Method and device for hydrolysis pulping in transcritical CO2 reaction system

Abstract

The invention discloses a method for hydrolyzing pulping. The method comprises the following steps: (1) preparing raw materials, namely, mixing water and wood chips or grass chips in mass ratio of 2:1-200:1, and then preheating; (2) caryring out hydrolyzing reaction, namely, feeding a mixture obtained in step (1) into a reactor, charging CO2 into the reactor, wherein the temperature in the reactor is 80 to 500 DEG C and the pressure is 3 to 50MPa; enabling the charged CO2 to enter a supercritical state or a subcritical state under the conditions that the temperature in the reactor is 80 to 500 DEG C and the reaction pressure is 0.5 to 50.0MPa; (3) discharging the mixed reacted gas from the reactor; and (4) reacting for 1 to 6 hours, discharging pressure-reduced materials from the reactor, and reacting to obtain pulp and reducing sugar. According to the method, supercritical / subcritical CO2 is dissolved in water to be used as protonic acid to replace caustic soda or sulphate or sulfite to pulp by the chemical method, so that the emission amount of heavy-polluted wastewater can be reduced; in addition, the pulping method is free of black liquor or waste gas emission, so that the pulping method is an environmentally-friendly pulping method.

Description

technical field [0001] The invention relates to the field of papermaking and pulping, in particular to a method and device for hydrolyzing pulping in a transcritical CO2 reaction system. Background technique [0002] Paper and cardboard are mainly made of pulp, and the pulping methods can be divided into: chemical method and mechanical method, as well as chemical mechanical method and semi-chemical method in between. Among the world's pulp production, chemical pulp accounts for 72.4%, mechanical pulp accounts for 16.6%, and the rest accounts for about 11.0%. Chemical pulping is divided into alkali method and acid method, and the alkali method includes lime method and caustic soda method. The main purpose of chemical pulping is to remove as much intercellular lignin as possible from the plant fiber raw materials that binds the fibers together to make pulp. The pulping process mainly includes cooking, washing and bleaching processes. The cooking process is high-temperature c...

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Problems solved by technology

At present, most paper mills in China use alkaline pulping, and the black liquor discharged is the wastewater with the highest concentration of pollutants and the deepest color in the pulping process, which contains a large amount of degradation products such as lignin and hemicellulose, pigments, Pentose sugars, residual alkali and other leached substances, about 10 tons of black liquor are discharged for every ton of pulp produced, which not only causes waste of plant resources but also causes serious environmental pollution problems, which is the most difficult problem and research hotspot in the paper industry

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