|Magnefite Pulping Process for Chlorine free Bleaching||Australia||-||Full scale|
MANUFACTURE OF PAPER AND PAPER PRODUCTS # 1
This case study was submitted on the part of the Working Group on Cleaner Production in Pulp and Paper Industries in the framework of the UNEP IE/PAC Cleaner Production Program with the support of the Technical Research Center of Finland's Non-Waste Technology Research Unit.
Cleaner Production Principle
Cleaner Production Application
The Magnefite pulping process was chosen for the Apcel redevelopment for the following reasons:
|Sulfite pulp has an unbleached brightness of 55% compared with 30% for Kraft pulp. This allows sulfite pulp to be bleached to a level acceptable to the market, without the use of chlorine or chlorine compounds.|
|The capital cost of an installed and operating Magnefite mill is approximately half to two-thirds of that of a Kraft mill.|
|The Magnefite process allows recovery and recycling of the cooking chemicals.|
The spent cooking liquor would pass through the following steps in the chemical recovery stage :
The liquor is concentrated by evaporation in several stages and combusted in a recovery boiler, resulting in the formation of magnesium oxide and sulfur dioxide in the boiler flue gases. Chemical recovery follows, where magnesium oxide would be recovered in a wet scrubber. The magnesium oxide would then be passed to another scrubber through which the sulfur dioxide-rich flue gases would pass, resulting in the formation of raw magnesium bisulfite liquor. The raw liquor would be clarified and filtered for reuse.
The pulp would be bleached using the peroxide steep bleaching process.
The secondary treatment plant would consist of either aeration lagoons or activated sludge treatment, or a combination of these two techniques.
Significant improvements in effluent quality would result from the proposed redevelopment.
The expansion in soft-wood chemical pulping capacity would be achieved by the construction of a new chemical pulp mill with a capacity of 250 ADt/d (90,000 ADt/a). The existing chemical pulp mill would be converted to a 110 ADt/d (40,000 ADt/a) Eucalyptus mill.
Environmental and Economic Benefits
By the proposed redevelopment of the Apcel operations, the company will meet the community expectations for effluent discharges to the adjacent Lake Bonney. Applicable effluent standards will be met or bettered. Odorous air emissions resulting from the pulp cooking process will be reduced. The use of chlorine or chlorine compounds to bleach pulp will be eliminated. The acute and chronic toxicity of effluent will be reduced. The solid waste disposal practices will be improved.
|Material Category||QTY Before||QTY After|
|Waste Generation : BOD||188 kg/ADt||7 kg/ADt|
|- AOX||7,6 kg/Adt||<0,1 kg/ADt|
|- Total suspended solids||15,4 kg/Adt||5 kg/Adt|
|- Color||1,075 HU||<200 HU|
|Water Use:||35 ML/d||35 ML/d|
|Energy Use:||21 MW||27 MW|
The project would cost 195 million Australian dollars.
The existing chemical pulp mill would require comparatively few equipment changes to convert it to the magnefite process. These changes would include a new large dual use heat exchanger, an additional washing stage, new primary and secondary knotter screens, pumps and pipework to transfer cooking liquor, and fans and ductwork to transfer non-condensable gases to the new pulp mill recovery plant.
This case study was submitted by the UNEP Working Group on Cleaner Production in the Pulp and Paper Industries, based at the Technical Research Center of Finland (address above) in 1992, as part of a contract for UNEP IE. Before submission, the case studies were reviewed at the Center. They were edited for the ICPIC diskette in June 1997.Subsequently the case study has undergone another technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.