The condenso-purifier shown in the accompanying cut operates as
follows: Water is caused to flow over a metallic plate perforated with
innumerable holes of from one to three millimeters in diameter, and
then, under this disk, which is exactly horizontal, a current of gas is
introduced. Under these circumstances the liquid does not traverse the
holes in the plate, but is supported by the gas coming in an opposite
direction. Provided that the gas has sufficient pressure, it bubbles up
through the water and becomes so much the more divided in proportion as
the holes are smaller and more numerous.
The gas is washed by traversing the liquid, and freed from the tar and
coal-dust carried along with it; while, at the same time, the ammonia
that it contains dissolves in the water, and this, too, so much the
better the colder the latter is. This apparatus, then, permits of
obtaining two results: a mechanical one, consisting in the stoppage of
the solid matters, and a chemical one, consisting in the stoppage of the
soluble portions, such as ammonia, sulphureted hydrogen, and carbonic
acid.
[Illustration: FIG. 1.--CONDENSO-PURIFIER FOR GAS. (Elevation.)]
The condenso-purifier consists of three perforated diaphragms, placed
one over the other in rectilinear cast-iron boxes. These diaphragms are
movable, and slide on projections running round the interior of the
boxes. In each of the latter there is an overflow pipe, g, that runs to
the box or compartment below, and an unperforated plate, f, that slides
over the diaphragm so as to cover or uncover as many of the holes as may
be necessary. A stream of common water runs in through the funnel, e,
over the upper diaphragm, while the gas enters the apparatus through the
pipe, a, and afterward takes the direction shown by the arrows.
Reaching the level of the overflow, the water escapes, fills the lower
compartment, covers the middle diaphragm, then passes through the second
overflow-pipe to cover the lower diaphragm, next runs through the
overflow-pipe of the third diaphragm on to the bottom of the purifier,
and lastly makes its exit, through a siphon. A pressure gauge, having an
inlet for the gas above and below, serves for regulating the pressure
absorbed for each diaphragm, and which should vary between 0.01 and
0.012 of a meter.
The effect of this purifier is visible when the operation is performed
with an apparatus made externally of glass. The gas is observed to enter
in the form of smoke under the first diaphragm, and the water to become
discolored and tarry. When the gas traverses the second diaphragm, it is
observed to issue from the water entirely colorless, while the latter
becomes slightly discolored, and finally, when it traverses the third
diaphragm, the water is left perfectly limpid.
Two diaphragms have been found sufficient to completely remove the solid
particles carried along by the gas, the third producing only a chemical
effect.
This apparatus may replace two of the systems employed in gas works: (1)
mechanical condensers, such as the systems of Pelouze & Audouin, and
of Servier; and (2) scrubbers of different kinds and coke columns.
Nevertheless, it is well to retain the last named, if the gas works have
them, but to modify their work.
[Illustration: FIG. 2.--PLAN VIEW WITH BY-PASS.]
This purifier should always be placed directly after the condensers, and
is to be supplied with a stream of pure water at the rate of 50 liters
of water per 1,000 cubic meters of gas. Such water passes only once into
the purifier, and issues therefrom sufficiently rich in ammonia to be
treated.
If there are coke columns in the works, they are placed after the
purifier, filled with wood shavings or well washed gravel, and then
supplied with pure cold water in the proportion stated above. The water
that flows from the columns passes afterward into the condenso-purifier,
where it becomes charged with ammonia, and removes from the gas the tar
that the latter has carried along, and then makes its exit and goes to
the decanting cistern.
In operating thus, all the remaining ammonia that might have escaped the
condenso-purifier is removed, and the result is obtained without pumps
or motor, with apparatus that costs but little and does not occupy much
space. The advantages that are derived from this, as regards sulphate
of ammonia, are important; for, on treating ammoniacal waters with
condensers, scarcely more than four to five kilogrammes of the sulphate
are obtained per ton of coal distilled, while by washing the gas
perfectly with the small quantity of water indicated, four to five
kilogrammes more can be got per 1,000 kilogrammes of coal, or a total of
eight to ten kilogrammes per ton.
When the gas is not washed sufficiently, almost all of the ammonia
condenses in the purifying material.
The pressure absorbed by the condenso purifier is from ten to twelve
millimeters per washing-diaphragm. In works that are not provided with
an extractor, two diaphragms, or even a single one, are employed when it
is desired simply to catch the tar.
The apparatus under consideration was employed in the St. Quentin
gas works during the winter of 1881-1882, without giving rise to any
obstruction; and, besides, it was found that by its use there might be
avoided all choking up of the pipes at the works and the city mains
through naphthaline.
In cases of obstruction, it is very easy to take out the perforated
diaphragms; this being done by removing the bolts from the piece that
holds the register, f, and then removing the diaphragm and putting in
another. This operation takes about ten minutes. The advantages of such
a mounting of the diaphragms is that it allows the gas manufacturer to
employ (and easily change) the number of perforations that he finds best
suited to his needs.
These apparatus are constructed for productions of from 1,000 to 100,000
cubic meters of gas per twenty four hours. They have been applied
advantageously in the washing of smoke from potassa furnaces, in order
to collect the ammonia that escapes from the chimneys. In one of such
applications, the quantity of gas and steam washed reached a million
cubic meters per twenty-four hours.--_Revue Industrielle._
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