biomass fuel chemical analysis

8/10/2019 Biomass Fuel Chemical Analysis

1/11

I[~ U TNEER H

mE , w N

0016- 2361( 95) 00142- 5

uel Vol. 74 No. 12, pp. 1812-1822, 1995

Copyright 1995 Elsevier Science Ltd

Printed in Great Britain. All rights reserved

0016-2361/95/ 9.05 + 0.00

I n f l u e n c e o f m i n e r a l m a t t e r o n b i o m a s s

p y r o l y s i s c h a r a c t e r i s t i c s

K . R a v e e n d r a n , A n u r a d d a G a n e s h a n d K a r t i c C . K h i l a r t

*Energy Systems Engineering, Dep artment of Mech anical Engineering,

tDepartment o f Ch emical Engineering, Indian Insti tute of Technology, Bomb ay-400 076,

India

Received 14 October 1994)

Studies on wo od and tw elve oth er types of biomass show ed th at in general, deashing increased the volatile

yie ld, ini tia l deco mpo sit ion temperatu re and ra te of pyrolys is . H owe ver , coir pi th, gro und nut shell and r ice

husk showed an increase in ch ar yield on deashing, which is a t t r ibuted to their high l ignin, potass ium an d

zinc conte nts. These results were supp orte d by studies on salt- impregnated, acid-so aked an d synthetic

biomass . A cor rela t ion was deve loped to pred ict the influence o f ash on volat i le yie ld. On deashing, l iquid

yield increased and gas yield decreased for all the biomass studied. The active surface area increased on

deashing. The heating value of the liquid increased, whereas the increase in char heating value was only

marginal.

Keywords: biomass; p yrolysis; mineral m atter)

B i o m a s s i s n o w w e l l r e c o g n i z e d a s a p o t e n t i a l r e n e w a b l e

s o u r c e o f e n e r g y . T h e r m o c h e m i c a l c o n v e r s i o n o f b i o -

m a s s i s o n e o f t h e m o s t c o m m o n a n d c o n v e n i e n t ro u t e s

f o r c o n v e r s i o n i n t o e n e r g y . T h i s i n c l u d e s c o m b u s t i o n ,

g a s i f i c a t i o n , l i q u e f a c t i o n a n d c a r b o n i z a t i o n . I n a l l t h e s e

p r o c e s s e s , p y r o l y s i s p l a y s a k e y r o l e i n t h e r e a c t i o n

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

p r o d u c t d i s t r i b u t i o n , c o m p o s i t i o n a n d p r o p e r t i e s .

I n t h e l a s t t w o d e c a d e s , e x t e n s i v e s t u d i e s h a v e b e e n

c o n d u c t e d t o u n d e r s t a n d t h e c o m p l e x i t y o f p y r o ly s is . T o

o b t a i n o p t i m a l c o n d i t i o n s f o r t h e d e s ir e d p r o d u c t s , m u c h

w o r k h a s g o n e i n t o s t u d y i n g t h e e f fe c ts o f p r o c e s s

v a r i a b le s a n d t h e p r o d u c t d i s t r i b u t i o n . T h e e f fe c t o f

f e e d s t o c k p r o p e r t i e s h a s r e c e n t l y b e e n i d e n t i fi e d a s o n e o f

t h e k e y r e s e a r c h a r e a s 1. T h i s p a p e r r e p o r t s t h e r e s u l t s o f

s t u d ie s o n t h e e f f ec t o f m i n e r a l m a t t e r p r e s e n t i n b i o m a s s

o n t h e p y r o l y s i s c h a r a c t e r i st i c s , p r o d u c t d i s t r i b u t i o n a n d

p r o d u c t p r o p e r ti e s .

D i f f e r e n t b i o m a s s f u e l s c o n t a i n m i n e r a l m a t t e r i n

v a r i o u s a m o u n t s . F u e l s s u c h a s w o o d a n d c o c o n u t s h e l l

c o n t a i n < 1 w t w h e r e a s s tr a w a n d h u s k s c o n t a i n u p t o

2 5 w t . G e n e r a l l y t h e m a i n e l e m e n t al c o n s t it u e n t s o f

b i o m a s s m i n e r a l s a re S i, C a , K , N a a n d M g , w i t h s m a l l e r

a m o u n t s o f S, P , F e , M n a n d A 1 . t h e se c o n s t i t u e n t s o c c u r

a s o x i d e s , s i l i c a t e s , c a r b o n a t e s , s u l f a t e s , c h l o r i d e s a n d

p h o s p h a t e s . T h e i n f l u e n c e o f c o m p o s i t i o n o n a s h

d e f o r m a t i o n a n d f u s i o n t e m p e r a t u r e s f o r v a r i o u s b i o -

2 3

m a s s h a s b e e n st u d i e d b y O s r n a n . G a n e s h s t u d i e d th e

i n f l u e n c e o f si l ic a i n ri c e h u s k a n d r i c e s t r a w o n t h e i r

c o m b u s t i o n a n d g a s i fi c a ti o n c h a r a c t e ri s t ic s a n d r e p o r t e d

t h a t a b o v e 1 1 4 6 K , s i l i c a i n b i o m a s s t r a p s t h e c a r b o n

p a r t i c l e s , m a k i n g i t u n a v a i l a b l e f o r c o n v e r s i o n .

T h e c a t a l y t i c ro l e o f m i n e r a l m a t t e r i n c h a r f o r m a t i o n

h a s a l s o o f t e n b e e n r e p o r t e d . S h a f i z a d e z e t a l . 4 f o u n d

t h a t i n o r g a n i c s a lt s s u p p r e ss t h e f o r m a t i o n o f t a r a n d

f a v o u r c h a r - f o r m i n g s e c o n d a r y r e a c t i o n s . F e l d m a n n

e t a l . s

f o u n d t h a t m i x i n g o f w o o d a s h o r c a l ci u m o x i d e

w i t h w o o d i n c r e as e d t h e y i e l d o f li q u i d p r o d u c t s . T h e

p y r o l y s i s s t u d i e s c o n d u c t e d b y G r a y

e t a l . 6

o n d e a s h e d

w o o d w a s t e s h o w e d 9 2 i n c r e as e i n t a r y i e ld a n d 3 4

a n d 3 3 r e d u c t i o n i n a q u e o u s a n d g a s e o u s p r o d u c t s

r e s p e c t i v e l y . M a d o r s k y e t a l . 7 s h o w e d t h a t a d d i t i o n o f

0 . 1 4 N a O H c o u l d in c r e a se t h e c h a r y i e ld b y u p t o 4 .

Es s ig

e t a l . 8

d e m o n s t r a t e d a 2 3 5 i n c r ea s e i n c h a r y i e ld

o n a d d i t i o n o f 0 . 1 N a C 1 t o c e ll u lo s e . T h e s e s t u d ie s

i n d i c a t e t h a t s m a l l a m o u n t s o f i n o r g a n i c m a t e r i a l , a s i s

p r e s e n t i n t h e b i o m a s s , a r e s u f f i c i e n t t o a l t e r t h e p y r o l y s i s

b e h a v i o u r t o a l a rg e e x t e n t .

H o w e v e r , m o s t o f t h e s tu d i e s r e p o r t e d p e r t a i n t o

w o o d y b i o m a s s , a n d t h e in f l u en c e o n p r o d u c t p r o p e r t i e s

r e m a i n s u n i n v e s t i g a t e d . T h e i n v e s t i g a ti o n s r e p o r t e d h e r e

w e r e a i m e d t o w a r d s u n d e r s t a n d i n g t h e i n fl u e n c e o f a s h

o n p r o d u c t d i s t r i b u t i o n a n d t h e i n d i v i d u a l p r o d u c t

c h a r a c t e r i z a t i o n .

E X P E R I M E N T A L

S a m p l e s e l e c t i o n a n d p r e p a r a t i o n

F e e d s t o c k p r o p e r t i e s .

T h i r t e e n c o m m o n l y a v a i l a b l e

t y p e s o f b i o m a s s i n t h e B o m b a y r e g i o n w e r e s e le c te d .

T h e i r p r o x i m a t e a n a l y se s , u l t i m a t e a n a l y s es , h e a t i n g

v a l u e s a n d b u l k d e n s i t i e s a r e p r e s e n t e d i n

T a b l e 1

a n d

t h e i r c o m p o n e n t a n a l y s e s i n

T a b l e 2 .

T h e i r a s h c o m -

p o s i t i o n s , d e t e r m i n e d b y t h e s t a n d a r d g e o l o g i c a l

r o c k a n a l y s i s p r o c e d u r e 9 ' t u s i n g i n d u c t i v e l y c o u p l e d

8 2 F u el 9 9 5 V o l u m e 7 4 N u m b e r 2


2/11

able 1 Pro p e r t i e s o f b i o ma ss

I n f l uenc e o f m i ne ra l ma t t e r on b i omas s py ro l y s i s K R av eend ran et a l

P r o x i m a t e a n a ly s i s ( w t )

U l t i m a t e a n a l y si s ( w t d b )

H H V a D e n s i ty

V M ( d a f ) A s h ( d b ) C H N O ( M J k g - 1 ) ( k g m - ' )

Bag asse 84.2 2.9 43.8 5.8 0.4 47. l 16.29 111

Co con ut co i r 82 .8 0 .9 47 .6 5 .7 0 .2 45 .6 14 .67 151

Co con ut shel l 80 .2 0 .7 50 .2 5 .7 0 .0 43 .4 20 .50 661

Co ir p i th 73 .3 7 .1 44 .0 4 .7 0 .7 43 .4 18 .07 94

Co rn cob 85 .4 2 .8 47 .6 5 .0 0 .0 44 .6 15 .65 188

Co rn s ta lks 80 .1 6 .8 41 .9 5 .3 0 .0 46 .0 16 .54 129

Co t ton g in was te 88 .0 5 .4 42 .7 6 .0 0 .1 49 .5 17 .48 109

G ro un dn ut shel l 83 .0 5 .9 48 .3 5 .7 0 .8 39 .4 18 .65 299

M illet hu sk 80.7 18.1 42.7 6.0 0.1 33.0 17.48 201

Rice hu sk 81.6 23.5 38.9 5.1 0.6 32.0 15.29 617

Rice stra w 80.2 19.8 36.9 5,0 0.4 37.9 16.78 259

Su bab ul wo od 85 .6 0 .9 48 .2 5 .9 0 .0 45 .1 19 .78 259

W hea t s t raw 83 .9 11 .2 47 .5 5 .4 0 .1 35 .8 17 .99 222

H i g h e r h e a t i n g v a l u e

T a b l e 2 C o m p o n e n t a n a l y si s o f b i o m a s s ( w t d b )

T o t a l T o t a l

Ash Ho l o c e l l u lo se C e l l u lo se He m i c e l l u lo se L i g n i n Ex t ra c t i v e s (h o l o ) (h e mi )

Bag asse 2.9 65.0 41.3 22.6 18.3 13.7 99.9 98.8

Co con ut co i r 0 .8 67 .0 47 .7 25 .9 17 .8 6 .8 111 .7 99 .0

Co co nu t shell 0.7 67.0 36.3 25.1 28.7 8.3 98.7 100.1

Co ir pit h 7.1 40.6 28.6 15.3 31.2 15.8 94.8 98.1

Co rn cob 2.8 68.2 40.3 28.7 16.6 15.4 102.9 101.8

Co rn stalk s 6.8 63.5 42.7 23.6 17.5 9.8 97.6 100.5

Co tto n gin wa ste 5.4 90.2 77.8 16.0 0.0 1.1 86.7 100.2

G ro un dn ut shel l 5 .9 55 .6 35 .7 18 .7 30 .2 10 .3 102 .0 100 .7

Mi llet hu sk 18.1 50.6 33.3 26.9 14.0 10.8 96.5 104.1

Ric e hu sk 23.5 49.4 31.3 24.3 14.3 8.4 96.5 101.8

Rice str aw 19.8 52.3 37.0 22.7 13.6 13.1 98.8 106.2

Sub abu l wo od 0 .9 65 .9 39 .8 24 .0 24 .7 9 .7 101 .2 99 .0

W he at s t raw 11 .2 55 .8 30 .5 28 .9 16 .4 13 .4 96 .7 100 .4

T a b l e 3 A s h c o m p o s i t i o n o f b i o m a s s : m a j o r e l e m e n t s ( p p m w d r y b i o m a s s )

A 1 C a F e M g N a K P S i

Ba gas se - 1518 125 6261 93 2682 284 17 340

Co con ut co i r 148 477 187 532 1758 2438 47 2990

Co co nu t shell 73 1501 115 389 1243 1965 94 256

Co ir pit h 1653 3126 837 8095 10 564 26 283 1170 13 050

Co rn cob - 182 24 1693 141 9366 445 9857

Co rn s ta lks 1911 4686 518 5924 6463 32 2127 13 400

Co t ton g in waste 3737 746 4924 1298 7094 736 13 000

G ro un d nut shel l 3642 12 970 1092 3547 467 17 690 278 10 960

M illet hu sk - 6255 1020 11 140 1427 3860 1267 150 840

Rice husk - 1793 533 1612 132 9061 337 2206 90

Rice s t raw - 4772 205 6283 5106 5402 752 174 510

Su bab ul wo od - 6025 614 1170 92 614 100 195

W he at s t raw 2455 7666 132 4329 7861 28 930 214 4444 0

p l a s m a - a t o m i c e m i s s i o n s p e c t r o s c o p y a r e p r e s e n t e d in

Tables 3 a n d 4 .

Sample preparation

T o u n d e r s t a n d t h e i n f l u e n c e

o f m i n e r a l m a t t e r , t w o t y p e s o f s a m p l e w e r e s t u d i e d :

( 1) d e m i n e r a l i z e d b i o m a s s ; ( 2 ) s y n t h e t i c b i o m a s s . T o

c o n f i r m t h e re s u l t s , s t u d i e s w e r e a l s o c a r r i e d o u t o n

s a l t - i m p r e g n a t e d a n d a c i d - s o a k e d s a m p l e s o f s e l e c t e d

b i o m a s s t y p e s . T h e s a m p l e s w e r e p r e p a r e d a s f o l lo w s .

D e m i n e r a l i z a t i o n w a s c a r r i e d o u t i n t w o s t a g e s . I n t h e

f i rs t s t a g e , b i o m a s s s a m p l e s w i t h p a r t i c l e s iz e r a n g i n g

f r o m 1 00 t o 2 5 0 m m w e r e t r e a t e d w i t h 1 0 H C 1 a t 6 0 C

f o r 4 8 h w i t h c o n s t a n t s t i r r i n g . I n t h e s e c o n d s t a g e ,

b i o m a s s o f h i g h e r s i li c a c o n t e n t w a s f u r t h e r t r e a t e d w i t h

a q u e o u s 5 N a O H f o r 1 h a t 9 0 C . S a m p l e s w e r e t h e n

w a s h e d w i t h d i s t i l l e d w a t e r , f i l t e r ed , d r i e d a n d s t o r e d .

S y n t h e t i c b i o m a s s s a m p l e s w e r e p r e p a r e d b y m i x i n g

t h e i n d i v i d u a l b i o m a s s c o n s t i t u e n t s ( c e ll u lo s e , l ig n i n ,

x y l a n , e x t r a c t i v e s a n d a s h ) , in p r o p e r p r o p o r t i o n s .

E x t r a c t i v e s w e r e i s o l a te d f r o m e a c h b i o m a s s t y p e

a c c o r d i n g t o T A P P I s t a n d a r d T 1 1 m . T h e a s h w a s

o b t a i n e d b y b u r n i n g c o r r e s p o n d i n g b i o m a s s i n a m u f f l e

f u r n a c e , T h e p r o p o r t i o n s o f t h e i n d i v i d u a l c o n s t i t u e n t s

w e r e ta k e n f r o m t h e c o m p o n e n t a n a l y s e s . T o s i m u l a t e

F u el 1 9 9 5 V o l u m e 7 4 N u m b e r 12 1 8 1 3


3/11

I n f l u e n c e o f m i n e r a l m a t t e r o n b i o m a s s p y ro l y s is . K . R a v e e n d r a n

e t a l

T a b l e 4 A s h c o m p o s i t i o n o f b i o m a s s : t r a ce e l e m e n t s p p m w d r y b i o m a s s )

B i o m a s s

Co Cr Cu Mn Ni S Zn

B a g a s s e 1 8 9 1 6 6 0 1 6

C o c o n u t c o ir 0.6 2.0 68 4 2 64 25

C o c o n u t s h e l l

0.5 0.3 5 1 13 35 9

Coi r pith 3.2 0.2 1239 27 22 476 40

C o r n c o b T ~ 19 6 15 11

C o r n s t a l k s

8.0 11 32 12 13 564 32

C o t t o n g i n w a s t e T 38 1 0 58 22

G r o u n d n u t s h e l l

2.3 6 11 44 l I 299 52

M i l l e t h u s k T 38 49 317 94

R i c e h u s k 21 108 32 163 1244

R i c e s t r a w

T 463 45 221 47

S u b a b u l w o o d 1 2 1 66 40

W h e a t s t r a w 7 25 25 787 18

a P r e s e n t i n t r a c e a m o u n t

r

. .. .. . . . . m - - N [ l : , > q

, ,, - , ;,

T b

; . .

:.: Y,;.:

- : - , i

T T HER NO COUPLE

1 ROTAHETER

2 GAS HEATER

3 PYROLYSIS REACTOR

(ELECTRICAL FURNACEI

4 CERAMIC WOOL

INSUL TION

5 HEATING EkE MENT

6 CERAMIC TUBE

7 SAMPLE BOAT

8 CLEANING PORT

9 PRODUCT VAPOUR

10 TEMPERATURE CONTROLLER

11 TEMPERATURE INDICATOR

12 CONDENSER TUBE

13 CHILLED WAT ER TANK

1/, WATER CIRCULATION PUMP

15 CONDENSING TRAIN

16 GAS FLOW METER

F i g u r e 1 S c h e m a t i c o f t h e b i o m a s s p y r o l y s e r

d e m i n e r a l i z e d b i o m a s s , a s h w a s e x c lu d e d f r o m t h e

m i x t u r e .

P o t a s s i u m c h l o r i d e w a s i m p r e g n a t e d i n t o d e m i n e r -

a l i z e d c o i r p i t h , ri c e h u s k a n d g r o u n d n u t s h e l l a t d i ff e r e n t

c o n c e n t r a t i o n s . T h e s e b i o m a s s t y p e s w e r e c h o s e n o n t h e

b a s is o f t h e r e su l t s r e p o r t e d b e l o w . B i o m a s s s a m p l e s

1 t o o l , ~ 2 5 g ) w e r e s o a k e d f o r 4 8 h i n K C 1 s o l u t i o n s o f

s t r e n g t h 0 . 0 1 a n d 0 . 3 6 g m l - Z a t r o o m t e m p e r a t u r e . Z i n c

c h l o r i d e w a s s i m i l a r l y i m p r e g n a t e d i n t o t h e s a m e

b i o m a s s t y p e s , u s i n g 0 .0 1 a n d 1 .0 g m l - ~ s o l u t i o n s . T h e

a m o u n t s o f s a lt s i m p r e g n a t e d w e r e d e t e r m i n e d b y a s h

a n a l y s i s .

T h e r m a l a n a l y s i s

D y n a m i c t . g. a , s t u d i e s w e re c a r r ie d o u t w i t h a t h e r m a l

a n a l y s e r o n u n t r e a t e d , d e m i n e r a l i z e d a n d s y n t h e t i c

b i o m a s s s a m p l e s a t a h e a t i n g r a te o f 5 0 K m i n - 1 i n a

n i t r o g e n f lo w .

P y r o l y s i s

E x p e r i m e n t s w e r e c o n d u c t e d i n a p a c k e d b e d p y r o l y s er

d e s i g n e d f o r t h e p u r p o s e , w i t h p r o v i s i o n f o r c o l l e c ti n g

t h e p y r o l y s i s p r o d u c t s .

igure

s h o w s a s c h e m a t i c o f t h e

p y r o l y s i s r e a c t o r .

B a s e d o n t h e r e s u l t s o f t h e t h e r m a l a n a l y s i s , f i v e

r e p r e s e n t a t i v e b i o m a s s t y p e s w e r e s e l e c t e d f o r f u r t h e r

i n v e s t i g a t i o n s u s i n g t h i s r e a c t o r. I s o t h e r m a l e x p e r i m e n t s

i n a n i t r o g e n f l o w a t 7 7 3 K w e r e c o n d u c t e d o n 1 0 - 2 5 g

s a m p l e s o f e a c h o f th e s e fi v e b i o m a s s s a m p l e s , b o t h

u n t r e a t e d a n d d e m i n e r a l i z e d . T h e v o l a t i l e s e v o l v e d w e r e

c o l l e c te d a n d q u e n c h e d i n a t r a in o f f la s k s i m m e r s e d i n

a n ic e b a th . T h e r e m a i n i n g n o n - c o n d e n s a b l e g a s e s w e re

p a s s e d t h r o u g h a f l o w m e t e r . T h e e x p e r i m e n t w a s

c o n t i n u e d u n t i l t h e e v o l u t i o n o f g a s e s c e a se d . T h e

f u r n a c e w a s t h e n s w i t c h e d o f f a n d t h e r e m a i n i n g c h a r

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

t h e n w e i g h e d . T h e t a r y i e ld w a s o b t a i n e d f r o m t h e

1 8 1 4 F ue l 1 9 9 5 V o lu m e 7 4 N u m b e r 1 2


4/11

I n f l uenc e o f m i ne ra l ma t t e r on b i omas s py ro l y s is K R av eend ran e t a l

1 . 0 . . , , , , , , , 2 - 0

. . . . U n t r e a t e d

0 , 8 - C O R N

~ \ . V I O e a s h e d = 1 . 5

1 . 0 o ,

o 0.~

1 5 0 2 0 0 2 ; 0 3 0 0 3 ' 5 0 4 0 0 , 5 0 5 ' 0 0 5 ' 5 0 6 ' 0 0 6 5 0 7 0 0

T e m p e r a t u r e ( { ; )

igure

2 T . g . a . a n d d . t . g, c u r v e s o f u n t re a t e d a n d d e m i n e r a l i z e d c o r n

c o b

difference in the weight of the flasks before and after the

experiment. The yield was obtained by difference.

Repeatable results were achieved.

The char and liquid products were tested for proper-

ties including ultimate analysis, heating value, iodine

adsorption of char and BET surface area o f char.

RESULTS AND DISCUSSION

Tables 3 and 4 in conjunction with Table 1 show that the

straws and husks are characterized by ash of high silica

content (90-95 wt ). Wood ash is characterized by high

Ca (70wt ), Mg (14wt ) and K (7wt ) contents,

whereas coconut coir ash has high K (36 wt ) and Na

(13wt ) contents. The ash of bagasse, corn cob and

corn stalks has high K, Mg and Ca contents. It can also

be seen that rice husk, groundnut shell, coir pith and

wheat straw have high K contents, and rice husk in

particular contains ~100 times as much Zn as the other

biomass types.

Therm al ana lys is

Influence o f demineralization Representative t.g.a.

and d.t.g, curves for untreated and demineralized bio-

mass are presented in

Figure 2

The changes in volatile

and char yields on demineralization, as well as the

changes in maximum rate of pyrolysis and incipient

devolatilization temperature for all the biomass types

are shown in

Table 5

Table 5 clearly brings out the influence of mineral

matter. It can be seen that the removal of mineral matter

increases the yield of volatiles except for coir pith,

groundnut shell and rice husk. Demineralization

increases the maximum rate of devolatilization and the

initial decomposition temperature in all cases. The

exceptional behaviour of the above three biomass types

may be explained on the following grounds.

Rice husk, groundnut shell and coir pith can be seen to

Tab l e 5 I n f l u e n c e o f d e m i n e r a l i z a t i o n o n p y r o l y s i s : t . g .a , s t u d i e s

Y i e l d ( w t % ) b

M a x . d e v o l.

S t a t e a V o l a t i l e s C h a r r a t e ( w t % K - ] )

R e l a t iv e c h a n g e ( % ) T e m p e r a t u r e ( K )

V o l a ti l es C h a r M a x . r a t e I D T I P T T M R

B a g a s s e U 7 9 . 7 2 0 . 3 0 . 9 2

D 8 1 .4 1 8 .6 1 .2 7 2 .2

C o c o n u t c o i r U 6 9 . 8 3 0 . 2 0 . 8 0

D 70 .8 29 .2 1 .28 1 .3

C o c o n u t s h e l l U 7 0 . 7 2 9 . 3 0 . 7 5

D 72 .7 27 .3 1 .01 2 .80

C o i r p i t h U 5 6 . 8 4 3 . 2 0 . 5 6

D 5 2 . 2 4 7 . 8 0 . 5 0 - 8 . 2

C o r n c o b U 7 3 . 5 2 6 . 5 1 .0 8

D 88 .8 11 .2 1 .64 20 .8

C o rn s t a l k s U 7 0 .9 2 9 .1 1 .1 4

D 7 7 .0 2 8 .0 1 .9 5 8 .6

C o t t o n g i n w as t e U 8 0 .6 1 9 .4 1 .3 1

D 89 .4 10 .6 1 .86 10 .8

G r o u n d n u t s h e l l U 6 8 . 7 3 1 . 3 0 .6 7

D 6 6 . 7 3 3 . 3 0 . 7 5 - 2 . 9

M i l l e t h u s k U 7 0 .1 2 9 .9 0 .8 8

D 80 .6 19 .4 1 .48 15 .0

R i c e h u s k U 7 0 . 0 3 0 . 0 0 . 8 4

D 6 6 .2 3 3 .8 1 .0 7 -5 .1

R i ce s t r aw U 7 4 .7 2 5 .3 1 .0 3

D 82 .1 17 .9 1 .31 9 .9

D D a 8 1 .6 1 8 .4 1 .2 7 9 .3

S u b a b u l w o o d U 7 5 . 4 2 4 . 6 0 . 9 7

D 77 .3 22 .7 1 .27 2 .4

W h e a t s t r a w U 7 2 . 8 2 7 . 2 0 . 9 0

D 75 .1 24 .9 1 .21 3 .2

4 8 3 6 8 8 6 7 7

- 8 . 5 3 9 . 4 5 2 8 7 0 8 6 7 3

5 1 3 6 7 3 6 7 2

- 3 . 0 5 8 . 9 5 4 8 7 1 3 6 7 8

5 1 8 6 7 8 6 1 5

- 6 . 6 3 5 . 2 5 3 3 7 1 8 6 2 0

4 8 3 6 6 3 6 2 2

1 0 .8 -1 1 . 0 5 1 3 9 4 8 6 3 3

5 3 3 6 5 3 6 0 3

- 5 7 . 7 5 1 . 5 5 5 8 6 9 8 6 6 0

4 9 8 6 5 3 6 3 4

- 0 . 2 5 8 . 9 5 3 3 6 8 3 6 3 9

5 2 3 6 8 8 6 7 9

-4 5 .1 3 6 .1 5 5 3 6 9 3 6 8 4

4 9 3 6 8 3 6 6 2

6.3 12 .1 513 673 668

5 2 3 6 6 3 6 5 3

- 1 6 . 2 6 8 . 4 5 0 3 6 8 3 6 5 8

5 1 8 6 6 3 6 6 6

1 2 .6 2 6 .9 5 4 3 6 9 3 6 6 8

518 673 651

- 2 9 . 3 2 7 . 0 5 4 8 7 0 3 6 5 3

- 2 7 . 4 2 3 . 3 5 2 3 6 9 3 6 5 5

4 9 8 6 0 3 6 7 2

- 7 . 3 3 0 . 8 5 2 8 7 2 8 6 8 8

4 9 3 6 6 3 6 0 4

- 8 . 5 3 4 . 3 5 1 8 6 6 8 6 1 7

a U , u n t r e a t e d ; D , d e m i n e r a l i z e d

b D a f b i o m a s s b a s i s

( I D T , i n it ia l d e c o m p o s i t i o n ; I P T , i n v o l u t i o n p o i n t ; T M R , m a x . r a t e

a A l k a l i - t r e a t e d a f t e r a c i d t r e a t m e n t

F u el 1 9 9 5 V o l u m e 7 4 N u m b e r 1 2 1 8 1 5


5/11

I n f l u e n ce o f m in e r a l ma t te r o n b i o ma ss p y r o l ys i s K. Ra ve e n d r a n et al

F i g u r e

3

1 5 . 0

1 0 . 0 ~

~ -

m

o 5 . 0

o

c

c

~ 0 . 0 .

u

5.0.

I 0 . 0

-1.1

I I I

B G - B A G A S S E

CN-CASHEW NUT S H E L L

A C B C R - C O C O N U T C O I R

C S - C O C O N U T

S H E L L

M H C P - C O I R P I T H

A C B - C O R N C O B _

C W C S - C O R N S T A L K S

A CW -COTTONGI N

W A S T E

R S

GS-GROUNDNUT

S H E L L

A ~ . ~ ~ M H - M I L L E T H U S K

R H - R I C E H U S K

C T R S - R I C E S T R A W - -

W D - W O 0 0

W S - W H E A T S T R A W

.A

W S

A A C S ~

S E = 2 2 9

Y - - 0 . 9 6 4 x X . , 7 .1 9 2

R H ' , , . A

I

I c g

I

I

I

I

I i I I I I I I I [ I I I I i i l I l i i i I I I i I I I I i

&.0 7.5 9.0 14.0

L ign in l 095 2X K 1 3727 Xz0 0996

C h a n g e i n v o l a ti l es v e r s u s p r o d u c t o f l i g ni n p o t a s s i u m a n d z i n c c o n t e n t s

I

1 5 . 0

u

O

u.

O

t-

O1

F i g u r e 4

1 .00 ~ 1

0 . 7 5

0 . 5 0 /

~ll

0 .25

0.00 :a.~.

150 250 350

I ~ i

1.00

O R I G I N A L ]

- - ~ ~ S Y N T H E T IC 0 .7 5

I

450

0 . 5 0

025

0.~

7

Temperature( C

O

e

O

>

O

T . g . a . c u r v e s o f n a t u r a l a n d s y n t h e ti c b i o m a s s p y r o l y s is

1.00 I ~ ~ I I i I 1.00

~ O E S H E D

7 5 . 0 - - ~ J ~ll~ - - ~ - ~ - - S Y N T H E T I C - 0 . 7 5

;.= o ~ W r T . 0 U T A s . i

0.50

0.0-

.~ 25.0 - o,25

0.00 I-n.-. ~ - - ,--'a--D--n- .~~ t~ I

I I I I I v . v v

1 5 0

250 350 450 550 650 7 0 0

T e m p e r a t u r e ( C )

h a v e h i g h l i g n i n c o n t e n t s

Table 2) .

I t i s k n o w n f r o m

t h e l i t e r a t u r e T a n d t h e a u t h o r s s t ud i e s t h a t o n

p y r o l y s i s , li g n i n g i v e s a h i g h e r c h a r y i e l d t h a n c e l lu l o s e

o r h e m i c e l l u l o s e . F u r t h e r , p o t a s s i u m , w h i c h i s e x c e p -

t i o n a l l y h i g h i n th e s e t h r e e k i n d s o f b i o m a s s , i s k n o w n t o

be a s t ro ng ca ta lys t fo r cha r gas i f i ca t ion 12 15, p ro m ot i ng

t h e g a s i f ic a t io n o f c h a r b y C O 2 a n d H 2 0 . I t c a n b e

u n d e r s t o o d t h a t s in c e C O 2 a n d H 2 0 a r e p r i m a r y

p r o d u c t s o f p y r o l y s is , i n t h e p r e se n c e o f p o t a s s i u m t h e y

reac t w i th the cha r (p resen t in h igh y ie ld in i t i a l ly in these

c a s e s b e c a u s e o f t h e h i g h l i g n i n c o n t e n t ) t o f o r m C O a n d

H 2 , t h e r e b y d e c r e a s i n g t h e c h a r y i e l d . I n o t h e r b i o m a s s

types , no t on ly i s t he re l e s s po t as s iu m bu t a l so l es s l i gn in .

I n w h e a t s t r a w , e v e n t h o u g h t h e p o t a s s i u m c o n t e n t i s

h i g h , b e c a u s e o f t h e l o w e r l i g n i n c o n t e n t t h e c h a r y i e l d

d o e s n o t i n c r e a s e o n d e m i n e r a l i z a t i o n .

1 8 1 6 F u e l 1 9 9 5 V o l um e 7 4 N u m b e r 1 2


6/11

In f lue nce o f min era l mat te r on b ioma ss py ro lys is . K . Rave endran

et al

Table 6 Influence of salt impregnation on pyrolysis: t.g.a, studies

Yield (wt f

Relative change ( )b

Max. devol.

Volatiles Char rate (wt K- l ) Vola ti les Char Max. rate

Temperature (K)c

IDT IPT TMR

Coir pith

KCI (H)a 86.5 13.5 0.80 65.7 -71.7 59.9

(L)~ 62.6 37.4 0.99 19.9 -21.8 98.5

ZnCI2 (H) 99.0 1.0 0.69 89.7 -97.9 38.0

(L) 63.4 36.6 0.43 21.5 -23.4 13.1

Untreated 56.8 43.2 0.56 8.9 -9.7 12.4

Demineralized 52.2 47.8 0.50 -

Groundnut shell

KC1 (H) 79.3 20.7 1.04 18.9 -37.9 38.4

(L) 74.6 25.4 1.12 11.8 -23.6 48.8

ZnC12 (H) 98.6 1.4 0.68 47.8 -95.6 -8 .8

(L) 70.8 29.2 0.57 6.1 -12.2 -23.5

Untreated 68.7 31.3 0.67 3.0 -6.0 -10.8

Demineralized 66.7 33.3 0.75

Rice husk

KC1 (H) 80.7 19.3 1.06 21.9 -42.9 - 1.4

(L) 76.6 23.4 1.15 15.6 -30.7 7.5

ZnCI2 (H) 97.9 2.1 0.66 47.8 -93.8 -38.3

(L) 77.7 22.3 0.45 17.4 -34.1 -58.2

Untreated 70.0 30.0 0.84 5.7 -11.2 -21.2

Demineralized 66.2 33.8 1.07 - -

483 683 370

463 693 365

698 953 883

503 778 693

483 663 622

513 948 633

493 683 653

493 683 643

693 943 883

493 773 583

493 683 662

513 673 668

533 603 658

533 603 653

723 953 883

603 883 773

518 703 666

543 673 668

a H, high, L, low, concentration of solution (0.36 and 0.01 gml J for KC1, 1.0 and 0.1 gml -j for ZnCI2)

b Compared with the demineralized biomass

a b l e

7 Influence of ash on pyrolysis in reactor

Yield (wt daf) Relative change ( )

State Vol. Char Liquid Gas Vol. Char Liquid Gas

Coir pith U 70.5 29.5 29.4 41.0

D 68.7 31.3 36.2 32.5 -2 .4

Corn cob U 79.9 20.1 37.4 42.5

D 87.1 12.9 43.4 43.6 8.9

Groundnut shell U 72.9 27.1 40.5 32.5

D 72.5 27.5 45.9 26.6 -0 .5

Rice husk U 82.7 17.3 41.2 41.5

D 75.6 24.4 57.4 18.2 -8 .6

Wood U 80.7 19.3 22.6 58.0

D 86.4 13.6 40.1 46.4 7.1

5.5 23.1 -20.8

-35.6 16.0 -3.2

1.5 13.4 -9.1

41.3 39.3 -56.2

-29.8 76.9 -20.1

In a similar manner, the presence of zinc (known to be

a good activating agent) in rice husk as well as the high

lignin content explain the increase in char yield on

demineral izat ion. The co mbined influence of potassium,

zinc and high l ignin conten t is represented in Figure 3.

The fol lowing corre lation was developed for this

behaviour:

A V = -0. 964 (L

l ' 0 9 5 v . - x l ' 3 7 2 7 V 0 . 0 9 9 6 ~ . / x

) + 7.192

where A V = change in p ercentage yield of volatiles due

to demineral izat ion, L = l ignin content (wt ) of bio-

mass, X~: = fraction of pota ssi um in silica-free ash, an d

Xz -- fraction of zinc in silica-free ash. This correlation

was obtaine d by non -l inear optimizat ion for these

biomass types with a standard error of 2.29. To validate

this correlation, a further biomass type, namely cashew

nut shell, was studied. The change in percentage yield of

volati les obtain ed experimental ly was -7 .37 and the

model predict ion was -7. 22. This correlat ion can there-

fore be used to predict the in fluence of mineral matte r

satisfactorily.

As can be seen in

Figure 3

zero on the y-axis,

representing no change in volat i le matter, corr esponds to

a value of 7.5 on the x-axis. When the value of the

product in brackets in the above correlation exceeds 7.5,

therefore, the chan ge in yield of volatiles is negative.

Synth et ic bioma ss s tudies . Figure 4 compares the t.g.a.

and d.t.g, curves of synthetic and u ntrea ted representative

biomass (coir pith). The pyrolysis characteristics of the

synthetic biomass match those of the natural one well.

This is true for all the biomas s types tested. These results

confirm the definite role played by mineral matter,

irrespective of its structure and other properties, in the

pyrolysis of the biomass.

In f luence o f sa l t impregnat ion .

The specific pyrolysis

behaviour of groundnut shel l , rice husk and coir pi th

F ue l 1 9 9 5 V o l u m e 7 4 N u m b e r 1 2 1 8 1 7


7/11

In f lue nce o f mine ra l ma t te r on b iomass py ro lys is . K . Ravee ndran e t a l

Table 8 Inf luence of chlor ide sa l t imp regnatio n on pyrolysis in reac tor

Sa l t Y ie ld (w t% da f )

im pre gna te d

(wt%) Vola t i le s Cha r L iquid Ga s

Re la t ive cha nge (% )

Vola t i le s Cha r L iquid Ga s

Coir pith

KC1 (H)a 52.9 80.5 19.5 24.2 56.2

(L) a 9.7 75.6 24.4 28.4 47.2

ZnC12 (H) 18.8 90.1 9.9 25.9 64.2

(L) 2.8 83.6 16.4 29.4 54.2

Un trea ted - 70.5 29.5 29.4 41.0

Dem inera l ized - 68.7 31.3 36.2 32.5

Groundnut shell

KC I (H) 54.0 76.7 23.3 34.3 42.5

(L) 3.3 73.8 26.2 39.3 34.5

ZnC12 (H) 13.9 90.8 9.2 18.9 71.9

(L) 2.6 76.4 23.6 26.8 50.4

Un trea ted - 72.9 27.1 40.5 32.4

Dem inera l ized - 72.5 27.5 45.9 26.6

Rice husk

KC I (H) 27.6 77.4 22.6 35.1 42.3

(L) 1.7 77.0 23.0 42.2 34.8

ZnC12 (H) 9.8 87.1 12.9 38.4 48.8

(L) 1.5 78.1 21.9 30.0 48.1

Un trea ted - 82.7 17.3 41.2 41.5

Dem inera l ized - 75.6 24.4 57.4 18.2

17.1 -3 7.6 -33 .1 73.1

10.0 -22 .0 -21 .7 45 .4

31.1 -28 .5 -28 .5 97 .6

21.7 -19 .0 -19 .0 67 .0

- 2 . 5 - 5 . 5 - 1 8 . 8 2 6 .2

5 .8 -15 .3 -25 .4 59 .5

1 .8 -4 .7 -14 .4 29 .6

25.1 -66 .3 -58 .9 170.0

5 .3 -14 .1 -41 .6 89 .3

0 .5 -1 .5 -11 .8 21 .7

2 .4 -7 .5 -38 .8 132.2

1 .9 -5 .9 -26 .4 91 .2

15.3 -47 .3 -33 .1 167.9

3 .4 -10 .5 -47 .7 164.3

9 .5 -29 .2 -28 .2 128.2

a Com pa re d wi th de m ine ra l i z e d b iom a ss

Ta ble 9 Inf lue nce of c a rbona te s a l t im pre gna t ion on pyro lys is in r e a c tor

Sa l t Y ie ld (w t% da f )

im pre gna te d

(wt%) Vola t i le s Cha r L iquid

G a s

Rela t ive change (%)a

Vola t i le s Cha r L iquid Ga s

Groundnut shell

K z C O 3 (H) 49.4 68.3 31.7 6.1 62.2

(L) 6.8 73.7 26.3 10.0 63.7

Zn CO 3 (H) 39.5 83.9 16.1 5.9 78.0

(L) 11.8 75.3 24.7 16.7 58.6

Un trea ted 72.9 27.1 40.5 32.4

Dem inera l ized 72.5 27.5 45.9 26.6

Rice husk

KzC O 3 (H) 33.3 71.7 28.3 5.5 66.2

(L) 11.1 86.7 13.3 11.9 74.8

ZnCO 3 (H) 22.8 78.4 21.6 5.5 72.9

(L) 6.5 78.0 22.0 13.9 60.0

Un trea ted - 82.7 17.3 41.2 41.5

Dem inera l ized 75.6 24.4 57.4 18.2

-5 .9 15 .6 -86 .8 133.6

1.6 -4 .3 -78 .1 139.2

15.1 -4 1.4 -87 .2 193.0

3.8 -1 0.0 -6 3.6 120.1

0 .5 -1 .5 -11 .8 21 .7

-5 .1 15 .6 -90 .4 263.9

14.7 -45 .5 -79 .4 311.0

3 .8 -11 .8 -90 .4 300.8

2 .1 -6 .4 -75 .7 230.0

9 .5 -29 .2 -28 .2 128.2

a Com pa re d wi th de m ine ra l iz e d b iom a ss

w a s f u r t h e r i n v e s t i g a t e d b y s t u d i e s c o n d u c t e d w i t h s a l t -

i m p r e g n a t e d b i o m a s s . B e c a u s e o f th e r e la t i v e l y h ig h K

c o n t e n t s o f g r o u n d n u t s h el l, co i r p i t h a n d r ic e h u s k

T a b l e 3 )

a n d t h e h i g h Z n c o n t e n t o f ri c e h u s k

T a b l e

4 ) , p o t a s s i u m a n d z i n c s a lt s w e r e u s e d f o r i m p r e g n a t i o n .

T h e r e s u lt s a re c o m p a r e d w i t h t h o s e f o r t h e u n t r e a t e d

a n d d e m i n e r a l i z e d o r i g i n a l b i o m a s s i n T a b l e 6 .

T a b l e 6

s h o w s t h a t , o n i m p r e g n a t i o n w i t h e it h e r K C 1

o r Z n C 12 , a t b o t h l o w a n d h i g h c o n c e n t r a t i o n s , t h e y ie l d

o f v o l a t i l e s i n c r e a s e s f o r a l l t h r e e b i o m a s s t y p e s t h e r e b y

r e d u c i n g t h e c h a r y i e l d . I t i s e v i d e n t f r o m t h e s e r e s u l t s

t h a t t h e p o t a s s i u m a n d z i n c p r e s en t i n t h e u n t r e a t e d

b i o m a s s i n f l u e n c e t h e f o r m a t i o n o f v o l a t i l e s , s o t h a t o n

d e m i n e r a l i z a t i o n , g r o u n d n u t s h el l, c o i r p i t h a n d r i ce

h u s k y i e l d l e ss v o l a t i l e s . T h e i n i t i al d e c o m p o s i t i o n

t e m p e r a t u r e d e c r e a s e s o n K C 1 i m p r e g n a t i o n . I n c o n t r a s t ,

Ta ble 10 Crys ta l l in i ty inde x of b iom a ss

Crysta l l ini ty index

C h a n g e

Biom a ss Unt re a te d De m ine ra l i z e d in Cr l (%)

Co ir pi th 8.7 12.5 43.2

Corn c ob 34 .6 32 .3 -6 .6

Gro und nut shell 25.0 50.1 100.0

Rice husk 43.6 53.3 22.2

W ood 44 .0 41 .8 -5 .1

Z n C 12 i m p r e g n a t i o n n o t o n l y in c r e a se s th e d e c o m p o s i -

t i o n t e m p e r a t u r e b u t i n c r e a s e s i t m o r e , t h e h i g h e r t h e s a lt

c o n c e n t r a t i o n . I t i s c l e a r f r o m t h i s t h a t t h e s h i f t in

d e c o m p o s i t i o n t e m p e r a t u r e o b s e r v e d o n d e m i n e r a l i z a -

8 8 Fue 995 Volume 74 Num ber 2


8/11

I n f l uenc e o f m i ne ra l ma t t e r on b i omas s py ro l y s i s K R av eend ran et al

a b l e

11 Char adsorption properties

State InZdex

Change

12 in 12 12 12 BET Change

adsorbed adsorbed index adsorbed area in BET

(wt%) (%) (daf) (daf) (m2 g J) area (%)

Coir pith

Corn cob

Groundnut shell

Rice husk

Wood

Standard c

U 1.56 29.9

D 2.07 39.8

U 1.20 23.0

D 2.89 55.5

U 0.89 19.6

D 2.01 43.0

U 2.09 44.6

D 1.62 34.6

DD a 3.20 61.3

U 0.72 15.5

D 0.75 16.1

- 4.18 98.0

1.77 33.9 470

32.9 2.26 45.2 625 32.6

1.49 28.5 381

141.4 3.51 67.3 500 31.2

1.11 24.4 277

119.0 2.18 46.6 375 35.4

6.42 137.1 260

22.4 6.59 140.8 340 30.8

0.75 16.2 234

3.9 0.76 16.2 252 7.7

Alkali-treated after acid treatment

b i2 adsorbed (g) from standard 12 solution (2.7gml I) by 0.5g of carbon

c AR-grade activated carbon

Table 12 Higher heating value (MJkg

i

daf) of biomass pyrolysis

products

Sta te B io ma ss Char Liquids Gas~

Coir pith U 19.46 24.97 18.66 16.06

D - 26.19 22.33 10.51

Corn cob U 16.11 28.59 23.81 05.19

D - 26.35 24.19 08.01

Groundnut shell U 19.82 27.43 23.62 10.00

D - 29.76 26.15 02.97

Rice husk U 19.98 44.24 22.45 07.42

D - 30.96 23.72 07.13

Wood U 19.95 24.13 24.94 16.61

D 24.24 28.54 11.28

a By difference

tion can be at tributed to the presence of inorganic

material.

yrolysis

To ve r i fy the above resu l t s the th ree excep t iona l

materials (coir pi th, rice husk and gro und nut shell) and

two other typical representat ive materials (wood and

corncob) were used for further studies with the packed

bed pyrolyser, in the untreated, demineral ized and sal t-

impregnated forms.

b~uence of demineralization.

The results obtained,

Table 7 show a similar trend to that in the t.g.a, experi-

ments. The main findings are:

(1) as observed in thermal analysis, the char yield

increases on d emineral izat ion of the coir pi th, g rou ndn ut

shell and rice husk;

(2) again, the char yield decreases on demi ner aliza tion of

the other two representative materials;

(3) the increase in char yield on demin erali zatio n is much

greater for rice husk than for coir pi th and groundnut

shell;

(4) there is a su bst ant ial increase in liq uid yield for all five

materials, ranging from 77% for wood to 13% for

gr ou nd nu t shell; cons equen tly there is a decrease in gas

yield.

These results are of maj or significance for increased

liquids production and optimizing the production of

both liquids and char.

Influence of salt impregnation.

The results,

Table 8

again show a similar trend to that obtained in the t.g.a.

experiments. It can be observed that

(1) salt imp regnat ion of demineral ized biomass reduces

the char yield for all three samples studied (coir pith,

gro und nut shel l and rice husk);

Table 13 Distribution of energy in biomass pyrolysis products

Energy (%)

Change in energy (%)

State Char Liquids Gas Char Liquids Gas

Coir pith U 37.9 28.2 33.8

D 42.1 39.3 18.6 I 1.0 39.2 -45.0

Corn cob U 35.6 49.4 15.0

D 21.2 53.2 25.7 -40.6 7.6 71.8

Groundnut shell U 37.4 44.7 17.9

D 41.2 54.0 04.8 10.1 20.9 -73.6

Rice husk U 38.3 46.3 15.4

37.9 50.3 11.8 - 1.2 8.7 -23.4

Wood U 23.4 28.3 48.3

D 16.5 57.3 26.2 -29.5 102.5 -45.8



9/11

In f luen ce o f min era l mat te r on b ioma ss py ro lys is . K . Ravee ndran e t a l

T a b l e 14 Elemental analysis of pyrolysis prod ucts

Composit ion (wt daf) Ratio

State C H O H/C O/C C

Change ( )

H O H / C O / C

h a r

Co ir pith U 83.6 2.4 14.1 0.028

D 76.7 2.1 20.9 0.028

Co rn cob U 85.3 2.4 11.8 0.028

D 79.5 2.3 17.0 0.029

G.n ut shell U 78.9 2.4 17.7 0.030

D 80.0 2.2 16.8 0.027

Rice husk U 88.8 3.2 08.2 0.036

D 59.5 2.4 38.0 0.041

W oo d U 83.7 2.4 13.8 0.029

D 84.7 1.8 13.0 0.022

Liquid

Co ir Pith U 47.0 6.0 46.9 0.13

D 50.2 6.4 43.5 0.13

Co rn cob U 54.6 6.3 39.1 0.12

D 53.5 6.5 39.5 0.12

G.n ut shell U 55.4 7.3 34.6 0.13

D 34.2 7.8 57.1 0.23

Rice husk U 41.2 7.4 51.2 0.18

D 48.9 6.1 44.2 0.12

W oo d U 16.7 7.4 75.8 0.44

D 53.2 6.3 40.5 0.12

Gas


10/11

I n f l uenc e o f m i ne ra l ma t t e r on b i omas s py ro ly s i s : K R av eend ran et a l

iodine adsorpt ion by the char increases in most instances,

the greatest increases being obtained with corn cob and

groundnut shell.

The BET measurements show an increase in surface

area on demineralizat ion. It is interesting to note that the

increase in surface area is similar (~30 ) in almost all

instances. Demineralized coir pith char has the highest

surface area, followed by demineralized corn cob and

groundnut shell. Wood shows very low iodine adsorp-

tion and BET surface area.

It is well established that pores are developed during

pyrolysis23-26, depending on the amount of volatiles

released and the rate of their evolution for a given

biomass. On the other hand, it is also known that the

volatiles released undergo condensation reactions, form-

ing deposits on the pores or pore mouths developed.

As observed earlier

Table 5),

the amount of volatiles

released and their rate of evolution increase on deminer-

alization. An increase in rate reduces the residence time

of the volatile matter in the pores, consequently reducing

condensation in the pores. This explains the increases in

both char adsorptivity and liquids yield. These results are

of importance for obtaining a high char yield and a high

active surface area for activated carbon manufacture.

He a t i n g v a l u e .

The heating values of the chars and

liquids were measured and that of the gases was obtained

by difference. Table 12 presents the results. As can be

seen, the higher heating value of biomass on the dry

ash-free basis is similar for coir pith, groundnut shell,

rice husk and wood. However, the heating values of

the products are different for different types of biomass.

The heating value of the char increases marginally on

demineralizat ion, except for corn cob. The heat ing value

of the liquids increases in all cases through demineraliza-

tion, consequently reducing the heating value of the

gases in almost all cases. The distribution of energy in

the products is shown in

Table 13.

More of the energy

is transferred to the liquid fraction, except for coir pith,

which has more energy in the char. These results indicate

that coir pith could be a potential raw material for char

(or activated carbon) manufacture. For liquefaction,

corn cob, groundnut shell and rice husk may be preferred

to wood, but wood is a good feedstock for gasification.

These data are also of importance in selection of a

product for supplying heat for the pyrolysis process itself.

Elem en ta l com pos i tion .

Elemental analyses were car-

ried out on the chars and liquids from the untreated and

demineralized biomass. The elemental composition of

the gases was calculated based on the gas yield. The

results are presented in Table 14.

The increase in the hydrogen content in gases for

demineralized rice husk is almost 50 and the highest.

The basic composition of the liquids is very similar to

that of the original biomass. This is true for both

untreated and demineralized material, in accordance

with reports in the literature 27'z8. For groundnut shell

and rice husk the O/H ratio increases on demineraliza-

tion, whereas it decreases for wood and coir pith.

CONCLUSIONS

Sodium, potassium, calcium, magnesium, iron, phos-

phorus, aluminium and silicon are the major elements

present in biomass fuels; cobalt, chromium, copper,

manganese, nickel, sulfur and zinc are present in smaller

amounts.

The yield of volatiles, the devolatil ization rate and the

initial decomposition temperature increase on deminer-

alization for most of the kinds of biomass tested; rice

husk, groundnut shell and coir pith are exceptions. The

difference in behaviour of these three materials is

attributed to their high potassium (and/or zinc) content

in combination with a high lignin content. A correlation

has been developed to express this effect. In other words,

the mineral matter of biomass, in combination with the

organic composition, plays a major role in determining

pyrolysis product distribution and product properties.

ACKNOWLEDGEMENTS

The authors wish to thank Professor Wolfgang Klose,

FG Thermodynamik, Kassel University, Germany, for

useful discussions and valuable suggestions. They also

thank Mr N. Ganasekaran and Mr A. Sundaresan,

research scholars in the Chemistry Department, for their

help in obtaining the XRD patterns and Miss Bakul Rao,

operator, RISC, liT Bombay, for help in ICP-AES

analysis.

REFERENCES

1 A n t a l , M . J . J r . In A d v a n c e s i n So l a r En e rg y , V o l . 2 (Ed s

K . W. B o e r a n d J . A . D u f f l e ) , A me r i c a n So l a r En e rg y So c i e t y ,

N e w Y o rk , 1 9 83

2 O sm a n , E . A . A S t u d y o f t h e E f fe c ts o f A sh C h e m i c a l C o m p o -

s i ti o n a n d A d d i t i v e s o n F u s i o n T e m p e r a t u r e i n R e l a t i o n t o S l a g

F o r m a t i o n D u r i n g G a s i f i c at i o n o f B i o m a s s , P h . D T h e s is ,

U n i v e rs i t y o f C a l i fo rn i a , 1 9 8 2

3 G a n e sh , A . S t u d i e s o n C h a r a c t e r i sa t i o n o f B i o ma ss fo r G a s i f i -

c a t i o n , Ph . D Th e s i s , In d i a n In s t i t u t e o f Te c h n o l o g y , N e w

Delh i , 1990

4 Shafizadez , F. A d v C a r b o h y d r a t e C h e m 1968, 23, 419

5 Fe l d m a n n , H . F ., C h o l , P . S . , C o n k l e , H . N . a n d C h a rh a n , S . P .

In B i o m a ss a s a N o n Fo ss i l Fu e l So u rc e (Ed . D . L . K l a s s ) ,

Sy m p o s i u m Se r i es N o . 1 4 4 , A m e r i c a n C h e mi c a l So c i e ty ,

W a sh i n g t o n , D C , 1 9 81

6 G r a y , M . R ., C o r c o r a n , W . H . a n d G a v a l a s , G . R .

In d E n g

C h e m P r o c e s s D e s D e v 1985, 24 , 646

7 M a d o rsk y , S . L . , H a r t , V . E . a n d S t ra w s ,

S J R e s N a t B u r

S t a n d

1956, 343

8 Ess ig , M . , R i c h a rd s , G . N . a n d Sc h e n c k , E . In C e l l u l o se a n d

W o o d - - C h e m i s t r y a n d T e c h n o l o g y ( E d . S c h u e r c h) , W i l ey ,

N e w Y o rk , 1 9 8 9 , p p . 8 4 1 -8 6 2

9 Sh a p i n o , S . a n d B ra n n o c k , W. W. R a p i d A n a l y s i s o f S i li ca te ,

C a r b o n a t e a n d P h o s p h a t e R o c k s , U S G e o l o g i ca l S u r v e y,

B u l l e t i n 1 14 4 -A , Wa sh i n g t o n , D C , 1 9 62

1 0 B o a r , P . L . a n d In g ra m , L . K .

A n a l y s t

1970, 95, 124

11 S h a f iz a d ez , F . I n F u n d a m e n t a l s o f T h e r m o c h e m i c a l C o n v e r -

s i o n o f B i o ma ss (Ed s R . P . O v e re n d , T . A . M i l n e a n d L . K .

M u d g e ) , E l se v i e r A p p l i e d Sc i e nc e , N e w Y o rk , 1 9 85

1 2 Ta k a ra d a , T . , Ta m a i , T . a n d To m i t a ,

A F u e l

1986, 65, 679

1 3 M i u r a , K . , A i mi , M . , N a i t o , T . a n d H a sh i mo t o , K . F u e l 1986,

65 , 407

1 4 H a w l e y , M . L . , B o y d , M . , A n d e rso n , C . a n d D e v e ra , A .

F u e l

1983, 62, 213

1 5 Lo n g , R . J . a n d N e a v e l , R . C .

F u e l

1982, 61 , 620

1 6 H a w l e y , G . G . (R e v . ) . Th e C o n d e n se d C h e m i c a l D i c t i o n a ry ,

1 0 t h Ed . , V a n N o s t ra n d R e i n h o l d , N e w Y o rk , 1 9 81 , p . 1 1 0 8

1 7 L i d e, D . R . ( E d .) C R C H a n d b o o k o f C h e m i s t r y a n d P h y s i c s ,

7 3 rd Ed . , C R C Pre ss , 1 9 9 3

18 Segal, L., Creely , J . J . , M art in , A. E. , Jr an d Co nra d , C. M.

T e x

R e s J 1959, 786

19 Loeb , L. and Segal, L.

T e x R e s J

1955, 516

2 0 W e i n s t e i n , M . a n d B ro i d o , A .

C o m b u s t S c i T ech n o l

1970, 1,

287



11/11

In f luen ce o f min era l mat te r on b iomass pyro lys is . K . Ravee ndran et al

21 Broid o, A. and Weinstein, M.

Combust Sc i Technol

1970, 1,

279

22 Hassler , J . W. A ctive Car bo n , Chem ical Publishing Co. , 1954

23 Ya ni , H . , Ta ka ha shi , H . a nd I sh iya m a ,

K J C h e m En g J a p a n

1973, 6, 443

24 Cha ne y, N . K . Trans Electrochem Soc 1932, 28

25 Al lm a nd, A . J . a nd Cha pl in , R . Trans F araday Soc 1932, 28

26 Mu kherjee , S. and Bhattacharya , S. AC S, 1949, 71, 1725

27 Pa kde l , H . a nd Roy, C . In Pyrolys i s O i l s f rom Biom ass, Produ-

c ing , Ana lys ing a nd Upg ra ding (Eds J . Solt e s a nd T . A . M i lne ),

Sym pos ium Se ries N o. 37 6 , Am e r ic a n Che m ic a l Soc ie ty ,

Wa shington , DC, 1988

28 Piskorz , J . , Scott , D. S. and Radle in, D. In Pyrolysis Oils f rom

Biom ass, P roduc ing , Ana lys ing a nd Upg ra ding (Eds J . Sol te s

a nd T . A . Mi lne ) , Sym pos ium Se r ie s No. 376 , Am e r ic a n Che m i-

cal Socie ty, Washington, DC, 1988

8 2 2 F u e l 1 9 9 5 Vo l u m e 7 4 Nu m b e r 1 2

biomass fuel chemical analysis

Documents