Peroxide Bleaching Study of Softwood TMP with Mg based Alkali Produced from Natural Brucite
Updated: 2016-10-27 | Print
a Russian Mining Chemical Company LLC, Lusinovsakaya Street 36, RU- 115093, Moscow, Russia
b A Fredrikson Research & Consulting Ltd, Vähäkuja 2, FI-40520, Jyväskylä, Finland
c Paper and Fibre Research Institute (PFI), NO-7491, Trondheim, Norway
High brightness is a valuable asset for paperboards and printing papers. Therefore, many mills would like to upgrade to higher brightness grades. Environmental awareness, in turn, tightens COD limits of the mills’ effluents. It is a challenge to meet targets simultaneously for high brightness and low-wastewater COD. For the first time, natural Mg(OH)2 was successfully tested in pulp bleaching process. We report mechanical pulp laboratory bleaching trials with Mg(OH)2 as partial alkali source. The target was to evaluate the suitability of a new origin and manufacturing method of Mg(OH)2. The product is manufactured from the mineral brucite—natural Mg(OH)2. After mining, brucite ore is crushed and classified on site by x-ray separation. The fraction with the highest magnesium hydroxide content and the lowest concentration of impurities—which can have an effect on the process—is selected for the production of Mg(OH)2 for mechanical pulp bleaching. The manufacture of natural Mg(OH)2 is a simple and environmentally friendly process—its cost structure is less dependent on the price of energy and it has lower CO2 emissions than that production of synthetic Mg(OH)2. An unbleached TMP pulp was bleached in a laboratory with hydrogen peroxide H2O2 and various dosages of Mg(OH)2 alkali. The effects of mean particle size of Mg(OH)2 was studied as well. We also compared the bleaching processes of natural Mg(OH)2 to bleaching with NaOH, as well as synthetic Mg(OH)2 2 grades, and discussed the differences. The manufacturing process of Mg(OH)2 from brucite, magnesite and sea water/well brine have different stages and environmental impacts which are quantified. In conclusion, natural Mg(OH)2 is suitable for peroxide bleaching of TMP and CTMP pulp for paper boards and printing papers.