Chemical mechanical pulping method for recycling of wet strength waste paper

Abstract

The invention discloses a chemical mechanical pulping method for recycling of wet strength waste paper. The method comprises a material preparation section, a steaming section, a first squeezing dipping chemical mechanical treatment section, a second squeezing dipping chemical mechanical treatment section, a latency and re-defibering section and a purification, screening and concentration section. According to the method, wet strength waste paper fiber dissociation and re-pulping are realized while the original pulp strength is not reduced under the action of mechanical strength and chemical treatment; furthermore, at the two squeezing dipping chemical mechanical treatment sections in series connection, a wet strength agent in the waste paper can be oxidized under the acidic condition firstly, and then hydrolysis is further promoted under the alkaline condition, so that the chemical bonding among molecules of the wet strength agent and between the wet strength agent and pulp fibers are destroyed more effectively, and the fiber dissociation rate and the re-pulping yield are effectively increased. The problems that the wet strength waste paper recycling, pulping and dissociation rate is low and the strength is substantially reduced are solved, and continuous, large-scale, low-water-consumption, low-energy-consumption, pollution-free and environment-friendly pulping can be realized.

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 volume 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%, and South Korea and Germany exceed 80%. my country's waste paper pulping increased from 28.1 million tons in 2005 to 53.05 million tons in 2010, and its proportion in the total pulp consumption increased from 54.0% to 62.7%, of which 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 domestic waste ...

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 has not been 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 It is very low and 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 breakdown 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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