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The sulfite process is acidic and one of the drawbacks is that the acidic conditions hydrolyze some of the cellulose, which means that sulfite pulp fibers are not as strong as kraft pulp fibers. The yield of pulp (based on wood used) is higher than for kraft pulping and sulfite pulp is easier to bleach .
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 ...
Lignosulfonates (LS) are water-soluble anionic polyelectrolyte polymers: they are byproducts from the production of wood pulp using sulfite pulping. [1] Most delignification in sulfite pulping involves acidic cleavage of ether bonds, which connect many of the constituents of lignin. [2]
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.
Dissolving pulp is mainly produced chemically from pulpwood in a process that has a low yield (30 - 35% of the wood). This makes up of about 85 - 88% of the production. [2] Dissolving pulp is made from the sulfite process or the kraft process with an acid prehydrolysis step to remove hemicelluloses. For the highest quality, it should be derived ...
Pulp mills have used black liquor as an energy source since at least the 1930s. [8] Most kraft pulp mills use recovery boilers to recover and burn much of the black liquor they produce, generating steam and recovering the cooking chemicals (sodium hydroxide and sodium sulfide used to separate lignin from the cellulose fibres needed for ...
The invention of the recovery boiler by G.H. Tomlinson in the early 1930s was a milestone in the advancement of the kraft process. [1] Recovery boilers are also used in the (less common) sulfite process of wood pulping; this article deals only with recovery boiler use in the kraft process.
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