The purpose of cooking agro raw material is to chemically dissolve lignin and other organic compounds to obtain unbleached pulp. This process is carried out in a horizontal continuous tube digester at a temperature of 160°C and a pressure of 6.5-7 kg/cm². The main components of the digester system include:

• Screw Feeder
• Inlet Chamber with Stop Valve
• Digester Tubes
• Cold Blow Discharger
• Blow House

The washed raw material from the aqua separator is conveyed by a belt conveyor to the metering screw conveyor in the digester house. Bagasse from the metering screw conveyor is fed to the pin feeder, and any excess raw material is returned to the wet washing plant.

In the pin feeder, the raw material is fed to the screw feeder to form a compact mass before entering the inlet chamber.

Cooking chemicals and steam are introduced at the inlet chamber, where they mix with the raw material before entering the digester tubes. A pneumatically operated blowback valve is provided in the inlet chamber to prevent the raw material from blowing back in case of improper feeding before the digester tubes.

The digester consists of two horizontal tubes equipped with screw conveyors, which convey the material from the first tube to the second tube. Steam is injected into the first tube to control temperature and pressure. The speed of the screw in the digester tube is maintained to achieve the desired Kappa number.

The cooked raw material, or pulp, is blown to the cold blow discharger, where cold black liquor is injected. From the cold blow discharger, the pulp is blown to the blow tank, which acts as a storage unit for the cooked pulp.