What is the Difference Between Kraft and Sulfite Pulping?

The key difference between kraft and sulfite pulping lies in the chemicals used in the cooking liquor and the resulting fibers. Here are the main differences between the two processes:

1. Chemicals used: Kraft pulping involves the treatment of wood chips with a hot mixture of water, sodium hydroxide, and sodium sulfide, while sulfite pulping involves the treatment of wood chips with calcium, potassium, magnesium, or ammonium.
2. Cooking liquor: The cooking liquor in kraft pulping is alkaline, which is less corrosive to iron and steel, while the cooking liquor in sulfite pulping is acidic.
3. Fiber strength: Kraft pulping produces stronger fibers than sulfite pulping.
4. Environmental impact: Sulfite pulping is considered more environmentally friendly than kraft pulping.
5. Pulp yield: The yield of pulp based on wood used is higher for sulfite pulping than for kraft pulping.
6. Pulp applications: Sulfite pulp is used to make fine paper, tissue, glassine, and to add strength to newsprint, while kraft pulp is used in a variety of applications, including paper and board production.

In summary, kraft pulping uses an alkaline cooking liquor and produces stronger fibers, while sulfite pulping uses an acidic cooking liquor and is more environmentally friendly. The choice of pulping process depends on the desired fiber properties and the specific application of the pulp.

Comparative Table: Kraft vs Sulfite Pulping

The key difference between kraft and sulfite pulping lies in the chemicals used in the process. Kraft pulping involves the treatment of wood chips with sodium hydroxide and sodium sulfide, while sulfite pulping involves the treatment of wood chips with calcium, potassium, magnesium, or ammonium. Here is a comparison of the two processes:

Both kraft and sulfite pulping processes are used to extract cellulose from wood by dissolving the lignin that binds the cellulose fibers together. The choice of pulping process depends on the desired properties of the final product, such as strength and purity.