X-600 Steam Plant

The X-600 Steam Plant is a standard industrial steam plant which produces steam for process heat, building heat, and miscellaneous purposes such as steam cleaning. It does not generate electricity. The steam plant consists of three independent 158 million BTU/hr coal-fired boilers, each rated for continuous operation at 125,000 pounds of saturated steam per hour at 125 psig and at a temperature of 353° F.

The coal-fired boilers are of the moving-grate, spreader-stoker design. Each boiler has mechanical, cyclonic dust collectors with fly ash reinjection followed by electrostatic precipitators. Particulate emissions are monitored by continuous opacity monitors. Each boiler is totally independent of the other two, having its own duct, fans, ESP, stack, and opacity monitor.

Each boiler has an induced draft fan and a forced draft fan, both of which may be operated by electric motors or by steam turbines. Each boiler also has a high pressure blower for overdraft air and a low pressure blower to circulate cooling air around the stokers. Both of these blowers are electric only but plant air may be used to replace part of the capacity in the event of a motor failure.

The three boilers are connected to a 16" header. Steam is supplied to the plant through two 12" steam loops, known as the east and west loops. Condensate is returned to the steam plant through a condensate return line.

The steam plant burns bituminous coal from southern Ohio. Total consumption is approximately 50,000 to 60,000 tons per year. Coal is delivered to the coal yard by truck and may be delivered directly to the coal grates or to the coal yard. The coal is transported by conveyor or elevator to three coal bunkers in the top of the steam plant. It is delivered to the boilers through four chutes, one to each of four stokers at each boiler.

Two boilers are normally on line at a time with each running at 50 to 75 percent of capacity depending upon the season and the demand for process heat. The steam plant was designed with three boilers to provide an immediate replacement in the event one of the two operating boilers suddenly failed. The gaseous diffusion process requires large amounts of steam heat to vaporize the uranium hexafluoride (UF6) feed stock and to keep it in gaseous form throughout the process. The loss of steam for more than a few hours will cause the UF6 to solidify, resulting in great damage to the process equipment, particularly the UF6 compressors. The third boiler undergoes its annual overhaul while it is off line.

The steam plant has numerous ancillary systems such as water treatment, coal handling, ash handling, steam distribution, and condensate return and feed.

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