THE COLLIERY GUARDIAN

AND

JOURNAL OF THE COAL AND IRON TRADES.

Vol. CXII.	FRIDAY, NOVEMBER 3, 1916.	No. 2914.

A New Belgian Coal Washer.

The coal washing question has become a matter of
prime importance in this country, because many of the
best and purest coal seams having now been worked
out, a number of collieries have had to work seams with
a higher ash content. On the other hand, a greatly
increased demand has arisen, especially for making coke
and briquettes, for clean coal slack with not more than
5 to 8 per cent, of ash.

There are already a number of well-known washery
systems, which deal capably with the washing of peas

tant position in the ranks of coal washing appliances.
At the Lens Collieries, in particular, it has replaced the
felspar box system for washing 0-jin. slack, without
previous separation of dust.

The Rheolaveur is really an auxiliary to the old
apparatus for washing ores with running water on a
sloping trough provided with transverse grooves. That
apparatus (fig. 1) washed the schists into the grooves r,
but although its action was improved by the provision
of transverse ledges b, below the grooves, it was aban-

in fig. 3, two or more Rhdolaveurs can be combined to
serve contiguous grooves.

Theory of Action.

In classification by density with this device, the
following factors have to be considered :—(1) The effect
of the flow of water on the trough; (2) that of the upward
current from the Rheolaveur; and (3) the effect pro-
duced by the upward current on the trough current.

Taking these in the order given, if a stream of water
is discharged on to the upper end of a trough or table A
(fig. 1), of suitable size and slope, the combined effect
of gravitation and frictional resistance soon reduces the
flow to a uniform velocity v. Coal placed on the trough

Fig. 1.—Typical Trough Washer.

Unwashed coal

Schiet

Washed coal

Unwashed coal

Washed coal

Fig. 3.—Combined Rheolaveurs.

Unwashed coal
20*50 L per hour

Schist (73°/#)

Second washer

Schist (66 ” o)

3



Mixed prod.

A

XtZZZ*
R

Fig. 2.—Typical Rheolaveur.

Washed coal

Unwashed coal
50-80 1. per hour

Schist (7 1 °/o)

Washed coal

Second washer
Schist (60° o)

8

Fig. 4s.—Multiple Trough Arrangement.

and nuts, but are costly to apply to the washing of
slack in coking and briquetting plants. For this reason
it is particularly interesting to note that, during the
past few years, French and Belgian collieries have
reverted to the older, simpler, and cheaper type of
trough washer, which has still many adherents in this
country, the efficiency of the washers having been
improved by modifying the arrangement of the ascend-
ing currents so as to ensure better classification.

doned, in consequence of the superior results obtained
with jigs. The principle has now been revived by pro-
viding, underneath the grooves, a Rheolaveur, which
produces an upward flow of water in the latter, and at
the same time allows the schists to drop through unin-
terruptedly.

The typical Rheolaveur is a pyramidal cast iron box
(fig. 2), one end of which fits under the washing trough,
whilst the other has an outlet for the removed dross.

at A will then be subjected to three forces—<f> being
taken to express the diameter of the pieces of coal; d,
the density; and K, K', K,, K',, correctional coefficients
depending on the shape of the pieces and their influence
on each other. The friction F on the bottom of the
trough depends on the weight </>3 (d — 1) of the coal in
water and on its friction against the bottom of the
trough, or rather against the layer of schist covering the
latter: F = K/<£3(d—1). The secondf actor is the propul-

■

■
k.

Fig. 5.—Simple Rheolaveur.

• H

h»i-

sf

to

Fig. 6.—Multiple-groove Rheolaveur with Single Discharge.

The newest washer of this kind is that known as the
“ Rheolaveur,” the following description of which has
been given by M. E. Dinoire, chief engineer of the
Lens Collieries, in the Bulletin de la Societe de I’lndus-
trie Minerale, and we understand that a washer of the
same type is shortly to be erected in England.

The Rheolaveur.

This coal washer, which is the invention of Messrs.
Habets and France, has been employed for some time
past in Belgian and French collieries, and, from the
results obtained, seems calculated to occupy an impor-

The box is divided by a vertical partition into two com-
partments, one (a) communicating with the groove in
the trough, and the other (b) serving for the admission of
water from the pipe t. The incoming stream of water
divides into two branches, one of which ascends
through the groove, and the other washes the dross out
through the bottom outlet. A head of 20 ft. of water
gives sufficient pressure, and the supply can be regu-
lated by the cock R.

One of these Rheolaveurs is mounted underneath
each of the grooves in the washing trough; or, as shown

sive effect 1 of the current of water, a function of the
superficial area of the lumps of coal, </>" and the square
of the velocity of the current : 1=K' <f>- v“. Thirdly,
there is the very small, and •negligible, component of
gravity due to the low angle of inclination of the trough.

The equation K/ d? (d— 1) = K' </>2 v: gives the
current velocity at which the products (i.e., coal and
“ equivalent ” schist) characterised by the factor
(d— 1) will remain in equilibrium.

In this way the treatment with running water gives
a classification of the products by equivalence. In