Commercialization of Lime-Limestone Flue Gas ... - ACS Publications

Pilot units have been installed at the Tidd Station of American Electric. Power ... Public Service awarded an additional contract for gas cleaning equ...
3 downloads 0 Views 1MB Size
10 Commercialization of Lime-Limestone Flue

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: April 1, 1975 | doi: 10.1021/ba-1975-0139.ch010

Gas Scrubbing Technology RICHARD S. ATKINS Research-Cottrell, Inc., Bound Brook, N. J. 08805 Research-Cottrell

has demonstrated the commercial

bility of limestone flue gas desulfurization installation.

Certain chemistry and process

were taken into account in designing

availa-

on a 115

MW

considerations

and operating these

systems. Methods have been developed to minimize

the

occurrence of potential problems.

Q i n c e the first large sulfur dioxide control system was installed at the ^

Battersea plant in London, it has taken almost 50 yrs for calcium-

based scrubbing technology

to become

commercially acceptable.

In

1926, the 125 M W coal-fired Battersea power plant was equipped with a spray packed tower and final alkaline wash section which removed more than 90%

of the sulfur dioxide and particulate ( I ) .

Thames River

water provided most of the alkali for absorption, and about 20% made up from lime addition.

was

The process operated in an open-loop

manner, returning spent reagent to the Thames. Subsequent programs to prevent water and air pollution supported by Imperial Chemicals Industries L t d . , British Power Authority consultants, and Howden Construction Co. led to the development closed-loop, lime-based, sulfur dioxide removal system.

of a

These types of

systems were installed in 1935 at the Swainsea and in 1937 at the Fulham power plants. They operated successfully until World War II when they were shutdown because the vapor plumes provided aerial guidance to the Luftwaffe. For the next 20 yrs no full-scale development work was performed in this area.

In fact, during the mid-sixties, there were several steps

backward when initial U.S. sulfur dioxide control systems started up and failed. For example, in the boiler injection of limestone followed by wet scrubbing, problems resulted from boiler and preheater rather than flue gas scrubbing. 120 Pfeiffer; Sulfur Removal and Recovery Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

pluggage

10.

ATKINS

Current

Lime-Limestone

Industry

Flue Gas

121

Scrubbing

Status

D u r i n g the last 3 yrs m o r e progress has b e e n m a d e i n c a l c i u m s c r u b b i n g t e c h n o l o g y t h a n d u r i n g the p r e c e d i n g q u a r t e r of a c e n t u r y .

Pres-

e n t l y 2500 M W of c a l c i u m - b a s e d scrubbers are o p e r a t i n g w i t h a n o t h e r 7600 M W u n d e r c o n s t r u c t i o n ( 2 ) .

M a n y of the i n i t i a l l y i n s t a l l e d u n i t s

e x p e r i e n c e d difficulties, b u t the n e w e r installations h a v e p e r f o r m e d better

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: April 1, 1975 | doi: 10.1021/ba-1975-0139.ch010

as the p o l l u t i o n c o n t r o l i n d u s t r y has g a i n e d confidence a n d experience. E P A and pollution industry-supported development programs have c o n f i r m e d m a n y of the process constraints e s t a b l i s h e d d u r i n g the o r i g i n a l H o w d e n - I C I projects ( 3 ) .

T h i s is not to say that w e h a v e m a d e a f u l l

c i r c l e a n d h a v e l e a r n e d no m o r e t h a n w a s a v a i l a b l e 25 yrs ago.

How-

ever, i f our i n i t i a l d e v e l o p m e n t p r o g r a m s h a d b e e n b a s e d o n p r i o r r e search results, w e w o u l d p r o b a b l y b e f u r t h e r a h e a d t o d a y .

T h e major

i m p r o v e m e n t s i n c u r r e n t processes result f r o m the a p p l i c a t i o n of m o d e r n t e c h n o l o g y a n d o p e r a t i n g t e c h n i q u e s to e x t e n d system r e l i a b i l i t y . Research—CottrelP s Status I n t h e mid-1960's R e s e a r c h - C o t t r e l l entered the s u l f u r d i o x i d e c o n t r o l field as a n expert i n p a r t i c u l a t e c o l l e c t i o n b u t as a n o v i c e i n gaseous removal.

I n i t i a l investigations u s e d a

flooded

disc s c r u b b e r

(FDS),

w h i c h is essentially a h i g h e n e r g y v e n t u r i r e q u i r i n g 8 - 1 0 i n . w.c. pressure d r o p for 4 0 - 6 0 % s u l f u r d i o x i d e r e m o v a l . I n s t a l l i n g a series of F D S ' s to i m p r o v e a b s o r p t i o n efficiency r e q u i r e d excessive pressure losses.

There-

fore, R e s e a r c h - C o t t r e l l b e g a n investigations of the F D S i n c o m b i n a t i o n w i t h a p a c k e d t o w e r to increase s u l f u r d i o x i d e r e m o v a l at

moderate

pressure drops. T h e p i l o t p l a n t studies started i n 1966 a n d h a v e c o n t i n u e d ever since. P i l o t units h a v e b e e n i n s t a l l e d at the T i d d S t a t i o n of A m e r i c a n E l e c t r i c P o w e r , the C h o l l a S t a t i o n of A r i z o n a P u b l i c Service, the B i g B r o w n S t a t i o n of Texas U t i l i t i e s , a n d Res ear c h - C o t t r ell's F i n d e r n e R e s e a r c h facility.

D e v e l o p m e n t studies h a v e b e e n s u p p o r t e d b y E P A , b y joint

efforts w i t h utilities, a n d b y this c o m p a n y (4,

5,6).

A s a d i r e c t result of this p i l o t effort, a w e t t e d film p a c k i n g was f o u n d w h i c h exhibits excellent s u l f u r d i o x i d e a b s o r p t i o n w i t h a n e x c e p t i o n a l l y l o w pressure d r o p .

T h i s p a c k i n g has o u t s t a n d i n g mass transfer c h a r a c -

teristics a n d h i g h specific

surface

area.

T h e packing developed

by

M u n t e r s C o r p . is a k e y element i n the limestone-based s u l f u r d i o x i d e r e m o v a l system. L a s t O c t o b e r R e s e a r c h - C o t t r e l l started u p its first gas c l e a n i n g syst e m , a 115 M W

limestone wet

s c r u b b i n g system at A r i z o n a P u b l i c

Service's C h o l l a p l a n t . I n this u n i t p a r t i c u l a t e a n d s u l f u r d i o x i d e are

Pfeiffer; Sulfur Removal and Recovery Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

122

SULFUR

r e m o v e d b y a F D S - p a c k e d t o w e r arrangement.

REMOVAL

AND RECOVERY

B e c a u s e of the results

o b t a i n e d at this c o m m e r c i a l f a c i l i t y a n d f r o m the p i l o t units, the A r i z o n a P u b l i c S e r v i c e a w a r d e d a n a d d i t i o n a l contract for gas c l e a n i n g e q u i p m e n t o n a n e w 250 M W b o i l e r . I n a d d i t i o n , the c o m p a n y is e n g i n e e r i n g 1900 M W of s u l f u r d i o x i d e r e m o v a l e q u i p m e n t for several m a j o r s o u t h w e s t e r n utilities. R e s e a r c h - C o t t r e l l r e a l i z e d that t h e i n d u s t r i a l a n d u t i l i t y m a r k e t s Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: April 1, 1975 | doi: 10.1021/ba-1975-0139.ch010

r e q u i r e d different types of s u l f u r d i o x i d e r e m o v a l e q u i p m e n t .

Therefore,

it c o n t r a c t e d w i t h A b B a h c o V e n t i l a t i o n of S w e d e n to m a r k e t t h e i r s u l f u r d i o x i d e r e m o v a l t e c h n o l o g y i n the U . S . a n d C a n a d a . B a h c o

technology

is p a r t i c u l a r l y a p p l i c a b l e to i n d u s t r i a l b o i l e r a n d process a p p l i c a t i o n s T h e first U . S . B a h c o i n s t a l l a t i o n w i l l h a n d l e seven stoker-type

(7, 8,9).

b o i l e r s at the R i c k e n b a c k e r A i r F o r c e B a s e i n C o l u m b u s , O h i o . Comparison

of Lime—Limestone Wet

Scrubbing

with Other Systems

S i n c e the u t i l i t y i n d u s t r y represents the major m a r k e t for s u l f u r d i o x i d e c o n t r o l systems, it w a s necessary to d e v e l o p

a s i m p l e system

w h i c h w o u l d not r e q u i r e a lot of a t t e n t i o n , be i n e x p e n s i v e to operate, h a v e m o d e r a t e c a p i t a l r e q u i r e m e n t s , a n d not take effort a w a y f r o m t h e i r p o w e r p r o d u c i n g f u n c t i o n . C a l c i u m - b a s e d s c r u b b i n g processes meet a l l of these requirements.

I n a d d i t i o n , the c a l c i u m reagents

are i n e x p e n s i v e a n d

f o r m r e l a t i v e l y i n s o l u b l e r e a c t i o n p r o d u c t s w h i c h c a n be d i s p o s e d of i n s a n i t a r y landfills a n d s l u r r y p o n d s . T h e d i s a d v a n t a g e of c a l c i u m - b a s e d t e c h n o l o g y is the l o w salt s o l u b i l i t y w h i c h necessitates the use of v e r y large a b s o r b i n g surface areas, high liquid

flow

rates, a n d g o o d p H c o n t r o l to p r e v e n t s c a l i n g a n d

p l u g g i n g . M o s t recent t e c h n o l o g i c a l advances are i n the areas of c a l c i u m salt scale p r e v e n t i o n a n d c o n t r o l l e d c r y s t a l l i z a t i o n . S o l u b l e - b a s e d systems h a v e better a b s o r p t i o n c a p a b i l i t i e s a n d l i m i t e d scaling and p l u g g i n g problems.

H o w e v e r they h a v e p r o b l e m s associated

w i t h s o l u b l e salt d i s p o s a l a n d h i g h e r reagent costs.

T h e waste d i s p o s a l

problems have limited their application. B y - p r o d u c t processes h a v e the advantages of s o l u b l e - b a s e d systems b u t h a v e p r o b l e m s associated w i t h m o r e c o m p l e x o p e r a t i o n , i n c r e a s e d c a p i t a l a n d o p e r a t i n g costs, a n d the n e e d to d e v e l o p b y - p r o d u c t m a r k e t s . Therefore,

R e s e a r c h - C o t t r e l l i n i t i a l l y chose to d e v e l o p

calcium-based

s c r u b b i n g t e c h n o l o g y to best m e e t the e x i s t i n g needs of its customers. System

Description

F i g u r e 1 illustrates the c o m p o n e n t s of a t y p i c a l c a l c i u m - b a s e d s u l f u r d i o x i d e s c r u b b i n g system.

F l u e gases enter a q u e n c h i n g section w h e r e

Pfeiffer; Sulfur Removal and Recovery Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

10.

ATKINS

Lime-Limestone

123

Flue Gas Scrubbing

Treated Gas Stack

i

Reheater

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: April 1, 1975 | doi: 10.1021/ba-1975-0139.ch010

4 Mist Eliminator

Water

i Sulfur Dioxide Absorber

Quencher and Particulate Scrubber

Dirty Stack. Gases

Calcium Reagent

Settling Tank

Scrubber Tank

Absorber Tank

Vacuum Filtration

ΠΓ CaS0

3

CaSOi Fly Ash Waste Disposal Figure 1.

Typical calcium-based

sulfur dioxide scrubbing

system

the gas is c o o l e d a n d p a r t i c u l a t e a n d some s u l f u r d i o x i d e r e m o v a l takes place.

T h e q u e n c h e d gas t h e n enters t h e a b s o r p t i o n section w h e r e the

r e m a i n i n g s u l f u r d i o x i d e is r e m o v e d . w a t e r a n d reagent droplets.

F i n a l l y a m i s t e l i m i n a t o r removes

T h e c l e a n e d gas is r e h e a t e d a n d r e t u r n e d

to the stack.

Pfeiffer; Sulfur Removal and Recovery Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

124

SULFUR

REMOVAL

AND RECOVERY

C a l c i u m reagent is a d d e d to the absorber t a n k a n d p u m p e d to the s u l f u r d i o x i d e absorber. M o s t of the spent reagent is r e t u r n e d to the a b ­ sorber tank, a n d p a r t is p r o v i d e d as reagent m a k e - u p to the q u e n c h e r system. T h e spent q u e n c h e r reagent, c o n t a i n i n g p a r t i c u l a t e a n d r e a c t i o n salts, is r e m o v e d f r o m the process as a s l u d g e b l o w d o w n .

Make-up

w a t e r , to c o m p e n s a t e for e v a p o r a t i o n losses a n d s l u d g e b l o w d o w n , is a d d e d p r i m a r i l y as m i s t e l i m i n a t o r w a s h . Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: April 1, 1975 | doi: 10.1021/ba-1975-0139.ch010

U s i n g this g e n e r a l a p p r o a c h , several sulfur d i o x i d e r e m o v a l systems have been developed.

F i g u r e 2 illustrates t h e C h o l l a sulfur d i o x i d e r e ­

m o v a l system w h e r e a m o d e r a t e e n e r g y s c r u b b e r is u s e d for p a r t i c u l a t e r e m o v a l , gas q u e n c h i n g , a n d i n c i d e n t a l sulfur d i o x i d e r e m o v a l . p a c k e d t o w e r is the m a j o r sulfur d i o x i d e a b s o r p t i o n d e v i c e .

The

Make-up

reagent is s u p p l i e d to the p a c k e d t o w e r , a n d the F D S receives reagent f r o m the p a c k e d - t o w e r system.

spent

T h u s reagent flow is c o u n t e r -

c u r r e n t to gas flow for m a x i m u m u t i l i z a t i o n .

INLET GAS

REHEATER Ρ*·

FDS

PACKED TOWER

SCRUBBER

Η >

Η

ι ,

TO SLUDGE DISPOSAL

MAKE-UP WATER

MAKE-UP WATER

y FDS SLURRY TANK

Figure 2.

TOWER TANK

Process flow diagram

R e s e a r c h - C o t t r e l l is also s u p p l y i n g a gas c l e a n i n g system u s i n g a n electrostatic p r e c i p i t a t o r for d r y p a r t i c u l a t e c o l l e c t i o n f o l l o w e d b y m u l t i - s t a g e gas l i q u i d contactor for sulfur d i o x i d e r e m o v a l .

The

stage is a c y c l o n i c q u e n c h e r for gas s a t u r a t i o n a n d m o d e r a t e

a

first

sulfur

d i o x i d e a b s o r p t i o n f o l l o w e d b y a spray a n d p a c k e d - t o w e r section w h e r e the m a j o r s u l f u r d i o x i d e a b s o r p t i o n takes p l a c e . a p p l i e d c o u n t e r c u r r e n t to t h e gas

A g a i n the reagent is

flow.

Pfeiffer; Sulfur Removal and Recovery Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

10.

Lime-Limestone

ATKINS

Process

Flue Gas

125

Scrubbing

Chemistry

T h e c h e m i s t r y i n v o l v e d i n l i m e - l i m e s t o n e s c r u b b i n g is v e r y c o m p l e x because of the l i m i t e d s o l u b i l i t y of the n u m e r o u s reagents a n d r e a c t i o n products.

T h e major c o m p o n e n t s a r e :

Reagent:

Ca, Mg, C 0 , O H 3

F l u e gas: S 0 , S 0 , CO >, 0 , N O , N 0 , N 2

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: April 1, 1975 | doi: 10.1021/ba-1975-0139.ch010

F l y ash:

3

2

L

2

2

N a , C l , K , Fe, C a , M g , Si

T h e m a i n reactions i n c a l c i u m b a s e d s c r u b b i n g are: 1.

D i f f u s i o n of s u l f u r d i o x i d e f r o m the gas phase into the l i q u i d phase, S 0 ( g ) S 0 ( a q ) 2

(1)

2

2. H y d r o l y s i s to f o r m sulfurous a c i d , bisulfite, sulfite, a n d h y d r o g e n ions, S0 (aq) +

H 0 *± H S 0

2

2

2

H S 0 - +± H + + 3