Operational Principle of Conventional Cooking Digester Room
Cooking digesters are mainly applied to pulp cooking through the use of raw materials such as wood or bamboo with less than 15% moisture content, 2%-3% ash content, 50%-55% cellulose content, 22%-25% lignin content and less than 3% Si content. After being cut into the slices (25mm-30mm), raw materials will be sent to the digester with full of cooking liquor and steam through a conveyor belt. The cooking process will take 5.5-6 hours at the temperature of 160℃-175℃ to make. The time span depends on the pulping demand (Pulp yield and hardness). The heating process occurs mainly in the effective indirect heating area where tubular heater works. Liquid out from the center flows through a circular tube whilst is heated and transmitted from up to down, which shall be circularly carried out for about 8-12 times an hour. Meantime the steam from the vent at the bottom will help do auxiliary heating. During the cooking process gas is expelled out from the vent at the top to reduce the fake pressure phenomenon caused by the air in the inner digester, which is conducive to keep the uniform of pulp cooking and improve the pulp quality. After the cooking process, through the blow valve, the pulp under pressure will be out of the digester and enter the flat discharge pan where it will be stored temporarily.
Specification of Conventional Pulp Cooking Digesters
|Design pressure （Mpa）||0.9/1.2|
|Design temperature （℃）||180/240|
Self-contained Complete Tanks And Heat Exchanger
|Tank region||Cold black liquor tank, warm black liquor tank, hot black liquor tank, cold white liquor tank|
|Heat exchanger||Warm black liquor cooler, black/white liquor exchanger, white liquor heater, steam distributor, cyclone separator|