Kraftpulpissa

Kraftpulpissa is a term that refers to pulp produced using the kraft process, also known as the sulfate process. This method is the most common chemical pulping process globally, used to produce the vast majority of wood pulp for paper manufacturing. The kraft process involves breaking down wood chips into cellulose fibers using a strong alkaline solution, typically composed of sodium hydroxide and sodium sulfide. This solution is heated under pressure in a digester.

The chemicals in the pulping liquor dissolve the lignin, a complex polymer that binds the cellulose fibers together in wood, while largely preserving the strength of the cellulose fibers themselves. This results in a pulp that is stronger and more durable than that produced by other methods, such as the sulfite process. The kraft process is particularly effective for pulping a wide variety of wood species, including hardwoods and softwoods.

A key advantage of the kraft process is its chemical recovery system. The spent pulping liquor, known as black liquor, contains dissolved lignin and inorganic chemicals. This black liquor is concentrated and then burned in a recovery boiler. This combustion process recovers much of the chemical value and generates steam for energy production, making the kraft process relatively self-sufficient and environmentally more sustainable than older methods. The inorganic chemicals are also recovered and reused in the pulping process, reducing the need for fresh chemical makeup. Kraft pulp is widely used for packaging, printing and writing papers, tissue, and other paper products.