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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.
In the sulfite process the pulping chemical is a mixture of metal (sodium, magnesium, potassium, or calcium) and ammonium sulfite or sulfite. After several hours in the digester, the chips or cut plant material breaks down into a thick porridge-like consistency and is "blown" or squeezed from the outlet of the digester through an airlock.
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 ...
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 ...
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 ...
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 ...
Data suggests that around 5% of people with asthma also have a sulfite sensitivity. Symptoms include wheezing, shortness of breath, chest tightness, coughing, sneezing, a stuffy or runny nose, and ...
Chemical pulps, such as those from the kraft process or sulfite pulping, contain much less lignin than mechanical pulps, (<5% compared to approximately 40%). The goal in bleaching chemical pulps is to remove essentially all of the residual lignin, hence the process is often referred to as delignification.