r. . b F - 6

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

0 INCREASED RECYCLE RATE A ADIPIC ACID ADDJTION' 0 DBA ADDITION

TIME, years

Figure 6. Cumulative Present Cost o f Options foi- Improving Springfield City Utilities' SWPP Scrubber (Chang and Mobley, 1983).

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I V . KATT DECONTAMINATION FOR BOILER FUEL

A. BACKGROUND

I n a t y p i c a l process fo r a i r o x i d a t i o n of cyclohexane t o produce

cyclohexanone and cyclohexanol (KA), a r e f i n i n g s tep i s u s u a l l y

included. I n our process the h igh b o i l i n g res idue from the

r e f i n i n g process i s c a l l e d KA Topper T a i l s , o r KATT.

very h igh organic content, v a r i a b l e water conten t and h igh metals

concentrat ion. I n a d d i t i o n t o d isso lved water i n the o i l phase,

there i s a separate aqueous phase amounting t o as much as 50% o f

the t o t a l weight. The r e l a t i v e dens i t y d i f f e r e n t i a l between the

two phases would reverse w i t h change i n temperature, making

cons is ten t phase separat ion d i f f i c u l t . Even i f the phase separa-

t i o n were poss ib le as a pretreatment f o r burn ing of the o i l phase

a t the p l a n t b o i l e r s , t he h igh metal content (sodium and boron)

would c rea te b o i l e r cor ros ion and tube f o u l i n g problems. As p a r t

o f the waste reduct ion/recovery e f f o r t , a development program was

thus undertaken t o f i n d ways t o overcome the above d i f f i c u l t i e s

so t h a t the heat ing value i n t h i s res idue cou ld be recovered and

the waste d isposal burden reduced.

KATT has

B. LAB SCREENING AND COLUMN TEST

A l abo ra to ry screening t e s t was conducted t o s e l e c t the combina-

t i o n o f f a c t o r s fo r ach iev ing des i red responses. The manipulated

fac to rs and the responses a re l i s t e d i n Table 1.

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Table 1. Factors Evaluated i n Lab Screening Study f o r KATT

Manipulated Factors

Method o f c rea t ing density d i f f e r e n t i a l

Ex t rac tant

Temperature

Extractant/KATT r a t i o

Res pon ses

Density d i f fe rence between two phases

Time f o r complete separation

Loss o f organics

Metal removal

Undesirable chemical reac t ion

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C.

Th is l a b screening i d e n t i f i e d t h a t Waste L iquor was the bes t

choice f o r cons is ten t phase separat ion, good metal removal, and

minimum loss o f organics t o the ex t rac tan t . Q u a l i t a t i v e tempera-

t u r e e f f e c t s were understood and the minimum extractant/KATT

r a t i o was determined.

Fol lowing l a b screening, a batch s imu la t ion of 2-stage continuous

countercurrent e x t r a c t i o n w i t h simultaneous phase separat ion was

conducted fo r p lanning a column t e s t . The s imu la t ion run was

made a t 60°C and an Extractant/Residue r a t i o o f 1:l. Results

showed sa t i s fac to ry metal removal. A column t e s t us ing a 1"

York-Schibel column was then conducted t o opt imize the process.

FULL-SCALE OPERATION

Data from the column t e s t were

i n s t a l l a t i o n t o separate water

a p p l i c a t i o n was f i l e d and the

used t o sca le up fo r a f u l l - s c a l e

and metal f r o m KATT. A paten t

patent was subsequently granted

(Chi and Lester, 1981). A c e n t r i f u g a l e x t r a c t o r was used t o

shor ten t h e contac t t ime and thereby reduce any chemical

reac t ions between the two feed streams.

The washed KATT became a c lean f u e l f o r f i r i n g together w i t h

pr imary f u e l i n one o f t he p l a n t b o i l e r s f o r e f f i c i e n t recovery

of t he heatincr value. A t t h e Dower house end. sDecial s ta in less

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s t e e l burner guns and t i p s are used because o f the cor ros ive

nature o f t h e byproduct waste. This process o f byproduct

u t i l i z a t i o n has been i n operat ion f o r f o u r years.

V. EXCESS AGS INCINERATION

The excess Waste L iquor a f t e r sales f o r f l u e gas d e s u l f u r i z a t i o n and

use i n KATT washing i s i n c i n e r a t e d i n the p l a n t b o i l e r f o r f u e l value

recovery.

waste l i q u o r i s removed by evaporation.

used f o r t h i s water removal step. The same b o i l e r i s used f o r

concentrated AGS and washed KATT. Because o f t h e r e l a t i v e l y low

heat ing value from t h e h i g h l y oxygenated organic acids, pr imary fuel

i s always f i r e d a t t h e same t ime t o ensure f lame s t a b i l i t y .

P r i o r t o i n c i n e r a t i o n , most o f the water content i n t h e

Low pressure waste steam i s

As more and more process wastes are burned i n t h e conventional indus-

t r i a l b o i l e r s , operator education becomes important because of t h e

increased handl ing o f chemicals which have d i f f e r e n t c h a r a c t e r i s t i c s

from t h e convent ional f u e l s.

commitment i n us ing b o i l e r s f o r byproduct waste disposal (and energy

recovery) i s very important. The i r i n f l u e n c e can f a c i l i t a t e

acceptance o f "chemical operat ions" by t h e u t i 1 i t i e s people.

Another p o i n t i s t h a t upper management I s

c

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V I . REFERENCES

Burke, J.M., R.P. Metcalfe, R. Cmiel, and J.D. Mobley, "Technical and

Economic Evaluat ion o f Organic Acid Add i t i on t o the San Miguel FGD

System," presented a t EPA's Indus t ry B r i e f i n g on the Organic Acid

Enhanced Limestone FGD Process, San Antonio, Texas, J u l y 19 (1984).

Chang, J.C.S. , and J.H. Dempsey, " P i l o t P lan t Evaluat ion of Byproduct

Dibas ic Acids as Buffer Addi t ives f o r Limestone Flue Gas Desu l fu r iza-

t i o n Systems," presented a t EPA/EPRI Symposium, Hollywood, F l o r i d a , May 17-20 (1982).

Chang, J.C.S., and J.D. Mobley, "Overview o f EPA's Test ing o f the

Ad ip ic Ac id Enhanced Limestone FGD Process ,'I presented a t EPA's

Indus t r y B r i e f i n g on the Ad ip ic Enhanced Limestone FGD Process,

Sp r ing f i e ld , Missour i , J u l y 15 (1981).

€ h g , S.C.S., and J.D. Mobley, "Test ing and Commercialization of

Byproduct Dibas ic Acids as B u f f e r Add i t i ves fo r Limestone F lue Gas

Desu l fu r i za t i on Systems," Journal o f t he A i r P o l l u t i o n Control

Associat ion, 33, 955-962 (1983).

Chi, C.T. , and J.H. Lester , Jr. , "Decontamination o f KA O i l Refinement

Waste Streams ,I' U.S. Patent 4450291 (1981).

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VI. REFERENCES (Continued)

Dickerman, J.C. and J.D. Mobley, "Technical/Economic Feasibility

Studies for Full-scale Application of Organic Acid Technology for

Limestone FGD Systems," prepared for Presentation at the Eighth FGD

Symposium, November 1-4 (1983).

Glover, R.L., G.E. Brown, J.C. Dickerman, O.W. Hargrove, N.D. Hicks,

D.M. Franley, and J.D. Mobley, "Results of the First Two Years of

Commercial Operation of an Organic-Acid-Enhanced FGD System,"

presented at EPA's Industry Briefing on the Organic-Acid-Enhanced

Limestone FGD Process, San Antonio, Texas, July 19 (1984).

Hargrove, O.W., J.D. Colley, and G.E. Brown, "Status of Adipic Acid

Enhanced FGD System Demonstration at Springfield City Utilities

Southwest Power Plant ,I' presented at EPA/IERL Industry Briefing,

Springfield, Missouri , July 15 (1981).

Lester, J.H., Jr., and D.E. Danly, "Buffered Flue Gas Scrubbing System

Using Adipic Acid Byproduct Stream," U.S. Patent 4423018, December 27

(1983). This patent has been dedicated to the public.

Mobley, J.D., M. Cassidy, and J. Dickerman, "Organic Acids can Enhance

Wet Limestone Flue Gas Scrubbing," Power Engineering, May (1986).

-

~

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VI. REFERENCES (Continued)

Rochelle, G.T., and C.J. King, "The Effect of Additives on Mass

Transfer in CaCO, or CaO Slurry Scrubbing of SO, from Waste Gases,''

Industrial Engineering Chemical Fundamentals, 16, 67-75 (1977).

Smith, M.P., M.T. Melia, B.A. Laseke, and N. Kaplan, "Recent Trends in

Utility Flue Gas Desulfurization," Symposium on Flue Gas Desulfuri-

zation - Houston , Texas, EPA-600/9-81-019a, October (1980).