Improving Combustion Efficiency, Reliability, and Safety in Large Fired Heaters Utilizing Multiplexed Laser Based Monitoring and Diagnostic Systems

Operators are often challenged to maintain well-balanced, uniform combustion across a large fired heater in order to optimize efficiency, reliability, production yields, and safety and to reduce emissions.  While most large furnaces and heaters have several individual sensors available to monitor temperature, O2, and CO, typically at the furnace exit, the number of such sensors available for use directly inside the firebox is very limited. This paper describes a novel but well-proven wavelength-multiplexed, laser-based monitoring and diagnostic technology that measures temperature, oxygen, and carbon monoxide directly in the high temperature zone of combustion furnaces and heaters. Because of the fiber-coupled nature of the system, multiple locations (up to 24 lines of sight) can be measured with a single system.

Utilization of wavelength-multiplexed tunable diode laser absorption spectroscopy (TDLAS) laser systems for continuous reporting of multiple combustion gases across the radiant and convective zones of a combustion process represents a first-of- its-kind application for TDLAS technology. It allows operators to tune burner controls to achieve fuel savings, increase production yields, lower excess O2, monitor CO, reduce NOx and CO₂ emissions, and extend furnace tube/coil life through well-balanced temperature and oxygen profiles across the entire envelope of the heater. 

This paper describes the design, use, and value of wavelength-multiplexed TDLAS laser technology as applied to large furnaces.