New Product Opportunities for Sulfur - ACS Publications - American

9 New Product Opportunities for Sulfur D. R. M U I R

Downloaded by CORNELL UNIV on August 17, 2016 | http://pubs.acs.org Publication Date: March 29, 1982 | doi: 10.1021/bk-1982-0183.ch009

Sulphur Development Institute of Canada (SUDIC), #1702, 505 3rd Street S.W., Calgary, Alberta, Canada T2P 3E6

I n v e s t i g a t i o n o f novel uses of sulphur is not j u s t a recent phenomenon - work was conducted s p o r a d i c a l l y d u r i n g the 19th century and w i t h greater i n t e n s i t y d u r i n g the 1920s. Butitwas not until the e a r l y 1970s that the economic situ a t i o n and the need f o r the unique p r o p e r t i e s of these m a t e r i a l s provided sufficient i n c e n t i v e for their development and c o m m e r c i a l i z a t i o n . This paper will review only those technologies which are commercial o r are approaching commercialization. Several sulphur a s p h a l t systems and sulphur concretes o f f e r significant product performance advantages, combined w i t h cost r e d u c t i o n potential, and in some cases, energy c o n s e r v a t i o n . These products are in commercial use today. One other technology which has commercial p o t e n t i a l produces s m a l l molded b l o c k s , such as tile and b r i c k , from sulphur. Although not a new use per s e , the agricultural importance o f sulphur must not be overlooked. I t s value as a m i c r o n u t r i e n t , although long recognised, is now t a k i n g on new significance in the light o f world food needs and inc r e a s i n g costs o f food p r o d u c t i o n . Approximately 87% o f a l l sulphur is used as a p r o c e s s i n g chemical in the form o f s u l p h u r i c a c i d and the bulk of the r e maining 13% is used in one combined form o r another f o r s p e c i a l i z e d chemical a p p l i c a t i o n s . Over the years though, researchers have been i n t r i g u e d by the prospects o f e x p l o i t i n g the unique chemical and p h y s i c a l p r o p e r t i e s of elemental sulphur in s p e c i a l product a p p l i c a t i o n s . I n f a c t , research was conducted sporadi c a l l y during the nineteenth century and w i t h greater i n t e n s i t y d u r i n g the 1920s. Three important f a c t o r s , however, worked 0097-6156/82/0183-0127505.00/ 0 ® 1982 American Chemical Society

Raymont; Sulfur: New Sources and Uses ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

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against s u c c e s s f u l widespread c o m m e r c i a l i z a t i o n - elemental s u l phur was not w i d e l y a v a i l a b l e ; it was expensive r e l a t i v e t o other m a t e r i a l s it could r e p l a c e ; and in general the t e c h n o l o g i c a l demands of the marketplace were low ( r e l a t i v e t o today) so that the value placed on q u a l i t y improvements t o be gained through sulphur technology was correspondingly low - too low in f a c t to o f f s e t the adverse economics. These c o n s t r a i n t s do not e x i s t today. Research e f f o r t s were renewed in the e a r l y 1970s and have been s u c c e s s f u l in b r i n g i n g a number o f new products t o the commercial or near-commercial stage. This research was spurred by an extended p e r i o d o f s e r i o u s over-supply o f sulphur on the world markets. Although t h i s s i t u a t i o n has undergone s u b s t a n t i a l c o r r e c t i o n and supply/demand is in much c l o s e r balance, the r e s u l t s of t h i s development work w i l l have s i g n i f i c a n t impact both on the product markets and the s u l phur producer. The products themselves f i l l i d e n t i f i a b l e t e c h n o l o g i c a l needs in the marketplace and thus provide d e f i n i t e advantages and b e n e f i t s t o the user. And as the products become more broadly used on a commercial b a s i s , the value o f sulphur w i l l be upgraded and the c y c l i c a l supply/demand swings w i l l be somewhat dampened, p r o v i d i n g greater market s t a b i l i t y f o r t h i s commodity. The whole f i e l d o f new product markets cannot be adequately d e a l t w i t h in a s i n g l e paper. This p r e s e n t a t i o n w i l l be confined to a b r i e f d i s c u s s i o n of three products which a r e now a t the commercial stage (two types o f sulphur a s p h a l t s , f o r both road paving and p a t c h i n g , and sulphur concretes) and one product concept, molded sulphur b l o c k s , which is b e l i e v e d to have good comm e r c i a l p o t e n t i a l . And, although the use o f elemental sulphur in a g r i c u l t u r e is n e i t h e r a new product nor a new use, t h i s a p p l i c a t i o n of sulphur w i l l be reviewed because o f i t s importance and the research a t t e n t i o n it is c u r r e n t l y r e c e i v i n g . These are not the only areas in which research has been conducted. Several other sulphur technologies have been developed to the commercial stage, i n c l u d i n g i n s u l a t i n g sulphur foams, sprayable p r o t e c t i v e coatings and sulphur paving mixes which use sand in p l a c e o f aggregate. Because the major market f o r these products is o u t s i d e North America, and in one case, the impact on the sulphur p i c t u r e w i l l be minor, these technologies w i l l not be covered in t h i s paper. As w e l l , s e v e r a l other technologies are the o b j e c t o f p r e l i m i n a r y s t u d i e s d i r e c t e d towards determining economic and t e c h n i c a l v i a b l i t y - t h i s category i n c l u d e s f o r example the use o f sulphur in p l a s t i c s and b u i l d i n g products. The Commercial New Uses Sulphur Extended Asphalt Paving Mixes. On average a convent i o n a l road paving mix c o n s i s t s of 5%/wt. asphalt cement (AC) and 95% graded aggregate, w i t h the AC b i n d i n g the aggregate together



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to form a cohesive " f l e x i b l e " s t r u c t u r e . The hot mix is prepared simply by mixing hot l i q u i d AC and preheated d r i e d aggregate t o gether, g e n e r a l l y in the temperature range of 120-150 C (250300°F), t r a n s p o r t i n g the mix from the paving p l a n t to the job s i t e in dump t r u c k s and u n i f o r m l y a p p l y i n g it to the road s u r f a c e w i t h a paving machine. As the placed m a t e r i a l c o o l s through the temperature range of 80-100°C (180-210°F) it is d e n s i f i e d by m u l t i p l e passes w i t h compactive r o l l e r s . Molten sulphur can be e m u l s i f i e d i n t o hot l i q u i d AC and t h i s emulsion used in place of r e g u l a r AC as the binder in the paving mix ( 1). Such a system provides a number of p o t e n t i a l advantages: Reduction in AC usage - Stable sulphur asphalt emulsions can be produced w i t h up to 40%/wt. sulphur. Since binder volume is the c r i t i c a l f a c t o r in the paving mix, and s i n c e the r e l a t i v e d e n s i t y of the emulsion binder is greater than r e g u l a r AC, the s u b s t i t u t i o n of AC by sulphur is not a one-to-one r e l a t i o n s h i p . With a 40:60 emulsion, AC usage is reduced by approximately 27%/wt. This can provide a s i g n i f i c a n t cost saving as w e l l as a l e s s e r dependence on not-always r e l i a b l e a s p h a l t s u p p l i e s . Lower f u e l consumption - Binder rheology is f a v o r a b l y a l t e r e d w i t h the a d d i t i o n of sulphur. Of g r e a t e s t importanceist h e downward s h i f t in the v i s c o s i t y / t e m p e r a t u r e r e l a t i o n s h i p . Since paving p l a n t mixing e f f i c i e n c y is dependent on binder v i s c o s i t y , t h i s means t h a t the paving p l a n t can o f t e n be operated at a lower-than-normal temperature. In a d d i t i o n , the pavement can be d e n s i f i e d w i t h l e s s compactive e f f o r t . Both these advantages o f f e r a p o t e n t i a l f u e l savings to the paving o p e r a t i o n . Improved pavement performance - A f t e r the d e n s i f i e d pavement has completely cooled, the e m u l s i f i e d sulphur d r o p l e t s s o l i d i f y and act as a s o l i d f i l l e r f o r the binder f i l m . This system now e x h i b i t s c e r t a i n improved p r o p e r t i e s over a r e g u l a r a s p h a l t i c m a t e r i a l . The s t i f f n e s s / t e m p e r a t u r e r e l a t i o n s h i p f o r the sulphur a s p h a l t mix, w h i l e unaffected at lower temperatures, shows g r e a t er s t i f f n e s s at high temperatures. As a r e s u l t a sulphur asphalt w i l l show no greater tendency towards c o l d temperature c r a c k i n g , but w i l l d i s p l a y much greater r e s i s t a n c e to deformation at high temperatures; in p r a c t i c e there is a s i g n i f i c a n t improvement in r u t t i n g r e s i s t a n c e . Water s t r i p p i n g is g r e a t l y improved, and sulphur asphalt pavements e x h i b i t a higher load b e a r i n g c a p a c i t y which may enable a r e d u c t i o n in pavement t h i c k n e s s under a p p r o p r i ate c o n d i t i o n s . The manufacture of sulphur extended a s p h a l t paving mixes is r e l a t i v e l y s t r a i g h t f o r w a r d . Except f o r production of the emulsion binder i t s e l f , no mechanical change is r e q u i r e d in the paving p l a n t and normal procedures are f o l l o w e d . The s e v e r a l technologies which have been developed in t h i s area focus on methods of manufacture of the emulsion binder and s t a b i l i z a t i o n of the emulsion (2^-4). While the technologies do vary in complexity, a l l work q u i t e s a t i s f a c t o r i l y i f employed under s u i t a b l e c o n d i t i o n s .



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S t a b i l i t y of the emulsion is of prime importance. I f the emulsion breaks, the advantages of adding sulphur are completely l o s t , w i t h the impact on s t r e n g t h and d u r a b i l i t y p r o p e r t i e s p a r t i c u l a r l y d e t r i m e n t a l . As sulphur in a s p h a l t emulsions are uns t a b l e by nature, due a t t e n t i o n has to be p a i d to t h i s p o i n t . One technology u t i l i z e s the a d d i t i o n of a s u r f a c e - a c t i v e agent to enable the production of a very f i n e emulsion and to avoid coagul a t i o n and subsequent s e p a r a t i o n of the components. The d r i v i n g f o r c e behind the commercial acceptance of s u l phur extended a s p h a l t s is the cost r e d u c t i o n p o t e n t i a l . Improved pavement performance, w h i l e of importance, is a secondary c o n s i d e r a t i o n . AC p r i c e s have been s o a r i n g r e c e n t l y in tandem w i t h crude oil p r i c e s and continued r a p i d p r i c e e s c a l a t i o n is f o r e c a s t together w i t h geographic shortages of a s p h a l t . I n many p a r t s of North America a p a r t i a l s u b s t i t u t i o n of a s p h a l t by sulphur w i l l r e s u l t in a r e d u c t i o n in c o s t per tonne of hot mix, and of course the use of sulphur w i l l o f f s e t a s p h a l t shortages (of up to 27%), wherever these shortages may occur. F i e l d development and e v a l u a t i o n of sulphur extended a s p h a l t s has been going on s i n c e the mid-seventies. The f i r s t commercial placements of sulphur extended a s p h a l t s under c o m p e t i t i v e l y b i d c o n t r a c t s took p l a c e in North America in 1980. Of the a p p r o x i mately 160,000 tonnes of hot mix i n v o l v e d , over h a l f used the a d d i t i v e technology mentioned above, the remaining p r o j e c t s used a number of d i f f e r e n t approaches. A r a p i d growth is expected in sulphur extended a s p h a l t ' s share of the market: The N a t i o n a l Asphalt Pavement A s s o c i a t i o n (NAPA) is f o r e c a s t i n g sulphur extended a s p h a l t use to reach 58 m i l l i o n tonnes by 1990 in the U.S. alone ( 5 ) . I n l i g h t of the world energy s i t u a t i o n , t h i s is a very t i m e l y and important product which should be in r o u t i n e use in many p a r t s of North Ameri c a w i t h i n the next s e v e r a l y e a r s . Sand-Asphalt-Sulphur Road P a t c h i n g Mixes. One sulphur a s p h a l t product was developed s p e c i f i c a l l y f o r road p a t c h i n g app l i c a t i o n s and is being used commercially in Canada (6, 7 ) . The product c o n s i s t s of about 6%/wt. AC and 13% sulphur w i t h the r e mainder aggregate or f i n e sand, depending on the p a t c h i n g a p p l i c a t i o n . The l i q u i d AC, molten sulphur and hot aggregate are simply mixed in the c o r r e c t p r o p o r t i o n and placed in the pothole or depression u s i n g normal techniques. The mix i t s e l f is s e l f compacting and does not have to be d e n s i f i e d to develop s t r e n g t h . Consequently, a l e v e l i n g of the s u r f a c e is a l l t h a t is r e q u i r e d to o b t a i n a s t r o n g , durable patch. The mix can be used e q u a l l y s u c c e s s f u l l y f o r asphalt or concrete pavement r e p a i r . A c o n s i d e r a b l e economic b e n e f i t is o f f e r e d by t h i s product. Based on s e v e r a l years' experience one p r o v i n c i a l highway department estimates t h a t the i n s t a l l e d cost is 60% l e s s than f o r other c o n v e n t i o n a l p a t c h i n g m a t e r i a l s ( 7 ) . I n a d d i t i o n , the patches are proving to have a l i f e span 2-3 times longer than normally experienced f o r c o n v e n t i o n a l patches.


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To date, use of t h i s product has been l i m i t e d f o r the purpose of developing economic and commercial data. Once t h i s phase is completed, wider promotion should r e a d i l y broaden the use of this material. Sulphur Concrete. Sulphur concrete c o n s i s t s simply o f modif i e d sulphur and aggregate, w i t h sulphur comprising 10-15%/wt. of the mix, depending upon aggregate type and g r a d a t i o n and end-use a p p l i c a t i o n . The product is made by mixing hot aggregate and molten sulphur together and pouring the mix i n t o molds o r forms and a l l o w i n g it t o c o o l (8, 9 ) . Sulphur concrete possesses a number of advantages over r e g u l a r p o r t l a n d cement (PC) concrete. On the p r o c e s s i n g s i d e , it sets as soon as it c o o l s and gains f u l l s t r e n g t h in one day v e r sus the 28 days normally r e q u i r e d f o r PC concrete. U n l i k e regul a r concrete, ambient temperature c o n d i t i o n s a r e not a c r i t i c a l f a c t o r , so pours under w i n t e r c o n d i t i o n s can be made without any s p e c i a l p r e c a u t i o n s . The product has very h i g h r e s i s t a n c e t o c o r r o s i v e a c i d and s a l t environments and o f f e r s s i g n i f i c a n t advantages in those a p p l i c a t i o n s where r e g u l a r concrete has a poor performance r e c o r d . L i m i t a t i o n s on the use o f sulphur concrete a r e imposed by i t s h i g h temperature and f i r e s u s c e p t i b i l i t y . Although it w i l l not s u s t a i n combustion, under a p p l i e d flame the sulphur w i l l burn t o produce S O 2 . At temperatures above the m e l t i n g p o i n t o f sulphur, the product l o s e s s t r u c t u r a l i n t e g r i t y . Thus sulphur concrete is best s u i t e d f o r outdoor and underground use as w e l l as indoor c o n s t r u c t i o n a p p l i c a t i o n s where f i r e hazard is not a concern and b u i l d i n g codes a r e not a p p l i e d . The advantages of sulphur concrete have been known f o r a number of y e a r s , but one major t e c h n i c a l problem - the d u r a b i l i t y of the product under temperature c y c l i n g - has prevented broad c o m m e r c i a l i z a t i o n . A system o f pure sulphur and aggregate simply does not have the c a p a b i l i t y t o r e l i e v e s t r e s s e s caused by c o o l ing and s e t t i n g and temperature f l u c t u a t i o n s without c r a c k i n g . S e v e r a l technologies have been deyeloped which s i g n i f i c a n t l y improve the d u r a b i l i t y p r o p e r t i e s by p l a s t i c i z i n g the sulphur through r e a c t i o n w i t h other chemicals (10-13). U n f o r t u n a t e l y t h i s chemical p l a s t i c i z a t i o n is not permanent and w i l l reverse w i t h i n a time span as s h o r t as s e v e r a l months w i t h one technology to as long as s e v e r a l years w i t h another. Depending on the specific end use, t h i s r e v e r s i o n may not be a negative f a c t o r . Products such as f l o o r i n g and sewer pipe w i l l experience the most s t r e s s b u i l d - u p d u r i n g the i n i t i a l p e r i o d of time w h i l e the chemical p l a s t i c i z a t i o n is e f f e c t i v e . Once in use f u r t h e r s t r e s s due t o severe temperature changes is not l i k e l y to occur. However, other products such as b r i d g e decking, highway pavement and curb and g u t t e r can experience continuous s t r e s s i n g because of r a p i d c l i m a t i c changes. I n these cases, permanent p l a s t i c i z a t i o n is e s s e n t i a l f o r product d u r a b i l i t y .



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A r e c e n t l y developed technology takes a d i f f e r e n t approach to s o l v i n g t h e s t r e s s problem (14) . Rather than c h e m i c a l l y p l a s t i c i z i n g the sulphur, n o n - r e a c t i v e a d d i t i v e s a r e used t o h o l i s t i c a l l y p l a s t i c i z e the sulphur concrete mix. I n essence these a d d i t i v e s a r e l u b r i c a n t s which operate a t the sulphur/aggregate i n t e r f a c e t o a l l o w s l i p p a g e and s t r e s s r e l i e f without d i s r u p t i o n and c r a c k i n g . The apparent permanency of t h i s p l a s t i c i z a t i o n approach has been demonstrated by extensive t e s t i n g over a four year p e r i o d . By v a r y i n g the l e v e l o f p l a s t i c i z e r , t h e s t r e s s / s t r a i n chara c t e r i s t i c s of sulphur concrete can be designed to f i t the speci f i c needs of the end use a p p l i c a t i o n . The range covers from h i g h s t r e n g t h m a t e r i a l s i m i l a r to r e g u l a r concrete t o f l e x i b l e m a t e r i a l comparable to a s p h a l t i c concrete. As noted p r e v i o u s l y , w i t h chemical p l a s t i c i z a t i o n r e v e r s i o n to the h i g h s t r e n g t h b r i t t l e product occurs w i t h time, r e g a r d l e s s of p l a s t i c i z e r l o a d i n g . The c u r r e n t s t a t e - o f - t h e - a r t has s i g n i f i c a n t l y advanced the performance p r o p e r t i e s of sulphur concrete to a p o i n t where it is commercially acceptable. However there s t i l l are l i m i t a t i o n s on the d u r a b i l i t y of the product in extreme temperature regimes. Very recent research has developed methods o f i m p a r t i n g a cons i d e r a b l y higher d u r a b i l i t y t o sulphur concretes (15) . R e s u l t s i n d i c a t e a s u p e r i o r performance to PC concrete in t h i s regard, and as t h i s technology is f u r t h e r developed the l a s t r e s t r i c t i o n on the u t i l i z a t i o n o f sulphur concrete (other than h i g h temperatures) w i l l have been removed. A p p l i c a t i o n s f o r sulphur concretes f a l l i n t o two broad c a t e g o r i e s : u t i l i t y uses and high c o r r o s i o n performance uses. Utili t y a p p l i c a t i o n s r e f e r t o those f o r which PC concrete performance is r e l a t i v e l y s a t i s f a c t o r y , such as p a r k i n g bumpers, precast curb and g u t t e r , paving s l a b s and highway median b a r r i e r s . I n these a p p l i c a t i o n s in-place economics r a t h e r than performance is the c r i t e r i o n that w i l l determine commercial use. As a general r u l e of thumb, when sulphur and P o r t l a n d cement are t h e same p r i c e , sulphur concrete should be economically competitive f o r these applications. I t is in the h i g h c o r r o s i o n performance uses where P o r t l a n d cement concrete r a p i d l y d e t e r i o r a t e s that sulphur concrete w i l l enjoy a very s t r o n g p o s i t i o n - t h i s i n c l u d e s uses such as ind u s t r i a l f l o o r i n g , a c i d storage tanks, e l e c t r o l y t i c c e l l s , sewer pipes and b r i d g e decking where h i g h l y c o r r o s i v e environments are encountered . Table 1 shows an example of p o t e n t i a l savings to be gained in u s i n g sulphur concrete f l o o r i n g in a c o r r o s i v e e n v i r o n ment. Estimates i n d i c a t e that up t o 70-75% of the cost of other f l o o r i n g m a t e r i a l can be saved over a t e n year l i f e t i m e when replacement c o s t s are taken i n t o account. F i e l d e v a l u a t i o n of sulphur concrete has been conducted in a number of a p p l i c a t i o n areas - not always s u c c e s s f u l l y because many f i e l d placements a l s o i n v o l v e process development work.



2

Discounted Cost f o r 10 y r s . S e r v i c e ($/ft. ) R e l a t i v e to SC 10 3.3

3.7

PC Concrete w i t h A c i d Res i s t a n t Coating

11

10

Estimated L i f e (yrs.)

Placements in 10 y r . S e r v i c e

11

2

PC Concrete w i t h A c i d Resistant Brick

3.3

10

2.5

PC Concrete

10

Sulphur Concrete (SC)

Estimated r e l a t i v e costs o f f l o o r i n g in c o r r o s i v e environments.

I n s t a l l e d Cost ($/ft. )

TABLE I .


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USES

Much more needs to be done, but sulphur concrete is being used now on a s m a l l commercial s c a l e in s p e c i a l i z e d a p p l i c a t i o n s . And w i t h recent advances in m o d i f i e r technology, r a p i d commercial development and extension of the uses of sulphur concrete can be anticipated.


Moving Towards Commercialization - Molded Sulphur Blocks Although hot-poured sulphur concrete is very s u i t a b l e f o r poured-in-place and precast a p p l i c a t i o n s , the m a t e r i a l cannot at t h i s time be press-molded and is thus not amenable to h i g h speed/ high volume production of s m a l l b l o c k s . Although a p o t e n t i a l l y l a r g e market e x i s t s f o r b l o c k s of t h i s k i n d , such as t i l e and b r i c k , it was not u n t i l the l a t e 1970s t h a t an attempt to develop a c o l d mix/press-mold sulphur based technology was s u c c e s s f u l . This technology (16, 17) produces sulphur concrete b l o c k s by a manufacturing process very d i f f e r e n t from a hot poured sulphur concrete system. S o l i d sulphur, aggregate, l i q u i d and a m i n e r a l binder are mixed together c o l d and compacted i n t o a mold. Because of the presence of the s m a l l amount of l i q u i d and m i n e r a l b i n d e r , the product r e t a i n s i t s shape, although a t t h i s p o i n t the sulphur is not b i n d i n g the product together in any way. The block is then d r i e d to remove the l i q u i d and heated in an oven to melt the sulphur. Products made in t h i s way meet or exceed s p e c i f i c a t i o n s f o r PC concrete b l o c k s and in a d d i t i o n have a much higher r e s i s t a n c e to c o r r o s i o n than the PC products. The sulphur-based b l o c k s and b r i c k s should t h e r e f o r e f i n d ready usage in w a l l s , storage sheds, a g r i c u l t u r a l b u i l d i n g s , warehousing, f l o o r s and p a t i o s as w e l l as f o r low cost housing in those c o u n t r i e s which already use b l o c k construction extensively. The economics of t h i s technology appear promising, although f u r t h e r work is necessary to determine accurate c o s t s . The raw m a t e r i a l s are inexpensive and r e a d i l y a v a i l a b l e , and the manufact u r i n g equipment can be adapted from c u r r e n t l y a v a i l a b l e b r i c k and b l o c k process u n i t s . The system has a t l e a s t one process advantage over conventional b l o c k manufacture which w i l l p o s i t i v e l y a f f e c t the economics: because sulphur-based b l o c k s reach f u l l s t r e n g t h on c o o l i n g , the b l o c k s can be used w i t h i n a few hours of mixing the raw m a t e r i a l s . By comparison, c o n v e n t i o n a l concrete b l o c k s r e q u i r e a minimum of s e v e r a l days' storage f o r c u r i n g . Most of the l a b o r a t o r y development work f o r t h i s technology on mix design, f o r m u l a t i o n s , p r o c e s s i n g c o n d i t i o n s , property determination and d u r a b i l i t y e v a l u a t i o n has been completed. In a d d i t i o n , conceptual design and o p t i m i z a t i o n of process c o n d i t i o n s f o r a semi-commercial h y d r a u l i c b l o c k machine have been worked out.


9.

MUIR


135


Sulphur in A g r i c u l t u r e A g r i c u l t u r a l f e r t i l i z a t i o n w i t h sulphur is not a new concept - a t the research l e v e l a t l e a s t , sulphur has long been recognised as an e s s e n t i a l p l a n t n u t r i e n t . However because the complex r o l e o f sulphur - in s o i l s , in p l a n t m a t e r i a l and in i n t e r a c t i o n w i t h other e s s e n t i a l element c y c l e s - has never been f u l l y understood, sulphur f e r t i l i z e r s have been used mainly on an e m p i r i c a l b a s i s . As a r e s u l t , sulphur f e r t i l i z a t i o n has shown somewhat e r r a t i c performance: Measured sulphur d e f i c i e n c y in s o i l s has not always been c o r r e l a t e d w i t h poor crop y i e l d and, as a c o r o l l a r y , sulphur f e r t i l i z a t i o n o f sulphur d e f i c i e n t s o i l s has not always improved poor crop y i e l d s . Thus it has been d i f f i c u l t t o r o u t i n e l y demonstrate an economic b e n e f i t t o the farmer. Considerable research has been conducted on the uses o f s u l phur in a g r i c u l t u r e and of course cannot be d e a l t w i t h w i t h i n the scope of t h i s paper. But one program in progress in Canada is examining a very fundamental aspect o f the use of sulphur in a g r i c u l t u r e - a model that w i l l a l l o w p r e d i c t i o n o f sulphur requirements, l o s s e s and gains is being developed (18). Event u a l l y t h i s model could provide a complete mathematical explanat i o n of the r o l e o f sulphur in the s o i l system and be a p p l i c a b l e in any a g r i c u l t u r a l area. This work w i l l g r e a t l y enhance the r e l i a b i l i t y and e f f e c t iveness o f sulphur f e r t i l i z a t i o n and g r e a t l y improve the e f f i c i ency of a g r i c u l t u r a l food p r o d u c t i o n . I n l i g h t o f present and f o r e c a s t e d world food needs, t h i s w i l l be a s i g n i f i c a n t accomplishment . Summary Recent research has l e d t o a number of new products - severa l of which have been reviewed here - t h a t a r e being used commerc i a l l y o r are c l o s e to c o m m e r c i a l i z a t i o n . There is l i t t l e doubt that these w i l l gain broad use. Although f o r e c a s t i n g market s i z e in the short term is very d i f f i c u l t , a recent p u b l i c a t i o n by the U.S. Bureau o f Mines (19) estimates t h a t the probable annual demade f o r sulphur by new uses in the U.S.A. w i l l be 10 m i l l i o n tonnes by 2000. I n l i g h t of l o n g term trends, t h i s is not an unreasonable f i g u r e and i f r e a l i z e d , c e r t a i n l y i m p l i e s s i g n i f i cant commercial success f o r these new products.


136

SULFUR:

NEW

SOURCES

AND

USES

L i t e r a t u r e Cited 1. 2. 3. 4. 5.


6. 7. 8.

9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

19.

Rennie, W.J., New Uses f o r Sulphur, 2(2nd Ed.) Sulphur Devel opment I n s t i t u t e of Canada (SUDIC) 1979. Garriques, C., Signouret, J.B., Chambu, C., U.S. Patent 3,970,468 (1976) Pronk, F.E., U.S. Patent 4,154,619 (1979) Kennepohl, G.J.Α., Logan, Α., Bean, D.C., U.S. Patent 4,155,654 (1979) F o s t e r , C.R., NAPA S p e c i a l Report, N a t i o n a l Asphalt Pavement A s s o c i a t i o n , ( J u l y , 1980) Kopvillem, O., MacLean, J.W., Canadian Patent 945,416 (1974) C u l l e y , R.W., Saskatchewan Highways & T r a n s p o r t a t i o n T e c h n i c a l Report 29 (1979) S h r i v e , N.G., Gillott, J.E., Jordaan, I . J . , Loov, R.E., Poten tial & P r o p e r t i e s of Sulphur Concretes, American Chemical Society Meeting, A t l a n t a (1981) (This volume) Raymont, M.E.D., New Uses f o r Sulphur ( 4 ) , Sulphur Development I n s t i t u t e of Canada (SUDIC) (1978) S u l l i v a n , T.A., McBee, W.C., U.S. Department I n t e r i o r Bureau of Mines Report No. 8160 (1976) Leutner, Β., D i e h l , L., U.S. Patent 4,025,352 (1977) Vroom, A.H., U.S. Patent 4,058,500 (1977) Gregor, R., Hackl, Α., Adv. in Chem. #165 (ACS), 54 (1978) Gillott, J.E., S h r i v e , N.G., Jordaan, I . J . , Loov, R.E., U.S. Patent 4,188,230 (1980) Gillott, J.E., S h r i v e , N.G., Jordaan, I . J . , Loov, R.E., U.S. Patent A p p l i c a t i o n . Unpublished T e r r e l , R.L., U.S. Patent A p p l i c a t i o n 073,503 (1980) T e r r e l , R.L., Babaei, K., Proc. I n t . Conf, Sulphur in Con s t r u c t i o n , Canada 519 (1978) Bettany, J.R., "Sulphur Transformation in R e l a t i o n s h i p to Carbon and Nitrogen in Soil Organic Matter Studies", Sask atchewan I n s t i t u t e of Pedology. Not yet p u b l i s h e d . Shelton, J.E., " S u l f u r - A Chapter from M i n e r a l Facts and Problems, 1980 E d i t i o n " , P r e p r i n t from U.S. Department I n t e r i o r Bureau of Mines B u l l e t i n 671 (1980).

RECEIVED

October 5,

1981.


New Product Opportunities for Sulfur - ACS Publications - American

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