AN IMPROVED MANUFACTURE OF PAPER PULP
Year: 1881

page_text: LETTERS PATENT to David Otto Francke, of Korndal Mölndal, in the
Kingdom of Sweden, for an Invention of "AN IMPROVED MANUFACTURE
OF PAPER PULP."
PROVISIONAL SPECIFICATION left by the said David Otto Francke at the
Office of the Commissioners of Patents on the 11th October 1881.
DAVID OTTO FRANCKE, of Korndal Mölndal, in the Kingdom of Sweden. " AN
IMPROVED MANUFACTURE OF PAPER PULP."
My Invention relates to the manufacture of paper pulp from wood, esparto,
wheat, maize, or other straw, or from other suitable vegetable fibre, the object
which I have in view being to produce in a cheap and easy manner pulp of high
quality fit for making paper without addition of rag or other pulp.
I prepare a solution of acid calcium sulphite or mixture of calcium sulphite
with sulphurous acid by passing through a tower charged with limestone kept wet
by a stream of water, the sulphurous acid fumes produced by burning sulphur or
by roasting or calcining sulphides, such as pyrites. When the acid calcium sulphite
thus produced has a strength of about 4° or 5° Beaumé, I charge it along with
fragments of the wood or of the straw or other fibrous material that is to be
treated into a strong vessel or boiler heated by a steam casing or coil or by steam
tubes, the steam employed being at a pressure of 4 to 5 atmospheres.
The proportion of solution employed varies according to the character of the
material treated; about 2000 to 2500 gallons of solution will generally suffice for
the production of 1 ton of wood pulp.
As the pulping action is greatly promoted by agitation I prefer to employ for
the purpose a vessel of cylindrical form caused to revolve while its charge is under
treatment.
The material having been thus subjected to heat and pressure for 12 to 15 hours
is withdrawn from the vessel, and being washed is ready for paper making.
In preparing the solution as above described pure limestone is not essential,
as limestone containing a proportion of magnesia or other alkaline earth or
mineral, such as witherite, can be employed without detriment to the pulping
action.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said David Otto Francke in the Great Seal Patent Office on the
4th April 1882.
DAVID OTTO FRANCKE, of Korndal Mölndal, in the Kingdom of Sweden.
IMPROVED MANUFACTURE OF PAPER PULP."
"AN
My Invention relates to the manufacture of paper pulp from wood, esparto,
wheat, maize, or other straw, or from other suitable vegetable fibre, the object
which I have in view being to produce in a cheap and easy manner pulp of high
quality fit for making paper without addition of rag or other pulp.
I prepare a solution of acid calcium sulphite or mixture of calcium sulphite with
sulphurous acid by passing through a tower charged with limestone kept wet by
a stream of water, the sulphurous acid fumes produced by burning sulphur or by
roasting or calcining sulphides, such as pyrites. When the acid calcium sulphite
thus produced has a strength of about 4° or 5° Beaumé, I charge it along with
fragments of the wood or of the straw or other fibrous material that is to be treated
into a strong vessel or boiler heated by a steam casing or coil or by steam tubes,
the steam employed being at a pressure of 4 to 5 atmospheres.
The proportion of solution employed varies according to the character of the
material treated; about 2000 to 2500 gallons of solution will generally suffice for
the production of 1 ton of wood pulp.
As the pulping action is greatly promoted by agitation I prefer to employ for
the purpose a vessel of cylindrical form caused to revolve while its charge is under
treatment.
The material having been thus subjected to heat and pressure for 12 to 15 hours
is withdrawn from the vessel, and being washed is ready for paper making.
It is to be understood that the wood before treatment as above described has its
bark stripped off and its knots bored out, and is cut into transverse slabs from one
quarter to half an inch thick. Jute may be treated in the same manner as wood,
its fibres being in the first place cut to lengths of about half an inch; and in a
similar manner straw, esparto, and other vegetable fibres of like character may
be treated, the solution employed for these being somewhat weaker than that used
for wood or jute, say, from 3° to 4° Beaumé, and the process occupying somewhat
less time, say, from 8 to 10 hours. In charging the pulping vessel I generally
leave about one quarter of its capacity as space for steam and vapour, the rest
being occupied with the material to be treated and the solvent. As many of the
fibres operated on, such as straw or esparto, are lighter than wood, the quantity of
solvent to the ton of pulp produced exceeds that which I have stated as being
suitable for wood; but as I employ it of less strength its active part bears
approximately the same proportion to the material treated.
In preparing the solution as above described pure limestone is not essential,
as limestone containing a proportion of magnesia or other alkaline earth or
mineral, such as witherite, can be employed without detriment to the pulping
action.
The accompanying Drawings represent apparatus which may conveniently be
employed in manufacturing pulp as I have described. Fig. 1 is a vertical section
of the tower A, which is lined with lead and charged through doors e with
fragments of limestone that rest on a grating b at the bottom. A cistern C at the
top supplies water, which may be spread over the limestone by a tumbling vessel d.
The sulphurous acid fumes enter the tower by a flue fand the solution collects in
a receptacle a at the bottom, whence it is drawn away for use by a pipe g. Fig. 2
is a transverse section and Fig. 3 a longitudinal section shewing one form of

page_text: pulping vessel which I employ. It is a cylindrical vessel like a boiler B, having
at each end an annular steam space C, C', connected by tubes D, the interior of
the vessel and the exterior of these tubes being lined with lead. The vessel has
two rings a, a, which run on rollers a¹, and to one of these rings is attached worm
teeth c gearing with a worm d that is driven by any convenient motor at such
speed that the vessel B makes one revolution in about 10 minutes. o is a safety
valve and pa pressure gauge; 9, 9, are man-holes for charging and discharging
and m is a valve for withdrawing samples from time to time. The steam is
supplied by the pipe h which enters a trunnion through packing at i; branches k, k,
lead the steam into the jacket C. At the opposite end the water of condensation
is led away by branch pipes 1, 1, and a pipe m. Fig. 4 is a transverse section
and Fig. 5 a sectional plan, shewing another construction of the pulping vessel.
In this case the steam is supplied by a pipe k, extending along the exterior of the
vessel to a number of annular tubes Q fixed within the vessel, and the water of
condensation is removed from these tubes by a pipe . The form and arrangement
of the pulping vessel may obviously be varied; those which I have shewn in the
Drawings are of a kind which I find convenient in practice.
Having thus described the nature of my Invention, and in what manner the
same is to be performed, I claim,—
The manufacture of paper pulp by treating fragments of wood, esparto, straw,
or other suitable vegetable fibre with acid calcium sulphite, prepared and applied
substantially as herein described.
In witness whereof, I, the said David Otto Francke, have hereunto set my
hand and seal, this Thirty-first day of March, in the year of our Lord
One thousand eight hundred and eighty two.
444
DAVID OTTO FRANCKE. (L.S.)