An Improvement in Burning Portland Cement.
Year: 1892

page_text: Date of Application, 8th Mar., 1892
Complete Specification Left, 26th Nov., 1892-Accepted, 31st Dec., 1892
PROVISIONAL SPECIFICATION.
An Improvement in Burning Portland Cement.
I, JAMES WEST KNIGHTS of Sidney Street, Cambridge in the County of
Cambridge, Analytical Chemist do hereby declare the nature of this invention to be
as follows:-
In burning the material used in making Portland cement, the object is to obtain
a hard clinker which will not disintegrate or fall to dust when exposed to the
atmosphere. Any dust formed in the kilns very seriously diminishes the strength
of the cement, some forms of raw material are very apt to form dust. To prevent
this use common salt (chloride of sodium), the common salt is placed in the kiln
with the raw material and the fuel in layers, a layer of fuel a layer of raw cement
and a sprinkling of salt, and so on until the kiln is full. During the heating of the
kiln the salt is absorbed by the cement and prevents the formation of dust. The
quantity to be used varies slightly with different raw materials and is from half to
one per cent. or in some cases two per cent. calculated on the cement produced.
If the salt is incorporated with the raw material instead of being sprinkled in the
kiln it will not produce the same effect.
Chloride of potassium may be used instead of chloride of sodium with the same
effect, but I prefer the chloride of sodium because it is cheaper.
Dated this 7th day of March 1805
J. WEST KNIGHTS.
COMPLETE SPECIFICATION.
An Improvement in Burning Portland Cement.
I, JAMES WEST KNIGHTS of 1 Sidney Street, Cambridge, Analyst do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
In making Portland cement a mixture of chalk and clay in certain proportions, is
burnt in a kiln until it assumes a semi-vitrified condition and is then termed clinker.
To produce the best quality of cement the clinker should be hard and should not
fall to dust or disintegrate during the process of cooling, which it frequently does
to the great detriment of the resulting cement.
This disintegration of the clinker more frequently occurs with some raw materials
than others.
To prevent it I sprinkle in the kiln amongst the mixture of chalk and clay and
fuel a little chloride of sodium or common salt.
The chloride of sodium when a high temperature is reached, is converted into
a vapour which in contact with the silica of the clay is converted into silicate of
soda, the small quantity of silicate of soda thus produced protects the clinker and
prevents its disintegration, and by so doing very much increases the strength of
the cement produced.
The manner of using the chloride of sodium is very simple. When a kiln is
loaded in the usual way a layer of fuel is first placed at the bottom then a layer
of chalk and clay mixture, another layer of fuel and so on until the kiln is filled.
I use the chloride of sodium by simply sprinkling a little on each layer either by
hand or with a shovel so as to equally distribute it as nearly as possible throughout
the kiln. The quantity to be used is from about half of one per cent. to about
two per cent. of the total yield of clinker; that is, if a kiln yields twenty tons of
1 Price 8d1

page_text: clinker the quantity of salt to be used will be from two to eight hundred-weights,
the experience of the burners will tell them the actual quantity that gives the best
results, in the first instance the smaller quantity should be used and gradually
increased in succeeding kilns until the desired result is obtained.
The chloride of sodium may be dissolved in water and the solution thus formed
may be sprinkled on the materials either in the kiln or before loading into the kiln,
with the same effect.
Chloride of potassium or a mixture of sodium and potassium chlorides have the
same effect as chloride of sodium, but are more costly.
If the salt is incorporated with the chalk and clay mixture instead of being
sprinkled in the kiln as above described, it does not have the same effect, as it is
essential for the success of my process that the salt be applied superficially and not
to affect the whole body of the clinker.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed declare that what I
claim is:
1. The use of chloride of sodium or common salt in the burning of cement in
the manner described.
2. The use of alkaline chlorides for the purpose and substantially as described.
Dated this 25th day of November 1892.
JAMES WEST
VEST KNIGHTS.