Improved Process for Transforming Roasted Cements into Powder, and in Apparatus therefor.
Year: 1894

page_text: Date of Application, 1st Feb., 1894-Accepted, 20th Oct.,
1894
Improved Process for Transforming Roasted Cements into Powder,
and in Apparatus therefor.
We, DOMINIQUE BELLOC, Engineer, of. 7 Rue Le Verrier, Paris in the
Republic of France, and EMILE BÉNARD, Architect, of 29 Boulevard Péreire,
Paris aforesaid, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement:-
This invention relates to an economic process for the manufacture of cements,
with a considerable diminution in the cost of fuel and of converting the cement,
once roasted, into powder.
We have observed, in the course of our numerous experiments, that the materials
employed in the manufacture of cement which are roasted to the moment,
crystallize like "Peridot" forming a compound, homogeneous, definite and
invariable; this crystalline compound has the property of becoming exhausted,
splitting and scaling, and of reducing itself automatically to powder under the
influences of progressive decrease of temperature, by an action or process very
similar to that of the extinction of lime.
Taking these observations as a basis we have invented the process which is the
subject of the present Application.
Our process consists in roasting the primary materials, for example, chalk or
carbonate of lime, argillaceous marls or mud or a calcareous marl containing from
19 to 25 per cent. of clay or any others usually entering into the composition and
manufacture of cements, with as much uniformity as is possible. For this purpose,
the materials either in the raw state or having previously been dried and heated,
are placed in a furnace or roasting oven in lumps of any shape, but uniform in
size, and preferably of small dimensions; and we cause combustible gases or gases
at a high temperature to circulate in contact with such pieces, so as to raise the
temperature of the mass gradually and uniformly, in order to effect the perfect
roasting gradually. The mass being completely roasted, we leave it to cool slowly
and progressively down in the furnace or oven itself; or we remove it therefrom,
in order to submit it thus more or less rapidly to the effects of contact with a cooler
atmosphere, or with cooling surfaces. Under the influence of such gradual
lowering of temperature, the crystals which have been formed in the heart of the
mass become disintegrated, and the pieces of cement which are thoroughly_and
properly roasted become exhausted, lose cohesion, and fall into a powder; those
small portions which are either over-roasted or incompletely roasted alone remain
in lumps, whole, and can easily be separated by screening from cement-powder of
good quality.
This subsequent sorting and separation is to be done at once, as quickly as may
be possible, in order to ensure the effectual selection and separation of the cement
particles which have roasted to the very moment that is proper, from those lumps
which are either not enough or too much roasted; because, of the latter, those
which are not sufficiently done also possess the quality of losing cohesion and falling
into powder, in a less degree, requiring therefore a much longer time, relatively, for
the completion of the process.
Our process may be employed with all existing cement furnaces or ovens, on
whatever system they may have been constructed, provided the charges of primary
materials adapted for use in the manufacture of cements are reduced to fragments
of uniform size and small dimensions.

page_text: The roasting of the lumps is effected by causing the combustible gases,
generated by any known means, to circulate throughout the mass of these lumps,
piled up in a roasting oven, and through all the interstitial spaces between the
lumps.
In certain cases we regulate the roasting in the heart of the mass by incor-
porating with the primary raw materials, in Jumps or in powder, a certain
proportion of solid fuel in powder, such as for example, powdered charcoal of wood,
or of breeze; this powdered fuel, at a red heat, forms in the heart of the mass,
in conjunction with the gases disengaged therefrom, a combustible
gas which
promotes, develops and regulates the roasting of all the constituent elements of
the said mass.
We must be understood to claim the application of our process to all kinds of
furnaces or ovens adapted for roasting cements.
To facilitate the comprehension of the means which may be employed for
carrying out our process industrially we have, by way of example, illustrated in the
accompanying drawings, some kinds of roasting-furnaces or ovens that we have
designed for the purpose.
In these drawings, wherein the same letters of reference throughout indicate the
same or corresponding parts in the different figures, the various types of furnace or
oven are shown in vertical section.
Figure 1 represents a furnace, with a central roasting chamber a which is
charged and emptied, in the axial line of the said chamber, through openings
and c.
The combustible gases enter by the flues d arranged laterally at the
upper part of the said chamber a; they traverse the chamber from top to bottom,
before issuing laterally, by the flues e at the lower part of the chamber
Figure 2 represents a furnace, with a central roasting chamber a charged through
an upper opening b in the axial line of the chamber, but emptied laterally by the
two lower openings c. The combustible gases issue from the flues d arranged
laterally at the top, descending and again ascending by the side flues d¹ and
entering at the top of the chamber a which they traverse from top to bottom,
making their escape from the bottom through a flue e in the axial line of the
chamber. The inlet-opening of this flue e is protected by a dome or cone g
which leaves a free passage to the gases to find an outlet through the apertures e¹.
Figure 3 represents a furnace with central roasting chamber a charged from
above but laterally through the openings and cleared also laterally at the bottom
through the apertures c. The combustible gases, on arrival, are distributed over
the whole superficial area, of the materials which are to be roasted, in chamber a
by a central flue d provided with numerous inlet apertures d'; and, after traversing
the mass from top to bottom, they escape by the apertures e' in the dome or cone g
into the central exit flue c. Pipes perforated with a series of openings are
arranged obliquely in the direction of the height of the chamber and serve to
conduct and distribute the combustible gases in the heart of the materials
accumulated in the chamber. The combustible gases supplied to the chamber a
are produced in any suitable generator.
The chamber a may be of any horizontal section, circular, polygonal, rectangular,
etc.; its walls may be rectilinear or curvilinear, vertical or inclined; the dome g
may be formed with inclined rectilinear or curvilinear walls, in such manner as to
convey the roasted materials in the direction of the discharge-orifices c so that they
cannot obstruct the outlet-openings e¹ of the gases which have parted with their
heat to the materials charged into the chamber a.
The materials being uniformly heated in all parts of the chamber a by reason of
the regular circulation of the combustible gases in contact with all the elements of
the mass of materials, nothing more is needed than to remove the plug or plugs c
to remove the materials, when we consider that the necessary temperature has been
maintained sufficiently long to secure the thorough and perfect roasting of the
cement. We thus bring the roasted mass in contact with the open air which
brings about the progressive lowering of the temperature of the cement, and the

page_text: disintegration and pulverisation of that portion which is perfectly and properly
roasted, a process which is completed in a very short time. By a subsequent
sorting process we separate these pulverulent particles from the coarser pieces
consisting of over-roasted or insufficiently roasted material.
Leaving the said grosser pieces in contact with the air for a much longer period
of time, we promote the slow disintegration of those lumps of cement which have
not been sufficiently roasted, while those which have been over-roasted remain
whole, in lumps; it suffices for us then to repeat the sorting process, to enable us
to separate, from such lumps of overdone material, all the underdone material,
which may then be roasted again. By this regular roasting in contact with com-
bustible gases, followed by a gradual cooling, and successive sorting processes we
are enabled to reduce the cement to powder.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. A process for the automatic conversion of roasted cements into fine powder,
consisting in charging the furnace or oven with the raw materials either previously
dried and heated or not, in lumps of any form but of uniform size and preferably of
small dimensions and then in roasting such materials so prepared by causing com-
bustible gases to circulate around and through and in contact with all the pieces in
the mass so as gradually regularly and uniformly to raise the temperature of the
mass to obtain the complete and perfect roasting thereof and the proper
crystallisation of the cement; then in progressively lowering the temperature of
the roasted cement either in the furnace or oven itself or removed therefrom, to
bring about the scaling and loss of cohesion of the crystals so as to cause them
to disintegrate and fall of themselves into powder and finally in sorting the mass so
as to separate those portions of cement which are perfectly roasted from those
lumps which are either under or over roasted so as to be enabled by a further
operation or process to submit the residue to a slow and more prolonged cooling so
that the insufficiently roasted particles after disintegration into powder may be
roasted anew while the over-roasted cement remains whole in lumps.
2. The process for the regular and uniform roasting of the primary materials
entering into the manufacture of cements consisting in the incorporation with the
primary raw materials in lumps or powder of a certain proportion of powdered
wood-charcoal or breeze or of other comminuted fuel and in roasting the mass by
causing combustible gases to circulate through the charge in the furnace.
3. The various types of furnace with continuous fire and intermittent charges
which realised this process comprising a central roasting chamber a traversed from
top to bottom by combustible gases which are introduced into the chamber by
orifices d' and perforated pipes the charging of the said chamber taking place at
its upper part by means of apertures b arranged in the axis or at the sides of the
chamber and its emptying being effected by openings e placed in the axis or at the
sides of the chamber substantially as described and illustrated in the accompanying
drawings.
Dated this 1st day of February 1894.
W. P. THOMPSON & BOULT,
Agents for the Applicants.