There are two floors, one on the ground level, a few feet only above the
outlet for drainage, the other floor, or raised platform, being 15 feet
above it. The refuse is taken in carts up an incline of 1 in 14 on
cast-iron tram plates to the upper floor, and deposited upon and
alongside of the destructor, and is shoveled into a row of hoppers at
the head of the cells. These hoppers are in the middle of the width of
the destructor, and each communicates with a cell on each side of it.
The refuse is always damp, and often wet, and after being put into
the cells is gradually dried by the heat reflected upon it from the
firebrick arch of the cell, before it descends to the furnace. This
distinguishes the system from the common furnace, and enables the wet
material to be burned without other fuel. No fresh fuel is used after
the fires are once lighted. The vapor passes off with the gases of
combustion into a horizontal flue between the two rows of cells, through
an opening at the head of each cell, alongside that through which the
refuse is fed into it, the two openings being separated by a firebrick
wall. The refuse is prevented from falling into the flue by a bridge
wall across the outlet opening, over which the gases pass into the flue.
Between the destructor and the chimney a multitubular boiler is placed,
which makes steam enough for grinding into sand the clinkers which are
the solid residue of the burnt refuse. At Burmantofts an old chimney was
made use of, which is but 84 feet high; but at Armley Road a new chimney
was built, 6 feet square inside and 120 feet high. It is necessary to
make the horizontal flue large; that at Armley Road is 9 feet high and 4
feet wide. A large quantity of dust escapes from the cells--about 7 cwt.
a month--and unless the velocity of the air in the flue between the
destructor and the chimney were checked, the dust would be carried up
the chimney and might cause complaints; as, indeed, it has done with the
120-foot chimney, but whether with any substantial grounds is uncertain.
The dust is removed from the horizontal flue or dust chamber once a
month. Experience seems to indicate that there should be some sort of
guard or grating to prevent the entry into the chimney of charred paper
and similar light substances which do not fall to dust, and which are
sometimes carried up with the draught.
A six-celled destructor kiln burns about 42 tons of refuse in
twenty-four hours, leaving about one-fourth of its bulk of clinkers and
ashes. The clinkers are withdrawn from the furnaces five times each day
and night, or about every two-and-a-half hours, into iron barrows, and
wheeled outside the shed which covers the destructor, and when cold are
wheeled back to the mortar mills, of which there are two at each depot,
each having a revolving pan 8 feet in diameter, with 27-cwt. rollers,
the pan making twenty two revolutions a minute. Forty shovelfuls of
clinkers and twelve of slaked lime make 7 cwt. of mortar in thirty-five
minutes in each pan, which is sold at 5s. 6d. per ton. The engine
driving the two mortar mills has a 14 inch cylinder, 30 inches length
of stroke, and makes sixty revolutions per minute with 45 pounds steam
pressure per square inch in the boiler, when both mortar mills are
running. The boiler is 11 feet long, 8 feet in diameter, and has 132
tubes 4 inches in external diameter, which, together with the external
flues, are cleaned out once a month.
At first sight it would probably appear that no good mortar could be
made from such refuse as has been described, but having passed through
the furnace, the clinkers are, of course, perfectly clean, and with good
lime make a really strong and excellent mortar. They are also largely
used for the foundation of roadways.
The number of men employed is as follows: Two furnace men in the daytime
and two at night. They work from midnight on Sundays to 2 P.M. on
Saturdays, the fires being fully charged and left to burn through the
Sundays. One foreman, who attends also to the running of the engine, and
one mortar man. A watchman attends while the workmen are off.
In addition to a destructor, there is at the Burmautofts depot a
"carbonizer" kiln, in which the sweepings of the vegetable markets are
burned into charcoal. The carbonizer consists of eight vertical cells,
in two sets or stacks of four, separated by a space containing two
double furnaces, back to back, there being a double furnace also at each
end of the eight cells. Each of the stacks of four cells is 15 feet
6 inches high; the ends and middle parts, forming the tops of the
furnaces, being 6 feet high. The block of brick work containing the
eight cells and furnaces is 26 feet 6 inches long and 12 feet 4 inches
wide at the floor level. Each cell is 3 feet 6 inches by 2 feet, and
about 10 feet deep, with a chamber below about 3 feet deep, into which
the charred material falls and is completely burned. The top of the
cells is level with the upper platform, and they are fed through a loose
cover, which is immediately replaced. Inside the cells cast-iron sloping
shelves are hung upon the walls so that their upper edges touch the
walls, but the lower edges are some inches off, so that the hot air of
the furnaces passes upward behind the shelves round the four sides of
the cell in a spiral manner, and out near the top into a vertical flue,
which conducts it down to the horizontal flue at the bottom, which leads
to the chimney. The charcoal is withdrawn from the bottom of the heating
chamber through a sliding plate 2 feet above the floor, and is wheeled
red hot to the charcoal cooler, which is a revolving cylinder, nearly
horizontal, kept cool by water falling upon it, and delivers the
charcoal in two degrees of fineness at the end. It is worked by a small
attached engine, supplied with steam from the boiler before mentioned.
Each cell of the carbonizer can reduce to charcoal 50 cwt. of vegetable
refuse in twenty four hours, but at Leeds not quite so much is put
through. The quantity of market refuse passed through six cells of the
carbonizer varies from 3 to 10 tons a day, and averages about 4½ tons,
from which 15 cwt. of charcoal is obtained. The fuel for burning the
charcoal is derived from the ash pit refuse, some selected loads being
for that purpose passed over a sloping screen fixed between the upper
platform and the furnace floor, the fine ashes which pass through the
screen being taken away to the manure heaps, and the combustible parts
to the furnaces of the carbonizer. In this way a good deal of the ash
pit refuse is got rid of; it is often one-twelfth part of the whole
quantity.
The carbonizer and the destructor are set 33 feet apart, to allow room
for drawing the furnaces and for the mortar mills, but the space is
hardly sufficient. One man is employed in attending to the carbonizer.
Besides the openings at the top of the destructor through which the ash
pit refuse is fed into the cells, there is a larger opening in each
cell, kept covered usually, through which bed mattresses ordered by the
medical sanitary office to be destroyed can be put into the cells. These
openings are midway between the central openings and the furnace doors,
and whatever is put into the cells through these comes into immediate
contact with the fire. Advantage is taken of these openings for the
destruction of dead animals and diseased meat, and as much as 20 tons in
a year have been passed through the destructor.
The whole works are roofed over. The lower floor is open on two sides,
but the upper one is closed in, with weather boarding at Burmantofts and
with corrugated iron at Armley Road. At the former place the works
were in some measure experimental, and the platform was constructed
of timber, but at Armley Road it is of plate-iron girders, with brick
arching, weight being considered advantageous in reducing the vibration
of carting heavy loads over it.
The cost of each depot has been £4,500, exclusive of land, of which
about an acre is required for the destructor, carbonizer, inclined road,
weigh office, and space. A supply of water is necessary, a good deal
being required for cooling the clinkers. The population of the two
districts belonging to these works is about 160,000.
The author has no longer any connection with the works described, and
for the recent experience of their working he is indebted to Mr.
John Newhouse, the superintendent of the sanitary department of the
corporation.
* * * * *