An oxygen bleaching method of pulp includes the steps of: adding a solution formulated by a magnesium salt and an activator to an unbleached chemical pulp, stirring to be mixed well, and bleaching by introducing oxygen. The activators are nano zero-valent metals that are conventional, low-cost, and recyclable. These activators can activate low-concentration oxygen at low-temperature in neutral aqueous solution to efficiently generate peroxide anion radicals, so as to promote the generation of hydroperoxide anions and peroxide ions, achieving high efficient delignification. The whole process does not generate waste water, the oxygen consumption is only 50-85% of the original process, the yield is increased by 1.5-2.8% compared with the original system, the pulp brightness is increased to 28-32° SR, and the magnesium salt can be recycled and reused.

A method of producing high yield chemical cellulosic pulp includes: (a) chemically pulping wood chips to separate lignin and liberate cellulosic fibers from the wood chips to generate a cellulosic pulp; (b) washing and screening the pulp of step (a); (c) pre-treating the washed pulp with oxygen; (d) optionally washing the treated pulp of step (c); (e) bleaching the pre-treated pulp in an extended duration oxidative bleaching stage; (f) optionally washing the bleached pulp of step (e); and (g) optionally further oxidatively or reductively bleaching the bleached pulp in a shorter duration bleaching stage, wherein the bleached pulp is produced at a yield of greater than 60% based on the weight of the pulped wood chips (dry basis).

Recycle fiber bleaching includes an oxygen pre-treatment to activate the fiber for further bleaching. A preferred method of making a high brightness papermaking pulp from recycled cellulose fiber includes: (a) pre-treating a first recycled cellulosic fiber mix with oxygen, said first recycled cellulosic fiber mix having a first high Kappa number prior to pre-treatment and a reduced Kappa number after pre-treatment that is lower than said first high Kappa number; and (b) blending the pre-treated first recycled cellulosic fiber mix with the reduced Kappa number with a second recycled cellulosic fiber mix having a second Kappa number lower than the first high Kappa number of the first recycled cellulosic fiber mix; and (c) oxidatively bleaching the blended recycled cellulosic fiber mix of step (b); and optionally (d) reductively bleaching the blended recycled cellulosic fiber mix of step (c).

A process for producing dissolving pulp from comminuted wood-based fibrous material. The process includes the following consecutive stages: cooking comminuted fibrous material with alkaline cooking liquor in a kraft cooking process to produce pulp; treating the cooked pulp in caustic extraction at a temperature of 70-110 C. and in an effective alkali concentration of 60-120 g/l for at least 5 minutes, and washing and oxygen delignifying the caustic extracted pulp.

The application relates to a method for preparing dissolving pulp by totally chlorine-free bleaching of poplar kraft pulp, including: preparing poplar kraft pulp by pre-hydrolysis kraft process with poplar as raw material; ZOQP bleaching of poplar kraft pulp to obtain dissolving pulp, wherein Z denotes ozone bleaching, O denotes oxy delignification, Q denotes chelation treatment, and P denotes hydrogen peroxide bleaching. In this way, washing and bleaching wastewater can be recycled in entire preparation process described above, achieving zero discharge. The dissolving pulp prepared by the method has no residual toxic substances, and exhibits that all indexes exceed the requirements of qualified products in dissolving pulp industry standard (QB/T 4898-2015), and most of indexes meet those of excellent products; thus, it can replace imported dissolving pulp. The use of the method significantly solved the problems of large pollution in the production and shortage of raw materials for viscose fibers.

The present invention is directed to a method for scouring and increasing the brightness of non-wood fibers. The method comprises forming a mixture of non-wood fibers, exposing the mixture to a scouring liquor and a scouring agent comprising oxygen gas to form a scouring mixture, and scouring the scouring mixture by radially circulating the scouring liquor throughout the scouring mixture to provide scoured fibers.

The present invention is directed to a method for scouring and increasing the brightness of non-wood fibers. The method comprises forming a mixture of non-wood fibers, exposing the mixture to a scouring liquor and a scouring agent comprising oxygen gas to form a scouring mixture, and scouring the scouring mixture by radially circulating the scouring liquor throughout the scouring mixture to provide scoured fibers.

The present invention relates to treatment of unbleached or partially bleached or alkaline extracted dissolving pulp with one or more cellulases. The cellulase treatment results in increased viscosity control, reduced viscosity and/or increased reactivity of the final dissolving pulp.

An oxygen bleaching method of pulp includes the steps of: adding a solution formulated by a magnesium salt and an activator to an unbleached chemical pulp, stirring to be mixed well, and bleaching by introducing oxygen. The activators are nano zero-valent metals that are conventional, low-cost, and recyclable. These activators can activate low-concentration oxygen at low-temperature in neutral aqueous solution to efficiently generate peroxide anion radicals, so as to promote the generation of hydroperoxide anions and peroxide ions, achieving high efficient delignification. The whole process does not generate waste water, the oxygen consumption is only 50-85% of the original process, the yield is increased by 1.5-2.8% compared with the original system, the pulp brightness is increased to 28-32? SR, and the magnesium salt can be recycled and reused.

The present invention relates to treatment of unbleached or partially bleached or alkaline extracted dissolving pulp with one or more cellulases. The cellulase treatment results in increased viscosity control, reduced viscosity and/or increased reactivity of the final dissolving pulp.