Deinking

July 13, 1999

Deinking Mills are a major specialty among paper recycling mills. The principal raw material categories for these mills are newsprint, magazines, telephone directories, and mixed office waste. There are many sub-specialties. For example, some mills will recycle only newsprint, while others will mix magazines with newsprint. This adds fiber strength and brightness, but it requires the addition of equipment to screen ash from the furnish. (Ash is mostly the kaolin clay coating used in glossy magazine paper.) MOW (Mixed Office Waste) mills use the least expensive material; however, it requires special equipment for removing a broad range of contaminants such as Styrofoam and stickies (contact cement).

The common feature of deinking mills is that they must separate printers' ink from the fiber. This is made difficult because the objective of ink formulators is to produce a product that stays bound to the paper fibers. Obviously there are many types of ink: water based, latex, those that work on ground wood paper, those that work for glossy coated paper, etc. One of the worst is laser printer ink, because it is heat bound to the fibers.

Once the ink and ash have been separated from the fibers, these contaminants must be screened from the flow. Traditional technology is to use a machine similar to a belt press for that purpose. The performance of these deinking machines is principally measured by (a) the brightness of the good fiber that is accepted, and (b) the amount of good fiber going in the reject steam.

Last year a Fiber Filter machine was tested for deinking capability. This was done in the laboratory of Thermo Black Clawson, the premier manufacturer of recycle paper mill machinery. The results were extremely encouraging. Compared to the conventional equipment, the Fiber Filter scored higher in brightness and, simultaneously, higher in fiber recovery. This means that more ink went through the fabric sleeve while at the same time that less good fiber was getting through the same sleeve. Ash separation was also excellent.

Feed consistencies ranging from 0.25% to 2.0% were tested. Accept consistencies were in the range of 7.5% to 14% solids, with flow rates of 150 to 250 gpm in the Model FF-12.

Issue 96