Improvements in Paper Pulp Digesters.
Year: 1892

page_text: Date of Application, 8th Nov., 1892-Accepted, 4th Mar., 1893
COMPLETE SPECIFICATION.
[Communicated from abroad by CHARLES CURTIS, of Newton, in the County of
Middlesex and State of Massachusetts, NATHANIEL MORRISON JONES, of
Bangor, in the County of Penobscot and State of Maine, and THOMAS
BAILEY DRAPER, of Canton, Norfolk, County Massachusetts, in the United.
States of America, Gentlemen.]
Improvements in Paper Pulp Digesters.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings in the County of Middlesex, 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 digesters for cooking wood chips in the manufacture of
paper pulp, and has for its object, first, to provide such a construction as will
protect the metal shell of the digester against the acid solutions employed to
dissolve the resins and gums of the wood. The invention also has for its object to
provide certain improvements relating to the supply and outlet orifices of the
digester; and, finally, to provide improved means for the protection of the inner
surface of the cement lining when such protection is desirable.
To these ends, the invention consists, first, in a digester comprising an external
shell or casing of metal, and a lining composed of compressed and preferably
carbonized cement or artificial stone. The invention also consists in certain
improvements relating to the construction of the supply and discharge orifices of
the digester; and, further, in certain improvements relating to the protection of
the cement lining by metallic acid-resisting material.
Of the accompanying drawings, forming part of this Specification:
Figure 1 represents a vertical section of a digester embodying our invention,
the central portion being broken away.
Figure 2 represents a perspective view of one of the blocks.
Figures 3 and 4 represent horizontal sections, showing cement-lined blocks
provided with facings or linings of metallic acid-resisting material.
The same letters of reference indicate the same parts in all the figures.
In the drawings :
a represents the shell of the digester, which is preferably of cylindrical form,
and composed of any suitable metal, such as iron, steel, phosphor bronze, brass, etc.
b represents an intermediate lining, which is preferably composed of asbestos
and cement made into a plastic composition and applied to the inner surface of
the shell in a plastic state, its object being to protect the inner cement lining
hereinafter described and to prevent contact of the acid solution with the metal
shell in the event of leakage through the cement lining.
c represents the cement lining, which is composed preferably of Portland cement
and ground glass or quartz, with or without a percentage of soluble glass. We do
not limit ourselves to this composition, however, and may use any other cement or
composition. The cement is carbonized by the absorption of carbonic acid gas,
and is thus converted into an artificial stone and rendered extremely hard and
durable, so that it is particularly adapted for use as a digester lining, it being
impervious to the acid, and comparatively free from liability to crack and chip.
We show the cement lining as constructed in sections 88, which are provided at
their edges with tongues 9 and recesses 10, the tongues of each section entering
the recesses of the adjacent section, so that the sections overlap at their joints. The
sections or blocks are formed in suitable flasks or molds, the ingredients of the
cement being inserted in the molds and subjected to sufficient pressure therein
:before. the setting of the cement to make the blocks uniformly dense and free from

page_text: pores or air holes. The compression of the cement is an important part of our
invention and prevents liability of the acid solution working its way through the
blocks, which liability would exist to a greater or less extent if the blocks were
simply formed without compression.
It will be seen that the lining of carbonized cement, being extremely hard
and dense, is well adapted not only to resist the acid solution, but also the heat
which is used in cooking the wood chips, preventing both the acid and the heat
from reaching the shell of the digester; while the intermediate lining constitutes
a safe-guard or protection for the metal shell against the action of the acid solution
in the event of cracking of the cement.
We do not claim broadly the process of carbonizing cement by subjecting the
same to carbonic acid gas; but we are the first, so far as we are aware, to provide
a metal shell with a lining of carbonized cement.
We do not limit ourselves in all cases to the use of the intermediate lining b, and
may place the cement lining directly against the inner surface of the metal shell,
or may interpose between the inner cement lining and shell only a coating of
cement.
We are aware that digester shells have been lined with glazed or vitrified tiles,
and with porcelain tiles, but we make the following broad distinctions between a
carbonized cement lining and a lining of glazed or vitrified tiles or porcelain
tiles, viz. First, carbonized cement is homogeneous and has substantially the
same coefficient of expansion and contraction as iron and steel, so that, when the
digester is opened and cooled internally after the discharge of its contents, the lining
and shell contract alike and there is no liability of the shell contracting more
rapidly than the lining and thus exerting an injurious compressive strain on the
lining. On the other hand, a lining of glazed or vitrified tile or of porcelain tile
will contract more slowly than the metal shell, so that there would be a pressure
on the lining tending to crack and chip off its inner surface. Secondly, carbonized
cement is more elastic than glazed or vitrified tile and porcelain tile, so that it is
not so easily broken.
We are also aware that it is not new to provide a boiler or a digester shell with
a continuous lining of cement applied in a plastic state to the interior of the shell:
Such lining has never been carbonized, however, prior to our invention, and there-
fore differs from our lining in that it is much more brittle and liable to crack and
chip off.
An objection to a continuous cement lining, applied in a plastic state, is
that it is impossible to make the lining of uniform density, hence it is often
defectively porous in spots and thus liable to be permeated by the acid. Our
lining is made of previously molded blocks, the material of which is subjected to
pressure during the molding operation, so that there is no difficulty in making all
the blocks of uniform density and strength, the inherent strength of the cement
being increased by carbonization.
The advantages due to the compression of the cement are not wholly dependent
on the carbonization of the cement, although the latter is a very important feature.
We therefore desire to cover a lining of compressed cement, whether carbonized
or not.
1
In Figure 1, we show certain improvements relating to the supply and discharge
openings at the top and bottom of the digester, and these improvements we will
next describe.
To the upper end of the digester shell a, we rivet or otherwise securely attach a
cylindrical collar, the upper end of which is provided with a flange f'. g represents
a cylinder of smaller diameter than the collar, said cylinder being placed within
the collar and separated therefrom by an annular space, which receives a part of
the cement lining b, and is open at its lower end, so that said part of the cement
lining communicates with the main body thereof. The cylinder g is provided at
its upper end with an outwardly projecting flange b', which bears upon the flange f
The flange is provided with a suitable number of orifices at 92 to enable the
cement to be poured into the space between the collar and cylinder g, said orifices.

page_text: being closed when not in use by means of suitable plugs. We prefer to corrugate
the external surface of the cylinder g, as shown in Figure 1, to enable it to engage
or interlock the cement filling when the latter becomes hard. The lower end of the
cylinder y projects somewhat into the interior of the digester, and is externally
screw-threaded to engage an internally screw-threaded collar i, having an
outwardly-projecting flange i. Said flange bears upon the inner surfaces of the
end tier or course of lining blocks 8, and serves to support said tier or course, as
well as to co-operate with the lining in securing the cylinder in place. The
cylinder y and collar i are preferably made of phosphor bronze, aluminium or some
other metallic substance which is not liable to be injuriously affected by the acid
solution employed in disintegrating the pulp.
The lower end of the digester is provided with a similar collar and cylinder g
said collar and cylinder being attached in the manner above described, and
differing from the collar and cylinder at the upper end of the digester only in size.
represents a blow-off connection, which is bolted to the flanges of the lower
collar and cylinder g.
In Figures 3 and 4, we show the lining blocks 8 provided on their inner faces
with protecting plates k of metallic acid-resisting material, preferably of lead each
plate being independently attached to the corresponding block. The object of
thus protecting the exposed faces of the cement blocks, which are in themselves
practically acid proof, is to provide against the possibility of cracking of the
sections or blocks; and also to provide against the possibility of the corrosion of
the sections or blocks, because cement is sometimes liable to become corroded,
owing to the presence of free lime or carbonates. In carying out this part of our
invention, we attach the metallic lining plates k to the cement blocks 8 in any
suitable manner. In Figure 3, we show the lining plate k provided on its rear
surface with ears or lugs k', which are engaged with T-shaped or flanged keys k²
embedded in the material of the block 8. In Figure 4, we show the lining plate k
provided on its back with dove-tail projections ³, which are embedded in the
material of the block 8. The lining plate k is secured to the cement block.during
the process of manufacturing the latter, the lining k being preferably inserted in the
mold or flask in which the block is formed, while the block is built up around the
keys k or projections or whatever other device is employed to engage the lining
with the cement block. We prefer to extend the lining beyond the block, as shown
at A, the extended portion of one block being adapted to overlap the adjacent edge
of the lining on the adjoining block, so that the linings may be secured together by
fusing the overlapping portions. We do not limit ourselves, however, to this
method and construction, and may adopt any suitable means for forming tight joints
between the linings of the different blocks.
We consider it important that each block have an independent metallic lining k
and that said lining be secured to the block at several points, so that there will be no
liability of any undesirable separation of the lining from the block by the expansion
of the lining.
Having now particularly described and ascertained the nature of the said inven-
tion, 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:
1st. The improved pulp digester herein described, comprising in its construction
a metal shell and a lining composed of compressed carbonized cement, as set
forth.
2nd. The improved pulp digester herein described, comprising in its construction
a metal shell and a lining composed of compressed cement, as set forth.
3rd. In a digester, the combination of an outer shell, a flanged collar secured
thereto, an inwardly-extended cylinder in said collar concentric with and of a
smaller diameter than said collar, an inner lining composed of molded blocks, and
a flange screwed upon the inner end of said cylinder and bearing on the inner
surface of the inner lining, substantially as described.

page_text: 4th. In a digester, the combination of an outer shell, an outwardly extended
collar thereon. having a flange, an inwardly-extended cylinder in said collar con-
centric with and of a smaller diameter than said collar, a cement lining between the
shell and cylinder, said cylinder being provided with corrugations to engage the
said cement lining, an inner lining composed of molded blocks, and a flange screwed.
upon the inner end of said cylinder and bearing on the inner surface of the inner
lining, substantially as described.
•
5th. In a digester, an outer shell a, an inwardly-extended collar f having a
flange, an inwardly-extended externally-corrugated cylinder g having a flange g¹
provided with openings for the insertion of the cement lining between said cylinder
and collar, an inner lining composed of molded blocks, a flange secured to the
inner end of the cylinder and bearing on the said inner lining, and an outer cement
lining interposed betwen the shell and cylinder and engaged with the corrugations
of the cylinder.
6th. A digester, comprising in its construction an external metal shell, a lining
composed of molded blocks or sections, and an inner lining composed of inde-
pendent plates or sheets of metallic acid-resisting material, each of said plates or
sheets being engaged independently with one of the said blocks or sections, as set
forth.
7th. A digester, composed of a shell, a cement lining, and a series of independent
metallic acid-resisting lining plates each connected to the cement at a number of
points between its edge, as set forth.
8th. The combination with a digester shell and a cement lining therefor, of a
series of metallic acid-resisting lining plates, each having a plurality of fastening
devices secured to it and to the cement lining at points within the edges of the
plates, as set forth.
9th. A digester lining block, composed of cement, having a metallic acid-resisting
lining plate attached to its inner surface by a plurality of fastening devices
projecting from the back of said plate at points between the edges thereof.
10th. The combination of a metallic acid-resisting lining plate, a series of
fastening devices projecting from the back of the plate, and a cement support
formed upon said fastening devices, as set forth.
Dated this 8th day of November 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.