1ene glycol, tetraethyllead, chlorinated solvents, and a host of other essential chemicals. Unable to meet its total war time chlorine requirements from existing sources, the Government took up the roie of a chlorine producer. The govern ment's Chemical Warfare Service and the Defense Plant Corp. each built four plants, which made significant contribu tions to the chlorine supply. Between 1941 and 1944, chlorine pro duction was upped from 800,833 to 1,262,362 short tons a year. Despite t h e vast expansion of existing facilities and the creation of new plants, chlorine remained tight throughout the war. An exasperat ing bottleneck was the scarcity of tank cars. Consequently, even if chlorine pro duction had been increased much beyond its actual World W a r II level, the chlorine shortage would not have been materially reduced—without a concurrent increase in tank car capacity. As the hostilities drew to a close, it appeared quite inevitable to some indus try prophets that, once the wartime props were slipped out from under the market, chlorine manufacturers would be forced into drastic production cutbacks. That prediction never came true. The vigorous postwar demand for chlorine k manu facturers stepping livelier tha r. In
» JANUARY
2 9,
1951
Of Greatest Importance, Electrolysis Currently three basic procrssrs are commercially employed in the manufac ture of chlorine. Chief among these is the electrolysis of aqueous solutions of either sodium chloride or potassium chlo ride. In 1949 this process accounted for about 91 r/ r of U. S. chlorine production ( 8 1 r r of the total stemming from dia phragm cells and 77r from mercury cells). The electrolysis of fused salt for t h e pri mary production of metallic sodium is the second-ranking source of chlorine, s u p p b i n g in 1949 about 87c of t h e total output. Of least magnitude is t h e production of chlorine by the interaction of sodium chloride and nitric acid, also known as the nitrosyl chloride process. In 1949, this method, employed exclusively by t h e Solvay Process Division, was the basis for about l r / r of t h e nation's chlorine manu facture. Not included in these statistics is the chlorine output that accompanies the production of magnesium from mag nesium chloride. Because almost all of the chlorine generated is re-used in the preparation of more magnesium chloride from magnesium hydroxide, this source meets practically none of the chlorine requirements of outside users. Clearly, the most important single source of U. S. chlorine is t h e diaphragm c e l l so named because of its porous asbestos diaphragm which permits the free flow of ions and yet, by obstructing the inter action of cell products, minimizes t h e for mation of sodium chlorate. A diaphragm unit, such as t h e Hooker type S cell, is customarily run at about 10,000 amperes and 3.75 volts, to produce approximately 500 pounds of chlorine a day. The latest trend is toward use of higher amperages, with the most recent type of Hooker cell operating at about 20,000 amperes. Market Limitations Although there were times between World Wars I and II when inventories of 365
Diaphragm Cell Electrolytic Process
CI 2 GAS
COMPRESSOR BRINE SATURATOR
DIAPHRAGM
CONDENSER
CELL DRYING TOWERS
T A N K CASS
The feed for a diaphragm cell is a saturated solution of sodium chloride, from which such contaminants as calcium and magnesium salts have been removed. Once purified, the brine is fed con tinuously into the cell's anode compartment, where gaseous chlorine is evolved at the graphite electrodes. Simultaneously, sodium hydroxide and hydrogen are formed ai the iron cathode- The chlorine gas, hot and saturated with moisture, is then chilled to remove much of the absorbed water, the remaining traces of which are scrubbed out with concentrated sulfuric acid. The brine discharge from the diaphragm cell contains about 1 1 % caustic
electrolytic caustic were distressingly high, the demand for electrolytic caustic during that period was, in general, greater than the demand ior chlorine. By the time World War II ended, however, the situa tion had turned a right-about-face. The nation's chlorine requirements had tar exceeded its needs for electrolytic caustic, with t h e result that t h e post-World W a r II market limitations of caustic have hin dered the growth of the chlorine-caustic industry. One Washington consultant has esti mated that if the sale of co-product caustic during recent years had presented no problems to the chlorine-caustic indus
and about 15% salt. This solution is concentrated to about 5 0 % caustic by evaporation, which neatly precipitates out most of t h e contaminating sodium chloride. If desired, the liquor's remaining 1 % of sodium chloride may be almost completely eliminated by extraction with liquid ammonia, by crystallization of caustic as a hydrate, or by precipitation as the t r i p l e salt, N a O H N a C I Na2SC>4Removal of chloride ions, as well as such other impurities as iron and chlorate, is essential before diaphragm caustic can pass t h e stiff requirements imposed by the rayon industry—largest market for caustic.
try, chlorine output today might be roughly 7,000 rath-cr t h a n 6,000 tons a day. Last April, a trade magazine reported that the " d e m a n d lor chlorine continues to soar, while* caustic is piling u p like cigar butts at an all-night poker session." During recent months, however, t h e in creased raw material requirements of chemical manufacturers have m a d e siz able inroads into the nation's causticsupply. Nevertheless, W . I. Galliher of Pittsburgh Plate Class says: " T h e chief problem facing the chlorine industry in long-range planning is t h e ultimate caus tic soda consumption. C u r r e n t shortages in caustic h a v e temporarily relieved this
New S-3 cell installation at Tacoma, Wash., plant of H o o k e r Electrochemical Co.
366
C H E M I C A L
situation, but it is a p p a r e n t that the in creasing rate of consumption of chlorine is higher than the increasing rate tor caustic." Chlorine without Caustic T h e chemical industry lias spent mil lions of dollars a t t e m p t i n g to devise suc cessful chlorine processes that do not yield caustic as a companion product. T h o u g h useful to an extent, these alterna tive procedures suffer from one basic de lect. T o be economical on a mass produc tion basis, they require t h e profitable large-scale disposal generally of sodium or one of its salts. Almost always, these co-products either c o m m a n d a lower price t h a n caustic or attract a comparatively small volume d e m a n d . T h e growth of t h e sodium chloridenitric acid process, for example, has been stunted by the relatively low price ob tainable for its by-product, sodium nitrate. T h e production of chlorine from fused sodium chloride has been restricted by t h e limitations on t h e d e m a n d for ele mental sodium. Until production barriers such as these can b e overcome, the cur rently popular electrolytic processes which > ield chlorine a n d caustic soda will re main pre-eminent. A method for reducing the pile-up of electrolytic caustic has been recommended by R. B. MacMullin, consulting engineer. H e proposes that t h e sodium amalgam (containing 0.Γ to 0.3 r > by weight of sodium ) p r o d u c e d in mercury cells he used directly in t h e synthesis of com p o u n d s other t h a n caustic. Possibilities: metal alcoholates ( using amalgam plus anhydrous alcohol), sodium sulfide, hy drosulfite, chlorite, or nitrite ( by the reac tion of amalgam with sulfur, sulfur diox ide, chlorine dioxide, or nitrogen peroxide, A N D
E N G I N E E R I N G
N E W S
Mercury Cell Electrolytic Process The mercury cell, like the diaphragm cell, employs graphite anodes, but its cathode is a moving pool of mercury. As the salt solution is pumped into the mercury cell, chlorine is evolved at the anodes. At the mercury cathode» however, no hydrogen or sodium hydroxide is produced initially. Rather metallic sodium is formed as an amalgam. Either continuously cr intermittently, this amalgam is transferred from the chlorine-producing cell t o a separate decomposing chamber. There, in contact with water and graphite and under the accelerating action of the electric couple, the dissolved sodium reacts with water to form sodium hydroxide. Simultaneously, hydrogen is evolved at the graphite grids. Because mercury cell caustic is formed in an operation completely isolated from the brine feed, contamination of the product with brine is almost entirely eliminated. The approximately 5 0 % caustic solution which flows from the decomposing cell contains less than 0.002% sodium chloride.
respectively), and such organics as hyd r o q u i n o n e from quinone, glyoxylic acid from oxalic aeid, and pinaeones from k e tones. Acting on this suggestion, t h e m a n a g e m e n t of t h e Marathon P a p e r Mills of C a n a d a decided to produce b o t h sod i u m sulfide and caustic soda in its n e w mercury cell plant at Ontario. MacMullin has emphasized that t h e cost of t h e amalg a m , per p o u n d of sodium, is approximately one fifth today's price for p u r e metallic sodium. " T h e r e is no q u e s t i o n , " lie states, "but that, in specific instances, use of the amalgam cell w o u l d solve t h e problem of a local u n b a l a n c e b e t w e e n [the production of] chlorine a n d caustic soda." W i t h i n recent years, n u m e r o u s companies—among t h e m Esso S t a n d a r d Oil, Shell, Socony-Vacuum, Air Reduction, a n d Solvay—have tackled t h e problem of p r o d u c i n g chlorine from hydrogen chloride. In fact, one of the earliest a n d most widely used methods of obtaining chlorine was based on hydrogen chloride. T h a t was t h e D e a c o n process, t h e chlorine industry's once-valuable Model T. T h e Deacon process employed a c o p per chloride catalyst to p r o m o t e t h e air oxidation of hydrogen chloride to chlorine at a b o u t 450° C. Because it r e q u i r e d h i g h t e m p e r a t u r e s a n d yielded an exceedingly i m p u r e gas ( containing approximately 7 % c h l o r i n e ) , t h e process went out t h e w i n d o w with t h e a d v e n t of t h e electrolytic cell. However, interest in this basic a p proach has since been revived. Not long ago it was thought that once low-cost oxygen b e c a m e available, t h e direct oxidation of hydrogen chloride to chlorine might prove exceptionally attractive. D e spite the best expectations, t h e price of oxygen has yet to drop sufficiently t o m a k e any real difference. Recently, t h e YVestvaco C h e m i c a l D i vision developed a method for o b t a i n i n g chlorine indirectly from b y - p r o d u c t h y d r o g e n chloride. T h e process involves t h e electrolysis of cupric chloride t o chloV O L U M E
2 9,
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SECTION OF ELECTROtYZSR
SECTION OF ANtALQANl DECOMPOSER:
WATER FEED DÉCOMPOSER COVSR:
' «HlORiNE DUCT
IROM CATHODE
N ear in a succession of rapid-fire announcements, the chlorine industry d i s closed at least a few of its plans for sizable expansion. In October Dow reported that, at a cost of about $1.5 million, it would boost by one third its output of chlorine and caustic at Pittsburg, Calif. Stauffer Chemical stated that when it winds u p its construction program at Niagara Falls early this year, its chlorine a n d caustic capacity will b e doubled. L a s t November Stauffer placed a fourth line of electrolytic cells in operation at H e n derson, Nev. Frontier Chemical of Kansas. Inc. reported that it is in the mi 1st of erecting near Wichita, Kan., a chlorine plant based on Hooker type S diaphragm cells. This plant was originally the 2 5 ton-a-day installation owned by General Electric at Pittsfield. Mass. Late in October Hooker Electrochemical at Tacoma, Wash., finished replacing t w o of its circuits with new, high-capacity type S-3 cells. This year Southern Alkali at Lake Charles, La., will increase its chlorine production by 2 5 r * . while D i a mond at Houston, Tex., will enlarge its facilities by 509r. Reports are that t h e Ethyl Corp. plans to build a 70-ton-a-day CHEMICAL
Although m 1S-I2 the nation's chlorine output accounted for about 4 5 r r of world production, by the end of 1948 the U. S. contribution had climbed to at least 60 to 70r/c. Apart from the United States, the world's largest chlorine producers are Germany, Japan, Great Britain, Canada, and F r a n c e , most of which rely predominantly upon mercury cells. In 1939 Canada had only one chlorinecaustic plant not operated by its pulp and paper industry. After World W a r II. however, the country doubled its chlorine production by building four additional mercury cell plants. It is expected that C a n a d a will be able to obtain domesticall> all the chlorine it needs w h e n at the end of this year its production exceeds 400 tons a day. Of this, about 757c will be based on mercury cells. Chlorine does not lend itself readily to foreign trade, principally because it must be transported under pressure as a liquid in heavy cylinders or tank cars. Verylittle chlorine was imported into the United States prior to World W a r II. D uring the war, however, imports picked up markedly as Canada b e c a m e the main outside supplier. In the peak year, 1945, t h e U. S. brought in 6,827 short tons of chlorine, but since World W a r II chlorine imports have been practically nonexistent. Although applied research in the design a n d operation of both diaphragm and mercury cells goes on continuously, recent advances have been relatively minor. Unmistakably, however, t h e trend in the chlorine industry has been toward bigger cells having greater capacity per unit of floor space. Other advances have involved t h e development of safer, more economical methods of storing and transporting the liquid element. Significantly, chlorine producers, now more than ever, are chlorine consumers. T h e driving force is the greater profit margin on chlorine derivatives. In 1939 only 34f/f of tin* chlorine produced in the United States was used right on the spot. By 1950, 70'"/ of U. S. chlorine was consumed by the producing plants. Industrial
Mobilization
Several months ago, at the start of the industrial mobilization program, chlorine was catapulted into the headlines. Because of the far-reaching effects of the shortage, chlorine has appeared in t h e news with increasing frequency ever since. During the same period chlorine has been AND
ENGINEERING
NEWS
T a b l e 1.
C o m p a r i s o n of M a n u f a c t u r i n g
Products: Clo NaOH Total
Costs" p e r T o n o f P r o d u c t
Β
5 0 0 tons a d 3y o f wet cell gas 5 6 . 4 tons a d a y o f 5 0 % lie uor T 0 6 ^ 4 tons a d ay ( 1 0 6 . 4 uni s of w e t Cl'2 D i a p h r a gm Cell Unit ~ consump tion''
Unit price
Unit cost
+ 50%
NaOH)
|
M e r c u r y Cell
— Unit
consumption '
1
Unit
1
cost
I
$4.94
1
0.90
I
Raw materials Rock salt, ton r D i a p h r a g m cell g r a p h i t e , l b . M e r c u r y cell g r a p h i t e , l b . Sodium c a r b o n a t e , l b . Hydrochloric acid, lb. Sodium h y d r o x i d e , lb. M e r c u r y , lb.
$6.00 0.26 0.20 0.015 0.02 0.02 1 .00
0.824 3.3
$4.94 0.86
0.824 4.5
6.0 1 .3 0.5
Total r a w m a t e r i a l s
0.09 0.03 0.01
26.0 8.0 0.17
5". 9 3 ~ "
Power S t e a m , thousand lb. Electricity, kw.-hr. W a t e r , thousand g a l .
4.75 1426 14.6
0.50 0.005 0.03
2.38 7.13 0.44
0.50 1707 0.70
9.95"
Total power Labor O p e r a t i n g , m a n hr. M o n t h l y , man hr.
1 .52 0.22
1 .75 2.00
2.66 0.44
2.02 0.22
3.10
Total l a b o r Repairs a n d maintenance L a b o r , m a n hr. Materials Overhead ( 4 0 % repair labor}
0.58
1 .75
Total r e p a i r s and m a i n t e n a n c e Miscellaneous supplies Works overhead Direct, superintendents Indirect ( 4 0 % l a b o r + 3 % investment T a x e s a n d insurance ( 3 % investment) D e p r e c i a t i o n ( 6 % investmen 0
Ί
T o t a l works o v e r h e a d (without a m o r t i z a t i o n )
1 .02 1 .02 0.41
0.70
!
1 I J
0.25
1
8.54 0.02
1 1
8.81
I
3.54
1
0.44
I
3 798~
1
1 .22 1 .22 0.49
!
2.45
2.93
0.60
0.28
0.44 3.04 1 .80 3.60
0.26 3.69 2.10 4.20
8.88
O t h e r Government Aids
1 0.25
$30.91
Production cost p e r unit
0.52
0.16 0.17 6.69
$32.94
a
M a n u f a c t u r i n g costs c h a r g e a b l e only t o electrolysis. K n o w i n g the t o t a l d a i l y consumption of a n y i t e m , you o b t a i n the unit consumption b y dividing by 106.4. r A t y p i c a l e l e c t r o l y t i c p l a n t consumes 1 .75 tons o f salt p e r ton o f CI2 p r o d u c e d . d For d i a p h r a g m cell p l a n t : $ 2 , 3 3 0 , 0 0 0 ; f o r mercury cell p l a n t : $ 2 , 7 2 0 , 0 0 0 . These investment estimates include on ly items c h a r g e a b l e to brine h a n d l i n g , the cell r o o m (including cells, c o p p e r , miscellaneous ec uipment, cell r e n e w a l , b j i l d i n g s , roy alties, and fees), caustic e v a p o r a t i o n (including s t o r a g e a n d s h i p p i n g ; , a n d mercury arc rectifiers (including b u i l d i n g s ) b
t h e subject of several government confer ences, much industry and government planning, a n d even more offstage specula tion. On Sept. 18, 1950, the National Pro duction Authority ordered a clampdown on t h e hoarding and excessive buying of six critically scarce chemicals, including chlorine. At its meeting on Nov. 3, NPA's Alkali-Chlorine Industry Advisory Committee discussed t h e distribution of defense orders ( D O ' s ) as it affected pro ducers of alkali a n d chlorine. In October Ν Ρ A h a d set up a priority system which m a d e it mandatory for manufacturers to give first attention to government defense needs. In t h e ensuing weeks, some com panies were swamped with DO's, while others received few if any. As a result, t h e operations at some plants were un necessarily disrupted. Chlorine companies h a d few objections to the basic intent of V O L U M E
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the D O regulations, but they did argue with compelling logic that defense orders should be distributed equitably through out the industry. T h e Alkali-Chlorine Industry Commit tee met once again on Dec. 5 to thrash out a proposed order designed to equalize the distribution of DO's. The committee suggested that no chlorine producer be required to accept DO's for more than l()r/( of his scheduled marketable produc tion within any given month. Furthermore, the committee recommended that no pro ducer be required to accept a D O if re ceived less than 15 days before the begin ning of the mondi in which shipment is desired. In an effort to assist the small businessman, the committee proposed that small companies be permitted to obtain as much chlorine as they received in com parable months of 1950. To guarantee that the nation's high health standards are
JANUARY
2 9,
1951
maintained, the group recommended that enough of the total marketable produc tion of chlorine be made available lor water purification, sewage disposal, and emergency public health needs. Earlier, the committee turned its at tention to the matter of cross hauling. Many industry men agree that the elimi nation of cross hauling could greatly fa cilitate the distribution of chlorine. T h e in-transit time of thousands of tank cars could be substantially reduced if con sumers could be supplied not necessarily by the company from which they purchase chlorine but by the company which is t h e least distance away. Nowadays, unless manufacturers care to run afoul of the antitrust laws, they cannot conclude such trade agreements without the prior blessing of the U. S. Government. However, the adoption of a more liberal policy toward arrangements of this sort—which were temporarily legal ized during World War II—is currently under government consideration. At present, government aid to industry can take the form of Certificates of Ne cessity. Issued by the National Security Resources Board, these tax concessions allow new defense plants to be totally depreciated within five years. Under t h e terms of NPA Regulation No. 5 1 , t h e Government may also accelerate indus try's emergency expansion by the grant ing of direct loans.
What other forms of government assist ance are needed? Said C. W. Cannon, president of Frontier Chemical Co.: "Under the present defense order system, there is no assurance that materials can be obtained for basic manufacturing con struction. Particularly indefinite are d e liveries on nickel and electrical equip ment. Unless the chlorine-caustic indus try can obtain assured delivery of t h e critical items necessary to complete con struction, it will be reluctant to start n e w construction to alleviate the chlorine shortage. There should be an allocation or priority system covering construction of basic manufacturing plants." "Some form of allocations for chlorine is needed," advised one manufacturer. "This is particularly true because of t h e mounting indications that D O orders will seriously disrupt the conduct of business." An industry spokesman urged that t h e Government "clearly forecast its own chlorine requirements if it expects to p u t an end to the present confusion." Said another: "Surprising as it mr.y seem, a few small chlorine plants are not running at peak capacity. Certainly if these plants were operated to the full, their added contribution to the chlorine supply would be significant." Though they may wrangle over details, manufacturers are unanimous in asserting that actually there is only one real way to beat the chlorine shortage. That is by production—more production—and still more production of chlorine. 369
