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Wood pulp produced primarily by grinding wood is known as "mechanical pulp" and is used mainly for newsprint. These mechanical processes use fewer chemicals than either kraft or sulfite mills. The primary source of pollution from these mills is organic material such as resin acids released from the wood when it is processed.
Wood chipping is the act and industry of chipping wood for pulp, but also for other processed wood products and mulch. Only the heartwood and sapwood are useful for making pulp. Bark contains relatively few useful fibers and is removed and used as fuel to provide steam for use in the pulp mill. Most pulping processes require that the wood be ...
Mechanical pulping is the process in which wood is separated or defibrated mechanically into pulp for the paper industry.. The mechanical pulping processes use wood in the form of logs or chips that are mechanically processes, by grinding stones (from logs) or in refiners (from chips), to separate the fibers.
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.
Simply putting it, wood pulp is a large amount of individual wood fibres with the lignin removed. Wood pulp is naturally between dark brown to light grey in colour. Dark brown wood pulp is used for paper bags and boxes, and bleaching the pulp produces higher grades of paper (among other products). [9]
In pulp mills (like this one in Blankenstein, Germany) using the kraft or the sulfite process, lignin is removed from lignocellulose to yield pulp for papermaking. Global commercial production of lignin is a consequence of papermaking. In 1988, more than 220 million tons of paper were produced worldwide. [21]
Oct. 28—Neighbors of a paper pulp mill in Old Town are raising a stink about a foul, rotten-egg smell they say it's been releasing — and now some are suing the mill's owner over the odor.
The black liquor contains more than half of the energy content of the wood fed into the digester of a kraft pulp mill. [11] It is normally concentrated to 65 - 80% by multi-effect evaporators and burned in a recovery boiler to produce energy and recover the cooking chemicals. The viscosity increases as the concentration goes up.