Combustion Air Preheat Should Be More Than Simply Recycling Energy

Abstract

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