| Steam heating | Approximately 100–250°C for many process duties; higher temperatures require higher steam pressures and suitable equipment. | Steam condenses in jackets, coils, or heat exchangers and transfers latent heat to the process. | Reactor and vessel jackets, batch heating, reboilers, and plant-wide process heating. | Good heat-transfer rates; steam can serve multiple users; condensate can often be recovered. | Requires a boiler or steam supply, pressure-rated equipment, condensate management, and controls to limit temperature variation. | The site already has a reliable steam network and several processes need heating. |
| Pressurized hot-water system | Commonly about 60–180°C; the water must be kept pressurized above its boiling point at the operating temperature. | Hot water circulates through jackets, coils, or heat exchangers. | Temperature-controlled reactors, formulation vessels, cleaning systems, and lower-temperature process circuits. | Provides stable, uniform heat and can offer finer temperature control than condensing steam in some applications. | Needs circulation pumps, expansion and pressure protection, and careful control of water quality and system pressure. | Moderate temperatures and steady, closely controlled heating are more important than very high temperatures. |
| Thermal-fluid (heat-transfer-oil) system | Often used from roughly 150°C to 300°C; the allowable maximum depends on the selected fluid and equipment design. | A liquid heat-transfer fluid circulates in a closed loop through a heater and process equipment. | High-temperature reactor jackets, distillation equipment, and processes that need heat above typical hot-water ranges. | Can deliver elevated temperatures at relatively low system pressure compared with pressurized water at the same temperature. | Fluid aging, oxidation, leaks, fire risk, expansion capacity, and fluid-specific temperature limits require attention. | High process temperatures are needed without using a high-pressure water circuit. |
| Electric process heating | Application-dependent; immersion and circulation heaters commonly serve liquid duties, while purpose-built electric furnaces can reach much higher temperatures. | Electrical resistance elements heat a liquid, vessel, air stream, or other process medium directly or through a heat-transfer loop. | Small or modular reactors, tank heating, heat tracing, pilot plants, and locations where combustion products must be avoided. | Precise controllability; no on-site combustion exhaust at the point of use; easy to install in modular systems. | Electrical supply capacity, energy cost, hazardous-area requirements, and element compatibility with the process must be assessed. | Accurate control, modular installation, or avoidance of local combustion emissions is a priority. |
| Direct-fired process heater | Can serve high-temperature duties; achievable process temperatures depend on heater design, fuel, materials, and the process stream. | Fuel combustion transfers heat to process tubes or equipment through radiant and convective sections. | Feed preheating, thermal-fluid heating, and selected high-temperature continuous process duties. | Can provide high heat input and may be practical where fuel infrastructure and experienced operating staff are available. | Requires combustion controls, emissions management, burner safeguards, inspection, and protection against tube overheating. | Large, continuous heat duties justify a dedicated fuel-fired installation and its associated safety systems. |