Justifying Controls with Opacity-Driven Energy Optimization
At a paper mill in New England, a long-delayed controls upgrade project was cost-justified within eight months of completion. The improved performance and energy savings from an ESP controls project saved the mill an average of $8,000 per month.
"I wish we had made the upgrade years ago when you first recommended it!"
Lack of compelling justification is often what holds back valuable upgrades to pollution control equipment at power plants and industrial process facilities. When justification is found and projects move ahead, it’s not unusual for results to exceed expectations. œWe should have done this a long time ago! is a common response.
That certainly was the case for a paper mill in New England where a long-delayed controls upgrade project resulted in average $8,000 per month savings for the mill, and the entire project was cost-justified within eight months of completion.
Reliability problems first cropped up at the mill ten years after a Research-Cottrell electrostatic precipitator (ESP) was installed in 1982 to treat waste from a utility biomass boiler. (The boiler was designed to burn pulverized coal, #6 oil, biomass wood waste and water treatment plant sludge for electric generation and paper mill production steam.)
These issues continued for years, and then throughout the 1990s several reviews were conducted about the costs and benefits of upgrading the ESP voltage and rapper controls. Unfortunately, budget constraints and lack of adequate ROI data stymied justification for the upgrades.
Finally, in the early 2000s, compelling justification was found. This justification was contingent on achieving opacity-influenced energy optimization. Also required: remote start-stop capabilities allowing control-room operation of voltage and rapper controls.
Neundorfer was selected to provide the new controls. Key to Neundorfer’s approach: inclusion of a control system screen showing real-time savings when operating in performance optimization mode. This provided instant feedback on financial payback to the mill.
The Neundorfer package included 10 MVC-3 adaptive voltage controls, two MicroRap rapper controls and a Windows computer running the Precipitator Optimization System (POS), along with necessary communication link upgrades. (The system required running communication cable from control room to tenth-floor MCC room, and analog signal wiring to connect DCS outputs to the Neundorfer-supplied analog signal interface panel.)
Real-time savings reporting capabilities topped the list of benefits offered by Neundorfer, but there were other important factors at play, too. For example: the original surge protection devices were oil-filled and required time-consuming maintenance and calibration; the new, solid-state MVC controls reduced calibration time to ten minutes per control. (Note: to help customers comply with newer OSHA arc flash safety standards, Neundorfer has more recently implemented safety and efficiency technology not available when this upgrade took place. This newer technology eliminates the need for manual calibration; Neundorfer’s MVC-4 controls are self-calibrating.) The MVC controls also offered secondary-voltage feedback, a feature lacking on the original controls.
The first six voltage controls were installed with the precipitator online, and the remaining four voltage controls, the MicroRap controls and the POS system were installed the next month during a scheduled boiler outage.
Much of the controls installation work was completed by plant electricians, after some initial training by Neundorfer.
At end of the scheduled outage”after calibration, air-load testing of each T/R set, initiation of the two rapper controls and startup of the control room POS”the boiler was brought back online. In the past, short-term opacity excursions typically occurred during transition from startup to online operation. This time, though, opacity remained below ten percent even during high dust load events.
One operator had the opacity monitor system checked and recalibrated because he couldn’t believe how low the opacity remained.
Just as importantly, the new controls resulted in average $8,000 per month savings for the mill, and the entire project was cost-justified within eight months of completion.
œI wish we had made the upgrade years ago when you first recommended it, exclaimed the mill’s project engineer, after observing the improved performance and energy savings.