Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates to a method of storing a fuel
gas for blowpipes and bu~ners, more partlcularly but not
exclusively for use in welding, cutting, bronze welding
and brazing.
It has been customary for more than half a century to
use acetylene in this technical field. However, the nature
of acetylene is such that it is very dangerous to keep
compressed in the natural state and currently it is stored
after having been compressed and dissolved in a solvent
such as acetone, in a porous material. The porous substances
filling bottles of ac~tylene have the purpose of-stabili2ing
the solution of acetylene contained in these vessels. This
stabilisation is obtained principally with regard to the
liquid phase.
A fuel gas for welding and cutting whiçh has recently
been proposed is obtained by dissolving under high pressure
a mixture of three gaseous constituents consisting of 60 to
85% acetylene, S to 30% ethylene and 5 to 20% propylene in
acetone impregnated in a porous material.
Likewise a fuel gas has been described wh~ch is obtained
by dissolving a mixture consisting of 60 to 80% acetylene and
40 to 20% ethylene in acetone impregnated in a porous material
under high pressure. A further mixture has also been advocated
which is obtained by dissolving 65 to 90% acetylene and 35 to
10% propylene under high pressure in a solvent such as acetone,
,
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toluene, xylene and mixtures of any two or all -three of those
liquids, impreynated in a porous material.
~ lowever, all these methods have the disaclvan-tage that
the fuel yas is stored anclrnust be drawn off in -the presence
of solvent.
In con-trast the use of a mixture of acetylene and ethylene
has been considered, avoiding the risks of explosion and allow-
ing a cornbustion tempera-ture to be obtained which is sufficiently
high to effect welding and oxycut-ting operations. rrhese com-
bustible liquid compositlons containing acetylene in the ratioof 40 to 90 mol % are kept or transported at a temperature of
-40C.
This method o-f storage and transport, solely in the
cryogenic state, involves heavy capital and operational costs,
due to the low temperatures used, and limits the duration of
preservatlon.
SUMMARY OF THE INVENTION
A method has now been found for storing an acetylene-
ethylene mixture which alleviates the various disadvantages
hitherto associated with filling, storing, distribution and
use. According to the present invention, there is provided
a method of storing a combustible mixture for blowpipes and
burners, more particularly applicable to weldiny, cutting,
bronze welding, and brazing, comprising the steps of preparing
a cornbustible mixture consisting of 15 to 25 mol % acetylene
and 85 to 75 mol % ethylene, and storing said mix-ture in a
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porous substance in compressed form, in the absence of solvent,
by introducing the mixture into a pressure-resistant metal
vessel filled with said porous mass, and maintaining the
mixture in the vessel at a pressure of 15 to 110 bars and
a temperature of from -30 to -~35C.
The method of the invention is an economical, simple and
fas-t process. This method is effected by simple compression
without ex-ternal addition of re-frigerants. It is an easy
technique for it does not have recourse to the phenomenon of
dissolving in a stabilising solvent and consequen-tly the
filling time is reduced and the operations of weighting the
bottles, checking the quantity of gas remaining in the bo-ttles
and of monitoring the quantity of solvent are obviated, only a
standard measure of the pressure is necessary when the tempera-
ture is known.
The method of storage of this invention allows usage
without special precautions in all climates, in both cold
and hot countries. The operations of welding and cutting can
be realized with high, and even very high, ra-tes of flow without
restriction as there is no risk of entraining stabilisation
solvent.
The mixture conditioned in accordance with the invention
is stable under pressure and allows operations to be conducted
under pressure without any decomposition, for example at the
time of distribution under pressure into piping or of feeding
certain special blowpipes under pressure.
The special conditions of storage of the combustible mixture
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and the choice of the proportions of its constituents allows,
at any moment during tapping, a combustible gas of practically
uniform composition to be drawn off, whatever the temperature~
This is ~ue to the particularly ~udicious and critical choice
of the composition of tlle mixture, associated with the
conditions of storage and those non-apparent conditions of the
stabilizing agent.
DESCRIPTION OF TIIE PREFERRED EMBODIMENTS
When the storage temperature is lower than about ~10C
the mixture is partly liquefled and the proportion of the liquid
fraction in relation to the gaseous fraction is a function of
the storage temperature~
Mixtures formed of about 20 mol % acetylene and about
80 mol % ethylene are particularly advantageous.
It has been discovered in completely unexpected manner
that the storage of the combustible acetylene-ethylene
mixture in the chosen proportions, under conditions of pressure
and temperature withln the limits close to the pseudo-critical
point (about 54 bar and about 14C) and of azeotropy in a
porous substance in the absence of any solvent, perfectly
meets all the requirements of stability and safety~
- The combustible mixture may be stored in a metallic
vessel or bottle of pressure-res~stant sheet steel, filled
with a porous material of a type currently used, such as
silicocalcareous monolithic substances, pulverulent substances
.
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includlng charcoal powder ancl infusorial earth and other
-ingredients, porous substances based on zinc oxychlor~de cement
enclosing porous charcoal and substances based on alumlnium
slag. The capacity of the bottle is not limited by the method
of the invention; lt may be for example between 1 litre and
160 litres.
The composition of the combustible mixture gives every
guarantee of safety. Acetylene explodes under an absolute
pressure of 1.4 ~ar, but when it is associated with ethylene
in the chosen proportlons the upper pressure limit for
explosion is much higher. For example a gaseous mixture of
25 mol % acetylene and 75 mol % ethylene has a maximum
pressure before explosion of 15 bar ancl a gaseous mixture
-of 20 mol % acetylen~ and 80 rnol % ethylene has an upper
pressure limit of 30 barO
The combustible mixture is particularly suitable for use
in welding, bronze welding and brazing. Comparative tests,
made by way of non-limiting examples, between acetylene alone
and a mixture of approx. 20 mol % acetylene and 80 mol %
ethylene, show that the welds produced are of equivalent quality
in both cases. The same metallurgical results are obtained
as with acetylene, with easy flame control and a practical
consumption ratio : heating oxygen consumption over fuel -
consumption, in volume, is in the range of 1.7 to 1.8. These
estlmates are equally valid f~r bronze welding and braæingO
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Comparative tests in oxycutting, made by way of non--limiting
--- example, between acetylene alone and the same combustible
mixture as before of 20 mol % acetylene and 80 mol % ethylene
show the high suitability of the mixture in this technical
field. The tests werc begun with a cutting oxygen pressure
of 3 bar with a normal distance between the cutting head and
the sheet metal of 10 millimetre thickness. Tests 1 and 3
correspond to acetylene alone while tests 2 and 4 to acetylene
20/ethylene 80 mol ~. In each test the pressures of the fuel
and of the heating oxygen P as measured were expressed in bars,
as also the flow rates of the fuel and the heating oxygen Q
expressed in litres per hour; "a" indicates the ratio o~ ¦
-consumption in volume (heating oxygen consumption/fuel
consumption). The cuttlng speeds are expressed in metres/hour
over 10 to 15 minutes and the starting time in secondsc
.
TABLE 1
: ~est : Fuel : 2 heatin9 : - : Speed : Starting :` !
Cut Time
:. . .
: 1 ~ P = 0.5 bar: P = 1.5 bar: a : 47m~h : : -
~.2 to ~Os
: :- Q = 300 l~h: Q = 350 1/h: : 90m/h : :
-
- ..
Table continued overleaf ~9
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2 : P = 005 bar: P = 1~5 bar: : 47m/h
` 1.8 to 20s
: : Q = 22g 1/h: Q = 425 1/h: : 90m/h
.... ~ . . . . .
: 3 : P = 0.3 bar: P = 1.5 bar: : ~6m/h ~ :
1.1 ClOs
: : 4 - ~20 l~h: Q - 480 l~h:
:
: 4 : P = 0.3 bar: P = 1.5 bar: : 46m/h
1.8 ~lOs
o : Q = 3~0 1/h: Q = 600 1/h: : : :
,
It was established that the starting times are correct and
the oxycutting speeds identical~ with good cutting surfaces being
obtained, when the acetylene/ethylene mixture is used; only the
ratio of consumption of the mixture is slightly higher than that
of acetylene alone.
~ urther comparative tests were carried out to provide
information on the characterlstics of blowpipe flames with
acetylene on the one hand and a mixture of 21 ~ol % acetylene
and 79 mol % ethylene on the other hand.
The-flame temperatures ~ in C are calculated; the ratio of
consumption is indicated by "a" as previously; and the strength
R of the fuels used in Table 2 below is as given by the Journal
~'Souder" no. 118, September 1973, page 24. The blowout flow
rates "S" in litres/hour have been measured and this term
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indicates the weakest of the flow rates at which the flame
is maintained on the stationary blowplpe but is extingusihed
if the blowpipe moves. The ~lowout speeds "V" ln metres/second
are calculated according to the dimensions of the nozzles
and the rates of flow takin~ lnto consideration the fact
that the flows are laminar. The heat ~ransfers T in kilo-
calories per hour are measured 2 millimetres downstream of the
cone and for a total ~aseous rate of flow equal to 9/10 of
the blowout flow rate, flow rate measured almost 2 % in
relative value. This measure is made on an interior surface
at 1,100 C by means of a thermal fluxmeter. The dimenslons
of the nozzles of the blowpipes are given ln millimetres.
TABLE 2
.... ... , . . _ _ ~ _ _ _ , , ................ _ _ ,
: Fuel : R : a : : Nozzle : S : V : T
9C mm l/h mJs m ThJh
' : :
~ . . . . . . . .
0O6 : 196 ~i 192.5 : 120
: Acetylene : 2.27 : 1.1: 3109 : 0.82 : 372 ~ 195 : 149 :
~ 1.04 : 473 : 15~ : 14~ :
O
: : : : : 0.6 ~ 116 : 113 : 103 : `
: Mixture : 1.33 :2.18: 2962 : 0.82 : 110 : 57 : 57 :
.
Table contlnued overleaf.
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: I
54L~
: 1.0~ : 27t3 : 90 : 136
. : : : : : 1.18 : 493 : 125 : 167 :
: : : : 1. ~ : 820 : 147 : 191
~ 1.6 : 1155 : 159 : 191
:
: Mixture : 1.65 : 1.75: 2 929 : 0.6 : 118 : 115 : 85
0.82 : 80 : ~2 : 27
: : : : : 1.0~ : 28~ : 92 : 119
: : : : : 1.18 : ~0 : 122 : 152
: : : : : 1.4 : 813 : 1~6 : 163
~ : 1.6 : 118~ : 163 : 163
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