C o u r t e s y , Tennessee C o p p e r Co. Above, right and center: No. 1 chamber unit, capacity 850 tons 60' Be. acid daily, with 66' concentrator to extreme right. Below, right: sho B and warehouse. center: power house blast furnaces, converter, and roasters. Left: K O . 2 c h a d e r unit, capacity 3'50 tons 60' BB. acid daiiy. COPPER SMELTERY .4ND
ACID PLANT (LARGESTCHAMBER
Sulfuric Acid-to
PLANT I X THE WORLD) h T COPPERHILL,
TENN.
Buy or to Build?
AXDREWM. FAIRLIE, 22 Marietta Street Building, Atlanta, Ga.
S
HOULD we purchase our acid, or should we build a plant? This question confronts the large consumer of sulfuric acid from time to time. S o set of rules can be laid down that would be universally, or eren widely, applicable for answering this question. Conditions vary a t different places, and each situation calls for special study. To assist in the solution of such problems and in the proper weighing of the relative advantages and disadvantages of buying acid us. owning and operating an acid plant, the following list of the principal features should be considered: 1. Quantity of acid consumed daily by the prospective acid plant builder. 2. Continuity and uniformity of his daily consumption. 3. Probability of permanence in the use of sulfuric acid in the consuming industry. 4. Distance of the site from a source of supply of acid of the strength and purity required. 5. Availability of markets for the disposal of excess production during periods of small consumption at the plant site. 6. Freight rates on sulfuric acid. 7. Prices at which acid can be bought and sold. 8. Promptness of delivery of purchased acid. 9. Cost of constructing an acid plant of desired capacity. 10. Cost of raw materials, including sulfur material, delivered at the buyer's works. 11. Cost of operating an acid plant, including interest on investment, and all other overhead. 12. Competition in the sale of surplus acid. 13. Availability of capital for construct'ing an acid plant. 14. Availability of ground space at the site of acid-consuming works.
At most points in the eastern part of the United States, and a t many points in the western, sulfuric acid of satisfactory grade is purchasable a t such prices, delivered a t buyer's works, that the operation of a nitration plant of less than 30 tons of 60" B6. sulfuric acid daily capacity, or of a contact plant of less than 25 tons of sulfuric acid daily, is not profitable. Plants smaller than those specified exist and are operated within the selling range of large producers hav-
ing acid to sell, but for the most part such small plants were erected prior to the construction of the large centrally located plants now equipped to supply an enormous demand. In some cases these small plants continue to operate merely because they have been built and paid for. In other cases the relatively high cost of operating has been recognized, and the plants have been closed or dismantled. As an illustration of the tendency toward the abandonment of small sulfuric acid plants, in 1916 Georgia led all other states in the number of plants operating, with a total of thirty. Assuming an average operating year of 300 days, the average daily capacity of these thirty plants was about 32 tons of 60" BB. acid each. By 1929, while Georgia was still leading the other states in the number of establishments operating, the total number of Georgia plants had been reduced to eighteen, the average daily output of which wa9 still (on the same assumption as before) approximately 32 tons of 60" B6. acid. In the western part of the United States and in Canada and other foreign countries there are localities so far distant from a source of supply that a nitration plant of a capacity as small as 20 or 25 tons of 60' B6. sulfuric acid daily, or a contact plant as small as 15 tons daily, would be warranted. Only in extremely isolated or inaccessible localities would it pay to nianufacture acid a t lower daily production rates than the smallest just named. The question "to buy or to build?" should, in practically all cases, be decided largely on the basis of the cost of the purchased acid unloaded in the buyer's tanks vs, the cost of manufacturing, including all overhead. Such motives as enthusiasm, prejudice, envy, spite, keeping up with competitors, etc., should be discarded. During the 'twenties and early 'thirties a number of acid plants were erected in the United States on motives apparently of doubtful merit, thus adding unnecessarily to the production capacity of the country. Regardless of size, an acid plant ordinarily should not be
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built within a territory already adequately supplied with 130,000 tons annually was dismantled or destroyed, the acid plants, producing a t reasonable cost, and selling a t fair net gain in production capacity since 1929 was about 200,000 prices. While the newcomer in the field may think he has tons annually. Since it is known that some acid plants were an advantage, the consequence of an oversupply is almost idle and others were operating at less than full capacity during sure to lead to price-cutting, with profit to no one. As an 1929, and that the new plants erected in that year were comexample of ill-advised construction, there stands in a middle pleted a t various times and thus necessarily operated for a western city an acid plant erected a t a cost of over $300,000, part of the year only, it may be assumed that in 1929 the a t a point where the accessible markets were already over- production was not more than 95 per cent of the total capacity supplied. Thirteen a t the end of the year, years a f t e r complewhich may be placed, tion, this new plant t h e n , a t 8,900,000 had not made as ' tons. A d d i n g t h i s much as one pound of figure to the assumed net gain in capacity s u l f u r i c acid. No reason for b u i l d i n g of 200,000 t o n s f o r this plant has been the p e r i o d 1930 t o discovered, unless to 1933 places the estiuse it as a club for mated capacity of the hammering down country at 9,100,000 prices. But the club tons in terms of 50" must have proved far BB. a c i d . O n this basis the 1932 productoo expensive. It is safe to surmise that tion of acid was only the annual interest 48 per cent, and the on the investment in 1933 production only 57 per cent, of the the i d l e p l a n t h a s greatly exceeded the present capacity of a m o u n t s s a v e d by the c o u n t r y . The p u r c h a s i n g acid a t excess of capacity inCourtesy, P. Parrish, London reduced prices* This GAILLARD-PARRISH CHhYBER PL43'T, "EXPOSED"TYPE,FITTEDWITH d i c a ed b y these idle plant no doubt TURBO-DISPERSERS (ERECTED AT LONDOXIN 1930) figures exists somehas caused the where, and the promanufacturers first in the field to lose money; but the new- spective acid plant builder should determine whether any of it comer has lost more. exists within his territory before he builds a plant. A similar situation confronts the manufacturer proposing If the consumer expects to use all of his product a t his own to establish a metallurgical plant which produces sulfurous works, the question is simpler than if he intends to produce gas as a by-product. If the locality under considerationis more than he consumes and to market the surplus. Conisolated and free from legal restrictions on the discharge of suming all of his product, the manufacturer has no concern sulfur dioxide into the atmosphere, the smeltery may be with available markets or competition. If the consumption established without regard to the existence of acid plants in of such a manufacturer is small (less than 30 or 40 tons of the territory, provided the smelting operation can stand the sulfuric acid per day), i t is likely, in most thickly settled wastage of the sulfur fumes. But if the legal requirements localities, that he can buy the acid more cheaply than he can of the locality are such that a sulfuric acid plant must be built produce it. If the consumption is large, the acid consumer as an accessory to the smelting plant, then the matter of com- may be justified in building an acid plant provided his rate of petition in the sulfuric acid field should be investigated. If consumption is a!so constant. In a territory already adethe demand for acid is amply supplied by plants already in quately supplied with acid, a manufacturer whose acid the territory, it is usually uneconomical and unwise to con- requirements fluctuate widely is not warranted in building an acid plant of larger capacity than his minimum daily struct a new plant. In some cases a manufacturer who has been discharging demand, unless he also installs acid storage capacity large into the atmosphere or throwing on the dump-heap a sulfur- enough to serve as a balance wheel between his minimum and bearing waste product finds himself faced with new legislation maximum requirements. I n such a case the size of the acid prohibiting him from continuing such practice. I n such a plant should not be greater than sufficient to supply his avercase, if the only outlet the manufacturer can find for the age daily requirements. waste sulfur product is to convert it into sulfuric acid, ordiThe manufacturer planning to build an acid plant of larger narily he is justified in building a plant for that purpose, capacity than his own daily needs require should certainly even though the territory is already amply supplied with investigate well the marketing situation and the amount of acid. But prudence would dictate that arrangements be competition within his territory, and make sure that there is made with the acid manufacturers already in the field to an available unsatisfied demand, at prices profitable to him, dispose of the newcomer's acid in an equitable way. for his surplus acid before committing himself to such a According to the Census Bureau, the quantity of sulfuric program. I n addition to the constancy of the consumption of a manuacid produced in the United States, in terms of 50" BB. acid, was 8,491,114 short tons in 1929 (the all-time peak year) facturer planning to build an acid plant, a n important point and 6,085,242 in 1931. Published estimates of the produc- is the prpbability of permanence of the use of acid, in quantion for the years subsequent to 1931 place the figures a t tity, in the particular industry or the particular manufacturing 4,410,000 tons for 1932 and 5,168,000 for 1933 (1). Since plant involved. Some of the units of the petroleum refining 1929 new acid plants with an aggregate capacity of ap- industry seem to be on the verge of facing this question of proximately 330,000 tons annually (50" BB. basis) have been permanence too late and in an unpleasant light. During erected in the United States. If we assume that during the the past half-dozen years a number of petroleum refiners four years 1930 to 1933 acid plant capacity to the extent of installed sulfuric acid plants-some of them of quite large
December, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
capacity-to produce acid for use in their own refineries. Kow i t develops that the modern trend in oil refining is to adopt processes that use organic chemicals of various kinds or clay or zinc chloride or liquid sulfur dioxide (a). Those refiners that installed sulfuric acid plants, a t large capital outlay, may soon be ruefully concluding that it would have been better to have purchased their acid during the past few years, and thus to have left their way clear for the adoption of an organic solvent process of refining, without the sacrifice of an acid plant. Enough possible instances have been cited to show that each proposal of this sort is a separate problem, to be dealt
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with individually on its merits. It seems clear that, because a manufacturer consumes even a large quantity of sulfuric acid, i t is not therefore a foregone conclusion that it will’be profitable for him to build, in preference to buying. NOTE: This paper is p a r t of the manuscript of a n A. C. S. Monograph on “Sulfuric Acid Manufacture,” now in preparation.
LITERATURE CITED (1) Chem. & Met. Eng., 41, 35 (1934). (2) Keith, P. C., Jr., and Forrest, H. O., paper presented before New York meeting of Am. Inst. Chem. Engrs., May, 1934.
RECEIVED September
20, 1934.
Studies in the Vulcanization of Rubber V I . Thermochemistry JOHNT. BLAKE,Simplex Wire & Cable Company, Boston, Mass. on the assumption that vulcaniInoestigators generally agree that there is a subzation involves two successive the heat of vulcanization stantial ecolution of heat during the vulcanization processes: (1) the disaggregawas studied over the entire of rubber to f o r m ebonite. There are, however, tion of the rubber micelles, and sulfur range by heat-of-combusdifferences of opinion regarding the thermal (2) the reaction of this disagtion measurements. Data were gregated material with sulfur. changes in the soft rubber range (0 to 8 per cent also obtained on vulcanization The equation gives the same with m-dinitrobenzene and selesulfur), and past data are inconclusive. general type of curve as the exnium. Although it had been Qualitative data have been obtained indicating perimental ones. In a second known qualitatively that there that a small but definite heat evolution occurs paper (12) he extended his work was a heat evolution during a t during vulcanization with one per cent sulfur to include a c c e l e r a t e d comleast a portion of sulfur vulcaniand larger amounts are evolved at higher perpounds. In all of these cases zation, definite values were thus the maximum temperature also obtained for the first time. centages. T h e effect of a n accelerator and the occurred when about half the The results by this heat-ofaction of dinitrobenzene and selenium have also sulfur had combined. The concombustion method are, howbeen investigated. clusion was drawn that his hyever, of limited accuracy where T h e results tend to confirm the preciously pothesis of the mechanism of small heat changes occur. The proposed theory that vulcanization consists of two vulcanization is correct. method consists in the determinRiding (10) studied temperaing of heat-of-combustion values successive reactions: T h e Jirst, or soft rubber ture changes in the center of a on a rubber compound before react ion, is aflected strongly by accelerators and mass of compound during the and after vulcanization. Their involves little or no heat interchange; the second, formation of ebonite. He found difference represents the heat or ebonite reaction, is comparatively insensitive to that t h e e v o l u t i o n of heat content change brought about accelerators and strongly exothermic. began a t the same r e l a t i v e by vulcanization and involves state of vulcanization with all the subtraction of values of the mixtures-a coefficient of vulcanization of &and that about 10,000 calories per gram. From the data obtained the conclusion was drawn that little between 8 and 40 per cent sulfur on the rubber the reor no heat is evolved below 6 per cent sulfur but that there is a action was exothermic. The results were essentially the steadily increasing heat evolution beyond this to 300 calories same as those of Perks (9). Riding found an increased per gram of compound at 32 per cent sulfur. The first three temperature change in the presence of accelerators but points of these data ( 2 , 4, and 6 per cent sulfur) gave an concluded that it was due to the greater rapidity of the average value of 6 and a mean variation from zero of 18 reaction. Hada, Fukaya, and Kakajima (5) used the heat-of-comcalories per gram, representing approximately 0.05 and 0.18 per cent of the total heat of combustion-probably the order bustion method to study the heat of vulcanization. They of the accuracy of the determinations. In the presence of an claimed that the data of the present author are composite accelerator (diphenylguanidine) a definite heat evolution was values containing: (1) heat of reaction between pure rubber found beyond 4 per cent sulfur, although none appeared at 1 and sulfur, ( 2 ) heat of reaction between resins and sulfur, and 2 per cent. Vulcanization of rubber with m-dinitroben- (3) heat of reaction between protein and sulfur, and (4)heat of combustion of free sulfur. This is true of the first three zene and selenium did not seem to give an evolution of heat. Toyabe (11) has since measured the increase in tempera- items. There was little or no free sulfur in the samples used. ture in the center of three rubber samples during vulcaniza- They claimed also that the heat of formation of the nitric tion. He found that the maximum temperature occurred and sulfuric acids produced during combustion should have after about the same time interval and also determined that been corrected for, not realizing that the method of running in each case this point coincided with the combination of blank determinations probably automatically cancels all about half the sulfur. An equation was set up for the reaction such items. S A PREVIOUS paper (8)
