Bourne Archive:
Muspratt: Cement: Rüdersdorf
kiln
http://boar.org.uk/aaiwxw3Muspratt2Cement.htm Latest edit 17 May
2011
The Bourne Archive
Muspratt’s Chemistry, Theoretical,
Practical & Analytical (ca. 1859)
Extracts Concerning Building Cements, 2.
This is part of an article on chemical bonding materials
under the heading ‘Cement’. It is presented here in three web pages, respectively
dealing with
fairly simple lime
burning kilns; the present one, dealing with a large lime kiln in Brandenburg; and with mortar.
Vol. 1. pp. 453-6
BUILDING CEMENTS. –
[continued]
As an economiser of fuel, the
limekiln of RUDERSDORF1
is the best. Fig. 299 is a vertical section of this kiln, which is heated by
wood and peat. The Shaft, C, is like the foregoing, formed of two truncated
cones, and is about fifty-six Hessian feet [14 m (a
Hessian foot was 0.25 m)] in height. It is seven feet in diameter at the top and base, and ten
feet in the widest part, opposite where the fires are situated. In the
construction of the shaft, limestones may be used in the walls; but that part
to which the heat reaches is usually faced with firebrick, the thickness of
which increases from half a brick to a brick and a half in thickness as it
approaches the seat of the heat. This lining reaches to the height of forty
feet, and is shown in the figure at d’;
the wall being represented by d d.
All these are encased in an exterior wall, e
e, built of the same material as d d,
leaving a space of a few inches in diameter, which is filled with ashes and
other non-conducting material. This serves to retain the heat, and likewise to
afford room for the expansion of the firebricks and stones which takes place
when strongly heated. An outer wall, B B, encloses the whole, and the
intermediate space is divided into several compartments by means of arches, p p p, which serve as receptacles for
the lime, and a temporary domicile for the workmen. The fires for heating the
limestones are three, and are seen at b b,
placed at equal distances from each other. These are arched over and the arches
are lined with firebrick. The grates are composed of two perforated tiles,
resting in the middle upon the brickwork, f;
the perforations of these tiles, by which a current of air, entering by the
passage, h, is admitted to the fire,
are about one inch wide, and three or four in length. g is closed by an iron door, as also the outlet from i, where the cinders collect at first,
and then fall into the channel, whence they are cleared off through the door, z.
These doors are left shut until the space, i,
is filled, and the cinders have sufficiently cooled to be removed conveniently.
The draught-holes where the burnt lime is abstracted are seen at a a; these are closed with iron doors,
which are luted [sealed with clay or
similar material],
except at such times as the content is being taken out, in order that the air
may not enter at these orifices to cool the kiln. To facilitate the descent of
the lime to these apertures, the sole of the kiln is inclined downwards towards
them. As the lime is very hot when the chamber, P, into which the hot air
ascends, a current being instituted in this passage by the fires.
Fig. 300 shows the plan of the
preceding, at the lines, Z Z, the section being horizontal with the fires, b b, on the one side, and with the
draught-holes, a a, on the other.
When the kiln is set in operation, the part of the shaft to the level of the
fires is filled with limestone, and fires lighted in a a a, which are kept burning till the calcination is completed. A
fresh quantity of limestones is now let down by buckets upon that already
burned, and continued till the shaft is quite full, when a heap, three or four
feet high, is raised over the mouth. The doors at a a a being luted on, so as to shut off the draught, the fires are
lighted in b b b, and kept up constantly.
Whenever the upper stones are observed to be well burned, the lime under the
level of the fires is drawn out; this causes the top column to fall in, upon
which a fresh quantity of limestones is thrown on and piled upon the mouth as
before. Thus the work progresses without interruption; the lime, however, is
drawn out only at periods of twelve hours, when about sixty to seventy-two
hundreds, Hessian weight [3,000 to
3,600 kg. (a Hessian
Zentner
or hundred was 50 kg. i.e. 100
Hessian pounds)], are
abstracted.
The time required for
burning lime is affected by many causes, such as the size of the stones, their
freshness, and density. It is well known that compact limestones are more
difficultly burned, than such as are more porous; also, that moisture to some
extent facilitates the expulsion of the carbonic acid, even at a lower degree
of heat than is required when the limestone is dry. The usual practice of
moistening the stones is not so economical as introducing a jet of steam into
the kiln; for, in the first case, the heat serves only to evaporate the water
before the material can be brought to redness, by which much fuel is wasted;
but in the latter, the limestone may be heated to redness, and then the steam
admitted, when it will be most serviceable. Where kilns are like the one above
described are being constantly worked, there is a great saving of fuel effected
by them; but it is evident that they are adapted only for such places as
require a very large quantity of lime, and where , consequently, they can be
kept in operation without intermission. Theoretically, the consumption of fuel
in causticising or burning lime, is only one-tenth of the weight of the
limestone; but in ordinary practice, five or six times the quantity which
theory shows to be sufficient is used; and where lime is burned for
agricultural purposes, and attendance is not very regular, even a much larger
amount is consumed.
It is evident,
therefore, that those who are engaged in these operations would do well to give
the subject their best attention. Much care is required of the lime-burner,
especially if the material is of an hydraulic nature; for if he allows the
temperature to rise higher than what is required to expel the carbonic acid,
the lime in consequence loses its property of setting or hardening.
RJP’s Footnote.
1. ^ It is not immediately clear where this was.
There are several localities bearing the name, in Germany
and Austria Berlin Berlin
Such
kilns in simpler forms, without the outer accommodation, may be seen today at
the Rüdersdorf museum village.