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RECYCLING AND CLOSING OF WATER CIRCUITS IN PAPER MILLS LE RECYCLAGE ET LA FERMETURE DES CIRCUITS DE L'EAU DANS L'INDUSTRIE DU PAPIER


CONSTANTIN STANCIU*, GHEORGHE CANTEMIR
INSTITUTIEUNIVERSITÉ « DUNĂREA DE JOS GALAŢI »,
FACULTÉ D’INGÉNIERIE, BRĂILA,
29 RUE CÄ‚LÄ‚RAĹžI, RO - 810017, BRÄ‚ILA, ROUMANIE
*CORRESPONDING AUTHOR: DECANATBR@UGAL.RO

Issue:

SCSCC6, Volume IX, No. 3

Section:

Volume IX, No. 3 (2008)

Abstract:

Water plays a basic role in the pulp and paper processes. A modern paper mills generally consumes 10-50 m3 water/tone of paper and removes an equivalent quantity of excess white water polluted with dissolved substances and suspended solids. The paper grade produced is an important factor influencing fresh water consumption and solid losses. To diminish the environmental impact of paper mills, generally speaking, a combination of internal and external actions is necessary: closure of white loop i.e. reduction of fresh water consumption and effluent volume; loss collection and sludge and waste treatment system. The closure of circuits can be carried out by: (i) white water recirculation after removing fibers and fine materials; (ii) restriction of fresh water consumption in white loop.

The paper shows in its first part, the problems of closure advantages and disadvantages of closing the circuits of paper machines.

The circuit closure in a paper mill drives the following: (1) increase of amount of suspended solids or colloidal substances in white water; (2) increase of amount of organic and inorganic substances dissolved in white water; (3) a rise of temperature in water circuit.

Operation difficulties may occur such as: corrosion, deposits and also production conditions are influenced lower retention of fillers, lower dewatering, increase of slime and of foaming odor and quality problems (diminishing of paper mechanical strength by 10% to 20 % or less).

The positive effects of circuit closure in paper mill are reduction of fiber and filler losses, reduction of energy costs and investment and operation costs for the treatment plant. The rise of raw and energy costs normally leads to a closure rate of 5 to 10 m3 fresh water/tone of paper. The removal efficiency of soluble materials becomes very important (> 95 %) in terms of restricting the problems related to closure of circuits.

Keywords:

paper, white water, zero effluent liquid.

Code [ID]:

CSCC6200809V03S01A0003 [0002401]

Full paper:

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