AN IMPROVED BOILER
Year: 1883

page_text: LETTERS PATENT to George Knowles of Billiter House Billiter Street in the
City of London Civil Engineer for an Invention of “AN IMPROVED BOILER
PROVISIONAL SPECIFICATION left by the said George Knowles at the
Office of the Commissioners of Patents on the 3rd July 1883.
GEORGE KNOWLES of Billiter House Billiter Street in the City of London Civil
Engineer "AN IMPROVED BOILER OR DIGESTER FOR EFFECTING CHEMICAL OR
OTHER OPERATIONS"
My Invention consists of an improved boiler or digester for effecting chemical or
other operations and has been designed with special reference to the boiling or
digesting of wood vegetable or other substances by means of sulphurous acid so as
to produce pulp for paper making or similar uses and also for the extraction of
saccharine colouring and other matters.
My improved boiler or digester is composed of a closed steam tight vessel
containing another vessel of somewhat smaller diameter the space between the two
vessels being filled or nearly so with water or other liquid. If the inner vessel
be filled to the same level as the outer vessel with a liquid or solution of the same
density the hydrostatic pressure on the inside and outside of the inner vessel will
naturally be equal. The upper part of the outer vessel forms a steam chest or
dome and the inner vessel is in free communication therewith the edge of this
vessel projecting upwards above the surrounding liquid. The inner vessel is
provided with one or more pipes or coils by means of which its contents can be
heated by steam or hot water. The apparatus is provided with openings for
charging and for emptying the contents when necessary.
Such being the construction of the apparatus it will be understood that when
the inner vessel is charged with the solution or material to be boiled or digested
and steam or hot water is made to circulate through the pipes or coils, the solution
in the inner vessel will first receive the heat from the heating coils and will after-
wards communicate it through the sides and by the top to the liquid in the outer
vessel; also that as steam or vapor is formed and accumulates in the dome it will
[Price 61

page_text: .
exert an equal pressure on the liquids in the two vessels and thus tend to preserve
in equilibrium the pressures on the inside and outside of the inner vessel no
matter how high the pressures may be. This equalization of the pressure on the
inside and outside of the inner vessel permits of this vessel being made of a much
lighter construction than would otherwise be necessary and also allows it to be
made of materials unfitted to resist high strains. The liquid in the inner vessel
does not come into contact with the sides of the outer vessel which vessel has alone
to resist the strains due to the pressure under which the boiling takes place. The
sides of the two vessels are not connected to each other; they can therefore
expand and contract independently and without liability of injuring each other.
The outer vessel should be constructed of iron steel or other material suitable
for making boilers. The inner vessel may be made of any material capable of
resisting the action of the solution used in the process of digesting. If acids are
to be used it may be made of lead or other metal or alloy which is not materially
affected thereby; or of porcelain pottery earthenware glass clay wood or other
substance which will resist the heat and the action of the acid. It is not however
necessary to make it of a material which is absolutely proof against the action of
acids because it can be readily removed when necessary and replaced with another
without lessening the efficiency of the outer vessel.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Knowles in the Great Seal Patent Office on the 31st December
1883.
GEORGE KNOWLES of Billiter House Billiter Street in the City of London, Civil
Engineer "AN IMPROVED BOILER OR DIGESTER FOR EFFECTING CHEMICAL OR
OTHER OPERATIONS
"
My invention consists of an improved boiler or digester for effecting chemical or
other operations and has been designed with special reference to the boiling or
digesting of wood, vegetable or other substances by means of sulphurous acid so as
to produce pulp for paper making or similar uses, and also for the extraction of
saccharine, colouring and other matters.
My improved boiler or digester is composed of a closed steam tight vessel con-
taining another vessel of somewhat smaller diameter the space between the two
vessels being filled or nearly so with water or other liquid. If the inner vessel be
filled to the same level as the outer vessel with a liquid or solution of the same
density the hydrostatic pressure on the inside and outside of the inner vessel will
naturally be equal. The upper part of the outer vessel forms a steam chest or
dome and the inner vessel is in free communication therewith, the edge of this.
vessel projecting upwards above the surrounding liquid.
The inner vessel is.
provided with one or more pipes or coils by means of which its contents can be
heated by steam or hot water.. The apparatus is provided with openings for
charging and for emptying the contents when necessary.
Such being the construction of the apparatus it will be understood that when
the inner vessel is charged with the solution or material to be boiled or digested
and steam or hot water is made to circulate through the pipes or coils, the solution
in the inner vessel will first receive the heat from the heating coils and will after-
wards communicate it through the sides and by the top to the liquid in the outer
vessel; also that as steam or vapor is formed and accumulates in the dome it will
exert an equal pressure on the liquids in the two vessels and thus tend to preserve
in equilibrium the pressures on the inside and outside of the inner vessel no matter
how high the pressures may be. This equalization of the pressure on the inside
and outside of the inner vessel permits of this vessel being made of a much lighter
construction than would otherwise be necessary and also allows it to be made of
materials unfitted to resist high strains. The liquid in the inner vessel does not come
into contact with the sides of the outer vessel which vessel has alone to resist the
strains due to the pressure under which the boiling takes place. The sides of the
two vessels are not connected to each other; they can therefore expand and contract
independently and without liability of injuring each other.
The outer vessel should be constructed of iron, steel or other material suitable
for making boilers. The inner vessel may be made of any material capable of
resisting the action of the solution used in the process of digesting. If acids are
to be used it may be made of lead or other metal or alloy which it is not materially
affected thereby; or of porcelain, pottery, earthenware, glass, clay, wood, or other
substance which will resist the heat and the action of the acid. It is not however.
necessary to make it of a material which is absolutely proof against the action of
acids because it can be readily removed when required and replaced by another
without lessening the efficiency of the outer vessel.
The annexed drawings illustrate my invention: Figure 1 being a vertical section,
and Figure 2 a horizontal section of one of my improved boilers or digesters. a is
a closed steam tight vessel and b is another vessel of somewhat smaller diameter

page_text: placed within it; the space between a and b is filled or nearly so with water or
other liquid. The upper part of the vessel a forins a steam chest or dome c and
the vessel b is in free communication therewith the edge of this vessel projecting
above the surrounding liquid; d d are coils in the vessel b by means of which its
contents can be heated by steam or hot water. e is a man hole with cover for
charging the vessel b and f is a valve by which the contents can be discharged. It
will be seen that the sides of the two vessels a and b are not connected to each
other; they can therefore expand and contract independently.
Figure 3 represents a modified form of apparatus in which instead of the coils d d
I employ, vertical pipes d d arranged all around the inner vessel near the circum-
ference of same. These pipes when heated by steam are provided with inner
return pipes so that the water of condensation which tends to collect in the bottom
of the pipes dd is forced by the steam up the inner pipes and escapes at the top
of-same.
The boiler or digester should be fitted with an inlet and outlet for water, a steam
pressure guage, a safety valve, a blow off cock, steam stop valves, cocks and tubes
for testing the solution and other like requisite appliances as will be well
understood.
Having now described the nature of my said invention and in what manner the
same is to be performed I declare that I claim :-
The boiler or digester constructed substantially as hereinbefore described, that
is to say, with an inner and an outer vessel having water or other liquid in the
space between them the upper part of, the outer vessel forming a steam dome with
which the inner vessel freely communicates and the inner vessel being provided
with means for heating the contents thereof, all substantially as and for the
purpose set forth.
In witness whereof I the said George Knowles have hereunto set my hand
and seal this twenty first day of December One thousand eight hundred and
eighty three.