July 2, 1915.

THE COLLIERY GUARDIAN.

15

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Bench Side of Ovens.





——Longitudinal. Elevation.-—-

-BASEMENT-

Plan.- ■

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General Arrangement, Exhaust Steam Turbine House.

approximately 83 ft. 7 in. long, 7 ft. Ilin, high, and
the mean width is 1 ft. 9 in. As is the ease with all of
the “Otto ” type of waste-heat ovens, the gas is led in,
pipes underneath the ovens, and each oven wall is
heated by 18 Bunsen burners, through which the gas is
evenly distributed throughout the whole length of the
oven wall, and even heating is thus obtained. Each
oven has 36 vertical flues : each Bunsen burner heats
two vertical flues, and the remaining three lead the
waste gases downwards into the main flue. A sloping
bench is provided, the coke being pushed out of the
ovens by means of an electrically-operated ram, and it
is then mechanically quenched before dropping down
the bench. At the bench the coke is loaded into railway
trucks alongside. The coal is brought from a belt con-
veyor, manufactured and erected by the Hepburn Con-
veyor Company Limited, of Wakefield, from the old
storage hopper used in connection with the installation
of beehive ovens to the crushed-coal storage hopper in
close proximity to the new ovens. This hopper supplies
the ovens with coal by means of tubs. The coal is
mechanically levelled in the ovens by means of a
levelling machine, which is combined with the coke-
pushing ram.

Recovery Plant for Tar, Ammonium Sulphate, and
Naphthalene.

The hot crude gas leaves the ovens by means of the
usual ascension pipes, and then enters the hydraulic
main. This main works on the semi-dry principle, tar
and liqur always flowing through it in an opposite direc-
tion to the flow of the gas. Any tar and moisture
which may have condensed in the latter is caught in
the tar catch tank, and from there it overflows to the
low-level deposit tanks. The gas collected in the
hydraulic main passes through a suction main into an
air cooler. This cooler is used as a temperature regu-
lator, and its duty is to cool the hot gas down to just
above the dew point. This temperature—dew point—
varies fairly considerably according to the quality of coal
used for coking, this being due to the quantity of
mechanical and chemical water in the coal. From the
air cooler the gas passes on to the spray tar extracting
apparatus. The gas is here met by a large volume of
tar and liquor, which is pumped under a high pressure,
sprayed, and then forced through the narrow neck of the
injector along with the crude hot gas. The sprayed tar
and liquor dashes against the small tar vesicles con-
tained in the crude hot gas, and it is by this means that
the tar is collected and precipitated. The actual make
of tar so extracted overflows into the afore-mentioned
tar deposit tank. The gas, now being freed from tar,
but still containing all ammonia, benzol, moisture, and
a large part of naphthalene, passes into a large enclosed
saturator containing weak hot sulphuric acid solution.
There are two saturators, each large enough to deal with
the gases from 40 ovens; thus one is kept for spare pur-
poses. In the saturator the gas is divided into a con-
siderable number of very small streams, and, owing to
the suction brought to bear upon it by the exhauster,
bubbles through a seal of this acid solution, whereby
all the ammonia is combined with the acid, and is
precipitated as sulphate of ammonia in the coned
bottom of the saturator. From this point it is mechani-
cally and continuously ejected by means of compressed
air, together with a certain amount of acid solution,
into the cone-shaped receiver. The ammonium sul-
phate crystals settle to the bottom of this receiver,
while the hot mother liquor overflows from the top,
and is led back by gravitation into the saturator. When
the cone-shaped receiver is full of crystallised sulphate
of ammonia the outlet cock on the bottom is opened, and
the sulphate passes then into a centrifugal dryer. In
this machine the sulphate is whizzed and thoroughly
freed of mother liquor, and is dried in a period of about
three minutes. The mother liquor, which has been
extracted through the whizzing of the salt, mixes with
the overflow from the receiver and flows back into the
saturator, whilst the dried sulphate of ammonia is
dropped through the bottom of the centrifugal machine
into the sulphate of ammonia store room, and can then
be bagged and shipped, or put into stock. The gas now
leaving the saturator, which is freed from both ammonia
and tar, but still containing all the benzol and moisture
and a part of naphthalene, passes through a lead-lined
catch-box. This box prevents any acid spray from
being carried over the saturators. From here the gas
passes on to the naphthalene spray cooler. Although
this cooler is quite devoid of any filling or apparatus, it
has on its top several nozzles through which cold water
is sprayed at high pressure downwards into the cooler.
The. action of this mass of finely-divided cold water
beating suddenly on to the hot gas produces a sudden
chill, which, together with the concussion brought about
by the water, precipitates and washes out practically all
the naphthalene, which flows away along with the water
into a catch-tank situated beneath this apparatus. The
naphthalene is filtered off. whilst the water is either
allowed to flow away, or is cooled and used over and
over again. This cooler serves the double purpose of
extracting the naphthalene from the gas as well as
cooling the gases to the requisite temperature for the
extraction of benzol. It is, of course, necessary to
extract the naphthalene, as otherwise it would pass to
the benzol scrubbers, where it would be dissolved by
the benzol wash oil, which would very soon become
saturated with naphthalene and rendered useless for the
extraction of benzol. The naphthalene so extracted is
of a pale yellow colour, and finds a ready sale. The
gas, now being cooled, but still containing all the
benzol, passes first through the exhauster, and thence
to two large vertical benzol scrubbers. There are two
exhausters of the Root® blower type, each capable of
dealing with the gases of 40 ovens, and thus one is
available as a stand-by. The benzol scrubbers are of
such a capacity that the gas flows very slowly through
them, so as to give ample time contact for the absorp-