IMPROVEMENTS IN THE MANUFACTURE OF HYDRAULIC LIME AND CEMENT
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office_
.
of the Commissioners of Patents on the 23rd November 1877. A communication,
from abroad by Mons. Leonce Vée, of Paris, in the Republic of France.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN THE MANUFACTURE OF HYDRAULIC LIME AND
CEMENT." A communication from abroad by Monst. Leonce Vée, of Paris, in the
Republic of France.
One of the essential conditions in manufacturing hydraulic lime and cement is to
work with materials which have been intimately mixed. This result is practically
obtained by grinding or reducing the substances to be employed to a fine powder,
and holding them in suspension in water. By this operation a semi-fluid paste is
produced, the solid parts of which have to be re-united in order to form them into
blocks which are baked in furnaces.
The separation of the solid parts from the liquid which holds them in suspension
is generally effected in tanks, the solid parts being allowed to settle to the bottom,
and the liquid drawn off. When the deposit is formed the soft paste is taken out
of the tank and drained; it is then dried, first in the open air, and afterwards by
utilizing the heat of furnaces. This operation is protracted, irregular, and expensive,
and the result is imperfect from a manufactural point of view.
The operation is protracted because the deposit takes place slowly in the tanks,
& it is necessary to perform several successive operations in the same tank, in order
to obtain a deposit of a certain thickness.
The operation is irregular, and during winter sometimes becomes wholly
impracticable, since the drying of the paste depends upon atmospheric conditions.
The operation is expensive, in the first place because it necessitates frequent
manipulations of the materials, and consequently considerable expense for labour,
and also because it involves the sinking of a large amount of capital; in fact owing
to the length of the process, the quantity of materials under treatment is always
considerable, and the impossibility of continuing operations during the winter
compels the manufacturer to prepare in the summer a supply of mixed materials

page_text: with which to work in the winter; lastly, the tanks occupy a considerable area of
ground, the acquisition of which increases the outlay.
It may moreover be observed that when the surface of the tanks at the disposal
of the manufacturer is insufficient, the factory is not regularly supplied, and when
space for constructing new tanks is not to be obtained, the amount of production
becomes limited, to the great prejudice of the interests of the owners; again, the
separation of the solid matter by allowing it to settle, and drawing off the liquid
does not yield a complete result in a manufacturing sense, since, as the substances
are deposited according to their degrees of density, the layer formed at each operation
is not of the same composition at different parts of its section.
The process forming the subject matter of this Invention has for its object the
dispensing with the employment of settling tanks, and consequently with the
manual labour which their use entails. It consists in separating the solid parts
from the milky liquid which holds them in suspension, and forming them into solid
blocks or cakes of homogeneous composition by means of one single operation of
short duration, capable of being carried out in all weathers day by day, according
to the requirements of the manufacture. This result is obtained by the employment
of the "filter press (or filtering apparatus operating by internal pressure ") with or
without the aid of external pressure for terminating the operation. By adopting
this process the operation is rendered short and inexpensive, and yields a more
perfect result than the means hitherto employed.
The apparatus termed "filter press" has been applied in various manufactures,
and particularly in the manufacture of sugar and of pottery, but its application to
the manufacture of hydraulic lime and cement is entirely new.
Any of the "filter presses" patented in France, or in other countries, may be
employed, in particular those of Needham and Kite, of Danek, of Trinks, of Messieurs
du Rieux and Roettger, as well as the press of Berlin, Godot Degoix and Combet.