Kraftpulppa

Kraftpulppa is a Swedish term that translates to "kraft pulp" in English. It refers to a type of chemical wood pulp produced by the kraft process, also known as the sulfate process. This process involves digesting wood chips with a solution of sodium hydroxide and sodium sulfide at high temperature and pressure.

The kraft process is the most widely used method for producing wood pulp worldwide due to its efficiency and the strength of the resulting pulp. Kraft pulp fibers are known for their long length and high tensile strength, making them ideal for applications requiring durability, such as paper bags, packaging materials, and high-quality printing paper. The process breaks down lignin, a complex polymer that binds cellulose fibers together in wood, allowing for the separation of these fibers.

A key characteristic of the kraft process is its recovery system, which recycles most of the chemicals used in cooking and generates energy from the organic byproducts. This makes the process more environmentally friendly and cost-effective compared to older pulping methods. The pulping liquor, after separating the pulp, is concentrated and burned in a recovery boiler. This burns off the organic residues and recovers inorganic chemicals that can be reused.

Kraft pulp can be produced from various types of wood, including softwoods like pine and spruce, and hardwoods like birch and eucalyptus. The choice of wood influences the properties of the final pulp. Softwood kraft pulp generally has longer fibers, contributing to greater strength, while hardwood kraft pulp has shorter fibers, resulting in a smoother and more opaque paper. The unbleached pulp is brown in color, and it can be further treated with bleaching chemicals to produce white pulp.