Improvements in the Treatment of Fibrous Plants for the Manufacture of Paper Pulp.
Year: 1891

page_text: Date of Application, 17th Feb., 1891
Complete Specification Left, 16th Oct., 1891-Accepted, 21st Nov., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Fibrous Plants for the
Manufacture of Paper Pulp.
I, JAMES BEVERIDGE of 4 Kent Road Gravesend in the County of Kent,
Technical Chemist, do hereby declare the nature of this invention to be as
follows: :-
This invention relates to the treatment of straw, esparto grass (alfa) and other
fibrous plants containing comparatively speaking large quantities of mineral
substances, particularly silicates.
I have observed when straw, esparto grass and other similar raw fibrous plants
which contain considerable quantities of silica or compounds thereof are digested
or boiled at temperatures about 212° Fahrenheit in aqueous solutions of bisulphites
of 'lime, magnesia or soda, or in solutions of sulphite of lime, magnesia or soda in
aqueous sulphurous acid that the silicates in such fibrous plants are not wholly
attacked or dissolved by the said 'bisulphite liquors, that is to say the silica and the
bases with which it is combined are not sufficiently dissolved, and therefore the
percentage-quantity of mineral substances in the pulp produced by this mode of
treating such fibrous plants is abnormally high, or is considerably greater than that
which exists in the original plant operated upon. Such pulp is for various reasons
unsuitable for the manufacture of high-class papers.
The object of this invention is to procure from straw, esparto grass and other
raw fibrous plants containing silicates a pulp which will be substantially free from
these mineral substances, and which will be in other respects suitable for the
manufacture of paper.
My invention consists in subjecting the fibrous plants to a double treatment
which consists in first digesting or boiling them at temperatures above
212° Fahrenheit in an aqueous solution of bisulphite of lime, magnesia or soda, or
in a solution of sulphite of lime, magnesia or soda in aqueous sulphurous acid, and
then, after washing with water, submitting the crude pulp thus obtained to the
action of a caustic Iye; or the order of the two chemical operations or treatments
can be reversed, that is to say the fibrous plants can be submitted first to the
caustic lye treatment, and then, after washing, to the bisulphite treatment.
The manner in which my invention can be carried into effect is as follows:-
The straw, esparto, or other raw fibrous plant which is to be treated or manu-
'factured into paper pulp is sorted, dusted and cut or otherwise suitably cleaned
and prepared, and then digested or boiled in an aqueous solution of a suitable
bisulphite, such as bisulphite of lime, magnesia or soda, but preferably the latter,
in suitable iron boilers lined with lead or other acid resisting material in any
of the well known ways. I prefer, however, to employ for this purpose a
revolving spherical boiler constructed of steel plates and supported on trunnions,
the entire interior surface of the said boiler being covered with sheet lead.
The boiler and contents are heated by direct steam injected into the said contents
through the trunnion or trunnions for from three to seven hours or longer at a
pressure of about 50 or 60 pounds per square inch above atmosphere corresponding
to a temperature of about 300° Fahrenheit. The temperature or pressure and the
length of time the "charge" is heated vary with the nature of the fibrous plant
which is 'being treated. After the digesting process is completed the pressure
within the boiler is blown off, the manhole cover removed and the contents of the
boiler emptied into any convenient receptacle, but preferably into a vat or vats
placed beneath the boiler and constructed of stone or cement, concrete work, or of
cast iron, which may be lined with lead. Each of these vats or tanks is fitted with

page_text: a perforated false bottom and suitable ways or pipes and cocks, so that the liquid
contents may be allowed to drain from the pulp whenever required. The raw pulp
from the boilers or digesters is now washed in these vats with a plentiful supply of
water, preferably hot, until, the washings are substantially free from sulphites or
compounds thereof.
The pulp at this stage contains a large quantity of mineral matter, chiefly
silicates, which has a tendency to hold or bind the fibres together in bundles, and
in order to remove these mineral substances and thus further liberate or separate
the individual fibres from one another I now steep, digest or soak the said pulp in
an aqueous solution of a suitable caustic alkali such as caustic soda, of suitable]
strength, for two or three hours or longer at a temperature ranging from
120° Fahrenheit to 212° Fahrenheit. The mixture of caustic lye and pulp is kept
hot by means of an open steam pipe or by a steam coil immersed in the contents of
the vat or vats, and the liquor may be caused to circulate through the mass of pulp
by a system of pipes and steam injector or pump, either of which conveys the lye
from beneath the false bottom and distributes it over the top of the pulp. By this
treatment the greater part of the silica or compounds thereof is dissolved by the
alkali forming soluble silicates of the alkali used. This steeping, soaking or
digesting process or treatment is continued till the pulp is sufficiently free from
silica and other mineral substances soluble in caustic alkalies. In order to be
economical in the use of the caustic soda or other suitable alkaline lye I
repeatedly use it for digesting, steeping or soaking fresh quantities of pulp till
its power of acting on the silica is in a practical sense exhausted. After this
may be thrown away. Or the active power of the caustic lye may be maintained
practically constant by adding a fresh quantity of caustic soda to each vat of fresh
pulp from the bisulphite boilers, together with such a quantity of lye already used
in a neighbouring vat as will make up the required volume to completely cover the
pulp. The amount of caustic alkali required to treat one ton of air dried pulp by
this method so as to yield satisfactory results varies with the amount of silicates
which the straw, esparto or other fibrous plant contains; but when working with
oat, wheat or rye straw from one to two hundredweight of 60 per cent. caustic soda
are sufficient per ton of pulp produced. The pulp after this treatment with caustic
lye is now washed with water till free from alkali or nearly so, and is then removed
in any convenient way to a breaker engine or potcher where it is thoroughly
disintegrated, again washed and finally bleached with hypochlorites. The pulp
thus produced is of superior quality, requires less bleaching powder per unit weight
to bleach it to a good white color, than pulps prepared by the usual soda methods
or processes and is in all respects very suitable for the manufacture of high-class
papers.
it
Although in ordinary practice I prefer to subject the raw fibrous plant first to
the bisulphite treatment and secondly to the alkaline treatment as above set forth,
yet the order in which the fibrous material undergoes these two chemical operations
or treatments may be reversed, that is to say the straw, esparto or other fibrous plants
may be first digested, steeped or soaked in the caustic lye at temperatures below
212° Fahrenheit till the bulk of the silica or compounds thereof is dissolved and
after washing with water to get rid of the bulk of the alkali, be then removed to
the bisulphite boiler and there finally digested or boiled in an aqueous solution of
bisulphites, substantially as above described or by other known methods.
בד

page_text: COMPLETE SPECIFICATION.
Improvements in the Treatment of Fibrous Plants for the
Manufacture of Paper Pulp.
I, JAMES BEVERIDGE of 4 Kent Road, Gravesend in the County of Kent
Technical Chemist, 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 relates to the treatment of straw, esparto grass (alfa) and other
fibrous plants containing comparatively speaking large quantities of mineral
substances, particularly silicates.
I have observed when straw, esparto grass and other similar raw fibrous plants
which contain considerable quantities of silica or compounds thereof are digested
or boiled at temperatures about 212° Fahrenheit in an aqueous solution of bisulphite
of lime, magnesia or soda, or in a solution of sulphite of lime, magnesia or soda
in aqueous sulphurous acid, that the silicates in such fibrous plants are not wholly
attacked or dissolved by the said bisulphite liquor, that is to say the silica and the
bases with which it is combined are not sufficiently dissolved and therefore the
percentage quantity of mineral substances in the pulp produced by this mode of
treating such fibrous plants is abnormally high, or is considerably greater than that
which exists in the original plant operated upon. Such pulp is for various reasons
unsuitable for the manufacture of high class papers.
The object of this invention is to procure from straw, esparto grass and other
raw fibrous plants containing ilicates, a pulp which will be substantially free from
these mineral substances and which will be, in other respects suitable for the
manufacture of paper.
My invention consists in subjecting the fibrous plants to a double treatment
which consists in first digesting or boiling them at a temperature above
212° Fahrenheit in an aqueous solution of bisulphite of lime, magnesia or soda
or in a solution of sulphite of lime, magnesia or soda in aqueous sulphurous
acid, and then, after washing with water, submitting the crude pulp thus obtained
to the action of a caustic lye; or the order of the two chemical operations
or treatments can be reversed, that is to say the fibrous plants can be submitted
first to the caustic- lye treatment and then, after washing to the bisulphite
treatment.
The manner in which my invention can be carried into effect is as follows:-The
straw, esparto or other raw fibrous plant which is to be treated or manufactured
into paper pulp is sorted, dusted and cut or otherwise suitably cleaned and prepared,
and then digested or boiled in an aqueous solution of a suitable bisulphite such as
bisulphite of lime, magnesia or soda, but preferably the last, in suitable iron boilers
lined with lead or other acid resisting material, in any of the well known ways.
I prefer however to employ for this purpose a revolving spherical boiler constructed
of steel plates and supported on trunnions the entire interior surface of the said
boiler being covered with sheet lead. The boiler and contents are heated by direct
steam injected into the said contents through the trunnion or trunnions for from
three to seven hours or longer at a pressure of about 50 or 60 lbs. per square inch
above atmosphere corresponding to a temperature of about 300° Fahrenheit.
The temperature or pressure and the length of time the "charge" is heated
vary with the nature of the fibrous plant which is being treated. After the
digesting process is completed the pressure within the boiler is blown off, the
manhole cover removed and the contents of the boiler emptied into any con-
venient receptacle, but preferably into a vat or vats placed beneath the boiler
and constructed of stone or cement, concrete work or of cast iron-which may
be lined with lead. Each of these vats or tanks is fitted with a perforated
false bottom and suitable ways or pipes and cocks, so that the liquid contents

page_text: may be allowed to drain from the pulp whenever required. The raw pulp from
the boilers or digesters is now washed in these vats with a plentiful supply of
water, preferably hot, until the washings are substantially free from sulphites
or compounds thereof.
The pulp at this stage contains a large quantity of mineral matter, chiefly silica
or compounds thereof which have a tendency to hold or bind the fibres together
in bundles, and in order to remove these mineral substances and thus further liberate
or separate the individual fibres from one another I now steep, digest or soak the said
pulp in an aqueous solution of a suitable caustic alkali such as caustic soda of
suitable strength, for two or three hours or longer at a temperature ranging from
120° Fahrenheit to 212° Fahrenheit. The mixture of caustic lye and pulp is kept
hot by means of an open steam pipe or by a steam coil immersed in the contents of
the vat or yats and the liquor may be caused to circulate through the mass of pulp
by a system of pipes and steam injector or pump either of which conveys the lye
from beneath the false bottom and distributes it over the top of the pulp. By this
treatment the greater part of the silica or compounds thereof is dissolved by the
alkali forming soluble silicates of the alkali used. This steeping, soaking or
digesting process or treatment is continued till the pulp is sufficiently free from
silica and other mineral substances soluble in the caustic alkali.
In order to be economical in the use of the caustic soda or other suitable
alkaline lye 1 repeatedly use it for digesting, steeping, or soaking fresh quantities
of pulp till its power of acting on the silica is, in a practical sense, exhausted.
After this it may be thrown away. Or the active power of the caustic lye may be
maintained practically constant by adding a fresh quantity of caustic soda to each
vat of fresh pulp from the bisulphite boilers, together with such a quantity of lyc
already used in a neighbouring vat as will make up the required volume to com-
pletely cover the pulp. The amount of caustic alkali required to treat one ton of
air dried pulp by this method so as to yield satisfactory results varies with the
amount of silicates which the straw, esparto or other fibrous plant contains, but
when working with oat, wheat or rye straw from 1 to 2 cwt. of 60 per cent. caustic
soda are sufficient per ton of pulp produced. The pulp after this treatment with
caustic lye is now washed with water till free from alkali or nearly so, and is then
removed in any convenient way to a breaker engine or potcher where it is
thoroughly disintegrated, again washed, and finally bleached with hypochlorites.
The pulp thus produced is of superior quality, requires less bleaching powder
per unit weight to bleach it to a good white color than pulps prepared by the usual
soda methods or processes and is in all respects very suitable for the manufacture
of high class papers.
Although, in ordinary practice, I prefer to subject the raw fibrous plant first to
the bisulphite treatment and secondly to the alkaline treatment as above set forth
yet the order in which the fibrous material undergoes these two chemical operations
or treatments may be reversed, that is to say the straw, esparto or other fibrous
plants may be first digested, steeped or soaked in the caustic lye at temperatures
below 212° Fahrenheit till the bulk of the silica or compounds thereof is dissolved,
and after washing with water to get rid of the bulk of the alkali, be then removed
to the bisulphite boiler and there finally digested or boiled in an aqueous solution
of bisulphite substantially as above described or by other known methods.
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 method or process of treating straw, esparto grass and
other fibrous plants containing silica or compounds thereof in order to manufacture
paper pulp, by subjecting the said fibrous plants to a double treatment which
consists in first digesting or boiling them at a high temperature in an aqueous,
solution of bisulphite of lime, soda or magnesia or in a solution of sulphite of lime,"
soda or inagnesia in aqueous sulphurous acid, and then after washing with water

page_text: submitting the crude pulp thus obtained to the action of a hot solution of caustic
alkali, all substantially as set forth.
2. The herein described method or process of treating straw, esparto grass and
other fibrous plants containing silica or compounds thereof in order to manufacture
paper pulp by subjecting the said fibrous plants to a double treatment, which
consists in first submitting them to the action of a hot solution of caustic alkali,
and then after washing with water, digesting or boiling them at a high temperature
in an aqueous solution of bisulphite of lime, soda or magnesia, or in a solution of
sulphite of lime, soda or magnésia in aqueous sulphurous acid, all substantially as
set forth.
Dated this 15th day of October 1891
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Chartered Patent Agent.