State-of-the-Art Environmental Protection
KBV Springfield Power Partners (KBV) — the project’s engineering, procurement, and construction (EPC) contractor — purchased a Foster Wheeler boiler (Figure 2), a Toshiba steam turbine generator (Figure 3), and Wheelabrator Air Pollution Control Inc. (a wholly owned subsidiary of Siemens Power Generation) air quality control system (AQCS) equipment. Emissions control at Dallman begins with Foster Wheeler’s Vortex series of split-flame, low-NOx burners in the boiler before the combustion gases pass to a substantial lineup of AQCS equipment (Figure 4).
2. Raise the drum slowly. One of the heaviest and most challenging lifts in the course of constructing a power plant is raising and positioning the steam drum. The complete steam generator was sourced from Foster Wheeler. Courtesy: CWLP
3. Power to the people. A Toshiba steam turbine configured with a combined high- and intermediate-pressure casing couple with a single double-flow low-pressure section provides shaft horsepower to the generator. Courtesy: CWLP
4. Lean and clean. The Foster Wheeler steam generator is configured with low-NOx burners that reduce NOx produced during combustion. A selective catalytic reduction system will reduce NOx levels in the flue gas to meet the plant’s permit limit. Courtesy: CWLP
Downstream of the boiler, an SCR further reduces the NOx concentration in the stack gas. Next up is a powder-activated carbon injection system that is used for mercury removal. A fabric filter, a wet flue gas desulfurization (FGD) system for the removal of SO2 from the stack gas, and wet electrostatic precipitator (WESP) to remove acid mist and ultra-fine particulate from the flue gas complete the emission reduction equipment. Siemens provided its first U.S. utility-scale WESP to ensure the facility meets its permitted emissions. The boiler island is also equipped with Foster Wheeler’s MBF coal mills. Table 2 summarizes many of the plant’s key performance parameters.
Table 2. Key Dallman 4 performance parameters. Source: CWLP
Instead of once-through lake cooling water, the plant uses a state-of-the-art plume-abated cooling tower, which will significantly reduce the chance of developing fogging conditions over the adjacent I-55 highway.
Coal ash disposal is subcontracted, and ash will be delivered to an abandoned mine located near the plant. The cost of ash disposal is $9.50 per ton for 2009, rising to $11/ton in 2011.
President Lincoln — a Springfield lawyer who rose to national prominence by representing Illinois in Congress before becoming president — may have been tall, but Dallman has him beat. At 440 feet, the new Dallman 4 stack is the second-tallest structure in Springfield, overlooked only by a Dallman 3 stack (Figure 5). Third runner-up is the combined stack for the first two units at Dallman. The State Capitol comes in a distant fourth.
5. The air is rare up there. The new Dallman 4 stack is the second-highest landmark in the City of Springfield and is higher than the State Capitol building. Courtesy: CWLP
That isn’t to say construction of the stack was easy. As Black & Veatch Vice President and Project Manager Les Rinck tells the story, volatile commodity prices and a tight subcontractor market put a lot of pressure on the team when bids came in way over budget. The bids received for construction of the stack were two to three times the original estimates, so KBV elected to self-perform the task, although neither company in the KBV joint venture had ever erected a stack before. However, they did have extensive experience in slip forming large concrete structures. A consultant from Austria assisted KBV in the planning and execution of the concrete shell slip forming operation. Tri-Clor Inc. was selected to provide detailed design and fabrication of the fiberglass stack liner and perform the erection with KBV. Tri-Clor also had no prior experience building a power plant stack liner — its expertise was in large fiberglass pipe and vessels. At the end of the day, construction of the concrete Dallman 4 chimney shell using slip form technology with a fiberglass liner was completed on schedule in only 28 days and 3 hours. The total cost of the stack and liner ended up being only 20% above the original estimate.
Emerson’s Ovation control system will monitor and control the new unit’s Foster Wheeler pulverized coal – fired boiler, as well as the burner management system, bottom ash handling, combustion control system, coal-handling system, and FGD and SCR systems (Figure 6). The Ovation system also interfaces with the Toshiba steam turbine controls. Emerson’s PlantWeb digital automation solution utilizes high-speed communications networks, intelligent field devices, and bus I/O technologies to increase plant operating efficiency and reduce long-term operation and maintenance (O&M) expenses. In all, Ovation will manage 2,500 hard I/O points and 2,500 soft I/O points. The controls were engineered and installed by the Power & Water Solutions division of Emerson.
6. The master controller. Emerson’s Ovation DCS system automates the plant’s many control tasks over a high-speed communication network. Courtesy: CWLP
"Dallman Unit 4 is being designed and built with efficiency and environmental stewardship in mind," said Brown, pointing out that, when completed, the new unit is expected to cost approximately 20% less to operate per megawatt-hour than the most efficient of the three existing Dallman units. "Emerson’s integrated digital automation system is a comprehensive solution that will not only contribute to improved operational efficiency and reduced costs, but will also support our utility-wide commitment to protecting the environment."
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