IMPROVEMENTS IN THE DISTILLATION OF COAL TAR
Year: 1879

page_text: LETTERS PATENT to George Careless Trewby, Civil Engineer, and Henry
William Fenner, Manufacturing Chemist, both of Beckton, in the County of
Essex, for the Invention of "IMPROVEMENTS IN THE DISTILLATION OF COAL
TAR."
Sealed the 2nd March 1880, and dated the 9th September 1879.
PROVISIONAL SPECIFICATION left by the said George Careless Trewby and
Henry William Fenner at the Office of the Commissioners of Patents on the
9th September 1879.
:
GEORGE CARELESS TREWBY, Civil Engineer, and HENRY WILLIAM FENNER,
Manufacturing Chemist, both of Beckton, in the County of Essex. "IMPROVEMENTS
IN THE DISTILLATION OF COAL TAR."
The object of the Invention is to facilitate the distillation of coal tar.
In carrying out our improvements we proceed gradually, as heretofore, in the
heating of the still by the fire heat employed, or by heat otherwise obtained, until
the heat obtained in the still is above that of steam.
When the tar in the still has become heated to a temperature of at least 212°
Fah. we then or at such other period determined upon, according to the quality or
character of the tar under operation, inject therein steam at a comparatively low
pressure and temperature, and by the further heat obtained from the tar the injected
steam becomes highly heated, and in proportion to the increased heat given to such
steam so is the extent of distillation facilitated:
We inject the steam into the still by means of a suitable pipe passed to near the
lower surface of the still, where it is formed into a coil or coils perforated for the
escape of the steam in a highly heated state in numerous jets amongst the coal tar.
By these means time and fuel are saved in the operation, whilst carbonization
of the pitch at the bottom of the still is prevented, and greatly increased yield of
valuable product is realized.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Careless Trewby and Henry William Fenner in the Great
Seal Patent Office on the 6th March 1880.
"
GEORGE CARELESS TREWBY, Civil Engineer, and HENRY WILLIAM FENNER,
Manufacturing Chemist, both of Beckton, in the County of Essex. IMPROVEMENTS
IN THE DISTILLATION OF COAL TAR."
In the distillation of coal tar as carried out up to the present time the beat
generally employed for the purpose is that obtained by external fire heat, and it
has been found necsssary to employ that heat at a much higher temperature for the
elimination of the heavier products than their true distilling points, and for two
reasons,-
1st. The resistance offered to the escape of the vapours by the large proportion
and depth of residual products contained in the still.
2nd. The bad heat conducting properties of the said residuals. This excessive
temperature so applied has resulted in the decomposition and loss of valuable
products, together with an accumulation of coke on the surfaces of the still more
immediately exposed to the action of the fire. In consequence it has been found
necessary periodically to stop the stills in order to remove the coke 30 accumulated.
When heavy tars have been worked this has necessitated a frequent renewal of still
bottoms, and together with loss of working capacity has been a serious drawback
to tar distillers.
The object of the present Invention is to overcome these difficulties, and the
character of the agitation obtained continually renews the contact of the boiling
tar or pitch with the surfaces of the still exposed to the fire, thereby preventing
coking, and at the same time providing a force for the immediate expulsion of the
vapours when they reach their true distilling point.
It has been found by tar distillers under the old system impossible to use coke
or other highly heating fuel on account of the concentration of the heat in the
bottom of the still, but in pursuance of these improvements this evil is obviated,
and coke or fuel of any kind can be employed.
But that the Invention may be the better understood I will, by the aid of the
accompanying Drawings, proceed to describe parts, in connection with a still for
carrying out our improvements.
Figure 1 shews a vertical section, and Figure 2 a horizontal section of a still
with parts arranged to carry our improvements into effect. In both Figures the
same letters apply to corresponding parts.
To effect the above improvements we employ, steam at any convenient pressure,
and proceed as follows:-The still is worked in the usual way by fire heat until
the lighter products have passed over. Steam is then turned in by the cock A, and
is made to traverse the pipe B which is connected with the smaller tubes C, C, C.
The two outside lead into the ring D, the centre into the branches E, which again
lead into numerous smaller outlet pipes or passages F. There are as many of these
outlet.passages employed as may be found desirable. From the pipe B the steam
is distributed amongst the three columns or tubes C, C, C, and by, the ring D, and
thence by the branches E is again subdivided, ultimately striking the gutter and
the crown of the still bottom by the outlets F. The steam entering at A is in fact
split up and so subdivided that it becomes by its passage down the tubes through
the vapours and body of the boiling tar or pitch super-heated to about the tempe-
rature of the said tar or pitch, which of course renders all risk of boiling over
impossible, whilst the increased pressure from the increased heat and expansion of

page_text: steam causes intense agitation of the coal tar in the still, and the expulsion of the
vapours with greatly increased rapidity. After the admission of the steam through
the pipe B, as stated, it is no longer necessary to increase the fire under the still,
but merely desirable to keep it sufficiently alive to maintain the contents of the
still at an even temperature, which may be seen by reading a thermometer placed
in a tube on top of the still, the end of that tube inside the still being closed.
Having thus described our Invention, we would have it understood that we are
aware that it heretofore has been proposed to introduce steam and gases into stills
for this distillation of coal tar, but so far as we have been able to ascertain such
efforts have not been successful, and have not been made practically available; but
what we claim is, the improvements in the distillation of coal tar, whereby steam
at a comparatively low temperature becomes superheated by being conducted
through the heated coal tar in the still, and is thence distributed in numerous jets
immediately over the bottom surface of the interior of such still amongst the coal
tar or pitch under operation in manner and for the purpose substantially as
described.
In witness whereof, we, the said George Careless Trewby and Henry William
Fenner, have hereunto set our hands and seals, this Fifth day of March, in
the year of our Lord One thousand eight hundred and eighty.