Digester Types

The purpose of kraft pulping is to separate fibers from each other so that they can be used to produce paper and other cellulose fiber based products. This type of chemical pulping is accomplished by cooking wood chips in a chemical solution in large pressure vessels called digesters. Pulping can be performed in digesters running in batch or continuous mode. This module describes the advantages and disadvantages of different types of digesters, including: batch systems, continuous cooking systems with one and two vessels, continuous digesters which are hydraulically filled and those which utilize a vapor phase. Pandia and M&D digesters are also described.

• Describe the purpose of kraft pulping • List typical configurations of continuous digester systems • Describe the major steps involved in batch cooking • Describe the advantages of continuous digesters • Identify the advantages of vapor phase continuous digester systems • Describe the advantages of two-vessel continuous digester systems • Identify the unique feature that the M&D and Pandia digesters share • Identify the primary use of M&D digesters