Wet-strength wastepaper recycling double-pH-value chemical and mechanical pulping method

Abstract

The invention discloses a wet-strength wastepaper recycling double-pH-value chemical and mechanical pulping method. The method includes a material preparation section, a steaming section, a first extrusion and impregnation chemical and mechanical treatment section, a second extrusion and impregnation chemical and mechanical treatment section, a latency and re-defibering section and a purification, screening and concentration section. Wet-strength wastepaper fiber dissociation re-pulping is achieved while original pulp strength is not reduced through the mechanical strong force effect and the chemical treatment effect. Furthermore, on the two extrusion and impregnation chemical and mechanical treatment sections connected in series, a wet strength agent in wastepaper is oxidized under the acid condition firstly, hydrolysis is further promoted under the alkaline condition, chemical bonding between molecules of the wet strength agent and between the wet strength agent and pulp fibers is more effectively damaged, and the fiber dissociation rate and the re-pulping yield are effectively increased. The problems that the wet-strength wastepaper recycling pulping dissociation rate is low and strength is greatly decreased are solved, and continuous, large-scale, low-water-consumption and low-energy-consumption pollution-free and environment-friendly pulping can be achieved.

Description

technical field [0001] 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 [0002] 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 proportion of total pulp consumption increased from 54.0% to 62.7%, of which the proportion of domestic waste paper pulp increased from 27.8% to 38.0%. During the "Twelfth Five-Year Plan" period, the increase in waste paper pulp is about 14 million tons. The r...

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

[0013] 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

[0017] 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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