Why Dewatering Matters in Tissue Production

In tissue paper manufacturing, dewatering is the single most energy-intensive step. After stock preparation delivers a fiber suspension at approximately 0.1–0.5% consistency to the headbox, every subsequent stage—forming, pressing, and drying—must remove water efficiently. A poorly designed dewatering chain forces the dryer section to shoulder the burden, directly increasing steam consumption per ton of paper.

Production managers often see the symptoms first: rising steam costs, reduced machine speed, or sheet picking at the press. The root cause frequently traces back to inadequate dewatering in the forming or pressing sections. Addressing this systematically can yield double-digit percentage improvements in overall energy efficiency.

Stock Preparation: The First Line of Dewatering Optimization

Dewatering begins long before the paper machine. Fiber refining directly affects water retention. Over-refined fibers swell excessively, trapping water and slowing drainage on the wire. Under-refined fibers form a weak sheet that presses poorly. The sweet spot for tissue-grade refining is typically 25–35°SR freeness for virgin fiber and 30–40°SR for recycled furnish.

Leizhan’s disc refiner series operates with adjustable plate clearance, allowing operators to dial in the precise freeness target. Equipped with cast stainless steel refiner plates and a PLC-controlled gap adjustment system, these refiners maintain consistent treatment with no-load power below 15% of installed motor rating—a meaningful energy saving across 24/7 operation.

Forming Section Configuration

Modern tissue machines predominantly use crescent former or twin-wire configurations. The crescent former wraps the sheet around a forming roll, using centrifugal force to assist drainage. Key parameters include:

• Wire tension: 6–8 kN/m for standard tissue grades
• Forming roll vacuum: 15–25 kPa, adjusted for basis weight
• Headbox slice opening: 8–12 mm, with jet-to-wire ratio at 0.98–1.02

Leizhan supplies complete tissue machine forming sections with stainless steel frame construction and precision-ground forming rolls. The headbox features a tapered header design with tube bank distribution, ensuring cross-machine basis weight variation below ±1.5%.

Press Section: The Biggest Lever

Each percentage point of sheet dryness leaving the press section reduces dryer steam consumption by approximately 4–5%. A well-designed tissue press should achieve 40–44% dryness before the Yankee cylinder. Key equipment choices:

• Suction press roll: Single-felted configuration with 25–30 mm drilled shell, vacuum at 45–55 kPa
• Press loading: 80–120 kN/m for tissue, adjusted by grade
• Press felt selection: 1400–1600 g/m² with multi-layer base construction for optimal water handling

Leizhan’s suction press rolls are manufactured with a corrosion-resistant bronze or stainless steel shell and internal vacuum box with adjustable sealing strips. Bore diameter, hole pattern, and open area are engineered grade-specifically rather than using a one-size-fits-all design.

Yankee Dryer and Hood System

The Yankee cylinder represents the final thermal dewatering stage. Operating at 0.5–0.8 MPa steam pressure, a typical 3.6-meter diameter Yankee transfers approximately 150–180 kg H₂O/m²/h. Hood temperature and impingement velocity directly affect drying rate:

• High-temperature hood: 350–500°C impingement air
• Impingement velocity: 80–120 m/s
• Hood coverage: 220–270° wrap angle

Leizhan’s Yankee dryer cylinders are cast from high-grade gray iron (GG25–GG30) with a ground surface finish of Ra 0.2–0.4 μm, optimized for creping doctor blade performance and uniform heat transfer.

Practical Maintenance Tips

• Felt conditioning: Continuous high-pressure shower at 2.5–3.0 MPa on a 15–20 cm traverse cycle. Replace fan-type nozzles every 6 months.
• Press roll inspection: Check suction roll shell thickness with ultrasonic testing every 12 months. Drill hole plugging above 5% of total area calls for cleaning.
• Doctor blade change: Crepe doctor on Yankee should be changed every 4–6 hours of operation for consistent sheet release.
• Vacuum pump monitoring: Record vacuum level and seal water temperature daily. A 10% drop in vacuum often traces to seal water issues—not pump failure.

To discuss your tissue machine dewatering setup or explore Leizhan’s range of forming sections, press rolls, and Yankee dryers, reach out to our technical team directly.

Contact Leizhan for Your Paper Machinery Needs

Zhengzhou Leizhan Technology Paper Machinery Co., Ltd. supplies complete stock preparation systems and paper machine equipment for tissue, kraft liner, coating board, and corrugated medium production worldwide. For technical consultation or equipment inquiries, reach our team at:

📧 leizhanzhang@gmail.com