Year: 1887

page_text: Date of Application, 26th Sept., 1887
Complete Specification Left, 26th June, 1888
Complete Specification Accepted, 3rd Aug., 1888
I, WILLIAM PHILLIPS THOMPSON F.C.S. M.I.M.E. of the Agency for Foreign Patent
Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester, both in the County
of Lancaster, and 323, High Holborn, in the County of Middlesex, "Civil Engineer, do
hereby declare the nature of this invention to 'be as follows:-
The process consists essentially in the application of the calcareous deposits or lime
mud constituting a bye-product of the manufacture of soda or sulphate cellulose to the
neutralization of acid sulphate of soda, and the simultaneous recuperation of the alkali
salts remaining in the calcareous mud through incomplete washing, such as carbonate
of soda, caustic soda etcetera, which effect the precipitation and consequent removal of
the iron, clay, lime, magnesia, etcetera.
In the manufacture of soda or sulphate cellulose the liquor obtained in the boiling
process contains in suspension particles of wood, and has a dark brown color. It will
be hereafter called the brown liquor. It is well known that this liquor is at present
evaporated and made red hot, that is fused for the purpose of transforming it into
carbonate of soda etcetera, and regenerating the alkaline salts. Water is added to the
mass that has thus been submitted to red heat and melted, and to facilitate the
transformation of the carbonate of soda into caustic soda, the solution is boiled with
burnt lime, that is to say, is rendered caustic. The rendering caustic of the liquor,
and the washing out of the calcareous mud takes place "methodically" in a series of
large tanks or vats provided with stirring devices.
The calcareous deposit thus obtained, which contains the lime as carbonate of lime,
is left to settle down, and after many washings allowed to run away. It contains
according to the more or less complete washing '0.5 to 1 per cent of alkaline salts,
which, like the Time, 'are lost and waste products.
The unavoidable losses of alkaline salts, which have hitherto taken place in the

page_text: manufacture, have been compensated by the addition of soda. Of late years neutral
sulphate of soda has been applied for this purpose according to Dahl's method. The
acid sulphate of soda, which finds almost no application in the industry, and which is
a bye or waste product of the manufacture of nitric acid, where it is obtained in large
quantities, could not, up to the present, be employed for this purpose, because the free
or unsaturated sulphuric acid neutralizes partially, the caustic alkalies, and thereby
renders them ineffective in the boiling process.
The manufacturers of cellulose were, owing to that, compelled to buy from soda
manufacturers, neutral puro sulphate of soda, which, when it contains 95 to 98 per cent
of pure sulphate of soda costs 5 or 6 shillings per 100 kilogrammes, whilst the acid
sulphate of soda containing 70 to 75 per cent of neutral sulphate of soda, can be
obtained for shilling and less.
According to this process it is possible for cellulose manufacturers to utilize the acid
sulphates of soda for their purpose in a simple manner, by using it to transform the
calcareous mud into gypsuin, a well known manure, and recover the unwashed alkalies
out of the calcareous mud.
The mode of working is as follows:-
After the calcareous mud, used in rendering caustic the boiled liquor, has been
washed in the stirring vat, and the last wash water removed, (fresh) water is added
to this mud, and the stirring appliance put in motion.
A basket made of iron bars is hung up in the stirring vat. This basket takes up
solid substances, which cannot fall through, whilst the liquor can come into it from
the outside.
A weighed quantity of acid sulphate is introduced gradually in this basket, whilst
the water, and the stirred up calcareous mud are constantly being brought into contact
with this salphato. The sulphate gets dissolved in the water, and is neutralized
by the lime in suspension, whilst carbonic acid is being evolved in an active manner.
The dissolution and decomposition are accelerated by application of heat either
through heating pipes, or by steam acting directly.
The quantity of sulphate to be added is calculated from the amount of acid sulphate
of soda contained in the sulphate, and from the quantity of carbonate of lime according
to the following equation:
2 Na SO, H + Ca CO₂ = Na, SO + Ca SO. + CO2 + H₂ O
According to this, 100 parts in weight of acid sulphate of soda require 41.6 parts
in weight of carbonate of soda.
The same equation shows that in the same process gypsum and carbonic acid are
produced besides neutral sulphate of soda. The gypsum can be used as manure, the
carbonic acid can eventually be collected and liquefied.
As the calcareous deposit contains almost always large quantities of iron, clay,
magnesia, etcetera, the latter get transformed into soluble sulphates in the neutralization
process. These sulphates must be removed, as they would exert an injurious action
in the latter process. This takes place already partly in the said process, through the
caustic alkalies existing in the calcareous mud. The separation of these metals is
completed when, towards the conclusion of the operation, the whole mass is stirred
and boiled for a quarter of an hour by means of high pressure steam. It is also good
for the purpose in view, to add to the above a good quantity of raw lye, that has not
yet been rendered caustic, and which contains much carbonate of soda.
The carbonate of soda and the caustic soda, sulphide of soda (Schwefelnatron) etcetera
precipitate the lime and magnesia in the state of carbonates, the iron partly as sulphide
of iron and partly as hydrated oxide of iron, the aluminium as hydrated clay; the
alkaline salts are transformed into sulphate of soda as expressed by the following
equations :-
--

page_text: ascertain whether the precipitation is complete a test is made by filtering a little
quantity of the liquid, and testing the filtered matter with carbonate of ammonia.
The liquor which is at the top, is an almost pure chemical solution containing neutral
sulphate of soda ready for immediate use. The way of operating is as follows:-
:―
The solution can be let flow into the reservoirs destined to receive the brown liquor,
at the same time as the latter leaves the pan after the boiling is over; the brown
liquor and solution are then evaporated etcetera. It is, however, more to the purpose
to proceed as follows: In order to avoid the evaporation of the greatest part of the
liquor, which flows along with the solution of Glauber Salts into the brown liquor,
this solution is used instead of water, for the purpose of diluting the mass that has
been made red hot and fused. The same (the solution) is added to the boiled lye and
undergoes with it the boiling operation. This process can, of course, be modified in
various ways:
Thus instead of the calcareous deposit, common burnt or quick lime or other basic
or alkaline substances can be used for the neutralization; for instance, the boiled lye
itself or the brown liquor. If the two latter are taken (the boiled lyo or the brown
liquor), the process becomes thereby, much simpler.
If the sulphate is added to the boiled lye, the free or half combined sulphuric acid
will neutralize one part of the caustic lye, and render it inactive in the boiling process.
But this injurious action of the sulphuric acid can be easily obviated. It is only
necessary to take care that, by the use of a concentrated lye, the solution which is
produced after the addition of the sulphate, contains still a sufficient quantity of
free alkali.
If, for instance, 16 cubic metres of lye are employed usually in the boiling process,
and that this lye has an alkalinity of 6 per cent (calculated after the soda), and that
3 centners only of neutral sulphate of soda are usually necessary to make up for the
losses in alkalies, it will be necessary on employing acid sulphate of soda containing
70 per cent neutral sulphate of soda, and 30 per cent free sulphuric acid, to use
4.28 centners of sulphate. These 4.28 centners of sulphate contain 1.28 centners of
free sulphuric acid, which, according to the following proportion neutralize
081 centners of soda

page_text: As the sulphate obtained in the manufacture of nitric acid is frequently mixed
mechanically with impurities, it is good for the purpose in view, to dissolve it in water
before adding it to the boiled lye, or to the brown liquor, and to filter it. It is also
advisable to divide the sulphate into two halves, one of which is added to the brown
liquor, and the other to the caustic lye. Thereby a separation in the brown liquor,
and an excess of sulphate of soda in the boiled lye, aro avoided.
The iron, clay, and other metallic salts contained in the impure acid or neutral
Glauber salt obtained as lye products in the manufacture of zinc and copper can bo
removed in the same manner as that employed to render harmless the same salts in
the acid sulphate of soda. The Glauber Salt derived from the above manufactures of
zinc and copper, can thus be utilized in the manufacture of cellulose.
The salt is brought along with the causticising lime into the above mentioned
basket of a stirring vat, which vat is filled with the so-called raw lye, that is to say,
boiled lye that has not been made caustic. The salt dissolves, and at the same time,
the injurious metallic salts are separated by the alkaline lye, and settle at the bottom
with the calcareous mud and other impurities, such as dust, sand, etcetera. Or the
salt can be dissolved by itself in water, or in another liquor obtained in the manufacture
(such as wash lye etcetera), soda or boiled lye added to it, and the solution boiled and
filtered. Or the said solution of neutral sulphate of soda is used in the manner
described in the foregoing.
Dated this 24th day of September 1887
WM. P. THOMPSON & Co.,
Agents for the Applicant.

page_text: I, WILLIAM PHILLIPS THOMPSON F.C.S. M.I.M.E. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, and 6 Bank Street, Manchester, both in
the County of Lancaster, and 323 High Holborn, in the County of Middlesex, Civil
Engineer, 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 :-
The present invention consists essentially in employing in the manufacture of
sulphate cellulose, acid sulphate of soda or free sulphuric acid along with neutral
sulphate of soda instead of the neutral sulphate of soda hitherto used.
For the purpose of rendering the present specification clearer, the principle of the
manufacture of sulphate cellulose will first be briefly explained. This manufacture
consists in boiling under pressure in closed vessels, wood in a solution of caustic soda,
sodium sulphide and sulphate of soda.
The liquor obtained in the aforesaid boiling operation, which will hereafter be
called the brown liquor, contains besides unchanged sulphate of soda, the encrusting
matter of the wood combined with soda. This brown liquor is evaporated and
submitted to red heat, that is calcined for the purpose of recuperating the soda.
In this regenerating process the soda is recovered partly as carbonate of soda, and
partly as sodium sulphide owing to the organic compounds of soda, such as resinate
of soda, etcetera, becoming transformed into carbonate of soda, and the sulphate of
soda being reduced into sodium sulphide.
The losses of soda occurring in the process are compensated by an addition of
neutral sulphate of soda, hence the name of sulphate cellulose given to the product
obtained in the process just described.
This neutral sulphate is added to the lye that has to be boiled, and remains
unchanged in the brown liquor after the boiling operation is over. It is then sub-
mitted with the liquor to evaporation and calcination, and thereby transformed into
sodium sulphide.
This sulphide of sodium is the most effective constituent of the boiling lye, it acts
more energetically than caustic soda, and produces a whiter, more easily bleached
cellulose.

page_text: Now it occurs that the success of the process just described is often seriously
influenced by the fact that in spite of the regular working of the process, and the
addition of the suitable quantity of sulphate to the aforesaid lye, the composition of
the latter cannot be kept uniform, and the boiling process turns out frequently to be
a failure, owing chiefly to the rapid decrease of the quantity of sodium sulphide in
the lye.
The process hereafter described, and forming the object of the invention has for its
object to remedy the aforesaid disadvantage, and to produce lyes richer in combina-
tions of sulphur and sodium than it was possible to obtain by the method hitherto
in use.
This new process consists in treating the brown liquor previous to the calcining
operation with acid sulphate of soda, or with free sulphuric acid along with neutral
sulphate of soda.
Through the free sulphuric acid, or the half combined sulphuric acid of the acid
sulphate, the brown liquor undergoes a chemical change, the compounds formed by
the soda with organic acids getting transformed into neutral sulphate of soda and free
organic acids, such as resinic acid etcetera, which separate as they are not soluble in
water.
In the subsequent stage of the process, namely, the calcining operation, the sulphate
of soda formed as just explained, is subjected along with the organic substances to a
glowing heat, and thereby reduced into sodium sulphide.
The product obtained in the above calcining operation, the so-called fusion, contains
a quantity of sodium sulphide equivalent to the quantity of sulphuric acid or acid
sulphate of soda added, whilst previously when neutral sulphate of soda was used, only
as much sodium sulphide was obtained as corresponded to the quantity of neutral
sulphate of sodium added to the brown liquor.
The working of the improved process may be explained as follows:-
Let the soda combinations contained in the brown liquor be represented by the
formula Na, (Cx Hy Oz), and the organic substances as acids by the formula
(Cx Hy Oz), H₂, then the addition to such a brown liquor, of one molecule of sulphate
of soda (Na, SO) for each 5 molecules of Na, (Cx Hy Oz), will give after evapora-
tion of the said liquor, and calcination of the solid portion thereof.
5 Na, (Cx Hy Oz) 2 + Na₂ SO
=====
5 Na, CO, Na, S plus remaining CH and O
as carbonic acid water, etcetera, that is to say 100 Na, CO₂ give 20 per cent. Na, S.
If, instead of one molecule of sulphate of soda, 2 molecules of acid sulphate of soda
(or 1 molecule of sulphuric acid and 1 of sulphate of soda) are added, the following
changes take place.
In the first once.

page_text: that is 50 parts of sulphide of sodium for 100 of carbonate of soda, whereas when
sulphate of soda was used, alone only 20 parts of sulphide, sodium are obtained per
100 parts of carbonate of soda.
It will be understood from the foregoing that the effect of the free sulphuric acid or
of the half combined sulphuric acid of the acid sulphate, on the brown liquor, is to
greatly increase in the calcined products, the quantity of sodium sulphide, and
thereby render more efficient the action of the lyes.
The same decomposition and action as those obtained with sulphuric acid and acid
sulphate of soda may of course be also obtained with other acids formed by sulphur,
such as sulphurous acid or acid sulphites. Sulphurous acid reduces the organic
compounds of soda into sodium sulphite, and free organic acids. Like sulphate
of soda, the sodium sulphite is also reduced in the calcination process into sodium
sulphide.
Instead of adding the acid sulphate as described, to the so-called brown liquor before
the calcining operation, it may also be added to the lye, which has to be boiled. This
would only be a round-about way of obtaining the same result as when the acid
sulphate is added to the brown liquor, as the brown liquor is obtained through boiling
this lye.
However, as the said lye has been partially neutralised by the half
combined sulphuric acid of the acid sulphate, and thereby rendered weaker in its
action, it is therefore advisable to add the acid sulphate to the brown liquor.
The quantity of acid sulphate to be added depends upon the strength of the brown
liquor. This strength can be estimated easily by titration with normal acid (Normal
Säure.)
It is best to add as much of this salt or of its solution as will reduce about one
third of the existing soda into sulphate of soda. An excess of free sulphuric acid
is unsuitable.
As mentioned in the foregoing, the addition of free sulphuric acid, or of acid
sulphate of soda to the brown liquor causes the separation of the organic substances.
It will therefore be necessary in order to obtain a uniform fusion product to stir
energetically the brown liquor, whilst it is submitted to evaporation, so that the
said organic substances may remain united as intimately as possible with the other
portion of the liquor.
Commercial acid sulphate of soda contains variable quantities of half combined, or
free sulphuric acid, ranging between 20 and 40 per cent. Now when this quantity
is too great, a cellulose manufacturer may find himself under the necessity of removing
part of it.
The simplest way of effecting this operation is to neutralise the acid sulphate by
means of the calcareous mud, a worthless bye product obtained in the manufacture of
cellulose, in rendering caustic the raw lyes. The most convenient way of effecting
this neutralisation consists in washing out the calcareous mud with water in the vessels
wherein the raw lyes are cauticised, and then mixing it with water in the same
vessels, and adding gradually to it the required quantity of acid sulphate. The acid
sulphate is hereby transformed into neutral sulphate, whilst carbonic acid is evolved,
and sulphate of lime formed. The latter is allowed to settle down, and the clarified
solution of sulphate of soda standing above the deposit is added either to the brown
liquor, or to the lye to be boiled.
Both manners of proceeding may appropriately be combined in such a manner that
one part of the acid sulphate is added directly to the brown liquor whilst the other
part is first partially or entirely neutralised.
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:-
In the manufacture of soda or sulphate cellulose:
1st. The application of acid sulphate of soda (or of free sulphuric acid along with
neutral sulphate of soda) which application consists in adding it either to the brown

page_text: liquor previous to the calcining operation, said liquor being afterwards evaporated
and fused, or to the lye to be boiled before the boiling operation.
2nd. The application of acid sulphate of soda in the manufacture of soda or sulphate
cellulose as claimed in the foregoing clause, after the said acid has been first partially
or completely neutralised by means of the calcareous mud obtained as bye-product in
the said manufacture.