Process and Apparatus for the Manufacture of Dry Calcium Hydroxide.
Year: 1888

page_text: Date of Application, 2nd Jan., 1888
Specification Accepted, 24th Feb., 1888.
COMPLETE SPECIFICATION.
Process and Apparatus for the Manufacture of Dry Calcium
Hydroxide.
I, JACOB PFEIFFER of No. 42 Barbarossa strasse Kaiserslautern in the German
Empire Manufacturer 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 :—
My invention relates to the conversion of caustic lime (Calcium oxide Ca, O) into.
hydrate of lime (Calcium hydroxide H, Ca O₂) by treating the caustic lime with water
while enclosed in a heated receptacle whereby it is converted into hydrate while under
considerable pressure.
For this purpose I employ one or more (according to the quantity of hydrate to be
produced) metallic cylindrical receptacles A, such as shewn in cross section,
longitudinal section plan and end view respectively at Figs. 1, 2, 3 and 4 in the
accompanying drawing, into which are introduced the semicylindrical carriages B
charged with the broken lime (Calcium oxide Ca O). The receptacle A is connected
by a tube C with a safety valve, a shut-off valve with discharge pipe, and a pressure
gauge. At the bottom it is provided with a cock for discharging water.
receptacle also communicates with a water supply pipe E which branches inside A
into two pipes F and G that are finely perforated, so that the water required for
hydration enters in the form of a uniformly divided spray over the lime in the
carriage B.
The
This carriage serves three purposes; firstly it enables the charge of the cylinder to
be easily and rapidly introduced and removed; secondly, by removing the entire
charge of pulverulent hydrate of lime in a body without disturbing it, the formation
of line dust, which is so injurious to the workmen, is entirely prevented; thirdly, it
prevents the hydrate of lime from absorbing more water than is necessary for the
hydration, by taking up water of condensation, and thus becoming moist, this being
effected as follows: The steam formed in consequence of the increase of temperature
due to the process of hydration, can only condense upon the sides of the cylinder A,
from which the water can only trickle down into the space between A and B, and
consequently cannot come in contact with the hydrate of lime in the carriage. The
accumulated water of condensation is discharged through the cock K.

page_text: The process is as follows :
The carriage or carriages B are filled with the burnt. lime, broken into pieces of
about the size of a nut, to a depth of from. 6 ins. to 8 ins., and is or are introduced into
the open end of the cylinder A. This is then closed steam tight by a cover H and the
cock J is opened so as to admit a measured quantity of water, previously determined
.according to the quantity of lime to be treated, the water being introduced either by
gravity from an elevated tank or by a force pump. The water flows in a finely
divided spray from the pipes F and G over the lime, producing the hydration thereof.
The pressure will, during this process rise to a degree depending upon the proportion
between the quantity of lime and the capacity of the cylinder A, such as to from 4
to 5 atmospheres. The hydrated lime is allowed to remain under this pressure for
about half an hour..
In order to prevent the condensation of steam formed by the rise of temperature,
the cylinder A is heated either by direct external fire heat, or by hot combustion
gases, or by a steam jacket supplied with fresh or exhaust steam.
At the expiration of half an hour, the steam is let off by opening the shut-off cock
on the pipe D, and the condensed water is also discharged from the bottom of A
through cock K.
In order to allow the surplus water taken up by the lime to be given off in the form
of steam, it is allowed to stand for another half hour in the cylinder A the door of
which is closed but which has the valve D open so as to communicate with the open
air. At the end of this time the hydrated lime, perfectly dry and pulverised, is
removed in the carriage B. from the cylinder A, and is utilised in any desired
nanner.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same. is to be performed, I declare that what
I claim is `
1. The process of converting burnt lime (Calcium oxide Ca O) into hydrate of
lime (Calcium hydroxide H, Ca O,) whereby the burnt lime, contained in a moveable
receptacle, is enclosed in a chamber and is there treated with the requisite amount of
water for its hydration while subject to pressure, with prevention of the formation of
dust, substantially as herein described.
2. Apparatus for carrying out the process referred to in the preceding claim,
consisting of a receptacle or chamber A heated by direct fire, heat or by other means,
a moveable receptacle or carriage B for containing the lime to be treated, and, a water
supply pipe E with perforated branches situated over the carriage B for distributing
the water in the form of spray over the charge of lime therein, substantially as herein
described.
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Dated this 2nd day of January 1888