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).

In a process for oxidation of white liquor, in particular of white liquor used in a process of production of paper or cellulose, the oxygen required for the oxidation is supplied to the reactor or the reactors in which the oxidation is carried out at least partially in the form of oxygen-containing nanobubbles. Due to the relatively long lifetime of the nanobubbles this very efficiently provides oxygen also for oxidation reactions in the white liquor proceeding at different rates.

A method for manufacturing dissolving pulp using wood material is disclosed. The method comprises subjecting the wood material to a hydrothermal treatment using steam and/or water, digesting the wood material obtained to a pulp in a kraft cooking process; subjecting the pulp to a cold caustic extraction CCE; and dewatering, washing and pressing the pulp to get a pulp product having a carbohydrate content. The wood material can be a coniferous wood material, and whereby the mild hydrothermal treatment is performed to reach a P-factor of from 100-300, and whereby the cold caustic extraction is executed to reach a combined concentration of anhydromannose and anhydroxylose of 5 weight %, or less, of the carbohydrate content of the pulp product.

Some variations provide a process for impregnating a biomass feedstock with a reaction solution, comprising: providing a biomass feedstock that contains non-condensable gases within biomass pores; introducing a condensable vapor into the biomass pores to remove non-condensable gases out of the biomass pores, thereby generating an intermediate biomass material, wherein at least a portion of the condensable vapor remains within the biomass pores; exposing the intermediate biomass material to a liquid solution to infiltrate the liquid solution into the biomass pores and condense the vapor to form a condensed liquid contained within the biomass pores, thereby generating an impregnated biomass material containing a reaction solution; and recovering or further processing the impregnated biomass material. The non-condensable gases may be oxygen, nitrogen, or carbon dioxide, for example. The condensable vapor may be steam, for example. The reaction solution may contain a pretreatment chemical, such as a catalyst and/or a solvent.

The present invention provides reconstituted tobacco and a preparation method thereof, and belongs to the technical field of tobacco. The preparation method provided by the present invention includes the steps of: subjecting tobacco stems to hot-water extraction and pulping by mill successively to obtain tobacco stem pulp; mixing the tobacco stem pulp with alkaline matter for oxygen delignification in an oxygen environment to obtain oxygen-delignified tobacco stem pulp, where the alkaline matter includes one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate and sodium bicarbonate; mixing the oxygen-delignified tobacco stem pulp with tobacco pulp, calcium carbonate and a retention agent, and subjecting the mixture to a papermaking process in the paper machine to obtain reconstituted tobacco sheets; and coating the reconstituted tobacco sheets with a concentrated tobacco extracting solution to obtain reconstituted tobacco. By means of the oxygen delignification of the tobacco stem pulp in the present invention, the lignin component in tobacco stems is partially removed, and the reconstituted tobacco prepared from processed tobacco stems and other raw materials has a soft flavor without wood smell.

A method for manufacturing dissolving pulp using wood material is disclosed. The method comprises subjecting the wood material to a hydrothermal treatment using steam and/or water, digesting the wood material obtained to a pulp in a kraft cooking process; subjecting the pulp to a cold caustic extraction CCE; and dewatering, washing and pressing the pulp to get a pulp product having a carbohydrate content.

The wood material can be a coniferous wood material, and whereby the mild hydrothermal treatment is performed to reach a P-factor of from 100-300, and whereby the cold caustic extraction is executed to reach a combined concentration of anhydromannose and anhydroxylose of 5 weight %, or less, of the carbohydrate content of the pulp product.

Discloses are a method for preparing fluff pulp from bamboos, and the fluff pulp prepared thereby. The method comprises the following steps: treating the bamboos with high-concentration alkali at a relatively mild temperature, after a certain period of treatment, replacing a treatment liquid for separating hemicellulose with a weak black liquor; Kraft cooking the treated bamboos to obtain unbleached bamboo pulp, removing rejects in the unbleached bamboo pulp by using a slotted screen; then removing miscellaneous cells by using a microporous sieve; carrying out two stages of oxygen delignification on the screened pulp; carrying out ECF bleaching treatment of a D.sub.0EpD.sub.1P process; and finally obtaining the bamboo fluff pulp which has high whiteness, low DCM extract content, low ash content and long fiber length, contains 4.2-4.6 million fibers per gram, and has relatively high bulkiness.

Process for the delignification and bleaching of pulp, comprising a first bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture; subsequent to the first bleaching stage, a second bleaching stage with hydrogen peroxide in an alkaline aqueous mixture; and, subsequent to the second bleaching stage, a third bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture.

The present disclosure provides methods and compositions for improving the oxygen delignification process. The methods may include adding low doses of a borohydride stabilized in an alkaline solution to brownstock pulp. The methods may result in significant chemical savings, increased pulp brightness, increased pulp yield, and reduced kappa number.

Discloses are a method for preparing fluff pulp from bamboos, and the fluff pulp prepared thereby. The method comprises the following steps: treating the bamboos with high-concentration alkali at a relatively mild temperature, after a certain period of treatment, replacing a treatment liquid for separating hemicellulose with a weak black liquor; Kraft cooking the treated bamboos to obtain unbleached bamboo pulp, removing rejects in the unbleached bamboo pulp by using a slotted screen; then removing miscellaneous cells by using a microporous sieve; carrying out two stages of oxygen delignification on the screened pulp; carrying out ECF bleaching treatment of a D.sub.0EpD.sub.1P process; and finally obtaining the bamboo fluff pulp which has high whiteness, low DCM extract content, low ash content and long fiber length, contains 4.2-4.6 million fibers per gram, and has relatively high bulkiness.