Chips from the storage silo are loaded into the digester, where it is cooked with cooking liquor (Caustic Soda) at a Temperature of 170-175 Deg. C & Pressure of around 9 kg/cm2. The cooking is carried out by an Indirect heating process to remove lignin & other organic compounds. After attaining a desired pressure & temperature, It is kept at the same pressure & temp. for 2 hours. Then, the whole mass is blown to the Blow tank under pressure. The Vapors coming out of the blow tank are utilized to heat the water in the blowing heat recovery system.

Vertical Stationary Diester With Preheater:

Digester has got cylindrical portion in the center & a conical shape at the bottom & top end. It has got screen plates at the top, middle & bottom. Material of Construction of digester is SA 516 Gr. 70 & the thickness is approx. 36 mm. The designed pressure is 10.5 kg/cm2 & test pressure is 16.5 kg/cm2. The screen plates MOC are AISI 304. Digester body has got connection for putting liquor in the center & discharge at the top & bottom. Blow line to the digester is connected at the bottom, from where the complete mass is blown after the cooking cycle completes.

As the cooking process is carried out by Indirect heating method, Digesters are connected with Liquor Preheater- where the steam is injected at the outer body of the preheater & the liquor is circulated in the preheater through liquor circulation pumps in the tubes of the preheaters.

Blow Heat Recovery System:

Blow Heat recovery system is installed to condense the contaminated vapors originating from the blow tank during blowing of pulp from the Digesters. The water from the Accumulator tank is circulated to condense these vapors & raise the water temperature. This hot water is used to heat the fresh water from ambient Temperature to 70 Deg. C in plate type or Tube type heat exchanger. The heated fresh water is used in washing section.