AN IMPROVED PROCESS FOR CONVERTING INTO CAUSTIC LIME SPENT LIME WHICH HAS BEEN USED IN THE PURIFICATION OF ILLUMINATING GAS
Year: 1878

page_text: LETTERS PATENT to William Mead, of Lawrence Pountney Hill, in the City
of London, at present residing in Paris, France, for the Invention of "AN
IMPROVED PROCESS FOR CONVERTING INTO CAUSTIC LIME SPENT LIME WHICH
HAS BEEN USED IN THE PURIFICATION OF ILLUMINATING GAS." A communi-
cation from Asa W. Wilkinson, of the City and State of New York, United
States of America.
Sealed the 24th December 1878, and dated the 24th June 1878.
PROVISIONAL SPECIFICATION left by the said William Mead at the Office
of the Commissioners of Patents on the 24th June 1878.
WILLIAM MEAD, of Lawrence Pountney Hill, in the City of London, at present
residing in Paris, France. "AN IMPROVED PROCESS FOR CONVERTING INTO CAUSTIC
LIME SPENT LIME WHICH HAS BEEN USED IN THE PURIFICATION OF ILLUMINATING
GAS." [A communication from Asa W. Wilkinson, of the City and State of New
York, United States of America.]
This Invention relates to an improved process for converting lime that has been
used in the purification of illuminating gas into caustic lime.
In carrying the said Invention into practice I first press the spent lime into bricks,
which is effected by the same means that are employed for formning ordinary bricks;
I then place these bricks in a convenient kiln, and subject them to increasing heat,
sufficient to drive off the moisture, ammonia, carbonic acid, and sulphur which the
lime has absorbed in purifying the gas.
The difficulty heretofore experienced in re-burning lime of this character has
arisen from the powdery character of the lime preventing the flames from permeating
the mass, which action is necessary in order to drive off the substances named. By
pressing the lime into bricks this difficulty is avoided.
In the said improved process I make use of an ordinary brick press, which may
be operated either by hand or power.

page_text: The lime is taken just as it is delivered from the purifying boxes, and is pressed
into a convenient form and made sufficiently hard so that the bricks may be piled
one upon another, as is customary in piling clay bricks in the kiln. Fire is now
started in the fire-box, and the bricks are burned as clay bricks are burned. The
length of time necessary to drive off the moisture, ainmonia, carbonic acid, and
sulphur depends somewhat upon the size of the kiln and the intensity of the heat.
The bricks will shrink in size as they lose carbonic acid, sulphur, and the like,
and from such shrinkage it can be ascertained about when the kiln is burned; from
twenty to thirty-six hours should be sufficient to accomplish the object. By
adopting this process the lime may be used an indefinite number of times, as by
each burning it is converted into caustic lime, only requiring slacking to convert it
to the hydrate and fit it for the purifying boxes again, or for other purposes for
which caustic lime is used.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Mead in the Great Seal Patent Office on the 24th December
1878.
WILLIAM MEAD, of Lawrence Pountney Hill, in the City of London, at present
residing in Paris, France. "AN IMPROVED PROCESS FOR CONVERTING INTO CAUSTIC
LIME SPENT LIME WHICH HAS BEEN USED IN THE PURIFICATION OF ILLUMINATING
GAS." A communication from Asa W. Wilkinson, of the City and State of New
York, United States of America.
This Invention relates to an improved process for converting lime that has been
used in the purification of illuminating gas into caustic lime.
In carrying the said Invention into practice I first press the spent lime into bricks
or blocks. This operation is effected by the same means that are employed for.
forming ordinary bricks; I then place these bricks in a convenient kiln, and subject
them to increasing heat sufficient to drive off the moisture, ammonia, carbonic acid,
and sulphur which the lime has absorbed in purifying the gas.
The difficulty heretofore experienced in re-burning lime of this character has
arisen from the powdery character of the lime, whereby the permeating of the mass
by the flames which is necessary in order to drive off the aforesaid substances is
prevented. By pressing the lime into bricks this difficulty is avoided.
In the said improved process I make use of an ordinary brick press, which may
be operated either by hand or other power.
The lime is taken just as it is delivered from the purifying boxes, and is pressed
into a convenient form and made sufficiently hard to allow the bricks to be piled
one upon another, as is customary in piling clay bricks in the kiln. Fire is now
started in the fire-box, and the bricks are burned in the same manner as clay bricks.
The length of time necessary to drive off the moisture, ammonia, carbonic acid, and
sulphur depends somewhat upon the size of the kiln and the intensity of the heat.

page_text: The said bricks or blocks will shrink in size as they lose carbonic acid, sulphur,
and the like, and from such shrinkage it can be ascertained when the burning is
finished; from twenty to thirty-six hours should be sufficient to accomplish this
object. By adopting this improved process the lime may be used an indefinite
number of times, as by each burning it is converted into caustic lime, only requiring
slacking to convert it into the hydrate and fit it for the purifying boxes again, or
for other purposes for which caustic lime is used.
Having thus fully described my said Invention, and the manner of performing
the same, I wish it understood that I claim the process of converting the spent lime
of gasworks into caustic lime by first pressing it into bricks or blocks and then
subjecting the same to sufficient heat in a kiln to drive off the moisture, ammonia,
carbonic acid, sulphur, and other matters with which it is combined, thereby
reducing it to caustic lime, and rendering it fit for further use in purifying gas or
for other purposes for which lime is used, as above set forth.
In witness whereof, I, the said William Mead, have hereunto set my hand and
seal, this Nineteenth day of December, in the year of our Lord One thousand
eight hundred and seventy-eight.