Major, Minor, and Trace Element Composition of Coal and Fly Ash, as

10 Major, Minor, and Trace Element Composition of Coal and Fly Ash, as

Downloaded by UNIV OF AUCKLAND on December 17, 2015 | http://pubs.acs.org Publication Date: September 1, 1975 | doi: 10.1021/ba-1975-0141.ch010

Determined by Instrumental Neutron Activation Analysis Κ. H. ABEL and L. A. RANCITELLI Battelle, Pacific Northwest Laboratories, Richland, Wash. 99352 A highly sensitive instrumental neutron activation analysis (INAA) technique can determine 30-40 eléments in coal and fly ash including Sb, As, Se, Hg, Zn, and V which are elements of environmental concern. This multi-element capability makes possible the detailed chemical analysis of coal and combustion products. A comparison to National Bureau of Standards-Environmental Protection Agency fuel standards shows that a high degree of accuracy and precision is attainable, allowing tentative conclusions to be drawn as to the origin of certain elements in the coal and their fate during combustion.

' n p h e c u r r e n t emphasis o n t h e large-scale e x p l o i t a t i o n of c o a l as a c o m m e r c i a l e l e c t r i c a l e n e r g y source makes a m o r e t h o r o u g h u n d e r s t a n d i n g of t h e c h e m i s t r y of c o a l a n d t h e b y - p r o d u c t s of c o a l c o m b u s t i o n i n c r e a s i n g l y i m p o r t a n t . A n e x a m p l e of p l a n n e d large-scale c o a l use f o r p o w e r g e n e r a t i o n is t h e p r o p o s e d

N o r t h C e n t r a l P o w e r Project.

This

project

w i l l use t h e vast c o a l reserves i n t h e F o r t U n i o n F o r m a t i o n i n N o r t h Dakota, South Dakota, Montana, a n d W y o m i n g .

T h e c o a l resources i n

this area are e s t i m a t e d t o b e 4 0 % of t h e U . S . t o t a l reserves.

The North

C e n t r a l P o w e r S t u d y ( 1 ) estimates t h a t b y 1980 a steam-fired g e n e r a t i n g c a p a c i t y o f 53,000 M W w i l l exist i n a n area b e t w e e n C o l s t r i p , M o n t a n a , a n d G i l l e t t e , W y o m i n g . E a c h 1000 M W of p o w e r g e n e r a t e d w i l l r e q u i r e c o n s u m p t i o n o f a p p r o x i m a t e l y 4 m i l l i o n tons of c o a l / y r .

Thus, the total

coal consumption w i l l be approximately 210 m i l l i o n tons/yr. p u t this c o a l c o n s u m p t i o n i n p e r s p e c t i v e ,

T o help

the D e p a r t m e n t of I n t e r i o r

118 In Trace Elements in Fuel; Babu, S.; Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

10.

ABEL AND RANCiTELLi

Instrumental

Neutron Activation

Analysis

119

e s t i m a t e d t h a t 326 m i l l i o n tons of c o a l w e r e u s e d for e l e c t r i c a l g e n e r a t i o n i n the e n t i r e U n i t e d States i n 1970 ( 2 ) .

T h e r e f o r e , the e s t i m a t e d 210

m i l l i o n tons represents a p p r o x i m a t e l y 6 5 % of the t o t a l u s e d f o r e l e c t r i c a l g e n e r a t i o n i n 1970. T o illustrate the possible i m p a c t of this t y p e of d e v e l o p m e n t , some f u r t h e r c a l c u l a t i o n s c a n be p e r f o r m e d u s i n g present e m i s s i o n standards and

r e p r e s e n t a t i v e c o a l concentrations.

s u l f u r c o n c e n t r a t i o n of 0 . 6 5 %

F i r s t , i f one uses a n

average

t y p i c a l of l o w s u l f u r w e s t e r n coals a n d


assumes the e s t i m a t e d c o a l c o n s u m p t i o n , 2.7 m i l l i o n tons of s u l f u r d i o x i d e w i l l b e p r o d u c e d p e r year. T h e emphasis i n recent e n v i r o n m e n t a l i m p a c t studies of fossil f u e l p o w e r p l a n t s has b e e n o n s u l f u r d i o x i d e e m i s s i o n a n d associated a c i d rains w h i c h h a v e h a d d e t r i m e n t a l effects o n s u r r o u n d ing vegetation

(3,

4, 5 ) .

T h e r e are F e d e r a l standards to l i m i t s u l f u r

d i o x i d e emissions, a n d the t e c h n o l o g y for s u l f u r r e m o v a l r e q u i r e d to m e e t these standards is d e v e l o p i n g i n s e v e r a l a l t e r n a t i v e p a t h w a y s , a l l s t i l l i n e x p e r i m e n t a l stages. fications

T h u s , t h e r e u n d o u b t e d l y w i l l be n u m e r o u s m o d i -

a n d alterations i n p l a n t d e s i g n before s u l f u r d i o x i d e is r e m o v e d

o n a f u l l - t i m e a n d large-scale basis.

B u t e v e n u n d e r these standards,

e m i s s i o n of 2.1 m i l l i o n tons of s u l f u r d i o x i d e / y r w o u l d b e a l l o w e d , a s s u m i n g a c o a l c o n s u m p t i o n of 210 m i l l i o n tons. S e c o n d l y , i f it is a s s u m e d t h a t the c o a l has a n ash figure of

15%

u p o n c o m b u s t i o n ( w h i c h appears reasonable for these c o a l s ) a n d 9 9 % efficiency is a s s u m e d for the p r e c i p i t a t o r s , 315,000 tons of fly ash c o u l d b e released p e r y e a r u n d e r the p r o j e c t e d c o a l c o n s u m p t i o n . F i n a l l y , the trace constituents b e c o m e i m p o r t a n t factors w h e n s u b s t a n t i a l a m o u n t s of c o a l are b u r n e d . S e l e n i u m , w h i c h is present at a p p r o x i m a t e l y 2 p p m i n c o a l , c o u l d be released at a rate of 210 t o n s / y r , a s s u m i n g 210 m i l l i o n tons of c o a l c o n s u m e d a n d a 5 0 % escape rate d u r i n g c o m b u s t i o n (6).

S i g n i f i c a n t discharges c o u l d also b e e x p e c t e d for H g ,

F , A s , and perhaps Sb, Z n , a n d C u . T h u s i t becomes a p p a r e n t that, for the v e r y h i g h p r o j e c t e d

coal

c o n s u m p t i o n i n this r e g i o n , the d i s c h a r g e of trace constituents is i m p o r tant, a n d p o t e n t i a l e n v i r o n m e n t a l i n t e r a c t i o n a n d effects w a r r a n t i m m e diate attention.

T h e r e has b e e n some a t t e n t i o n g i v e n to

radioactive

elements i n c o a l a n d t h e i r release d u r i n g c o m b u s t i o n (7, 8,9).

However,

the stable e l e m e n t trace constituents are p e r m a n e n t p o l l u t a n t s of

the

e n v i r o n m e n t , a n d t h e i r i m m e d i a t e a n d p o t e n t i a l l o n g - t e r m effects s h o u l d be investigated. R e s e a r c h i n d i c a t e s t h a t a significant f r a c t i o n ( 5 0 - 9 0 % ) of m e r c u r y is v o l a t i l i z e d a n d lost d u r i n g c o a l c o m b u s t i o n (10, 11, 12)

a n d that m a n y

of the p o t e n t i a l l y h a z a r d o u s trace elements a p p e a r c o n c e n t r a t e d finer p a r t i c u l a t e emissions (13,

14).

upon

S e v e r a l investigators h a v e o b s e r v e d

e n r i c h m e n t of these h a z a r d o u s elements u p o n p a r t i c u l a t e s i n u r b a n areas

In Trace Elements in Fuel; Babu, S.; Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

120

TRACE

(15-23),

i n remote

C a n a d a (25),

ELEMENTS

locations s u c h as A n t a r c t i c a (24)

a n d i n the u p p e r a t m o s p h e r e

IN

FUEL

and Northern

(26).

T h e r e are several factors w h i c h m a k e n e u t r o n a c t i v a t i o n analysis (NAA)

a n a p p r o p r i a t e t e c h n i q u e for i n v e s t i g a t i n g p o t e n t i a l p o l l u t a n t s

i n c o a l a n d the c o m b u s t i o n process.

F i r s t , the m u l t i - e l e m e n t n a t u r e of

N A A is u s e f u l because of the l a r g e n u m b e r of p o t e n t i a l e l e m e n t a l p o l lutants, s u c h as Se, H g , A s , Z n , N i , S b , a n d C d . A l s o , the use of e l e m e n t a l ratios m a d e possible b y the m u l t i - e l e m e n t c a p a b i l i t y facilitates the u n d e r


s t a n d i n g of c h e m i c a l b e h a v i o r d u r i n g the c o m b u s t i o n process. E l e m e n t a l ratios h a v e b e e n u s e d p r e v i o u s l y i n u r b a n ( 1 5 ) (26)

studies.

and upper atmospheric

S e c o n d l y , the s e n s i t i v i t y a n d s e l e c t i v i t y of N A A a l l o w s

d e t e r m i n a t i o n of m a n y elements present at v e r y l o w concentrations ( p p m or l o w e r ) , a n d the results are unaffected b y m a t r i x interferences.

This

s e n s i t i v i t y also a l l o w s analysis of v e r y s m a l l samples. F i n a l l y , t h e cost of N A A w h e n c o n d u c t e d as a m u l t i - e l e m e n t a n a l y t i c a l t o o l is c o m p e t i t i v e w i t h m o r e c o n v e n t i o n a l a n d less sensitive t e c h n i q u e s o n the

cost-per-

e l e m e n t - p e r - s a m p l e basis. Battelle (INAA)

has

developed

instrumental neutron

a c t i v a t i o n analysis

t e c h n i q u e s w h i c h p e r m i t v e r y sensitive a n d accurate

multi

e l e m e n t analysis of a p p r o x i m a t e l y 40 elements i n c o a l a n d fly ash. T h e s e t e c h n i q u e s , w h i c h w i l l b e d e s c r i b e d i n this w o r k , f o r m the basis extensive e n v i r o n m e n t a l studies of the effluent f r o m c o a l - p o w e r e d

for gen

e r a t i n g f a c i l i t i e s a n d other p o l l u t i o n sources. Experimental T h e s e t e c h n i q u e s are d e s i g n e d to m i n i m i z e b o t h the a c t u a l w o r k i n g t i m e , r e q u i r e d a n d the a n a l y t i c a l u n c e r t a i n t i e s i n s a m p l e analysis. S a m p l e p r e p a r a t i o n a n d n e u t r o n a c t i v a t i o n p r o c e d u r e s are b a s e d o n p r o v e d a n a lytical and microanalytical techniques. reliability, and accuracy

T h e unusually h i g h sensitivity,

are a c h i e v e d t h r o u g h a c h o i c e of

optimum

i r r a d i a t i o n a n d c o u n t i n g times for the γ-ray d e t e c t i o n systems. Sample Preparation. T h e c o a l a n d fly ash samples are w e i g h e d i n t o s m a l l bags f o r m e d b y f o l d i n g a n d h e a t - s e a l i n g p o l y c a r b o n a t e

film.

The

openings are also heat-sealed after the samples are p l a c e d i n t o t h e p o l y c a r b o n a t e bags.

T h e p o l y c a r b o n a t e film, s u p p l i e d b y N u c l e o p o r e , is the

stock m a t e r i a l u s e d for N u c l e o p o r e p o l y c a r b o n a t e filters a n d is d e s i r a b l e b e c a u s e of its l o w trace m e t a l content.

T h e heat s e a l i n g is a c c o m p l i s h e d

u s i n g a T e f l o n - c o a t e d " Q u i k S e a l " t h e r m a l i m p u l s e sealer m a n u f a c t u r e d b y N a t i o n a l I n s t r u m e n t C o . T h e p o l y c a r b o n a t e bags are t h e n p l a c e d i n t o a c l e a n p o l y e t h y l e n e v i a l ( a p p r o x i m a t e l y 2.5 c m l o n g X dram).

1.0 c m I D - 2 / 5

T h e v i a l c o n t a i n i n g the c o a l a n d fly ash samples is t h e n p l a c e d

i n t o a n o t h e r c l e a n v i a l (5.5 c m l o n g X

1.43 c m I D - 2 d r a m ) p r i o r to

neutron activation.


10.

ABEL AND RANCiTELLi

Table I.

Neutron

Activation

121

Analysis

Irradiation and Counting Procedures for Coal and Fly Ash

IRRADIATION INTERVAL/ DECAY NEUTRON FLUX* INTERVAL


Instrumental

COUNT INTERVAL

INSTRUMENTATION

1,000-10,000 MIN

Nal σΐ) MULTI-DIMENSIONAL γ - R A Y SPECTROMETER

K, Th, U

(15-1 min/lxl(r 10 Ml Ν

5 MIN

Ge (Li)

Al, Br, CI, Cu, Mg, Mn, Na, Ti, V

6-8 hrs/5xl0 1 2

10 MIN

Ge (Li) OR ΑΝΤΙ-COINCIDENCE SHIELDED Ge (Li)

As, Au, Ba, Br, Ca, K, La, Lu, Na, Sm, Yb

4-7 DAYS

- 3 0 DAYS

ELEMENTS DETERMINED

Ag, Eu, Sb, Tb,

100-1,000 MIN

Ce, Co, Cr, Cs, Fe, Hf, Hg, Ni, Rb, Se, Se, Sr, Ta, Th, Zn

* NEUTRONS/CM2/SEC

S t a n d a r d s u s e d f o r comparators are either w e l l d o c u m e n t e d m a t e r i a l s ( U . S . G . S . B C R - 1 Basalt, N B S O r c h a r d Leaves, N B S Bovine L i v e r , etc.) or a r e p r e p a r e d i n t h e l a b o r a t o r y b y p i p e t t i n g k n o w n q u a n t i t i e s of ele ments onto h i g h p u r i t y cellulose m a t e r i a l . S t a n d a r d s a r e w e i g h e d

into

p o l y c a r b o n a t e a n d p a c k a g e d f o r i r r a d i a t i o n i n t h e same m a n n e r as t h e samples. Neutron Activation Analysis. T h e analysis consists o f t w o i r r a d i a t i o n p e r i o d s a n d three c o u n t i n g intervals as s h o w n i n T a b l e I . G a m m a ray

spectrometry

is a c c o m p l i s h e d

b y state-of-the-art

Ge(Li)

diodes,

t y p i c a l l y w i t h 1 5 - 2 0 % efficiency r e l a t i v e to 3 X 3 " N a l ( T l ) detector a n d < 2 K e V r e s o l u t i o n ( f u l l w i d t h a t h a l f m a x i m u m ) at t h e 1332 K e V energy.

6 0

Co

T h e γ-ray spectra f r o m samples a n d standards a r e ' stored o n

m a g n e t i c tape a n d t h e d a t a r e d u c e d b y a P D P - 1 5 c o m p u t e r .

A computer

p r o g r a m (27) w a s d e v e l o p e d to i d e n t i f y t h e r a d i o n u c l i d e s present f r o m t h e i r c h a r a c t e r i s t i c γ-ray energies, c a l c u l a t e n e t peak areas, a n d c o n v e r t net p e a k areas to element w e i g h t s b y d i r e c t c o m p a r i s o n to k n o w n s t a n d ards, thus c a l c u l a t i n g t h e c o n c e n t r a t i o n of t h e elements i n t h e o r i g i n a l samples. T a b l e I I s u m m a r i z e s the parameters w h i c h relate to t h e m e a s u r e m e n t of e a c h element: n e u t r o n a c t i v a t i o n p r o d u c t s , h a l f - l i v e s , γ-ray energies, lengths of i r r a d i a t i o n , d e c a y , a n d c o u n t i n g . A l s o l i s t e d are t h e possible i n t e r f e r i n g r a d i o n u c l i d e s a n d i n t e r f e r i n g reactions p r o d u c i n g t h e same isotopes f r o m another element w h i c h w e r e necessarily e v a l u a t e d . t a b l e is s u b d i v i d e d i n t o three sections r e p r e s e n t i n g t h e elements

This deter

m i n e d d u r i n g e a c h o f t h e three c o u n t i n g i n t e r v a l s . T h e i n t e r f e r i n g reactions w e r e e v a l u a t e d b y i r r a d i a t i o n of p u r e ele m e n t standards w i t h corrections

applied where

necessary.

T h e only


122

TRACE ELEMENTS

Table I I - A .

I N FUEL

Nuclear D a t a Relating to the Measurement of the Elements in Coal and Fly A s h INTERVAL-0.5-1.0 Ml Ν C - 1x1013 NEUTRONS/cm2/sec


ELEMENT

TARGET ISOTOPE

ISOTOPIC ABUNDANCE

< % )

PRODUCT NUCLIDE

HALFLIFE

THERMAL NEUTRON CROSS SECTION

A.

2.31m

0.24

Br

17.6m

8.5

BEST y FOR MEASUREMENT (KEV)

NUMBER OFy's PER 1000 DECAYS

1779

1000

NONE

ul

617

70

666(10)

108

1643

380

2170(470)

NONE

1039

90

NONE

70

b

Al

27

AI

100

B

Br

7

V

50.5

80

CI

37

CI

24.5

*CI

37.3m

b 0.4 b

Cu

65

Cu

30.9

«Cu

5.10m

2.3

POSSIBLE INTERFERING NUCLIDE IN DIODE MEASUREMENT

ASSOCIATED y-RAYS KEV (yls/1000 DISINTEG)

POSSIBLE INTERFERING NUCLEAR REACTIONS PRODUCING NUCLIDES OF INTEREST

^Siln.pA

Nd(1776) Ag(614)

31

Ρ(η,α)

80

Kr(n.p» 8 0 Br

*ΑΓ(η.ρ)3ΐ Κ(η,α) « C l

b

Ga(1040)

71

Zn(1040) 69

Mg

Mn

Na

Ti

Mg

26

55

Mn

Na

23

50

Ti

11.2

27

100

9.45m

Mg

^Mn

100

24

5.3

Na

51

0.027 b

2.58h

13.3

0.53

15.0Π

Ti

5.79m

0.14

844

700

1014

300

847

990

1811

290

b

1369

1000

b

320

b

M(X840) u l Nd(84D 87 Kr(846) 56ΜΠ(847)

180(70)

101

ÏJÎMol 1012) tat 1016) ^ S n d O l T ) 188ReU018) 15

2110(150)

27

Mg(844)

2754(1000)

950

v

51

99.8

52

Table II-B.

V

3.76m

4.9

b

1434

As

TARGET ISOTOPE

75

AS

ISOTOPIC ABUNDANCE

(%> 100

117

Cd(1373

Z7

Au

100

p^Mn

,Mg(n,p)24Na AI(n,a) 2 4 N a

1

NONE

Ru(317)

1 3 9

BZm

Ta(318)

^Crln.a)

51

Ti

{W*V

Ba( 1430)

Mn(n,a) V 52

Nuclear Data Relating to the Measurement of the Elements in Coal and Fly A s h

PRODUCT HALFNUCLIDE LIFE

76

As

26.5h

THERMAL NEUTRON BEST r FOR CROSS MEASUREMENT (KEV) SECTION

4.5 b

559

j

NUMBER OF r s PER 1000 DECAYS

430

ASSOCIATED Τ-RAYS KEV


(Y's/1000DISINTEG) 1220(50) 1440(7)

0s(558)

193

114m

POSSIBLE INTERFERING NUCLEAR REACTIONS PRODUCING NUCLIDES OF INTEREST

ln(558) 82Br1554)

As(562) 122Sb(564)

Au

Mg

JJ?Pt(317) f_V

160

14(

la(398)

67

79

Nd(398) 233PaG98>

147

75se(401)


24

Na

Eu(n.p.

153

Sm

Gd(n,a)

153

Sm

153

182

156

Yb

42

Ce«n.p» 1 4 0 La

Eu(1596)

177m Lu(2M ) 199Au(2fjg) Na

Ca(n.p. 4 2 K

Sc(n.a)

NONE

10.

Instrumental

A B E L AND RANCITELLI

Table II-C.

Neutron Activation

123

Analysis

Nuclear Data Relating to the Measurement of the Elements in Coal and Fly Ash IRRADIATION PARAMETERS j

ISOTOPIC ABUNDANCE (%)

TARGET ISOTOPE

ELEMENT

48.65

Ag

PRODUCT HALFNUCLIDE LIFE

110m

Ag

THERMAL NEUTRON CROSS SECTION

3b

255(1

BEST Τ FOR MEASUREMENT (KEV)

658

NUMBER OFY's PER 1000 DECAYS

960

680(160) 706(190)

POSSIBLE INTERFERING NUCLEAR REACTIONS PRODUCING NUCLIDES OF INTER


ASSOCIATED 7 -RAYS KEV (Y's/IOOODISINTEG)

Eu

1 1 (

152

764(230) 818(80)

113

Wp»

1 1 0

ln(n.a.

%

U

° %

140

Ce

885(710) 937(320) 1384(210) 1505(110) Ce

140

Ce

88.48

141

Ce

32.5d

0.6 b

145

480

NONE

Pa(145) 127Xe(145)

Fe(142)


59

177m

Co

59

Cr

100

Co

4.31

Cr

50

60

51

Co

Cr

5.24y

27.8d

37 b

17 b

1173

1000

1332

1000

320

90

NONE

Lu

Major, Minor, and Trace Element Composition of Coal and Fly Ash, as

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