Velocity pressure drops, pneumatic conveying

Dixon (1976) has suggested using the minimum point in pressure drop with velocity for vertical pneumatic conveying in order to determine the solids friction factor and... 

To design reliably a low-velocity slug-flow pneumatic conveying system, the total pipeline pressure drop as well as the lower and upper boundaries must be predicted accurately for a given product. 

R. Pan and P.W. Wypych, Pressure Drop and Slug Velocity in Low-Velocity Slug-Flow Pneumatic Conveying of Bulk Solids, Powder Technology, 94, ppl23-132,1997. 

One widely-used picture for illustrating the different types of flow in pneumatic conveying is the so-called state diagram, - in which the pressure drop is related to the air velocity. 

In this chapter the pressure drop for pneumatic conveying pipe flow is studied. The conventional calculation method is based on the use of an additional pressure loss coefficient of the solid particles. The advantage of this classical method is that in principle it can be applied to any type of pneumatic flow. On the other hand, its great disadvantage is that the additional pressure loss coefficient is a complicated function of the density and the velocity of the conveying gas. z lso, it is difficult to illustrate the additional pressure loss coefficient and this makes the theoretical study of it troublesome. 

Mstlin. L. University of London. Ph.D. thesis (1954). A study of pneumatic conveying with special reference to solid velocity and pressure drop during transport. 

The pressure drop inside the draft tube is more complicated because it involves acceleration of solid particles from essentially zero vertical velocity. However, the model for calculating the pressure drop in vertical pneumatic conveying lines suggested by Yang (1977) can be applied. The acceleration length can be calculated from numerical integration of the following equation. 

If the conveying velocity is a critical parameter, then the designer of a pneumatic conveying system should also consider the expansion effect caused by the pressure drop along the conveying line. The resulting increase of the gas velocity can be accounted for by increasing the pipe diameter. 

R. Pan, P.W. Wypych, Pressure drop and slug velocity in low-velocity pneumatic conveying of bulk solids, Powder Technol. 94 (1997) 123-132. 

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. 

Knowlton, T. M and Bachovchin, D. M. The determination of gas-solids pressure drop and choking velocity as a function of gas density in a vertical pneumatic conveying line, International Conference on Fluidization, Pacific Grove, June 15-20, p. 253 (1975). 

Particle-fluid flow has been in existence in industrial processes since the nineteenth century. Applications include pneumatic conveying, which deals with pipe flow of solid material transported by a gas, slurry transport and processing of solids in a fluid. The necessity of predicting blower or pumping power for a given amount of material to be conveyed led to measurements of pressure drops and attempts in the correlation of physical parameters. That anomaly exists in the correlation in terms of simple parameter is one of the motivations for the exploration into the details of distributions in density and velocity and the present state of development of instrumentation. 

Stream, and the amount of solids in the reactor can only be maintained by recycling the entrained solids (circulating fluidized bed [Contractor 1999], e = 0.9-0.98). Beyond a certain fluid velocity, the system enters the realm of pneumatic conveying, in which the solid particles are carried out of the reactor without residence time, and the pressure drop increases noticeably due to acceleration of the particles. 

The pneumatic conveying system of the previous example consists on 50 m horizontal pipe, two 0.5 m radius bends, and 15 m vertical pipe. Calculate the overall pressure drop on the system if the initial air velocity is 10% over the saltation velocity. 

Pneumatic conveying is a common method for transportation of particulate solids within or between processing plants. Particles are mobilized commonly using air and transported inside pipes or ducts. To attain a consistent flow of particles, particle mobilization and fluid pressure drop should be understood in detail. Stationary particles and excessive pressure drop could halt the flow. Figure 7.35 shows a study by Kuang et al. [84] on particle-gas behavior in a horizontal pipe with a view to investigate particle porosity and velocity distribution as well as gas pressure drop. 

The typical behavior of bed pressure drop with increasing gas velocity is depicted in Fig. 4.1c and d for conventionally fluidized beds and for spouted beds, respectively. The graph for a conventional fluidized bed (Fig. 4.1c) can be subdivided into four regions, corresponding to 1, the packed bed 2, transition to bubbling fluidization 3, stable bubbling fluidization and 4, pneumatic conveying. 

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