Original Date: 08/26/1996
Revision Date: 01/18/2007
Best Practice : Foster-Wheeler Steam Generating Plant
Construction of a new, steam-generating facility and modifications to increase the boiler capacity have resulted in annual Weirton Steel Corporation (WSC) savings exceeding $1.5 million. In the late 1970s, WSC lacked sufficient boiler capacity, bought fuel at record-high prices, and used 25 to 60-year-old boilers with serious maintenance problems. WSC was also burning off (flaring) and wasting large quantities of byproduct, blast furnace gas (BFG), while having to purchase additional fuel due to insufficient BFG burning capacity.
In 1980, the company solved these problems by building a new, cost effective Foster-Wheeler steam generating plant. The facility takes water from the nearby Ohio River and converts it into 600,000 lb-m/hour (gross) of superheated steam at 825 psi and 825°F, delivering 500,000 lb-m/hour for steel mill operations. Cost effectiveness of the Foster-Wheeler steam generating plant comes from several sources such as its ability to proportionately switch fuel mix from 95% BFG (5% natural gas) to 100% natural gas automatically.
Besides the automatic fuel mix capability, improved boiler efficiency resulted from two 60% capacity induced-draft and forced-draft fans on each boiler; heat traps that include both air heaters and economizers which provide more than 85% efficiency; low excess 02; and attemperators to control finished-steam temperature. Boilers have a complete National Fire Protection Association burner management safety system and are fully environmentally compliant.
Another cost-effective measure comes from the high water quality using a water treatment process to produce deionized water that provides less than 1% boiler blowdown. The neutralization system complies with EPA requirements, and the water treatment process is automated (except carbon filters) with a programmable computer.
In 1993, as an element of the company's Total Quality process, WSC benchmarked its operating and maintenance strategies for the Foster-Wheeler plant against those of Florida Power and Light. Following the benchmarking, WSC’s water plant capacity was increased 27% by using an improved ion exchange resin, resulting in an annual savings of $100 thousand. An additional $250 thousand in annual savings was achieved through increased capacity of the induced-draft fans’ turbine-steam admission valve at a cost of only $1 thousand per fan. A third improvement in plant capacity was achieved through the use of high pressure (20,000 psig maximum) water lasers to remove (BFG) residue which reduced off-line time by 50%, and provided savings of more than $750 thousand per year.
Further cost improvements have been realized at WSC through activation and enhancement of boiler pressure control (rather than flow control) to reduce purchased fuel costs, and through tracking and trending excess air control. These changes resulted in a combined, annual savings of an additional $375 thousand.
The company believes these process changes have provided insight to future opportunities which will yield savings approaching 10 times those achieved to date.
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