Combustion Air Preheat and Radiant Heat Transfer in Fired Heaters - A Graphical Method for Design and Operating Analysis

The installation of combustion air preheat is a widely used technique for improving the fuel efficiency of existing fired heaters and fired tubular reactors. By increasing adiabatic flame temperature, combustion air preheat increases radiant section heat transfer efficiency thereby enabling the transfer of the same amount of energy from a lower total heat release in the radiant box. This paper presents a graphical procedure that can be used (1) to estimate fuel savings obtained by combustion air preheat, and (2) to analyze the effects of variations in operating conditions on a combustion air preheat furnace, such as load changes, over-or-under firing, and excess air control

Combustion Air Preheat Should Be More Than Simply Recycling Energy

Combustion air preheat can and should result in fuel savings far in excess of the energy added to the combustion air. In a typical installation of air preheat on a fired tubular reactor, the addition of 2.5 million BTU/hr to the combustion air results in a fuel savings of 6.8 million BTU/hr. Control of excess effects of excess combustion air on radiant heat transfer in a fired tubular reactor, the point at which air preheat does become simply recycling energy, and the point at which any advantage of air preheat is lost entirely. How air preheat and excess air influence radiant heat transfer is discussed and a calculation method presented which can be used to develop justification for improved excess air control

Multiobjective optimization of an industrial LPG thermal cracker using a first principles model

10.1021/ie801409mIndustrial and Engineering Chemistry Research48219523-9533IECR