The out-flowing behavior of particles at the discharge end of rotary kilns

Autor :Yi Chun Shi
Herkunft :OvGU Magdeburg, Fakultät für Verfahrens- und Systemtechnik
Datum :03.07.2009
Dokumente :
Dataobject from HALCoRe_document_00007209
Typ :Dissertation
Format :Text
Kurzfassung :Rotary kilns are often used in cement, metallurgy and chemical industries. The particle movement in the kiln is specially significant for the heat transfer from hot gas to the materials as well as process control. Although the particle movement inside kilns has been experimentally and theoretically studied by a lot of authors, the flowing behavior of particles at kiln discharge end is still not researched. Furthermore, this behavior is concerned by industries in the production process. The solid bed depth at the discharge end of rotary kilns was investigated for different mass flow rates, rotational speeds, inclination angles and materials using two kilns with size 0.4m(ID)*5m(L) and 0.25m(ID)*6.7m(L), respectively. The depth could be more times higher than the particle diameter in dependence on the materials. All parameters according to Saeman's model [29] were combined in a newly developed dimensionless 'Bed depth number' designated as 'Bd'. The filling degree of solid bed at the discharge can be correlated with F0=1.75*Bd0.5 (for inclination angle between 1°-4°). The range of the researched Bed depth number (Bd) is suitable for all industrial kilns. The variation of the end bed depth is also necessary for the discharge behavior in radial and axial direction. Still with the two kilns, the radial downstream velocity at the discharge end was measured with a grid box. Sand, glass beads and clinker were used as experimental materials. The particles distributions in radial direction had the best agreement with the normal distributions. The velocity is calculated according to the distribution. The end filling degree was found to influence the velocity. Based on the 'Bed depth number', the velocity equation in literature was extended, including all influencing parameters. According to the distribution, the velocity fluctuation of clinker at discharge end is the highest and glass beads is the lowest. The discharge velocity in the axial direction was also experimentally investigated. The axial discharge distribution had best fit with the normal distribution. Based on the mass balance and the results of the bed depth at discharge end, the velocities from experiments and calculation are compared. It is found that the end bed depth becomes totally active layer. The whole cross section area of the solid bed can be used to calculate the axial velocity.
Schlagwörter :Rotary kiln, Out-flowing, discharge end, filling degree, radial downstream velocity, axial velocity
Rechte :Dieses Dokument ist urheberrechtlich geschützt.
Größe :129 S.
Erstellt am :21.07.2009 - 08:17:47
Letzte Änderung :22.04.2010 - 08:09:32
MyCoRe ID :HALCoRe_document_00007209
Statische URL :http://edoc.bibliothek.uni-halle.de/servlets/DocumentServlet?id=7209