Application of KDP Plate Heat Exchangers in the Metallurgical Industry

Application of KDP Plate Heat Exchangers in the Metallurgical Industry：

Process Flows and Material Requirements for Plates and Gaskets

Plate heat exchangers (PHEs) are widely used in the metallurgical industry for cooling, waste heat recovery, and medium heating due to their high heat transfer efficiency and compact design. They are particularly suitable for extreme conditions involving high temperatures and corrosive environments. Below is a detailed explanation of their applications, process flows, and material requirements for plates and gaskets.

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Typical Process Flows and Applications in Metallurgy

Ironmaking Process

Applications:

Blast furnace cooling water systems, waste heat recovery from hot blast stoves.

Requirements:

Cooling of blast furnace wall circulating water (80–120°C), requiring resistance to scaling and corrosion.

Recovery of waste heat from hot blast stove exhaust gases (containing SO₂ and dust, 300–500°C).

Steelmaking Process

Applications:

Converter/EAF (Electric Arc Furnace) flue gas cooling, secondary cooling water for continuous casting machines.

Requirements:

Rapid cooling of converter flue gas (from 1000°C to below 200°C to prevent dioxin formation).

Cooling water circulation for continuous casting (containing iron oxide scale and oil, requiring anti-clogging design).

Rolling Process

Applications:

Lubricating oil cooling for rolling mills, waste heat utilization from annealing furnace exhaust.

Requirements:

Stabilizing rolling oil temperature (40–60°C to avoid viscosity changes).

Heat exchange with annealing furnace exhaust (containing acidic condensate, pH 2–4).

Non-Ferrous Metal Smelting (Copper, Aluminum, Zinc)

Applications:

Electrolyte heating/cooling, waste heat recovery from smelting furnace flue gas.

Requirements:

Temperature control of copper electrolyte (60–70°C, containing H₂SO₄ and Cu²⁺).

Cooling of aluminum smelting furnace flue gas (containing HF and Al₂O₃ dust, highly corrosive).

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Plate Material Selection Criteria and Comparisons

Metallurgical environments are extremely harsh, requiring plates to withstand high temperatures, corrosion, and erosion. Common materials include:

Material TypeSuitable ConditionsMax TempAdvantagesLimitations
316L Stainless SteelGeneral cooling water, neutral media (e.g., continuous casting water)150°CLow cost, easy fabricationPoor resistance to Cl⁻ and SO₂
2205 Duplex SteelChloride-containing water (e.g., seawater cooling), weak acids250°CResists pitting and SCCNot suitable for concentrated H₂SO₄
254SMO Super StainlessHigh-Cl⁻ environments (e.g., coastal plants), flue gas desulfurization300°C6% Mo content, resists crevice corrosionExpensive
Titanium (Ti)Strong acids (e.g., copper electrolyte, HF gas), seawater cooling350°CResists Cl⁻ and HF, long lifespanSensitive to alkalis (pH >10)
Hastelloy C-276Extreme corrosion (e.g., concentrated H₂SO₄, mixed acids), high-temp flue gas (>400°C)500°CAll-around corrosion resistanceVery high cost
Graphite CompositeStrong acid/alkali alternation (e.g., pickling line waste treatment)200°CResists all acids/alkalisBrittle, limited to low-pressure use

Design Considerations：

Plate Pattern:

Wide flow channels (e.g., "herringbone") for flue gas to prevent dust clogging.

Thickness:

≥0.8mm for corrosive media; ≥1.2mm for erosion-prone flue gas side.

(SCC: Stress Corrosion Cracking)

Gasket Material Selection

Metallurgical gaskets must endure high temperatures, oils, acids/alkalis, and particulate abrasion. Common materials:

Gasket MaterialTemp. RangeChemical ResistanceApplications
NBR (Nitrile Rubber)-20–120°CResists mineral oils, not oxidating acidsRolling mill oil cooling
EPDM (Ethylene Propylene Diene)-40–150°CResists weak acids/steam, not oilsHot blast stove waste heat recovery
FKM (Fluorocarbon Rubber)-20–200°CResists oils, acids, solvents (e.g., H₂SO₄, HF)Electrolyte heat exchange, pickling lines
PTFE-Coated Gaskets-100–260°CChemically inert, but low elasticityStrong acid/alkali environments (requires metal support)
Metal-Jacketed Gaskets-200–800°CUltra-high temp/pressure (e.g., molten metal cooling)Smelting furnace direct cooling

Key Considerations:

Dynamic Sealing:

Use high-elasticity FKM gaskets in high-vibration rolling mills.

Cleaning Compatibility:

Must withstand HNO₃/HF mixed cleaning agents in pickling lines.

KDP Case Studies and Maintenance Guidelines

Case 1: Copper Electrolyte Heating

Plates:

Titanium (resists H₂SO₄ and Cu²⁺).

Gaskets:

FKM (acid-resistant and flexible).

Maintenance:

Monthly inspection for scaling on the electrolyte side.

Case 2: Blast Furnace Gas Waste Heat Recovery

Plates:

2205 duplex steel (resists SO₂ and Cl⁻ in flue gas).

Gaskets:

PTFE-coated (high-temp resistant and anti-fouling).

Design:

Flue gas side flow channels widened to 8mm to prevent ash buildup.

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Best Practices:

Anti-Scaling:

Add scale inhibitors to cooling water; maintain flow velocity >0.5 m/s.

Freeze Protection:

Drain exchangers in winter to prevent cracking in cold climates.

Plate heat exchangers surpass traditional heat exchangers in the four major pain points of the metallurgical industry: high-temperature corrosion, dust clogging, energy efficiency improvement, and convenient maintenance. They are particularly suitable for:

Flue gas waste heat recovery (such as converters, anode furnaces)
Highly corrosive medium heat exchange (electrolyte, pickling waste acid)
Space-constrained transformation projects

Its comprehensive life cycle cost can be reduced by 35-50% compared to shell and tube, making it the preferred solution for energy-saving upgrades in the metallurgical industry.

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