Displacement cooking digesters

Operational principal of displacement pulp cooking

Displacement cooking is that used cooking liquor is displaced by cooking liquor or washing water using the principles of displacement cycle and diffusion washing of black liquor in the batch digester. Both used cooking liquor and heat are displaced, and then cold spraying is fulfilled. Displacement cooking can make full use of the black liquor repeatedly, extract lignin from the cooking system in delignification phase and dissolve hemi-cellulose. During the supplementary delignification phase, cooking liquor can be refilled. By the principles, initial heat and chemicals can be recycled. The cooking can keep continuous balance during the whole cooking process, which can help to improve pulp quality and production efficiency.

Advantages of displacement cooking technology

Displacement cooking technology is the most advanced batch cooking technology in the world nowadays. Compared with conventional cooking, it has the following advantages:

• Per-ton pulp of steam consumption is reduced greatly to 0.6-0.8t (Conventional consumption is 2.0-2.5t).
• It can achieve low Kappa number, high strength and high yield pulp through deep delignification.
• Pulp has gotten better bleaching. Its low Kappa number and high strength are conducive to oxygen delignification, reduction of consumption of chemicals for bleaching and reduction of pollution.
• Production process is controlled by microcomputer, which reduces manual operation as much as possible and keeps the system reliable and stable.

Parameter of displacement cooking equipments