Thermic Fluid Heaters

A thermic fluid heater (also known as a thermal oil heater or hot oil boiler) is an industrial heating system that uses a special heat transfer fluid (thermic fluid or thermal oil) as a medium to transfer heat from a furnace to various process applications. Unlike steam boilers, they operate at much higher temperatures at or near atmospheric pressure, eliminating the need for high-pressure vessels, blowdown, and water treatment.

Types of Thermic Fluid Heater

Solid Fuel Fired Heaters: Use biomass (wood, briquettes, rice husk), coal, or other solid fuels.

Liquid Fuel Fired Heaters: Use fuels like furnace oil, LDO, diesel, or natural gas.

Gas Fired Heaters: Use natural gas, LPG, or biogas.

Electrically Heated Heaters: Use immersion heaters to heat the thermic fluid, often for smaller systems or where precise temperature control is needed.

Vertical Heaters: Space-saving design, often used for smaller to medium capacities.

Horizontal Heaters: Larger capacity, common for industrial applications.

Closed-Loop Systems: Most common, where the thermic fluid continuously circulates.

Applications in Various Industries

Textile Industry: Drying, dyeing, heat setting.

Chemical & Pharmaceutical Industry: Heating reactors, distillation columns, dryers, heat exchangers.

Food & Beverage: Frying, baking, drying, pasteurization, sterilization.

Paper & Pulp Industry: Drying paper, heating calenders.

Rubber & Plastics Industry: Curing, molding, extrusion, laminating, calendering.

Edible Oil Industry: Cooking, refining, deodorizing.

Plywood & Laminate Industry: Hot presses.

Technology:

Involves a coil (typically helical) through which the thermic fluid circulates, absorbing heat from combustion gases (or electric elements). A high-efficiency burner for fuel combustion. An expansion tank to accommodate fluid expansion. A circulation pump to move the fluid. Control systems (PID controllers, PLCs) for temperature regulation, safety interlocks, and alarm systems. The thermic fluid itself is typically a synthetic organic oil or mineral oil with high thermal stability and a high boiling point.

Material Selection Considerations

• Coil/Heating Surfaces: High-quality seamless carbon steel tubes (e.g., SA 179, SA 192) or alloy steel for high-temperature resistance and durability.
• Furnace/Combustion Chamber: Refractory lining (fire bricks, ceramic fiber insulation) to withstand extreme temperatures and insulate the outer shell.
• Outer Casing/Shell: Carbon steel, often insulated and cladded.
• Piping & Valves: Carbon steel or alloy steel compatible with the thermic fluid and operating temperatures/pressures.
• Circulation Pump: Cast iron or steel body, with specific seals compatible with high-temperature thermic fluid.
• Thermic Fluid: Specialized synthetic or mineral-based oils, chosen for high thermal stability, high autoignition point, low vapor pressure, and good heat transfer properties.
• Insulation: Mineral wool or ceramic fiber to minimize heat loss and ensure personnel safety.