Application of Oxygen Trim Control to Small Packaged Boilers

Abstract

Small packaged boilers are used to generate steam or hot water for industrial, commercial and institutional power plants. Due to their small size and relatively small fuel capacity, they have not received the energy saving attention that larger industrial boilers have. That situation is changing as energy deregulation brings gas prices into parity with oil.

This paper describes a recent development brought on by these rising fuel costs and the technological break through of low cost microprocessor controls and inexpensive oxygen sensors to measure excess oxygen in the boiler flue gas. The new developments make possible low cost, continuous, automatic optimization of boiler performance by direct control of air/fuel ratio using flue gas analysis trim control.

New mechanical interfaces capable of modifying the relationship between the air and fuel linkage on existing boilers without expensive jackshaft modification or installation difficulties has significantly reduce the installed cost. A field retrofit installation of an advanced microprocessor based system can be installed for under $10,000. This means that users of boilers as small as 150 HP can obtain good return on investment by retrofitting their existing boilers with oxygen trim control.