BYPRODUCT UTILIZATION IN ADIPIC ACID MANUFACTURE BY C. T. Chi and J. H. Lester Monsanto Chemical Company P.O. Box 12830 Pensacol a, F1 ori da 32575 @MAsTE MINIMIZATION WORKSHOP New Orleans, Louisiana November 11-13, 1987 ABSTRACT This presentation provides a case study of beneficial utilization of two waste streams from adipic acid manufacture. from crystallization of adipic acid. from refining of cyclohexanol. The first stream, containing adipic, glutaric, and succinic acids, the mixture is referred to as AGS, was found to be very effective in improving the efficiency of 1 imestone scrubbers for removing SO, from coal-fired power plant flue gases. Typically, SO, removal efficiency can be increased from less than 80% to over 90%. AGS is currently being used at several public utility plants to bring the existing scrubbers into compliance. The unused portion of AGS is incinerated in the adipic manufacturing plant boilers as a waste disposal and energy recovery enhancement. An ion exchange process is used to remove metals as a pretreatment. The first stream is a filtrate The second is a distillation residue A portion of the AGS stream is also used to convert a waste distillation residue from cyclohexanol manufacture into a clean boiler fuel. The residue is an oily waste, containing metals and a hard-to-separate aqueous phase. Through liquid-liquid extraction and ion exchange, sodium and boron in the oily waste are removed by washing with AGS in a contactor. . The aqueous phase is separated at the same time. The residue is converted into a high BTU clean burning fuel. CTC101/VG46
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BYPRODUCT UTILIZATION IN ADIPIC ACID MANUFACTURE
BY
C. T. Chi and J. H. Lester Monsanto Chemical Company
P.O. Box 12830 Pensacol a, F1 ori da 32575
@MAsTE MINIMIZATION WORKSHOP New Orleans, Louisiana November 11-13, 1987
ABSTRACT
This presentation provides a case study of beneficial utilization of two waste streams from adipic acid manufacture. from crystallization of adipic acid. from refining o f cyclohexanol.
The first stream, containing adipic, glutaric, and succinic acids, the mixture is referred to as AGS, was found to be very effective in improving the efficiency of 1 imestone scrubbers for removing SO, from coal-fired power plant flue gases. Typically, SO, removal efficiency can be increased from less than 80% to over 90%. AGS is currently being used at several public utility plants to bring the existing scrubbers into compliance. The unused portion of AGS is incinerated in the adipic manufacturing plant boilers as a waste disposal and energy recovery enhancement. An ion exchange process is used to remove metals as a pretreatment.
The first stream is a filtrate The second is a distillation residue
A portion of the AGS stream is also used to convert a waste distillation residue from cyclohexanol manufacture into a clean boiler fuel. The residue is an oily waste, containing metals and a hard-to-separate aqueous phase. Through liquid-liquid extraction and ion exchange, sodium and boron in the oily waste are removed by washing with AGS in a contactor. . The aqueous phase is separated at the same time. The residue is converted into a high BTU clean burning fuel.
CTC101/VG46
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BYPRODUCT UTILIZATION I N A D I P I C ACID MANUFACTURE
I. INTRODUCTION
A t the Monsanto Pensacola s i t e , there i s constant e f f o r t t o reduce the
waste from manufacturing processes. The fo l l ow ing approach i s taken:
1. Character izat ion of wastes a t t h e i r sources.
2. With in process recyc le and reuse.
3. External u t i l i z a t i o n .
This p resenta t ion provides a case study of combined i n t e r n a l and
ex terna l u t i l i z a t i o n of two major waste streams.
l i q u o r from c r y s t a l l i z a t i o n of a d i p i c ac id .
ment res idue from cyclohexanol r e f i n i n g and recovery.
The f i r s t i s a waste
The second i s a r e f i n e -
The sources of these two byproduct purge streams a re i l l u s t r a t e d i n
F igure 1. The waste l i q u o r conta ins a t o t a l o f about 25 percent
d ibas i c acids, i nc lud ing a d i p i c ac id , succ in i c ac id , and g l u t a r i c
acid; t he r e s t i s comprised o f water and minor impur i t i es . The
ref inement res idue contains p r i m a r i l y organic es ters and var ious
amounts o f a second aqueous phase.
i n the second stream.
Sodium and boron are a l so present
AIR I
NITRIC AClO
I c REFINEMENT
SYSTEM
RESIDUE (WASTE STREAM 2)
WASTE LIQUOR (WASTE STREAM 1)
FIGURE 1 SOURCES OF BYPRODUCT WASTE STREAMS
I N I
I
I
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11. OVERALL SCHEME
The overall scheme for the integrated approach is illustrated in
Figure 2.
concentrating to over 50% organic solid for sales to coal-fired
utilities for enhancement of flue gas desulfurization. The product is
sold as "AGS Mixture." A portion of the un-concentrated waste liquor
is used to wash the refinement residue which is subsequently burned in
the plant boilers for energy recovery. The unused and unsold portion
of AGS is also burned in the plant boilers for energy recovery. Other
markets for AGS and sales o f certain forms of the refinement residue
are being pursued actively.
Most of the waste liquor is directed to an evaporator for
The above byproduct utilization scheme for these two streams achieves
about 30% volume reduction and greater than 90% total carbon reduc-
tion. The scheme has converted a pollution control problem into a
profitable operation. The three major segments, AGS for flue gas
desulfurization, washing of the refinement residue, and energy
recovery from excess waste liquor and the refinement residue are
further detailed in the following sections.
WASTE LIQUOR
REFINEMENT RESIDUE
# - - - - - - - - - -
I I I I 1
I
EVAPORATION - FLUE GAS DESULFURIZATION
I__cL
- STEAM GENERATION
d WATE
I I
WASTE DISPOSAL
I I I - - - -
FIGURE 2
OVERALL SCHEME FOR BYPRODUCT UTILIZATION AND WASTE DISPOSAL '
I
f
I I
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111. AGS FOR FLUE GAS DESULFURIZATION
A. BACKGROUND
A t y p i c a l modern c o a l - f i r e d power p l a n t may emit as much as
2,000,000 SCFM waste gas conta in ing 2,000 ppm o f SO,. This
s u l f u r d iox ide f requent ly must be removed f r o m the f l u e gas,
usual ly w i t h a scrubber, t o meet governmental regu la t ions .
Sul fur d iox ide emissions are associated w i t h the ac id r a i n
problem. The m a j o r i t y o f f l u e gas desu l fu r i za t i on (FGD) systems
t h a t a r e e i t h e r i n operat ion o r under p lanning are calcium-based
l i m e o r l imestone processes because of system s i m p l i c i t y and
economics (Smith e t a l . , 1980). A t y p i c a l l imestone FGD system
i s shown i n F igure 3. Although t h i s FGD technology has been
under development fo r over 18 years, many of t he e x i s t i n g l ime-
stone systems have problems i n meeting design l e v e l s o f reagent
u t i 1 i z a t i o n and SO, removal (Burke, e t a1 . , 1984). -
Most problems w i t h SO, removal and l imestone u t i l i z a t i o n are
symptoms of poor mass t rans fe r . According t o Chang and Mobley
(1981), l imestone ‘scrubber performance i s 1 i m i t ed by two pH
extremes: 1) low pH near the gas - l i qu id i n t e r f a c e which decreases
the the SO, s o l u b i l i t y and absorpt ion rate; 2) h igh pH near the
1 i q u i d - s o l i d in te r face which lowers the 1 imestone so lub i 1 i ty and
d i s s o l u t i o n ra te . These two extremes can be moderated by us ing a
so lub le bu f fe r add i t i ve .
TO STACK
BALLMILL
I L.
' FLUEGAS FROM BOILER
RECYCLE b+-- FEED COMPRESSORS
AIR FOR FORCED OXIDATION. I
HOLD TANK !
21---., THICKENER OVERFLOW
TO DEWATERING AIR
SPARGER
ADIPIC
T LIMESTONE STORAGE
L LIMESTONE
I cn I
70.1 B 13- 1
Figure 3 . Flow Diagram for a Typical Limestone Scrubber (Hargrove e t aZ. 1981).
1
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It has been known since 1977 that certain organic additives are
useful as buffers and are effective in enhancing mass transfer.
Adipic acid and isophthalic acid were identified as "fully
effective" by Rochelle and King (1977). Since then the EPA has
sponsored pilot, prototype, and full-scale demonstration testing
o f adipic acid to quantify its effectiveness, loss, and other
aspects as an additive.
solubility in water, low volatility, chemical stability, non-
toxicity, high availability, and low cost (Dickerman and Mobley,
1983). Demonstrated benefits of adipic acid enhancement include
(Chang and Dempsey, 1982):
Adipic acid was selected because o f its
Increased SO, removal
Decreased 1 imestone consumption
Decreased waste sludge volume
Reduced operating cost
Expanded FGD system flexibility
During EPA's test program for adipic acid, the concept of using
byproduct AGS (also called DBA, dibasic acids) as a lower lost
a1 ternative was introduced by Monsanto (Lester and Danly, 1983).
A separate program by the EPA was conducted to evaluate by-
products as alternatives to pure adipic acid.
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B. LAB AND PILOT TEST RESULTS
~
Fo l lowing labora tory charac ter iza t ion , p i l o t p l a n t (0.1 MW) t e s t s
were conducted by the EPA f o r byproduct organic a c i d from f o u r
sources, i nc lud ing two from a d i p i c a c i d manufacture (Chang and
Dempsey, 1982). F igure 4, taken from the same reference, shows
t h a t both DBA's enhanced SO, removal s i g n i f i c a n t l y . With an
a d d i t i o n o f 50 meq / l i t e r (about 3300 ppm) o f DBA, the SO, removal
e f f i c iency was increased from 50% t o 90%.
t h a t both DBA's can improve SO, removal as e f f e c t i v e l y as a d i p i c
acid.
~
F igure 4 a l so shows
A l abo ra to ry t e s t on t h e e f f e c t o f AGS a d d i t i o n was a l so con-
ducted a t Monsanto. The bench scale apparatus had a 1 ACFM
capaci ty, u t i l i z i n g syn the t i c f l u e gas.
t he r u n s - i s shown i n F igure 5. Dur ing t h i s run, SO, removal
e f f i c i e n c y increased from 59 t o 85% i n 10 minutes.
AGS concentrat ion i n the scrubbing l i q u o r was 2200 ppm.
S t r i p c h a r t from one o f
The u l t i m a t e
C. COMMERCIAL APPLICATION
The f i r s t commercial-scale t e s t us ing byproduct DBA was conducted
i n S p r i n g f i e l d City U t i l i t y ' s Southwest Power P lan t (SWPP)
u t i l i z i n g AGS from Monsanto. This power p l a n t has a 194 MW
c o a l - f i r e d u n i t designed t o burn 3.5-4% s u l f u r coal . P r i o r t o
t h i s t e s t the p l a n t ' s FGD system was unable t o b r i n g the SO,
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IO0
90 $ a
J 80 cl
5 70 s U 60
$ 50 m
4Q
.. / 0 - p H = 5.0 /'a A ADIP IC ACID
/ - A' a /
V # I D8A
U s 2 DBA
0 1000 2000 3000 4000 ADIPIC A C l D CONCENTRATION ppm
1 1 I I I I 0 10 20 30 40 5 0
TOTAL ORGANIC ACID, meg / liter
Figure 4. Effect o f Organic Acid on SO2 Removal a t IERL- RTP P i l o t Plant (Chang and Dempsey, 1982).
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Figure S. S t r i p Chart Response t o AGS Addition a t Monsanto Bench-Scale SO, Removal U n i t .
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emission into compliance. Test results showed that addition of
530 ppm of AGS mixture increased removal efficiency from 58% to
85% thus meeting the regulatory requirements (Chang and Mobley,
1983).
DBA additive to other alternatives. As shown in Figure 6, the
use of DBA was a clear winner (Chang and Mobley, 1983). It was
decided to install permanent facility for operating with DBA
Economical analysis was made to compare the cost of using
additives. Thus, SWPP became the first commercial-scale facility
to utilize DBA in FGD system application for enhanced SO,
removal
Two years after the first commercial application of DBA tech-
nology, SWPP reported not only meeting SOp emission 1 imitations
but also having 98% FGD reliability as compared to 45% relia-
bility prior to the change (Glover, et al., 1984).
Today, more than 11 power plants are either using or considering
€he use of DBA additives for improved FGD performance (Mobley, et
al., 1986). The sale of AGS for FGD has expanded into multi-
mi 1 1 ion-pound-per-year business and is growing . product utilization solves two environmental' problems at once.
Thi s ki nd o f by-
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1 1 1 I I I 1 I 1 1 I 1 1 I 1 A 0 ABSORBER INTERNAL MODIFiCATION