260995 Improvements On Three Methods of Thickener Area Calculation

Thursday, November 1, 2012: 8:30 AM
403 (Convention Center )
Ahmed I.A. Salama, CanmetENERGY-Devon, Natural Resources Canada, Devon, AB, Canada

IMPROVEMENTS ON THREE METHODS OF THICKENER AREA CALCULATION

A. I. A. Salama

 

CanmetENERGY-Devon

Natural Resources Canada

Suite A202, #1 Oil Patch Drive, Devon, Alberta, Canada T9G 1A8

Phone (780) 987-8635, Fax (780) 987-8676

E-mail: Ahmed.Salama@nrcan-rncan.gc.ca   Abstract   Thickener cross-sectional Area (A) may be estimated using either one of the methods; Merta and Ziolo (MZ), Talmage and Fitch (TF), and solids sedimentation flux (SSF).  The MZ method is based on determining A's at different zone solid-concentrations.  The TF method was developed using intermediate slurry solid mass concentration (C) and thickener underflow (U), C, as a reference.  In the SSF method, two correction-factors to the solids terminal velocities are used.  

Keywords: Thickener cross-sectional, Thickener, Clarifier, Solid-liquid separation, Sedimentation solids flux

Conclusions

  The methods of MZ, TF, and SSF revisited and improvements on these methods have been proposed.  These methods are selected due to their simplicity and practicality.  The MZ method utilizes single solids settling (SS) curve.  The original TF method was developed for any intermediate slurry C and using the thickener U C as reference.  Again, the TF method uses a single settling curve.  In the TF method the reason for the overestimation of A is identified.  In the SSF method, two models of correction factors for Us(C) are proposed.  The SSF method can be applied using single SS test and an analytical model is needed to determine the settling velocity at different slurry solid mass concentrations.  In SSF and using a single settling curve a model for the settling curve is needed. However, In case of multi settling tests, the method is applied directly because the initial settling velocities at different slurry solid mass concentrations are known. Based on the results reported in this paper, general conclusions can be drawn: µ         The MZ method has been extended to show how the local maximum A can be determined. µ         In the TF method the source of A overestimation is identified. µ         The SSF method, expressions for the optimal SF's and the corresponding A's are developed. Single settling test data are used to demonstrate the MZ method and multi-settling tests data are used to demonstrate the SSF method.  In the SSF method, the RZ (Richardson and Zaki, 1954) correction factor, and Christian (1994) and Wilson and Lee (1982), correction factor for   w(C) are demonstrated.


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