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By S. K. Kawatra

In order to take full advantage of the use of manipulatable variables to effectively control the response of coal flotation circuits to disturbances and to optimize circuit performance, the effects of each manipulatable variable must be understood with respect to the mechanisms responsible for particle recovery. This paper pays particular attention to the critical role of the froth phase and its effect on circuit behavior and control and emphasizes that in order to optimize the separation of coal from gangue by flotation it is necessary to consider particle behavior in both the pulp and in the froth while developing a control strategy. Data obtained from the extensive sampling of the flotation circuits in two coal preparation plants are used to illustrate this concept; by showing first the effects of reagent addition levels on the mechanisms responsible for particle recovery and second how this information can be used for control strategy development.

Jan 1, 1984

By C. A. Mitke

(Butte Meeting, August, 1913.) 1. Character of Gases which Caused Helmets to Get Out of Order. DURING September, 1911, the fire area, in the Lowell mine continually increased. and gases resulting from the fire came through the upcast shaft. These gases contained such a large percentage of sulphur dioxide that the men were unable to go up and down on cages, and, within a comparatively short time, repairs in the shaft were found to be necessary. Since the fire was in sulphide ores and extended into certain timbered sections, the gases contained varying amounts of SO2, CO2, and perhaps, at times, CO. The temperature in the shaft was generally about 97°, and the relative humidity from 97 to 99.5 per cent. The corrosive action of the fumes became apparent when the cables had to be changed more often than usual, the heads of lag screws in the guides of the shaft disappeared, and the cages needed frequent repairs. It also became necessary to repair two compartments of the shaft by putting in 150 ft. of new guides between the 600 and 800 levels and lag screws in nearly all the old guides from the surface to the 800 level. 2 Ordinary Methods of Testing Helmets which were Unsatisfactory. These conditions required all work to be done by men wearing oxygen helmets. The Draeger type was tried, and was used until all repairs were completed. At first the helmets were tested for air circulation and air tightness .and the injector was tested by water gauge according to the methods recommended by the Draeger Oxygen Apparatus Co. Six arrangements, covering these different tests, are illustrated in the catalogue and circulars of the company.

Jan 7, 1913

Data about production are very meager. In this county from the earliest days until after the Civil War, the amount of coal used locally greatly exceeded that shipped on account of the iron produced; for many years the furnaces used raw coal for melting the ore. In 1846 it was stated that in this county one ton of iron required three tons of iron ore and three tons of local coal used raw.1 In 1864, eleven furnaces in Pennsylvania using 102,230 tons of raw coal produced 44,671 tons of iron, or 2.3 tons raw coal per ton of pig iron .2 This was probably as good a record as was made, as nearly all furnaces changed to coke some years later. Neither of these figures include the coal used for steam and other purposes around an iron plant. The Beaver and Erie Canal was opened in 1845 and the shipments shown from then to 1865, inclusive, are of coal received by the canal at Erie, and do not include any used at local points along the canal. From the completion of the Erie and Pittsburgh Railroad in 1864 the tonnage shipped by canal decreased. rapidly, and, while the canal shipments after 1864 are supposed to be those received at Erie by canal only, they may include some rail tonnages. Tonnages on Erie and Pittsburgh Railroad may, and probably do, include some used locally; those on the Jamestown & Franklin Railroad do not. It is likely that both canal and Erie and Pittsburgh Railroad figures include some coal originating in Lawrence County, and possibly a little from Beaver County. These tonnages are not duplicated in the data for either of the other counties. Not all of the railroad reports can be found now.

Jan 1, 1942

By NA NA

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By H. R. Ogden, E. S. Bartlett, A. G. Imgram

THE tensile and notch tensile ductile-to-brittle transition characteristics of several refractory metals and alloys have been well documented.1-3 Electron-beam melted tantalum and columbium have been shown to retain excellent ductility at very low temperatures. Some indications of brittle behavior (low ductility and cleavage fracture) were observed with columbium tested at -253oC, but no similar effects were noticed with tantalum. Increasing the interstitial oxygen content in these two materials resulted in the detection of indications of brittle behavior at higher temperatures, although good ductility was retained in both bases at -196°C when they contained about 1 at. pet 0. Detailed descriptions of the impact transition behavior of these two materials at various purity levels have not been available. This technical note describes the effect of interstitial oxygen on the impact properties of wrought, fibered tantalum and columbium and compares the transition behavior to the previously determined tensile transition characteristics. Tantalum and columbium impact specimens with three different interstitial oxygen levels indicated in Table I were tested at temperatures ranging from -196o to 300°C. Oxygen additions were made to 1/2-in.-diam bars of electron-beam melted material in a Seiverts Apparatus. The oxygenated bars were then homogenization-annealed to obtain uniform cross-section hardnesses and swaged to

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