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Page 17
The receiving instruments can be made recorders also by simple
devices. Thus, having only a most delicate pressure in the primary
instrument, a distinct ink record may be made in the receiver, even
though the paper be rough and soft. The method is applicable to steam
gauges, water indicators, clocks, barometers, etc., in fact, to any
measuring instrument where a moving hand can be employed.
* * * * *
A NEW MONSTER REVOLVING BLACK ASH FURNACE AND THE WORK DONE WITH IT.
By WATSON SMITH, Lecturer in Chemical Technology in the Victoria
University, etc.
The Widnes Alkali Company, limited, to which I am indebted for
permission to describe this latest addition to a family of revolving
black ash furnaces, of late not only increasing in number, but also
individual size, has kindly allowed my friend, Mr. H. Baker, to
photograph the great revolver in question, and I have pleasure now in
throwing on the screen a picture of it, and also one of a revolver of
ordinary size, so as to render a comparison possible. The revolver of
ordinary size measures at most 18� ft. long, with a diameter of 12�
ft. The boiling down pans connected with such a furnace measure 60 ft.
in length. Each charge contains four tons of salt cake, and some of
these revolvers get through 18 tons of salt cake per day and consume
13 cwt. of coal per ton of cake decomposed.
With regard to the larger revolver, it may be just said that the
Widnes Alkali Company has not at once sprung to the adoption of a
furnace of the immense size to be presently given, but in 1884 it
erected a revolver only about 3 ft. to 4 ft. short of the length of
that one, and having two discharging holes. The giant revolving
furnace to be described measures in length 30 ft. and has a diameter
of 12 ft. 6 in. Inside length is 28 ft. 6 in., with a diameter of 11
ft. 4 in. It is lined with 16,000 fire bricks and 120 fire-clay blocks
or breakers, weighing each 1� cwt. The bricks weigh per 1,000 about
four tons. The weight of salt cake per charge (i.e., contained in
each charge of salt cake, limestone, mud, and slack) is 8 tons 12 cwt.
For 100 tons of salt cake charged, there are also charged about 110
tons of lime mud and limestone and 55 tons of mixing slack. In a week
of seven days about 48 charges are worked through, weighing of raw
materials about 25 _tons per charge_. The total amount of salt cake
decomposed weekly is about 400 tons, and may be reckoned as yielding
240 tons of 60 per cent. caustic soda. As regards fuel used for
firing, this may be put down as 200 tons per week, or about 10 cwt.
per ton of salt cake decomposed. Also with regard to the concentration
of liquor from 20� Tw. to 50� Tw., there is sufficient of such
concentrated liquor evaporated down to keep three self-fired caustic
pots working, which are boiled at a strength of 80� Tw. Were it not
for this liquor, no less than seven self-fired pots would be required
to do this work, showing a difference of 80 tons of fuel.
[Illustration: A NEW MONSTER REVOLVING BLACK ASH FURNACE. (2 Figures.) ]
The question may be asked, "Why increase the size of these huge pieces
of apparatus?" The answer, I apprehend, is that owing to competition
and reduction of prices, greater efforts are necessary to reduce
costs. With automatic apparatus like the black ash revolver, we may
consider no very sensible addition of man power would be needed, in
passing from the smallest sized to the largest sized revolver. Then,
again, we may, reckoning a certain constant amount of heat lost per
each revolver furnace of the small size, consider that if we doubled
the size of such revolver, we should lose by no means double the
amount of heat lost with the small apparatus; but only the same as
that lost in the small furnace _plus_ a certain fraction of that
quantity, which will be smaller the better and more efficient the
arrangements are. Then, again, there is an economy in iron plate for
such a large revolver; there is economy in expense on the engine power
and on fuel consumed, as well as in wear and tear.
Just to mention fuel alone, we saw that with an ordinary large sized
revolver, the coal consumption was 13 cwt. per ton of salt cake
decomposed in the black ash process; but with the giant revolver we
have been describing, that consumption is reduced to 10 cwt. per ton
of cake decomposed.
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