The methods of working coal seams have been gradually evolved and
progressively improved or modified as knowledge and experience were gained
and power machines became available. Over the years, a very large number
of methods of mining coal have been developed to suit the seam and local
conditions, and they may be split, broadly, into longwall, and pillar
methods of working. See also:stowing method
Crude oil obtained by the destructive distillation of bituminous coal.
A small settlement near a coal mine.
An instrument to assess the strength of a coal seam, its relative
workability, and the influence of roof pressure. It consists of a steel
rod of sectional area 1/4 in2 (1.6 cm2 ) that is pushed
into the coal, normal to the coal face, under the action of a light
hydraulic ram. The ram is braced against lightweight props erected at the
face. When in position, the penetrometer gives a graph of load against
penetration at a particular point. Readings are taken at a number of
points laterally and vertically along the face, and these can be
correlated with the performance of plow-type machines. Thus, the probable
performance of a machine in a seam can be estimated without the need for
costly trials. Syn:penetrometer
Eng. A place where coal is dug. A coal mine.
A type of continuous coaling machine developed in Germany esp. for
longwall mining. It consists of a heavy steel plow with cutting knives,
with power equipment to drag it back and forth across a coal face. A
parallel conveyor receives and carries away the coal as the planer digs it
from the face.
A fossil plant found in coalbeds or contributing its substance to the
formation of coalbeds. Any plant species, the residue of which has entered
into the composition of coal under natural geological conditions.
Fay
a. A cutter loader with knives to slice the coal off the face.
Nelson
b. This device carries steel blades that shear or plane off coal to a
limited depth and plow it onto the face conveyor. The plow is hauled
backward and forward along the coal face by steel ropes or chains operated
by winches in the gate roads, and it planes off a thickness of 11.8 in (30
cm) to a height one-third to one-half the seam thickness each time. The
coal is conveyed along the face by a double-chain conveyor with
double-ended drive; the conveyor sections are articulated to allow for
bends in its tracks and are moved bodily forward at each passage of the
plow, either by compressed-air jacks or by means of a torpedo or trailer
attached by rope to the plow and an auxiliary drum on the winches. Its
uses are limited to softer coal seams, or to suitably prepared coal. Also
called kohlenhobel. Mason
a. A structure, bunker, or bin for the storage of coal. Fay
b. An arrangement of bins to load trucks or railcars by gravity.
The various physical and mechanical processes in which raw coal is
dedusted, graded, and treated by dry methods (rarely) or water methods,
using dense-media separation (sink-float), jigs, tables, and flotation.
The objective is the removal of free dirt, sulfur, and other undesirable
constituents.
a. A facility where raw coal is sized and prepared for loadout. In the
United States, plant capacities vary from 500 to 2,500 st/h (454 to 2,268
t/h). See also:cleaning; dense-medium washer; gravity concentration;
screen; washery. Nelson
b. A facility or collection of facilities that include associated support
facilities and consist of, but are not limited to: loading facilities;
storage and stockpile facilities; sheds, shops, and other buildings;
settling basins and impoundments, coal processing and other waste disposal
areas; roads, railroads, and other transport facilities. Exempted from the
meaning of coal-preparation plant is an operation that a) loads coal; b)
does not separate coal from its impurities; and c) is not located at or
near the mine site.
The process adopted for cleaning and sizing coal for the market.
Specialists select the best process for any particular run-of-mine coal.
Many conflicting factors must be weighed. The cost of a detailed
investigation is well repaid in higher recoveries, in flexibility, and in
ease of operation and maintenance. Nelson
On mechanized longwall faces, the shift during which coal-cutting, boring,
and shot-firing operations are performed. Mason
Earth materials that are combustible, physically unstable, or acid- or
toxic-forming, which are wasted or otherwise separated from product coal.
They are slurried or otherwise transported from coal-preparation plants,
after physical or chemical processing, cleaning, or concentrating of coal.
Classification according to degree of metamorphism or progressive
alteration, in the natural series from lignite to anthracite; higher rank
coal is classified according to fixed carbon on a dry basis; lower rank
coal according to Btus on a moist basis. Bennett
Very impure coal containing much argillaceous material, fusain, etc.
AGI
a. Scot. A working face in stope-and-room workings. Fay
b. The open area between pillars where the coal has been removed.
The standard method used by the U.S. Bureau of Mines samplers is as
follows: A space of 5 ft (1.52 m) in width should be cleared of dirt and
powder from top to bottom of the seam being sampled. Down the center of
this cleared space, a zone 1 ft (0.3 m) wide is cut to a depth of at least
1 in (2.54 cm) in order to get perfectly clean coal. A cut is then made up
the center of this zone to a depth of 2 in (5.2 cm) and a width of 6 in
(15.2 cm); or, if the coal is soft, to a depth of 3 in (7.6 cm) and a
width of 4 in (10.2 cm). Approx. 5 to 6 lb (2.3 to 2.7 kg) of coal will be
obtained for each foot (0.3 m) of thickness of the seam. This should
include all bony coal included in the mining operation and exclude all
slate or partings, which are thrown out during the operation. The sample
obtained should be collected on a waterproof cloth 6 ft by 7 ft (1.83 m by
2.13 m) and then screened, the lumps being broken in a mortar, and all
passed through a 1/2-in (12.7-mm) screen. Any impurities, such as slate or
pyrite, are crushed to 1/4 in (6.4 mm) or finer and thoroughly mixed with
the coal. The coarser materials should be evenly distributed, the sample
being then quartered, remixed, and requartered. When the mixing is
complete, the sample should be placed in a can with the capacity of 3 lb
(1.35 kg) and the top screwed on and sealed with adhesive tape. The can
should be labeled with the name of the collector, the location, the date,
and any other information necessary for the analysis.
See also:channel sample; sampling. Kentucky
A bed or stratum of coal. Craigie
The identification of a coal seam; the linking up or matching of a seam
exposed in different parts of a mine or coalfield. A coal seam may be
correlated by lithology, by fossils, by chemical composition, or by its
spore content. Coal-seam correlation is very important in exploration and
in penetrating faults. See also:correlation
An obsolete, nucleonic coal-sensing instrument that can measure the
thickness of coal left on the roof or floor of a seam after the passage of
a mining machine. The principle used is the measurement of the density of
the strata underlying the machine by a gamma-ray backscattering unit.
Gamma rays from a radioactive source are scattered in all directions by
the atomic particles in the coal and rock. The amount of scattered
radiation eventually reaching the Geiger counter is, approx., inversely
proportional to the density of the scattering medium; i.e., more radiation
will come back from coal than from rock. Thus, as the amount of coal
between the source and the underlying rock changes, so the amount reaching
the Geiger counter and the counting unit (the ratemeter) will change, and
consequently the output of the meter can be calibrated in terms of the
thickness of the floor coal. This instrument has been replaced by a
natural-gamma coal thickness sensor. See also:manless face
Nelson