Process Stages in Pulping and Papermaking and Their Functions

Pulping Stage:

Raw material selection → Cooking and fiber separation → Washing → Bleaching → Washing and screening → Concentrating or forming pulp sheets → Storage for later use

Papermaking Stage:

Pulp dispersion → Impurity removal → Refining → Beating → Adding various additives → Mixing pulp → Pulp transportation → Headbox → Forming section → Pressing section → Drying section → Surface sizing → Drying → Calendering → Winding into paper rolls

Coating Stage:

Coating the base paper → Coating machine → Drying → Winding → Rewinding → Supercalendering

Finishing Stage:

Rewinding → Cutting into sheets (or rolls) → Sorting and packaging → Warehousing and completion

Modern papermaking processes can be divided into main steps such as pulping, formulation, papermaking, and finishing.

1.Pulping Process:

Pulping is the first step in papermaking. Common methods to convert wood into pulp include mechanical pulping, chemical pulping, and semi-chemical pulping.

2.Formulation Process:

The formulation of the paper pulp is another key stage in papermaking, as it directly affects the strength, tone, printability, and shelf life of the paper after it is made.

The typical formulation process can be broken down into three steps:

• a. Pulp dispersion
• b. Beating
• c. Adding sizing and fillers

3.Papermaking Process:

The primary task in the papermaking department is to take diluted pulp and evenly interlace and dewater it. After that, it is dried, calendered, wound into rolls, cut, sorted, and packaged. The general process flow is as follows:

a. Pulp Screening:

The formulated pulp is diluted to a lower concentration, and impurities and undissolved fiber bundles are removed using screening equipment to maintain quality and protect equipment.

b. Forming Section:

The pulp is transferred from the headbox onto a circulating copper wire or plastic mesh, where it is evenly distributed and interwoven.

c. Pressing Section:

The wet paper is moved between two rollers covered with felt, where the pressure from the rollers and the water absorption of the felt further dewaters the paper, compacting it to improve its surface and increase its strength.

d. Calendering:

After pressing, the moisture content of the paper is still 52–70%. At this point, mechanical methods are no longer effective for removing the water, so the paper is passed over multiple heated cylinders to dry it.

e. Winding:

After pressing, the moisture content remains at 52–70%, so the paper is dried by passing it over cylinders with steam inside.

f. Cutting and Sorting:

The paper rolls that have been wound are cut into sheets using a cutting machine. These sheets are then sorted by hand or mechanically to remove damaged or soiled sheets. Finally, every 500 sheets are packaged into one ream (commonly known as one "ream").

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