Improvements in the Treatment of the Recovered Ash of Paper Mills.
Year: 1889

page_text: Date of Application, 4th Apr., 1889
Complete Specification Left, 4th Jan., 1890-Accepted, 8th Feb., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Treatment of the Recovered Ash of Paper
Mills.
We, JOSIAH WYCKLIFFE KYNASTON of Kensington, in the City of Liverpool, and
JAMES SUTHERLAND of Ballyclare in Ireland, Manufacturing and Analytical Chemists
respectively, do hereby declare the nature of this invention to be as follows :-
In the manufacture of paper, the material employed, whether rags, esparto, straw
or woody or other fibre, is boiled in solution of caustic soda under pressure, and when
the material is sufficiently softened and disintegrated, the liquor is drained away.
This liquor contains all the soda used in the operation, largely in the caustic condition
in which it was used, but also largely in combination with resinous and other organic
matter and with silica and alumina extracted from the fibre. It is usual now in
nearly all paper works, to boil down these liquors, and to dry and calcine the residue
in a furnace so as to burn off the organic matter and recover the soda for use over
again. This recovered soda ash, consisting mostly of carbonate of soda contains also
silicate and aluminate of soda to the extent of 15 to 20 per cent. of the whole soda
present. This silicate and aluminate of soda are not only themselves valueless as
detergents, but their presence seriously impedes the action upon fibrous materials of
the causticised solution and it becomes necessary to use quantities of either fresh soda
ash or caustic soda largely in excess of the quantity which should be required to
replace the mechanical losses.
Now our invention consists in a mode of treatment of solutions of recovered ash, by
which the injurious silicate and aluminate are decomposed, the silica and alumina aro
removed from the solutions and the soda which had been combined with these
substances becomes effective for the required purpose.
We accomplish this by the addition to the solution of recovered ash, of a sufficient
quantity of bicarbonate of soda to convert the caustic soda present into monocarbonate
(the bicarbonate used being itself reduced to the same condition) and to precipitate
the alumina and silica which under these conditions combine together and become
insoluble. After the addition of the bicarbonate the solution is boiled for from a
quarter to half an hour. Lime is then added and the causticising process carried out
in the usual manner.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Patent Agents for the Applicants.
Improvements in the Treatment of the Recovered Ash of Paper
Mills.
We, JOSIAH WYCKLIFFE KYNASTON of Kensington in the City of Liverpool and
JAMES SUTHERLAND of Ballyclare in Ireland, Manufacturing and Analytical Chemists,
respectively, 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:-
In the manufacture of paper by one well known process, and the process most
commonly used, the fibrous material employed, whether rags, esparto, straw or woody
or other fibre, is boiled in solution of caustic soda under pressure, and when the
material is sufficiently softened and disintegrated, the liquor is drained away.
This

page_text: .
liquor contains all the soda used in the operation, largely in the caustic condition in
which it was used, but also largely in combination with resinous and other organic
matter and with silica and alumina extracted from the fibre. It is the usual practice
now in nearly all paper works to boil down the liquor and to dry and calcine the
residue in a furnace so as to burn off the organic matter and recover the soda for use
over again.
This recovered soda ash, consisting mostly of carbonate of soda, contains also
silicate and aluminate of soda to the extent of 15 to 20 per cent. of the whole soda
present. This silicate and aluminate of soda are not only themselves valueless as
detergents or disintegrating agents, but their presence seriously impedes the action
upon fibrous materials of the causticised solution, and it becomes necessary to use
quantities of either fresh soda ash or caustic soda largely in excess of the quantity
which should be required to replace the mechanical losses.
It is true that when the solution of recovered ash is causticised in the usual manner
by means of lime, much of the silica and some of the alumina combine with lime and
become insoluble. But the products are not simply silicate and aluminate of lime :
they are complex salts containing also considerable quantities of soda, which is thus
lost from the process and requires to be replaced by fresh soda ash or caustic soda.
The soda thus lost probably exceeds the losses of this substance in all the other stages
of the manufacture.
Now our invention consists in a mode of treatment of solutions of the recovered
ash in paper mills, by which the injurious silicate and aluminate of soda are
decomposed, the silica and alumina are removed from the solution in combination with
each other, and the soda which had been combined with these substances is liberated
and becomes effective for the required purpose.
an
We accomplish this by the addition, to the solution of recovered ash, of a sufficient
quantity of bicarbonate of soda or of other carbonate of soda (or potash) containing
excess of carbonic acid beyond that necessary to constitute monocarbonate to
convert the caustic soda present into monocarbonate (the bicarbonate itself being
reduced to the same condition) and a further quantity sufficient to convert into mono-
carbonate the soda which is in combination with silica and alumina. The two last
named substances thus combine together and become insoluble. After the addition of
the bicarbonate, the solution is boiled for from a quarter to half an hour. Lime is then
added, and the causticising process carried out in the usual manner. If the muddy
mixture produced by the addition of the bicarbonate, after being boiled, be allowed to
stand at rest, the insoluble compound of silica and alumina falls out, and the clear
purified solution may be drawn off and causticised. But this is not essential to the
successful working of the process, as the compound of silica and alumina, after having
been formed in the solution, is not decomposed by treatment with lime, but falls down
with the carbonate of lime and is thus got rid of.
The liquors obtained by dissolving paper-makers' recovered ash vary considerably
according to the nature of the fibrous material which has been treated, liquors from
straw boiling, for instance, being much more contaminated than those from esparto.
It is not therefore possible to state the exact proportion of bicarbonate required to be
used in all cases, but this may be easily ascertained by the operator in a few minutes
by the following mode of procedure:-
A portion of the liquor to be treated, say a half pint, is taken, and also a weighed
quantity of the bicarbonate to be used. The latter is then added to the liquor in
small portions at a time (stirring well after each addition) first, until a permanent
precipitate or muddiness is produced, and then until a precipitate is no longer pro-
duced, which is ascertained by filtering a little of the muddy mixture and adding a
little bicarbonate to the clear fluid. The weight of the bicarbonate required for the
half pint of liquor is then ascertained by weighing that which remains unused, and by
a simple calculation, the quantity of bicarbonate required for the batch of liquor to be
treated is found.

page_text: Having now particularly described and ascertained the nature of our said inven-
are aware that
tion, and in what manner the same is to be performed, we
carbonic acid, more or less pure, has been and is used by alkali manufacturers for
removing silica and alumina from soda liquors, but this process is quite inapplicable in
paper mills and we make no claim to the use of this acid per se, but we declare that
what we claim as our invention is :-
The treatment of solutions of paper-makers' recovered ash with bicarbonate or
other carbonate of soda (or potash) containing an excess of carbonic acid beyond
that necessary to constitute monocarbonate, so as to render insoluble the silica and
alumina contained in such liquors, in the manner substantially as described.
2nd this 2nd das
1800
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester, and London, Patent Agents.