and C.T. Lawson Union Carbide Chemicals and Piastics Co.

tion to einht asuects of a

Rscussed below: with uarticular.em asis on the aspects thHt involve CP' lg gineers most directly.

1; Product Uesign Product desigi has been descnbed as the thiid dimension of a waste-mini- mization program, usually neglected

until after ad*istrative and process changes have been addressed [3J For long-term pollution prevention, how- ever, the design of the product must in fact be the starting point.

The productdesign phase of a thor- h pollution-prevention program

ead to products that are less ss mobile, less persistent, more for recycling or more amena-

eatment It should focus on one

Preventing the products from enter- .iPn the environment

ples to the design of products that are made and marketed for use within CPI plants, whether as supplies, reagents or raw materials.

2. Process Design Process design fora typical CPI facility generates a number of solid, liquid, and gaseous waste streams. These can be broken down into ten categories:

Unreacted raw materials Impmities in the reactants Undesmble bwroducts Spent auili&materials (catalys&,-

9 kasing their removal ;from the oils, solvents, others) $nvironment OffspecEcatiod product 5, Facilitating .theu. ability .to ne' 0 Maintenance wastes and materials $processed Material generated during startun o r

sign is often associated with consumer 6 Material .cauied bvprocess upsets or uroducts. whereas the focus of this &- bv suills

Environmentally sound product de- .shutdown

>le is pollution prevention within the ' .:Material generated dUnng proaucr, CPI plant. Even so, numerous opportu- and waste handling, sampling, starage nities can arise to apply the same princi- . or treatment

Fugitive sources These wastes can be classified .as

either variable or fixed. The. former 'Mr. W u o d N rith W n h W i d e Chem& and P k k Ca. while vribng this h d o ~ m o ~ P r b . b o ~ ~ ~ R . f i ~ c e [ ~ v h l c h f ~ ~ a o o t h c ~ ~ h t u ~ v h r n d L N u i n g ~ f f ~ v . o p n d a n ( n *

*m Pouution p m c n u d of muluf.colMp wtia In E"

120 CHEMICAL ENGINEERING/SEmFMBER 1991

. .

thetta&&d :&atrdospherie: con& whe:e in-Letween.-bhi?iniaWDstes are& wastesin~ the pmcess,:;th*:firpt mduer, 1 tions: Variable wastes might' b e repre- .Umant 3tkthe..fudatnbbM: procesk'. , ~ ~ a e f f o t k ' e m p h ~ ~ s t h t simple, obvi-. 'sented by working 1osses.of.VOC from wafipration. whereas taxtsiesic;onse ous,, and .most. :cosktffective .altem&

. the tank, dependentupon the volumeof are:pssociatd With the auxiliary. as-. 'I tives; and are material .passing through:the tank. pects of the operation,The above list of exhinsic waste Other examples of fiied wastes in a ten streams is arranged with the most- . These Phase I efforts' include good-

,

, ,i . . CHEMICAL ENGINEERINGISEPTEMBER 1991 121

. . . .

. . . . . .

. . 1 . . .

of materiais without treatment, and the other practices noted above. Emphasis is on the operation rather

anal reductions are desired. more-ex-

(Phase 11). These are with equipment modi-

r recycle. This phase immediate ROI, and

. m te the procesr,

rinl orcataiyru, or

Jusfdying fundamental changes to the process as part of the pollution-preven- tion program per se is particularly diffi- cult - a Rand Corp. study [s] shows that the first construction-cost esti- mate of process plants involving new technology is usually less than half of the final cost, with many projects expe- riencing even worse performance.

A case in point A striking example of combating intrin- sic wastes is found in the manufacture of ethylene 0ide;It.s production beg& in 1914, using dehydrochlorination of ethylene chlorohydrin to form theox- ide: While the jield of this chlorohydrin process reached over 8074 it generated unwanted chlorine-containing byprod- ucts as well as large amounts of waste calcium chloride. Many improvements to this process were made, but none meaningfully reduced those wastes. . .

ver catalyzes the FIGURE 1. formation of eth- A sustained poliu- y]ene oxide from tion-prevention ef- ethylene and oxy- fort at an existing plant takes place gen? without pro- in three succes- duction of calcium sive phases that chloride or chlori- generate succes- nated materials.

. At first, the yield slvely less return on Investment lR0l l of this direct- I ~..-.,

synthesis proeess was only 50% and it did produce numer- ous undesirable by-products of its own. But improvements 'in'catalyst technol- ogy, and use of promoters of ethylene oxide generation and inhibitors of un- wanted by-produets ' have raised the ethylene oxide yield to above 8G%. To- day, virtually all ethylene oxide is pro. duced viathis directaidation route: . . ' -Selectivity of the .catalyst towards ethylene -'oxide :formation decreases with enylene consumption, so the oper' .. ation is generally designed to produce a stream containing only 1 to 2% of that product. The' ethylene, oxide must be recovered from this gas, and theresidu-' a1 hydrocarbon recycled to the process. A portion of the recycle stream is bled off to prevent buildup of carbon &ox:

122 CHEMICAL WGINEERING/SEPTEMBER 1991

ide, unwanted byproducts, and impuri- ties that enter t h e process with the reactants. Treatment or recovery of portions of thii fixed waste stream var- ies from case to case.

Several years ago, the US. Environ- mental Protection Agency @PA) esti- mated [IZl that this stream represented less that 10% off& a u w a s e s from an etllylene oxide plant The rest were e*nsic streams associated with equipment leaks, a problem that threatens all CPI plants. Equipment-screening studies for the ethylene oxide industry demon- strated that the industry's fugitive emissions were less than one-tenth of EPA'S expectations. That industry has been designated as representing MACT (Maximum Achievable Control Technology) for fugitive emissions un- der the new U.S. Clean Air Sct .

One of the main uses of ethylene oxide is making ethylene glycol, via hydrolysis in the presence of large ex- cess (usually20-fold) amounts of water. This operation typifies the need to ac- commodate byproducts in an environ- mentally satisfactory way.

About 90% of the hydrolyzed oxide is converted to ethylene glycol. The re- mainder reacts to form higher homo- logues, &- and triethylene glycol, that can be recovered through distillation, as well as some additional impurities, such as aldehydes and tetraethylene glycol, that must be removed to pre- vent their accumulation. To be success- ful, an ethylene glycol'operation must be able to market the di- and tri- by- products. Among their uses are drymg of natural gas and as an intermediate for making resins and plasticizers. .. . '

The ethylene oxide and glycol exam- ples^illrisfzate thehportance of look-

a l t a " i e ~ ~ . b . ~ p r o c e 8 e tJu4

byproduct-depends at least in part upon its priee and the-price of the products for which it may be a close substitute. As for recycling.the byproduct; the typical CPIplant is not likely to provide an incentive, except perhaps when the

d m , d ~ ~ S ~ + b ~ t h ~ b y ~ r O d U c t ~ Whether br. nofi t pays 'to mar

t

material can serve as fuel (however, see later -discussion of integrated facilities).

There may well be a complication, especially as regards the marketing option. Many byproducts are classified as hazardous wastes, and constraints are placed on their storage, transport, and use.

In summary, while significant reduc- tions in pollution and waste generation can in some cases be achieved via evolu- tionary changes in process technology, a revolutionary process change (such as switching from the chlorohydrin to the direct oxidation means of producing ethylene oxide) may ultimately be need- ed to achieve desired reductions. The introduction of radically new process technology might initially cause waste generation to rise, but as refinements in the technology (such as better cata- lysts, inhibiters or promoters) are eval- uated and implemented, long-term re- ductions can be achieved p g u r e 2).

3. Plant configuration In the context of pollution prevention, two aspects of plant configuration and layout are especially important. The first is the desirabilitv of process integration.

PART f

ility is likely to be large and complex.' Thus, pollution preven- tion can replace or supplement the economies of scale as a motive for plan- ning large, integrated facilities.

Wel1:designed large petroleum refin- eries tend to reflect this philosophy. An especially striking example is BP Oil 120:s Alliance Refinery at Belle Chasse, La. The completely integrated single- train facility, built in 1971, is designed to minimize waste generation and con- serve energy by whenever possible feeding hot charge directly from one unit to the other. Even the amount of intermediate tankage included in the design is thus minimaI[lfl.

Sometimes a raw-material supplier and the customer can link up to enable a desirable bit of integration. A good example .involves acrolein, which Mon- santo employs as a raw material and buys from Union Carbide. Acrolein is so flammable, reactive and toxic that it is no longer transported between plants. Instead; through special agree- ment between the two firms, both the raw material (acrolein) and the final Monsanto product are produced a t .a single Union Carbide facility. By opti- mizing the continuous processing of acrolein into the final Monsanto prod-

I

CHEMICAL ENGINEERINGISEPTEMBER 1991 123 I

... ..

.. . . ~ . '1 COVER STORY

ucf engineers have eliminated the haz- ards linked with transporting that alde hyde and minimized its storage.'

emisGns hGi equipment leaks can ac- count for more than onequarter of total releases to the environment - an effec- tive program to address them requires not only selecting equipment with low- leak potential but also placing the equip ment so that it is easy to reach.

In the same vein, units that are regu- arly shut down for process changes or \

rged and cleaned, e are transferred to

downstream vessel or unit. ,

4. Information and control Obviously, a process unit needs an ad quate information-and-contol systei to optimize yield and minimize undesi able- byproduction formation. -!&

THE PROCESSING CHALLENGES Pollution-prevention experience to date suggests that wastes are especially likely to be generated when any of these conditions are present:

The products are complex The process is complex Process temperatures or pressures deviate significantly from ambient. This

' ' is especially likely to trigger waste generation at auxiliary aspects of the

The products must be highly pure in comparison to the purities of the -reactants . ' ' . '

Batch operations rather than continuous are used. This is because of having to clean system between batches, and losses during startup and shutdown Many solvents and other non-reactant chemicals are required

operation, such as storage and transfer

The payout can be dramatic. For ex- ample, a recent investment in comput- ereontrolled process changes reduced overall air emissions a t an ethyl cellu- lose resin plant of Dow Chemical U.S.A. by 28% [la.

5. H u & ~ resources I t has been estimated that about 15% of the time of an average plant-operating employee in the CPI is devoted to ad- dressing immediate environmental con- cerns. While one might expect a good pollution-prevention program to lower this figure, +e long-te ev- ertheless needs the iw x

' '

, .

, ,

~~~.~~~~~~~~ mh a , ,

portant that the employees be: Dedicated. They must rank pollution-

prevention issues on a par with other pressing work-related issues

Trained. They must be able to recog- nize pollution, spot pollution- preven- tion opportunities when available, and work with others to implement new projects D Rewarded. Management must recog- nize them for improvements that re h e pollution, yet not penalize them for ideas .that do not meet expectations.

, ,

a

Employees at all levels of the organi- :ation must become involved. Many of he improvements in petroleum-refin- ng technology have come from hands- )n refinery operators. rather. than ieople : with scientific or. engineering !ducation..

i. Research and development Cffective research and development is he key ta an ongoing pollution-preven- ion program. There are four espeiially mportant aspects. Firsf~R&D must fmd new processes

md modifications to existing processes o reduce w&te generation. In ethylene' liide and ethylene glycol, for.ins&ce, w e n t , research is a t t a c b g :waste ;eneration by improving the selectiv- 7, capacity, lifespan, and .activity of he catalysts, and by upping in other fays the selective production of m o m thylene glycol from ethylene oxide

without the formation o i higher ethyl. ene glycol homologues.

Furthermore, R&D must seek new separation technology to purify and segregate waste streams in the pro cesses. It must come up with new ana lytical techniques not only to to detect impurities and unwanted residual ma. terials but also to pinpoint their sources. And all the while, it must pro 1 vlde ongoing support to existing opera- tions for incremental improvements in pollution prevention.

7. Supplier-customer rapport Pollution'prevention is fostered by a close relationship between supplier and the customer.. This pertains to suppli- ers of equipment and raw materials alike.

For instance, CPI engineers should interact closely with their counterparts at valve, pump and gasket suppliers to reduce fugitive emissions. In one im- portant Union Carbide pollution-pre vention activity, the strategy finally adopted.' to -e!im&ate'; a '.problematic chemical from a waste stream was fiRt proposed by the supplier of that chemi- cal. -And a supplier's .employing the "juit in time" philosophy of producing a product exactly when needed by the customer can reduce wastes generated from storage.

Companies sometimes seek closer eo- operation'with a supplier in'order to

obtain purer raw materials from thai supplier. It is well to realize that thi: will benefit society only if it brings about a net reduction in the combined customer-supplier waste generation as sociated with the final product made from that material.

8. Organization Pollution prevention must receive sup port and commitment from all levels within the firm. This includes, and must start with, top management.

Furthermore, the company must be organized and run so as to allow staff interaction and teamwork. Many firms are not nearly so good in that regard as they believe. An individual engineer or operator can reduce or eliminate a par- ticular extrinsic waste stream, but in- trinsic wastes often can only be sd- dressed by the coordinated efforts of representatives from operations, engi- neering, and R&D, and may require participants from marketing and pur: chasing, and suppliers and customers. ;-:A notably skong , role in'.-effective pollution prevention is played by the firm's accounting department. For one thing, accurate and appropriate "score- keeping" of waste reduetions is unpor- t int for the W s ,interactions 'with regulatory agencies. Whafs more, the companykaccounting system must be dapted.to fully.recognize the internal benefits 'of' a pollution-prevention program.

While substantial initial reductions :n pollution can be achieved with rela-

PART 1 -

tively little cost during the Phase I discussed earlier, a more-rigorous program can be quite expensive, es- pecially for existing oper- ating facilities. To be viable, each individual pol- lution-prevention project must be able to compete for needed resources with

other needed projects. In the same vein,'almost every pro-

ject also involves a series of technical compromises that determine cost, per- formance, and l i e . These compromises must mirror the values that the compa- ny, the customer and society want, but they must be judged on'economic grounds.

Conventional accounting practices ' require that a new program provide some payback or return on investment (ROI - sometimes whimsically called Rejection of Innovation). And admitted- ly, many firms' successful pollution- prevention programs do indeed empha- size payback. But a program directed a t intrinsic wastes that require signifi- cant R&D or massive capital expendi- tures will probably not achieve any im- mediate payback, and might only be justified by considering additional fac- tors such as reduction in long-term li- ability, such intangible benefits as a positive community image, and hidden costs associated with existing waste management practices.

EPA has developed an approach that addresses such benefits. It is summa- rized in.Figure 3 and presented in Ref- erence [19].

Table 1 summarizes the eight aspects discussed up tc m w . It i:lcludes practi- cbi comments with respect to each of them, related to implementing'a pre vention program.

New-technology developmeqi om the time a new process is con- ceived until a plant employing :t begins production, there' are many dpportuni: ties 6 .consider 'pollution prevention.' These include the periods .when:. the original laboratory and pilotscale stud- ies are conducted 'and the ,process is conceptually defined; the process is de ' veloped; the final technology is defied; fie process unit is designed and engi- neering spifications is prepared; and ., ...

CHEMICAL ENGlNEERlNGlSEKEMEER 1991 125

. .. - ,- COVER STORY

the unit is constructed and started up. The emphasis a t each stage should

vary. In the early periods, the polluhon- prevention focus should be on the actu- al product and the process. Once the process is defined and the facility is being scoped and designed, the focus should shift to the equpment needed.

With the completion of the engmeer- ing design and the purchase of the equipment, the focus shifts to keeping pollution prevention in mind during equipment installation. Finally, the same must be done dunng startup (un-

Consider pollution-

prevention from the beginning

-

fortunately a fertile source of waste material) and subsequent operation.

The importance of thinking about pollution prevention from the early stages cannot be overemphasized. This is especially true for avoiding inizinsic wastes.

The link with safety Because environmental protection and worker safety are each goals that have become more important to society in recent years, it is common to link them somewhat in one's mind. In fact,

product design

FUNCTIONAL I ASPECTSOF AREA^) 1 CHARACTERISTICS IMPLEMENTATION

Product mix Product complexity Retormulotlons

Plant configuration

I Process design I Automotion

Process conditions Process complexity Maintenance plans Catalyst technology Equipment selection

Location [re customer) Integration Slze accepted New look at accepted DraCtices

Information and. control sysbmr

Human reaourws

Resiarch and d evd o p m o n t

..

%dpllets customoris mle.and relatlonshlp

Oganlmiion..

Product toxicity, hazard- ~~

Transportation modes Bans. phose-ouis. taxes Recyclabiiity, degrodoblilty.

disposal

Eledronlc data handling Wade tracking Computer integration Process monitoring

Training Showlng ston that Motivation poilullon prevention Rewards gets high priority

Management prodices

Developing products Developing altematlves

Evaluating calaWsh. Use 01 byproduds

Pllat-plant testing

Subcontracting. tali manutactwe Ute-cycle woste. management Partnerlng . lntonnatlon exchange Jolnt ventures

Economlc analysis (Roll Strategic management StratGic ObjeCtiVeve. Topmanagement suppon

Corporate environmentoi

and processes 'Integratlon

separatlons

-vlslon ..... Additional economic factors

Focused teamwork-

1 Pocroging oesign

Choice 01 raw moleriols Generation. use 01 bmrooucts Storage of chemicals onsite Waste treatment, disposol Minimization 01 leab

Smaller size. more integration Recontiguratlon of operations Reuse 01 byproducts

RELEVANT SOCIETAL TRENDS

Toxic-ure reduction Greening Recycling Dlsposoi.copocity limit

Community awareness "Good Neighbor" Emisstom reporting

Permit restriction Emlssion iimitr Risk assessments

Public eiectronic access lo waste dolo

4wards to proactbe companies

Jnberslr/-lndustry consortla kodemic training in pollution prevention'

:uiI ittecycle assessments

iacietal costs Ilgh-level government support >dustrycommunli) supporl groups

I ABLE 1. The major functlonal areas to be covered by a pollution-preventfon etfori are respectively ldentftled by Varlous ~ncterlstlcs. entail numerous aspects of implementatlon, and have wide-ranging tie-ins with the economy (or society) at large

j26 CHEMICAL ENGINEERING/SEmEMBER 1991

PART 1 . _ --

however, their dictates can be in op position, especially when the specific environmental goal becomes pollution prevention.

From a worker-safety standpoint, CPI plants nowadays are designed and operated to minimize the chance of the worst possible outcome - for example, explosions, fires, and operator expe sure to toxic material. The pollution- prevention perspective adds a need to maximize the chance of the best possi- ble outcome, namely, zero emissions.

In many cases, such as reducing stor- age, monitoring for fugitive leaks, and using more integrated facilities, those two operating goals are compatible. But in other respects, such as lengthened operating cycles to reduce wastes gen- erated durine maintenance. llrrrmlllclts

" d t P T h e optimal polluion-preven. don prognm requires numuing and balancing tension bemeen these poren. tially contradictory requirements.

What g o v e r n m e n t can do Pollution prevention is achieved through the vohntary activities of com- panies. To make such activities more amactive to csmpanies, governments should address several regulatory, pro- cedural and publicawareness impedi- ments. The following wish-list of s u g gested governmental actions [ZI] is tai:ored somewhat to the US. scene. Nevertheless, most if not all of the proposals could be beneficially adopted in other nations, or in some cases even internationally:

Esrablish a uniform national data-

The authors

lutanol and on olllttion pksention. Holder of P ' . B.S. in cheniieafengineemg from the U. of M i n

nesota nod a mater's de ee in that field f m m the U. of Wahington, h e y a s Ivrittm more than 30 a em nod IS coeditor of "Ro spheric Ozone am! t\e dnvirknent,'* Air and %uta Manage- ment Arm.. Pihrburgh, 1991.

1

base to measure pollution-prevention progress and environmental-quality trends, employing standardized defini- tions built upon the best of the existing databases

Create incentives' for pollution pre- vention and eliminate statutory and regulatory barriers. For example: Streamline the permitting process for environmentally sound recyclipg of waste ,streams; encourage creation of markets for recycled materials; and r e frain from rigid regulatory deadlines and associated severe penalties when companies try innovative pollution-pre- vention approaches. Otherwise, compa- nies will tend to stick to the high-cost ''tried and true" options

Adopt a national pollution-prevention policy that encourages source reduc- tion and environmentally sound recy- cling as a first option, but that also recognizes safe'treatment, storage and disposal practices as important compo- nents of an overall environmental pro- tection strategy

Develop a policy that emphasizes net environmental benefits and gives regu- lators the flexibility to balance the needs of protecting air, water and land resources

Coordinate pollution-prevention strategies among EPA's program of- fices, EPA's regional offices, and state and local governments D Facilitate the transfer of technology, via a national pollution-prevention information clearinghouse and state technical-assistance programs

Increase industry and consumer pol- lution-prevention awareness (and modi- fy their behavior) through education md training initiatives . . - .

Edited by Nicholas P. Chopey

References 1. Haas. E.A.. Breakthrough Manufactwing.

H o m d Bwinm Review, Marrh-Aprill967. pp. 7581.

2 Comory, R. E., and Schmitt R. W.. Science and Product, Science, Vol. 240, p. 1137, 1203. May 17, 1988. - well . A. H.. The ?hid Dimension of Waste

Minimization, Chemical Engineering Pro. mesa. June 1969. D. 5. ~. ..

4. MeGuLF. M. L. and Jones, K.. Maximizing the Potential of Pmeesa En eeling Databases. Chemical Engineering %gws, November 1969, pp. 7883.

5. Hunter, J. S.. and Benfomdo, D. M.. Life Cycle Approach Lo Effective Waste Minimbation Pn- per -'81-15.12. Pmcecdin 8 qfthc 8Gth A&- el Meetin of the Air Pofulion Control Fed-

6. 'Amold. J. H.. Asseaskg Capital Risk You Can't Be Tm Consenrahve, Hnrvord B w i n c s ~

' R h n u . September 1986. pp. 113-121. loitation of

Science by American Indusoy, i n x a r k , K. B. Hayes. R. €I. and Lorenr, C., 'The Uneasy A d anee, M a y ' p the Pmduehvl Technology Dilemma, arvard Bus& ' g h m l Press, Boston, 1985.

6. American Pemleum Institute. "Fill'er Up." r e printed in Doings in General. April 1926, p. 16.

9. Nelson. W. L.. "Petroleum Refinely Engineer- mg." 4th ed., MeGraw-Hill. New York.

emtion, 21- z 6 . m .

7. Rasenberg, N.. The Commercial E

10.01sehewski. K. H. and Spibmuller, K., "Heat- ing Oil." Volume A-12, p. 61'7. "Llllmann'r Ency. elopedia of Industrial Chemism." Weinheim, Basel, 1989.

11. Reonda: S. and Mayer D.. "Ethylene Oude." Volume A-16. p. ;l:.l%, 'Lllmann s Eneyelope dia of l n d u r n a l Chemwq,' \Ve:nheim. B u a . .

A1969. D. W., S o m e of Ethvlene Oxide EPA450/585014. U.S. Environ-

mental Rateetian Agency, Office of Air Qualii Planning and Solndardr, Research Wangle - k k , N.C., April 1985.

_ _ I

13 erglund R . L Romano R.R. and Randall 2.L. Fuh t ive Emissions'Fmm the Ethylen; f

Oxide Pmduetion 1ndust-y. hvirammfnl Pmgnsr. February 1990. pp. 1C-17.

14 RebsdrL S and Mayer. D "Ethylene Clyml." Volume A-10. p 101.!15. "llllmnnn 3 Eneyc.ope dm of Indusmal Chrmurry." Welohem. Barsl, 19fi9

6 h t h e o a t . H. G., Minimize Refinery Waste, --ffydwcarbon Pmcesng. Augus t 1990. pp.

52.54. I a r lund. R. L. Neely. C. C., and Riffle. J. +Qua%q P m p m : SptemPhC Reduehon o i

Lenb From Valves and Other Equipment, . Volva Magazine, Wmter 1991. pp. 2629.

p : E n v i m i m e n t a l b k t i o n Afen "Pollu. . k B & n d . R L &d S n y d n G. E., W a t e Mini. .:mabon The Smner the Bettu, Chnntcch,

. tion Prevention Benefib Mnnual ,la. December 1990, PP. 70-746. .

2U.S. Environmental Pr&tion A ency, Pmeeedin I of the National Air Polfutant Control l h q u e r Advirory Committee,

. . April 1991. . . .. . . ,

I CHEMICAL ENGINEERING/SEPIEMBER 1991 127