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1 Chemical Process Hazard Review JOHN M. HOFFMANN
Downloaded by 80.241.75.94 on August 14, 2015 | http://pubs.acs.org Publication Date: March 14, 1985 | doi: 10.1021/bk-1985-0274.ch001
Parke-Davis Division, Warner-Lambert Company, Rochester, MI 48063
The phrase Chemical Process Hazard Review has widely varying meanings. To the professional safety engineer, it connotes a broadly based review of a chemical process which when conducted properly would provide assurances that a process can be conducted "safely"; safe for the scientists in the laboratory, the technician in the pilot plant and the chemical operators in the manufacturing plant. The developing chemist may view a chemical process hazard review as just another hurdle to jump enroute to getting his/her process into the pilot plant or manufacturing plant. Chemical engineers destined to design both the process and equipment may depend on such a review to provide the details necessary to design the process "safely." Environmental engineers and control specialists consider a review process as a means for estimating risk to environmental exposure (air, water and ground) and a source of data to develop compliance information. Management needs the assurance from both line managers and staff functions that the process can be conducted and the hazards associated with that process in its entirety are identified to the extent that appropriate risk/benefit decisions can be made. An appropriate Chemical Process Hazard Review can and should meet all of these needs.
L i f e i n t h e c h e m i c a l p r o c e s s development w o r l d i s no l o n g e r one shrouded i n t h e m y s t e r i e s t h a t s y n t h e t i c o r g a n i c c h e m i s t r y can p r e s e n t . The b a s i c r e s e a r c h e r does n o t have t h e l u x u r y o f l i v i n g i n 0097-6156/85/0274-O001$06.00/0 © 1985 American Chemical Society
In Chemical Process Hazard Review; Hoffmann, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
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an i s o l a t e d l a b o r a t o r y and day a f t e r day p r o d u c i n g new c h e m i c a l e n t i t i e s through ever i n c r e a s i n g complex c h e m i s t r y w i t h o u t r e g a r d to t h e u l t i m a t e p r o c e s s i n the p i l o t p l a n t . The developmental c h e m i s e s concern i s not j u s t d e f i n i n g a w o r k a b l e , c o s t - e f f e c t i v e p r o c e s s but one which can be done " s a f e l y and e c o n o m i c a l l y . The c h e m i c a l e n g i n e e r d e s i g n i n g a p l a n t s c a l e p r o c e s s a l s o has added a number o f new concerns which must be c o n s i d e r e d b e f o r e c o m m i t t i n g to a p l a n t i n s t a l l a t i o n . C o n s i d e r f o r a moment j u s t t h e changes i n v o c a b u l a r y d u r i n g the p a s t twenty y e a r s among t h e s e p r o f e s s i o n s . Chemists and c h e m i c a l e n g i n e e r s l o n g known f o r t h e i r seemingly c a p r i c i o u s use of acronyms and p e c u l i a r j a r g o n a r e f a c e d w i t h i n c o r p o r a t i n g and u n d e r s t a n d i n g those i n v e n t e d and used by o t h e r s . OSHA, PEL, NIOSH, RTECS, HMTA, FWPCA, CPSA, IARC, FEPCA and SF a r e j u s t a few. With t h i s seemingly overwhelming burden o f r e g u l a t o r y r e q u i r e m e n t s , l i f e and b u s i n e s s must go on and they a r e . A s m a l l p a r t o f c o n t i n u i n g l i f e and b u s i n e s s has been and i s i n the Chemical P r o c e s s Hazard Review. N o t w i t h s t a n d i n g the c o m p l e x i t i e s c o n s i d e r e d above, c h e m i c a l p r o c e s s e s must be developed i n a way which p e o p l e , the environment and p r o p e r t y a r e p r o t e c t e d . The c h e m i c a l r e a c t i o n p r o c e s s i t s e l f p r e s e n t s i t s own p e c u l i a r e v a l u a t i o n needs which impact upon o c c u p a t i o n a l s a f e t y and h e a l t h , e n v i r o n m e n t a l p r o t e c t i o n and p r o p e r ty p r e s e r v a t i o n and c o n s e r v a t i o n . I n the p r o g r e s s i o n o f a process from the r e s e a r c h l a b o r a t o r y to the development l a b o r a t o r y to the p i l o t p l a n t and e v e n t u a l l y to m a n u f a c t u r i n g , the o b j e c t i v e s f o r the p r o c e s s r e v i e w must be: 1. The a b i l i t y t o c a r r y out t h e d e s i r e d p r o c e s s p r o d u c i n g the desired products, p r o f i t a b l y ; 2. Development o f d a t a w h i c h can c h a r a c t e r i z e the r e a c t i o n , i n c l u d i n g s i d e o r minor p r o d u c t s , and the c o n d i t i o n s under which they may be produced. 3. Development o f r e a c t i o n c o n d i t i o n s ( t e m p e r a t u r e s , p r e s s u r e , c o n c e n t r a t i o n s and equipment) a t which the p r o c e s s can be conducted " s a f e l y . " 4. I d e n t i f i c a t i o n o f c o n d i t i o n s and events ( o t h e r than normal) which can l e a d to hazardous c o n d i t i o n s o r p r o d u c t s .
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Most major c h e m i c a l and p h a r m a c e u t i c a l companies today have developed s y s t e m a t i c methods o f e v a l u a t i n g new (and i n many c a s e s , old) p r o c e s s e s and m a t e r i a l s f o r the hazards a t t e n d a n t t o t h e i r manufacture. The degree of urgency i n e s t a b l i s h i n g a c h e m i c a l p r o cess h a z a r d a n a l y s i s f u n c t i o n has o f t e n been d i c t a t e d by some untoward event ( u s u a l l y w i t h i n the company). I t i s to the p r e d i c t i o n and c o n t r o l o r e l i m i n a t i o n o f unplanned r e a c t i o n events to which the c h e m i c a l process h a z a r d review must address i t s e l f . B r o a d l y , the r e v i e w p r o c e s s can be s e g r e g a t e d i n t o : an unders t a n d i n g o f the c h e m i s t r y , d e s i r e d and p o s s i b l e ; a thorough l i t e r a t u r e r e v i e w o f r e l a t e d c h e m i c a l r e a c t i o n s and p r o c e s s e s ; t h e r o r e t i c a l c a l c u l a t i o n s ; and d e s i g n and conduct o f experiments to c o n f i r m hypotheses and/or g a t h e r a d d i t i o n a l d a t a .
In Chemical Process Hazard Review; Hoffmann, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
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Process
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Chemistry
In u n d e r s t a n d i n g t h e d e s i r e d and p o s s i b l e c h e m i s t r y t h e p r o c e s s a t each s t e p s h o u l d be c a t e g o r i z e d as t o type o f r e a c t i o n and a b a l a n ced c h e m i c a l e q u a t i o n developed. The use o f a b r o a d c a t e g o r i z a t i o n such as g i v e n i n T a b l e I i s f r e q u e n t l y used as a s t a r t i n g p o i n t . A l l p r o b a b l e s i d e p r o d u c t s s h o u l d be i d e n t i f i e d and t h e i r p o t e n t i a l r o l e ( s ) p o s t u l a t e d . Rate d e t e r m i n i n g s t e p s i n m u l t i - s t e p o r s e q u e n t i a l p r o c e s s e s s h o u l d be so l a b e l e d and t h e i r import t o t h e process i d e n t i f i e d .
Downloaded by 80.241.75.94 on August 14, 2015 | http://pubs.acs.org Publication Date: March 14, 1985 | doi: 10.1021/bk-1985-0274.ch001
Table I .
Chemical R e a c t i o n Energy C a t e g o r i z a t i o n
Process Oxidation
Sulfonations Hydrolysis Polymerization
Energy H i g h l y Exothermic E q u i l i b r i u m Favored Exothermic Potential oxidation Low H i g h l y Exothermic chain reaction f o r Chlorine & Fluorine Moderately exothermic M i l d l y exothermic Can be h i g h l y e x o t h e r m i c
Condensations
Moderately
Hydrogénation
M i l d t o moderately exothermic easily controlled M i l d l y exothermic side reactions g e n e r a l l y a problem Highly exothermic Moderately exothermic
Nitration Reductions Halogenations
Alkylation
Organo M e t a l i c s Amination
exothermic
Chemical Hazard Potential High High Low High
Low Low Moderate to h i g h Low t o moderate Moderate to low Low
High Low
I d e n t i f i c a t i o n and q u a n t i f i c a t i o n o f t h e d e s i r e d r e a c t i o n cond i t i o n s , p a r t i c u l a r l y temperature and c o n c e n t r a t i o n , a r e n e c e s s a r y to e v a l u a t e what may happen i f t h e s e c o n d i t i o n s a r e n o t met. T h i s i s p a r t i c u l a r l y t r u e where e q u i l i b r i u m c o n s i d e r a t i o n s a r e a s i g n i f i c a n t f a c t o r i n a r a t e d e t e r m i n i n g s t e p between o r among competing r e a c t i o n s . Where m u l t i p l e p r o d u c t s a r e p o s s i b l e , temperature v a r i a t i o n s w i l l o f t e n s i g n i f i c a n t l y a l t e r t h e r a t i o s o f these p r o d u c t s . I f one o f t h e s e i s u n s t a b l e o r more t o x i c , t h i s c o u l d l e a d t o more s t r i n g e n t temperature c o n t r o l requirements i n t h e p r o c e s s and e q u i p ment d e s i g n .
In Chemical Process Hazard Review; Hoffmann, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
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Downloaded by 80.241.75.94 on August 14, 2015 | http://pubs.acs.org Publication Date: March 14, 1985 | doi: 10.1021/bk-1985-0274.ch001
I d e n t i f y i n g the " t y p e " o f r e a c t i o n can be u s e f u l i n b r o a d l y c a t e g o r i z i n g the o v e r a l l p o t e n t i a l hazards as w e l l as a i d i n g i n the l i t e r a t u r e s e a r c h . Many l i t e r a t u r e sources r e f e r t o r e a c t i o n s n o t o n l y by t h e i r h i s t o r i c a l name but a l s o by t h e i r type. I f a r e a c t i o n s t e p i n a p r o c e s s can be i d e n t i f i e d i n t h i s manner, i t may a i d i n the l i t e r a t u r e s e a r c h and i n k e y i n g v a r i o u s r e v i e w e r s memories. Types o f r e a c t i o n s such as F r i d e l - C r a f t s , G r i g n a r d , Meerwin-Ponndorf, C a n n i z z a r o , Clemenson. W o l f f - K i s h n e r , Hofmann D e g r e d a t i o n , Beckman Rearrangement, Simmons-Smith, P i e l s - A l d e r , W u r t z - F i t i g , e t c . may n o t be household names to everyone, b u t they a r e to many o r g a n i c c h e m i s t s . More i m p o r t a n t l y , l i t e r a t u r e s o u r c e s can be searched f o r these c l a s s i f i c a t i o n s to g i v e an o v e r a l l p e r s p e c t i v e to a r e a c t i o n under study. Literature Not enough can be s a i d about l i t e r a t u r e reviews when you c o n s i d e r how many chemists t h e r e a r e i n the w o r l d today (128,000 c u r r e n t members i n the American Chemical S o c i e t y a l o n e ) and when you con s i d e r how many t h e r e have been from the days o f P r i e s t l y , the number i s awesome. Many o f these chemists as e x p e r i m e n t a l i s t s have t r i e d m i x i n g a l i t t l e of e v e r y t h i n g w i t h a n y t h i n g to see what would happen. O f t e n something d r a m a t i c d i d happen. Much o f t h i s i n f o r m a t i o n has been r e c o r d e d i n the l i t e r a t u r e a l b e i t a b i t h a r d to f i n d at t i m e s . F r e q u e n t l y , c h e m i c a l a c c i d e n t s i n the l a b o r a t o r y a r e r e p o r t e d i n C&E News i n the l e t t e r s t o the e d i t o r . Invariably, a f t e r p u b l i s h i n g the untoward event i n t h i s manner o t h e r readers w i l l respond w i t h r e p o r t s of s i m i l a r occurences t h a t they were i n v o l v e d i n o r knew about. And o t h e r s w i l l r e p o r t a l i k e event r e corded i n the l i t e r a t u r e i n y e a r s p a s t . Table I I l i s t s a few s t a r t i n g p o i n t s f o r l i t e r a t u r e r e v i e w s . As i s o f t e n the case i n l i t e r a t u r e s e a r c h e s , one key a r t i c l e can o f t e n p r o v i d e the r o u t e back to p r e v i o u s authors and r e v i e w e r s who have worked i n t h a t p a r t i c u l a r area of chemistry. T a b l e I I . L i t e r a t u r e Review ο ο ο ο ο ο ο
L. B r e t h e r i c k - Hand Book o f R e a c t i v e Chemical NFPA 491 M & 49 F a c t o r y M u t u a l Data Sheets 7-19, 7-23 Kirk-Othmer CMA (MCA) A c c i d e n t Case H i s t o r i e s Volumes 1-4 Open L i t e r a t u r e V i a Chemical A b s t r a c t s Data Bases Such As : Med L a r s , Toχ L i n e T o x i c o l o g y Data Bank and D D C.
Hazards
Theoretical Calculations T h e o r e t i c a l c a l c u l a t i o n s can be made r e g a r d i n g the energy which i s a v a i l a b l e from a r e a c t i o n . The use o f c h e m i c a l thermodynamic t a b l e s , t a b l e s o f h e a t s o f f o r m a t i o n and known h e a t s o f r e a c t i o n
In Chemical Process Hazard Review; Hoffmann, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
Downloaded by 80.241.75.94 on August 14, 2015 | http://pubs.acs.org Publication Date: March 14, 1985 | doi: 10.1021/bk-1985-0274.ch001
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Chemical Process Hazard Review
can l e a d t o e s t i m a t i o n s o f the energy a v a i l a b l e . C o u p l i n g t h i s w i t h r e a c t i o n c o n d i t i o n s (temperature p a r t i c u l a r l y ) and gross r a t e s observed on b e n c h - s c a l e experiments can produce m e a n i n g f u l p a r a meters t r a n s l a t a b l e to s c a l e - u p . C a l c u l a t i o n s o f oxygen b a l a n c e e i t h e r f o r the t o t a l r e a c t i o n mixture o r f o r i n d i v i d u a l products i s a simple yet very e f f e c t i v e f i r s t - o r d e r e v a l u a t i o n o f a process o r m a t e r i a l , p a r t i c u l a r l y n i t r a t i o n s and n i t r o - c o n t a i n i n g compounds. Most a u t h o r s recommend d e t e r m i n i n g the r a t i o o f oxygen a v a i l a b l e w i t h i n the system t o t h e o r e t i c a l oxygen requirements n e c e s s a r y t o o x i d i z e a l l carbon t o carbon d i o x i d e , a l l hydrogen t o w a t e r , and n i t r o g e n reduced ( o r i n some c a s e s , o x i d i z e d ) t o e l e m e n t a l n i t r o g e n . I f o t h e r o x i d i z a b l e s p e c i e s a r e p r e s e n t , such as s u l f u r o r a l k a l i / a l k a l i n e e a r t h m e t a l s , these would a l s o be presumed t o be o x i d i z e d t o t h e i r o x i d e s i n the most s t a b l e o x i d a t i o n s t a t e . The CHETAH Program from ASTM Committee E-27 i s a l s o q u i t e usef u l f o r t h e o r e t i c a l c a l c u l a t i o n s o f enthalpy (decomposition, o x i d a t i o n o r c o m b u s t i o n ) , oxygen b a l a n c e , and p o t e n t i a l energy r e l e a s e . Recent m o d i f i c a t i o n s o f the program and u p d a t i n g o f the d a t a base make i t even more u s e f u l . Testing E v a l u a t i o n o f a m a t e r i a l o r p r o c e s s b y a n a l y t i c a l t e s t s and e x p e r i ments i s , o f c o u r s e , a must when h i s t o r y ( l i t e r a t u r e ) , t h e o r y and paper c h e m i s t r y a r e i n s u f f i c i e n t t o c h a r a c t e r i z e the p r o c e s s o r answer the s i g n i f i c a n t "what i f s . " T a b l e I I I l i s t s some o f the more common u s e f u l methods. Table I I I . DTA DSC TGA ARC BSC SEDEX Others
T e s t i n g Methods
D i f f e r e n t i a l Thermal A n a l y s i s D i f f e r e n t i a l Scanning C a l o r i m e t r y Thermo G r a v i m e t r i c A n a l y s i s A c c e l e r a t i n g Rate C a l o r i m e t r y Bench S c a l e , Heat Flow C a l o r i m e t r y S e n s i t i v e D e t e c t o r o f Exothermic P r o c e s s e s Oven T e s t s , Dewar T e s t s , Hot P l a t e T e s t s , e t c .
The u l t i m a t e purpose o f these types o f t e s t s i s t o e v a l u a t e two s i m i l a r ( i n r e s u l t s ) but d i f f e r e n t o c c u r r e n c e s . These a r e runaway c h e m i c a l r e a c t i o n s and e x o t h e r m i c c h e m i c a l d e c o m p o s i t i o n s . The f i r s t may a c t u a l l y j u s t be a d e s i r e d r e a c t i o n out o f c o n t r o l w h i l e the second i s an u n d e s i r e d r e a c t i o n out o f c o n t r o l . Among the purposes which a n a l y t i c a l t e s t s s e r v e a r e the d e t e r m i n a t i o n o f the " o n s e t " o f exothermic (endothermic) d e c o m p o s i t i o n . While f r e q u e n t l y a s p e c i f i c temperature i s c i t e d f o r such " o n s e t s , " one must remember t h a t t h i s temperature i s h i g h l y dependent on i n s t r u ment s e n s i t i v i t y , degree o f a d i a b a t i c i t y and time-temperature h i s t o r y . I t s h o u l d be s t a t e d t h a t t e s t s r e s u l t s a r e a c c u r a t e o n l y f o r the e x a c t c o n d i t i o n s under which they were r u n . P h y s i c a l f a c t o r s such as d e n s i t y and geometry can a l s o i n f l u e n c e t e s t d a t a . I n t h e o r y , r e a c t i o n r a t e s a r e n o t a s t e p f u n c t i o n but a r e c o n t i n u o u s . A r e a c t i o n r a t e f o r a p r o c e s s i s n o t zero below a g i v e n " o n s e t "
In Chemical Process Hazard Review; Hoffmann, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
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temperature, b u t i s merely a s m a l l e r number which i n s t r u m e n t a t i o n i s n o t s u f f i c i e n t l y s e n s i t i v e t o measure. In p r a c t i c e , however, e s t a b l i s h e d temperature o n s e t s f o r p r o c e s s r e a c t i o n s w i l l u s u a l l y a l l o w a s u f f i c i e n t margin o f s a f e t y , p r o v i d e d t h a t adequate c o o l i n g c a p a b i l i t y o r i n h e r e n t heat s i n k s a r e s u f f i c i e n t t o remove heat energy i n excess o f t h a t which can be generated. F o r h i g h l y exot h e r m i c r e a c t i o n s o r r e a c t i o n s w i t h low a c t i v a t i o n e n e r g i e s , i t may be n e c e s s a r y t o modify t h e p r o c e s s . Continuous o r semi-batch v e r s u s b a t c h i s one way i n w h i c h c o n t r o l may be m a i n t a i n e d w i t h i n engineering l i m i t s .
Downloaded by 80.241.75.94 on August 14, 2015 | http://pubs.acs.org Publication Date: March 14, 1985 | doi: 10.1021/bk-1985-0274.ch001
Summary The c h a l l e n g e t h a t f a c e s c h e m i c a l r e s e a r c h e r s , development chemists and e n g i n e e r s , m a n u f a c t u r i n g chemists and e n g i n e e r s and t h e s t a f f f u n c t i o n a l p r o f e s s i o n a l s a s s o c i a t e d w i t h chemical processes i s formidible. I t i s one t h a t r e q u i r e s more and b e t t e r i n f o r m a t i o n about c h e m i c a l p r o c e s s e s t o meet today's r e g u l a t o r y demands and b o t h p u b l i c and p r i v a t e e x p e c t a t i o n s f o r t h e c h e m i c a l and pharmaceutical industries. O r g a n i z e d and s y s t e m a t i c c h e m i c a l p r o c e s s h a z a r d r e v i e w s a r e n e c e s s a r y t o meet these demands. The attempt i n o r g a n i z i n g t h e Symposium on Chemical P r o c e s s Hazard Review a t t h e S p r i n g 1984 ACS n a t i o n a l meeting i n St. L o u i s , was t o p r e s e n t papers on t h e r e v i e w p r o c e d u r e , some o f t h e thermoc h e m i c a l e v a l u a t i o n t e c h n i q u e s and t h e a p p l i c a t i o n o f b o t h o f t h e s e to a c t u a l p r o c e s s e s . Some o f t h e papers p r e s e n t e d a t t h e symposium have been c o l l e c t e d and a r e p u b l i s h e d here to f u r t h e r exchange i n f o r m a t i o n r e l a t e d t o c o n d u c t i n g c h e m i c a l p r o c e s s e s "safely."
Literature Cited 1. Bodurtha, Frank T., Industrial Explosion Prevention and Protection, McGraw-Hill 1980 2. Fawcett, H.H. and W.S. Wood, Safety and Accident Prevention in Chemical Operations, Interscience Wiley 1982 3. Bretherick, L., Handbook of Reactive Chemical Hazards, Second Edition Butterworths and Co. 1979 4. Meyer, Eugene, Chemistry of Hazardous Materials, Prentice-Hall 1977 5. Seaton, W.H., Freedman, E . , Treweek, D.N., CHETAH - The ASTM Chemical Thermodynamic and Energy Release Evaluation Program, ASTM Philadelphia 6. Lothrup, W.C. and R. Hendrick, "The Relationship Between Performance and Constitution of Pure Organic Explosive Compounds," Chem Rev, vol 44 no. 3 pp 419-445, June 1949 7. Manufacturing Chemist's Association, Guide for Safety in the Chemical Laboratory, 2nd ed. Van Nostrand Reinhold, New York 1972 8. Skoog, D.A. and D.M. West, Principals of Instrumental Analysis 2nd ed., Saunders College, Philadelphia 1980 9. Cardillo, P., Combined Use of Instruments for Determining Chemi c a l Safety, Cromache Chimivca, 69, 1982 10. Fenlon, W.J., A Comparison of ARC and Other Thermal Stability Tests, AICHE Loss Prevention Symposium Aug. 1983 RECEIVED November 3, 1984 In Chemical Process Hazard Review; Hoffmann, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
