RU2155720C1 - Method of treating waste water from production of fibrous intermediate products for paper and cardboard manufacture - Google Patents

Abstract

FIELD: paper-and-pulp industry. SUBSTANCE: invention, in particular, relates to production of defibering, refiner, thermomechanical, and chemical-thermomechanical pulp. To waste water are added coagulator aluminum chloride hydroxide (aluminum oxide-to-chlorine ratio 0.71-0.92), then clump from flotation traps of intrashop purification of excess cardboard production return water, and then remaining amount of coagulator. 30- 180 s after the second addition of coagulator, waste water is supplemented by polyacrylamide flocculant, in particular anionic polyacrylamide with molecular weight (9-15) 10⁶. EFFECT: increased degree of purification. 2 cl, 3 ex

Description

 The invention relates to a technology for the treatment of effluents from the production of fibrous semi-finished products for the manufacture of paper and paperboard - cellulose and wood pulp (defibre, refiner, thermomechanical, chemical-thermomechanical), mainly from the production of chemical-thermomechanical pulp.

A known method of treating sewage sludge - sludge-lignin from the pulp and paper industry, including treating it with a coagulant - aluminum sulfate, a flocculant - polyacrylamide and a water repellent - a mixture of primary amines hydrochlorides C ₁₂ -C ₁₅ -ANP-2, while the treatment with said water repellent is carried out before or after processing the lignin slurry with a flocculant (SU, 1061411, class C 02 F 11/14, A).

 However, this method, requiring the additional introduction of a water repellent, is not suitable for treating wastewater from the production of fibrous semi-finished products and, in particular, from the production of wood pulp, as in this method, there is insufficient sedimentation.

 There is also known a method of treating industrial and 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 potassium hydrophthalate and hydrochloric acid, or sodium hydrogen phosphate and sodium dihydrogen phosphate (see RU, 2114068, class C 02 F 1/56, publ. 06/27/98, 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, tanneries, fish processing plants, breweries, agricultural processing plants, wastewater from oil, manure, chemical and electrochemical wastewater.

 However, this method is unsuitable for wastewater treatment of the production of semi-finished products of various types of pulp and wood pulp for the manufacture of paper and cardboard due to the introduction of a buffering additive, which would cause stabilization of lignin derivatives. In addition, the simultaneous introduction of all components (in the form of a composition) would lead to the flocculation of only the slurry part of the pulp, which would cause only selective treatment of the wastewater, for the treatment of waste water for the production of fibrous semi-finished products for paper and cardboard.

 The closest analogue of the described invention in technical essence is a method of treating wastewater from the production of fibrous semi-finished products for the manufacture of paper and cardboard, including the steps of introducing into the wastewater a coagulant and flocculant - polyacrylamide (see SU, 1375566, class C 02 F 1/24, 1 / 56, publ. 23.02.88, A1).

 According to this method, aluminum sulphate is used as a coagulant, and cellulose sulphate wastewater containing sludge-lignin and said coagulant is used as the initial wastewater. In addition, this method involves the introduction of a flotation reagent, which is used as N- (2'-hydroxyethyl) oxazolidine oleic acid, and the specified introduction is carried out simultaneously with the introduction of the flocculant. These two reagents are introduced into waste water containing a coagulant - aluminum sulfate.

 However, this method does not allow for a high degree of purification, and, first of all, for effluents from the production of wood pulp.

 A new technical result from the use of the described invention is to increase the degree of wastewater treatment by improving the coagulation process of the colloidal part of the system, followed by its effective adsorption on the coarse fraction and lower COD of treated clarified water.

 This result is achieved by the fact that in the method of treating wastewater from the production of fibrous semi-finished products for the manufacture of paper and paperboard, comprising the steps of introducing into the wastewater a coagulant and a flocculant - polyacrylamide, according to the invention, aluminum chloride with a ratio of aluminum oxide to chlorine is used as a coagulant therein from 0.71 to 0.92, an osprey from the flotation traps of the in-plant cleaning of excess recycled water from cardboard production is additionally introduced into the waste water, and the coagulant is introduced into two doses, first the coagulant is introduced into the initial wastewater, and then into the wastewater after mixing it with the drain, while the second coagulant is introduced and the flocculant is introduced sequentially with an interval between the indicated steps of 30-180 seconds.

As the polyacrylamide, it is preferable to use anionic polyacrylamide with a molecular weight of (9-15) • 10 ⁶ , since it is precisely in the proposed set of features that the specified polyacrylamide in combination with osprey will make it possible to clarify water more deeply from the production of fibrous semi-finished products.

 As a source of wastewater, preferably take wastewater from the production of alkaline wood pulp - chemical-thermomechanical.

 Used in the proposed method, aluminum hydroxide is obtained according to TU 6-09-05-1456-96.

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

 Example 1. Take wastewater from the production of chemical-thermomechanical pulp obtained by preliminary alkaline treatment of wood chips of hardwood and subsequent refining.

 A coagulant, aluminum chloride hydroxide, with a ratio of alumina to chlorine of 0.92 in it is introduced into said wastewater.

The consumption of aluminum chloride hydroxide is 50 g / m ^{3 of the} total volume of treated wastewater, which is 50% of the total coagulant consumption.

Then, wasp is added to the wastewater from the flotation traps of the in-shop treatment for excess recycled water produced by a cardboard liner weighing 150 g / m ² in an amount of 20 volume percent of the volume of wastewater.

Then, the remaining amount (50 g / m ^{3 of} water, which is 50%) of the coagulant — aluminum chloride hydroxide — is introduced into the wastewater mixed with osprey. 180 seconds after the indicated introduction of the coagulant (its second introduction), a flocculant — anionic polyacrylamide with a molecular weight of 12 • 10 ⁶ in the amount of 0.8 g / m ^{3 of} water - is introduced into the resulting system. After 10 s, the stock is flotated in a flotation trap. The degree of wastewater treatment is 92%. COD (chemical oxygen demand) is 500 mg / L. The optical density of clarified water is 0.7.

Example 2. The experiment is carried out analogously to example 1, but using aluminum chloride hydroxide with a ratio of aluminum oxide to chlorine of 0.71 in it. Anionic polyacrylamide with a molecular weight of 15 • 10 ⁶ is administered 30 seconds after the second injection of coagulant (50% of its total consumption) in an amount of 1 g / m ³ water. Flotation begins 5 seconds after flocculant administration.

 The degree of wastewater treatment is 94%. COD is 300 mg / L. The optical density of clarified water is 0.6.

Example 3. The experiments are carried out analogously to example 1, but using aluminum chloride hydroxide with a ratio of aluminum oxide to chlorine of 0.80. Anionic flocculant - polyacrylamide with a molecular weight of 9 • 10 ⁶ is administered 110 s after the second injection of the coagulant, and flotation begins after 7 seconds. after the introduction of a flocculant.

 The degree of wastewater treatment is 94.5%, COD is 400 mg / l, the optical density of wastewater is 0.65.

For comparison, a prototype experiment is carried out using aluminum sulfate as a coagulant contained in the source wastewater and using a flotation reagent N- (2'-hydroxyethyl) oxazolidine oleic acid, which is simultaneously introduced together with the flocculant. On the same drain - water from the production of chemical-thermomechanical mass, the following results were obtained:
degree of purification - 88%,
COD - 100 mg / l
optical density - 1.5.

 Thus, the proposed method allows to increase the degree of wastewater treatment from the production of fibrous semi-finished products.

Claims (2)

 1. A method of treating wastewater from the production of fibrous semi-finished products for the manufacture of paper and paperboard, comprising the steps of introducing into the wastewater a coagulant and a flocculant - polyacrylamide, characterized in that aluminum chloride with a ratio of aluminum oxide to chlorine of 0, is used as a coagulant therein. 71 to 0.92, an osprey from flotation traps of intra-workshop cleaning of excess recycled water for cardboard production is additionally introduced into the wastewater, and the coagulant is introduced in two steps, first coagulating m is introduced into the original waste water, and then in the effluent after introduction therein Osprey, wherein the second administration of coagulant and flocculant administering is performed sequentially with an interval between said steps 30 - 180 sec. 2. The method according to claim 1, characterized in that as the polyacrylamide use anionic polyacrylamide with a molecular weight of (9 - 15) • 10 ⁶ .