December, 1925
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1293
AMERICAN CHEMICAL INDUSTRIES The Dorr Company stead of making more profit from the new mill, it was found of the Dorr Company’s organization and the variety of the that it was actually running a t a loss. The whole trouble was applications of the Dorr machinery today, he would have poor classification, and after a good deal of experiment Mr. been regarded as a dreamer. From a small beginning, with one Dorr devised a plan of running the ore into a shallow tank with sloping bottom, raking out the sands, and overflowing the slime. machine in a mill in the Black Hills, South Dakota, the business With care this gave the leaching product necessary to secure of the Dorr Company has grown continuously and steadily until now there are over eight thousand machines in operation dealing satisfactory results. Improved construction resulted in the birth of the Dorr Classifier. with widely different materials varying from gold, platinum, and The Classifier was designed to meet diamonds to more common substances a special condition a t a special mill, and such as coal, iron ore, and building a t first mill men doubted if it had more sand. The activities of the Dorr Comthan a local application. A visitor to pany have taken its engineers to every the mill, however, seeing the Classifier continent and practically every country. work was reminded of a somewhat Its machines are in use from Korea to similar problem in New Mexico and Zululand and from the North Cape, asked Mr. Dorr if he would build a ClasNorway, to Patagonia. sifier suitable for his conditions. To proThe founder, J. V. N. Dorr, graduated tect the idea, Mr. Dorr took out his as BSc., from Rutgers College, and had first patent and the Classifier was sent a good grounding in scientific investigat o Kew Mexico. The mill where it was tion work, spending two years in the installed was a t that time barely maklaboratories of Thomas A. Edison, ing ends meet. After the installation Orange, N. J. Later, he supplemented it commenced to make profits which this scientific training by practical plant enabled its owners to sell out for one experience in the Black Hills, South million dollars. Dakota, first as a chemist in a pyritic smelter there and later as chemist and Owing to the success of the Dorr mill foreman in a cyanide plant a t Deadwood. in the Black Hills, Mr. Dorr was asked While working in the cyanide plant he to remodel the Mogul Mining Combecame acquainted and entered into pany’s mill at Pluma, S. D. The Dorr partnership with Lundberg and Wilson. Classifiers were installed in this mill, but John Lundberg was a practical miner an additional problem presented itself and had made some success in operating -the thickening of the Classifier overflow. Intermittent thickening gave irleases on gold-mining properties. The J. V. N. Dorr regular results, and again after a great partners, realizing that if they could treat deal of experimental work Mr. Dorr intheir own ore they would have a better stalled the first Dorr Thickener. This chance of success, acauired the lease on a small antiquated mill operated by Mr. Dorr and treated the machine, like the Classifier, was received with considerable doubt ores mined by the co-partners. by mill men as to its efficiency. However, these doubts were soon From the first their operations were successful, but the mill dispelled by the continued successful operation of the machines was located some distance from the mining property and the and inquiries commenced to come in from various mining comhaulage of the ore involved a freight charge of one dollar per ton. panies that were having dBculties. Also, the expenses of running a badly designed mill and the rent To meet this demand and to arrange for manufacturing, the for it were additional drawbacks. This decided the partners Dorr Cyanide Machinery Company was formed and, without to erect a mill of their own adjacent to the property. The advertising, a small but increasing business in the machines technical work in mill design was in Mr. Dorr’s hands and the was developed. Mexico was experiencing a mining boom and new plant included a number of novel points. Crushing was a prominent engineer there asked for an agency for the Dorr done in cyanide solution, sands and slime were treated sepa- machinery. This was granted and Mexican business commenced rately, the sand by leaching and the slime by a Moore filter. to come in. Without any advertising, sales increased, one maDaring greatly, the adventurers not only staked all their own chine operating successfully selling others. capital on the success of the mill but pledged their credit to the As a natural sequence to the success of the Dorr Thickener, maximum. As an interesting sidelight on the relations between Countercurrent Decantation commenced to be installed. This the operators and their workers, we may state that the Miners’ proved to be a very decided forward step in the cyanide process Union advanced the sum necessary to complete the erection and countercurrent decantation, or C.C.D., plants were erected of the mill. in the States, Mexico, and Canada, followed later by the applicaThe ore being treated contained an unexpectedly large protion of this process of slime treatment practically all over the portion of slime and the double-cone classifiers originally in- world. Representatives of the Dorr Company visited Europe, stalled failed to give a sand product that was readily leachable. Australia, India, and South Africa, and the machines had a This prevented the mill from running t o its designed capacity world-wide application. Although originally designed for the and the tailings contained more gold than was expected. In- cyanide treatment of gold and silver ores, the Classifiers and
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F, twelve years ago, any one had foretold the magnitude
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 17, No. 12
Two-Hundred Foot Dorr Thickener a t Inspiration Copper C o . , Miami, A r b .
C. C. D. Installation a t G u a n a j u e t o Reduction a n d Mines C o . , Mexico
Thickeners became standard machines in practically all oretreatment plants. The Dorr Agitator was designed to meet a difficulty found in C.C.D. plants. Mechanical agitators take high power, and pulp in air agitators settles out and necessitates frequent cleaning. Mr. Dorr designed a machine embodying the advantages of the Thickener, where a mechanism sweeps the bottom of a tank and keeps the pulp from building up. A small air lift in the center transfers the pulp swept to the center up to the top, where it is distributed over the surface of the charge. This was a decided advance in agitators. Running cost was considerably reduced and, owing to .the shape of the tank, installation costs were less than agitators of the air type. Naturally, modifications and improvements have taken place in all machines mentioned. The present “D” type Classifier is a very different machine from its progenitor in the Dorr mill in the Black Hills. An open and connected type Tray Thickener has increased the capacity of the ordinary type thickener many times in proportion to the floor space.
Thickener, a special diaphragm pump was designed, after experiment with orifice discharge, air lifts, and other types of pumps. The Dorr Washer is really a combination of the Classifier and a trommel, and was designed to free ores from clay and make a three-product separation, one of which was usually waste. One of the latest fields of Dorr activity is sanitary engineering. The Dorr Clarifier has become a standard machine for handling domestic sewage and industrial waste waters, and consists of a square concrete tank in which a specially designed mechanism sweeps the settled solids from all parts of the tank t o the center, thus enabling full advantage to be taken of the whole area and cheap construction costs. The Dorrco Screen was developed t o eliminate the coarser suspended particles in sewage and trade wastes so as to prevent overloading the Thickener with coarse material. This has also met with immediate success and a number of very large installations are operating and being erected. When it was found that the application of Dorr machines was going into a large number of industries it was believed that
Dorr Agitators a t Oklahoma Portland C e m e n t C o . , Ada, Okla.
Dorr Save-All, Watab Paper C o . , Sartell, Minn.
The Bowl Classifier has enabled large tonnages of pulp t o be handled in one machine and a close separation made at fine mesh. The Dorr Cane Juice Clarifier as used in cane sugar work is the natural evolution of the Tray Thickener and was designed to meet the special requirements of the process. The Dorr Save-All, now in common use in paper mills, is also a modification of the Dorr Tray Thickener, following special study of the requirements of the case. To control the underflow from the
the name of the company should be changed and the Dorr Company succeeded the Dorr Cyanide Machinery Company. Taking advantage of this reorganization, Mr. Dorr associated with himself and the company a number of the engineers who had helped him to develop the machines, and as they included mechanical, chemical, metallurgical, and sanitary engineers, the basis of the company was both broadened and strengthened. One of the most important factors in the success of the Dorr
