TCF Bleaching of Mixed Office Waste Compositions, 1995 Recycling Symposium Proceedings

Patrick E. Sharpe

Kamyr, Inc. R&D Laboratory

The main objective of tbis study was to gain further understanding of the bleaching requirements for mixed office waste (MOW). Mill trials were run at a recycled fiber mill using MOW as the furnish. Samples of the mill pulp were taken at a press prior to bleaching. Additional MOW compositions were made in the laboratory, consisting of varying percentages of white fiber, colored fiber, groundwood fiber, and brown fiber. The maximum amounts of colored, mechanical and brown fibers in each composition were 40 % , 20 %, and 5 %, respectively.

Samples were deinked and bleached in the laboratory using various total chlorine-free (TCF) bleaching sequences. The dye removal index was calculated.

The final bleached brightness was found to be inversely proportional to the initial kappa number of the MOW composition. OZPF produced bleached brightnesses greater than 80% IS0 when initial kappa numbers of the MOW were as high as 16, and bleached brightnesses of 91% - 94 % ISO when initial kappa numbers were less than 9.

Continuous mechanical agitation on MOW with a high kappa number during bleaching produced a higher final brightness than mixing the chemicals only at the start of the bleach. Increased hydrogen peroxide bleaching temperature, pressurized peroxide bleaching, and bleaching at high consistency produced beneficial results.