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Show 1.1 Characteristics of the Allen Fossil Plant The Allen Fossil Plant (ALF) was installed in 1958-1959. It is comprised 9f 3 identical cyclone boilers, each designed to fire 101 tonlhr of high sulfur interior province bituminous coal in 7 cyclones and each coupled to a single turbine-generator. The boilers were also designed to fire natural gas, although that is not practiced at the ALF installation. Each boiler is designed to produce 2.1 x 106 lblhr of 2,500 psig/l050OP, and can generate reheat steam at 1050OP. Typical operating conditions are 2.0 x 106 lb/hr of 2400 psig/lOOOOP/1000OP. The original design documents identify a gross capacity of 330 MWe per unit, and a net capacity of 280 MWe per unit. The plant was converted from pressurized operation to balanced draft, and each boiler/turbine-generator unit was derated to about 275 MWe (gross). The original design documents identify a firing rate at maximum continuous rating (MCR) for each boiler 2,495 x 106 Btulhr based upon the original coal flow. The maximum overload rate (MOL) on a 4-hr basis is 2,520 x 106 Btulhr based upon coal flow in the original heat balances. The net station heat rate for the unit is approximately 9800 BtulkWh (Tillman et. aI., 1994; Foster Wheeler Environmental, 1995a). Fig 1 shows a schematic of a representative ALF boiler. The cyclones at ALF employ vortex feeders, with coal entering directly into the burner section and with primary air entering the scroll, and imparting the swirl to the rope of solid fuel. The boilers at ALF are controlled by Bailey Net 90 DCS systems. Electrostatic precipitators are used for airborne emission controls. The Allen Fossil Plant provides insights that can be transferred to many of the cyclone boilers in the U.S. Its switch to western coal is analogous to the switching performed by utilities in Minnesota, Wisconsin, and Indiana; although ALF uses a Utah bituminous coal rather than subbituminous coals. Its capacity is sufficient to represent some of the larger cyclone boilers, although it is not in the >600 MWe class of units such as the King Station of Northern States Power or the three large cyclone boilers of the Paradise Fossil Plant. 1.2 Characteristics of the Test Program at the Allen Fossil Plant Tests were conducted during August of 1994, and both August and December of 1995. The test program conducted at ALF consisted of the following elements: • characterizing the individual fuels to be burned, and characterizing the fuel blends used for each test • acquiring sufficient data from the control system to characterize main steam conditions and main steam flow; reheat steam conditions and reheat steam flow; feedwater conditions and flow; air temperatures including ambient air, air exiting the FD fans and entering the air heater, and air exiting the air heater and entering the windbox; flue gas temperatures at the exit of the economizer, at the exit of the air heater, and at the stack; excess O2 concentrations at the exit of the economizer,· and a variety of other parameters including generator output, house load, FD and 3 |