With today’s increasingly high energy and chemical costs and stringent environmental regulations, the need for improved recovery of chemicals from the pulp and paper making process has become a critical economic factor in the industry. It is essential that mills maximize steam and power production capacity, reduce recirculating chemical dead loads, and minimize chemical losses. Paper is an essential outcome from the forest industry, used in various forms and shapes. This different form of paper is made by pulping of the wood, bleaching the pulped wood, spreading these bleached pulps into sheets ultimately converting it to paper. With different stages of designing the paper, various chemicals are used to give the paper its present properties, such as the bleaching chemicals that make paper white (and which also enable it to subsequently be colored). Sulfate or Kraft pulping is the main pulping process was invented in Germany in 1884 and remains the dominating technology today. Kraft pulping usually relies on a combination of heat, chemicals and mechanical pulping to convert the wood into a smooth, soft pulp suitable for use in papermaking.
Functions of Kraft pulping process
- Minimizing the environmental impact of waste material (black liquor) from the pulping process.
- Recycling pulping chemicals, NaOH and Na2S;
- Co-generating steam and power.
Advantages for Chemical Recovery Process:
- It can be used with virtually all wood species.
- It can easily handle the extractives in most coniferous wood
- The pulp has very good strength.
- The recovery process for the chemicals is well established.
- More effective at removing impurities like resins.