New Generation of Combustion Technologies Optimizes Coal-Fired Boiler Performance

摘要

Emissions regulations, fuel flexibility, and market competition are driving the need for optimization of boiler performance and emissions. Maintaining good combustion performance is critical for boiler optimization. A number of boilers, such as those firing problematic coals, facing coal variability and quality issues, and/or equipped with combustion modifications for NO{sub}x emissions control, can benefit from the latest generation of combustion optimization technologies. A new generation of combustion optimization systems is available to improve plant performance and help reduce the detrimental impacts of combustion modifications. The technologies provide tools for operators to monitor and control local combustion conditions in the furnace. This paper presents the GE Zonal Combustion Tuning system and its application to a 250 MW boiler firing bituminous coal and a 380 MW boiler firing low-rank coal. The Zonal Combustion Tuning system relies on well-established methods for combustion optimization including burner coal flow balancing and sensor-based combustion tuning. Balancing burner fuel distribution is traditionally a prerequisite of combustion optimization. The use of an automatic burner coal flow balancing system can reduce burner coal flow bias from levels over 30 percent to levels consistently below 5 percent and maintain these performance levels over a wide range of mill operation. Once coal flow is balanced, combustion sensors can be used to systematically balance combustion performance and reduce CO emissions. In one of the cases presented in this paper, balancing combustion also reduced the fly ash unburned carbon or loss on ignition (LOI). In addition to balancing local combustion conditions throughout the furnace, the Zonal Combustion Tuning system can be integrated with the boiler controls to maintain the boiler at optimum excess O{sub}2 levels, resulting in maximizing boiler thermal efficiency, minimizing furnace exit gas temperatures, and lowering NO{sub}x emissions while meeting constraints on CO and fly ash LOI. In summary, the GE Zonal Combustion Tuning system integrates expert combustion principles with the latest sensor and control technologies to improve combustion performance. Improving combustion performance can help to reduce issues associated with poor combustion, such as delayed combustion, zones of fuel-rich gases or high furnace exit gas temperatures, excessive slagging and fouling and sootblowing, and high metal temperatures. The expected benefits of the system include maintaining optimum emissions and carbon-in-ash levels, while improving boiler capacity, availability, reliability, and efficiency.