Comparison of High Consistency Ozonation and Peracids as Bulk Delignifiers of Pine Pulp, 1996 International Pulp Bleaching Conference Proceedings

Since 1992, Union Camp has been using high consistency ozone bleaching at its Franklin mill to produce 85 brightness pine pulp in an ECF sequence. Peracids represent another class of bleaching agents, and are under consideration by others as low capital cost alternatives to ozone bleaching. The delignification performance and process economics of HC ozonation and peracid (specifically Pxa) are compared in this paper. High consistency ozone bleaching is shown to be superior to Pxa as a bulk delignifier of kraft/oxygen delignified southern pine pulp. The extent of delignification achievable with Pxa is limited. As a result, ozone delignified pulps are substantially easier to bleach to final brightness in ECF and TCF sequences. Selectivity relative to lignin removal (delta KNumber/Aviscosity) is comparable for the two systems. The relative costs to produce 84 brightness pine pulp using OPxaEopD and OZEoD sequences were compared for hypothetical mills of 500, 1000 and 1500 ADMTPD capacity. Pxa has an attraction because of its low capital cost relative to the ozone stage. This benefit, however, is more than offset by the substantially higher chemical cost requirements. This study demonstrates that HC ozonation is superior to peracid as a bulk delignifier, and is also more economical on a total cost basis for producing high brightness ECF pulps from oxygen delignified pine feedstocks.