ENV-17-04 Beyond MACT DDDDD: Boiler and Heater Tuning From a Best Management Practices Perspective

Description:

40 CFR 63 Subpart DDDDD (MACT DDDDD), referred to as the Industrial, Commercial, and Institutional (ICI) Heater and Boiler MACT Rule requires affected facilities to conduct combustion tune-ups on applicable heaters and boilers in an effort to improve emission performance. Heater and boiler tuning can be described as part science and part intimate knowledge of the equipment’s operational characteristics and process needs, but it must be based on accurate and representative flue gas measurement. While many facilities believe their heaters and boilers to be well optimized, recurring compliance tuning efforts for MACT DDDDD has revealed that this is not always the case. For example, many units are observed operating under high excess O2 firing conditions or utilizing low-NOx burners that due to their design, have the potential to create high and unmanageable CO emissions when attempting to lower excess O2. In some instances, combustion air dampers, air louvres, and primary air registers on burners are inoperable, making tuning difficult and sometimes impossible. In other cases, a facility’s process control system has logic set points that precluded true optimization of the heater or boiler. For Gas 1 (i.e. natural gas, refinery fuel gas, etc.) type heaters or boilers greater than 10 MMBtu/hr of heat input capacity that do not have automated oxygen trim systems and do not meet the definition of limited use, the work practice provision for the Subpart DDDDD Rule continues to be required annually for affected facilities. These annually-recurring tune-ups provide the opportunity to gather a significant amount of data from a variety of Gas 1-fired process heaters and boilers. Nearly three years of data from tune-ups, conducted on over 500 boilers and heaters of various makes, models, and sizes, have been used to evaluate cost savings estimates (actual and potential) that combustion tuning and optimization provides relative to natural gas fuel consumption. Data from these results indicate cost savings from the tune-ups are more than sufficient to provide simple payback on the annual, biennial, and 5-year tune-up bases. For example, improved combustion efficiency in heaters and boilers rated between 40 and 150 MMBtu/hr realized an average fuel savings of around $10,250 per year from a standard MACT DDDDD tune-up and a simple payback on cost in 2-3 months. Even more promising are the findings relative to the potential cost savings associated with full optimization of the combustion settings for a heater or boiler. For heaters and boilers with room for improvement beyond the MACT DDDDD standard, unrealized fuel savings may be as high as $75,000 per unit, per year. The purpose of this paper is to summarize heater and boiler tuning from a best management practices perspective, rather than the focus on emission reductions relative to MACT DDDDD.