Soda pulping
Encyclopedia
Soda pulping is a chemical process for making wood pulp
with sodium hydroxide as cooking chemical. In the Soda-AQ process, anthraquinone
(AQ) may be used as a pulping additive to decrease the carbohydrate degradation. The soda process gives pulp with lower tear strength than other chemical pulping processes (sulfite process
and kraft process
), but has still limited use for easy pulped materials like straw
s and some hardwood
s.
). The first mill was started in 1860 in the USA. In 1865 they patented a method for recovery of the cooking liquors by incineration of the spent liquor. Many of the early soda mills converted to kraft mills
once it was discovered.
production worldwide is produced from agricultural crops, valuing agricultural paper production at between $5 billion and $10 billion. The most notable of these agricultural crops are wheat straw and bagasse
. Using agriculatural crops rather than wood has the added advantage of reducing deforestation.
Due to the ease with which bagasse can be chemically pulped, bagasse requires less bleaching chemicals than wood pulp to achieve a bright, white sheet of paper.
Most chemical bagasse pulp mills concentrate the spent reaction chemicals and combust them to power the paper-mills and to recover the reaction chemicals.
es, bagasse
, bamboo
and some tropical hardwoods contain much silicate
s that may cause sodium aluminum silicate scale
s. Moderate amounts of silicates can be controlled with purging lime mud or lime kiln ash. Silicate removal from green liquor
in a soda mill can be achieved by lowering the pH
of the liquor with CO2
-containing flue gases from the lime kiln or other sources. No commercial silicate removal system is available for the kraft process
, but it can handle the small amounts of silicates from northern woods.
Wood pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...
with sodium hydroxide as cooking chemical. In the Soda-AQ process, anthraquinone
Anthraquinone
Anthraquinone, also called anthracenedione or dioxoanthracene is an aromatic organic compound with formula . Several isomers are possible, each of which can be viewed as a quinone derivative...
(AQ) may be used as a pulping additive to decrease the carbohydrate degradation. The soda process gives pulp with lower tear strength than other chemical pulping processes (sulfite process
Sulfite process
The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites , or bisulfites , depending on the pH...
and kraft process
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...
), but has still limited use for easy pulped materials like straw
Straw
Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain and chaff have been removed. Straw makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has many uses, including fuel, livestock bedding and fodder, thatching and...
s and some hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
s.
History
Soda pulping was one of the first chemical pulping methods and was invented in 1851 by Burgess (USA) and Watts (EnglandEngland
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
). The first mill was started in 1860 in the USA. In 1865 they patented a method for recovery of the cooking liquors by incineration of the spent liquor. Many of the early soda mills converted to kraft mills
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...
once it was discovered.
Production
Around 5%-10% of paperPaper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
production worldwide is produced from agricultural crops, valuing agricultural paper production at between $5 billion and $10 billion. The most notable of these agricultural crops are wheat straw and bagasse
Bagasse
Bagasse is the fibrous matter that remains after sugarcane or sorghum stalks are crushed to extract their juice. It is currently used as a biofuel and as a renewable resource in the manufacture of pulp and paper products and building materials....
. Using agriculatural crops rather than wood has the added advantage of reducing deforestation.
Due to the ease with which bagasse can be chemically pulped, bagasse requires less bleaching chemicals than wood pulp to achieve a bright, white sheet of paper.
Most chemical bagasse pulp mills concentrate the spent reaction chemicals and combust them to power the paper-mills and to recover the reaction chemicals.
Soda pulping as solution for silicate scaling
Many grassGrass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es, bagasse
Bagasse
Bagasse is the fibrous matter that remains after sugarcane or sorghum stalks are crushed to extract their juice. It is currently used as a biofuel and as a renewable resource in the manufacture of pulp and paper products and building materials....
, bamboo
Bamboo
Bamboo is a group of perennial evergreens in the true grass family Poaceae, subfamily Bambusoideae, tribe Bambuseae. Giant bamboos are the largest members of the grass family....
and some tropical hardwoods contain much silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
s that may cause sodium aluminum silicate scale
Fouling
Fouling refers to the accumulation of unwanted material on solid surfaces, most often in an aquatic environment. The fouling material can consist of either living organisms or a non-living substance...
s. Moderate amounts of silicates can be controlled with purging lime mud or lime kiln ash. Silicate removal from green liquor
Green liquor
Green liquor is the dissolved smelt of sodium carbonate and sodium sulfide from the recovery boiler in the kraft process. Although the color of such a solution is indeed green, no literature sources were found to explain what specific compounds are responsible for this color.The green liquor is...
in a soda mill can be achieved by lowering the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of the liquor with CO2
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
-containing flue gases from the lime kiln or other sources. No commercial silicate removal system is available for the kraft process
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...
, but it can handle the small amounts of silicates from northern woods.