Last updated on April 1st, 2019 at 03:36 pm

A process heater is any equipment with the express purpose of heating chemical process streams. Any process where electrical energy transforms into usable heat qualifies as electric heating.

As the name indicates, an electric process heater (EPH) is an electric heater that is in direct contact with a process. For example, a static process where an electric flanged immersion heater is generally used or a flowing process where a circulation heater is widely used in heating tanks. Variety of process fluids work with an EPH, including:

• Air
• Ammonia
• Fuel oil
• Petrochemical fluids
• Fuel gas
• Water
• Nitrogen

The process fluid enters from one end of the heating tank, passes through the heating element and leaves from the other end of the heating tank. During this process, heat from the heating element is transferred to the process fluid either by convective or radiant heat transfer. For a static process, the immersion heater is submerged in the process fluid contained in a heating tank and heats up by natural convection. And during a flowing process, the circulation heater is immersed inside a pressure vessel containing the process fluid and heats up by forced convection.

Electric Process Heaters (EPH) in Power Generation

An EPH finds use in many industries including power generation, oil and gas refining, petrochemical, pipeline etc. A few examples are below.

To ensure that condensation does not occur for the gas in a gas turbine before combustion occurs, most gas turbines require superheating fuel gas to extremely high temperatures. An electric fuel gas heater achieves these temperatures. If condensation was to occur before combustion, there can be excessive exhaust emission damaging the fuel nozzle and reducing its life.

Within the pulp and paper mills, temperature fluctuations cause the calendar roll to expand and contract and therefore affect the quality of the final product. During the winter period, this problem gets more aggressive. To prevent this, industries use electric heaters.

EPHs also help in conveyer systems. During cold weather conditions, particulate materials can form lumps and freeze on to the conveyer belts. To prevent this, a flat tubular heater can be employed with its ends sealed from moisture and contamination. Stainless steel heating elements are more suited for this application.

Applications of Electric Process Heaters

A few other applications of electric process heaters are:

• Heating water in order to prevent it from freezing
• Electric air heater used in nitrogen generators to heat the air
• Heating diesel fuel oil (inside the heating tanks) in order to prevent the formation of waxy paraffin
• Nitrogen electric heater used to heat nitrogen gas in a desiccant regenerator
• Heating fuel gas to prevent hydrocarbon condensation
• Electric crude oil heater used in processing crude oil to reduce its viscosity
• Re-boiling of glycol to separate water from glycol
• Regeneration of absorption beds through heating ammonia

Electric heaters see extensive use due to their benefits, such as precise control, lower weights, smaller footprint, no harmful emissions, high outlet temperatures etc.

References

• http://en.wikipedia.org/wiki/Electric_heating#cite_note-3
• http://en.wikipedia.org/wiki/Joule_heating
• Robert Klein, Immersion heaters: selection & implementation, Chemical Engineering. 113.1, Jan 2006
• Rob Bohn, Mike Bange and Joe Foreman, The basics of electric process heating, IEEE, Paper No. PCIC-94-14, 1994