Double-pH-value wet-strength waste paper recycling pulping method

Abstract

The invention discloses a double-pH-value wet-strength waste paper recycling pulping method. The method includes a material preparation work section, a steaming work section, a first extrusion and dipping chemical-mechanical treatment section, a second extrusion and dipping chemical-mechanical treatment section, a latency and re-defibering section and a purification, screening and concentration section. According to the method, fiber dissociation and re-pulping of wet-strength waste paper are achieved under the effects of strong mechanical force and chemical treatment without reducing the strength of raw paper pulp; furthermore, in the two serial extrusion and dipping chemical-mechanical treatment sections, a wet-strength agent in the waste paper is oxidized under the acidic condition, and then hydrolysis is further promoted under the alkaline condition, so that chemical bonding between molecules of the wet-strength agent and chemical bonding between the wet-strength agent and pulp fibers are effectively damaged, and the fiber dissociation rate and the re-pulping yield are effectively increased. The problems that in wet-strength waste paper recycling pulping, the dissociation rate is low and strength is substantially reduced are solved, and continuous, large-scale, pollution-free and environment-friendly pulping with low water consumption and energy consumption can be achieved.

Description

[0001] This application is a divisional application for an invention patent titled: A chemical mechanical pulping method for recycling and reusing wet strength waste paper, the application number is: 2014103492050, and the application date is July 21, 2014. technical field [0002] The invention relates to a pulping system and a pulping method, in particular to a waste paper recovery and reuse chemical mechanical pulping system and pulping method. Background technique [0003] Waste paper is an important fiber raw material for papermaking. All countries attach great importance to the recycling of waste paper resources. The world's waste paper recycling increased from 182.6 million tons in 2005 to 223.4 million tons in 2010; the recovery rate increased from 49.8% to 56.6%. , developed countries generally exceed 60%, South Korea, Germany more than 80%. my country's waste paper pulping increased from 28.1 million tons in 2005 to 53.05 million tons in 2010, accounting for the pr...

AI Technical Summary

Problems solved by technology

The disadvantages of this technology are (1) the production of high-consistency pulp is discontinuous and takes a long time; (2) the power consumption is high; (3) the wet strength agent is not chemically treated, which will cause Re-flocculation affects paper making; (4) The presence of wet strength agents will affect the use of other chemicals such as resident additives during paper making

Existing problems: (1) The yield of waste paper pulp is low, and a large amount of fiber raw materials are degraded and enter the pulping wastewater, which increases the difficulty and cost of wastewater treatment; (2) If the dissociated waste paper pulp is not bleached, the pulp whiteness Very low, it can only be used in some paperboards that do not require high whiteness, and the use of pulp is limited; (3) The chemical cooking method has a strong chemical effect on waste paper pulp, resulting in a decrease in the degree of cellulose polymerization, which leads to a physical degradation of the pulp. decrease in strength

[0014] Existing problems: hypochlorite treatment can effectively treat bleached PAE wet-strength paper, and the cost is low, but it cannot completely repulp non-bleached wet-strength paper, and it will increase the amount of chloroform and tetrachloride in the discharged sewage. Loading of adsorbable organic halides (AOX) such as ethane, which is also a negative factor limiting the use of hypochlorite

[0018] Problems: During the neutral or alkaline repulping process, because the free radicals generated by the decomposition of peroxodisulfate can extract the hydrogen on the lignin to form non-reactive free radicals, so that most of the wet strength resins are not damaged. Oxidation, therefore, peroxodisulfate is not very effective for unbleached kraft pulp, chemical thermomechanical pulp and OCC wet strength paper, which is difficult to repulp

Although an excess of peroxodisulfate can overcome this side reaction, it is too expensive, inefficient and damaging to the fiber

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