By Robert Evatt
A variety of coal emission regulations were highlighted by industry workers and researchers during the session titled “ACQS Upgrades for Enhanced O&M Performance” at POWER-GEN International 2016.
Chris Wedig of CB&I said that coal plants, even older ones, are becoming subject to load following; they must now adjust power output as demand for electricity fluctuates throughout the day.
“Load following at coal-fired power plants is a reality,” he said.
This increasing requirement of load following comes as heavy industrial demand decreases and residential demand continues to rise.
And environmental regulations on emissions are still in place even with new operations. Utilities now must develop operations and maintenance methods to compensate for the shifts in load.
Additionally, load following and the associated temperature shifts create new stresses on nearly every piece of equipment at coal plants, meaning operators must keep a close eye on equipment performance.
Co-author Joseph Klobucar of HDR presented a report on two spray dryer and fabric filter installations in two coal plants—a report that won POWER-GEN International’s Paper of the Year.
The system consisted of rotary atomized spray dryers for SO2 control, pulse-jet baghouses for particulates, powder-activated carbon for mercury control, and draft system modification.
The systems were successful at both the Columbia Generating Station in Wisconsin and the Ottumwa Generating station in Iowa. The system produced a 90 percent reduction in mercury emissions, was very reliable, and exceeded SO2 and particulate matter emission standards.
However, there were a number of challenges, including a very cold Wisconsin winter, pressure damage to an SDA byproduct bin vent filter, issues with SDA flop valves, and slurry line failures.
Conner Cox of United Conveyor Corporation (UCC) presented alternative approaches to emission controls.
DSI equipment can now come in pre-engineered, small modules that can fit underneath silos and save on insulation costs.
Additionally, UCC’s COBRA lance system produces a low-pressure zone within flue gas and improves extraction of pollutant material.
Stuart Nicholson of Primex Process Specialists presented a look at corrosion problems at Carneys Point Generating Plant in New Jersey.
Though the plant was built in 1995, corrosion problems cropped up that year and continued with time. By 1998, bag cap failures began to fail. Plant officials replaced them with stainless material, but those eventually failed as well due to chloride stress.
By 2014, officials at Carneys began a program to replace filter caps with a hanger apparatus that didn’t need a sealing cap at all. The program was a success, and the hangers were implemented throughout the plant.