September 25, 1914.

THE COLLIERY GUARDIAN.

677

Utilisation of Heat

By WALTER

For many years past efforts have be* n made, from
time to time, to use the beat contained in slags, which
at present is wasted. The late Sir Lowthian Bell
evaporated brine for the manufacture of salt by means
of this heat, but it was not a commercial success. Some
four years ago Messrs. Bell Brothers again began
experiments with a view to using the steam produced
from slag in a low pressure turbine. The slag used was'
that produced in the manufacture of ordinary Cleveland
iron having an average analysis of:—Silica, 28'30 per
cent.; alumina, 24'78; feirous oxide, 0'30; lime, 32'39;
sulphide of lime, 3'67 ; magnesia, 8'94; manganous oxide,
0'36 ; and alkalies, 1'26 per cent.

The apparatus for producing the steam consists of a
wrought iron circular vessel B. Near one edge of the
top plate of the granulator B is the hole through which
the slag is poured (c); on the underside of this top plate
and round the hole a circular ring 4 in. deep is fixed,
which dips into the water to a depth of 3in., thus
forming an hydraulic seal, and preventing the steam
from escaping; inside the granulator are four vanes
fixed on a vertical shaft D, which cause the water to
rotate. The slag, comes fiom the furnace along the
trough or channel A. When the slag drops into the

Fig. 1.—Kestner Patent Evaporator.

water it granulates, and its velocity causes it to sink a
certain depth. It floats for a time, but the rotation of
the water causes it to come to the surface inside the
vessel, otherwise it would block up the slag entrance;
the granulated slag is then lifted by the elevator E into
a second seal F, and there becomes waterlogged, sinks
through the seal, and is taken by a second elevator and
dropped into trucks. The feed water is introduced
along with the slag C ; the surplus water which drains
from the truck is also pumped back to 0 by a small
pump fixed to the side of the apparatus. The steam
generated comes off at G-; at first it was intended to use
this steam direct in an exhaust steam turbine. After
numerous experiments on blades of different metal, it
was found that duraluminium was affected very slightly,
and a 50 kw. turbine with blades of this material was
experimented with.

The steam produced from ordinary grey Cleveland
slag contains about 0*5 per cent, by volume of incon-
densable gases, the average analysis of which is:—
sulphuretted hydrogen, 29 per cent.; hydrogen, 55 ; and
nitrogen, 16 per cent.

To deal with these gases a very big air pump would
be required, so it was essential to absorb them between
the condenser and the air pump. This was done by
washing first with milk of lime to absorb the sulphuretted
hydrogen, and then passing the remainder through a
tube containing calcined Cleveland ironstone heated to
a temperature of about 750 degs. Cent., and recondensing
the water produced. The nitrogen was dealt with by
the air pump. Under these conditions the plant ran
for two months ; at the end of that time the turbine was

* A paper submitted for discussion at the autumn
meeting of the Iron and Steel Institute, now abandoned.

Contained in Slag.*

L. JOHNSON.

opened out, and the openings were found to be partly
blocked up with fine sulphur, which had caused some
wear of the blades. The sulphur, which it was
impossible to eliminate by filtering the steam, was
produced by the reaction:—

2H2S+SO2=2H2O+3S,

this reaction being the probable cause of the entire
absence of sulphur dioxide in the steam. The direct
method was then abandoned, and a water heater and
heat exchanger were introduced between the turbine and
the primary generator. The water-heater consists of an
outer casing and tube plates with tubes in. diameter
fixed therein, placed vertically, the total heating surface
being 156 square feet.

The one shown in the illustration is an improvement
but the one above described was used in order to see
what action, if any, there was on the tubes. They were
examined every week, but did not show any undue
corrosion; there was, however, a deposit of fine suphur
on the shell and tubes.

The calandria (a Kestner single-effect climbing film
evaporator) consists of 2 parts—the calandria proper
and the separator. The former is composed of a shell
or casing containing the e\aporating tubes, which aie
about 23 ft. long and lT7fVin. diameter, and are fixed in
upper and lower tube plates. The water is fed into the
lower end of the heater H at J, and then passes from
the upper end by the pipe K into the separator L. The
dirty steam from the generator B passes inside the
tubes of the heater, the clean water being on the

HLO W/UUHtUT

Slag Steam Generator [

Fig. 3
PLAN

il

Fij.2 Section through Slag Steam Generator
ELEVATION

outside, and the uncondensed remainder enters the
calandria at M.

The water in the tubes is caused to boil by the steam
with which they are surrounded, and as ebullition takes
place a column of vapour rises up the centre of each
tube. This vapour travels at a high velocity, carrying
with it a film of water on the inner surface of the tubes.
The water does not “ climb ” by capillary attraction nor
by the liquid and the steam forming alternate links in
the same way as in a Pohle air-lift. .The operation is
performed in a simple manner ; the water begins to boil
in the tubes, and is gradually drawn up in a complete
film by the vapour itself. As a result of this action, a
certain amount of water is carried up into the separator
L, which acts as a steam drier; this water and the feed-
water from the heater, which enter at N, flow down the
pipe O, entering the calandria at the bottom. The
clean steam is delivered by the pipe P to the turbine,
which is connected with the condenser in the usual
manner. The sulphur deposited in the tubes of the
heater is brushed out, and that in the calandria is
removed by occasionally filling the dirty steam space
with a dilute solution of caustic soda and heating with
steam. There seems to be very little corrosion of the
tubes of the heater or calandria; and after four years of
intermittent working the primary generator does not
show any signs of undue corrosion, the shafts of the
elevator having a very thin black skin on the surface
only.

The heating surface of the calandria is 548 square feet.
A vacuum of about 9 in. of mercury is maintained in the
separator, so that the water boils at 90 to 91 degrees
Cent. With steam from the slag at 100 degs. Cent, and
keeping a temperature in the calandria of 91 degs., the
mean of 22 experiments gave 173 gallons of water
evaporated per hour, and the average steam per hour
condensed in the calandria and heater was 190’2 gallons.
The feed water entered the heater at an average
temperature of 24'6 degs. Cent, and entered the calandria
at an average temperature of 89 degs.—that is, 91 lb. of
clean water was evaporated for every 1001b. of steam
from the slag. With the steam from the slag at
100 degs. and the temperature of 90'50 degs. Cent., the

mean of 27 experiments gave 177’2 gallons of water
evaporated per hour, and the total steam condensed in
the calandria and the heater was 198’3 gallons per hour.
The average temperature of the feed-water was 26 degs.
Cent., and of the water entering the calandria 89 degs.
Cent,, or 89’4 lb. of water were evaporated for 100 lb. of
dirty steam.

As the condensation of dirty steam takes place, the
percentage of incondensable gases naturally increases.
When the percentage gets above 7’5 the calandria
begins to lose its efficiency, and it is advisable not to
allow that percentage to be exceeded. In order to
control it a small outlet pipe is arranged on the top of
the calandria, where the incondensable gases are drawn
off together with a small proportion of steam ; with 0’5
per cent, of gas in the dirty steam, there will be a loss
of 6’6 per cent, of steam.

Experiments were also made to determine the amount
of available steam from the slag by condensing and
measuring it. The mean of seven experiments gave
1,017 lb. per ton of slag, and deducting 6’6 per cent, for
escape with the incondensable gases, there are left
9501b., and 90 per cent, of this gives 855 lb. of clean
steam available for the turbine. Since modern exhaust
steam turbines with a full load and a vacuum of 28J in.
can be guaranteed under the above conditions to use not
more than about 27 lb. per horse-power, this gives
31 6-hoise power per hour per ton of slag per hour.

Cost— It is impossible to give the cost of running
such a plant, because the practice at different works
varies considerably. Apart from handling the slag, the
cost of running the electric installation is the same as
an ordinary exhaust steam turbine plant of a similar
size, and the attendant can regulate the water in the
calandria; there is, however, about 2 per cent, more
power required for the greater amount of condensing

SECTION THRC’JGH HEATER

LlLAN VtATLRINLET

. CLEAN STEM
' TO TURBINE

BIAS STEM INLJT_^

fl©

Rg.4. EVAPORATING PLANT
SIDE VIEW

ARRANGEMENT FOR

Generating Steam from Slag

water per horse-power ; where the slag is already being
granulated, there is the extra upkeep of the second
elevator. One man per furnace should be able to attend
to the primary generator and running in the slag, the
remainder being all mechanical.

Chile’s Coal Resources.—Dr. Johannes Bruger, who -was
employed by the Government of Chile to study the coal
deposits of the Republic, states that there is enough coal in
the carboniferous region of the province of. Arauco to supply
the needs of Chile for a period of 200 years. This expert,
who last year carefully examined the northern part of the
province of Arauco, found practically inexhaustible coal
deposits, the richest and most extensive of which are in the
coast region of the province. In the neighbourhood of the
town of Buena-Piden there is an abundance of coal. These
deposits were exploited on a large scale some years ago, and
railways and wharves were constructed to facilitate the
mining and shipping of the product. Work was, however,
suspended because a fault was discovered in the vein, suffi-
cient search not having been made to discover the continu-
ation of the deposit, which in reality was but a short dis-
tance away. In the vicinity of Lavapie, the Pacific Ocean
has laid bare coal veins along the beach for a considerable
distance. The hills in the neighbourhood of Ronquiel, Mis-
longue, and Millaneco contain large deposits of an excellent
quality of coal. The coal mines now in operation in the
province of Arauco by the Curanilahue Company, and the
Porvenir and Victoria mines, have immense supplies of coal,
which will last for many years. From Curanilahue to
Pipilco and from Cuyinco to Temuco (Caramavida) coal out-
croppings can be traced scarcely without a break, and the
vein between the last two places is 1 metre 30 centimetres
thick, the coal being of good quality and free from deleterious
foreign substances. South of the line from Lebu to Temuco
there is but little coal, and some of it is of such poor quality
as to be practically worthless for commercial purposes.