Process Heaters, Furnaces and Fired Heaters: Improving Efficiency and Reducing NOx

Process Heater
(courtesy of
AMETEK Process
Instruments)

A process heater is a direct-fired heat exchanger that uses the hot gases of combustion to raise the temperature of a feed owing through coils of tubes aligned throughout the heater. Depending on the use, these are also called furnaces or red heaters. Some heaters simply deliver the feed at a predetermined temperature to the next stage of the reaction process; others perform reactions on the feed while it travels through the tubes.

Process heaters are used throughout the hydrocarbon and chemical processing industries in places such as refineries, gas plants, petrochemicals, chemicals and synthetics, olefins, ammonia and fertilizer plants. Some plants may have only two or three heaters while larger plants can have more than fifty.

Most of the unit operations in these plants require red heaters and furnaces. These operations include:

• Distillation 
• Fluidized Catalytic Cracking (FCC) 
• Alkylation 
• Catalytic Reforming 
• Continuous Catalyst Regeneration (CCR) 
• Thermal Cracking 
• Coking 
• Hydrocracking 

Typical process heaters can be summarized as follows: 

• Start-Up Heater — Starts-up a process unit where it is required to heat up a fluidized bed of catalyst before adding the charge. 
• Fired Reboiler — Provides heat input to a distillation column by heating the column bottoms and vaporizing a portion of it. Used where heat requirement is greater than can be obtained from steam. 
• Cracking Furnace — Converts larger molecules into smaller molecules, usually with a catalyst (pyrolysis furnace). 
• Process Heater — Brings feed to the required temperature for the next reaction stage. 
• Process Heater Vaporizer — Used to heat and partially vaporize a charge prior to distillation. 
• Crude Oil Heater — Heats crude oil prior to distillation. 
• Reformer Furnace — Chemical conversion by adding steam and feed with catalyst.

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Process Heaters, Furnaces and Fired Heaters: Improving Efficiency and Reducing NOx from Belilove Company-Engineers