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Abstract

Inline flocculation is a promising technique for the dewatering and remediation of oil sands tailings. In recent years the industry has undertaken a number of exploratory programs aimed at defining the process operating windows that will produce flocculated materials with the desired properties.

The major challenges related to the process include determining flocculant dosing sensitivities, mixer operating windows, influence of pipeline shear, and development of effective instrumentation technique and process control relationships.

To be applicable in a field setting, the inline flocculation process must be controllable such that process disturbances can be addressed, ensuring consistent production of acceptable material.

This paper presents lab-scale evaluation of a comprehensive control scheme developed by Shell for dynamic inline flocculation. A feed forward scheme is implemented to control the mixing intensity and flocculant dosage based on the properties of the fluid fine tailings and polymer.

Inline image analysis and particle size measurements performed on the flocculated product are used to add a feedback trim to the scheme, accounting for the errors in the model or unmeasured disturbances. Results from the laboratory-scale tests are presented to demonstrate the efficacy of this control strategy.