Improvements in the Decomposition of Mineral Oils for the Production of Illuminating Gas.
Year: 1892

page_text: Date of Application, 5th July, 1892
Complete Specification Left, 1st Apr., 1893-Accepted, 24th June, 1893
Improvements in the Decomposition of Mineral Oils for the
Production of Illuminating Gas.
WILLIAM YOUNG, Chemical Engineer, Priorsford, in the Town and County of
Peebles, North Britain, and ALEXANDER BELL, Manager of Gas Works, in the
Town and County of Peebles, North Britain, do hereby declare the nature of this
invention to be as follows:-
Our invention has for its object to increase the amount of light obtainable from
a given quantity of mineral oil when such oil is decomposed by heat in order to
produce illuminating gas, and it consists of an improved method of decomposing
the oil.
Hitherto when mineral oils have been decomposed for the production of illu-
minating gas, either alone or commingled with some material producing a gas of
lower illuminating power, such as coal, or when the oils have been diffused in the
form of vapour through water gas, the retorts have been heated to such a tem-
perature that the oil is decomposed at one single operation in a limited period of
time; the object being to have the temperature as high as will produce the
smallest quantity of liquid products, and yet sufficiently low as not to produce an
excessive deposit of sooty carbon. Considerable difficulty has been experienced
in maintaining the suitable temperature, and the sooty carbon deposits have proved
a great source of inconvenience while the excess of liquid products has constituted
a serious loss.
We have discovered that these difficulties can be avoided and that a much larger
illuminating value can be obtained from a given quantity of oil by subjecting it,
either alone or in the presence of a poor gas such as is obtained from coal or by
the decomposition of water, to the repeated and fractional decomposing action of
heat of a temperature lower than that which, as at present employed, decomposes
the oil at one operation; and in such a manner that the heat shall act as far as
possible upon the oil as radiant heat, contact being avoided as much as can be
between the oil and oil vapours and the heated surface of the retort by having the
area of the retort large in proportion to its surface.
Our invention may be carried into effect by a variety of arrangements. The
decomposing vessels or retorts may be placed either vertically or horizontally.
The vertical retorts may be of any form of cross section, and any convenient
number may be placed in an oven surrounded with brickwork and heated to the
desired temperature in any convenient manner; but preference is given to having
the temperature higher at the bottom than at the top. These vertical retorts are
provided with a series of central trays or shelves or their equivalents, either
suspended from the top or supported in some other manner-in any case in such a
way that they can be conveniently removed for cleaning or can be conveniently
cleaned in situ. The outlet for the decomposed products is taken from the top of
the retort and led to any convenient forms of washing or scrubbing and condensing
arrangement.
When the oil has to be decomposed in the presence of a poor gas each of the
retorts is connected preferably at its lower end by a branch pipe to the trunk
main supplying such poor gas, but the poor gas may be commingled with the
decomposed products from the oil after they have left the retorts, preferably
however while hot as the poor gas is thereby better carburetted.

page_text: The retorts are heated to a suitable temperature which, while it varies slightly
for different grades of oil, needs to be kept considerably under that which causes
sooty matter to be present in the gas. This desired temperature is readily
ascertained from the goodness or otherwise of the final results.
The oil to be decomposed is run into the washer or scrubber where it acts as the
medium for washing or scrubbing the gas coming from the retorts. The oil flowing
from the bottom of the washer or scrubber is run in regulated streams into the
upper trays or shelves in the retorts and thence flows down from tray to tray, being
exposed in its descending course to the heat radiated from the walls of the retorts.
And as the mineral oil consists of a series of hydrocarbons of different boiling
points, these different grades are volatilised as they in their descent in the retort
reach their boiling points at distances from the outlet of the retort which increase
as the boiling points rise. Thus the vapours into which the different grades of oil
are successively converted, and each of which is in its turn less easy to decompose,
are subjected to correspondingly higher temperatures and longer periods of time.
The products resulting from this fractional decomposing treatment pass away to
the washing or scrubbing and condensing arrangements, whence all that has been
sufficiently decomposed to remain in a gaseous form passes away for use, while the
partially decomposed and condensible products are absorbed by the fresh oil in the
washer or scrubber and carried back with it to the retorts, there to undergo
further decomposition into conditions similar to those just described. This process
of fractional decomposition and condensation is continued until the oil is entirely
decomposed into products capable of being retained in a gaseous form and into
deposited carbon. The carbon is found mostly on the trays or shelves in the retorts
and can be removed when it accumulates to such an extent as to interfere with the
perfect working of the arrangement.
Should the oil employed be one that leaves a large deposit of carbon which is
troublesome to remove from the trays or shelves of the retorts, the process is
somewhat modified. Instead of the oil being run into the retorts at such a rate as
to allow of its being entirely volatilised on reaching the bottom trays or shelves, it
is run in considerably faster, so that, while the greater part of it is volatilised, a
residue remains, and this less volatile residue, which contains most of the
carbonaceous matter, is withdrawn from the bottom of the retort by means of a
suitable pipe into a still where the volatilisation and decomposition are continued
till only the fixed carbonaceous matter is left in a hard and dry state. Or the
volatilisation of the residue in the still may be continued only until the residue
reaches a certain consistency, when it can be run off into suitable beds there to
cool and form a pitch. The stills are thus left comparatively clean and the
difficulty in removing the solid carbonaceous matter from the still is thereby
avoided. The pitch may be conveniently converted into gas by being mixed
either when hot or after it is cold with the coal used to produce poor gas.
When horizontally-placed retorts are employed to carry out the process, they are
either made of considerable length or two or more retorts are connected so as to be
equivalent to one long retort. If one long retort be employed it is preferably
heated to the highest temperature at the end further from that where the oil is
introduced; otherwise if there be two or more connected retorts they are heated
to different temperatures, the one into which the oil is run being heated to the
lowest temperature. The retorts also are placed at a slight inclination in order
that the oil may flow from the less heated to the hotter end. The retorts may be
of any convenient form of cross section, preference being given to those of
cylindrical or those of rounded D shape with the flat part of the D as the sole of
the retort. They should be of large sectional area, and the heat externally applied
to them should be higher in temperature over the upper parts and lower at the parts
where the oil is volatilised; the object being to cause the heat to act as far as
possible as radiant heat and, where the oil is volatilised by contact with the
heated surface, to have the heated surface not much higher than the boiling point
of the oil.

page_text: In all other respects the horizontal retorts are worked in the same way as the
vertical retorts.
1000
WM. YOUNG.
ALEXANDER BELL.
COMPLETE SPECIFICATION.
Improvements in the Decomposition of Mineral Oils for the
Production of Illuminating Gas.
We, WILLIAM YOUNG Consulting Chemist. Priorsford, Peebles and ALEXANDER
BELL, Gas Works Manager, Peebles in the County of Peebles, do hereby declare
the nature of this invention and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :-
Our invention has for its object to increase the amount of light obtained from a
given quantity of mineral oil when such oil is decomposed by heat in order to
produce illuminating gas and it consists of an improved method of decomposing
the oil.
Hitherto when mineral oils have been decomposed for the production of
illuminating gas, either alone or in conjunction with some material producing a
gas of lower illuminating power such as coal or where the oils have been diffused
in the form of vapour through water gas the retorts have been heated to such
a temperature that the oil is decomposed at one single operation in a limited
period of time, the object being to have the temperature so high as to produce
the smallest quantity of liquid or condensible products and yet sufficiently low not
to produce an excessive deposit of sooty carbon.
Heretofore considerable difficulty has been experienced in maintaining the proper
temperature and the sooty carbon deposit has proved a great source of incon-
venience, whilst the excess of liquid or condensible products has constituted a
serious loss.
We have discovered that these difficulties can be avoided and that a much
larger illuminating value can be obtained from a given quantity of oil, by subjecting
it either alone or in the presence of a poor gas such as that obtained from coal
or by the decomposition of water to the repeated and fractional decomposing action
of heat of a temperature lower than that which is at present employed in
decomposing the oil at one operation, and in such a manner that the heat shall as
far as possible act as radiant heat, contact being avoided as much as can be
between the oil and oil vapours and the heated surface of the retort by having the
area of the retort large in proportion to its surface.
The fractional decomposition of the oil is effected by causing the oil to pass
alternately through the decomposing retort and the condenser and washer or
scrubber. The oil to be decomposed is employed as the agent to wash or absorb
(out of the products coming from the retort) all that are not sufficiently gasified
and convey them back into the retort to undergo further decomposition, the alternate
operations of decomposition, condensation and oil washing being continued till the
oil is split up into gaseous compounds and solid carbon.
Our invention may be put into practice with various forms or constructions of
apparatus and on the accompanying drawings we have shewn several suitable.
constructions.
Figures 1 and 2 are respectively a vertical section and plan of an arrangement
suitable for the purpose of carrying out of our process and in which the decomposing
vessels or retorts are placed vertically and provided with shelves, Figure 3 being
a modification.
Figures 4 and 5 are respectively a vertical section and plan also partly in section
of a further arrangement wherein slightly inclined retorts are employed.

page_text: In the modification shewn at Figs. 1 and 2 of the drawings the retorts A are of
round ended oblong cross section made of cast iron or steel and are placed vertically
and provided with shelves B and openings C having the usual retort lids to enable
the carbon or coke resulting from the decomposition of the oil to be removed from
the shelves and bottom of the retorts.
These retorts are shewn as being heated by means of a special furnace with
fire bars D but where water gas is being produced to be enriched by oil gas, the
producer gas resulting from the blowing of the generator may be conveniently
employed to heat the retorts to the necessary temperature, or where the process
of producing ordinary coal gas is carried on in conjunction with the manufacture
of oil gas, the heating of the oil gas retorts may be effected by the waste heat
from the coal gas retorts.
The retorts are preferably heated highest at the lower part which can be
conveniently done by carrying the fire gases along and around the bottom part A¹
first and subsequently up and around the upper part A³.
The stand pipes E convey the products resulting from the decomposition of the
oil in the retorts to the hydraulic main F which is kept cool by immersion in water
contained in the tank G.
The main pipe H conveys the products (volatile and gaseous) from the hydraulic
main to the combined condenser and washer I. This part of the apparatus consists
of a rectangular vessel containing a series of shelves provided with short tubular
nozzles covered by light sheet iron covers to cause the products passing through it
to bubble through and come into intimate contact with the fluid contained in the
shelves part of a shelf is shewn at J.
In order to cool the products there are inserted between the shelves the tubes K
passing from side to side of the vessel so that air can pass freely through them.
The permanently gaseous products pass away by the main pipe L.
On the top of the condenser and washer is placed the tank M to contain the oil
to be decomposed. This tank should be provided with a float to indicate its
contents.
The oil to be decomposed is allowed to flow out of the tank into the arrangement
by means of the regulating valve N into the filler attached to the tube O. This
tube is connected by branch pipes provided with stop cocks P to each of the shelves
in the condenser and scrubber and also to the pipe leading from the hydraulic
main, so that the oil can be made to flow down all or any number of the shelves
forming the washing arrangement or the oil may be allowed to flow direct into the
hydraulic main without passing through the washer, according to the amount of
washing to which it is desired to subject the gaseous products from the oil.
The oil entering the hydraulic main Fat the end from which the decomposed
products from the retorts leave, flows through its whole length and is withdrawn at
the opposite end by the pipe Q into the cistern R provided with a float and
indicator to shew its contents. The oil flows from the cistern by the main pipe S
provided with the regulating valves T to regulate the flow of oil through the syphon
pipes U into and down the stand pipes E on to the upper shelves of the retorts B.
To carry out the process the apparatus is operated in the following manner: -
The tank M having received a charge of oil and the retorts being heated to the
desired temperature, the regulating valve N is at first fully opened and the oil
flows through the tube O on to the lower shelf of the condenser and washer until
the bottom part of the condenser and the hydraulic main F is filled up and the oil
has overflowed by the pipe Q and partially filled the compensating cistern R. The
regulating valve N is then checked to pass about the quantity it is anticipated the
retorts will decompose. "We have found 1050° to 1150° F. to be a suitable external
temperature to begin with," different oils however, require different temperatures
and the effect of externally applied temperatures can be considerably modified by
the rate at which the oil is run into the retort, a large flow of oil lowering the
internal temperature of the retort or keeping the internal temperature at that

page_text: suitable for the purpose, although the external temperature is raised. An increased
external temperature, with proportionally increased flow of oil into the retort, leads
to a larger product of gases per retort.
The oil is now allowed to flow from the cistern R through the pipe S and
regulating valves T and the syphon pipes U into and down the stand pipes E on to
the upper or first shelf in the retorts. The rate at which the oil is allowed to flow
into the retort must be largely in excess of that which the heat of the retort will
decompose into permanently gaseous compounds.
At least one half of the total oil must leave the retort in a condensible form and
with most oils, especially oils of high gravity the best results will be obtained when
only from one fourth to a sixth of the oil passing into the retort is decomposed into
permanently gaseous compounds, the three fourths to five sixths leaving the retorts
as vapour only partially decomposed, or being left in the retort as solid carbon.
The proper quantity of oil to be run into the retort in relation to the externally
applied temperature is readily ascertained by the appearance of the partially
decomposed products, when a portion is allowed to escape by the small stop cock z
fixed in the retort door. The products should have the appearance of oil vapour,
being whiteish or pale, or at most dark yellow. When the supply of oil is too
small in relation to the temperature of the heat applied to the retort the vapour
becomes more or less dark brown in colour. Such a condition is detrimental to the
success of the process.
This large flow of oil falling upon the first inclined shelf B runs down it and
thence from shelf to shelf to the bottom of the retort, being exposed in its
descending course to the heat radiated from the walls of the retort and as mineral
oils consist of a series of hydrocarbons of different boiling points which the
fractional process of decomposing accentuates, on the resulting product getting
into circulation these different grades are volatilized as they in their descent over
the shelves in the retort reach their boiling points at distances from the outlet of
the retort which increases as the boiling points rise:-thus the vapours into
which the oils are successively converted, and each of which is in its turn less easy
to decompose, are subjected to corresponding higher temperatures and longer
periods of time. The products resulting from this fractional decomposing treatment
of the oil pass up the stand pipe E where they are met and partially washed of
the grossest matter by oil admitted by the pipe U and flowing down the standpipe
to the retort.
The condensation and absorption of most of the oil vapours which have only
been partially decomposed on their first exposure to the heat of the retort, takes
place whilst bubbling through the oil in the hydraulic main. The great heat
resulting from this condensation is rapidly transmitted through the walls of the
hydraulic main to the surrounding water contained in the cistern.
The more volatile products together with the gaseous portion pass by the pipe H
from the hydraulic main to the condenser and washer I where the cooling and
washing of the gaseous portion is completed.
For a time the oil flowing over the lower shelf of the washer is capable of
absorbing the vapours out of the gases, but as the process continues and the
apparatus and the oils get heated, the oil has to be admitted into the condenser
and washer on the higher shelves, so that it may flow down from shelf to shelf and
present a greater surface to more perfectly fractionate out of the truly gaseous
portion that which otherwise condense.
The number of shelves over which it is necessary to pass the oil so as to
sufficiently absorb and fractionate out of the gaseous portion the volatile hydro-
carbons which would otherwise condense is dependent upon the nature of the oil
employed. Oils containing volatile matter have less solvent power than heavy
dead oils, the solvent power of the oils diminish as the temperature rises, and the
number of shelves through which the oil is run must be regulated accordingly.
The purpose to which the oil gas is to be applied has also to be taken into
consideration in connection with the washing with oil.

page_text: When the oil gas is to be used to carburette and give illuminating power to
water gas or to increase the illuminating power of coal gas, hydrocarbon which
would condense out of the oil gas if kept separate would be rendered perfectly
permanent when diffused through those gases and therefore for such a purpose less
oil washing is required. Indeed sufficient washing or scrubbing may for such
purposes be obtained by the portion of the oil which escapes decomposition in the
retort but which in a volatilized state passes off with the gases falling or dropping
back through the gases rising from the retort and in that case it is not necessary
to pass the crude mineral oil through the washer at all it being supplied direct to
the retorts by a separate supply pipe connected to the supply cistern.
On the other hand when the oil gas is to be used for lighting railway carriages
and requires to be stored under considerable pressure, then the washing of the
oil gases requires to be more drastic so as to render the oil gas as free as
possible from hydrocarbon which would condense during compression.
The proper amount of oil washing is readily ascertained by the illuminating
power and character of the gas and the proper quantity of oil flowing into the
arrangement from the supply tank M through the regulating valve N is indicated
by the float in the compensating cistern R. If the supply is in excess of that
which is being decomposed in the retorts the indicating float rises, and it falls
when the supply is deficient.
The oil after having undergone one decomposition in the retort has had a portion
rendered permanently gaseous. This passes away by the pipe L to the purifiers.
The remaining partially decomposed portion of the oil, condensed or absorbed
by the fresh oil, flows back through the arrangement to the compensating
cistern R and the commingled oil and partially decomposed products are again
submitted to decomposition in the retort and the resulting products again con-
densed and washed as already described. The process of alternate decomposition
and condensation and washing is thus continued with the result that the stream
of oil flowing into the apparatus is completely split up into permanently gaseous
compounds, which leave the arrangement by the pipe L, and carbon which is left
upon the shelves and bottom of the retort as hard coke. This coke is periodically
removed when it accumulates so as to begin to interfere with the process.
Figure 3 shews a modified form of retort by which instead of reducing the
residue of the oil to coke in the bottom of the retort it may be decomposed
only to such an extent as to allow of its being drawn off by the stop-cock W
in a state which on cooling becomes pitch.
In working by this modified form the flow of oil into the retort must be
increased or the temperature of the retort kept a little lower than when coke is
produced.
Figure 3 also shews how a poor gas such as that obtained from the decomposition
of water may be employed, the poor gas being supplied from the gas main X
and branch pipe Y into the bottom of the retort. By this arrangement the oils
are decomposed in the presence of the poor gas. We believe however, that
better results are obtained by decomposing the oils and producing the water or
other poor gas separately and commingling them after they are comparatively
cold as a much better fractionation of the products from the oil can be made
than when the water gas is present.
The water gas is also much more easily treated during the process of cooling
enabling water to be more freely employed as the cooling agent.
The arrangement of apparatus shewn by Figs. 4 and 5 are substantially identical
in every respect with the arrangement shewn in Figs. 1 and 2 and is in any respect
operated in the same manner, the only essential difference being in the form of the
retorts which are placed at a slight inclination from the horizontal and contain no
shelves.
The
The decomposition of the oil is however effected in a similar manner.
oil flows from the stand pipe on to the bottom of the inclined retort, and down
to the opposite end, volatilizing as the temperature rises in the graded manner

page_text: corresponding to that described where the oils flow over the shelves in the
vertical retort.
In decomposing the oils in slightly inclined retorts we do not find it of
importance to differentiate the heat applied externally to the retort between
the higher and lower end as the oil entering the higher end rapidly reduces the
temperature there to that suitable for the process.
Our process may in part be carried into effect in many of the existing forms of
apparatus both in which oil gas is produced alone and also in those in which oil
gas is produced by decomposing oil in the presence of poor gas from coal or in the
presence of water gas in retorts or in decomposing vessels heated internally.
In producing gas from oil by such existing arrangements, in accordance with our
invention, the temperature at which the oil is decomposed is reduced by adjusting
the inflow of oil to the temperature of the decomposing vessel (the higher the
temperature of the decomposing vessel the larger must be the flow of oil) so that
only a fractional part of the oil is decomposed each time it passes into the retort or
decomposing vessel, and the oil and condensed undecomposed products are employed
to wash the gas and carry back into the decomposing vessel the undecomposed
portion of the oily products for further decomposition.
When our invention is practised in conjunction with the manufacture of water
gas and when the mineral oils to be decomposed are very crude and tarry,
containing a large excess of carbon in their composition, the water gas plant should
in order to carry out the process, be so constructed that the oil and returned
undecomposed products shall flow, or be pumped back, into the water gas producer,
so that the excess of carbon may be there deposited as solid carbon to be utilized
in the reheating of the upper internal walls of the decomposing chamber, or in the
production of water gas.
In decomposing such tarry mineral oils in externally heated retorts we have
found that ordinary fire brick retorts may be employed and that the process may
be conducted in conjunction with the production of gas from coal.
Having thus particularly described our said invention and arrangement of
apparatus whereby the same may be carried into practical effect we wish to state
that we do not restrict ourselves to the precise details therein described and
delineated as the like results may be obtained by many other modified arrange-
ments, we also wish to state that we are aware that in the manufacture of oil gas
the tar and oil which has unavoidably escaped decomposition, when the oil has
been distilled at a comparatively high temperature has been returned with the fresh
oil into the retort to there undergo further decomposition, we are also aware that
it has been proposed to wash oil gas with oil, and that oil has been extensively
used to wash the hydrocarbons out of gas produced in shale oil works, and benzole
out of gases produced from coal, and therefore we desire to restrict our claims
accordingly.
1. The improved method of decomposing mineral oils for the production of
illuminating gas consisting in repeatedly subjecting them to the action of heat
preferably radiant heat of a temperature so low that only a part of the oils will be
decomposed each time they are passed into the retort or decomposing vessel the
rate of flow into the retort or decomposing vessel being so regulated in accordance
with the externally applied temperature as to restrict the internal temperatures to
those suited for the partial gasification of the particular oil being decomposed.
2. The improved method of fractionally effecting the decomposition of mineral
oils for the production of illuminating gas by causing the oil to flow into and
through the retort or decomposing vessel in an opposite direction to the outflow of
the products of decomposition, so that the oil is subjected to higher temperatures
and for longer times as the boiling point rises.
3. The improved method of washing the products resulting from the decom-
position of mineral oils in the production of gas, by the oil to be subsequently
decomposed, and whereby the imperfectly decomposed portion is continually washed

page_text: back through the condensing arrangement and hydraulic main, and down the stand
pipe into the retort till the oil is completely split up into gas of the desired
permanency and hard solid carbon or pitch.
Dated this Thirtieth day of March 1893.
CRUIKSHANK & FAIRWEATHER,
62, St. Vincent Street, Glasgow, Agents.