Performance and capacity of centrifugal gas cleaning devices

Author

Mohamed S. Saad, University of Wollongong

Year

2006

Degree Name

Doctor of Philosophy

Department

School of Mechanical, Materials and Mechatronic Engineering - Faculty of Engineering

Recommended Citation

Saad, Mohamed S, Performance and capacity of centrifugal gas cleaning devices, PhD thesis, School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, 2006. http://ro.uow.edu.au/theses/661

Abstract

The purpose of dust control systems is to capture, collect and dispose of contaminant in an efficient manner. This research examines how to improve the operational and collection efficiency of gas cleaning devices via variations in geometry of different cyclone components. Unfortunately many of the predictive models provide inaccurate and contradictory results. Furthermore, many practical issues such as outlet and inlet configurations have not been investigated properly or at all. This study investigates the effect of cyclone outlet (vortex finder) diameter on cyclone pressure drop. Two cyclone configurations were used: air discharging directly to atmosphere; air discharging through a pipe connected to a filter. The measured values of cyclone pressure drop were compared with pressure drop predictions from various models (e.g. EEUA, 1997; Jacob et al., 1979; Rhodes, 1998; Mason et al., 1983; and Zenz, 1999). This comparison showed significant variations and differences compared with the experimental results. The models of Jacob and Dhodapkar (1979) and Mason et al. (1983) predicted similar values and were closest to the experimental data. The research evaluated existing models and developed new improved models for this purpose. A new theoretical model for pressure drop prediction across the cyclone is presented based on the consideration of the dissipative loss of flow in the cyclone system. Two different sizes of vortex finder (gas exit diameters) were used for this modeling of pressure drop. The models of Stairmand (1949), Jacob Dhodapkar (1979), Mason et al. (1983), Rhodes (1998), EEUA (1987) and Zenz (1999) predicted significantly lower pressure drops than the experimental values. The model of Barth (1956), with two values of k1 and k2 for rounded and sharp edges, respectively, predicted significantly higher values than the experimental data. Furthermore, the maximum solids flow capacity of cyclone separators was investigated. Different bulk solids and air flows were tested under different conditions: maximum solids flow rate under pneumatic conveying conditions (before choking); choked gravity flow from the test cyclone; and different gravity flow conditions from a hopper. The results obtained in this study were compared with the predictions of Beverloo et al. (1961), Brown (1961), Zenz (1962) and Johanson (1965). Results show that the Johanson (1965) model provides reasonable agreement with the experimental results.