Polymer Dose Control for Belt Presses Using Machine Vision Technology

Traditionally, it has been found to be extremely difficult to measure on-line, the effectiveness of the flocculant or polymers used on belt presses. This is due primarily to the nature of the various sludges being dewatered and fouling or clogging of the traditional types of sensors used. The subsequent lack of reliable control systems has resulted in belt press operators manually overdosing the polymer in order to ensure correct press operation throughout the changing sludge characteristics of the day. However, it is possible for a skilled operator to assess the performance of a press visually and, theoretically, he can then constantly optimize the polymer addition accordingly. This seldom happens in practice due to the ever increasing pressure on the operator's time. This paper discusses a new polymer dose control system for belt filter presses and gravity belt thickeners. The control system has been modeled on the intelligent operator principle. The dose control system uses machine vision and image analysis to provide a measurement of how well the press is performing. The measurement uses a custom designed control algorithm to optimize polymer dosage for conditioning sludge fed to the press.