Thermal Oil Boiler

Estimated EXW reference prices vary by thermal capacity and design:

– Small Vertical Systems (<0.7 MW / <600,000 kcal/h): USD 8,000 – 23,000

– Medium Horizontal Systems (0.7–3.5 MW / 600,000–3,000,000 kcal/h): USD 23,500 – 88,000

– Large High-Temperature Systems (>3.5 MW / >3,000,000 kcal/h): Starting from USD 88,000+

Prices vary by operating temperature, thermal capacity, temperature control requirements, and burner/auxiliary brands. Quotes cover the boiler pressure vessel and control cabinet only (excluding freight). Custom multi-coil units are quoted separately.

Boilers are classified by three main criteria:

• By Fuel/Heat Source:Gas-fired, heavy/light oil-fired, biomass-fired, or electric thermal oil heaters.
• By Coil Structure:Compact vertical design (small footprint, fast start) or horizontal multi-pass coil design (larger oil capacity, higher efficiency).
• By Delivery Configuration:Traditional split system or integrated skid-mounted system (factory pre-piped with pumps and tanks).

A complete thermal oil system comprises five main components:

• Heating Unit:Radiant and convective multi-pass heating coils enclosed in insulation.
• Heat Source:Fully automatic gas/oil burner, biomass combustion grate, or electric heating elements.
• Fluid Circulation Module:High-temperature thermal oil circulation pumps and air-oil separators.
• Expansion & Storage Tanks:High-level expansion tank (for fluid degassing and volumetric expansion) and low-level storage tank (for thermal oil drain and emergency dumping).
• Controls & Interlocks:PLC cabinet with automatic high-temperature cutouts, differential pressure (DP) switches, and flow monitoring.

The main advantage is achieving high working temperatures (300–350 °C) at low operating pressures (<0.8 MPa), whereas achieving 300 °C saturated steam requires approximately 8.6 MPa pressure.

In addition, closed-loop thermal fluid operation avoids most water-side scaling, corrosion issues, and freezing risks, reducing water treatment requirements.

Depending on system design, temperature control accuracy can reach ±1 °C.

Standard gas/oil or electric thermal oil heaters typically take 25–40 days.

Custom multi-pass coil designs, large biomass units, or high-temperature systems (>300 °C) take 45–75 days (including coil NDT and hydrostatic testing).

Maintain proper fluid circulation and perform strict initial degassing:

1. Flow Velocity:Maintain fluid velocity within heating coils, typically around 1.5–3 m/s depending on fluid properties and system design, to prevent thermal cracking, hot spots, and internal tube coking.
2. Degassing & Dewatering:After oil filling or maintenance, perform a slow thermal heating and degassing process to remove moisture before increasing to operating temperatures. Water vapor can cause pressure fluctuations and pump cavitation.
3. Circulation Interlock:Burners must automatically interlock with fluid flow switches to shut down instantly if circulation drops.

Thermal fluid degrades over time due to thermal cracking and oxidation, affecting heat transfer performance and reducing the flash point.

Regular testing of key parameters helps determine fluid condition:

• Flash Point:Replace when flash point drops significantly according to the thermal oil supplier’s recommendation.
• Kinematic Viscosity:Replace if viscosity changes beyond the recommended operating range.
• Acid Value:Replace or neutralize if acid value exceeds the manufacturer’s recommended limit.
• Carbon Residue:Replace or filter if carbon residue exceeds the recommended operating limit.

Common field installation issues include:

• Incorrect Expansion Tank Height:The high-level tank must be installed at sufficient height according to pump suction requirements to prevent cavitation.
• Poor Piping Slope:Inadequate slope can cause air pockets and localized overheating in process lines.
• Wrong Gaskets/Seals:Using unsuitable rubber or low-temperature sealing materials instead of high-temperature gaskets can lead to oil leaks.
• Undersized Storage Tank:Storage tank volume must exceed the total system fluid expansion volume for safe gravity drain during power outages.

Thermal oil systems are widely used in chemical reactor jackets, asphalt heating and terminal storage, textile heat-setting machines, plywood/wood pressing, paper coating and drying, food frying/baking, and rubber/plastic molding.