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The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibres, the main component of paper. The kraft process involves treatment of wood chips with a hot mixture of water, sodium hydroxide (NaOH), and sodium sulfide (Na 2 S), known as white ...
Recovery boiler is the part of kraft process of pulping where chemicals for white liquor are recovered and reformed from black liquor, which contains lignin from previously processed wood. The black liquor is burned, generating heat, which is usually used in the process of making electricity, much as in a conventional steam power plant. The ...
Chemical pulping involves dissolving lignin in order to extract the cellulose from the wood fiber. The different processes of chemical pulping include the Kraft process, which uses caustic soda and sodium sulfide and is the most common; alternatively, the use of sulfurous acid is known as the sulfite process, the neutral sulfite semichemical is treated as a third process separate from sulfite ...
The kraft process does less damage to the cellulose fibers than the sulfite process, thereby producing stronger fibers, but the sulfite process makes pulp that is easier to bleach. The chemical pulping processes use a combination of high temperature and alkaline (kraft) or acidic (sulfite) chemicals to break the chemical bonds of the lignin.
After the cellulose fibers are separated from the lignin, a pulp is created which can then be treated to create durable paper, boxes, and corrugated cardboard. Chemical pulping can be characterized by two main methods: sulfate (Kraft process) pulping and sulfite pulping, and these two methods have different benefits. Sulfate pulping can be ...
This, along with the ability of the kraft process to accept a wider variety of types of wood and produce stronger fibers [4] made the kraft process the dominant pulping process starting in the 1940s. [3] Sulfite pulps now account for less than 10% of the total chemical pulp production [3] and the number of sulfite mills continues to decrease ...
H-factor is a kinetic model for the rate of delignification in kraft pulping. It is a single variable model combining temperature ( T ) and time ( t ) and assuming that the delignification is one single reaction .
The kraft process, due to the alkali and sulphur compounds used, tends to minimize attack on the cellulose and the non-crystalline hemicellulose, which promotes bonding, while dissolving the lignin. Acidic pulping processes shorten the cellulose chains. Kraft pulp makes superior linerboard and excellent printing and writing papers.