IMPROVEMENTS IN THE PROCESS OF CONVERTING WOOD AND OTHER FIBROUS MATERIALS INTO Pulp, and in AppaRATUS THEREFOR
Year: 1872

page_text: LETTERS PATENT to Edward Alfred Cowper, of No. C, Great George
Street, Westminster, in the County of Middlesex, for the Invention
of "IMPROVEMENTS IN THE PROCESS OF CONVERTING WOOD AND OTHER FIBROUS
MATERIALS INTO Pulp, and in AppaRATUS THEREFOR.”
Sealed the 1st October 1872, and dated the 27th April 1872.
PROVISIONAL SPECIFICATION left by the said Edward Alfred Cowper
at the Office of the Commissioners of Patents, with his Petition,
on the 27th April 1872.
I, EDWARD ALFRED COWPER, of No. 6, Great George Street, West-
5minster, in the County of Middlesex, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN THE PROCESS OF CONVERTING WOOD
AND OTHER FIBROUS MATERIALS INTO PULP, AND IN APPARATUS THEREFOB," to be as
follows:-

page_text: some cases the application of hot flame direct to the boiler has produced
injury to the boiler or its contents, and in other cases when circulation
pipes have been used there has been great delay in working, or when the
heating has been much urged ruptures in the pipes have occurred.
Loose trays have also been put into pulp boilers with the view of pre- 5
venting the contact of the material with the sides of the boiler, and
perforated linings have also been fixed inside such boilers.
Great loss of alkali has generally occurred from the material not
having been soaked with it before it has been placed in the boiler and
from the want of means of regulating the amount or time of the 10
circulation of the solution in the boiler when it is sufficiently boiled.
Loss of heat has taken place after boiling a charge at a high pressure,
the contents having been allowed to pass out without giving up their heat
properly so that it might be utilized, and there has been inconvenienco
from the steam blowing the soapy lye about, or from "priming"; and 15
again great loss of time and heat has occurred from the materials not
being charged into the boiler as hot as possible, and from the boiler
being allowed to cool between each charge.
Now by my Invention I am enabled to boil the wood or other material
in an efficient manner much more quickly than hitherto, and with a con- 20
siderable saving of alkali, and at the same time to avoid the production
of blacks or burnt pieces of wood or resin soap in the pulp.
"
"
In heating the boiler I employ special means to prevent direct action
of the hot flame on the boiler, for this purpose I place the fire at some
distance from the boiler, and I cool down and extinguish the hot flame 2
by placing between the fire and the boiler a gridiron " or series of
gridirons" of strong small pipes forming a hot water apparatus, so
that only a mild heat reaches the boiler, such as it can well sustain
without injury. The heat absorbed by such hot water apparatus is then
conveyed by circulation to heat a tank containing water or the liquor 3
that will next be charged into the boiler, or to heat the boiler itself or
another boiler.
In some cases I heat the contents of the boiler by means of a series of
steam pipes in it supplied with steam at a very high pressure from a strong
boiler of tubular or other construction. The waste heat from the furnace 3
of the steam boiler may be used to assist in heating the pulp boiler.

page_text: In order to fill and empty the boiler quickly I charge metal boxes
with the material to be boiled; these boxes are made with hooks or
loops by which they can readily be lifted in and out by a crane or tackle;
they are also provided with trunions by which they can be mounted on
trucks to be run from place to place. The boxes have one or more
vertical tubes through them to permit of the circulation of the liquor
in the boiler through them, and each box is provided with a rotating
ventilator valve which can be turned by means of a key passed through
a stuffing box in the top of the boiler so as to be opened or closed at
pleasure whilst the pressure is up, whereby the hot liquor is permitted
to pass through the pulp more freely at one time than at another. Beforc
the boxes are put into the boilers they are filled with wood which has
been previously chopped up or with such other materials as are to be
operated on, and they are then put to soak in hot strong lyc, which has
the effect of soaking the material with the alkali, so that the resin and
other impurities may be more readily acted on and the chemical changes
effected which allow of the seperation of the fibres into pulp. The
boxes containing the soaked materials are then put into the boiler,
which is nearly filled up with caustic alkali or water or spent lyc, and
the valves of the boxes are kept closed until the whole has been raised
to the required temperature so that the caustic alkali may act on the
material at the high temperature without dilution. The valves of the
boxes are afterwards opened so as to allow the liquor in the boiler to
circulate through the material in the boxes.
For conveniently discharging the liquor from the boiler and utilizing
the heat I employ a coil of pipo or a "refrigerator" through which the
liquor is made to pass as it leave the boiler, giving its heat to cold
water or cold liquor. The discharge pipe is provided at the end farthest
from the boiler with a cock or valve which is opened to allow the liquor
to pass into an open tank. Thus the temperature of the liquor is
reduced before its discharge so far as to avoid the inconvenience arising
from the dispersion of the soapy lye into the air and waste of the
liquor when it issues at a high pressure. I also connect to the coil or
"refrigerator" a steam pipe from the upper part of the pulp boiler
provided with a cock or valve by occasionally opening which, when
the pressure is up the pressure can be reduced for a short time; this
causes steam to be formed in the body of the pulp, driving out some of

page_text: the liquor which again returns, thus more effectually washing out the
dissolved resin and other impurities whilst the materials are at a high
temperature.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Edward Alfred Cowper in the Great Seal Patent
Office on the 25th October 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
ALFRED COWPER, of No. 6, Great George Street, Westminster, in the
County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-seventh day of April, in the
year of our Lord One thousand eight hundred and seventy-two, in the
thirty-fifth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Edward Alfred Cowper, Her special
licence that I, the said Edward Alfred Cowper, my executors, adminis-
trators, and assigns, or such others as I, the said Edward Alfred Cowper,
my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "In-
PROVEMENTS IN THE PROCESS OF CONVERTING WOOD AND OTHER FIBROUS MATERIALS
INTO PULP, AND IN APPARATUS THEREFOR," upon the condition (amongst
others) that I, the said Edward Alfred Cowper, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their
hands and seals, should particularly describe and ascertain the nature of
the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Edward Alfred Cowper, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained.

page_text: in and by the following statement thereof, reference being had to the
accompanying Drawings and to the figures and letters marked thereon,
that is to say :-
Wood and other materials for producing pulp for making paper have
been boiled down with caustic alkali in several kinds of boilers.
In some cases the application of hot flame direct to the boiler has
produced injury to the boiler or its contents, and in other cases when
circulation pipes have been used there has been great delay in working,
or when the heating has been much urged ruptures in the pipes have
occurred. Loose trays have also been put into pulp boilers with the
view of preventing the contact of the material with the sides of the
boiler, and perforated linings have also been fixed inside such boilers.
Great loss of alkali has generally occurred from the material not
having been soaked with it before it has been placed in the boiler, and
from tho want of means of regulating the amount or time of the cir-
culation of the solution in the boiler when it is sufficiently boiled.
Loss of heat has taken place after boiling a charge at a high pressure
the contents having been allowed to pass out without giving up their
heat properly, so that it might be utilized, and there has been in-
convenience from the steam blowing the soapy lye about, or from
pruning," and again great loss of time and heat has occurred from
the materials not being charged into the boiler as hot as possible, and
from the boiler being allowed to cool between each charge.
Now by my Invention I am enabled to boil the wood or other material
in an efficient manner much more quickly than hitherto, and with a
considerable saving of alkali, and at the same time to avoid the pro-
duction of blacks or burnt pieces of wood, or resin soap in the pulp.
"
In heating the boiler I employ special means to prevent direct action
of the hot flame on the boiler; for this purpose I place the fire at some
distance from the boiler, and I cool down and extinguish the hot flame
by placing between the fire and the boiler a "gridiron" or series of
gridirons" of strong small pipes forming a hot water apparatus, so
that only a mild heat reaches the boiler such as it can well sustain
without injury. The heat absorbed by such hot water apparatus is
then conveyed by circulation to heat a tank containing water, or the
liquor that will next be charged into the boiler, or to heat the boiler
itself, or another boiler.

page_text: In some cases I heat the contents of the boiler by means of a series
of steam pipes in it, supplied with steam at a very high pressure from
a strong boiler of tubular or other construction. The waste heat from
the furnace of the steam boiler may be used to assist in heating the
pulp boiler.
In order to fill and empty the boiler quickly, I charge metal boxes
with the material to be boiled; these boxes are made with hooks or
loops by which they can readily be lifted in and out by a crane or
tackle; they are also provided with trunnions by which they can bo
mounted on trucks to be run from place to place. The boxes have one
or more vertical tubes through them to permit of the circulation of the
liquor in the boiler through them, and each box is provided with a
rotating ventilator valve which can be turned by means of a key passed
through a stuffing box in the top of the boiler, so as to be opened or
closed at pleasure whilst the pressure is up, whereby the hot liquor
is permitted to pass through the pulp moro freely at one time than
at another. Before the boxes are put into the boilers they are filled
with wood which had been previously chopped up, or with such other
materials as are to be operated on, and they are then put to soak in
hot strong lye, which has the effect of soaking the material with the
alkali, so that tho resin and other impurities may be more readily acted
on, and the chemical changes effected which allow of the separation
of the fibres into pulp. The boxes containing the soaked materials aro
then put into the boiler, which is nearly filled up with caustic alkali,
or water, or spent lye, and the valves of the boxes are kept closed
until the whole has been raised to the required temperature, so that
the caustic alkali may act on the material at the high temperature
without dilution. The valves of the boxes are afterwards opened so as
to allow the liquor in the boiler to circulate through the material in
the boxes.
For conveniently discharging the liquor from the boiler, and utilizing
the heat, I employ a coil of pipes or a “refrigerator" through which the
liquor is made to pass as it leaves the boiler, giving its heat to cold
water or cold liquor. The discharge pipe is provided at the end farthest
from the boiler, with a cock or valve which is opened to allow the
liquor to pass into an open tank. Thus the temperature of the liquor
is reduced before its discharge so far as to avoid the inconvenience
arising from the dispersion of the soapy lye into the air, and waste

page_text: of the liquor when it issues at a high pressure. I also connect to the
coil or "refrigerator" a steam pipe from the upper part of the pulp
boiler provided with a cock or valve, by occasionally opening which
when the pressure is up, the pressure can be reduced for a short time,
this causes steam to be formed in the body of the pulp driving out some
of the liquor which again returns, thus more effectually washing out
the dissolved resin and other impurities whilst the materials are at a
high temperature
Fig. 1, Sheet I., shews a vertical section, and Fig. 2, Sheet II., shows
a plan partly in section as at A & partly in top plan view as at B
of a pulp boiler and setting.
Fig. 3, Sheet I., shows a vertical section of part of a boiler with its
guides, and a box with its trunnions and arrangements for catching
hold of the same by tackle; Figs. 4, 5, & 6, Sheet I., shew the
arrangements for influencing the circulation of currents of liquor inside
the boiler.
The pulp boiler C, C, is set upright in brickwork D, D, with flues E, E,
around it, so that the heat derived from a furnace F placed at a distance
from the boiler may pass around the boiler, and by preference it is
made to pass backwards and forwards, embracing the boiler each time
till it enters the chimney E'. There is but a very small portion of
the brick setting in contact with the boiler, so that there is no danger
of the brickwork if hot burning the boiler if empty. The fire Fas
before stated is placed at a considerable distance from the boiler, so
that there shall be no large body of flame beating against the boiler,
and tending to give an irregular and undue heat at certain places.
The flue G, G, G, immediately on leaving the fire F is greatly enlarged,
so that by time the heat comes in contact with the boiler the area
it acts upon is many times the area of the fuel at the fire, so that the
boiler is only subjected to a mild heat such as it can well sustain
without injury.
In some cases when the fuel used is apt to produce long and very
hot flames they are cooled down and extinguished by the interposition
of a "gridiron," or series of pipes charged with water, as shewn by dotted
lines at H, Fig. 1, Sheet I., and Fig. 2, Sheet II. The heat taken up

page_text: by the water in these pipes may be utilized in any way, so that none
of the heat shall be lost. Another means of regulating the temperature
in the flue consists in admitting a regulated quantity of air, and this
regulation may well be effected by a rough pyrometer consisting of
a long metal rod I, reaching down from the upper part of the brick!
setting to a lever acting on a valve J that admits the air.
In some cases pulp boilers have been heated by hot water circulation
pipes worked at a very high pressure, but the effect produced has been
that of heating up the contents of the boiler just where the pipes
entered it, and but little heat has been communicated to other parts of 1
the boiler (except by circulation) owing to the water having already
parted with its surplus heat, so that the pipes have never been hot
throughout their length. Now I obviate this great defect by supplying
a series of steam pipes inside the boiler with steam at a very high
pressure, and drawing the condensed water therefrom as fast as it is 1
condensed, so that the pipes are heated from end to end by the steam
insido them, and constantly give off heat to the contents of the boiler
throughout their whole length, thus heating the boiler very uniformly
and quickly.
The time of filling and emptying a pulp boiler generally occupies a 2
considerable portion of the total time of working a charge, and the
heating up of the contents of the boiler to the boiling point also occupies
considerable time, and if the material to be acted on (and particularly
if it is a compact material like bamboo or wood) has not been thoroughly
soaked with caustic alkali before it is put into the boiler, much time 2
is practically lost, as it takes several hours for the whole to become
perfectly saturated, and this evil is unfortunately exaggerated by any
variation in the density or compactness of portions of the material
being acted on, thus, if one piece of wood contains more resin than
other pieces, it does not saturate so quickly, and thus the cooking or 3
dissolving out of the substances contained amongst the fibres does not
begin so soon as with other pieces that have become saturated quickly,
and the cooking of which commences as soon as the heat is sufficiently
high. Now in order to fill and empty a boiler quickly, to charge it with
materials as hot as possible, to ensure their being acted on equally, and 3
to reduce the time that the materials must remain in the boiler in order
to be thoroughly cooked, I construct a number of boxes K, K, (Figs. 1,
2, 3, 4, 5 & 6, Sheets I. and II.,) in such a manner that they may be

page_text: guided down into the boiler into their proper positions when lowered
down by a crane or tackle and remain truly in position in the centre of
the boiler, there being guides L, L, (Figs. 1, 2 & 3, Sheets I. and II.,)
fixed inside the boiler for the purpose; the crane chain N, Figs. (1 and 3,
Sheet I.,) is provided with a spring catch or self-acting hook M (Fig. 3,
Sheet I.,) to which a light chain or cord O (Fig. 3, Sheet I.,) is attached,
so that when a box K. has been lowered down the catch M (which takes
hold of a cross bar fixed in a central tube in the box) may be released
conveniently, although at the time it may be quite impossible for the
workmen to see at all inside the boiler in consequence of the steam. In
lowering the spring catch or self-acting hook down into the boiler for
the purpose of lifting a box it is guided by the guide bars L, L, and thus
is enabled to take hold of the box with certainty, although the workmen
may not be able to sec.
The mode in which I form the boxes, so that they may be guided
down into their places in the boiler, and may also be supported on light
railway trucks P (Fig. 1, Sheet I.,) for conveyance on the railway Q
(Figs. 1 and 2, Sheets I. and II.,) from place to place, is by attaching
stout pins or trunnions R, R, (Figs. 1, 2, 3, 4, and 6, Sheets I. and II.,)
to the sides of the boxes K, K, to run down between the guide bars L, L,
in the boiler C, such trunnions fitting into notches or recesses in the
frame of the railway truck P, so that the boxes K, K, may be tipped,
and thus conveniently emptied of their contents after they leave the
boiler C, and have been sent along the railway Q to the rolls for ex-
pressing the spent lye from the material being operated on, the boxes
may either be perforated or not. I use a crane by preference for lifting
the boxes K, K, out of the boiler C by means of the chain N, and
depositing them on the trucks P, P, and one crane will conveniently
serve two boilers, where a long range of pulp boilers are properly
arranged. In large pulp works also I use a crane by preference after
the boxes have been filled with the material to be operated on, for
lowering them into a soaking tank nearly filled with strong hot caustic
alkali, where they remain some time until well saturated with the
alkali, and the boxes conveniently stand in a segment of a circle in
this soaking tank, being all served by one crane, which takes them one
by one from the railway trucks P, P, and puts them into the tank, and
puts them again on to the trucks P, P, for conveyance direct to the
pulp boiler C thoroughly hot and ready for receiving the still higher

page_text: temperature that they are subjected to when the boiler is closed and the
cover screwed down tight and heat is applied to the boiler O. The
cover S (Figs. 1, 2, 4, and 5, Sheets I. and II.) of the boiler O may be
secured in any convenient manner, but the mode I prefer is, to provide
a number of wrought-iron or steel screw clamps T, T, to grip the top
ring of the boiler and screw down on to the cover S, the lower ends of
such clamps T, T, being conveniently retained in a hole or recess to keep
them in position, but allow them to fall back when unscrewed, as shown
by dotted lines T (Fig. 1, Sheet I.).
The circulation of the liquor in the boiler to prevent the boiler
becoming dry or "burnt" in any place is provided for in a manner
similar to that described in the Specification of a Patent granted to
Jacob Perkins, 27th August 1831 No. 6154, viz. by having a passage or
passages through each box open at top and bottom, and leaving an
annular space all round the inside of the boiler outside the boxes in
connection with a space at top and bottom of the boiler, so that there
may be a constant flow of liquor down the centre of the boiler to become
heated, whilst the liquor in the space all round the inside of the boiler
on becoming heated will rise upwards and flow over the top of the top
box and down the central opening, thus will a constant agitation be a
produced and the liquor will be continually carried from the bottom
upwards between the boxes and the boiler, and will prevent its becoming
burnt, and at the same time the heat will be more quickly taken up by
the fluid and distributed more uniformly through the boiler. I further
provide for the control of the circulation of the liquor by ventilator
valves X (Figs. 5 and 6, Sheet I.,) attached to spindles Y (Figs. 5 and 0,
Sheet I.,) turning in bearings in each box and capable of being turned by
a key or spindle Z (Figs. 5 and 6, Sheet I.,) that is mounted on the cover
of the boiler and passes through a stuffing box fixed thereon, the bottom
end of such key or spindle Z being made to take hold of the spindle of 3
the ventilator valve X, and thus turn it when the upper end of the
spindle Z above the stuffing box (and therefore outside the boiler) is
turned by any means; thus the ventilator valves X to the openings
through the boxes can be opened or shut at pleasure and the circulation
can be thereby controlled.
I construct the stuffing box as follows:-In order to prevent the lyc
in the boiler from coming into intimate contact with the hemp, metal,
or other material used for packing the stuffing box, I construct a small
3

page_text: closed chamber T (Fig. 4, Sheet I.,) some few inches in height through
which the spindle passes, and I form a stuffing box at the bottom of this
chamber and another at the top so as to form an enclosed space round
about the spindle; I then attach a pipe V (Fig. 4, Sheet I.,) to this
chamber and supply it with water from a cistern or otherwise, at a
slightly greater pressure than there is in the boiler at the time, so that
if there is any leak through the lower stuffing box a little water leaks
slowly into the boiler, or if the top stuffing box leaks a little water lcaks
out and no injury is done to the packing; I also when necessary allow
the water to circulate through the chamber so as to keep it at a lower
temperature than the boiler, and this may be done by a circulation coil
exposed in the air in order to allow it to part with heat by radiation
and condensation, or by a circulation cistern or close tank. The pressure
may be kept up in the chamber and coil or tank in any known manner,
but I prefer as the best means with which I am acquainted that a small
steam pipe W (Fig. 4, Sheet I.,) should be brought up from the cover of
the boiler and the steam should be allowed to press on water in a pipe
or second small tank and force some water into the chamber before
named, as there will then always be a little more pressure in the chamber
than in the boiler equal to the head of water in the small tank above
the level of the top of the boiler. Thus both the stuffing boxes will be
supplied with water cool and at a pressure slightly greater than the
pressure in the boiler whatever that may be at the moment.
In some cases instead of the ventilating valve X (Figs. 5 and 6,
Sheet I.,) being connected to the spindle passing through the stuffing box,
a screw or ventilator X (Fig. 4, Sheet I.,) is connected to the spindle Z
to be employed for influencing the circulation of the liquor in the
boiler, it being understood that the stuffing box and spindle shown in
this Figure are similar to those used in cases where the ventilating valve
) is used.
Having thus described the nature of my Invention, and in what
manner the same is to be performed, I would have it understood
that I do not claim generally reducing wood, bamboo, and other
materials to the state of pulp by subjecting them to the action of
3 caustic alkali at high temperatures in a boiler, nor do I claim generally
discharging the liquor from such boiler through a refrigerator, but I
claim,-
First, The combined process substantially as herein described for
reducing wood, bamboo, and other materials to the state of pulp, such

page_text: process consisting of the successive operations of soaking the materials
to be operated on in boxes in hot caustic alkali, charging the hot boxes
containing the hot soaked materials into the pulp boiler by crane and
tackle, subjecting the materials to the necessary action in the boiler
with regulated circulation of the liquor in the boiler and through the
boxes, discharging the spent liquor from the boiler through a refri-
gerator and lifting the boxes by crane and tackle from the boiler and
loading them on trucks.
Second. The interposition of pipes charged with water between the
furnace of a pulp boiler, and the boiler itself so as to moderate the
intensity of the heat before it is permitted to act on the boiler, substan-
tially as hercin described.
Third. The use for containing the materials to be reduced to pulp of
boxes constructed with trunnions whereby they are guided to their place
in the boiler or mounted on trucks conveniently for tipping, and with
passages for circulation through them and means for readily lifting and
lowering them, substantially as herein described.
Fourth. The use for influencing the circulation through such boxes
of ventilator valves worked from outside the boiler by a spindle passing
through a stuffing box, substantially as herein described.
In witness whereof, I, the said Edward Alfred Cowper, have
hereunto set my hand and seal, this Twenty-fifth day of October,
in the year of our Lord One thousand eight hundred and
seventy-two.