RU2158327C1 - Method of treatment of excessive circulating water of cardboard production for its reuse - Google Patents

Abstract

FIELD: technology of partial closed water circulation in cardboard production. SUBSTANCE: introduced successively into excessive circulating water in coagulant in form of aluminum hydroxide and chloride with aluminum oxide-chloride ratio of 0.71 to 0.92. In this case, flocculant is introduced into excessive circulating water in 30-100 s after introduction into water of coagulant. Polyacrylamide is used in form of cationic polyacrylamide with molecular weight of (5-9)10⁶ or anionic polyacrylamide with molecular weight of (9-15)10⁶. EFFECT: higher efficiency of method. 2 cl, 2 ex

Description

 The invention relates to a technology of partially closed water circulation in cardboard production, in particular to methods for preparing excess recycled water for cardboard production, for its reuse.

 There is a method of preparing excess recycled water for pulp and paper production, in particular, a method for treating wastewater of a sulfate-cellulose production, including introducing coagulant-aluminum sulfate, flocculant-polyacrylimide and flotation reagent -N- (2'-hydroxyethyl) oxazolidine oleic acid (see SU, 1375566, CL C 02 F 1/24, 1/56, publ. 23.02.88, A1).

 According to this method, waste water of a pulp and paper mill containing sludge — lignin and coagulant — aluminum sulfate is used as wastewater, and flocculant and flotation reagent are introduced into the wastewater simultaneously.

 However, this method does not allow for the complete coagulation of the fine fraction, including the colloidal part, in the process of partially closed water circulation.

 There is also known a method for preparing treatment of industrial domestic wastewater with a composition containing aluminum chloride hydroxide, a copolymer based on acrylamide (polyacrylamide) and a buffering additive — sodium carbonate and sodium hydrogen carbonate, or sodium acetate and acetic acid, or sodium hydrophthalate and hydrochloric acid, or sodium hydrogen phosphate and sodium dihydrogen phosphate (see RU, 2114068, class C 02 F 1/56, publ. 27.06. 98, C1).

 Wastewater treatment with such a composition is only suitable for the treatment of effluents from solid and liquid dispersed substances at metal processing plants, in leather production, at fish processing plants, breweries, agricultural processing plants, wastewater from oil, manure, and chemical and electrochemical wastewater.

 However, this method is unsuitable in the processes of preparing excess recycled water of cardboard production for its reuse due to the insufficient degree of heteroflocculation, due mainly to the selective process of homoflocculation of the coarse fraction.

 The closest analogue of the described invention is a method of preparing recycled water for cardboard production for reuse by sequentially introducing into the excess recycled water a coagulant and flocculant - polyacrylamide (see US 3884755, A, n.c. 162-190, IPC D 21 F 1/66 , publ. 20.05.75).

 According to this method, the flocculant is administered 120 to 180 seconds after the introduction of the coagulant. As the latter, bentonite is used in this method.

 However, this method, due to the use of bentonite as a coagulant in it, does not provide the required degree of wastewater treatment from dissolved and highly dispersed anionic substances.

 In addition, the process of coagulation with bentonite is time consuming.

 A new technical result from the use of the described invention is to increase the degree of purification of waste water from cardboard production while reducing fiber loss during reuse of prepared water.

 This result is achieved by the fact that in the method of preparing excess recycled water for cardboard production for its reuse by sequentially introducing coagulant and flocculant polyacrylamide into the excess recycled water, according to the invention, aluminum chloride with a ratio of aluminum oxide to chlorine of 0 is used as a coagulant therein. 71 - 0.92, with the introduction of a flocculant is carried out after 30 - 100 s after the introduction of a coagulant into it.

As polyacrylamide use cationic polyacrylamide with a mol. m. (5-9) • 10 ⁶ or anionic polyacrylamide with a mol. m. (9-15) • 10 ⁶ .

 As the excess recycled water of the cardboard production in the described method, the total water generated from overflows, from the functioning of the sprays and the operation of the presses is used.

 The hydroxide aluminum chloride used in the proposed method is obtained according to TU 6-09-05-1456-96.

 The invention is illustrated by the following examples of its implementation.

Example 1. Take excess recycled water from the production of cardboard liner weighing 155 g / m ² . Coagulant hydroxide aluminum chloride with a ratio of aluminum oxide to chlorine of 0.92 (concentration of an aqueous solution of 200 g / l) in an amount of 40 mg / m of water is introduced into the initial water with a concentration of 493 g / l. 100 s after the introduction of the specified coagulant, cationic polyacrylamide with a mol.m is introduced into the excess circulating water. 7 • 10 ⁶ and the resulting mixture is flotated in a flotation trap.

 The degree of purification of clarified (floated) water from suspended particles is 96%, COD (chemical oxygen consumption) is 300 mg / l.

 The purified water is partially sent for reuse, and partially for sedimentation and biological treatment. The flock from flotovolushki return to the production of cardboard.

Example 2. The method is carried out analogously to example 1, but using aluminum hydroxide chloride with a ratio of aluminum to chlorine of 0.71 in it. 30 s after the introduction of the specified coagulant in excess recycled water is introduced anionic polyacrylamide with a mol. m. 12 • 10 ⁶ .

 The degree of purification of clarified (floated) water from suspended particles is 95.5%, COD - 350 mg / l.

 The purified water is partially sent for reuse, and partially for sedimentation and biological treatment. Osprey from flotation is returned to the production of tuberous gaskets.

In parallel, for comparison, the prototype method is carried out, according to which first a coagulant - bentonite is introduced into the same drain, and then, after 150 s, polyacrylamide is introduced (cationic with a mol. M. 7 • 10 ⁶ ).

 The degree of purification of clarified water from suspended particles is 82%, COD - 1000 mg / l.

 The purified water is partially sent for reuse, and partially for sedimentation and biological treatment.

 The reduction in fiber loss by the proposed method is due to a higher degree of purification (13.5-14%) at the flotation stage.

Claims (2)

 1. A method of preparing excess recycled water for cardboard production for reuse by sequentially introducing a coagulant and flocculant polyacrylamide into excess recycled water, characterized in that aluminum chloride with a ratio of aluminum oxide to chlorine of 0.71-0 is used as a coagulant therein , 92, while the introduction of a flocculant into excess circulating water is carried out after 30 - 100 s after the introduction of a coagulant into it. 2. The method according to claim 1, characterized in that as the polyacrylamide use cationic polyacrylamide with mol. m. (5 - 9) • 10 ⁶ or anionic polyacrylamide with a mol. m. (9 - 15) • 10 ⁶ .