Detailed Explanation of KDP Plate Heat Exchangers in the Pulp and Paper Industry

Detailed Explanation of KDP Plate Heat Exchangers in the Pulp and Paper Industry

图片5.png

Key Processes in the Pulp and Paper Industry and Applications of KDP Plate Heat Exchangers (PHEs)

The paper production process primarily includes pulping, bleaching, papermaking, coating, and wastewater treatment. Plate heat exchangers play a vital role in the following core processes:

Pulping Process

Black Liquor Evaporation

Process Requirement:

Black liquor (containing lignin and alkali) after pulping needs to be concentrated from 15% to 60–80% for alkali recovery through combustion.

PHE Application:

Used in multi-effect evaporation systems as heaters, where steam (120–150°C) heats the black liquor.

Advantage:High heat transfer efficiency (3× higher than shell-and-tube exchangers), reduced scaling risk (turbulent flow design).

Material Selection:

Plates: 316L stainless steel (alkali-resistant), titanium (Ti), or 254SMO super stainless steel (chloride-resistant).

Gaskets: EPDM (resistant to high-temperature alkali) or FKM (fluorocarbon rubber, resistant to organic solvents).

Chip Heating

Process Requirement:

Wood chips must be preheated to 70–90°C to soften fibers.

PHE Application:

Utilizes waste heat (e.g., steam condensate) to heat process water, significantly saving energy.

Bleaching Process

Bleaching Chemical Heating (ClO₂, H₂O₂, NaOH Solutions)

Process Requirement:

Bleaching agents must react at 50–80°C for higher efficiency.

PHE Application:

Titanium plates are used to resist ClO₂ corrosion, avoiding weld corrosion issues in shell-and-tube exchangers.

Material Selection:

Plates: Titanium (Ti) or Hastelloy C-276 (resistant to strong oxidizers).

Gaskets: PTFE (Teflon®, resistant to all bleaching chemicals).

Paper Machine Dryer Section

Hot Air System

Process Requirement:

Drying paper requires 100–200°C hot air, traditionally generated by gas heating. PHEs can recover waste heat.

PHE Application:

Recovers heat from exhaust gas to preheat fresh air (energy savings >30%).

Material Selection:

Plates: 304 stainless steel (cost-effective) or aluminized steel (high-temperature oxidation-resistant).

Gaskets: Silicone rubber (resistant to 200°C).

Coating Process

Coating Color Temperature Control

Process Requirement:

Coating must be maintained at 40–60°C for uniform viscosity.

PHE Application:

Dual PHE system: one side heats (steam), the other cools (water) for precise temperature control.

Material Selection:

Plates: 316L stainless steel (resistant to pigment abrasion).

Gaskets: NBR (nitrile rubber, resistant to mineral oil-based coatings).

Wastewater Treatment

Anaerobic Digestion

Process Requirement:

Wastewater must be maintained at 35–55°C to promote microbial degradation.

PHE Application:

Uses PHEs to heat wastewater, with heat sourced from biogas boiler waste heat.

Material Selection:

Plates: 2205 duplex stainless steel (resistant to hydrogen sulfide corrosion).

Gaskets: EPDM (resistant to weak acids/alkalis).

Guidelines for KDP 's Plate and Gasket Selection

Plate Material Selection

Medium TypeRecommended MaterialApplication Scenario
Black liquor, alkali316L stainless steel, 254SMOPulp evaporation systems
Chlorine bleach (ClO₂)Titanium (Ti), Hastelloy C-276Bleaching section
High-temperature exhaust gasAluminized steel, 304 stainlessDryer section heat recovery
High-sulfur wastewater2205 duplex stainlessWastewater treatment

Gasket Selection

Medium/EnvironmentRecommended GasketTemperature/Chemical Resistance
High-temperature alkali (pH>10)EPDMResists 150°C, NaOH
Organic solvent coatingsNBRResists mineral oils, ≤100°C
Strong oxidizers (ClO₂)PTFEResists all chemicals, ≤180°C
High-temperature exhaust gasSilicone rubberResists 200°C, oxidation

KDP's Advantages Over Other Heat Exchangers

Comparison DimensionPlate Heat Exchanger (PHE)Shell-and-Tube Heat ExchangerSpiral Plate Heat Exchanger
Heat Transfer EfficiencyUltra-high (K-value up to 6000 W/m²·K), narrow flow channelsLow (K-value ~1000–2000)Moderate (K-value ~3000–4000)
Fouling RiskTurbulent flow reduces fouling, easy cleaningLaminar flow promotes fouling, requires mechanical cleaningModerate, but difficult to clean
FootprintCompact (80% smaller than shell-and-tube)BulkyModerate
Maintenance CostOnly gasket replacement, plates last >10 yearsPeriodic tube bundle replacement, costlyWelded structure, difficult to repair
Corrosion ResistanceOptional high-end materials (Ti, Hastelloy)Relies on expensive liningsLimited material options (usually stainless steel)
Temperature/PressureSuitable for ≤180°C, ≤2.5 MPa (welded models can handle higher)Handles high temp/pressure (≤400°C, 10 MPa)Medium temp/pressure (≤250°C, 4 MPa) | 

KDP Case Studies

A Finnish Pulp Mill:

Adopted all-titanium PHEs for ClO₂ bleaching, achieving a 15-year service life, whereas shell-and-tube exchangers corroded within 5 years.

A Chinese Packaging Paper Mill:

Used 316L stainless steel PHEs in coating, achieving ±1°C temperature control and improving product quality consistency by 20%.

图片10 - 副本.png

Summary

Plate heat exchangers are the preferred choice in the pulp and paper industry for pulping, bleaching, drying, and coating due to their high efficiency, corrosion resistance, and ease of maintenance.

Key Selection Recommendations:

Corrosive media (e.g., bleach) → Choose titanium or Hastelloy plates + PTFE gaskets.
High-viscosity/scaling-prone media (e.g., black liquor) → Opt for wide-gap plates + EPDM gaskets.
Waste heat recovery → Select aluminized steel plates + silicone rubber gaskets for high-temperature oxidation resistance.

With proper selection, PHEs significantly reduce energy consumption, maintenance costs, and enhance process stability in paper mills.

Top