Optimizing Boiler Efficiency Through Combustion Control

Optimizing Boiler Efficiency Through Combustion Control

At Watervliet Arsenal, New York, the ESTCP Installation Energy Test Bed successfully demonstrated a cost-effective combustion control and monitoring system for commercial and industrial boilers. The digitally controlled system, which monitors boiler performance on a continuous basis and reduces greenhouse gas emissions, significantly improved fuel efficiency. It essentially transforms decades-old boilers into state-of-the-art, high-efficiency reduced-emissions systems. With its broad applicability on installations throughout the U.S., the system is expected to lead to significant cost and energy savings for DoD.

Boilers with a capacity larger than 10 MMbtu/hr represent the bulk of commercial boiler systems delivering steam for industrial processes, space heating, and hot water. The overwhelming majority of these systems are more than 10 years old and do not operate at optimum efficiency, with 90 percent lacking automated controls. Because replacing these boilers is often cost prohibitive, upgrading the combustion control system represents a cost-effective solution for increasing boiler efficiency and reducing flue gas emissions.

United Technologies Research Center (UTRC) and Fireye (a division of UTRC’s Climate, Controls, and Security Systems) developed a retrofit solution for hot water or steam generation boilers with capacities larger than 10 MMbtu/hr referred to as CO/O2 trim. This technology incorporates a novel control algorithm, low cost sensors to monitor exhaust composition, and a user-friendly tool to visualize boiler performance. The sensors monitor oxygen (O2) and carbon monoxide (CO) concentrations in flue gas to improve the boiler’s fuel-to-steam efficiency. The controller continuously maintains the optimum proportion of fuel and air feeding the burner to reduce inefficiencies arising from excess air content while preventing unsafe operation arising from incomplete combustion.

The combustion control and monitoring system was installed on Watervliet’s 25 MMbtu/hr steam boiler, and the Test Bed demonstration assessed boiler performance using (1) the legacy mechanical system, (2) the commercially available state-of-the-art electronic O2 trim solution, and (3) the UTRC/Fireye prototype CO/O2 trim solution. During the 1-year testing campaign, the CO/O2 trim system demonstrated fuel savings of about 4 percent for typical boilers with a corresponding reduction in carbon dioxide (CO2) emissions. Adopting this system for all 10-100 MMbtu/hr boilers older than 10 years across DoD has the potential to save $56 million in fuel costs annually and avoid the emission of 600,000 tons of CO2 with a payback period of 2 years or less.

Reducing inefficiencies, fuel expenditures, and emission output for this class of boilers is key to meeting DoD’s goals for energy security and environmental impact. The estimated cost of installing the combustion control and monitoring system is $40,000, with 4 days of outage, and annual maintenance costs of about $1,500 per boiler. The prototype tested is at Technology Readiness Level 6. Based on results from this demonstration, further development, testing, and certification are ongoing to advance the system to Technology Readiness Level 8, facilitating commercialization and enabling widespread deployment of this innovative technology.

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