Materials problems in coal gasification and liquefaction
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THE
c o n v e r s i o n of coal into gaseous and liquid fuels is not new. T h e g a s i f i c a t i o n of coal for lighting s t r e e t s , h o m e s , and b u i l d i n g s was s t a r t e d c o m m e r cially in London in 1807. More than 11,000 g a s i f i e r s w e r e in o p e r a t i o n in the United States by the late 1920's.1 D u r i n g World W a r II, G e r m a n y achieved a p r o d u c t i o n r a t e of m o r e than 3.6 m i l l i o n m e t r i c tons p e r y e a r (MTPY) e q u i v a l e n t to 70,000 BPD of liquid fuels f r o m 18 h y d r o l i q u e f a c t i o n p l a n t s 2 The Sasol s y n t h e t i c - f u e l plant in South A f r i c a , which has o p e r a t e d for 20 y e a r s , c o n v e r t s coal into m o r e than 8.5 m i l l i o n s t a n d a r d cubic m e t e r s p e r day (SCMPD) of Syngas. C u r r e n t l y , a p r o g r a m is u n d e r w a y to d e s i g n and cons t r u c t Sasol II which will be four to five t i m e s l a r g e r and is scheduled to b e g i n o p e r a t i o n in 1980. 2 Although the b a s i c t e c h n o l o g i e s that a r e r e q u i r e d for coal c o n v e r s i o n have b e e n a r o u n d for half a c e n t u r y or m o r e , they had b e e n little developed in this country, l a r g e l y b e c a u s e up to now the a v a i l a b i l i t y of n a t u r a l gas as a fuel and the plentiful supply of p e t r o l e u m has made it u n e c o n o m i c a l to do so. However, now this nation is r e c o g n i z i n g a l i m i t e d and d e c r e a s i n g supply of p e t r o l e u m and n a t u r a l gas; t h e r e f o r e , a c r i t i c a l r e view of c o n s e r v i n g and p r o l o n g i n g c u r r e n t r e s e r v e s and of s u p p l e m e n t i n g them with a l t e r n a t e s o u r c e s is u n d e r w a y . F o r the p a s t decade or so, the s o u r c e s of e n e r g y in the U.S. have b e e n p r e d o m i n a n t l y oil and gas (44 and 31 pct r e s p e c t i v e l y ) with coal a c c o u n t i n g for 21 pct and all other s o u r c e s , i n c l u d i n g h y d r o e l e c t r i c and n u c l e a r p l a n t s , a c c o u n t i n g for 4 pct. In cont r a s t , coal a c c o u n t s for 75 to 80 pct of the n a t i o n ' s fossil-fuel resources. 3 The s i m p l e s t way to obtain e n e r g y f r o m coal is to b u r n it! Coal, however, b e c a u s e of its content of s u l fur and other p o l l u t a n t s , is c o n s i d e r e d to be a d i r t y fuel. R e m o v a l of the p o l l u t a n t s f r o m s t a c k gas when coal has not yet achieved full c o m m e r c i a l a c c e p t a n c e . N e i t h e r has g e n e r a t i o n of e l e c t r i c a l power f r o m dir e c t - f i r e d gas t u r b i n e s u s i n g f l u i d - b e d c o m b u s t i o n . A d i s c u s s i o n of the m a t e r i a l s p r o b l e m s in these, e n e r g y s y s t e m s is beyond the scope of this p a p e r . The e m p h a s i s of this p a p e r is to p r e s e n t an o v e r -
view of m a t e r i a l p r o b l e m s a s s o c i a t e d with the conv e r s i
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