Patent DE-102007022608-A1 (DE)
Title: Method for partly softening liquid/dispersion for continuous purification of wastewater in paper industry, by supplying a precipitant to the liquid or dispersion for precipitating lime and sparging gas bubbles through the liquid/dispersion
Inventor: MENKE LUCAS
IPC: C02F5/02
Filed: 2007-05-15
Abstract: The method for partly softening liquid/dispersion for continuous purification of wastewater in paper industry, comprises supplying a precipitant to the liquid or dispersion for precipitating lime to form lime particles and sparging gas bubbles through the liquid or the dispersion. The precipitant is supplied to the liquid or to the dispersion while the gas bubbles are sparged through the liquid or the dispersion. The method is carried out such a way that the gas bubbles are sparged through the liquid or the dispersion during the formation or directly after the formation of the lime particles. The method for partly softening liquid/dispersion for continuous purification of wastewater in paper industry, comprises supplying a precipitant to the liquid or dispersion for precipitating lime to form lime particles and sparging gas bubbles through the liquid or the dispersion. The precipitant is supplied to the liquid or to the dispersion while the gas bubbles are sparged through the liquid or the dispersion. The method is carried out such a way that the gas bubbles are sparged through the liquid or the dispersion during the formation or directly after the formation of the lime particles, and as pressure relaxation floatation process. The gas bubbles have an average diameter of 20-60 mu m. Gas is added to the liquid and/or dispersion under pressure and is expanded for forming pressurization, gas subjected liquid or dispersion, so that the gas bubbles form itself in the liquid and/or dispersion as a result of the pressure reduction. The gas bubbles sparge through the liquid or the dispersion, which is added to the precipitant and to a flocculant after the expansion of the gas. The liquid and/or the dispersion is supplied into a container (11), in which a second liquid is supplied over a separate inlet. In the container, the gas is worked out under pressure and is expanded later, so that the gas bubbles form itself in the liquid and the precipitant is supplied into the container over a further separate inlet. The second liquid containing the gas bubbles, and the liquid and/or the dispersion are mixed together in a part of the container having precipitant. The flocculants is introduced into the second liquid before supplying into the container. The retention time of the liquid and/or the dispersion in the container is 1-6 minutes. Stilling basins arranged center in the container is introduced for softening the liquid and/or the dispersion, which enters subsequently radially outward in distributor cells. The distributor cells flow throughable in horizontal and radially tangential manner and enters over discharge openings into a separation basin (61) in which the second liquid is supplied to the liquid and/or the dispersion. The precipitant is supplied to the liquid and/or the dispersion in the area of the perfusion of the discharge opening. The precipitant is a base. The pH value of the liquid and/or the dispersion is 7.5-8.5 after the supplement of the precipitant. The hardness of the liquid and/or the dispersion during the process is 20-80% related on the hardness of the exit liquid and/or the dispersion. Independent claims are included for: (1) a method for continuous purification of wastewater in paper industry; and (2) device for partly softening liquid/dispersion.