Metallurgical problems and opportunities in coal-fired steam power plants
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Metallurgical Problems and Opportunities in Coal-Fired Steam Power Plants
R. I. J A F F E E
E x t e r n a l constraints on the generation of electricity in s t e a m power plants that determine metallurgical r e s e a r c h and development include 1) the source of fuel, 2) environmental controls, 3) the economy of s c a l e , 4) efficiency of energy conversion, and 5) reliability of the power generating equipment. T h e s e are reviewed in the current time f r a m e . Econ o m i c and political factors dictate that coal and n u c l e a r fission are the m a j o r fuels for generation of electricity until the end of the century. Environmental constraints on SO2 emission dominate a g r e a t deal of current materials r e s e a r c h and development. Only a s m a l l percentage of available coal is low enough in sulfur t o meet new s o u r c e standards. Conversion of coal to a c l e a n gaseous, liquid, or solid fuel is replete with difficult m e t a l lurgical problems, chiefly in high temperature corrosion. T o compete with s t a c k gas desutfurization it is necessary t o burn the clean converted coal in more thermally efficient combined cycles, which requires development of high temperature industrial gas turbines. The fabrication problems of advanced air or water cooling of m e t a l hot components are traded off against the brittle design problems of c e r a m i c components. Removal of sulfur in the combustion stage in fluidized beds containing an SO2 aceeptor has many attractive features, but potential problems e x i s t in hot corrosion of the in-bed tubes and erosioncorrosion-fouling of expander turbines. The economy of s c a l e has increased power plant size to about 1200 MW, where further i n c r e a s e s seem t o have stalled because of metall u r g i c a l problems. Improvements in t h e r m a l efficiency from high s t e a m temperatures and pressures also have stalled, and even retreated, because of metallurgical b a r r i e r s . The main current effort in materials r e s e a r c h and development is a i m e d at improved r e l i a bility r a t h e r than efficiency. Two metallurgical opportunities to improve reliability are described in detail: titanium low p r e s s u r e turbine blades and l a r g e r o t o r forgings. A FTER spending most of my c a r e e r in nonferrous metallurgy at the Columbus Laboratories of Battelle Memorial Institute, working chiefly on titanium and refractory m e t a l s in aerospace applications, it was a refreshing and stimulating change t h r e e y e a r s ago t o
take on new responsibilities for the E l e c t r i c P o w e r R e s e a r c h Institute t o look at the applications of mat e r i a l s in power generating equipment. The predominant m a t e r i a l used in power generation is steel, although nonferrous alloys are used in condenser
T h e E d w a r d DeMille C a m p b e l l M e m o r i a l Lecture w a s e s t a b l i s h e d i n 1 9 2 6 a s a n a n n u a l lecture in m e m o r y o f a n d i n r e c o g n i t i o n o f t h e o u t s t a n d i n g s c i e
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