|
Main
- books.jibble.org
My Books
- IRC Hacks
Misc. Articles
- Meaning of Jibble
- M4 Su Doku
- Computer Scrapbooking
- Setting up Java
- Bootable Java
- Cookies in Java
- Dynamic Graphs
- Social Shakespeare
External Links
- Paul Mutton
- Jibble Photo Gallery
- Jibble Forums
- Google Landmarks
- Jibble Shop
- Free Books
- Intershot Ltd
|
books.jibble.org
Previous Page
| Next Page
Page 18
[Illustration: A NEW MONSTER REVOLVING BLACK ASH FURNACE. (2 Figures.)]
The question will be probably asked, How is it possible to get a flame
from one furnace to carry through such a long revolver and do its work
in fusing the black ash mixture effectively from one end to the other?
The furnace employed viewed in front looks very like an ordinary
revolver fireplace, but at the side thereof, in line with the front of
the revolver, at which the discharge of the "crude soda" takes place,
there are observed to be three "charging holes," rather than doors,
through which fuel is charged from a platform directly into the
furnace through those holes.
The furnace is of course a larger one than furnaces adjusted to
revolvers of the usual size. But the effect of one charging door in
front and three at the side, which after charging are "banked" up with
coal, with the exception of a small aperture above for admission of
air, is very similar to that sometimes adopted in the laboratory for
increasing heating effect by joining several Bunsen lamps together to
produce one large, powerful flame. In this case, the four charging
holes represent, as it were, the air apertures of the several Bunsen
lamps. Of course the one firing door at front would be totally
inadequate to supply and feed a fire capable of yielding a flame that
would be adequate for the working of so huge a revolver. As an effort
of chemical engineering, it is a very interesting example of what
skill and enterprise in that direction alone will do in reducing
costs, without in the least modifying the chemical reactions taking
place.--_Journal Soc. Chem. Industry._
* * * * *
IMPROVEMENTS IN THE MANUFACTURE OF PORTLAND CEMENT.[1]
[Footnote 1: A paper recently read before the British
Association.]
By FREDERICK RANSOMS, A.I.C.E.
So much has been said and written on and in relation to Portland
cement that further communications upon the subject may appear to many
of the present company to be superfluous. But is this really so? The
author thinks not, and he hopes by the following communication, to
place before this meeting and the community at large some facts which
have up to the present time, or until within a very recent date, been
practically disregarded or overlooked in the production of this very
important and valuable material, so essential in carrying out the
great and important works of the present day, whether of docks and
harbors, our coast defenses, or our more numerous operations on land,
including the construction of our railways, tunnels, and bridges,
aqueducts, viaducts, foundations, etc. The author does not propose to
occupy the time of this meeting by referring to the origin or the
circumstances attendant upon the early history of this material, the
manufacture of which has now assumed such gigantic proportions--these
matters have already been fully dealt with by other more competent
authorities; but rather to direct the attention of those interested
therein to certain modifications, which he considers improvements, by
means of which a large proportion of capital unnecessarily involved in
its manufacture may be set free in the future, the method of
manufacture simplified, the cost of manipulation reduced, and stronger
and more uniformly reliable cement be placed within the reach of those
upon whom devolves the duty and responsibility of constructing works
of a substantial and permanent character; but in order to do this it
will be necessary to allude to certain palpable errors and defects
which, in the author's opinion, are perpetuated, and are in general
practice at the present day.
Portland cement is, as is well known, composed of a mixture of chalk,
or other carbonate of lime, and clay--such as is obtained on the banks
of the Thames or the Medway--intimately mixed and then subjected to
heat in a kiln, producing incipient fusion, and thereby forming a
chemical combination of lime with silica and alumina, or practically
of lime with dehydrated clay. In order to effect this, the usual
method is to place the mechanically mixed chalk and clay (technically
called slurry), in lumps varying in size, say, from 4 to 10 lb., in
kilns with alternate layers of coke, and raise the mass to a glowing
heat sufficient to effect the required combination, in the form of
very hard clinker. These kilns differ in capacity, but perhaps a fair
average size would be capable of producing about 30 tons of clinker,
requiring for the operation, say, from 60 to 70 tons of dried slurry,
with from 12 to 15 tons of coke or other fuel. The kiln, after being
thus loaded, is lighted by means of wood and shavings at the base,
and, as a matter of course, the lumps of slurry at the lower part of
the kiln are burned first, but the moisture and sulphurous gases
liberated by the heat are condensed by the cooler layers above, and
remain until the heat from combustion, gradually ascending, raises the
temperature to a sufficient degree to drive them further upward, until
at length they escape at the top of the kiln. The time occupied in
loading, burning, and drawing a kiln of 30 tons of clinker averages
about seven days. It will be readily understood that the outside of
the clinker so produced must have been subjected to a much greater
amount of heat then was necessary, before the center of such clinker
could have received sufficient to have produced the incipient fusion
necessary to effect the chemical combination of its ingredients; and
the result is not only a considerable waste of heat, but, as always
occurs, the clinker is not uniformly burnt, a portion of the outer
part has to be discarded as overburnt and useless, while the inner
part is not sufficiently burnt, and has to be reburned afterward.
Moreover, the clinker, which is of excessively hard character, has to
be reduced by means of a crusher to particles sufficiently small to be
admitted by the millstones, where it is ground into a fine powder, and
becomes the Portland cement of commerce.
Previous Page
| Next Page
|
|