Water Treatment Equipment for Papermaking Industry

In papermaking production, raw water and circulating water are two core water sources. There are significant differences in their sources, uses, water quality requirements, and treatment logics, and together they support the stable operation of papermaking processes and the efficient utilization of water resources.

Raw water is a general term for the fresh water required in papermaking production, mainly sourced from natural water bodies (e.g., rivers, groundwater) or municipal water supplies. It must undergo targeted pretreatment to meet the water quality standards for various papermaking processes (such as pulping, papermaking, and auxiliary material preparation) before entering the production system.

Circulating water refers to "low-pollution wastewater" generated during papermaking (e.g., papermaking white water, equipment cooling water, and light washing water). After physical and chemical treatment, it is reused in the original process or other processes with lower water quality requirements, forming a "water use - treatment - reuse" circulation system.

In papermaking water treatment, raw water pretreatment equipment and circulating water treatment equipment (among others) ensure that the inlet water quality meets standards during papermaking production, improve the recycling rate of water resources, and reduce production costs and environmental impacts. The main types are as follows:

I. Raw Water Pretreatment Equipment (for Fresh Water Sources)

Raw water pretreatment involves treating natural water sources (e.g., river water, groundwater, tap water) to meet the water quality standards for papermaking production (e.g., requirements for pulping and papermaking processes). Its primary goal is to remove impurities such as suspended solids, colloids, hardness, organic matter, and microorganisms.

1. Multi-Media Filter

Composed of multiple filter media (e.g., quartz sand, anthracite, manganese sand), it removes suspended solids, sediment, and colloidal particles from water through multi-layer filtration, reducing water turbidity and laying the foundation for subsequent treatment. It is commonly used for initial raw water purification to protect subsequent precision treatment equipment.

2. Activated Carbon Filter

Utilizing the adsorption capacity of activated carbon, it removes organic matter, odors, color, and residual chlorine from water. It is particularly suitable for treating raw water with high organic content, improving water purity and preventing adverse effects on paper quality (e.g., color spots and odors).

3. Softening Equipment (Ion Exchanger)

Removes hardness-causing components (e.g., calcium and magnesium ions) from water to prevent scaling in papermaking equipment (e.g., boilers, pipelines, paper machines), which could otherwise reduce heat transfer efficiency or cause paper quality issues (e.g., increased brittleness of paper sheets due to hard water). Common types include sodium ion exchangers and cation-anion exchangers.

4. Ultrafiltration (UF) Equipment

Uses UF membranes to retain macromolecular organic matter, colloids, bacteria, and viruses, further purifying water. The effluent has low turbidity and meets microbial standards, serving as pretreatment for subsequent reverse osmosis (RO) treatment or directly for papermaking processes with relatively low water quality requirements.

5. Precision Filter (Security Filter)

As terminal filtration equipment, it removes residual fine particles (typically with a filtration precision of 5-20μm) to protect subsequent membrane modules (e.g., RO membranes) or precision equipment from contamination and clogging, ensuring stable system operation.

II. Circulating Water Treatment Equipment (for Water Reuse in Production)

A large amount of water used in papermaking (e.g., papermaking white water, washing water) can be reused after circulation treatment, reducing fresh water consumption and wastewater discharge. Circulating water treatment equipment mainly addresses issues such as scaling, corrosion, and microbial growth in circulating water.

1. Cooling Tower

Reduces the temperature of circulating water. Since water temperature rises after use in papermaking equipment (e.g., the press section and drying section of paper machines), cooling towers lower the water temperature to the process-required range through evaporative heat dissipation or air heat exchange, ensuring the cooling effect of circulating water.

2. Side Stream Filtration Equipment

Side stream filters are installed in the circulating water system to remove suspended solids, fiber debris, and microbial slime, controlling the turbidity of circulating water and reducing the risk of equipment/pipeline clogging and scaling. Common types include sand filters and self-cleaning filters.

3. Corrosion and Scale Inhibition Equipment

Inhibits metal corrosion and the formation of scales (e.g., calcium carbonate, calcium sulfate) in circulating water by adding corrosion inhibitors, scale inhibitors, or using electrochemical methods. This protects the service life of paper machines, pipelines, and other equipment.

4. Sterilization and Algae Removal Equipment

Circulating water in high-temperature and high-humidity environments is prone to algae growth, bacterial propagation (e.g., Legionella), and microbial slime formation. Common equipment includes ultraviolet (UV) sterilizers, ozone generators, and chemical dosing devices (for adding bactericides) to prevent equipment corrosion or paper contamination caused by microbial pollution.

5. White Water Recovery Equipment

Specifically designed to treat papermaking white water (wastewater containing fine fibers and fillers generated during papermaking). It recovers fibers and clean water through air flotation, filtration, and sedimentation. The recovered fibers can be reused in the pulping system, while the clean water is used for wire washing and dilution. This significantly improves the utilization rates of water resources and raw materials.

Together with wastewater treatment equipment, these devices form a complete water treatment system for the papermaking industry. Covering raw water purification, water circulation in production, and up-to-standard wastewater discharge or advanced reuse, the system achieves the dual goals of efficient water resource utilization and compliance with environmental protection requirements.