The Kraft process in paper mill, also known as Kraft Pulping, is a process of efficiently converting wood into wood pulp. The Kraft pulping process is a vital method in paper production known for its ability to produce high-quality paper.
Chemical Process in Kraft Pulping
Kraft process in paper mill involves the use of chemicals, specifically sodium hydroxide and sodium sulfide. These chemicals break down lignin, the substance that binds wood fibers together. The removal of lignin results in a pulp that is easier to bleach and refine.
Steps of Forming Kraft Pulp
Wood Preparation / Debarking
The formation of kraft pulp begins with preparation of wood. The logs are processed through a debarking machine followed by a chipper to get the logs debarked and then chopped into small pieces. These chips are further screened to get uniform chips for further process.
Cooking
After processing the wood chips from screening, they are passed for the cooking step. The wood chips are cooked in a digester with a chemical solution to break down the lignin.
Washing and Screening
The pulp is washed to remove dissolved lignin and other impurities. It is then screened to separate any remaining wood chips.
Bleaching
If the pulp or final product requires white color, bleaching is carried out with chemical additives.
Refining
The bleached pulp is refined to improve fiber bonding and achieve the required strength for quality paper products.
Environmental Benefits
Modern Kraft mills are designed to minimize emissions and energy consumption, contributing to sustainable paper production. The recovery and reuse of chemicals reduce waste significantly.
