What issues should be noted when purchasing pressure screening equipment for papermaking?

In the process of purchasing pressure screens for papermaking equipment, a comprehensive consideration should be made from five dimensions: technical parameter compatibility, equipment performance optimization, operational stability guarantee, maintenance convenience design, and economic assessment. The specific points to note are as follows:

I. Adaptability of technical parameters

Sieve hole/slit size: Selected based on the characteristics of the slurry. Waste paper pulp contains a lot of impurities, so a fine screen slit of 0.15-0.5mm (such as a long screen slit internal flow screen) should be used to improve the screening efficiency. Chemical pulp fibers are long, so a 1.3-2.5mm round hole sieve can be selected to balance output and quality.

Processing capacity matching: It needs to be determined in combination with the production scale. For instance, when the surface area of the 16-inch inner hole screen drum is 6.8 square meters, the maximum dry slurry processing capacity is 800 tons per day. If the daily processing demand is 1,200 tons of OCC slurry, then three 12-inch tail screens need to be configured.

Slurry feeding pressure and pressure difference control: The recommended slurry feeding pressure range is 0.18-0.35MPa, and it needs to be linked with the slag discharge device.

Ii. Optimization of Equipment Performance

Rotor configuration selection: High-frequency rotors (80-100Hz AC variable frequency motors) are suitable for high-precision screening. Single-arc rotors consume 25% less power than multi-stage ones.

The material and service life of the screen drum: The service life of the 304 stainless steel base is approximately 12 months. The composite screen plate with surface thermal spraying of tungsten carbide can extend the service period to 28 months. The choice should be based on the long-term cost.

Anti-clogging design: The internal flow pressure screen (such as the ZNL series) generates negative pressure pulses through the tangential entry of the slurry and the high-speed rotation of the rotor, which can automatically clean the screen drum to prevent clogging. The good slurry has a low pulse intensity and is suitable for direct feeding to the grid.

Iii. Guarantee of Operational Stability

Pressure and flow control: The pressure difference between the slurry inlet and outlet needs to be determined through experiments during production. If the pressure difference is too small, the slurry inlet pressure should be increased, but exceeding the limit will increase power consumption.

Slag discharge system design: A reverse pressure device should be installed on the tailings pipeline to ensure that the slurry fills the slurry screening machine. For instance, the tailings from the high-concentration screening machine should be discharged into the tailings pool at a higher position than the slurry inlet, or a flow control valve should be installed to prevent empty discharge.

Air management: When paper materials enter the pressure screen, they will form vortices. Air is prone to accumulate in the low-pressure area at the center and needs to be promptly removed to prevent flow fluctuations.

Four. Maintain convenient design

Replacement of vulnerable parts: Components such as screens and rotors should be easy to disassemble and replace.

Cleaning and anti-corrosion: Regularly clean the screen, inspect the transmission system and sealing performance, and do a good job in lubrication and anti-corrosion. For instance, stainless steel screen drums and thermal spraying of tungsten carbide technology are adopted to extend the service life of the equipment.

Safety design: During maintenance, it is necessary to ensure that the equipment is shut down and the power supply is cut off to prevent damage to personnel and equipment. For instance, install safety interlock devices to prevent accidents caused by misoperation.

V. Economic Assessment

Payback period: The payback period for new equipment is approximately 2.3 years. Long-term planning should be carried out in combination with production efficiency and cost. For instance, although the initial investment in high-concentration pressure screens is high, they can save water and power consumption, and have better long-term economic benefits.

Model capacity redundancy: 20% to 25% of the model capacity should be reserved to cope with the switching of different slurry types.

Maintenance and parts supply chain: Select a manufacturer that offers comprehensive maintenance services to ensure timely parts supply.