Improvements in Treating the Liquors Resulting from the Manu- facture of Cellulose or Fibres by the Sulphite Process in order to obtain Useful Products therefrom.
Year: 1899

page_text: Date of Application, 4th Jan., 1899
Complete Specification Left, 28th Sept., 1899-Accepted, 4th Nov., 1899
PROVISIONAL SPECIFICATION.
Improvements in Treating the Liquors Resulting from the Manu-
facture of Cellulose or Fibres by the Sulphite Process in order to
obtain Useful Products therefrom.
I, CARL DANIEL Ekman, of 57), Old Broad Street, in the City of London,
Chemical Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to the treatment of the liquors resulting from the manu-
facture of cellulose or fibres from wood or other fibrous plants by boiling under
pressure with a sulphite solution or a solution containing sulphurous acid, and
a base such as potash, soda, magnesia or lime in order to obtain sizing and
stiffening materials or other useful products.
According to this invention the said liquors which are generally called sulphite
liquors are treated with oxide of zinc at the ordinary temperature or at an
elevated temperature as may be desired. The oxide of zinc probably forms a
chemical combination with substances in the sulphite liquor and after the proper
treatment and evaporation a concentrated thick liquor is obtained, suitable for
the manufacture of "dextròne" as described in my Patent Specification No. 20036
of 1893 and for other purposes and it will have the advantages that the dextrono
will, when properly prepared, be of better quality and color than if manufactured
from liquor treated in the ordinary way.
The oxide of zinc can be replaced by a suitable zinc salt which is soluble in
the liquor and from which by addition of a suitable base oxide of zinc is precipi-
tated. Sulphate of zinc has given very satisfactory results and has the advantago
of cheapness as compared with most other zinc salts.
Carbonate of zinc, if prepared chemically, can also be used instead of oxide
of zinc, but it acts much more slowly and greater weight is necessary to obtain
the same results and it generally comes more expensive than the oxide; therefore
in practice I prefer the oxide of zinc.
One way in which this process can be carried into effect is to place the sulphite
liquor in an agitator tank lined with lead or made of an acid resisting material
and to heat the liquor by a lead coil or other suitable arrangement to about
80° C. to 90° C.-say 175° F. to 195° F. and then add an excess of oxide of
zinc in powder under agitation, the heating being continued for four to five hours
until the liquor has been saturated with the oxide of zinc and shows a strong
alkaline reaction on litmus paper. The liquor is separated from the precipitate
by settling or filtering or by first partly settling and then clearing by filtration.
This clear liquor is now evaporated, care being taken that its colour does not
suffer by using a too high temperature or from other causes; I therefore prefer
to evaporate the prepared liquor in vacuum.
A smaller amount of oxide of zinc than is necessary to saturate the liquor may
be used for some purposes, as even a very small amount generally improves the
colour of the products obtained from the liquor and especially so of the dextrone,
but this as well as the time and degree of heating depend much on the special
purposes for which the liquor is intended but for the manufacture of dextrone
I have obtained the best results by heating the liquor to about 90° C.-195° F.-
adding an excess of oxide of zinc and continuing the heating under agitation for
four to five hours

page_text: Dextrone prepared from the thick evaporated liquor will have a much brighter
and lighter colour, if the different processes have been carried out with the
necessary experience and skill, than if the dextrone is manufactured in the
ordinary way, as described in my Patent Specification No. 20036 of 1893.
If for the sake of economy it is desired not to use as much oxide of zinc as will
saturate the sulphite liquor, a smaller quantity will still be an improvement and
if for the sake of evaporation or any other cause the liquor is required to be
alkaline, this can be effected by adding the necessary quantity of magnesia, soda
_ash or some other suitable base until the desired alkaline reaction is obtained.
Another way of treating the sulphite liquor is to pass it through a layer of
oxide of zinc until the liquor gets saturated, which can be done cold by passing the
liquor through the layer of oxide of zinc once or oftener. The clear saturated
liquor is evaporated as usual and used for the manufacture of dextrone or for
other purposes.
The oxide of zinc being a somewhat expensive material it is of advantage
with the view of cheapening the products to partly replace the oxide of zine by
a cheaper oxide and this can be done very accurately and cheaply by adding
more or less soda ash to the sulphite liquor before it passes through the oxide
of zinc. A convenient way to do this is to heat the liquor by a lead steam coil
in an agitator tank, as above described to about 40° C. to 50° C. or say about
100° F. to 125° F. under agitation until the liquor shows a nearly neutral reaction
on very sensitive blue litmus paper and then to pass this so prepared liquor
through oxide of zinc until it is saturated and then to treat as described above.
The results I have obtained in this way are not as good as when oxide of zinc
alone has been used, but still they are sufficiently good for many purposes.
The oxide of zinc can also be replaced by a soluble salt of zinc, which by
addition of a suitable base gives a precipitate of oxide of zinc, but different salts
give more or less satisfactory results. For practical purposes I have found
sulphate of zinc preferable, as it is comparatively cheap and has given good
results and as a base, a pure commercial soda ash answers very well. Chloride
of zinc has not given satisfactory results and the results obtained with nitrate
of zinc have not been so good as when I have used the sulphate.
In carrying out this process I dissolve the zinc salt in the sulphite liquor,
which is heated in an agitator tank with a steam lead coil, as above mentioned,
and then the soda ash or some other suitable base is added until a decided alkaline
reaction is obtained by litmus paper. The liquor is if necessary cleared and then
evaporated as above described and it is then ready for the manufacture of dextrone
or other purposes.
The quantity of salt used varies greatly according to circumstances, as for
example cheapness, the kind of liquor to be treated and the purposes for which
the product is intended, but I generally use a quantity representing from one-
tenth per cent. to two per cent. oxide of zinc.
AL
Jan1900
COMPLETE SPECIFICATION.
Improvements in Treating the Liquors Resulting from the Manu-
facture of Cellulose or Fibres by the Sulphite Process in order to
obtain Useful Products therefrom.
I, CARL DANIEL EKMAN, of 571, Old Broad Street, in the City of London, 5
Chemical Engineer, do hereby declare the nature of this invention and in what

page_text: manner the same is to be performed, to be particularly described and ascertained
in and by the following statement: →
"
The object of this invention is to obtain useful products such for example
as sizing or stiffening materials from the liquors, generally called "sulphite
liquor, resulting from the manufacture of cellulose or fibres from wood or other
fibrous plants by boiling under pressure with a sulphite solution or a solution
containing sulphurous acid and a base such as potash, soda, magnesia or lime.
According to this invention the sulphite liquor is treated with oxide of zinc
either at the ordinary temperature or at an elevated temperature The oxide
of zinc may either be introduced into the sulphite liquor in the form of oxide
or I may use instead thereof a zino salt which is soluble in the sulphite liquor
(Buch for example as sulphate of zinc) together with a suitable base such for
example as soda ash, by which the oxide of zinc will be precipitated. Chemically
prepared carbonate of zine can also be used but it acts slower than oxide and offers
no special advantages. The oxide of zinc appears to form a chemical combination
with some substances in the sulphite liquor, and after evaporation a thick concen-
trated liquor is obtained which can be utilised for sizing or stiffening purposes
or in the manner described in my Patent No. 20036 of 1893 for the manufacture
of a product resembling or having properties similar to those of dextrine. This
product when made with liquor treated according to the present invention is of
better quality and color than that obtained from liquor treated as described in
my said former patent.
One way in which the present invention can be carried into effect is to place
the sulphite liquor in an agitator-tank lined with lead or made of an acid resisting
material and to heat the liquor by a lead coil or other suitable arrangement to
about 80° C. to 90° C. and to then add an excess of oxide of zinc in powder
under agitation, the heating being continued for four to five hours until the
liquor has been saturated with the oxide of zinc and shows a strong alkaline
reaction on litmus paper. The liquor is separated from the precipitate by settling
or filtering or by first partly settling and then clearing by filtration. This
clear liquor is now evaporated, care being taken that its colour does not suffer
by using a too high temperature or from other causes; I therefore prefer to
evaporate the prepared liquor in vacuum.
A smaller amount of oxide of zinc than is necessary to saturate the liquor may
be used for some purposes, as even a very small amount generally improves the
colour of the products obtained from the liquor, but this as well as the time and
degree of heating chiefly depend on the special purposes for which the liquor
is intended.
If for the sake of economy not enough oxide of zinc has been used to saturate
the liquor, but for the sake of evaporation or for any other cause it is desired
to have an alkaline liquor the necessary quantity of a suitable base, as magnesia
or soda, is added.
Another way of treating the sulphite liquor is to pass it through a layer of
oxide of zinc once or oftener until the liquor gets saturated. The clear saturated
liquor is then evaporated as usual and can be used for the manufacture of the
dextrine-like product described in my former patent or for other purposes.
Further for the sake of economy the oxide of zinc may be partly replaced by
a cheaper oxide and this can be done by adding soda ash to the sulphite liquor
before it passes through the oxide of zinc. A convenient way to do this is to
heat the liquor by a lead steam coil in an agitator-tank as above described to
about 40° C. to 50° C. under agitation until the liquor shows a nearly neutral
reaction on very sensitive blue litmus paper and then to pass this so prepared
liquor through oxide of zinc until it is saturated. The results I have obtained
in this way are not as good as when oxide of zinc alone has been used, but still
they are sufficiently good for many purposes.
When I employ a zinc salt instead of oxide of zinc I dissolve the zinc salt in

page_text: the sulphite liquor, which is heated in an agitator tank with a steam lead coil,
as above mentioned, and I then add soda ash or some other suitable base until
a decided alkaline reaction is obtained by litmus paper.
The quantity of salt used varies greatly according to circumstances, as for
example cheapness, the kind of liquor to be treated and the purposes for which
the product is intended, but I generally use a quantity representing from one-
tenth per cent. to two per cent oxide of zinc.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The herein described process or method of treating sulphite liquor which
consists in submitting said liquor to the action of oxide of zinc, whereby a chemi-
cal combinaton between said oxide and some substances in said liquor is formed,
and said liquor is thereby rendered suitable after evaporation for sizing, stiffening
or other purposes.
2. The herein described process or method of treating sulphite liquor which
consists in first dissolving a zinc salt in said liquor and in then converting said
zinc salt in said liquor into oxide of zinc by the addition of a base for the purpose
set forth.
Dated this siɩn day or september 1099.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.