Lately, four pulp digesters of dual-phase steel for export to A pulp company in Brazil were delivered smoothly.
Material: dual-phase steel
Quantity: 4 sets
Weight: 240 tons
Application: pulping and papermaking industry
Processes of this steel fabrication: cutting, rolling, machining, welding, shaping, assembling, inspection, etc.
WHAT IS PULP DIGESTER?
Pulp digester, also called digester, is a huge container for chemical pulping and dissolved fiber steam sections. It is used to cook raw materials of paper pulp, such as grass, wood, boom, and so on. Pulp digester is not only applied for the kraft process but also the sulfite process. The raw materials of digester have carbon steel structure, composite steel structure, and dual-phase stainless steel due to the difference between alkaline pulping and acid pulping processes.
WORKING PRINCIPLE OF PULP DIGESTER
Before cooking, all raw materials must keep moisture content below 15 percent, silicon less than 3 percent, ash about 2-3 percent and cellulose about 50-55 percent.
First, cut the raw material into about 25 by 30mm slices and feed them into the cooker through the conveyor belt.
The requirements of pulping process usually determine the length of cooking process, in particular, the length of the cooking process depends on the yield and hardness of pulp. Cooking usually lasts 5-6 hours, during which cooking temperature should be kept at 160-175 ℃.
The heating process mainly refers to the indirect heating area of the tube heater. The liquid from the center flows through the tube and heats up and moves from the top to the bottom. Next, reheat the liquid about 8-12 times an hour. At the same time, the steam enters the auxiliary heating through the vent at the bottom.
In the course of cooking, gas is released through the upper vent to reduce the false pressure caused by the air inside the cooker, to ensure the pulp cooking uniformity and to improve the pulp quality.
After cooking, under pressure, remove the pulp from the cooker and enter the discharge tank for temporary storage.
Openex has rich experiences in pulp digester fabrication. we're also skilled in fabricating heavy ASME pressure vessels and boilers for customers.