COMBUSTION
CONTROLLING COMBUSTION IN FIRED PROCESS HEATERS
Fired process heaters are integral to hydrocarbon processing . Specifically designed for the reaction of fuel and air to produce extremely high gas temperatures , heaters transfer this energy to potentially highly flammable process fluids via heat exchangers .
They consume large quantities of fuel , produce large quantities of emissions , and are a potential safety hazard to personnel and plant . However , they are currently irreplaceable within many petrochemical processes – so they warrant the highest levels of understanding and care in their operation and control .
The cornerstone of a well-controlled combustion process is an optimized air-tofuel ratio for efficient fuel consumption . This produces considerable benefits , in the form of efficiency , reduced emissions , safety , and extended life of equipment .
Before analyzer technologies were developed to measure excess air in the products of combustion , fired heaters were run in conditions of high excess air . Although this meant inefficient and costly fuel consumption , it was the only way to avoid the creation of low-oxygen , fuel-rich conditions that could lead to a potentially dangerous explosion .
Too much oxygen leads to cooler burning , causing a significant reduction in combustion efficiency due to an increased loss of heat to the atmosphere , while the excess of oxygen available combines with nitrogen and sulfur to produce undesirable emissions .
The understanding that a fuel-rich ( high carbon monoxide ) situation is a potential source of explosions has caused the measurement of carbon monoxide to move from a supporting combustion measurement to a key safety measurement .
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