stuck check valve/high humidity. Solids fed to conveying line < design ratio of air to fluidize in the blow tank relative to convey is too small/fault in control system. 

Konrad, K. Powder Technol. 49 (1986) I. Dense-phase pneumatic conveying a review. 

Fluidized Bed Tests. These tests have direct relevance to all applications where particles are subjected to conditions of fluidization. Some authors believe that these tests can also to some extent simulate the stress of pneumatic transport. Coppingeretal. (1992) found at least a good correlation with the attrition resistance in dense-phase pneumatic conveying when they tested various powders in a slugging fluidized bed. 

Despite the little experimental data, there are two models available in the literature. Adams etal. (1992) considered dense phase conveying. They tried to predict the amount of attrition as a function of conveying distance by coupling a Monte Carlo simulation of the pneumatic conveying process with data from single-particle abrasion tests. Salman et al. (1992) focused on dilute phase conveying. They coupled a theoretical model that predicts the particle trajectory with single particle impact tests (cf. Mills, 1992). 

Figure 1. Breakdown of dense phase pneumatic conveying systems. 

Konrad, K., Dense Phase Pneumatic Conveying A Review, Powder Tech., 49 1 (1986)... 

Paul, K. D., Dense Phase Pneumatic Conveying Improving Efficiency, Powder and Bulk Engr., p. 41 (1991)... 

Mainwaring, N. J., and Reed, A. R., Permeability and Air Retention Characteristics of Bulk Solid Materials in relation to Modes of Dense-Phase Pneumatic Conveying, Bulk Solids Handling, 7(3) 415-425 (1987)... 

Keywords Fluid mechanics Hopper design Vertical pipeline Pneumatic conveying Inclined pipeline Pipeline bends Rubber hose Dense phase... 

Two typical sets of pressure measurement data for the vertically down and vertically up sections of pipeline are presented in Fig. 2. This shows the location of the pressure tappings and their proximity to the various bends in the pipeline. The data relate to the pneumatic conveying of a fine grade of pulverised fuel ash. Five different bulk particulate materials were investigated in the research programme, the other four being barytes, bentonite, cement and fluorspar. All five materials were capable of being conveyed in dense phase and hence at low velocity. 

D. Mills, J.S. Mason, P. Marjanovic, An analysis of the dense phase pneumatic conveying of cement in vertical pipelines. Proceedings of the 9th Powder and Bulk Solids Conference, Chicago, USA, May 1984, pp. 125-147. 

This paper presents mathematical and experimental studies of solids deposition characteristics in the horizontal pipeline of a dense phase slug flow pneumatic conveying... 

Blasco et al. [12] proposed two-dimensional mathematical model for the drying process of dense phase pneumatic conveying. However, heat and mass transfer were not considered and therefore their model may be used for dense phase pneumatic transport only. In their paper, both experimental and numerical predictions for axial and radial profiles for gas and solid velocity, axial profiles for solid concentration and pressure drop were presented. 

Pneumatic conveying systems can be classified on the basis of the angle of inclination of pipelines, operational modes (i.e., negative- or positive-pressure operation), and flow characteristics (i.e., dilute or dense phase transport steady or unsteady transport). A practical pneumatic conveying system is often composed of several vertical, horizontal, and inclined pipelines. Multiple flow regimes may coexist in a given operational system. 

Konrad, K., Harrison, D., Nedderman, R. M. and Davidson, J. F. (1980). Prediction of the Pressure Drop for Horizontal Dense-Phase Pneumatic Conveying of Particles. Pneumotransport, 5,225. 

The book is arranged in two parts Part I deals with basic relationships and phenomena, including particle size and properties, collision mechanics of solids, momentum transfer and charge transfer, heat and mass transfer, basic equations, and intrinsic phenomena in gas-solid flows. Part II discusses the characteristics of selected gas-solid flow systems such as gas-solid separators, hopper and standpipe flows, dense-phase fluidized beds, circulating fluidized beds, pneumatic conveying systems, and heat and mass transfer in fluidization systems. 

Plate exchangers, 189,195 Plates, fractionating. See Trays Pneumatic conveying, 71-76 dense phase transfer, 74 equipment, 72,73,75 flow rates, 72 operating conditions, 73 pilot plant, 74... 

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