Commercial Explosives Industry J
C. A. WOODBURY AND W . C. HOLMES
E. I. du Pont de Nemours & Company, Inc., Wilmington, Del.
W
H E N Governor Winthrop in 1635 became powder industry, but the subsequent developments were not actively interested in the establishment contemplated a t the outset. of colonial industries, the production of While there doubtless was earlier small-scale production of saltpeter for gunpowder was undoubtedly one of the materials powder by individuals and by mill owners, the first definitely in mind. This is indicated by the fact that an order of the recorded powdermill was erected a t Milton, Mass., about six General Court of Massachusetts, passed in 1M2 through Winmiles from Boston, in 1675 This mill was established a t a throp’s influence, provided that every plantation within the very opportune time, for powder was furnished to the coloColony should erect a house of prescribed dimensions for nists during King Philip’s War which broke out in 1675. An making saltpeter, or, in other words, for producing such mateinvestigator from England attested the quality of the product, rials “as will perfect the making of gunpowder, the instrureporting that “the powder is as good and strong as the best mental means that all nations lay hold on for their preservaEnglish powder.” The government in England, however, tion. ” did not favor the building of strong industries in the Colonies, I n the plans for this industry the use of powder in hunting and the manufacture of gunpowder on this side of the Atlantic and in defensive warfare was doubtless in Winthrop’s mind. was relatively small up t o the time of the Revolutionary War. At that time there was no knowledge, on the part of the Black Powder Industry colonists, of blasting or construction work by means of explosives. The first use of explosives in mining that is supFACTORSFAVORING EXPASSION. The history of black ported by documentary proof dates back only to 1627. This powder in the colonial days of -4merica is the story of gunuse was in Hungary, and even up to 1670 the employment of powder alone, since little attempt seems t o have been made explosives for breaking down ore seems to have been practito secure powder for any use except in firearms. The Revocally unknown in England. lution greatly stimulated the industry, however. Whereas If a land such as America were now in the colonial stage, it is stated that, just prior to the war, not a single powderwith the information now available, a similar government mill was in operation in the Colonies and that the American proclamation would probably provide for the production not mills produced only about 815,000 pounds of powder during the first two years of the war, while imports were approxiof gunpowder but of explosives, and the contemplated impormately twice that amount, by 1790 the domestic producers tant uses would be mining, quarrying, and construction work. What started as a “gunpowder” industry has grown to be a dominated the home market. Pennsylvania’s twenty-one vast and diversified explosives industry composed of more powder mills alone are said to have had a total annual cathan twenty companies, supplying to industry annually pacity in 1786 of 625 tons. Many factors helped t o bring about a great expansion in around 300,000,000 pounds of dynamite and 100,000,000 the explosives industry in the years between the Revolution pounds of black powder. This tremendous tonnage of explosives is employed t o loosen from mother earth around and the Civil War such that the production of powder had in50,000,000tons of iron ore, 500,000,000 tons of coal, 150,000,creased to 1,500,000 pounds in 1810 and nearly 9,000,000 pounds by 1840. It was the beginning of a great engineering 000 barrels of cement rock, together e t h large amounts of and construction era, probably stimulated by the availability gold, silver, copper, lead, and zinc ores. I n addition, it -of explosives and s e r v e s in blastthe knowledge of ing tunnels for methods for their railroads and manufacture and a q u e d u c t sysuse. While the tems, quarrying composition of s t o n e f o r road the powder had building, c l e a r not changed mai n g l a n d of terially, actually stumps, blasting i t was n o t so ditches, and much gunpowder deepening haras blasting bors and navipowder that was gable streams. now in demand. The commerAbout thirty cial e x p l o s i v e s canals are listed1 industry is a 1 Drinker, “Explclogical outsive Corn p o u n d a . g r o w t h of t h e Machine Rock Drills hfOWBRAY’S NITROGLYCERIN FACTORY AT NORTH h A M S , hIASS., ABOUT 1870 and Blasting.” 1883. colonial gun632
dustry. The influence of the Civil War, however, was very considerable. The demand for powder naturally inc r e a L, ed g r e a t l y , a n d t h i s , in turn, created problems in obtaining an adequate supply of raw materials, particularly saltpeter, which was the principal ingredient and which had to be imported in considerable measure. A certain amount of saltpeter was made, however, from sodium nitrate by conversion with potash or potassium chloride. As is well known, the southern states were hampered even more because of their inability to import and were obliged to resort to primitive measures for the production of saltpeter. Following the war, the industry was left in a temporarily demoralized condition because of the greatly increased production capacity of the country and the excess stocks of powder in the hands of the Government, which was sold a t public auction. During the period described, the powder industry comprised a great number of relatively small concerns. One name stands out because of its influence on the commercial explosives industry for over a century and a quarter, down to the present time. It was in 1804 that the manufacture of powder was begun by E. I. du Pont de Kemours, who founded the business that has continued under substantially the same name, always the most important factor in the American explosives industry. The period of expansion for the black powder industry did not end with the Civil War, though this explosive soon had to share the blasting business with the new competitor dynamite, which was better adapted for use in hard rock blasting. Black powder was still the preferred explosive, however, for many uses-in the mining of coal and soft rock, for example, where a shattering effect was undesirable. The production of black powder reached an all-time high in 1917, when over 277,000,000 pounds were produced. Of this amount, about 85 per cent, or approximately 236,000,000 pounds, was used in mining coal, and the other 15 per cent in other mining and construction work. Since the advent 01
:is being condructed betxeen 1790 and 1850; the most impressive were the Erie Canal, begun in 1819 and completed in 1825 at a cost of more than $10,000,000, and the Chesapeake and Ohio Canal, commenced in 1828 and iinished in 1850, costing about $12,000,000. The building of the Erie Canal, a tremendous undertaking for its time, is said to have given an impetus t o the spirit of public improvement in all parts of the country. The era of canal building was followed by one of railroad construction. Drinker lists twenty-seven railroads constructed mainly in the years between 1830 and 1840. The most important of the early railroad undertakings was that of the Baltimore and Ohio; the work commenced in 1828 and cost over $20,000,000 up to 1853, a t which time Baltimore had been connected t o Wheeling by way of Harpers Ferry, a distance of 379 miles. Along with the building of canals and railroads came the construction of canal and railroad tunnels; nver thirty were built between 1820 and 1850. Mining operations began to use explosives during this era in increasing quantities. Many such operations required only limited amounts of explosives, and it was a rather general custom for powder plants to be located near the place of use. Anthracite coal mining, later a great consumer of explosives, was practically begun in 1820, when the Lehigh Navigation and Coal Company sent 365 tons of coal to Philadelphia, a quantity that completely stocked the market for the year. I t is interesting to note that hard coal mining had become so important by 1840 that Luzerne County had assumed the lead in Pennsylvania in the number of powder mills and their output. Iron mining likewise consumed its quota of black powder, &ce the production of pig iron increased in the period from 1810 to 1860 from about 54,000 to over 800,000 long tons. Other operations that required explosives were granite, slate, 633
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dynamite, the proportional use of black powder in blasting has decreased until it now represents only about 25 per cent of the total explosive consumption. It has been substantially replaced in all types of blasting operations except in the mining of coal, and this industry in 1934 consumed about 88 per cent of all the black powder used. The production of black powder had decreased to about 120,000,000 pounds by 1929 and 64,000,000pounds in 1932 from its maximum annual production of 277,000,000 pounds. The use of black powder in
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It seems to have been the practice to locate powder milla along rivers or small streams where water power was available. Power-driven machinery was in general use therefore. Hydraulic presses mere substituted for hand-operated screws about the time of the Civil War Power corning mills had come into use about 1840 and automatic devices were later added, so that the mills required no attendance after starting. Subsequently, a safety device was introduced that automatically \topped operations if any hard foreign material came between the rolls. Automatic machinery, in fact, has been a feature of the best American powdermill practice. After the worst of t h e d e p r e s s i o n in t h e powder business, following the Civil War, the great increase in coal mining caused a demand for black blasting powder, because of the particular suitability of this low-velocity type of explosive whereby the coal was obtained in large lumps. With the introduction of safety dynamite explosives of the permissible type in the early part of the twentieth century, the black powder industry appeared t o be on the down grade. In 1925, however, the introduction of pelleted black powder started a new interest in an old industry. Pellet powder was originally developed in Europe and consists of cylindrical blocks of black powder packaged in a wrapped cartridge similar to a stick of dyna19M 19s mite. These cartridges commonly comprise four 2-inch pellets, of a diameter varying between inch and 2 inches, with a longitudinal hole extending through the pellets; they furnish a safer, handier, and more usable form of powder for the miner. The introduction of pellet powder immediately stimulated development work to produce powder varying with respect t o speed and density so as to be better adapted to the different types of coal blasting in this country. I n 1930 a high-speed, low-density pellet was introduced, followed in 1932 by a lowdensity cartridged wheel cake powder. j / g
firearms has, of course, largely given way to smokeless powder, a development that began in the last decade of the nineteenth century. TEc”1c.4~ DEVELOPMENTS. The developments in the manufacture of black powder have been essentially in the improvement of the physical properties of the product rather than in the cheniical composition. A gunpowder made in England in 1647, for example, had the composition 69.1 per cent saltpeter, 15.3 charcoal, and 15.3 sulfur, and present day formulas are very close to this composition. The one outstanding American chemical development was the replacement of potassium nitrate by sodium nitrate in blasting powders, though the potassium salt remained in the gunpowder formulas. The sodium nitrate blasting powders were patented by Lammot du Pont in 1857. and the change was of great economic importance to the American industry. Control of the ingredients has, of course, been vastly iinproved. Supplies of charcoal were a h a y s readily obtained a t home. Satisfactory grades of saltpeter in adequate amounts appear always to have been imported. The early colonists were able to make a crude saltpeter in small quantities from various sources of nitrogenous waste. I n the early part of the nineteenth century, sources of saltpeter were found in the various limestone caves. Sodium nitrate was more available in the form of “nitrous earths” found in a number of locfttions and could subsequently be obtained from Chile. Satisfactory supplies of sulfur appear to have been obtained almost wholly by importation, until the development of the American industry in elemental sulfur. Various technical manufacturing developments may be briefly noted. Stamp mills for the moist pulverizing and mixing of black powder ingredients gave way rather generally in the larger plants to wheel mills in the early part of the nineteenth century, with the result that a superior powder was obtained from the viewpoint of incorporation. This adoption of wheel mills seems to have been first made in America about 1810, but some European countries had used them previously.
Dynamite Industry INTRODUCTIOK I N THISCOUNTRY.The early history of the dynamite industry is essentially the story of the accomplishments of the Swedish inventor, Alfred Kobel, and no industry was ever more fortunate in its founder While the United States cannot claim the credit for the conception of dynamite, this country appreciated the new product almost a t once and started using it on a large scale. Nobel’s first contribution was to introduce nitroglycerin a \ a practical commercial explosive in 1862. Since this compound is essentially a detonating compound, unlike black powder, it was only after Xobel’s introduction, about 1865, of an early form of blasting cap containing mercury fulminate that nitroglycerin could be effectively detonated. Liquitl nitroglycerin was used rather extensively as a blasting agent for a year or two, being transported by boat and rail. A considerable number of serious explosions occurred, however, notably one a t Panama where about sixty people were killed. Because of the great hazard involved, Kobe1 turned his atterition to devising a safe method for the transportation and U ~ C ) of nitroglycerin. I n 1866 Kobe1 conceived the idea of mixing nitroglycerin with a suitable absorbent whereby he obtained, in place of a liquid dangerous to transport and difficult to handle, a solid sensitive to the action of a blasting cap but relatively insensitive to ordinary shocks. This product was dynamite, kieselguhr being used as the first absorbent. Nobel’s last fundamental contribution was the discovery, about 1875, of the fact that nitroglycerin could be converted into a solid, plastic
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mite. The so-called Judson powders, named a f k r the inventor, E. P. Judson, were of this type and map be considered as perhaps the first’ real American contribution to the dynamite industry. Judson powder was patenbed in 1876 and was in standard use for many years, particularly the R R P (railroad powder). This powder was essentially a black powder composition in which originally the ingredients were heated above the melting point of sulfur. By raking the mixture during cooling, solid grains were formed, with which 5 per cent or more of nitroglycerin was mixed. i4bout 1922 a substantially free-running polder was intrciduced, not requiring the hot treatment of the ingredient., thus eliminating an undesirably hazardous manufacturing operation. The new powder n-as low in nitroglycerin content and practically noninflammable, the free-running effect being obtained by the use of coarse ammonium nitrate and coaric sodium nitrate particles. This idea was later extended Ijy the incorporation in such a powder of a coarse, granular : i l r~l . m t such as sawdust. Xitroglycerin has from the start been the basis o f the tlynamite industry and no substitute has been developed that can begin to take its place completely. American practice, however, has more and more t’ended to the replacement of a porDevelopment of Finished Products tion, and in many cases much, of the nitroglycerin by animonium nitrate, an inorganic salt which i c completely conThe United States has been a great consumer of blasting verted into gaseous products on decomposition arid which is explosives because of the rapid and progressive development itself an explosive when properly sensitized by nitroglycerin. of the country since the beginning of the nineteenth century The replacement of nitroglycerin by ammonium nitrate gives and because of the shortage of labor throughout most of that a product less sensitive to shock and one that is commercially period. Black powder appeared to offer little chance of att’ractive. s t a r t 1i n g improveAmmonium nitrate ments. From the inhas the disadvantage troduction of dynaTO ALASKAN SOLO a SILVER MINES of being highly hygrom i t e , however, a scopic, a serious discharacteristic Smeriadvantage in tlynacan industry has mites which are often evolved. While much stored for considerthe same raw mateable periode under adrials are used here as verse nioisture condiin Europe, the prodtions. The success of ucts are quite differthe American exploe n t i n m a n y essensives industry in using tials. ammonium n i t r a t e One of the depardynamites has been tures from European clue to the recognition practice was the use of the necessity of proof active i‘dopes” in t e c t i n g t h e ammothis country-absorbnium nitrate properly. ents that were comIn 1885 R. S. Pennibustible and t h a t FIGURE 2 . v man made practical added t o the strength of the explosive by the dynamites containing LOCATION OF e DYNAMITE PLANT increased volume of this salt by mixing the ABLACK POWDER PLANT gases p r o d u c e d on ammonium n i t r a t e EXPLOSlVES PLANTS DWTING C A P 8 s W l B PLANT combustion. S i n c e with a small amount COAL [m3;tADkZlNC WITH RESPECT T O PRINCIPAL a b s o r b e n t s such as of p e t r o l a t u m or IRON ORE COPPER wood pulp required similar coating agent. MINERAL DEPOSITS GOLD & SILVER additional oxygen for The coated n i t r a t e their complete comcould t,hen be incorbustion. balanced porated with the ot,lier dopes were obtained by the introduction of the proper amount ingredients. The so-called ammonia dynamites, containing of sodium nitrate or other oxidizing salt into the composition. both nitroglycerin and ammonium nitrate, became of great Kieselguhr dynamites have never been important in this importance in the industry. Penniman laid the foundation5 country, and the literature of explosives appears to have for ammonia dynamites by developing both process and equiprecognized the active-base dynamites as an American type. ment for the low-cost production of grained ammonium ni-4nother American activity was in the direction of freetrate. The eventual success of this type of dynamite wab running dynamites--that is, explosives that had something assured, however, when in 1912 the industry placed the manuat least of the free-flowing properties of granular black powder, facture of ammonium nitrate by the Penniman process on a so that they could be poured into the borehole, while at the systematically controlled basis with regard to grain - 1 ~ same time they had the high-velocity characteristics of dynamoisture content, and method of handling.
material by incorporation x-ith about 8 per cent of nitrocotton. This -was the beginning of blasthg gelathi and the highly important gelatin dynamites. One of the earliest and most spectacular uses of nitroglycerin in the United States mas by Mowbray who started its manufacture a t Korth iidams, Mass., in 1867, for use in the construction of the Hoosac Tunnel. Mowbray is said to have produced over a million pounds of nitroglycerin a t his S o r t h ddams factory in the next few years, considerable of this being shipped to various points in the eastern part of America. It is interesting to note that RIowbray shipped nitroglycerin as the solid, frozen product in tins, and not in absorbed form as dyilamite. RIowbray’s success T\ ith nitroglycerin was probably due to his careful use of pure raw materials and purification of the final product. The first dynamite plant in America was constructed in 1867 by the Giant Powder Coinpany near San Francisco, Calif. This was only a little over a year after Nobel’s introduction of dynamite and before the siiccess of dynamite was certain. Raw materials such as glycerin and kieselguhr had to be imported from Europe.
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Very recently (1935) a siea. blasting explosive, comprised pcrniissibles but iriaile more plastic mid ivatcT ;osistant by tlw si1)sttuitialIy of animoiiiuni nitrate, I i m Ireen placed on t l i e iiicliiiiou of a very Iav percentage of nitrocottori in the formula. iiiarket, for use in Inrge-diameter, well-drill qiiiirry lkastitig. A phase of explosive development in wliicli tliis country 'l'ilis iiew product is cltaracteriaed by itti unnsually high degree 1i:is gone farther thail ;uiy ot,iier lras ireen the iniproveineiit / > / safet,y. Iilasting eiiiciency, atid winter resistatiix:; the latter of low-freezing dyiiamites. LVlrile nitroglycerin has a freezing point of around i-54" F., explosives contaiiiiiig it are expoae(1 rxrllent prolwty is due tri the ~mclosiireof the exjrlwive in i i S U l ! d lrlet,al cUIItaiileT. tit times to temperatures t l ~low ns -40" 1'. The iinproveCoal iiiitiiiig l ~ n beeii s une (IS tlie largest users of explosives ment in tliis respect is sucli that the irewing of nitroglpceriii siiict: tlie early yenrs (if the niiiet.eentli century, and the haswil explosives is no longcr a iniitter of co~icc:rn. The first successcjf cxpiosives iii gassy mines has long been recogniml. 13lack ful low-freezing dynamite, brought out in this country in 1907, 1)oivdur is paJ'tkUlady suitable for use in bringing dorun coal contained dissolved i i i t r d x h m x , and successive frcasinpbeeawe of its low velocity a i i d conseqitent slow heaving acpoint depressants included nitrated stigars, tetranitrodiglyoerin, and ethylene glycol dinitr:rte, the liitter being first wet1 timi. The Ieogth and duration of its flarne on explosion, lrowever, mike it unsafe in the presence of inflammable mine ga about IYZB. The improvement in tliis respect has beeri of 'l'hr pr~d~lenr of devising ari explosive satiiifactory for SIICIL great importance froni the point of v i m of both sdety i t d iiso liid beeti taken up actively by various European couiiconvenience. tries, t,liougli n u standard prileticc kind been attained. Tile A developmerit that may be considered almost entirely American has been the successful inaiiufactiire and use of first "aafety explosive" tnarkcted in the United States was iirolmbly Oliver's Flaineless Powder, a low-strength dynamite nonfreezing explosives coritaiiring solid nitrostarch as the t u whicll finely divided salts containing water of crystdlizaseiisitizing explosive base, and iio nitroglycerin UT other liquid explosive. t,ivn liad beeti added. The industry started an active research prograin on tlie subject in 1902, with initall:ition of This section would not lie complete without iricntiorr of tire tlie bcst European testing apparatus, and in i9Oi tried out valuable services rendered to the iiiiliistry by tile l3ure:w for x ~ m eof the most promising powders in the field. 111 the U T g i U r i Z W ~ ill I907 by tlie Safe Trtm~portationof Expliisi following year, the Technologic Branch of the U. S. Goohrgithe American Railway Associatioii. Jrider the directioii of cal Survey, under tlce leadership of Joseph A. lfolmes, began R. W. D u m , who 1123 been clijef inspector for pr:ict~icrrll.y its t,he testing for periiiissibility of various explosives sulmittcd tmtire existeuce tlie bureau liai been lriglil . successful it1 by American manufacturers. Seventeeri explosivcs were making safe tire traiispurtntim of exploiir gerous itrticles. jiiticed on tire permissible list prior t v >lay 15; 1909. I lie testing of explosives Tor periiiissibility wns sitbseqiiently Process Development for Ingredients trtmsferred to tlie I3rrreati of kIiiies. The trend in mil iiiitie l.'lie prop?ss in the explosives industrv has been Iareelv vxi,lnsives tiiriied soot1 to tlre : ~ i i i r i i o i i i Bperniissihle type, eondepencfent on the qudiity and a v a i l a b i l i t y of raw materiaLs aiid i n t e r m e diate products, a n d v e r y great advances liuve beeii brought about in the ltkst twenty-five years in tlic iiiiprovcment of methods for p r o d i t e i 11 g a n d treating these rrraterjals. Becau,su of tlic magnitude of the illdustry and its la~ge-~cale use of sucli materials, the improvemetits brought a b u u t h a v e h a d a prunounced effect on the clieniical industry generally. Sitroglycerin, tlie basie liigh.explosive materia!, is produced by thenitratioti of giyceritl l y means of a subst,antia!ly a n l i j d ~ u u smixture of siiliuric and nitric acids. A b o u t 1903, a inarkcd advance was made by tire iiitrotluction of an imirol"~l'lnrethod for hesteniiig t,Iie .epnrzLtion of n i t x glyceriii fr
