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A precursor to the soda pulping process was the paper making process developed by Matthias Koops in 1801 which involved washing wood shavings in limewater, adding soda crystals and then boiling the mixture. [2] Soda pulping was one of the first chemical pulping methods and was invented in 1851 by Burgess (United States) and Watts (England).
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 (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 pulp is used for materials that need to be stronger or combined with mechanical pulps to give a product different characteristics. The kraft process is the dominant chemical pulping method, with the sulfite process second. Historically soda pulping was the first successful chemical pulping method.
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 .
During the 19th and 20th centuries, the paper chemical technologies for making the pulp from wood rather than grasses underwent some major industrial-era upgrades, as first the soda pulping process and then the Kraft process helped reduce the unit cost of paper manufacture.
In the kraft process the pulping chemicals are sodium hydroxide and sodium sulfide and the solution is known as white liquor. In the sulfite process the pulping chemical is a mixture of metal (sodium, magnesium, potassium, or calcium) and ammonium sulfite or sulfite.
The most common technical lignins include lignosulphonates (isolated from sulfite pulping), kraft lignins (isolated from kraft pulping black liquor), organosolv lignins (isolated from organosolv pulping), soda lignins (isolated from soda pulping) and lignin residue after enzymatic treatment of biomass.