FR2628728A1 - METHOD AND DEVICE FOR THE COMBINATION OF HYDROGEN WITH OXYGEN, IN PARTICULAR FOR TRITIUM ENRICHMENT - Google Patents

Abstract

Process characterized in that an overpressure is obtained in the combustion chamber 2 by introducing therein a non-combustible gas with the exception of oxygen and in that the device for its implementation comprises: a) the combustion chamber closed 2 is in communication directly or through at least one gas-tight pipe with a water collecting tank 18 disposed below; b) in the combustion chamber or else in the gas chamber of the water collecting container, opens a pipe 12 through which a non-combustible gas, with the exception of hydrogen, is supplied to the device. The invention relates to a method and a device for the combustion of hydrogen with oxygen, in particular for an enrichment in tritium.

Description

"Process and device for the combustion of hydrogen with oxygen

  especially for tritium enrichment. "

  The invention relates to a method for

  hydrogen combustion with oxygen at ratios of approximately stoichiometric volumes by a flame in a closed combustion chamber

  and cooled, and who is in communication with the envi-

  a process in which steam is produced

water and / or condensed water.

  The combustion of hydrogen with oxygen is important from two points of view: 1.- enrichment of hydrogen isotopes

  by catalytic exchange of isotopes.

  In what follows, we will describe the enrichment

  tritium according to US-PS 4,190,515.

  Water containing tritium is decomposed in a

  oxygen and hydrogen electrolysis cell.

  The hydrogen that starts is usually depleted in its tritium content. The major

  part of the tritium still contained in it, he is

  lifted on a noble metal catalyst sprayed with a water low in tritium. This water is poor in tritium

  then picks up tritium, while hydrogen is

poor in tritium.

  The hydrogen thus depleted is burned with the oxygen released during the electrolysis. The tritium-poor water thus obtained sprinkles the metal catalyst

  counter-current with respect to hydrogen,

  as already mentioned the tritium contained in this hydrogen and is brought back to the electrolysis cell

  to continue enrichment with tritium.

  2.- Accumulation of the electrical energy ex-

  sedentary by electrolysis of water.

  Electrolysis of water allows indirectly

  the accumulation of electrical energy. In this case, the

  electrical energy is converted into usable chemical energy. During the combustion of the electrolysis gases,

  for example, steam can be obtained.

  The water that is used for electrolysis must be of high chemical purity because the whole

  impurities are deposited in the electrolysis cell.

  These deposits can cause a short circuit of this

electrolysis cell.

  Obtaining high purity chemical water always leads to high operating costs,

  because, in general, at least one

  tillation and / or purification with exchangers

ion.

  Advantageously, the water is born

  during combustion in the two processes previously

  mentioned, should therefore be brought back into the electrolysis cell, so that one can

avoid water purification.

  In the case of tritium enrichment, the recycling of water is further indicated for

  reasons for protection against radiation.

  In order to recover the reaction water, the combustion chamber must be closed. In addition, the combustion must be conducted in such a way that

  no impurities in the reaction water.

  As impurities, it is necessary to take

  mainly in consideration of NOx / HN03 and the

  corrosion products resulting from the material of the

  combustion chamber (usually stainless steel)

  corn). When burning hydrogen in a

  closed combustion chamber, nitrogen oxides

  born when the air reaches this chamber.

  combustion. This formation of NOx also occurs when the hydrogen is burned with oxygen

  pure, because the pressure in the communication device

  is unstable and when it fluctuates

outside air is drawn in.

  From the equation of reaction: 2H2 + 02 2 H20 (fl) we can see that from three molecules of gas

  (67.2 l) only 0.036 l of condensed water is obtained.

  The foreign gas present in the combustion chamber after the ignition of the hydrogen must, therefore, in the ideal case, remain locked during the whole of the combustion time to maintain the

atmospheric pressure.

  However, this is not the case in practice.

than.

  Fluctuations in the flow of oxy-

  gene and the hydrogen current modify the flame and thus modify the heat released, thanks to which the

  temperature in the combustion chamber changes.

  During a temporary rise in the flow of

  oxygen and hydrogen, the combustion device

  It becomes hotter. As a result, the pressure increases. Via communication with

  the environment, which is necessary for the technical

  given, gas is expelled. When following the flows

  of oxygen and hydrogen are normalizing or

  drop for a short time below the

  predefined, the combustion device becomes colder and the pressure in the combustion chamber

decrease.

  Air is sucked from the environment

  the nitrogen fraction of this air is burned to give NOx which combines with the water formed to form

give nitric acid.

  Even for very constant gas flow rates, the water flowing from the combustion chamber has a pH between 0 and 0.5. Instead of pure water, we get

  during the combustion of hydrogen under the conditions

  mentioned above, very dilute nitric acid which,

  In addition, it acts in a very corrosive

  eratures raised in the combustion chamber and which

  is welded by corrosion products.

  The formation of NOx can be reduced when

  that, as a link to the environment, a long, thin tube is used. For security reasons, such a tube is, in any case, installed so

  it opens in a hood or in the open air.

  A tube that causes a measurable pressure drop at least prevents the suction of very large amounts of air and thus reduces the formation of NOx during combustion. However the pressure

  in the combustion chamber does not remain

  aunt. It turned out that for-depressions of

  0.1 bar and more, the flame goes out. Vraisembla-

  In the depression, a large amount of condensed water vaporizes quickly, which uses

  a lot of heat and as a result, the temperature is

  drop below the ignition temperature of the

H2 / O2 mixture.

  In a document (H.J. Sternfeld, Brebber-

  system mit reinem Wasserstoff; Beitrag zur DECHEMA-

  Wasserstoffstudie, Màrz 1986), it is proposed, to reduce the formation of NOx, to carry out the combustion at high pressures of 20 to 200 bar. In that same

  document, we note, however, that during an increase

  pressure in the combustion chamber

  tion, explosions may occur.

  As other possible measures to reduce NOx formation, it has been proposed to reduce the

  temperature of combustion or to delay

  exhaust gas recirculation. These measurements

  simply reduce the formation of NOx but do not

do not exclude it.

  A lowering of the fuel temperature

  This may not be desirable for thermodynamic reasons. It was further proposed to use a

  oxygen fraction exceeding the stoichiometric amount

  T. Peschka, J. Hydrogen Energy, Vol 12,

No. 7, pp. 481-499, 1987).

  During the combustion of electrolysis gas,

  this extra fraction of oxygen must be ob-

  held from another source, most of the time

  from gas bottles. There, manipulation of

  oxygen scavengers is problematic because of the risk of

  than explosion. An excess of oxygen in the combustion chamber is also reflected in the high temperatures, by a significant corrosion of the material, so that the produced water is dirty and can not

  be directly reused for electrolysis.

  For the combustion of hydrogen during

  the enrichment of hydrogen isotopes by

  catalytic processes, combustion devices with

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  catalytic action are therefore also pre-

  in general (Robert E. Ellis et al., Deve-

  lopment of Combine Electrolysis Catalytic Exchange, Final Report, June 24, 1982, MLM-2952, Mound Facility Miamisburg, Ohio 45342). In these combustion units operating catalytically, hydrogen is catalytically burned

  with oxygen in contact with platinum. The temperature

  The reaction temperature does not exceed 600 ° C, so

  - 10 that there is no formation of NOx.

  Platinum immediately turns on a mixture

  of hydrogen and oxygen. For this reason, hydro-

  The gene must be diluted below the limit of

4 volumes%.

  Catalytic combustion is not economically

  that because of the high fraction of foreign gases, because of the adjustment expense for the dilution of

  hydrogen, and the high price of the catalyst.

  The problem that arises for the invention is

  to achieve the combustion of hydrogen with oxygen

  safer, especially without risk of explo-

sion, and in a simpler way.

  In addition, the formation of NOx and / or acid

nitric acid should be avoided.

  The water produced must be recoverable and not in practice soiled by products

  corrosion. The combustion process must, in

  to be completely unfolded and

  that the flame does not go out unintentionally.

  Investments and operating costs

  such a device for the implementation of the

combustion must be reduced.

  The part of the problem which concerns the procedure

  combustion die is resolved in that an overpressure

  is obtained in the combustion chamber by introducing

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  leaving a non-combustible gas, with the exception of oxygen. The water vapor that starts during combustion is completely condensed and collected in a container. As non-combustible gas,

carbon dioxide.

  As a non-combustible gas, a gas is used

rare, preferably argon.

  In the water starting, condensed and

  collected, we introduce oxygen.

  Water starting, condensed and col-

read, is heated.

  The overpressure rises to 1 bar,

  preferably, from 100 to 3005mPa.

  The part of the problem concerning the

  for the implementation of the invention is solved according to the invention in that:

  (a) the closed combustion chamber is in communica-

  directly through at least one

  gastight pipeline with a tank

  water reader disposed below, b) the combustion chamber and the water collecting tank are made so that they are gas-tight, c) in the combustion chamber or in the

  gas chambers of the water collecting container,

  bQueue a pipeline through the-

  a non-combustible gas, with the exception of hydrogen, is supplied to the device, d) the combustion chamber and / or the gas chamber of the water collecting vessel share at least one bleed pipe, e ) the flow resistance of the purge line or the purge lines is permanently or temporarily so high that the arrival of the non-combustible gas causes

an overpressure.

  The combustion chamber and the water collecting container are interconnected by two channels, the first of which balances the

  pressure, and the second of which flows into the

  water collector, the water being born during

of combustion.

  The first pipeline includes a

  flame arrestor and penetrates at least

  a few millimeters in the combustion chamber.

  The second channel comprises either a

  flame retardant device with low

  flow line is a U-shaped curved part. The purge line can be closed by a valve which is only open when a predetermined overpressure is reached or

exceeded.

  The water collecting container comprises

  below the water level, a frit and below this frit, a pipe for feeding

in oxygen.

  Via a pipeline for oxygen supply, part of the fraction

  stoichiometric amount of oxygen is derived.

  The device according to the invention for the implementation of combustion and a completely

  this device are shown in Figures 1 and 2.

  Figure 1 represents an experimental schema

tal according to the invention.

  Figure 2 is a variant of Figure 1.

  It turned out that already, because of the creation

  low overpressure, by introducing a

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  non-combustible gas, the combustion process can

  was to be accomplished in a safe manner, without

  NOx / HNO3 and without involuntary flame extinction.

  As non - combustible gases, it is possible to use mainly argon and. bi-carbon oxide. The quantity of non-combustible gases to be introduced depends on

  essentially dimensions of the chamber of communication

  bustion 2 and the realization of the pipeline of

purge 11.

  Advantageously, one places on the channeling

  purge valve, a valve 13 controlled by pressure and reacting quickly, this valve opening only for an overpressure of for example 2005mPa. We

  can thus use a large purge pipe

  transversal section, advantageous for reasons

  of safety, without thereby resulting in a

  high gas content. The overpressure to be established is

  above all, according to the dimensions of the combustion chamber. It must be chosen so that even

  for large pressure fluctuations, the pres-

  in the combustion chamber of at least

  1.05 Pa, otherwise the flame may extinguish

  dre. Other embodiments of the purge line, for example a tube with a high resistance to flow, are however also possible and

should not be excluded.

  Advantageously, all the pipes that open into the combustion chamber must be protected by non-return devices flame. When the water collecting container 18 is not directly flanged on the combustion chamber, the incorporation of a flame retardant device in the water discharge pipe 9, can then cause problems, when the free evacuation is hindered. The water level then rises in the combustion chamber and this results in extinction of the flame. For this reason, it is most of the time more advantageous to make the U-shaped water discharge pipe, in which case the lengths of the legs of the U must be tuned to the desired pressure difference. therefore to the flow resistance of the line of equalization of

pressure. -

  When it is expected in the combustion chamber, as a result of the material used, corrosion and water pollution by metal ions, will advantageously be used to obtain the overpressure, the carbon dioxide which is, in any case, less expensive. In addition, one can

  thus to remove from the reaction water the metallic impurities

  als. Carbon dioxide dissolves in the reaction water. Corrosion metal products are transformed either into insoluble carbonate or into

  hydrogen carbonate. Hydrogen carbonates can

  They may be converted by heating their aqueous solution or by bubbling oxygen into insoluble carbonates. In both cases the excess carbon dioxide is removed from the aqueous solution at the same time.

  The oxygen sparge is usually

  run for energy reasons.

  Advantageously, a small portion of

  the reaction oxygen is derived (with the aid of a

  pope 14) and introduced to the bottom of the collecting tank

  18. A frit 16 disposed above the

  introduces, on the one hand, uniformly

  oxygen and prevents, on the other hand,

  solid stanzas arrive in the pipeline of

  evacuation 17 of the water collecting tank.

  Due to the presence in the combustion chambers of water vapor, there is no risk that the carbon dioxide is converted into carbon monoxide in contact with hydrogen. Potentially formed carbon monoxide would react with the vapor

  water to give hydrogen and carbon dioxide.

  bone. The invention will be explained in more detail

  hereinafter using exemplary embodiments.

  The experimental device is made of stainless steel and is shown in Figure 1. It consists of a cooled combustion device 1 with a combustion chamber 2, closed and gas-tight, about 50-liters, and which is supplied with reaction gas via the pipeline

  3 for hydrogen and line 4 for oxy-

  gene. Both pipes have provisions

  flame arrestors (not shown). Before igniting the burner, only the oxygen is supplied via the nozzle 8. The hydrogen is sent via a three-way valve 5 into a starting pipe 6 which opens into a

  hood and on which is placed a control valve 7

  due to the pressure. The nozzle 8 comprises, as described in DE-OS 35 05 513 Ai, a thread

  ignition may be electrically heated.

  When the ignition wire has reached the

  ignition temperature (about 700 C) and when the

  pressure in the starter line is higher than

  greater than the sum of the pressure loss on the nozzle

  and the pressure in the combustion chamber, the hy-

* drogen is sent to the combustion chamber, or

  it lights up. The flame is monitored

electrically.

  The evacuated water flows via a U-shaped water discharge pipe 9 into a water collecting vessel 18, cooled and having a level control. A pressure equalizing pipe 10 ensures the equalization of the pressures prevailing in the combustion chamber and

  in the water collecting container.

  The entire device is connected to the envi-

  through a pipeline of

purge 11.

  a) Combustion at atmospheric pressure -

  As a purge line, we use a

short section of tube (10 x 1 mm).

  Electronically produced hydrogen (6m3 / h) and electrolytically produced oxygen (3m3 / h) are brominated at atmospheric pressure. The combustion is

  maintained for about 8 hours. The evacuated water pre-

  a nitric acid concentration of about 22000 ppm NO3 corresponding to a pH value of 0.5 and this water contains significant amounts of

  corrosion products of fine granulations and

dissolved corrosion products.

  b) Purge line with high resistance to

the flow -

  The experiment is renewed with a combustion chamber cleaned by the same conditions as in a). To the purge line is connected a sintered metal filter with a high resistance to

flow.

  It occurs in 1 hour on average 3 to 6

  pressures of 0.15 Pa or more, although the electrolysis cell operates on a regular basis. The flame

  then goes off each time and must be

  Lumee. The water is heavily polluted by HN03 and by

corrosion products.

c) Overpressure combustion -

  The experience is renewed with a new

  the combustion chamber under the same conditions as in a), the water collecting tank being however provided with a pipe 12, through which 40 to 60 liters of argon per hour are introduced into the space at above the water level. The purge line is equipped with an electromagnetic valve 13

  commanded by pressure, through the intermediary of

  which line 11 is only open for

  pressures above 11705 mPa.

  There is no nitric acid in

  the evacuated water. The pH value is around 7. In

  the absence of corrosion products, whether dissolved or undissolved. During an inspection, the combustion chamber proves to be free from corrosion sites and presents a

shiny metallic.

  The combustion is complete. With a specto-

  meter of masses one can not highlight, after

  about 1 hour of operation, neither oxygen nor hy-

  drogen in the purge pipeline. This experience

  this burning was continued for several

  weeks without the flame going off involuntarily.

is lying.

Claims (14)

  1.- Process for the combustion of hydrogen   with oxygen in ratios of volumes   proximally stoichiometrically by a flame in a closed and cooled combustion chamber, and which is in communication with the environment, a process in which water vapor and / or   condensed water, characterized in that one   pressure is obtained in the combustion chamber (2) by introducing a non-combustible gas with the exception oxygen.   2. The process according to claim 1, wherein   in that the water vapor originating during combustion is completely condensed and collected in a container.   3. The process according to claim 1, wherein   in use as a non-combustible gas bi-carbon oxide.   4. The process according to claim 1, wherein   terized in that it is used as a non-combustible gas,   a rare gas, preferably argon.   5. A process according to claim 2, characterized   terized in that in the water that starts   collected and collected, oxygen is introduced.   6. A process according to claim 2, characterized   terized in that the water starting, condensed and collected, is heated.   7. Process according to any one of   claims 1, 3 or 4, characterized in that the over-   up to 1 bar, being preferably this from 100 to 3005 mPa.   8.- Arrangement for implementing the   process according to any one of claims 1 to 7, characterized in that:   a) the closed combustion chamber (2) is in communication   directly or through   less a gas-tight pipeline with a   water collector (18) placed underneath, (b) the combustion chamber and the water collector tank are constructed so that they are watertight to gases.   (c) in the combustion chamber or in the   of gas from the water collection vessel, opens   a pipe (12) via the   a non-combustible gas, with the exception of hydrogen, is supplied to the device, d) from the combustion chamber and / or the gas chamber of the water collecting vessel, leaves at least one bleed pipe ( 11), e) the flow resistance of the purge line or purge lines, is permanently or temporarily, sufficiently high that the arrival of the non-combustible gas causes an overpressure.   9.- Device according to claim 8,   characterized in that the combustion chamber and the   water collecting container are interconnected by   two pipes, the first of which (10) ensures   balancing the pressure, and the second (9) conveys in the water collecting container, the water   arising during combustion.   10.- Device according to claim 9,   characterized in that the first channel   takes a non-return flame device and penetrates at least a few millimeters into the combustion chamber. 11.- Device according to claim 9,   characterized in that the second pipeline comprises   te, either a non-return flame device with low flow resistance, or a U-shaped curved part. 12.- Device according to claim 8, characterized in that the purge pipe is   likely to be closed by a valve that is not   only when a predetermined overpressure is hue or exceeded.   13.- Device according to claim 8, characterized in that the water collecting container comprises below the water level, a frit   (16) and below this frit (16) a canalisa-   tion (15) for the supply of oxygen.   14.- Device according to claim 13,   characterized in that via a channel   (15) for the supply of oxygen, a part   of the stoichiometric fraction of the volume of oxygen is not derived