Solids Concentration Measurements of Floating Particles Suspended in a Stirred Vessel Using Sample Withdrawal Techniques

• Published in: Industrial & engineering chemistry research 1999-07, Vol.38 (7), p.2794-2802
• Main Authors: KUZMANIC, N, RUSIC, D
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical engineering; Exact sciences and technology; Mixing
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie980592i

Axial and radial concentration profiles formed during suspension of floating particles in liquid under turbulent agitation are presented in this paper. Monomodal suspensions of polyethylene in tap water stirred by a pitched blade turbine have been studied. The local solids concentration from a slurry mixing tank have been measured by the withdrawal of a sample from the vessel. The dependence of the distribution of the monosized suspension on the sample tube design and sampling technique has been investigated. Three different probes have been tested. The obtained results have to be related to the direction of the local fluid velocity at the point of sampling in the mixing tank and the orientation of the suction section of the sampling tube. The effects of the particle size, bulk solids concentration, and impeller speed on the solids concentration profiles were also examined in detail. The solids concentration profiles in the mixing tank are described by means of the one-dimensional dispersion model. The applied model includes two parameters, Pe b, modified Peclet number, based on solids upward velocity due to the buoyance force effect, and q representing the ratio of Peclet numbers for liquid and solid phases. These parameters were found to be a function of the hydrodynamic conditions in the mixing tank.