Improvements in the Boiling Process for Producing Cellulose by means of Sulphurous Acid.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in the Boiling Process for Producing Cellulose by
means of Sulphurous Acid.
I CARL KELLNER of Hallein in the Empire of Austria 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 boiling operation carried out in the treatment of
wood for producing cellulose by means of the solution of a sulphite in liquid
sulphurous acid, and has for its object to avoid the occurring waste of the latter, as
well as the soiling of the product by a precipitation of the monosulphite.
Heretofore it has been the habit to fill into the boilers the wood together with
the cold sulphurous solution, and to heat the latter to the desired temperature by
means of a steam-coil, of a steam jacket, or of steam introduced directly into the
boiler.
In addition to the fact that this heating operation takes a long time, during
which the boiler is diverted from its real function, it has for its effect an escape
of gaseous sulphurous acid which lasts until the generated pressure prevents
a further formation of gases, and, in consequence of this escapement of sulphurous
oxide, a proportionate quantity of monosulphite is separated from the solution and
precipitated on the hottest places of the boiler.
According to my invention, this inconvenience is obviated in such a way that the
solution of the sulphite in the liquid sulphurous acid is heated above the boiling
point in a separate vessel, and is only then introduced, in an already heated state,
into the boiler.
Further, in order that the monosulphite separated from the first charge and
precipitated in the vessel which serves for heating the solution may be caused to
be again dissolved in the next charge, the invention provides that the sulphurous
oxide, mixed with steam, which escapes from the boilers, is conducted into the
heating-vessel.
Although the arrangement of a heating apparatus designed for the above
mentioned purpose will be easily intelligible to any professional man and in its
details depends upon local circumstances, and in order that the principle of ny
invention may be more clearly understood I annex a description of appliances of a
simple nature, which I find suitable for use in the majority of cases, reference being
made to the accompanying sheet of drawings, in which:
Fig. 1 (Sheet 1) represents a vertical, and Fig. 2 (Sheet 2) a horizontal heater,
both in vertical section.
Fig. 3 is a transverse section of the apparatus represented in Fig. 2.
As shown, the heating-vessel a (Fig. 1) contains a heating coil b, in which steam
is introduced through the pipe c, while the condensed water flows off through the
pipe d into the receiver e and is conducted from there to be used as feed water for
the steam boiler.
The lye which is intended to be heated is forced under pressure through the
valve finto the vessel a and, after it has attained the desired temperature it is made
to pass through the valve g into the boiler.
The sulphurous acid which has escaped in consequence of the heating operation,
passes through the pipe h into the serpentine, surrounded by the cooling vessel k.
The refrigerating water fed from the pipe circulates in an opposite direction to
that of the liquid resulting from the condensation, and the latter, together with the
sulphurous acid which has escaped from the boilers, is pumped into the heater when

page_text: the same is charged again in order to re-dissolve the monosulphite previously
precipitated from the former solution.
The man-hole m provided with a suitable cover and the valve n serve for cleaning
the heater a from time to time.
In the apparatus represented in Figs. 2 and 3, the heater a is arranged hori-
zontally and contains a stirring device o, the motion of which maintains the
precipitated monosulphite in the shape of a powder and prevents the solidification
of the same in the shape of a hard crust.
The lye is let in through a perforated tube p arranged beneath the heating-coil b,
and a dome shaped part 9 provided at the top allows the lye to expand itself, and
the escaping sulphurous acid to be carried off through the pipe h into the condenser.
The salient feature of this heater is an isolating sheet-metal casing r in which a
pockets is provided for receiving the thermometer.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
First. In the operation of treating wood by sulphurous acid for producing
cellulose, the heating of the lye previously to its being introduced into the boiler,
in order to avoid the wasting of sulphurous acid and the soiling of the product by
precipitated monosulphite, substantially as described.
Secondly. In the process described in the first claim, the re-dissolution of the
precipitated monosulphite formed during the heating operation, said re-dissolution
being obtained by the introduction into the heater of the sulphurous acid escaping
from the heater and from the boilers, substantially as described.
Dated this 30th day of July 1801
GEO. DAVIES & SON,
4, St. Ann's Square, Manchester, Agents for the Applicant.