Emerson’s James Bare shared how effective process control and tuning improves combustion air management and improves overall emissions control at the 2019 Ovation Users’ Group conference. James opened describing different types of boilers and their operation in different regions. The focus of the presentation was on coal-fired boilers.
Combustion of coal with air creates steam from water which drives a steam turbine generator. Combustion requires fuel, heat, air to create steam with drives the turbine connected to an electrical generator to create electricity. One the waste side of the process, the ash from the spent coal is sent to be pulverizer and the emissions are cleaned through selective catalytic reduction (SCR) and scrubbers.
Heat is the primary objective and CO2, CO, NOx, SO and particulates are byproducts. Non-ideal combustion can result from fuel composition, air composition, improper mixing of the two and inadequate surface area where combustion occurs.
Optimizing combustion improves efficiency, improves regulatory compliance, and improves availability & reliability. James explain the control strategy for managing fuel flow and air flow into the boiler combustion process. Some key measurements for combustion include flow rates, oxygen level, back pressure, and flue gas composition. Cross-limiting logic helps to control the combustion to achieve optimum combustion.
Combustion air must lead fuel on load changes to make sure combustion is not starved. Then the air composition can be optimized to the fuel rate at the new load level.
Visit the Ovation Advanced Power Applications area on Emerson.com for more on optimizing combustion control and other key electrical power generation applications.