Year: 1886

page_text: i.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co, Patent Agents,
Southampton Buildings, in the County of Middlesex, 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 has for its object to manufacture sulphuric acid in such a manner
that hydraulic cement is obtained as a bye-product.
Hydraulic or Portland cement is usually manufactured by mixing together clay
and carbonate of lime in such proportions that after calcination the resulting
compound will contain about 62 parts of lime, 28 parts of silicic acid and 10 parts
of alumina, by weight. During the process of calcination the carbonic acid
contained in the carbonate of lime is expelled and the silicic acid combines with.
the bases and forms therewith silicates of lime and alumina which are afterwards
reduced to powder and known as hydraulic or Portland cement. The carbonic
acid which is expelled during the process of calcination has no commercial value
and is allowed to escape into the air.
The said invention consists in calcining a mixture of clay and sulphate of
lime so as to obtain sulphuric acid as hereinafter set forth.
In practising my invention, I mix together gypsum or sulphate of lime.and clay
in the proportion of about 1266 pounds of gysum to 400 pounds of clay. I prefer
to pulverize the gypsum, and dry the clay and pulverize the same, then intimately
mix the pulverized gypsum and clay and add a small quantity of water, and mould
the mixture into blocks substantially in the.manner practised in making Portland
cement from carbonate of lime and clay by the well known, dry process. I then
subject this mixture to calcination in a suitable kiln. At the high degree of heat
which is maintained during the process of calcination the silicic acid contained in
the clay expels the sulphuric acid contained in the sulphate of lime and combines
with the lime and alumina and produces therewith silicates of lime and alumina,
which upon being reduced to powder, are in every particular a hydraulic or
Portland cement.
The sulphuric acid is expelled during this process of calcination either in the
form of vapour, or it is decomposed and forms sulphurous acid and oxygen; or the
escaping gas is a mixture of vaporized sulphuric acid, sulphurous acid and oxygen,
according to the degree of beat which is maintained during the process of calcination

page_text: and which may vary somewhat at different times owing to differences in the
quantity or quality of fuel employed, strength of draught &°.
The gases escaping during the process of calcination are cooled in suitable
chambers or passages lined with lead in which the sulphuric acid is condensed
and collected. The sulphurous acid, if any, is converted into sulphuric acid in
the ordinary manner by means of steam and nitric acid. The sulphuric acid so
obtained is then concentrated or further treated. in any usual manner practised in
the manufacture of sulphuric acid.
f
The mixture of gypsum and clay above specified produces about 580 pounds
of sulphuric acid and 711 pounds of hydraulic or Portland cement from every
1666 pounds of the mixture, the balance being moisture which is expelled.
It will be readily understood, as the cost of the sulphate of lime is about the
same as that of carbonate of lime that the cement obtained as a bye-product in the
manufacture of sulphuric acid costs considerably less than that obtained according
to the old method in which carbonate of lime is employed.
In practising this invention any suitable kiln in which, the process of calcination
can be carried out may be employed, and any ordinary apparatus may be used for
recovering the sulphuric acid.
The condensing and converting chambers are connected with the top of the kiln
by a suitable flue and the waste gases are discharged from the condensing or
converting chambers by a stack or chimney or a suitable fan which maintains a
proper draught through the kiln and chambers.
The proportions herein specified are found to be well calculated to produce the
desired results, but they may be varied in .accordance with the nature of the
gypsum-rock and clay employed within certain limits without changing the general
results. If the proportion of clay used be too great the cement will be of an
inferior quality, but the sulphuric acid contained in the sulphate of lime will be
driven off and recovered. If an excess of gypsum be used, the lime contained
therein is in excess of the true combining proportions with the silicic acid, and the
sulphuric acid will not all be driven off and the resulting cement will be inferior
in quality by reason of the presence of sulphate of lime, although
a small per-
centage of the latter may be present without exerting any specially deleterious
influence.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed as communicated to
me by my foreign correspondent, I declare that what I claim is :-
First. The herein described method of manufacturing sulphuric acid, which
consists in calcining a mixture of clay and sulphate of lime, substantially in the
proportions specified, and recovering the sulphuric acid which is driven off,
substantially as set forth..
Second. In the manufacture of sulphuric acid, the herein described method of
producing hydraulic or Portland cement as a bye product, which consists in calcining
a mixture of clay and sulphate of lime in the proportions to form a hydraulic or
Portland cement substantially as set forth.
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