FR2481945A1 - Neutralising noxious cpds. in exhaust gas from IC engines - where gas is mixed with ambient air, and then exposed to UV rays which convert noxious cpds. into harmless substances - Google Patents

Abstract

An excess of air is mixed with the exhaust gas, and the mixt. is then exposed for at least 0.1 second to ultraviolet rays (UV) with a wavelength of 130-315 nm, pref. 145-300 nm. The UV rays pref. create nascent oxygen in the mixt.; and are pref. obtd. from a low pressure Hg vapour lamp; an electric arc; a lamp contg. H2 or Xe; or a spark lamp. The air added to the exhaust gas is pref. first enriched with ozone. The pref. appts. consists of an exhaust gas pipe provided with an air inlet and joined by anti-vibration mountings to a chamber contg. a UV lamp and fitted with an exit pipe for the treated gas. Esp. for use on petrol or diesel engines. The invention is less expensive than conventional methods of purificn. of exhaust gas, which use costly catalysts and also reduce the efficiency of fuel consumption.

Description

 The present invention relates to a process for neutralizing harmful effluents from the combustion gases of heat engines9 such as internal combustion engines (petrol and diesel engines in particular), that is to say a process transforming said effluents harmful gases into non-toxic gases with a high conversion rate. It also relates to the devices implementing this process and the installations or vehicles comprising such devices.

The harmful gaseous effluents generated by heat engines are mainly nitrogen oxides such as nitrous oxide or nitrous oxide NO and nitrogen peroxide FIO, ~ carbon monoxide CO; sulfur oxides, such as sulfur dioxide S02 or sulfuric anhydride 533, and their derivatives; unburnt hydrocarbons or produced by condensation and / or cyclization, during combustion, from lighter hydrocarbons e and lead and its derivatives.

 The processes currently used to reduce the quantity of these noxious products and thus reduce the atmospheric pollution due to the exhaust gases from the abovementioned engines are based on the use of catalytic masses or use absolute masses.

The catalytic masses based on noble metals deposited on inert supports transform certain harmful products, in the presence of excess air or oxygen, at a sufficiently high temperature, of the order of 400 to 500 ° C. when using air, according to reactions

Part of the CY Hy hydrocarbons can also be oxidized
The nitrogen oxides NOz are, depending on the nature of the cataly
will either be reduced to nitrogen, will be further oxidized when possible, or still be fixed on the hydrocarbons.

Such a method has the following drawbacks
1) the noble metals used, for example platina and platina
rhodium, are costal
2) catalyst cases require the use of fuels
free from sulfur OR slightly sulfur-free, and containing no
lead (unusable premium fuel) classic poison of
catalysts, which considerably limits the scope of application
cation of said process
3) the efficiency of the catalytic masses depends on the temperature
re exhaust gases, so that in the case of
diesel engines or this temperature is too low, the
process does not prevent pollution of the atmosphere;
4) this efficiency is also reduced by the presence of
halogenated ves, e.g. chlorinated, used as additives
detergents in fuel, since these derivatives
favor addition reactions, not reactions
oxidation.

5) the use of catalytic masses leads to an im
bearing pressure loss in the circuit. exhaust gas
ment C100 to 200 mm of water) and therefore a drop in
motor efficiency corresponding to an over consumption of
fuel in the range of 5 to 8 #.

According to the process using absorbent masses, generally based on iron and possibly on alumina, the volatile aromatic organic compounds, such as aldehydes and alcohols, formed during the combustion of diesel are adsorbed; this process is of some interest, given the absence of harmful nitrogen compounds, in this case, since it eliminates odors and reduces the risk of fire, for example in the forest, by gases exhaust, but it is not applicable to engines using petrol since it does not then eliminate the most harmful compounds.

The method according to the invention overcomes the drawbacks of the known methods described above by the fact that it is very effective, that it is applicable to any type of fuel containing or not containing additives, that it does not cause any significant pressure drop in the exhaust pipes, thus avoiding any overconsumption of fuel and that it is not expensive,
This process is essentially characterized in that it consists in introducing an excess of air into said exhaust gases so as to obtain an intimate mixture then in subjecting said melanqe to irradiation by ultraviolet radiation of wavelength between about 1,300 and 3,150, preferably between 1,450 and 3 oeo A, for at least 0.1 seconds.

The ultraviolet radiation used belonged to the medium ultraviolet (2 800 - 3 150 At, to the far ultraviolet C1 850 - 2 000 to 2 800 A) and / or to the Schumann zone (below 1 850 A ); under these conditions, this radiation, by acting on the air mixed with the exhaust gas, produces nascent oxygen or monoatomic oxygen, according to the reaction 02 0 + 0. In addition, nitrogen peroxide and protoxide d are broken down according to the following reactions

 On the other hand, the ultraviolet energy received by the exhaust gases does not allow the molecules of nitrogen and carbon monoxide CO to be split. The monoatomic nitrogen formed and the unused monoatomic oxygen are ultimately found in the form of diatomic nitrogen and oxygen.

 The nascent oxygen thus released is used to oxidize carbon monoxide to carbon dioxide and hydrocarbons to carbon dioxide and water. However, as the nascent oxygen is very reactive, but has a very short lifespan, the arrival of the excess air must take place so that it is intimately mixed with the exhaust gases of the engine before reaching the area where ultraviolet irradiation takes place; in other words, the introduction of excess air into the exhaust gases must be carried out sufficiently upstream of said zone, possibly using, in accordance with the present invention, means for mixing the exhaust gas - air mixture, for example baffles and / or a venturi, in the exhaust pipe section where the air - exhaust gas mixture circulates. In accordance with another characteristic of the invention, the air to be incorporated into the exhaust gases is subjected to the action of electrical aromas, so that it contains ozone which promotes the oxidation reactions of the carbon monoxide and hydrocarbons.

The source of ultraviolet radiation used is preferably a mercury vapor lamp, advantageously of the low pressure type, which emits in the interval 1,400 - 3,000 (maximum intensity of emission for 2,537 A), setting work of a low pressure allowing, in itself known to reduce the absorption of ultraviolet radiation by the emitting vapor, we can also advantageously use spark lamps in which the spectrum of sparks (ion lines) is superimposed on the lines of the arc (production of ultraviolet radiation of wavelength less than 1,850). Of course, many other sources can be used, in particular the metallic carbon arc (medium ultraviolet), the hydrogen lamp and the polymetallic arcs (far ultraviolet), as well as the hydrogen lamp and the xenon lamp (transition zone between the distant UV and the Schumann area). These sources can be powered by accumulator batteries, which allows, in the case of an internal combustion engine of a motor vehicle, to supply said source by the vehicle's accumulator battery.

The device for implementing the aforementioned method comprises, on the path of the exhaust pipes of the heat engine, from upstream to downstream, an upstream section of pipe where the exhaust gases circulate, which is optionally provided with means for aforementioned mixing and to which is connected an air intake pipe, a reaction chamber on the oaroi of which is adapted at least one source of ultraviolet radiation of length
e wave between 1300 and 3150 A and a downstream exhaust section of said gases, this device being preferably adapted on the downstream end of said exhaust pipes.

According to a characteristic of the invention, the source of ultraviolet radiation is protected by one or more anti-vibration seals placed between the aforementioned upstream section and the reaction chamber and between the aforementioned downstream section and said reaction chamber; it is also possible, according to a variant according to the invention, to interpose an annular anti-vibration seal between the reaction chamber and the source of ultraviolet radiation.

 The aforementioned reaction chamber is advantageously provided with a coating reflecting ultraviolet radiation (nickel, magnesium oxide, etc.) so that it passes through said chamber several times, in the transverse direction, which allows, for a diameter Given this, to increase the radiant energy received by the gas mixture or, for the same dose of irradiation, to use a small diameter olus reaction chamber.

According to another characteristic of the invention, several sources of ultraviolet radiation are used placed in parallel, that is to say at a me # e distance from the entrance to the reaction chamber i st / or in series, that is to say staggered along said reaction chamber, on the path of the aforementioned gas mixture
In the case of a motor vehicle of average characteristics, the electric power consumed by the single source or the total power of the different sources to produce the desired effects in the exhaust gases is less than 100 W, which allows example of supplying a source, such as a mercury vapor lamp, emitting radiation of the order of 1.4 to 2.8. 10 7 quants of energy per second and per useful centimeter of source length.

Other characteristics, objects or advantages of the invention will appear during the following description of several embodiments, given without limitation, with reference to the accompanying drawings in which
- Figure 1 shows a sectional axial lcngitudinele section
of a device according to an embodiment of the invention
and
- Figure 2 represents1 also in longitudinal section axia-
them a device according to another embodiment of the
vention.

 FIG. 1 shows a device for neutralizing harmful tributaries of the exhaust gases of a heat engine which comprises, on the path of the exhaust pipes of this engine, from upstream to downstream in the direction of gas flow, an upstream section 1 of piping where said exhaust gases circulate and to which an air intake piping 2 is connected, a reaction chamber 3 on the wall of which is adapted a source of ultraviolet radiation 4 and a downstream section 5 of exhaust of said gases; the air intake pipe 2 opens in the axis of the upstream section 1 at the level of an internal bulge 6 of said section, forming a venturi, which allows the suction of the air, brought by the pipe 2, by the flow of exhaust gases s the air intake pipe 2 opens, at its upstream end, into the atnosohere, directly or through a device producing electrical aromas for the effect of form ozone in the air passing through said pipe 2.

The reaction chamber 3 is generally cylindrical in shape, in its central part, with a diameter of approximately 150 to 200 mm, the length of this chamber being approximately 300 to 500 mm, in order to
that, taking into account the flow rate and the speed of the exhaust gases mixed with the air, the latter are subjected to the action of ultraviolet radiation from the source 4 for at least approximately 0.1 seconds.

 The source 4 is for example constituted by a mercury vapor lamp whose wall is formed by a straight quartz tube, as in the example shown, or curved, according to a variant according to the invention; this lamp is mounted, by means of the support arm 7, in a recess in the side wall of the reaction chamber 3 and it is supplied with electrical energy by the conductors 8 passing through the insulating passages 9.

The power of the radiation emitted by this lamp, expressed in quanta of energy is about 2.1 x 10 per second and per useful centimeter (measured according to the length of the lamp); the power of this lamp is less than 100 W (effective operating voltage: 10 volts per centimeter; starting voltage: 100 volts).

Lv source 4 is protected here by two anti-vibration seals; the seal 10 is an annular seal placed between flanges belonging respectively to the upstream section and to the reaction chamber 3, while the seal 11 is an annular seal placed between flanges asnecting respectively to the downstream section 5 and to the reaction chamber reaction 3; of course these seals are made of an elastomer capable of withstanding the temperature of the exhaust gases. To promote the mixing of the air - exhaust gas mixture and obtain an intimate mixture before its exposure to the ultraviolet ray in the reaction chamber 3, the device comprises, at the inlet of the latter, baffles 12.

The device of the embodiment of FIG. 2 comprises, in a manner entirely similar to FIG. 1, an upstream section 1 ′ of exhaust pipe to which the air intake pipe 2 ′ is connected and which is provided with baffles 12 ', a reaction chamber 3' and a downstream section of exhaust pipe 5 ', the latter comprising here baffles 13.

The ultraviolet irradiation is carried out here by two sources 14 and 14 ', made up D, r exemole by lamps with mercury value whose part is a quartz tube, as represented these two lamps are arranged in series, that is to say say that the gaseous mixture passes successively, in passing through the reaction chamber 3 ′, under the radiation of the lamp 14 then under the radiation of the lamp 14 ′; these lamps are here mounted on support lids, respectively 15 and 15 ′, engaged in suitable openings in the side wall of the reaction chamber 3 ′; annular elastomer seals, resoactively 16 and le̲, here extend the lamps 14 and 14 'from vibrations Each seal is interposed between the side wall of the chamber 3' and a peripheral rim, 15a or 15'a, of the seal 15 or 15
The lamps 14 and 14 ′ are electrically supplied by conductors such as 17 passing through insulating passages such as 18 and they are supported by the lids through arms such as 19.

The diameter of the reaction chamber is here smaller than that of the reaction chamber 3 of the device of FIG. 1, for example approximately 60 mm instead of 150 to 200 mm and the internal surface of this reaction chamber 3 ′ is provided a coating 20 reflecting ultraviolet radiation, for example based on nickel or magnesium oxide, so that the radiation # emitted by the lamps 14 and 14 ′ crosses the tube several times in the transverse direction of that -this and that the radiant energy received by the gas mixture is increased, which compensates for the reduction in cross section compared to the case in FIG. 1 9 indeed, due to the reduction in cross section, the linear speed of the mixture gas in the reaction chamber 30 is higher than in the reaction chamber 3 and the residence time of each elementary amount of mixture is shorter there; on the other hand, each elementary quantity receives radiant energy at a higher rate, since the radiation reflected by the side walls of the reaction chamber 3 'is added to the radiation received directly from a lamp (it is assumed here that the 'radiant energy emitted by the two lamps 14 and 14' is of the same order of magnitude as that emitted by the single lamp 4 of the device of Figure 1)
The devices of Figures I and 2 are particularly suitable for equipping a conventional motor vehicle, the diameter of the upstream section 1 or 1 and the downstream section 5 or 5 r having the usual dismetre of the exhaust pipe such a vehicle; the surface of the tranayarsal section of the intake pipe 2 or 2 ′ is advantageously of the order of 5% of the cross section of the exhaust gas pipe; of course, lamps such as 4.

14 and 14 'can be powered by the vehicle's storage battery.

 The flow rate or quantity of air to be introduced is of the order of 2% to 10 by volume relative to the flow rate or quantity of combustion gas; for example. for a four-stroke internal combustion engine running on petrol7 of average displacement t7 at 8 tax horsepower). producing 70 to 90 liters reduced to normal pressure and temperature conditions) of exhaust gas per second, at a linear speed of 40 to 60 m / s in the exhaust piping. the optimum quantity of air to be introduced in accordance with the invention is 4 - 8% by volume relative to the volume of the exhaust gases (normal conditions.

It goes without saying that the present invention is in no way limited to the embodiments described which have been given for purely explanatory purposes. Consequently, all means equivalent to the means or embodiments described, modifications or variants of these means or embodiments also form part of the present invention as defined by the claims below.

Claims (7)

R E V E N D I C A T I O N S  1. Method for neutralizing harmful effluents contained in the exhaust gases of thermal engines, in particular internal combustion engines such as petrol engines and diesel engines, characterized in that it consists in introducing an excess of air into the said exhaust gases so as to obtain an intimate mixture, pui5 to subject the said mixture to irradiation with ultraviolet radiation of wavelength between approximately 1 aoe and 3 150 A, preferably between 1450 and 3000, during at least 0.1 seconds. 2. Neutralization process according to claim 1, characterized in that an incipient oxygen-producing radiation is used 3 neutralization process salon claim 1, characterized in that one uses as a source of ultraviolet radiation a mercury vapor lamp, preferably low pressure, an electric arc, a hydrogen lamp, a xenon lamp or a lamp spark 4. Method according to claim 1, characterized in that the air introduced into the exhaust gases has previously been enriched with ozone by subjecting said air to electrical aromas 5. Device for implementing the method of claim 1, characterized in that it comprises, on the path of the exhaust pipes of a thermal engine, from upstream to downstream, an upstream section of piping where circulating exhaust gases and to which is connected an air intake pipe, a reaction chamber on the oaroi of which is adapted at least one source of ultraviolet radiation of wavelength between 1300 and 3150 and a section downstream of said exhaust, this device being preferably adapted on the downstream end of said exhaust pipes 5 Device according to claim 5, characterized in that the above source is protected by one or more anti-vibration seals placed between the upstream section and the aforementioned reaction chamber and between the downstream section and the reaction chamber  recited and / or entered said source and said reaction chamber, this source being in particular a low-pressure mercury vapor lamp supplied, in the case of a motor vehicle, by the storage battery of said vehicle.  7. Device according to claim 5, characterized in that the aforementioned reaction chamber is provided with a coating reflecting ultraviolet radiation so that it crosses said chamber several times and increases the radiant energy received by the gas mixture.  8. Device according to claim 5, characterized in that the above-mentioned upstream section comprises means for mixing the exhaust gas - air mixture constituted in particular because baffles and / or a venturi.  9. Device according to claim 5, characterized in that several sources of ultraviolet radiation are used in parallel or in series on the path of the above-mentioned gas mixture. 10. Device according to claim 5, characterized in that the ultraviolet radiation power emitted by the aforementioned source is of the order of 1.4 to 2.8. 1013 quanta of energy per second and per useful centimeter of length of said source.