Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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It is ~nown tha-t by distillation crude petroleum
can be fractionated into a certain number of varied products
which are distinguished fro,-n one another especially by their
~olatility.
In the feeding o~ internal combustion engines the
fraction has been employed which i5 called in ~rance "essence"
and in the United ~tates "gasoline"~ in England "petrol",
whioh thanks to its volatility enables carburetting of the
air to be effected before its introductien into the engine
cylinderS.
~ hen the Diesel cycle has enabled heavier frac-
tions to be employed, such as gas-oil which is injected sepa-
rately into the engine cylinders at the end of the phase of
compression of the air and which ignites spontaneously tl~anks
to the heat of compression.
; Hitherto ~ne has lived with this binary system of
fuels and the corresponding two classes of engines.
~ or engines having carburettors where the air
charged with fuel is compressed in the cylinders before igni-
tion it is advisable for the fuel to have an-ti-detonating
properties which have come to be characterized by the octane
number.
~ he natural distillate from petroleum generally
has a poor octane number which allows of only an equally poor
degree of compression. In order to improve the performance
of carburettor engines one is compelled to inorease this
octane number by various artifices. One of them is the addition
to the petrol of products such as tetra-ethyl lead which
unfortunately is very poisonous and hence presents a serious
disadvan-tage in relation to pollution. In addition i-t contri-
butes to the fouling of engines by deposits of lead and to
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corrosion of the valvesc
~nother arti~ice curren~tly applied in petroleum
refineries consists in tal~ing fractions of~ tlle distillate
wllich are heavier and ligh-ter -than petrol and in converting
them by cracking or reforming operations in order to obtain
hydrocarbons of aromatic or naphtene type having antidetonating
properties~ which are mixed wi-th the petrol fraction in order
to increase its octane number.
~ut this procedure, apart from -the fact that i-t
necessitates complicated and costly apparatusg in-troduces
losses resulting from -the fuel tha-t is burn-t for heating the
apparatus and gives as residue gases which are generally burnt
in a flare. r~hese losses may be evaluated at about 5~0 of the
crude petroleum.
It is obvious that in the present economic situation
these losses constitute a serious disadvan-tage.
On -the other hand Diesel engines have made consi-
derable technical progress and today for the propulsion of
motor vehicles even in -towns high-speed Diesel engines can
be produced, having low weight, a certain flexibili-ty in
running and being no-t very noisy.
~ he ~pplican~ has had the idea of replacing the
two types of fuel by a single fue] called "long~cut" incor-
porating light and hea,vy fra,ctions from crude petroleum,
which is well suited to operation of modern Diesels a,nd par-
-ticularly ante-chamber Diesels so that this new fuel for
piston engines should progressively replace the -two present
fuels at the same time tha-t the Diesel engine would replace
-the previous carburettor engine by making the disaavanta~es
3 called to mind above disappear7 since in particular for the
Diesel engine there is no need of a high octane number.
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As -the Diesel engine has generally specific
consumptions lo~er than -the petrol en~i~e one would acld -t~io
sources of economyo one during the course o~ refining and the
other in the operation of t~e engine. As the Diesel engine
also enables easier fitting of an exhaust twrbo-compressor,
progress along the pa-th of economy n~,ight bc made general thanks
to a more universal fuel than gas-oil.
Since tllis new fuel will take part of the market
for petrol in addition to tha-t for gas-oil it mus-t be widely
available ~rom crude petroleum.
It will consist in its wiclest definition of the
whole of the distillation fractions comprising gas-oil for
high speed engines and lighter fractions the designa-tion of
which varies bu-t in a conventional way comprises the kerosenes
and the distillates sometimes called heavy and light naphtas,
Hence it will comprise conventional gas-oil and -the sections
available by distillation which dis-till at temperatures lower
than those o~ the gas-oil cut.
~he new long-cut fuel which will be designated
below by ~C for convenience of speech and which forms the
object of the inventlonS is characterized mainly by the fol-
lowing points D
a) in the standardized clistillation test, distilla-tion
commences at about 30C -to terminate in the same range
o~ temperature as that of conventional gas-oils for high~
speed engines 9
b) in -this same standardized distillation test about 90
of the volume passes in-to -the receiving vessel at a
temperature lying be-t~een about 210 to 250C and 360C~
Such a, ~uel which represents about 50 to 60~o
by volume of the crude petroleum ins-tead of 10 to 20~, as
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is the case for light gas-oil for motor vehicles, presents
no-t only the advan-tages ~Jhich have been indicated but again,
thanks to the presence of products heavier -t~an petrol, has
a lubricating power sufficicnt for th.e proper operation of
pumps 5 injectors and accesrsories~ whils-t containing vola-tile
proclucts which facilita.te cold starting of Diesel engines.
It goes without saying that -this fuel is more
available in crude petroleum than the present petrol for
motor vehicles since the la-tter above all becau.se of the
demand for an octane index9 re~luires special operations in
prepara-tion and is not generally available by simple clis-
tillation from the crucle excep-t in some special cases.
It is in adclition important to avoid -the possibi-
lity of the fuel falling within the zone of ground-level
explosivity which is characterized by the presence of suffi-
; cient volatile hydrocarbons to result in an ambient saturated
atmosphere which lies above the liquid fuel in a tank entering
the zone of inflammability~ at least at ordinary temperature
in normal geographical loca-tions~
~hus i-t is known that if on~ considers a -tank
containing liquid pe-trol, even only in small amount 9 its
atmosphere is generally too rich in vapour to ignite~ ~t
least in temperate climates, that is to say9 those where
' the win-ter temperat~re is 'nigher than -20 a .
- 25 On -the other hand for kerosene and a fortiori
gas-oil, the saturated atmosphere is too poor to ignite.
~ut if one is dealing with mixtures of lamp oil ?.
and petrol the saturated atmosphere in tanks may arrive at
conditions for ignition, hence for deflagration ~nd for '
~0 explosion.
In order not to complicate excessively -the com-
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mercial distribution o~ -the fuel in accordance with the in-
vention it is advisable to make it comparable with petrol in
its effect on ambient atmosphere~ consiaered.
To this end the fuel should contain a minimum
of light hy~lrocarbons, this minimum bein~ c~laracterized by a
minimum of Reid vapour ?res,ure or a minimurn of the ~ercentage
distilling at low temperatures in the standardized distillation
test.
This proportion of light hydrocarbons corresponds
with a ~eid vapour tension higher than 50 piezes or 500 g/cm2
or possibly only higher than 35 to 40 piezes depending upon
the local conditions of use.
A8 far as t!le minimum percentage dis-tilling at low
temperatures is concerned the composition may be adapted so
that 10~ of the volume dlstils below 70 or 75C, this limit
depending upon the minimum atnlospheric -temperature in the
geographical terri-tor~ of use.
~ rom another poi~t of view it is known that in
order to avoid vapour locks in the :Eeed circuit to an engine
and depriming of the feed pump9 it is advantageous for the
`'t~eid vapour tension not -to exceed a certain value, for example 9
i in ~rance ancl o-ther temperate countries, 65 piezes in summer
! and 80 piezes in winter.
~he attached drawing shows by way of example the
standardized distillation curve of a long-cu-t fuel in accor-
dance with the inven-tion. Temperatures in degrees centigrade
are plo-tted as ordina-tes and the percentages of product
passing into the eprouvet-te a~re plotted as abscissae.
'~he point A represents the upper limit of tempera-
tures corresponding with the condi-tion b above 9 whilst the
points B and Bl corre~pond with the range of lower limit.
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~hc ~oin-t C corresponds wi.-th -the preserce of a minimum of
volatile hyclrocarbons according to what has been said above.
Such a curve enables one sk-llled in -the art, -that
is to say 9 specialists in the refining of petroleum, -to
produce a fuel in accordance with the invention, starting
with a crude of any origin.
'~hus it i9 possible to start9 in conventional
manner~ by fr~ctiona-ting the crude, I or example 9 in a plate
distillation colu~-n, then to recombine suitable proportions
of the frac-tions thus separated in order to con.stitute the
fuel in accordance with -the invention. The specialist in
distillation will have no difiiculty in determining the sui-
table proportions of -the various fractions. If the occasion
arises, the gaseous hydrocarbons such as butane or -the
pentanes may be dissolved in -the mixture.
The production yield by direc-t distil'La-tion of
the new fuel results from -the f`ollowing tables in which the
percen-tages of gas-oil and of -the new ~C fuel have been given,
which may be obtained Wi-t}l crudes of different origins~ Petrol
~or motor vehicles are not set forth because it re~uires
reprocessing of certain fractions and its availability depends
both on the nature of the crude and the refining e~uipment
available.
Amongst the problems posed by the refining of
available crude petroleums, it may be :necessary to thermally
break down (for example, by catalytic cracking) fractions of
pe-troleums stocks heavier than gas-oils in order to avoid
having too much of the heavy f'ractions~ In fact the market
for these fractions might tend to diminish because of -the part
, 30 -taken by the increasing emplo~men-t of atomic or e~en coal
power s-tations and the use of -their residual hea-t. In these
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circumstances the refiners woul~ be led to employ catalytic
crackers for heavy products which can be adap~ted for -the
production either of petrol of high octane number or of
products in the ran~e known as gas-oils. Acloptio^n o~ the ~C
fuel will make these adaptations more flexible ~y enabling
the use of prcducts of any ~ature. ~he use ar.cl the opera-tion
of catalytic craci~ers~ hydrogenating or not, may be simplified
by it and corresponding investments reduced.
Crude Arabian Heav~l~rabian Medium ~rabian ~i~ht
% gas-oil 16% 18 20
~a 430~0 50 60
~ an ~assan
% gas-oil 14 20
% ~C 55 55
Al~eria ~'lessaoud
o,b gas-oil 2
'~ ~C 7~
Kuwait
% gas-oil 14
20 r~o LC 42
Irak Qatar Zakum
~O gas-oil 10 18 20 19
/o ~C 50 50 '70 63
It is known tha-t the combustion of gas-oils in
Diesel engines leads to -the use of minimum cetane index in
order to avoid knocking in these engines. r~'his resul-ts from
a property which is the reverse of lack of explosiveness o~
petrols for controlled igni-tion engines. 'i~here will be no
reason to change it in the developmen-t of -the use of ~C.
It is possible in order -to expedite ref'ining,
to specify a maximum con-tent of aromatic carbons 9 for example,
20 or 25,~" in order -to obtain a product giving less knocking
and a minimum of smoke in the exhaust.
~ 'he maximurl ternperature point A (350) ~or the
90% point on -the distill~tion curve corresponds likewise
ensures that the hyclrocarbons are not too heavy9 so as to
cavse deposits and smoke on combustion. '~'he temperature 360C
corresponds to a sligh-t increase in gravity in comparison with
conventional gas-oils. It might be raised by the use of light
fractions in the "long-cut" fuels.
The requiremen-ts regarding sulphur content ~J-ill
be preserved as for conventional gas-oils intended ~or use in
motor vehicles, ~hey will generally be more easy to meet for
refining because the na-tural sulphur content often increases
with -the density of the distilla~tion cuts. It follows that it
is possible -to minimize the maximum sulphur con-ten-t of -the
"long-cut" f'uel relative to -that of` conven-tional gas-oils.
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