IMPROVEMENTS IN THE MANUFACTURE OF ILLUMINATING GAS FROM GAS TAR OIL OR FROM GAS TAR
Year: 1867

page_text: LETTERS PATENT to Thomas Crow, of West Ham, in the County of Essex,
Tar Distiller, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF ILLUMINATING GAS FROM GAS TAR OIL OR FROM GAS TAR.”
Sealed the 17th December 1867, and dated the 25th June 1867.
PROVISIONAL SPECIFICATION. left by the said Thomas Crow at the Office
of the Commissioners of Patents, with his Petition, on the 25th June
1867.
I, THOMAS CROW, of West Ham, in the County of Essex, Tar Distiller,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN THE
MANUFACTURE OF ILLUMINATING GAS FROM GAS TAR OIL OR FROM GAS TAR," to be
as follows:-
The oil of gas tar (commonly called creosote or dead oil) is extracted from
the gas tar in the usual way, and is placed in a tank or reservoir situated at
any convenient height; from this tank the oil flows down through a pipe
into a small heated vessel or vaporizer which may conveniently be in the form
of a dee retort. A continuous stream of the oil is allowed to flow over the
bottom of this vessel only just sufficient in quantity to wet it, and in doing so.
the oil is instantly converted into vapour. The vapour so formed passes by a
pipe into a superheater which is maintained at a bright red heat. The outlet

page_text: of this superheater must be sufficiently small in proportion to the generating
capacity of the vaporizer so as to maintain a constant accumulation of vapour
and consequent high state of pressure in the superheater. The vapour thus
exposed simultaneously to a great heat and a high pressure is converted into
permanent gas of great illuminating power, which can be dealt with as ordinary
coal gas. Gas tar alone may be similarly treated to obtain illuminating gas.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Crow in the Great Seal. Patent Office on the 24th
December 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
CROW, of West Ham, in the County of Essex, Tar Distiller, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fifth day of June, in the year of our Lord One
thousand eight hundred and sixty-seven, in the thirty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Thomas Crow, Her special licence that I, the said Thomas Crow, my executors,
administrators, and assigns, or such others as I, the said Thomas Crow, 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 "IMPROVEMENTS IN THE MANUFACTURE OF ILLUMINATING
GAS FROM GAS TAR OIL OR FROM GAS TAB," upon the condition (amongst others)
that I, the said Thomas Crow, my executors or administrators, by an instru-
ment 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 imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas Crow; do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the. Drawing hereunto annexed, that is to
say:
The oil of gas tar (commonly called creosote or dead oil) is extracted from

page_text: the gas tar in the usual way, and when obtained is placed in a tank or reservoir
situated at such a height as to produce the degree of pressure required; from
this tank the oil flows down through a pipe into a heated vessel or vaporizer.
A continuous stream of the oil is allowed to flow over the bottom of the
vaporizer only just sufficient in quantity to wet it, and in so doing it is instantly
converted into vapour. The vapour so formed passes into a superheater which
is maintained at a bright red heat, or even at a greater heat. The outlet of
this superheater must be sufficiently small in proportion to the generating
capacity of the vaporizer so as to maintain a constant accumulation of vapour
and consequent high state of pressure in the superheater. The vapour thus
exposed simultaneously to a great heat and a high pressure is converted into
permanent gas of great illuminating power, which can be dealt with as
ordinary coal gas. Gas tar itself may be similarly treated to obtain illuminating
gas.
I do not limit myself to any particular arrangement or form of apparatus
for carrying my Invention into effect, as it will vary according to the circum-
stances of its application, but in all cases the same principle of construction
and action will be retained, that is to say, first, the supply of oil will be con-
tinuous and at a pressure due to the elevation of the oil reservoir; secondly,
the passage of the gas from the apparatus will be so proportioned as to produce
a back pressure within; and, thirdly, the heating surface of the vaporizer and
superheater will be such as to admit of the whole of the vapor generated being
superheated before it passes out.
The accompanying Drawing represents in vertical section one form or
arrangement of apparatus which may in some cases be advantageously adopted.
A, A, is a structure of fire-brick heated by one or more furnaces B; C is the
retort oven containing pipes D, E, F, G, arranged as shown in such manner
that there is a continuous passage in alternate directions through them. The
lowest pipe D forms the vaporizor, and the other pipes E, F, G, form the
superheater. The products of combustion from the furnace B enter the
oven C at the sides thereof to heat the pipes; these products may pass off at
any convenient part into the chimney or uptake. The pipes D, E, F, G, are
provided with screw plugs or caps I, I, which may readily be removed when
the pipes require cleaning. K, K, are doors one at each end of the oven C;
Lis the furnace door, and M the ash-pit; N is the oil tank or reservoir, from
which the oil flows in a continuous manner by a pipe O provided with a cock P
into the pipe or vaporizor D; Q is a pipe leading from the uppermost pipe G
of the superheater to an ordinary condenser. The passage through this pipe
is so proportioned as to produce a back pressure in the apparatus; it is pro-

page_text: vided for this purpose with a cock or valve R to regulate the outlet of the
gas. S is a gauge to indicate the pressure.
The action is as follows: The oil flows from the tank N in a very small
continuous stream by the pipe O into the front end of the pipe or vaporizor D;
it becomes vaporized therein by the heat of the furnace, and the vapor rises
from the back end of the pipe D into the pipe E, passes through this pipe
and through the pipes F and G, and finally'issues in a superheated state by the
pipe leading to the condenser. The pressure produced in the apparatus
owing to the smallness of the outlet by the pipe Q brings all the particles of
the vapour into close contact with each other, and produces equality of
temperature throughout its whole volume.
And 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 manufacture
of illuminating gas substantially in the manner herein-before described.
In witness whereof, I, the said Thomas Crow, have hereunto set my hand
and seal, this Twenty-fourth day of December, in the year of our Lord
One thousand eight hundred and sixty-seven."
THOMAS CROW. (L.S.)