Pulp Cooking Process

Kraft cooking and pulp cooking equipments

In the papermaking industry, Kraft cooking or called chemical pulp cooking is a traditional method that converts wood chips or other fibrous sources into paper pulp. The chemical pulping method can produce high-quality papers because the Kraft cooking dissolves most of the lignin and hemicelluloses remained in the wood, resulting in better separation of the cellulose fibers. In a manner of speaking, Kraft cooking is the core step of the paper pulping process.

Anyang Machinery is a professional manufacturer of various types of pulp cooking equipment with more than 40 years of experience. With the most advanced processing equipments, Anyang Machinery can produce the complete set of pulp cooking equipments, including cooking digester, blow tank, vacuum pulp washer, replacement tanks with high quality. As a fixed-point production unit of SASAC, Anyang Machinery has produced 50-400 thousand tons of batch cooking, continuous cooking, and other conventional cooking systems since the 1980s, and provided equipment for entire production line for more than 60 papermaking enterprises from home and abroad. For the reliable quality of pulp cooking equipment and considerate after-sale service, we own a good reputation in the papermaking industry.

Flow chart of paper pulp cooking process

kraft cooking process

Types of Kraft cooking processes

According to the difference in working mechanisms, pulp cooking processes can be divided into two types, batch cooking process and continuous cooking process.

Batch cooking process

A Batch cooking plant typically comprises a number of 300 to 400 m³ digesters, two pressurized liquor accumulators, and three atmospheric tanks. In the digester, the cooking chemistry is on. Apart from the batch cooking operations, there are also continuous operations, such as heat transfer in the tank farm, fiber separation, condensate handling, and gas collecting.

The continuous batch cooking process is the latest technology for the manufacture of dissolving grade pulp according to the sulphate process. This discontinuous process has been optimized both from energy and steps. Furthermore, this process has been successfully solved the environmental problems, such as air (odor) and water pollution (prehydrolysate), commonly encountered in this field. Raw pulp produced by continuous batch cooking process features the highest quality in terms of bleachability and further processing. The process itself is characterized by the wide number of wood species that can be used.

Continuous cooking process

Continuous cooking process is the continuous process from feeding to discharging. It’s mainly used in alkaline pulping, nitrite cooking, prehydrolysis sulfate and sulfite cooking. Nowadays continuous cooking methods are widely applied to pulping processes for various materials. Including wood sawdust, annual plant, and agricultural and sideline products can be used, especially for those raw materials with loosing structure, easy penetration and non-wood fiber, such as bagasse, reed, wheat straw are more suitable for continuous cooking.

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