Equipment Description:Chemical Pulping
To print this FactSheet click here To return to the FactSheet home page click here
Chemical Pulping breaks down the raw material (wood) into individual fibres by dissolving the lignin that holds the fibres together. There are two main processes in Chemical Pulping. These are Sulphate and Sulphite Pulping. The Sulphate process produces pulp of high strength and bulk but a generally gives a poor sheet formation. The pulp is used for products such as linerboard and food packaging board. Sulphite pulping provides pulp of lower strength and bulk but with better formation properties. This pulp is used for products such as MG paper with a high gloss finish. |
Sulphate A Chemical pulping process using Sulphate, often known as the kraft pulping process. Sulphite A Chemical pulping process using sulphite. Lignin A complex chemical substance that bonds wood fibres together. |
 Image courtesy of Metso |
In the Sulphate process, chemicals and chips are charged into a digester and cooked for approximately 2-4 hours at around 170 deg Celsius depending on the lignin to be removed. For each ton of pulp produced about 3000-5000 gallons of residual fluid called black liquor is produced and washed from the pulp during the process. This residue contains dissolved wood components (organics) and inactive cooking chemicals (inorganics). This residue goes through a recovery process. The organic component is burnt off to generate heat energy. The inorganics are re-activated to be re-used again. The pulp can then be bleached to attack and remove the remaining lignin and to strip the colour from the fibres and any dirt to improve brightness. The Sulphite process is similar to that of Sulphate Pulping except that sulfurous acid and an alkali is used to break down the lignin bonds. The yield of chemical pulping is about 45% but a high brightness can be achieved and much of the remaining wood material can be burnt to produce steam and electrical energy. |
Chemical Pulping was also mentioned in the following Fact Sheets (40):
|
(This information is from suppliers listed in the Industry Directory. Contact PITA to have your company listed here) There are 4 other potential suppliers of relevant equipment/services. (This information is from suppliers listed in the Industry Directory Contact PITA to have your company listed here)
|