Emerson’s Sam Thiara and Scott Pettigrew presented a case study on a steel producer looking to drive energy efficiency solutions to minimize costs and emissions. The objectives of the first project was to reduce CO2 emissions and dust in the facility and reduce natural gas consumption.
The goal of the project was to create a plant with a safe operating platform consisting of both automation and safety instrumented systems. They also wanted to optimize the use of indigenous fuels. From a control standpoint, airflow measurements were difficult with duct issues and older instrumentation. Also the varying type of fuels had various heat release rates. Finally, the existing instrumentation did not provide repeatable measurements and the control valves were aging.
The plant had 7 boilers and multiple turbines, blowers, and condensers. The boilers required burner management systems. The air systems were operated in manual which could not provide optimal combustion to maximize efficiency and minimize emissions. Process control constraints were required to prevent unplanned shutdowns.
Scott noted that the place they had to begin was in the basement–replacing the instrumentation and final control elements. Annubars were used to measure air flow to optimize the combustion control. The architected solution had an overall energy management Plant Master to set overall economic goals for the plant production of steam and electricity.
The Plant Master feeds the boiler master which in turn fed a fuel optimizer to burn the most cost effective available fuels. The fuels include fuel oil, natural gas, gas fuel, coke oven gas, and blast furnace gas. The control strategy is base on true BTU technology where the BTU is calculated and the appropriate airflow is set to control based on BTU content and not boiler curves.
The project team created operator screens with idea of creating a visual “line out” look of the old panel boards. For those unfamiliar with the line out concept, image a long row of meters. When everything is operating well, the meter needles are in a line. When one or more is not, is easy to recognize the line pattern is broken and immediate attention is required to get the boiler lined out.
Sam shared the results that the boilers were put back from manual mode of operation to automatic. The load response to handle process changes is much improved. The project consisting of the steel manufacturers engineering team and Emerson project team continue to work and refine the operation. The project team is currently auditing performance to get the overal energy savings which are currently estimated in the 3-5% range.