| The degree of waste paper recycling has been increasing steadily in North America over the last decade. Today, it is recognized that the flotation deinking process is one of the most important processes in waste paper recycling. This is demonstrated by the numerous variety of industrial flotation cell technologies currently available. Column flotation, developed in the mineral processing industry, is proposed as an alternative to other flotation technologies due to its low capital costs and improved separation performance. The flotation column requires an air sparging device to produce bubbles. Previous experimentation has shown that columns run with internal porous spargers initially produced excellent ink recoveries and low organic losses but eventually the sparging system plugged and performance deteriorated.;In this work, an air sparging technique, based on a static inline pipe mixer was compared to a porous sparger. Both air sparging systems were evaluated in-plant on a lab scale flotation column to determine their relative merits, confirm previous work and compare to a circuit of full scale deinking cells. The effects of gas rate, retention time, wash water rate, froth height were investigated. It was found that the static mixer sparger was an excellent alternative to conventional porous spargers due to its stable operation and ability to control bubble size. As with porous spargers, the bubble surface area rate produced by the sparging system was found to be an important parameter in determining ink recovery. Two flotation circuits based on columns with the two competing sparging systems were scaled up using long term test data and compared. Operational boundaries for the static mixer sparger system were also defined. |
