Biphenyl Heating Systems: Physical & Chemical Properties of Biphenyl and Its Industrial Applications

1. Introduction to Biphenyl Heating Systems: Efficient High-Temperature Thermal Solutions

A biphenyl heating systemhttps://8ruiyan.com/en/all-organic-heat-carrier-boilers/ is a high-temperature heating device that uses biphenyl (C₁₂H₁₀) or its mixtures (e.g., biphenyl-diphenyl eutectic blends) as a heat transfer fluid. Widely used in chemical, pharmaceutical, petroleum, and material heat treatment industries, biphenyl heating systems operate stably within 250°C to 400°C, offering advantages such as high-temperature capability at low pressure, superior thermal efficiency, and precise temperature control compared to traditional steam heating systems.

2. Physical Properties of Biphenyl: Why Is It an Ideal Heat Transfer Fluid?

Biphenyl is an aromatic hydrocarbon with excellent thermal properties, making it an optimal heat transfer medium:

Physical Property	Value	Industrial Significance
Melting Point	69.2°C	Requires preheating or eutectic mixtures (e.g., Dowtherm A)
Boiling Point (1 atm)	255°C	Can operate above 400°C under pressure
Thermal Conductivity	0.13 W/(m·K) (liquid, 100°C)	High heat transfer efficiency, uniform temperature distribution
Specific Heat Capacity	~1.25 kJ/(kg·K)	Strong heat retention, excellent thermal stability
Density (Liquid)	1.04 g/cm³ (100°C)	Easy to pump and circulate
Vapor Pressure	Low (~0.3 MPa at 300°C)	Low system pressure, enhanced safety

3. Chemical Properties of Biphenyl: Stability and Safety Considerations

(1) Chemical Stability

• Stable under inert atmospheres (e.g., N₂) and resistant to high-temperature oxidation (<400°C).
• Non-corrosive to stainless steel and carbon steel, making it suitable for industrial equipment.
• Chemically inert to most industrial chemicals, ideal for polymerization, catalysis, and distillation processes.

(2) Thermal Decomposition & Safety Risks

• Decomposition temperature: ~450°C (may produce benzene, toluene, etc.).
• Flammability: Flash point ~113°C—requires fire and leak prevention measures.
• Toxicity: Biphenyl vapor irritates the respiratory system—ensure system sealing.

(3) Optimized Biphenyl Mixtures (e.g., Dowtherm A)

Industrial applications often use eutectic mixtures (26.5% biphenyl + 73.5% diphenyl ether, Dowtherm A), offering:
✅ Lower melting point (12°C)—prevents solidification in cold climates.
✅ Higher boiling point, improved thermal stability.
✅ Better fluidity, reduced energy consumption.

4. Biphenyl Heating Systems vs. Other Heating Methods

Heating Method	Max Temperature	Pressure Requirement	Thermal Efficiency	Typical Applications
Biphenyl System	~400°C	Low (<1 MPa)	High	Fine chemicals, pharma, materials
Steam Heating	~250°C	High (>4 MPa)	Moderate	Food processing, general chemicals
Molten Salt	~600°C	Atmospheric	High	Solar thermal storage, extreme heat
Electric Heating	~1000°C	Atmospheric	Low-moderate	Lab-scale, small-batch production

✅ Advantages of Biphenyl Systems: High temperature + low pressure + precise control, ideal for temperature-sensitive processes.

5. Safe Operation & Maintenance of Biphenyl Systems

• Leak prevention: Regular sealing inspections, leak detection systems.
• Oxidation protection: Nitrogen blanketing to prevent degradation.
• Fluid replacement: Monitor acidity and moisture to avoid corrosion.
• Emergency cooling: Prevents thermal runaway and decomposition.

6. Future Trends

• Eco-friendly alternatives: Developing less toxic, higher-temperature fluids.
• Smart control systems: IoT integration for optimized efficiency and safety.
• Waste heat recovery: Improving energy utilization, reducing costs.

Biphenyl heating systems, leveraging biphenyl’s outstanding thermal stability and heat transfer performance, are indispensable in chemical, pharmaceutical, and material industries. Proper selection of biphenyl or eutectic mixtures, combined with rigorous maintenance, ensures long-term, efficient, and safe operation.

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