TREATMENT OF REFRACTORY OXIDES IN HF-PLASMA REACTORS

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TREATMENT OF REFRACTORY OXIDES IN HF-PLASMA REACTORS

A. Bakhvalov, S. Dresvin, T. Levitskaya, G. Paskalov, A. Philippov

To cite this version:

A. Bakhvalov, S. Dresvin, T. Levitskaya, G. Paskalov, A. Philippov. TREATMENT OF REFRAC-

TORY OXIDES IN HF-PLASMA REACTORS. Journal de Physique Colloques, 1990, 51 (C5), pp.C5-

19-C5-25. �10.1051/jphyscol:1990503�. �jpa-00230800�

TREATMENT OF REFRACTORY OXIDES IN HF-PLASMA REACTORS

A.O. BAKHVALOV, S.V. DRESVIN, T.N. LEVITSKAYA*, G.Z. PASKALOV and A.K.

PHILIPPOV*

Laboratory of E1ectrotechnological and Plasma Installations. Leningrad Polytechnical Institute, ulitsa Polytechnicheskaya 29, Leningrad :95251, U.S.S.R.

Special Design Office of Analytical Instrument Engineering of USSR Academy of Sciences. Prospect Ogorodnikova 26, Leningrad 198103, U.S.S.R.

Rbsumb : Des rbsultats thboriques et expbrimentaux relatifs au traitement de Si02,Mg0, W... dans un plasma inductif pression atmosphbrique sont prbsentCs. L'optimisation des paramhtres permet d'obtenir une efficacitb maximale de 0,6 0,7 avec un taux de 1 B 50%pm. Les rbultats de mesure sur les caractbristiques thermophy- siques et dynamique de l'bcoulement sont prbsentbs.

ABSTRACT

R e s u l t s o f t h e o r e t i c a l and e x p e r i m e n t a l s t u d i e s o f SiO 2 A1&Si.HgO.W a n d some o t h e r m a t e r i a l s t r e a t m e n t i n i n d u c t i o n t y p e h i gh-f r equenc y p1 asma under atmospher

i

c p r e s s u r e are p r e s e n t e d . Key s t u d y o b j e c t i v e

-

o p t i m i z a t i o n o f plasma i n s - t a l l a t i o n o p e r a t i n g modes w i t h maximum e f f i c i e n c y

-

^{0.8 -0.7;}

s p h e r o i d i z a t i on e x t e n t -90-99%. s i z e of t r e a t e d p a r t i c l e s 1 -500 rnkm. Di a g n o s t i CS of thermophysi cal and gasodynami c a l plasma r e a c t o r s p e c i f i c a t i o n s h a s been p r e s e n t e d .

1. I NTRODUCTT ON

Many i m p o r t a n t t e c h n o l o g i c a l p r o c e s s e s of s y n t h e s i s , treat- ment and r e f i n i ng of d i s p e r s i o n materials may b e implemented by u s e of HF-plasma t o r c h e s . V a r i e t y of mode v a r i a n t s and d e s i g n p e c u l i a r i t i e s of HF-p1 asma g e n e r a t o r s m a k e s p o s s i b l e . on t h e one hand. t o m a k e p r a c t i c a l 1 y a n y t e c h n o l o g i c a l p r o c e s s e f f e c t i v e by c h o o s i n g a p p r o p r i a t e HF-plasma g e n e r a t o r s . On t h e o t h e r hand, a b s e n c e of HF-p1 asma g e n e r a t o r s uni v e r s a 1 1 t y i mpo- se r a t h e r h i g h requirememts t o t h e l e v e l of t h i s equipment managing. Apart from t e c h n i c a l p a r a m e t e r s i n is i m p o r t a n t t o t a k e i n t o a c c o u n t e f f i c i e n c y of plasma p r o c e s s C 1 3 . I n p a r t i

-

c u l a r . t h e h i g h e s t r e s u l t s i n s p h e r o i d i z a t i o n p r o c e s s e f f i c i

-

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990503

COLLOQUE DE PHYSIQUE

e n c y of SiO2.N&i.M~0.W and o t h e r m a t e r i a l s a r e a c h i e v e d i n HF-plasma r e a c t o r s . T h i s is r e l a t e d w i t h a p o s s i b i l i t y of producing l a r g e plasma volumes BOO-1000 cu. S W w i t h low s p e e d of plasma jet /VpL=l-50 m/s/ p r a c t i c a l l y w i t h a l l g a s e s /Ar.He.N , a i r . p r o p a n e / , i n c l u d i n g hudrogen L E ] .

2. EXPERI MENTAL METODS

F i g u r e 1 schemati c a l l y p r e s e n t s t h e e x p e r i m e n t a l i n s t a l l a - t i o n . comprising: high-f r e q u e n c y g e n e r a t o r /l / w i t h power o u t - p u t of 6 0 kW and f r e q u e n c y 1 .76 MHz /some p r o c e s s e s w e r e h e l d u s i n g g e n e r a t o r w i t h 10 kW power o u t p u t and 13.33 MHz/; induc- t i o n plasma g e n e r a t o r

e/

w i t h q u a r t z d i s c h a r g e chamber. which c o n s t r u c t i o n a l l o w s t o o p e r a t e r e l i a b i l l y i n t h e r a n g e of p1 asma-f ormig g a s consumption /air. n i trOgen, a r g o n / from 201 /m t o 500 l / m i n a x i a l a n d v o r t e x f e e d ; r e a c t o r D / ; two f e e d e r s /4/. c a r r y i n g o u t f e e d of t r a n s p o r t i n g g a s /at powder treament w i t h d i s p e r s i o n of t h e powders-up t o 60 m k w and w i t h o u t i t /at powder t r e a m e n t w i t h d i s p e r s i o n more t h a n 6 0 m k w ; c o l l ec- t i n g u n i t /5/ u s i n g c l o t h o r metal f i l t e r s .

F i g . 1

-

Schematic d i a g r a m of t h e e x p e r i m e n t a l s e t - u p .

Control and measurments of t h e i n s t a l l a t i o n and t e c h n o l o - g i c a l p r o c e s s d i f f e r e n t p a r a m e t e r s h a s been c a r r i e d o u t i n a c c o r d a n c e w i t h s p e c i a l a l g o r i t h m . w i t h a l l o w s t o o p t i m i z e t h e o p e r a t i o n of HF-plasma i n s t a l l a t i o n / c r i t e r i u n

-

minimum of power l o s s e s / and t h e t e c h n o l o g i c a l p r o c e s s / c r i t e r i u m

-

maxi mum o u t p u t of good product/. From t e c h n o l o g i c a l p o i n t of view i t is d i s i r a b l e t o h a v e maximum thermal e f f i c i e n c y of p1 asma g e n e r a t o r .

F i g u r e 2 p r e s e n t s some modes of plasma gene-

r a t o r o p e r a t i o n a t d i f f e r e n t methods of g a s f e e d t o plasma g e n e r a t o r .

Fig. 2

-

C o e f f i c i e n t of performance of t h e p l a s m a t r o n V S d i s c h a r g e power a t v a r i o u s g a s f e e d a n g l e s

Speci a1 gas-f ormi ng d e v i c e a1 l owed t o change t h e

a n g l e of g a s f e e d /a/ from 0 t o 90 b o t h y i n asyazimuth and i n p l a c e a n g l e . The most e f f i c i e n t mode h a s been observed a t a=45-50

.

I n t h a t c a s e plasma g e n e r a t o r e f f i c i e n c y i s a b o u t 85-90%. The plasma jet l e n g t h depended on power i n d i s c h a r g e Pp and consumption of p1 asrna-f ormi ng g a s G p and i n our expe- r i m e n t s i t r a n g e d from 100 t o 600 mm a t mean s e c t i o n 80 mm.

Using r e s u l t s o f c a l c u l a t i o n s of movement and h e a t i n g t h e p a r t i c l e s i n plasma a c c o r d i n g t o a model which t a k e s i n t o a c c o u n t e l e c t r o - and gasodynamics of t h e HFI - d i s c h a r g e , con- d i ti o n s of mixing c o l d / t r a n s p o r t i ng g a s w i t h t h e plasma j e t . i n t e r p h a s e exchange, o p t i m a l o p e r a t i n g modes f o r HF-instal l a- t i o n h a s been chosen. as w e l l a s method. p l a c e and a n g l e of d i s p e r s i o n material i n p u t i n t o t h e plasma jet C 3 1 . The o p t i - m i z a t i o n has been c a r r i e d o u t i n a c c o r d a n c e t o c r i t e r i u m of maximum e f f i c i e n c y and o u t p u t of t h e p r o c e s s . A s a r e s u l t s of t h e o r e t i c a l a n d e x p e r i m e n t a l sr udi e s o p t i m a l t e c h n o l o g i c a l scheme of s u c h d i s p e r s i o n m a t e r i a l S t r e a t m e n t as Si02. MgO, A Z C O M

.

^N&i

.

^{W is} developed. F i g u r e 3 p r e s e n t s depedance of

3

s c h e r o i d i z a t i o n d e g r e e

-

a / W a-amount o f s p h e r o i d i z i ded sph-

mater i a1

.

A-amount of i n i ti a1 mater i a1 /from m a s s l oadi ng of plasma j e t Gm w i t h power i n t h e jet

-

40 KW.

COLLOQUE DE PHYSIQUE

F i g . 3 S p h e r o i d i z a t i o n d e g r e e o f M@ _{V S} p r o d u c t i v i t y C e x p e r i

-

m e n t a l c o n d i ti o n s Pp=SOKW; f =l , i'6MHz ; a i r G = l l /S>.

I n c r e a s e of o u t p u t o f s p h e r o i d i z a t i on p r o c e s s a t s a t i s- f a c t o r y e f f i c i e n c y ^/ nsOh=80Yd i s p o s s i b l e w h i l e u s i n g more p o w e r f u l p1 asma i n s t a l l a t i o n s . Type o f t r e a t e d mater i a 1 d e t e r

-

mines dynamics of i t s h a t i n g i n t h e plasma. For example. f i g u r e 4 p r e s e n t s d e p e n d a n c e of Si02 and NaBSi p a r ti c l es t e m p e r a t u r e on axial c o o r d i n a t e Z.

D i s t a n c e l e n g t h ZCsm)

F i g . 4 P a r t i c l e h e a t i n g dynamics 1 - SLOP 2 - MaBSi

s u m p t i o n Gp=l g / s - f o r Si02; C s t r = O . 65 g / s ; Gp=O:5 g / s - f o r NaBSi Plasma-forming g a s

-

a r g o n + a i r ,power i n t h e discharge-7KW.

f r e q u e n c y 13.56 MHz/. A f t e r t r e a t m e n t c h e m i c a l composotion of t h e i n i t i a l m a t e r i a l i s changed s i g n i f i c a n t l y / f u s i b l e i m p u r i t i e s u s u a l 1 y v a p o u r i z e / . I n t a b l e s 1 and 2 below SiO

2' NaBSi chemical d a t a are p r e s e n t e d as w e l l a s s p h e r o i d i z a t i o n e x e n t a t d i f f e r e n t t h e r m a l t r e a t m e n t c o n d i t i o n s . Range of d i s- p e r s i o n change of m a t e r i a l . t r e a t e d i n plasma. is d e t e r m i n e d by t h e amount of i n i t i a l m a t e r i a l a n d t h e r e g i m e of t h e t r e a t m e n t .

T a b l e 1 Chemical c o m p o s i t i o n of s o d i um-borosi l i c a t e g1 a s s

...

I n i t i a l A f t e r plasma t r e a t m e n t m01

.

^% S p e c i f i c s u r f a c e m01

.

^% S p e c i f 1 c s u r f a c e

...

T a b l e 2 E f f i c i e n c y of s p h e r o i d i z a t i o n p r o c e s s f o r NaBSi

D p t . g. G vor. Gas t y p e Sph.

D r G ax

...

l. 0.30 7 a r g o n 0.3

2. 0 . 3 4 6 a r g o n 0 . 3

3. 0. 40 7 a r g o n 0.5

4. 0.40 6 a r g o n + a i r l : 1 0.7

5. 0.60 9 a r g o n 0.6

6. 0.60 l 2 a r g o n + a i r 1:l 0.99

DpL.g.Dr

-

d i a m e t e r s o f plasma g e n e r a t o r and r e a c t o r Guor.Gox

-

g a s consumption a t v o r t e x and a x i a l s u p p l y o f g a s i n t o t h e d i s c h a r g e chamber.

F i g u r e 5 p r e s e n t s a s a n example d i s t r i b u t i o n o f s p h e r o i d i z i

-

ded SiO

P

a r t i c l e s i n a c c o r d a n c e w i t h t h e r s i z e a f t e r p r e c i

-

se f r a c t i o n i n g /2 s a m p l e s / t h e d a t a a r e r e c i e v e d u s i n g l aser l i g h t d i f f u s i o n i n s t r ument LS-01 .

COLLOQUE DE PHYSIQUE

P a r t i c l e s i z e C m k d

F i g . S Si02 s p h e r o i d i z a t i o n p a r t i c l e s i z e d i s t r i b u t i o n Diagram of d i s t r i b u t i o n of p l a s m a - t r e a t e d Si02 d i s p e r s i o n c o m p o s i t i o n w i t h s i z e o f 1 0 0 mkm i s p r e s e n t e d i n f i g . 6

P a r t i c l e s i z e Cmkd

F i g . 6 SiO p a r t i c l e s i z e d i s t r i b u t i o n a f f e r plasma t r e a t m e n t 2

E l e c t r i c power consumption f o r p r o d u c t i o n of 1 kg o f 5f 0 2

/ vs* ^{=90-997d =l 0 k W/hr}

.

^{f o r NaB5i / r )} _{S P ~} ^{'95-997- =4 k W/hr}

.

^{f o r}

m0

^{/Vsph = 807d} = l 2 kW/hr.

')soh =SE-95%. e l e c t r i c power c o n s u m p t i o n

-

8-9 kW/hr/kg.

A L C O M 3 d i s p e r s i o n t r e a t m e n t i n a i r p l a s m a / p a r t i c l e s i z e 10-200 mkm/ a l l o w e d t o r e c i e v e AL 2 3 0 power /a-phase/ o f t h e same d i s p e r s i o n w i t h c o n v e r s i o n e f f i c i e n c y SW% a n d s p h e r o l d i

-

s a t i on e x t e n t 95-99%. P r o d u c t i v i t y o f ALCOH>3 t r e a t m e n t pro- c e s s i n plasma i s s i m i l a r t o NgO t r e a t m e n t .

REFERENCES

1. P1 asma t e c h n o l o g y i n m e t a l l u r g i c a l p r o c e s s i n g . J

.

F e i nman

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Edi t o r . I r o n a n d Steel Soc.

.

^{I nc.}

^,

^{l Q87}

2. A. V. Donskoi ,V. _M. Go1 d f ar b a n d V. S. K1 ubni ki n

,

P h y s i c s and Technology o f Low-Temperature P1 asmas.

.

^{S. V.} D r e s v i n , l Q72 E n g l i s h e d i t i o n t r a n s l a t e d by T. Cher on a n d e d i t e d by H. V. E c k e r t

.

Iowa State Univ. P r e s s . 1 9 7 7

3. Bakhvalov A. 0. , D o b r i n s k a j a T. A. e t a l . Motion a n d h e a t l n g of f i n e d i s p o s e d m a t e r i a l s l n a p l a s m a jet / F i r s t E u r o p l a n C o n g r e s s o n t h e r m a l P1 asma and M a t e r i a l B e h a v i o u r a t h i g h t e m p e r a t u r e s

.