New Uses for Anthracite Coal
and Slate D. J . JOSES
AND
E. L. BULLER
The Hudson Coal Company, Scranton, Pa.
OF
OR over a century man has used anthracite as a fuel because of its low volatile matter and high carbon content, which made it slow-burning and smokeless. Very little study has been given to its use for anything other than combustion purposes. However, anthracite can be used as a filtering medium, for sintering iron ore, as a filler for asphalt, and in the form of sintered anthracite slate as a concrete aggregate. A good anthracite contains (on the dry basis) 6.0 per cent volatile matter, 85 per cent, fixed carbon, and 9.0 per cent ash. The volatile matter analyzes as follows (in per cent by volume) :
coz 01
H?
co
CH4
NZ
Northern Field Coal (Scranton) 1.6 0.8 86.2 0.4 6.6 4.4
Northern Field Slate (Scranton) 3.4 4.2 76.5 6.7 3.6 5.6
The volatile constituents of the slate, which is associated with the coal, show 1.8 per cent more carbon dioxide, 3.4 per cent more oxygen, 9.7 per cent less hydrogen, and 6.3 per cent more carbon monoxide than the coal. The ash from the anthr:tcite and from the slate in the Sorthern field analyzes as follows (in per cent by weight): Si02
.k1z03 Fez03
CaO 3190 Alkalies
C c d Aah 69.00 26.46 3.24 0.40 0.20 0.70
--
100.00
Slate Ash 61.60 32.17 3.70 0.40 0.20 1.93
100.00
Filter Medium During the decade 1890-1900, the State of Massachusetts conducted several experiments on water filtration, in which anthracite was used as the filter medium. This work was continued later a t State College, Pa., under the direction of the Anthracite Institute Research Division, and subsequently several filter beds throughout the East, Middlewest, and Southwest were equipped with anthracite instead of sand. In water purification, the finer sizes of anthracite are usually used. The main bed is made from coal passing a a/3,-inch round-mesh screen. Exact specifications are prescribed, so that the coal shipped as Anthrafilt has a definite effective size and uniformity coefficient. The coal must contain a minimum of noncombustible material because, if the ash increases beyond a maximum of 10 per cent, the specific gravity of the entire mass is changed and 953
the efficiency of the filter bed during backwash periods is cut down materially. Also, as the noncombustible material increases, the carbon content of the bed decreases and the number of angular particles is reduced; this destroys efficiency because the angularity of the particles undoubtedly adds a great deal to the effectiveness of anthracite as a filter medium. The specific gravity of the coal for this use is important. Anthracite with a specific gravity of 1.50 is the most desirable. When anthracite with a low specific gravity is used, the necessary backwash head is reduced and more economical plant operation is possible. The specific gravity of the coal used for filtration :ilso influences attrition losses because, as the specific gravity of the coal increases, the brittleness also increases, and when the particles are bumped together during backwash periods, the high-gravity coal produces more fines than low-gravity coal. Since all material through 40 mesh is eventually washed from the filter bed, high-gravity coal results in high bed losses. Anthrafilt has some absorbent qualities; for example, it will remove certain odors, certain dyes, and some tastes, but the qualities of absorption are not great enough to be of any commercial value. Water, containing one part per million of chlorine, can be reduced to 0.3 p p. m. when passed through a bed of a n t h r a c i t e 34 i n c h e s in depth. At, the end of 6 90 w e e k s , however, the bed ceases to 80 reduce the chlorine below 0.3 p. p. m. and a t present no 70 means of reactivating the bed is 60 known. Rater t r e a t e d 50 with lime tends to cement a sand bed into a solid mass. 40 This difficulty is absent in anthra30 cite beds. In the filtration of h o t alkali maters for 20 i n d u s t r i a l uses, their solvent effect IO must be considered. Experi0 ments show that hot s o l u t i o n s of COAL SLATE sodium hydroxide %DRY VOLATILE 6.6 6.3 d o n o t affect or AN.4LYSIS BY VOLUhlE OF VOLATILE dissolve the carbon &TATTER in Anthrafilt.
Sintering of Iron Ore At the Lyon Mountain plant of the Chateaugay Ore and Iron Company, anthracite passing a 3/&nch round-mesh screen is used in the sintering of a magnetite ore. This coal will contain a maximum of 10 per cent ash. It is mixed with the ore on a Dwight-Lloyd sintering machine, where the magnetite is partially reduced by the carbon and the ore is sintered so that the finished product is easily handled in the blast furnace. The resultant pig iron analyzes approximately (in per cent by weight) : Carbon Manganese Phosphorus
3.500 0.040 0.025
Sulfur Silicon
0,030
2.680
INDUSTRIAL AND ENGINEERING CHEMISTRY
954
The wrought iron from this process compares favorably with any wrought iron produced today.
Anthracite and Slate as Fillers for Asphalt Because of the abundance of anthracite slate and the low cost a t which this material can be marketed, much work has been conducted on its use as a filler for asphalt. The slate analyzes as follows (in per cent by weight): Si02 Alios FezOa
20.18 10.65
1.21
CaO
MgO Alkalies
VOL. 27, NO. 8
This may be due to the permeability of the powdered coal to actinic light. A good grade of mineral filler will increase the life of the asphalt when exposed in the Weatherometer approximately 225 per cent; pulverized anthracite effects an increase of only 30 per cent. Coal has been used successfully as a filler for tar and asphalt in European paving.
Sintered Anthracite Slate as Concrete Aggregate
0.14 0.07 0.63
When ground to $40 mesh, the slate has a flat laminated structure. However, as the grinding continues to -200 mesh the flat particles disappear. The value of the slate as an asphalt filler is due to the overlapping of these flat particles which prevents movement within the asphalt. The sulfur content of some slates is also another factor hindering its use as an asphalt filler because sulfur will decrease the life of the asphalt. When the anthracite, ground to 315 Tyler mesh, was used as a filler in bituminous test bricks, weathering was greater than in bricks containing more standard fillers. Although the coal is easily wetted with bitumen and imparts the anticipated mechanical stability to the bituminous compound, it is inferior to other mineral fillers in weather resistance.
The anthracite industry of Pennsylvania has millions of tons of refuse that could be used as an excellent concrete aggregate after sintering. Raw anthracite slate was crushed to -8 mesh and then sintered on a Dwight-Lloyd sintering machine carrying a 5inch bed of slate. The sintering time was 35 minutes because it was necessary to burn out practically all of the carbon before sintering occurred. The finished product was a hard, structurally strong, sintered mass that had to be crushed to whatever aggregate size was necessary. When prepared, however, this material was light in weight and very strong. The total weight of the concrete can be reduced by using this material, thus reducing the weight of the structural steel necessary in high structures. RECEIVED April 19,1935.
[ENDOF SY~~POSIKJM] .tC#
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HEN hydrocarbon gases are dissolved in liquid hydrocarbons, marked decreases in density, surface tension, and viscosity result. Such changes have an important bearing upon the processes involved in the production of crude petroleum. It is therefore of interest to obtain sufficient experimental information to permit the prediction of such changes as functions of the properties of original oil and gas involved, of temperature, and of equilibrium pressure. The present paper deals with results of a study of viscosity changes resulting from solution of methane and of propane in an oil known as crystal oil, under conditions of equilibrium temperature and pressure commonly met in petroleum production practice.
Materials and Apparatus The crystal oil used in this study was a water-white refined oil produced from a western crude stock. It was chosen as a suitable material on account of its stability, low vapor pressure, high viscosity, and narrow range of properties of its constituent hydrocarbons. The analysis and physical properties of this oil have been described in detail by Sage and co-workers (2). The methane supply was prepared from natural gas by methods previously outlined (2). Possible impurities consisted of nitrogen and similar inert gases to the extent of less than 0.2 per cent and of less than 0.02 per cent of hydrocarbons of higher molecular weight. The propane was of a chemically pure grade giving no evidence of impurities by fractionation analysis or by variation of equilibrium pressure during gradual condensation a t constant temperature ( 5 ) . All three of these materials have also been utilized in connection with phase-equilibrium studies of hydrocarbon systems (3,4,6) and it is therefore possible to obtain information concerning additional properties to those discussed in this paper. The viscometer used for the measurement of viscosity of saturated solutions was that described by Sage (I). It con-
Viscositv of d
Hydrocarbon Solutions Solutions of Methane and Propane in Crystal Oil B. H. SAGE, J. E. SHERBORNE,
AND W. N. LACEY
California Institute of Technology, Pasadena, Calif.
sisted in principle of a ball rolling down an inclined tube filled with the saturated solution under controlled conditions of saturation pressure and temperature. Since the densities of these saturated solutions were known from studies in other apparatus (9, d ) , the density balance formerly described as part of the viscometer circuit was eliminated, thus decreasing the amount of materials needed to fill the apparatus. The density measurements referred to furnish more accurate re-
