Cavitation jet deinking: a new technology for deinking of waste paper, 2008 Engineering, Pulping and Environmental Conference

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A new method and in-house device for treating secondary fiber has been developed. This method is based on the fluid-jet cavitation technique. In this apparatus, pulp suspension was injected into the reacting vessel by using a high-speed jet, and cavitation bubbles were produced around the jet. The impact of the breakage of cavitation bubbles detached contaminants, like ink and binder, from the surface of fibers. The effects of cavitating jet (hereafter called CV-jet) treatment on deinking of the pulp from mixed office waste (MOW) and old newsprints/old magazines (ONP/OMG) mixture were studied.

The basic experiments on cavitation control showed that the intensity and region of cavitation were controlled by the jet velocity and the pressure difference in the reacting vessel. It was found that the CV-jet generated broad ultrasound waves while the conventional ultrasonic apparatus generated an intrinsic frequency. The results from MOW test showed that CV-jet, even without chemicals and high temperature, decreased dirt speckles and reached almost the same dirt reduction level of the mill kneader. Moreover, CV-jet minimized fiber damages during the process and this resulted in the handsheets of the pulp giving much higher paper strength than those of kneader. The ONP/OMG test revealed that CV-jet was superior to mill disperser in terms of ink detachment and stickies dispersion. It is considered that CV-jet is a new, environmentally friendly, method in deinking and stickies treatment.