Preparation method of cutting-free rice and wheat straws by alkaline cooking through vertical digester

Abstract

The invention provides a preparation method of straw pulp by alkaline cooking through a vertical digester without straw cutting. The preparation method comprises the steps of: washing cutting-free straw raw materials, and putting the straw raw materials into the vertical digester; adding a hot alkali solution, and carrying out liquor circulation cooking by using a conventional sulfate method or caustic soda anthraquinone method; when lignin released by the straw raw materials reaches 80-90% by cooking, discharging free black liquor, supplementing a part of an alkali solution for continuous liquor circulation to the cooking temperature, stopping the liquor circulation, and preserving heat until the cooking is finished; and performing conventional pulp washing, so as to obtain unbleached pulp, and conveying the obtained black liquor to an alkali recovery system. According to the preparation method, the straw materials are not cut, and the liquor circulation is unobstructed and the straw materials are uniformly cooked into the pulp in the vertical digester by utilizing good appearance and maintained characteristics of the straw materials before pulping, so that on the premise of ensuring the quality of cooking, the solid matter concentration of the black liquor can be up to more than 12%, the raw material stock loss can be reduced by about 5%, the cooking capability of unit digester volume can be improved by about 10%, the pulp yield and the viscosity are improved by different degrees, and the level of efficient, energy-saving and clean production of the straw pulp is improved significantly.

Description

Technical field [0001] The invention relates to a method for preparing straw pulp, in particular to a method for preparing straw pulp by directly performing vertical pot cooking without cutting the grass, and belongs to the technical field of papermaking. Background technique [0002] Grass-based raw materials are a huge potential resource of my country's paper industry. In the past, it was used as an important alternative resource for wood to support my country's paper industry for nearly half a century. It's just that the inherent deficiencies of grass fiber raw materials not only restrict the use of high-efficiency energy-saving pulping technology and equipment, but also seriously affect the advancement of clean pulp production. The country had no choice but to restrict the development of straw pulping technology in the late 1990s. Today, the proportion of the straw pulping industry has been reduced to less than 20%. Instead, a large amount of pulp raw materials are imported...

AI Technical Summary

Problems solved by technology

However, the pulping of grass is easy to bridge or form embolism due to its loose tissue structure, which affects the normal operation of cooking

Moreover, as the cooking progresses, the fragmentation of the forage tends to block the grate, making the cooking liquid unable to circulate, so it cannot be used in the pulping equipment with the vertical pot as the mainstream

Therefore, the cooking vessel selected for rice and wheat straw cooking is either steamed with a low-energy-efficiency steamer, or the horizontal tube continuous digester can only be used to obtain pulp with large fluctuations in quality and poor drainage performance.