Overview of Modern Kraft Liner Production Technology

Kraft linerboard remains the backbone of the global packaging industry, with demand growing steadily across developed and emerging markets. A well-engineered kraft liner production line integrates stock preparation, paper machine, and finishing sections into a cohesive system that maximizes output while minimizing operational costs.

The complete production process begins with waste paper handling—OCC (old corrugated containers) and kraft cuttings are fed into a hydraulic pulper for initial defibering. The pulp then passes through high-density cleaners to remove heavy contaminants, followed by pressure screens for fine screening at 0.15-0.35mm slot sizes. Medium-consistency cleaning and fractionation ensure uniform fiber quality before the pulp reaches the paper machine headbox.

Key Equipment Specifications for 200-600 TPD Lines

For mills targeting 200 to 600 tons per day of kraft liner production, the following equipment configurations deliver optimal performance:

Stock Preparation Section

• Hydraulic Pulper: D-type design, 132-500 kW motor, pulping consistency 4-6%, batch cycle 15-20 minutes
• High-Density Cleaner: 3-4 stage cascade, inlet consistency 3-4%, reject rate less than 8%
• Pressure Screen: 0.15-0.35mm screen basket slots, 2-stage screening, fiber recovery above 95%
• Double Disc Refiner: 660-910mm disc diameter, 250-900 kW, freeness reduction 8-12 °SR per pass
• Disc Thickener: Inlet 0.8-1.2%, outlet 8-12%, filtrate clarity below 0.05%

Paper Machine Section

• Wire Width: 3200-4800mm depending on capacity target
• Basis Weight Range: 90-250 gsm
• Design Speed: 350-500 m/min
• Headbox Consistency: 0.5-0.8%
• Press Section: 3-nip configuration, dryness after press 46-48%
• Dryer Cylinders: 36-48 cylinders, 1800mm diameter, steam pressure 0.3-0.6 MPa

Energy Consumption and Operating Efficiency

Energy represents one of the largest operational costs in kraft liner production. Modern line configurations achieve the following benchmarks:

• Stock Preparation Power: 80-120 kWh per ton of pulp
• Paper Machine Power: 280-320 kWh per ton of paper
• Steam Consumption: 1.6-1.8 tons per ton of paper (with closed hood)
• Water Usage: 8-12 m³ per ton (with closed-loop recycling)

Compared to older configurations, these figures represent a 15-20% reduction in specific energy consumption, achieved through optimized rotor designs, improved heat recovery systems, and variable-frequency drives on major motors.

Maintenance Schedule for Long-Term Reliability

Preventive maintenance is essential for maintaining production efficiency and avoiding unplanned downtime:

• Daily: Check lubrication oil levels, inspect doctor blade contact on all dryer cylinders, verify vacuum pump seal water flow, monitor bearing temperatures (should not exceed 70°C)
• Weekly: Inspect wire tension and tracking, check felt guiding systems, verify steam trap operation, examine rope threading system
• Monthly: Calibrate basis weight and moisture sensors, check gearbox oil quality, inspect suction roll shell, verify refiner plate gap settings
• Quarterly: Replace doctor blades, inspect felt and wire guide roll bearings, check refiner plate wear (replace when groove depth below 3mm), examine screen basket for wear
• Annual Shutdown (5-7 days): Complete dryer cylinder inspection, gearbox overhaul, roll bearing replacement, headbox cleaning and nozzle inspection, complete screen basket and rotor replacement if needed

Quality Control Parameters for Kraft Liner

Consistent product quality requires monitoring these key parameters throughout production:

• Burst Index: 3.0-4.5 kPa·m²/g (depending on basis weight)
• Ring Crush Test (RCT): 1.5-2.5 kN/m
• STFI Short Span Compression: 4.0-6.5 kN/m for 150 gsm
• Moisture Content: 7-9% at reel
• Caliper Variation: Within ±3% across the web

Zhengzhou Leizhan Technology provides complete kraft liner production line engineering, equipment manufacturing, and commissioning services. Each project includes installation supervision and operator training to ensure smooth startup and sustained performance.

Contact us for a detailed proposal: leizhanzhang@gmail.com

Zhengzhou Leizhan Technology Paper Machinery Co., Ltd.