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Petrochemistry of Coal Ash Sla gs . 2 . Co rre l a t i on of Visc osi tywith Composition and Petrographic Class

Harold H. SchobertGrand Forks Energy Research Center

Box 8213, Universi ty Sta t ionGrand Forks, ND 58202

The Grand Forks Energy Res ear ch Cen ter (GFERC) of t h e Ehergy Rese arch andDevelopment Administration has reactivated a f ixed -bed s l a gg ing c oa l ga s i f i c a t io np i l o t p lan t which was formerly operated by th e Bureau of Mines. Design of t h ega s i f i e r , t he B ureau o f Mines t e s t r e s u l t s , and p r el im ina r y r e su l t s from the ERDAprogram have been documented (1-4).

A de t a i l e d s tudy of t he s l a gg ing ope r a t ion i s one as pe ct of t h e cu rr en t GFERCThe objec t iv e of t h i s s tudy i s t o develop a ccura te knowledgeilot plant program.of th e f low and hea t t r an sf e r behavior of t he s l ag , bo th t o improve opera t ion ofth e GFERC plant and t o sugges t des ign approaches fo r fu tu re gene ra t ion ga s i f ie r s .One of th e impor tan t pa ramete r s i n t h i s work i s t h e s l a g vi s c o s it y .The experimenta l determination of s l ag vi sc os i t y as a func t ion of tempera ture

i s a d i f f i c u l t p ro ce du re . Consequently, many e f f o r t s have been made t o d evelop ana pproac h t o c a l c u la t e t h i s r e l a t io nsh ip . The e qua t ions ge ne r a l ly propose d inc o r -porate one o r more terms which a re c a lc ula ted f rom th e sl ag composition.

The equation

has been sugges ted in severa l publ ica t ions (5 -7 ) f o r c a l c u l a t i n g v i s c o s i t y a s afunc tion of temperature. In t h i s e q ua t io n , T i s expressed in degrees Centigrade,and 2,n p o i s es . M and C a r e te rms ca l cu la t ed f rom th e s l ag composit ion , be ingfunc t ions of S O 2 , A1203, Fe20-3, and CaO con ten t .proposed fo r ca lcu la t ing C an d M . These e q u a ti o n s d i f f e r s l i g h t l y i n t h e v a l u eso f t h e c oe f f i c i e n t s o f t h e com pos it ion t e r m s . The work done by Watt and Fereday( 6 ) i s based on Br i t i sh coa ls , whi le th a t r epor ted by th e In s t i tu te of Gas Tech-nology ( 7 ) i s based on synthe t ic me l ts .

Var ious equ ation s have been

Attempts were made t o u se equatio n [ l ] f o r t h e c a l c u l at i o n o f v i s c o s i t i e s o fsome l i g n i t e a sh s l ag s f o r which exper imenta l v iscos i ty da ta w a s a v a i l a b l e a tGFERC.Bomkamp ( 7 ) were used.temperature range over which vi sc os i t y da ta was a va il ab le a t GFERC ( 8 ) .t h e r e s u l t s a r e g i ve n i n T a bl e 1.

Both t h e Watt-Fereday method ( 5 , 6 ) and th e modified equ ation s suggested byA t e s t temperature was se le cte d f rom t h e center of t h eSome of

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TABLE 1. Cal cul at ed Val ues of Li gni t e Sl ag Vi scosi t i es. A/Li gni t e Sl ag Temper at ure Method lE Met hod 2c/ Expt '1 Val ueBaukol - Noonan 1175' 197 11, 600 42I ndi anhead 1260 21 2, 276 60Vel va 1385O

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The computed values of C and M were used as i n p u t d a ta f o r a m u l t ip l e l i n e a rregress ion ana ly s is f o r th e development of equa t ions re la t i n g C and M t o s la gcomposit ion. Repeated computer t r i a l s fa i l ed t o produce a s a t i s f a c t o r y fit oft h e d a t a . A s a r e s u l t , a t t e n t i o n w a s then focused on performing regressiona na lyse s f o r s l a g s on ly o f a s in g le pe t rog r a ph ic c l a s s .c l a s s i f i c a t io ns and t er m ino logy r e f e r t o i gne ous roc k pet rog ra phy , r a t he r t ha n t ocoal petrography.)

( I n t h i s p ap er p e t ro g r ap h i c

The t e s t s lags were d iv ided in to two groups on the bas is of s i mi la r i ty ofcomposition: Baukol-Noonan, Disco-Flux, and Indianhead i n t h e f i r s t group; andBentinck , Cronton-19, Cronton-27, Disco, and Thoresby i n t h e second. De ta ile dpetrographic analy ses were done fo r Indianhead and Thoresby sla gs , th e composit ionsof which a r e g iven i n t h e appendix.t h e C.I.P.W. method ( 9 ) , fol lowing th e procedure o utl ine d by Johannsen (10).This procedure i s a taxonomic method fo r comparing chemical analyses from ape t r o log ic a l a spe c t . The a na ly t i c a l da t a i s r e c a l c u la t e d i n t e rm s of a s e t o fstand ard mineral molecules.and Thoresby t o be fe ld spa r normative .

The pe t r og r a ph ic c l a s s i f i c a t ion was done by

Indianhead s la g was found t o be pyroxene normative

Cor re la t ion co ef f ic i en ts were ca lcu la ted between each of th e major s la gcomponents and th e va lu es of C and M , f o r b o t h c l a s s e s o f s l a g . The c a l c u l a t i o n swere done us ing a stan dar d li n ea r co rr el at io n computer program. This work wasdone so th a t th e re s u l t s would se rve as a guide t o which s l ag components mightbe s t be used i n a mult ip le reg ress io n an a ly s is f or developing equa t ions to CalCU-l a t e C and M.Table 4. The computed va lue s o f t h e c o r r e l a t ion c oe f f i c i e n t s are g ive n i n

TABLE 4. Linear Co rre lat io n Coeff ici ent s Between Sla g Compositionand Computed Values of C and M.mox ene-n orma tive Slags Feldspar-normative SlagsComponent C M C M

i02 -. 69 .444M2O3 .554 -.485Fe203 - e 996 .999MgO .209 - 129K20 -.589 .521

CaO .360 -.283Na2O -.140 * 059

.681 .094-.573 .570.168 .255.030 .140-.76O .940

-.019 -.512-. 95 .200

Mul t ip le l in ea r regress ion a na lys is of t h e fe ldsp ar normative group deve lopedth e fo l lowing equa tions :

c = -4.5413 - .2158 (K20) + .0883 (Si021 + .0091 (Al2O3) [31M = 0.3676 + .0783 (K20) - .0043 (M 203 ) [41

I n th e se e qua t ions th e c onc e n t ra t ion terms use th e a c tu a l weigh t pe r c e n t va lue sdetermined from th e chemical ana lys is . .The v iscos i ty- tempera ture re l a t i on sh ip fo r Cronton-19 s la g was ca lcu la t ed byThe a pp r op r i a t e a na l y t i c a lub s t i tu t in g equa tions [31 and [41 in to equa t ion [ l] .d a ta f o r t h i s s l a g a r e 3.5 p c t K20, 43.6 pct Si02, and 24.6 pct A12O3.

shows the experimental (11)and c a l c u la t e d v i s c os i ty c u rve s.F igure 1

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Although only l im i t ed da ta a re ava i la b le fo r th e pyroxene normative s l a gs , ar e g r e s sion a na lys i s was done to f i t C and M va lue s t o F ez0t h e h igh cor r e la t io n between the se pa ramete rs .

content because ofEquations 751 and [6 ] resu lted .

C = 0.8143 (Fe2O3) - 4.8749 [51M = 0.1135 (Fe2O3) - .5219 t61

The viscosi ty- temperature curve for Indianhead slag (Fe2O3 = 11.0 p c t ) c a l c u l a t e dfrom equations [5] , [ 6 ] , and [ l ] , i s given in Figure 2.

These resul ts demonst ra te t h a t t h i s approach produces improved re su l t s fo rt h e s p e c if i c s l a g s s t u d i e d t h u s f a r . It i s s ug ge st ed t h a t c l a s s i f i c a t i o n o fsl ag s by a petrog raphi c procedure may be more us ef ul th an othe r methods f o r theproduction of v i s c o s i t y e f f e c t s .

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REFERENCESG.H. Gronhovd, A.E. Harak, W.R. Kube, and W.H. Oppelt. "Design and I n i t i a lOpera t ion of a S laggin g , F ixed-Bed, P ressure Gas i f ica t ion P i l o t P lan t . "Bureau of Mines R I 6084 ( 1 962 ) .G.H. Gronhovd, A.E. Harak, M.M. Feg ley , and D.E. Sev erso n.Bed Gasif ica t io n of North Dakota Lign ite a t Pre ssure s t o 400 Psig."Bureau of Mines R I 7408 (1970).R.C. E l l m a n and B.C. Johnson.Forks Energy Resea rch Center. "Gas Symposium, Chicago, I L , October 1976.R.C. Ellman and H.H. Schober t . "Pi lot Plant Operat ion of a Fixed-Bed SlaggingGasi f ie r . "So ci et y, New Orle an s, LA , March 1977.B r i t i sh C oal U t i l i z a t io n R esea rc h Assoc ia t ion , Annual Report (1963).J . D . Watt and F. Fereday.Ashes of B ri t i sh Coals:Rela t ion to Slag Composit ion."I n s t i t u t e of Gas Technology.Technical Data Book."Report F61730-21 ( 1 976 ) .G.H. Gronhovd. P r iv a te communication.H.S. Washington. "Chemical Analyses of Igneous Rocks." U.S. Geo log icalSurrey Profess ion a l Paper 99 (1917) .A. Johansen. "A De sc rip ti ve Petrography of Igneous Rocks." The Un ive rsit yof Chicago Pr es s, Chicago, I L (1939) .H.R. Hoy, A.G. Roberts , and D .M . Wilkins. "Some In ve st ig ati on s wit ha Small Cyclone Combustor."

U.S.

"Slagging Fixed-U.S.

"Slagging Fixed-Bed Ga si fic at io n a t t h e GrandP r ese nted a t t he E igh th S yn the t i c P ipe l ine

Presented a t t h e National Meeting of t h e American Chemical

"The Flow P ro pe rt ie s of Sl ag s Formed from t h eP a r t 1: Viscosity of Homogeneous Liquid Slags inJ . I n s t . F u e l , 42, 99 (1969) .

"Preparation of a C o a l Conversion SystemsEnergy Research and Development Administration

J . I n s t . F u e l , 2, 41 (1958).

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