UTILITIES PRESS PROGRAMS TO USE MORE COAL

American Electric Power (AEP), Columbus, Ohio, has begun the first combined cycle generation of electricity from its Tidd pressurized fluidized bed combustion (PFBC) demonstration plant, a step toward full load operation.

Meanwhile, Western Energy Co., Butte, Mont., joined with a unit of Northern States Power Co., Minneapolis, to demonstrate and market technology for improving sub-bituminous and lignite coals. The partnership plans to build a coal upgrading plant at Western Energy's Rosebud coal mine near Colstrip, Mont.

TIDD PLANT PROJECT

The 70,000 kw AEP demonstration plant at Ohio Power Co.'s Tidd plant on the Ohio River near Brilliant, Ohio, is a flagship project of the U.S. Department of Energy's Clean Coal Technology program.

PFBC involves burning coal with dolomite. Sulfur dioxide released by burning coal is captured by the dolomite during combustion, so it does not need flue gas scrubbers.

The process burns coal in a churning or fluidized bed inside a combustion chamber that operates at a pressure of 175 psi.

Fluid properties of the bed result in high combustion and sulfur removal, and the high pressure permits power to be generated from a gas turbine cycle or steam turbine cycle, said James J. Markowsky, senior vice-president and chief engineer for AEP Service Corp., a subsidiary. The plant will burn 30 tons/hr of coal at full load.

DOE is providing $60.2 million of the $185 million program cost, and the Ohio Coal Development Office is providing $10 million. Construction got under way in April 1988, although AEP said it has been developing PFBC technology since 1976.

The technology has the potential to meet government emission requirements, with advantages over scrubbers such as greater efficiency, and lower capital and operating costs, AEP officials say.

PFBC ADVANTAGES

With the PFBC process, sulfur removal is expected to meet or exceed 90%, regardless of the type of coal used, said Robert Gentile, DOE assistant secretary for fossil energy.

"Commercial development of the PFBC process will permit utilities to continue to burn high sulfur coal such as that from Ohio and the northern panhandle of West Virginia," he said.

The required combustion temperature of 1,580 F. reduces nitrogen oxide emissions to half those of conventional coal fired boilers, and ash byproducts from PFBC are easily removable dry granules, Markowsky said. Scrubbers do not reduce nitrogen oxide emissions and produce sludge, not ash.

DOE and AEP expect the plant to become fully operational in early 1991, and plan for the Tidd demonstration program to continue for 3 years afterward.

AEP has begun preliminary engineering and design for a 340,000 kw plant, which it says would be the world's largest and the first commercial scale PFBC plant in the U.S.

Options are to either repower its Philip Sport plant in New Haven, W.Va., which would begin operating in 1996, or build a new plant in West Virginia, which would start up in 1998. AEP expects to burn 50 million tons of coal this year, accounting for about 90% of its total power generation.

ROSEBUD PLANT

The partnership of Western Energy and NRG Group, Rosebud SynCoal Partnership, will build the Colstrip coal conversion plant. DOE's Clean Coal I technology program will finance half the $69 million cost for 3 years.

Rosebud SynCoal says its conversion process will improve the properties of coal from Colstrip mines to less than 5% moisture, 0.6% sulfur, and more than 11,500 BTU/lb heating value, from 25% moisture, 1 %sulfur, and 8,600 BTU/lb. The converted coal will comply with Environmental Protection Agency sulfur dioxide emission standards of 1.2 lb/MMBTU.

Rosebud SynCoal will begin construction in early 1991, with start-up planned in 1992. The plant will produce about 300,000 tons/year of upgraded synthetic bituminous coal.

Western Energy will manage and operate the plant under a separate contract with Rosebud Syncoal, which plans to develop other projects, eventually producing as much as 3 million tons/year of upgraded synthetic coal.