Improvements in or relating to the Prevention of the Corrosion of Vessels, Tubes, Valves, and the like used in the Manufacture of Sulphite Cellulose.
Year: 1889

page_text: Date of Application, 2nd Apr., 1889-Accepted, 29th Mar., 1890
COMPLETE SPECIFICATION.
Improvements in or relating to the Prevention of the Corrosion of
Vessels, Tubes, Valves, and the like used in the Manufacture of
Sulphite Cellulose.
A communication from CARL HEINRICH JUNG and JOHANNES PAUL LINDIG, of
Freiberg, in the Empire of Germany, Manufacturers.
I, ALFRED JULIUS BOULT of 323 High Holborn, in the County of Middlesex,
M.I.M.E., do hereby declare the nature of this invention and in what manner the.
same to be performed, to be particularly described, and ascertained in and by the
following statement :-
The present invention relates to a method for the prevention of the corrosion of
vessels, tubes, valves and the like used in the manufacture of sulphite cellulose."
This method consists essentially in the employment of a layer or coating of calcium
iron silicate or calcium silicate at those points and parts of the apparatus which come
in contact with the sulphite lye, with or without the simultaneous application of a
cement consisting of calcium monesulphite and water-glass...
According to the nature of the apparatus.the method is employed as follows:-.
a). Boiling apparatus; for the purpose of cleaning, the apparatus is first scoured
with a lye (ie. soda or potash lye or solution) and is then treated with a diluted
mineral acid such as sulphuric- nitric- or hydrochloric acid. After this operation:
the surface is coated with a solution of sulphite of calcium in dilute sulphurous acid
for the formation of calcium iron sulphite. When this is dry the surface is coated
with a solution of potash- or soda-water-glass for the formation of calcium iron
silicate; it is preferable to repeat this coating after the first is dry. On to this silicate.
coating is applied a layer of a thickness of 1 to 5 centimetres of a pulpy mixture of
calcium monosulphite and potash- or soda-water-glass to which may be added an
indifferent substance such as chamotte-powder fine sand, pulverized glass asbestos or
the like.
When this layer is dry and hard, water is boiled in the vessel with an admixture of
bisulphite of calcium thus forming sulphite of soda in solution and in the above
mentioned layer forming silicate of calcium which protects the surface against the
effects of the sulphite lye. After several boilings it is preferable to repeat the
layer of calcium monosulphite and water-glass for the purpose of forming several
layers of silicate.
6). Tubes and valves. Tubes and valves are cleaned and treated with acid in the
same manner as the boiling apparatus and are then filled with a solution of
bisulphite of calcium and warmed they are then emptied and filled with the
solution of water-glass and then emptied and dried. The outside is then coated
several times thickly with red lead and linseed oil and they are then boiled in an
autoclave in a solution of bisulphite of calcium, again filled with solution of water-
glass, emptied and dried. This operation is repeated until a sufficiently thick layer of
silicate of calcium is formed.
c). Reservoirs and channels for the liquid are coated with the mixture of mono-
sulphite of calcium and silicate of soda or potash. The bricks for these reservoirs or
channels are impregnated with a hot solution of water-glass, or the brick-work is
several times coated therewith.
As the mixture of monosulphite of calcium and water-glass dries quickly and
becomes closer and harder in contact with a solution of bisulphite of calcium,
because the pores are filled more and more with silicate of calcium, as further this
layer adheres to the iron like rust-cement because of the above described preliminary
treatment of the iron, and as lastly the coefficients of the linear expansion of the iron
and of this mixture only vary in the fifth decimal and therefore can be considered as
I

page_text: equal, this method offers better protection against corrosion than all others known up
to the present time and can be employed most cheaply and simply with all kinds of
boiling and other apparatus used in the manufacture of sulphite cellulose.
To prevent the walls of the boiler being affected by the sulphite lye in case cracks
appear in time in the layer of silicate of calcium, the boiler is included in the
electric circuit of a dynamo machine or an accumulator and the iron boiler forms the
cathode while a lead plate inserted through the walls of the boiler or the lid and
insulated therefrom forms the anode. The strength of the current is regulated by
means of suitable resistances in such a manner that in case cracks should appear in
the protecting layer of the boiler the exposed iron surface is covered with the
deposit consequent on the decomposition of the lye by electrolysis, i.e. the cracks
will be filled up with the deposit and these places which can be noticed when the
boiler is emptied by their lighter colour are then coated with a solution. of water-
glass.
"Having now particularly described and ascertained the naturo of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondents, I declare that what I claim is
;
For the purpose of protecting apparatus employed in the manufacture of sulphite
cellulose against corrosion :-
1. That the places coming in contact with the sulphite lye, after being thoroughly
cleaned or scoured, are treated with a diluted mineral acid, and then coated first
with a solution of sulphite of calcium in aqueous sulphurous acid, then with a
mixture of water glass and monosulphite of calcium used either alone or in
conjunction with other substances that cannot be affected by contact with the other
chemicals.
2. The filling up of cracks appearing in the protecting layer of a sulphite boiler
during the boiling by means of an electrolytic deposit from the boiling lye.
3. The employment of a mixture of monosulphite of calcium and water-glass for
the coating of reservoirs, channels and the like which come in contact with the lye
used in the sulphite cellulose manufacture.
Dated this 2nd day of April 1889.
W. P. THOMPSON & BOULT,
Agents for the Applicant.