IMPROVEMENTS IN OR CONNECTED WITH THE PURIFICATION OF COAL GAS, AND IN THE APPARATUS EMPLOYED THEREIN."
Year: 1880

page_text: LETTERS PATENT to Charles Clement Walker, of Lilleshall, in the County of
Salop, and William Thomas Walker, of Highgate, in the County of Middlesex,
for an Invention of "IMPROVEMENTS IN OR CONNECTED WITH THE PURIFICATION
OF COAL GAS, AND IN THE APPARATUS EMPLOYED THEREIN."
PROVISIONAL SPECIFICATION left by the said Charles Clement Walker and
William Thomas Walker at the Office of the Commissioners of Patents on
the 7th February 1880.
CHARLES CLEMENT WALKER, of Lilleshall, in the County of Salop, and WILLIAM.
THOMAS WALKER, of Highgate, in the County of Middlesex. "IMPROVEMENTS IN
OR CONNECTED WITH THE PURIFICATION OF COAL GAS, AND IN THE APPARATUS
EMPLOYED THEREIN."
Our Invention relating to the purification of coal gas has for its object the
condensing or screening of tar held in suspension or carried along in coal gas after
such gas has been cooled in the condensing apparatus used in gas works. It is
desirable that the operation of removing tar from coal gas should be completely
performed before the gas enters the scrubber for its further purification from
ammonia. In order to effect this we use a vessel circular, square, or of other
convenient form and in this we place perforated screens of wrought or cast iron
or other suitable material through which the gas is screened from tar in its passage
through the openings of the same.
We make the vessel of considerable height or length and of an area much
larger than the superficial area of its feed pipe, not only for the purpose of being
able to give a total equivalent area of the perforated screens to its feed pipe, but
also for allowing the gas to expand itself to, say, for example, six times or more of
the capacity of the feed pipe in order that fine globules of tar held in suspension
and carried along by the gas may be brought into contact with each other by the
necessary breaking up and contraction of the numerous small streams of gas in
passing through the small holes of the screens. For example, after passing through
one of the screens the gas again expands to the full capacity of the body of the
vessel, and the same operation of contraction is again repeated at the next
screen, causing the fine globules of tar to unite upon or with each other and

page_text: become deposited, until the gas passing through the top screen is entirely freed
from tar.
We also avail ourselves of the advantages of height or length for the means of
controlling and varying the dimensions of the passage of the interior necessary to
meet the fluctuations in the production of gas in winter and summer by making all
or some of the upper perforated screens capable of being turned into a position at
right angles to their normal position, their axes being carried through stuffing boxes
to the exterior of the condenser so as to enable them to be turned by the aid of
suitable handles.
These screens while filling up the internal capacity of the vessel have their
perforated surfaces through which the gas must pass of less area, say, for example,
reduced to one half or one fourth by non perforation of the surface. When turned
in one direction they allow the gas to pass by them freely; on turning them in the
reverse direction they fill the bore of the vessel, and the volume of gas is then
screened through their openings which are of suitable area for the production of gas
at the time necessary to use them; or we may employ disc valves which, being
brought into contact with the screens, shut off or intercept the required portion of
the perforated surface, whereby a similar result is obtained.
The lower screens have larger openings than those above, which latter are
gradually contracted in dimensions as they have less work to perform by reason
of the amount of tar screened and thrown down from the gas before reaching
them.
We are enabled also to construct the area of perforated surfaces of such dimensions
so as to pass the gas through such perforated surfaces without the disadvantage of
the excessive injurious back pressure which has heretofore attended all efforts in
this direction and proved a serious barrier to success.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Clement Walker, and William Thomas Walker in the Great
Seal Patent Office on the 7th August 1880.
CHARLES CLEMENT WALKER, of Lilleshall, in the County of Salop, and WILLIAM
THOMAS WALKER, of Highgate, in the County of Middlesex. "IMPROVEMENTS IN
OR CONNECTED WITH THE PURIFICATION OF COAL GAS, AND IN THE APPARATUS
EMPLOYED THEREIN."
Our said Invention relating to the purification of coal gas has for its object the
condensing or screening of tar held in suspension or carried along in coal gas, after
such gas has been cooled in the condensing apparatus used in gas works, and before
the gas enters the scrubber for its purification from ammonia. In order to effect
this object we employ in combination with the ordinary or other suitable condensing
apparatus a vessel, column, or conduit, circular, square, or of any other convenient
form, and in this we place screens of perforated steel or wrought or cast iron or
other suitable perforated or reticulated material, through which the gas (which has
been cooled in the condensing apparatus) is screened from tar in its passage through
the openings of the same, the gas thus freed from tar being thence conducted into a
scrubber or other suitable apparatus for its purification from ammonia.
In order that our said Invention may be perfectly understood, we shall now
proceed more particularly to describe the same, and for that purpose shall refer to
the annexed Drawing, which represents a sectional elevation of a portion of a
condensing apparatus of the description known as "Walker's Annular Condenser "
with the screening apparatus, which forms the subject of our present Invention,
applied thereto.
A, A, A, represent a series of columns which are in intercommunication by means
of pipes B, B, B, the whole together forming a condensing apparatus of the typo
known as "Walker's Annular Condenser," through which the gas is caused to pass
in the direction indicated by the arrows. When condensing apparatus of this type
is adopted, we use a sufficient number of these columns to ensure that the gas
leaving the lower part of the last column at a shall be sufficiently cooled, and we
connect to the last column a tar screening vessel or column C, containing a series of
screens D, D', D2, D3, D4, D5, D6, through which the ascending gas is caused to pass
in order to have the tar which is in suspension or carried along with the gas
separated therefrom by the gas being finely divided by its passage through the
screens.
We make the vessel or column C of considerable height and of an area much
larger than the superficial area of its feed pipe, not only for the purpose of being
able to give a total equivalent area of the screens to its feed pipe, but also for
allowing the gas to expand itself to, say, for example, four times or more of the
capacity of the feed pipe in order that fine globules of tar held in suspension and
carried along by the gas may be brought into contact with each other by the
necessary breaking up and contraction of the numerous small streams of gas in
passing through the small holes of the screens. For example, after passing through
one of the screens the gas again expands to the full capacity of the body of the
vessel or column, and the same operation of contraction is again repeated at the
next screen, causing the fine globules of tar to unite upon or with each other, and
become deposited until the gas passing through the top screen is entirely freed
from tar.
We also avail ourselves of the advantages of height or length for the means of
controlling and varying the dimensions of the passage of the interior necessary to
meet the fluctuations in the production of gas in winter and summer, by making all
or some of the upper screens capable of being turned into a position at right angles

page_text: to their normal position, their axes being carried through stuffing boxes to the
exterior of the condenser so as to enable them to be turned by the aid of suitable
handles.
In our Drawings we have shewn the three upper screens D*, D³, and Dº, as thus
arranged so as to be capable of being turned on axes b, the said axes being extended
through stuffing hoxes to the exterior and there provided with handles c for the
facility of their manipulation. The screen D is shewn in action, the gas being
caused to pass through its openings whilst the screens D5, D6, are represented out of
action, the said screens being assumed to have been turned to a position at right
angles to their normal position so as to leave a free unobstructed passage for the
escape of the gas. It should be observed that the upper screens D³, Do, whilst in
their normal position filling up the internal capacity of the vessel or column have
their perforated portions of a reduced aggregate area suitable for the production of
gas at the time when they are required to be used, their annular periphery for a
suitable width being left unperforated.
Similarly the lower screens have each larger openings than the screen above
them; as for example, the screen D has larger openings than the screen D¹, and the
screen D¹ has larger openings than the screen D2, and so on in succession throughout
the series of screens, the openings being gradually contracted in dimensions in
ascending the column as the upper screens have less work to perform by reason of
the amount of tar screened and thrown down from the gas before reaching them.
In order that the area of perforated surface and the dimensions of the holes may
be suited to the special work they have to perform, videlicet, the screening-out of
tar, and to obviate the necessity for enlarging the holes for the return of the tar so
screened out, as well as for the passage of the ascending gas, the surface of the lower
screens is made convex so as to allow the tar to flow readily to the sides where it
is received into annular seal cups d, and thence overflows down the sides of the
vessel or column whilst the gas only (unclogged by descending tar) ascends through
the perforations of the screens which are made of suitable dimensions and mesh to
perform their own proper functions.
If desired, in lieu of making the upper screens themselves moveable for the gas at
the upper part in summer or whenever the production of gas is diminished, we may
form the said screens with perforations of the requisite maximum aggregate area
and employ disc valves E, as shewn in dotted lines, applied to the screens D, D¹, D², D³,
in the column C, which valves by being brought nearer to or moved further from the
screens, the passage of the gas may be regulated as required to suit the demand,
or a part only of the perforated area of the screens may be closed by the disc
valves having a projecting ring on their under faces, as shewn in the Drawing
at F, F1, F2, F³.
The disc valves are attached to and actuated by a centre rod or spindle E¹ passing
through the column C and raised or lowered so as to adjust the position of the
valves E by a screw nut G, as shown, or by a lever movement placed at the top of
the column, and for greater convenience a rod or shaft extending down the outside
of the column C may be connected by suitable gearing to the nut G so as to enable
the valves E to be worked from the lower part of the apparatus, or if desired the
centre rod or spindle E¹ may be passed through a stuffing box in the bottom or side
of the column to enable it to be worked from below.
For the purpose of cleaning out the apparatus should it ever be found necessary
I introduce steam (either at the top or bottom thereof) by means of a tube fitted
with a steam cock for regulating the supply of steam as required.
It is obvious that although we have described the screening vessel or column C as
vertical it may be placed horizontally, and although in the example assumed the
said vessel or column is described as arranged in combination with what is known
"Walker's Annular Condenser," it may be employed in combination with a
condenser of any other suitable construction.
as
The gas having been screened or freed from tar by means of the vessel or column C

page_text: is next conducted into a scrubber of any one of the well known types or other
suitable apparatus, in order to be purified from ammonia.
By the arrangement of the screens herein before described we are enabled to effect
the passage of the gas for the complete separation of the tar therefrom without the
disadvantage of excessive or injurious back pressure.
Having now described and particularly ascertained the nature of our said
Invention and the manner in which the same is or may be used or carried into
effect, we would observe in conclusion that what we consider to be novel and
original, and therefore claim as the Invention secured to us by the hereinbefore in
part recited Letters Patent is,-
The employment between the condensing apparatus in which coal gas is cooled
and the scrubber or other apparatus in which the gas is purified from ammonia,
of a vessel, column, or conduit, provided with screens for the purpose of condensing
or separating the tar held in suspension or carried along. in the gas, the said
screens being constructed and arranged so as to operate substantially in the
manner hereinbefore described.
In witness whereof, I, the said William Thomas Walker, on behalf of myself
and the said Charles Clement Walker, have to this our Specification set my
hand and seal this Fifth day of August, One thousand eight hundred and
eighty.
WILLIAM THOMAS WALKER. (L.S.)