chapter19.txt

CHAPTER XIX







MAGNETIC ORE MILLING WORK







DURING the Hudson-Fulton celebration of October,



1909, Burgomaster Van Leeuwen, of Amsterdam,



member of the delegation sent officially from



Holland to escort the Half Moon and participate in



the functions of the anniversary, paid a visit to the



Edison laboratory at Orange to see the inventor, who



may be regarded as pre-eminent among those of



Dutch descent in this country. Found, as usual, hard



at work--this time on his cement house, of which he



showed the iron molds--Edison took occasion to remark



that if he had achieved anything worth while,



it was due to the obstinacy and pertinacity he had



inherited from his forefathers. To which it may be



added that not less equally have the nature of



inheritance and the quality of atavism been exhibited



in his extraordinary predilection for the miller's art.



While those Batavian ancestors on the low shores of



the Zuyder Zee devoted their energies to grinding grain,



he has been not less assiduous than they in reducing



the rocks of the earth itself to flour.







Although this phase of Mr. Edison's diverse activities



is not as generally known to the world as many



others of a more popular character, the milling of



low-grade auriferous ores and the magnetic separation



of iron ores have been subjects of engrossing



interest and study to him for many years. Indeed,



his comparatively unknown enterprise of separating



magnetically and putting into commercial form low-



grade iron ore, as carried on at Edison, New Jersey,



proved to be the most colossal experiment that he



has ever made.







If a person qualified to judge were asked to answer



categorically as to whether or not that enterprise



was a failure, he could truthfully answer both yes



and no. Yes, in that circumstances over which Mr.



Edison had no control compelled the shutting down



of the plant at the very moment of success; and no,



in that the mechanically successful and commercially



practical results obtained, after the exercise of



stupendous efforts and the expenditure of a fortune, are



so conclusive that they must inevitably be the reliance



of many future iron-masters. In other words, Mr.



Edison was at least a quarter of a century ahead of



the times in the work now to be considered.







Before proceeding to a specific description of this



remarkable enterprise, however, let us glance at an



early experiment in separating magnetic iron sands



on the Atlantic sea-shore: "Some years ago I heard



one day that down at Quogue, Long Island, there



were immense deposits of black magnetic sand. This



would be very valuable if the iron could be separated



from the sand. So I went down to Quogue with one



of my assistants and saw there for miles large beds



of black sand on the beach in layers from one to six



inches thick--hundreds of thousands of tons. My



first thought was that it would be a very easy matter



to concentrate this, and I found I could sell the stuff



at a good price. I put up a small plant, but just as



I got it started a tremendous storm came up, and



every bit of that black sand went out to sea. During



the twenty-eight years that have intervened it has



never come back." This incident was really the prelude



to the development set forth in this chapter.







In the early eighties Edison became familiar with



the fact that the Eastern steel trade was suffering



a disastrous change, and that business was slowly



drifting westward, chiefly by reason of the discovery



and opening up of enormous deposits of high-grade



iron ore in the upper peninsula of Michigan. This



ore could be excavated very cheaply by means of



improved mining facilities, and transported at low



cost to lake ports. Hence the iron and steel mills



east of the Alleghanies--compelled to rely on limited



local deposits of Bessemer ore, and upon foreign ores



which were constantly rising in value--began to sustain



a serious competition with Western mills, even



in Eastern markets.







Long before this situation arose, it had been recognized



by Eastern iron-masters that sooner or later the



deposits of high-grade ore would be exhausted, and,



in consequence, there would ensue a compelling necessity



to fall back on the low-grade magnetic ores.



For many years it had been a much-discussed question



how to make these ores available for transporta-



tion to distant furnaces. To pay railroad charges on



ores carrying perhaps 80 to 90 per cent. of useless



material would be prohibitive. Hence the elimination



of the worthless "gangue" by concentration of



the iron particles associated with it, seemed to be



the only solution of the problem.







Many attempts had been made in by-gone days to



concentrate the iron in such ores by water processes,



but with only a partial degree of success. The



impossibility of obtaining a uniform concentrate was a



most serious objection, had there not indeed been



other difficulties which rendered this method commercially



impracticable. It is quite natural, therefore,



that the idea of magnetic separation should have



occurred to many inventors. Thus we find numerous



instances throughout the last century of experiments



along this line; and particularly in the last



forty or fifty years, during which various attempts



have been made by others than Edison to perfect



magnetic separation and bring it up to something



like commercial practice. At the time he took up



the matter, however, no one seems to have realized



the full meaning of the tremendous problems involved.







From 1880 to 1885, while still very busy in the



development of his electric-light system, Edison found



opportunity to plan crushing and separating machinery.



His first patent on the subject was applied



for and issued early in 1880. He decided, after



mature deliberation, that the magnetic separation of



low-grade ores on a colossal scale at a low cost was



the only practical way of supplying the furnaceman



with a high quality of iron ore. It was his opinion



that it was cheaper to quarry and concentrate lean



ore in a big way than to attempt to mine, under adverse



circumstances, limited bodies of high-grade ore.



He appreciated fully the serious nature of the gigantic



questions involved; and his plans were laid



with a view to exercising the utmost economy in the



design and operation of the plant in which he



contemplated the automatic handling of many thousands



of tons of material daily. It may be stated as broadly



true that Edison engineered to handle immense



masses of stuff automatically, while his predecessors



aimed chiefly at close separation.







Reduced to its barest, crudest terms, the proposition



of magnetic separation is simplicity itself. A



piece of the ore (magnetite) may be reduced to powder



and the ore particles separated therefrom by the



help of a simple hand magnet. To elucidate the basic



principle of Edison's method, let the crushed ore fall



in a thin stream past such a magnet. The magnetic



particles are attracted out of the straight line of the



falling stream, and being heavy, gravitate inwardly



and fall to one side of a partition placed below. The



non-magnetic gangue descends in a straight line to



the other side of the partition. Thus a complete



separation is effected.







Simple though the principle appears, it was in its



application to vast masses of material and in the



solving of great engineering problems connected



therewith that Edison's originality made itself manifest



in the concentrating works that he established



in New Jersey, early in the nineties. Not only did he



develop thoroughly the refining of the crushed ore, so



that after it had passed the four hundred and eighty



magnets in the mill, the concentrates came out finally



containing 91 to 93 per cent. of iron oxide, but he



also devised collateral machinery, methods and processes



all fundamental in their nature. These are



too numerous to specify in detail, as they extended



throughout the various ramifications of the plant, but



the principal ones are worthy of mention, such as:







          The giant rolls (for crushing).



          Intermediate rolls.



          Three-high rolls.



          Giant cranes (215 feet long span).



          Vertical dryer.



          Belt conveyors.



          Air separation.



          Mechanical separation of phosphorus.



          Briquetting.











That Mr. Edison's work was appreciated at the



time is made evident by the following extract from



an article describing the Edison plant, published in



The Iron Age of October 28, 1897; in which, after



mentioning his struggle with adverse conditions, it



says: "There is very little that is showy, from the



popular point of view, in the gigantic work which



Mr. Edison has done during these years, but to those



who are capable of grasping the difficulties encountered,



Mr. Edison appears in the new light of a brilliant



constructing engineer grappling with technical



and commercial problems of the highest order. His



genius as an inventor is revealed in many details of



the great concentrating plant.... But to our mind,



originality of the highest type as a constructor and



designer appe...