DE10018792C1 - Motor exhaust gas processing system to reduce hazardous emissions, separates hydrocarbon components with low boiling point into vapor fractions to be reformed and reduced and high boiling point components are returned to the fuel tank - Google Patents

Abstract

To reduce hazardous emissions from the exhaust gas of an internal combustion motor, initially the components of the hydrocarbons with a low boiling point are separated by boiling point fractions and evaporated before the next stage where hydrogen or carbon monoxide is produced only from these components. The temperature for the boiling point fractionating is = 200[deg] C. The separated components are fed by a dosing unit (6) to a reforming reactor (7).to give the hydrogen or carbon monoxide. Air is mixed with the components at the dosing unit (6). The components of the hydrocarbons with a high boiling point are returned to the fuel tank (2). The remaining hydrogen and/or carbon monoxide in the exhaust gas flow, after the reduction stage for hazardous matter, is passed through an oxidizing stage with air to oxidize the components into water and carbon dioxide. The water is taken from the steam reduction of the hydrogen from the low boiling point components. An independent claim is included for an exhaust gas processing system with a reforming reactor (7) and a fractionating unit (5) to separate and evaporate components with a low boiling point from the components with a high boiling point. The outlet of the fractionating unit (5) leads the components with a low boiling point to the reforming reactor (7). A dosing unit (6) is between the fractionating stage (5) and the reforming reactor (7), to give a dosed feed into the reactor (7), mixed with air from an air feed supply (10) with an air heater (11). The dosing unit (6) is a jet. The fractionating unit (5) is in the fuel return line (4,4a) from the motor (1) to the fuel tank (2). The fractionating unit (5) has a pressure vessel, a heater and a rising tube to take the vaporized components with a low boiling point. The heater is electrical and/or is a heat exchanger using the motor heat. A CO shift stage is after the reformer (7). A particle filter is after the reduction catalyst. An oxidizing catalyst (15) is after the reduction reactor (14). Air is fed from the air supplies (10,16) through the oxidizing catalyst (15) and/or the particle filter.

Description

The present invention relates to a method and a pre Direction for pollutant reduction in exhaust gases from combustion Engines.

The reduction of pollutants in exhaust gases is a contribution to Reduction of environmental pollution from motor vehicles. Moreover see the legal regulations in the coming years Lower the permissible exhaust gas limit values.

A method and a system are known from US Pat. No. 4,125,090 knows about an internal combustion engine only with hydrogen To operate gas as fuel. This is fuel at for example gasoline, in a reformer through partial oxidation in reformed fuel, namely the hydrogen-containing gas converted. To make the system's performance data the difference adapting operational requirements, both Air-fuel ratio of the reformer as well as the ratio reformed fuel and air for combustion motor controlled.

A device for reducing nitrogen oxides for internal combustion engines is known from US Pat. No. 5,412,946. The device comprises an internal combustion engine, a hydrogen generator including a reforming catalyst, a further catalyst for NO _x reduction, which is arranged in the exhaust line of the internal combustion engine, means for supplying the generated hydrogen to the reduction catalyst and a mixer on the input side of the reduction catalyst to mix the exhaust gases with the generated hydrogen. Palladium (Pd) and platinum (PT) catalysts with copper (Cu), chromium (Cr) and nickel (Ni), Cu-Ni-Cr / aluminum catalysts, Cu-Mn- / Cu- are used as catalysts for reforming the hydrogen. Zn catalysts and catalysts containing nickel (Ni), cobalt (Co) and rhodium (Rh) as the catalyst material are proposed. A platinum catalyst, which is applied to a zeolite, silicon or aluminum support, is used to reduce the NO _x . Methanol and hydrocarbons such as LPG (liquefied petroleum gas) and natural gas are disclosed as fuels for hydrogen production.

From US Pat. No. 4,233,188 a catalyst for treating NO _x , CO and unburned hydrocarbons from exhaust gas from internal combustion engines is known. The catalyst includes a substrate, a three-way catalyst made of iridium, an oxygen storage material selected from the group consisting of nickel and tungsten, and an oxidation catalyst made of palladium.

From US-PS 4 059 076 a fuel system for a Ver internal combustion engine known. In a reformer, hydro substances essentially converted to hydrogen and carbon monoxide changes. This reformed gas serves as fuel for the Internal combustion engine. Next to it is an auxiliary combustion engine seen that with the hydrocarbons as fuel in egg a lean air-fuel mixture is operated. The Auxiliary combustion engine essentially serves to react generate heat for the reformer. In addition, the Ab gases of the auxiliary combustion engine in a mixing chamber in front of the Reformer mixed with the hydrocarbons. The one for the Re Formation of the hydrocarbons required oxygen is on this way as a component of the exhaust gas posed.

DE 195 47 921 C2 describes a method for reducing Nitrogen oxides in exhaust gases from motor vehicles by reduction  known a catalyst. The what needed for the reduction Hydrogen is obtained by electrolysis using a liquid generated fixed electrolytes.

DE 195 48 189 C2 describes another method for reducing adornment of nitrogen oxides in exhaust gases from motor vehicles Reduction on a catalyst known. The one for reduction required hydrogen is obtained by steam reforming and / or partial oxidation of hydrocarbons, the catalyst being controllable independently of the engine exhaust is heated.

For the reduction of nitrogen oxides and soot particles in exhaust gases from Internal combustion engines can also use small amounts of water serve fabric and carbon monoxide. An accurate and reliable Dosage of small amounts of liquid hydrocarbons for the reformer is difficult or needs a corresponding one Construction effort and is therefore expensive. As Eduk te for the production of hydrogen and carbon monoxide various hydrocarbons such as diesel, petrol, kerosene, LPG (Liquefied Petrol Gas) or alcohols such as methanol be set. The individual components of these fuels un differ in their suitability for reform tion to hydrogen and carbon monoxide.

In contrast, the invention has for its object a Ver drive and create a device that is reliable and inexpensive dosing even of small amounts of Koh Hydrogen oils allow and also a more effective refor Ensure hydrogenation and carbon monoxide.

On the one hand, a method with the Features of claim 1, on the other hand with a device the features of claim 8 proposed.

Accordingly, in a method according to the invention, in one first step essentially low-boiling components of the  Hydrocarbons separated by boiling point fractionation and evaporates before in a subsequent step only from this separated components of hydrogen or carbon monoxide be generated.

It has been shown that high-boiling components of coal Hydrogen bad to hydrogen and carbon monoxide to re are forming. Liquid hydrocarbons can also be used Dosing in small quantities is difficult. The hydrogen or carbon monoxide generation can be separated by separating them easily components, which are also easy to reform, by the high-boiling components, advantageously on the first called educt components with the favorable reaction properties be limited. Gases can also be found in small quantities dispense reliably and precisely without difficulty. The you Depoint fractionation is based on an easy evaporation boiling components. According to the invention, the separation of the components and the partial evaporation in one Process step advantageously a gaseous ed educt that is easier to produce even in small quantities doses, and at the same time the educt from the compo nents of hydrocarbons obtained for the reformie tion are particularly suitable. This means that an effective re Formation of hydrocarbons into hydrogen and coal monoxide, their presence as a reducing agent the quality the pollutant reduction of the exhaust gases significantly affected, ge is guaranteed.

With a device in which a reforming reactor Fractionation device for separating and evaporating easily boiling components versus high boiling components of the Hydrocarbons is connected upstream, the output of the Fractionation device for the low-boiling components with the reforming reactor is connected, the erfindungsge method in a simple manner become. The arrangement of the reforming reactor and fraction kidney device allows a compact design, so that the device  as an additional assembly behind a burn motor can be installed. The device according to the invention is also inexpensive to manufacture because of costs and also Space for a separate evaporator can be saved.

Advantageous embodiments of the invention result from the Dependent claims.

In an advantageous embodiment of the invention, the separated low-boiling components via a dosing device towards a reforming reactor to produce the water substance or carbon monoxide supplied. About the dosing device tion, the amount of the starting materials to be reformed may be appropriate be controlled.

In an advantageous development of the metering device these are designed so that the separated low-boiling com Components are mixed with air via the metering device can. There is no need for an additional mixing device become. Air and the separated low-boiling component can NEN to the reformer as a mixed gas via the dosing device tion are fed.

In a further expedient embodiment of the invention air supply means are provided on the metering device. The air supply means can be used as a fan or compressor be trained. These can also be used to NEN operating pressure to operate the metering device bring or control.

In a useful development of the invention are Heizmit are provided for preheating the air. This allows the Air before the reformer enters the operating system temperature to be preheated.  

In an advantageous embodiment of the invention, the Do siervorrichtung a nozzle. This sets one constructively simple and inexpensive solution.

In an advantageous development of the invention Fractionator in the fuel return line from Internal combustion engine arranged to the fuel tank. Since already ge rings of hydrogen and carbon monoxide for the reducti If the exhaust gases are sufficient, the need for coal water be covered by the return line without additional supply lines must be provided. Possible Verunreini for example B. with high-boiling oils are due to the boiling point point fractionation irrelevant.

In an advantageous embodiment of the invention, the Fractionator a pressure vessel, a heating device device and a riser pipe over which the low-boiling components ten of the hydrocarbons are discharged in gaseous form. A such a solution is structurally simple and still enables an effective separation of the liquid, high-boiling components of the evaporated low-boiling components via the Riser pipe. The operating pressure can also be set via the pressure vessel be built for the dosing device.

Further advantages and refinements of the invention result itself from the description and the accompanying drawing.

It is understood that the above and the following standing features to be explained not only in each specified combination, but also in other combinations or can be used alone, without the scope of to leave the present invention.

The invention is based on an embodiment in the Drawing is shown schematically and is below Described in detail with reference to the drawing.  

Fig. 1 is a highly schematic block diagram shows an inventive device.

Fig. 2 shows an enlarged section of the schematic representation of Fig. 1st

According to the invention, low-boiling components are first separated from hydrocarbons such as diesel or petrol in a fractionation step before hydrogen and carbon monoxide are generated from these components in a reformer. These are used as reducing agents for the reduction of exhaust gas pollutants such as nitrogen oxides and soot particles on a catalyst. Portions of hydrogen and carbon monoxide, which are still present in the exhaust gas stream even after the exhaust gas has been reduced, are oxidized with air to water and carbon dioxide in an oxidation step. An embodiment of an inventive device for performing the inventive method for pollutant reduction in exhaust gases from internal combustion engines is shown schematically in Fig. 1.

In Fig. 1 reference numeral 1 designates an internal combustion engine, and numeral 2 a tank for the fuel of the engine 1. The tank 2 is connected to the internal combustion engine 1 via a feed line 3 . In a fuel return line 4 from the combustion engine 1 to the tank 2 , a fractionator 5 is arranged. In the fractionator 5 , the easily components are separated from the high-boiling components of the fuel. The high-boiling components are returned to the tank 2 via a return line 4 a. The separated low-boiling components are fed to a reformer 7 in gaseous form. For this purpose, a metering device 6 is hen hen, which is preferably designed as a nozzle.

In the reformer 7 , hydrogen and carbon monoxide are generated from the low-boiling components of the fuel, which are used as reducing agents for exhaust gas purification. The reforming of hydrogen and carbon monoxide from hydrocarbons per se is known. The reformer 7 comprises a catalyst which contains, for example, nickel, cobalt or rhodium as the catalyst material. Through the known steam formation and / or partial oxidation, the hydrogen-containing gas used as the reducing agent is generated. For steam reforming, water can be passed into the reformer 7 via an inlet 9 . The air for the partial oxidation is fed to the reformer 7 via the nozzle 6 . For this purpose, an inlet 8 is provided on the nozzle 6 . The air can be supplied via a fan 10 or compressor 10 . At least part of the operating pressure of the nozzle 6 can be applied via the Ven tilator / compressor 10 . Heating means 11 such as heating spirals are also provided on the nozzle 6 in order to preheat the air to approximately 200 ° C. A CO shift stage (not shown) can be connected downstream of the reformer in order to increase the hydrogen yield.

Gases can be dosed reliably and precisely even in small quantities. It is also possible to regulate a dosage by the amount of heat input, ie by electrical heating. Another possibility is the dosing of the air supply via fan / compressor 10 .

The exhaust gas of the internal combustion engine 1 is fed into a reactor 14 via a line 13 . The hydrogen-containing gas is added as a reducing agent via a line 12 to the exhaust gas of the combustion engine 1 upstream of the reduction reactor 14 . The Reak gate 14 contains a catalyst with z. B. platinum as catalyst material. In the reduction reactor 14 , the reduction of, in particular, nitrogen oxides and soot particles of the exhaust gas on the catalyst takes place by means of hydrogen and / or carbon monoxide. After the reduction of hydrogen or carbon monoxide still present, air is converted into carbon dioxide and water by means of an oxidation catalyst 15 . The resulting water is fed via a line (not shown) to the inlet 9 of the reformer 7 for steam reforming. Air is supplied to the oxidation catalytic converter 15 via the line 16 via the compressor 11 . A particle filter (not shown) is arranged on the reduction reactor 14 . If necessary, this can be burned free via the line 17 by metering in air.

FIG. 2 shows the fractionation device 5 in an enlarged section of FIG. 1.

The fractionation device 5 comprises a pressure vessel 20 , a heating device 21 and a riser pipe 22 . In the exemplary embodiment shown, the heating device 21 is designed as an electrical heater. But it can also be formed as a heat exchanger, which uses the waste heat of the internal combustion engine 1 . Electric heating is preferred, however, because it can also be used during the starting process.

The pressure vessel 20 has an inlet for the fuel return line 4 and an outlet for the line 4 a. The fuel reaches the pressure tank 20 via the fuel return line 4 , where it is heated by the heating device 21 . The low-boiling components evaporate first and rise via the riser pipe 22 to the nozzle 6 . The remaining fuel, which consists of high-boiling components, is returned via line 4 a to tank 2 . This is a simple and effective fractionation of the fuel into light and high-boiling components.

The liquid level in the pressure vessel 20 is controlled so that the riser pipe 22 does not extend into the liquid. The pressure of the pressure vessel 20 can be used to build up the operating pressure for the nozzle 6 . Air can be added to the nozzle 6 via the inlet 8 . The outlet 23 of the nozzle 6 is connected to the reformer 7 .

Not only air, but also water can preferably be introduced into the reformer 7 . Since water recovery can be technically difficult, an expedient measure is to use a water content of the exhaust gas 13 of the combustion engine in a partial flow. Typically, the exhaust gas contains about 10-15% water, which can be used accordingly. In addition, z. B. in the exhaust gas of diesel engines also hold oxygen ent. In a favorable development of the invention, the fan / compressor 10 can also convey exhaust gas or, in the case of gasoline engines, preferred exhaust gas and air.

The supply of air is preferably advantageously possible through a branch after an exhaust gas turbocharger. There is an increased pressure there, so that a fan / compressor 10 could also be dispensed with under certain circumstances.

Claims (20)

1. Process for the reduction of pollutants from exhaust gases from combustion engines, in which pollutants, in particular nitrogen oxides and soot particles, are reduced on a catalyst with the addition of hydrogen and / or carbon monoxide, the water or carbon monoxide being formed by steam reforming and / or partial oxidation of hydrocarbons, in particular diesel fuel and petrol, are generated, characterized in that in a first step essentially low-boiling components of the hydrocarbons are separated and evaporated by boiling point fractionation before in a subsequent step only the separated components of the hydrogen or the Carbon monoxide is generated. 2. The method according to claim 1, characterized in that the Temperature at boiling point fractionation less than 200 ° C ge is chosen. 3. The method according to any one of claims 1 to 2, characterized in that the separated low-boiling components are fed via a metering device ( 6 ) to a reforming reactor ( 7 ) for generating the hydrogen or carbon monoxide. 4. The method according to claim 3, characterized in that the separated low-boiling components via the Dosiervor direction ( 6 ) air is mixed. 5. The method according to any one of claims 1 to 4, characterized in that the high-boiling components of the hydrocarbon materials are returned to the hydrocarbon tank ( 2 ). 6. The method according to any one of claims 1 to 5, characterized records that hydrogen and / or carbon monoxide, which after the pollutant reduction step is still present in the exhaust gas stream are in an oxidation step with air to water and coal be oxidized. 7. The method according to claim 6, characterized in that the water produced in this way for the steam reforming of water material from the low-boiling components of the hydrocarbon fabrics is used. 8. The device, in particular for carrying out the method according to any one of claims 1 to 7, with a reforming reactor ( 7 ) for generating hydrogen and carbon monoxide from hydrogen carbon by hydrogen reforming and / or partial oxidation and a reduction reactor ( 14 ) for reducing pollutants the exhaust gases while supplying hydrogen and / or carbon monoxide to a catalyst, characterized in that the reforming reactor ( 7 ) is preceded by a fractionation device ( 5 ) for separating and evaporating low-boiling components against high-boiling components of the hydrocarbons, the output ( 22 ) of the Fractionator ( 5 ) for the low-boiling components is connected to the reforming reactor ( 7 ). 9. The device according to claim 8, characterized in that between the output ( 22 ) of the fractionation device ( 5 ) for the low-boiling components and the reforming reactor ( 7 ), a metering device ( 6 ) is arranged, via which the low-boiling components the reforming reactor ( 7 ) can be fed. 10. Device according to one of claims 8 to 9, characterized in that the metering device ( 6 ) for adding air to the separated low-boiling components is ausgebil det. 11. The device according to claim 10, characterized in that air supply means ( 10 ) are provided. 12. The device according to one of claims 10 to 11, characterized in that heating means ( 11 ) for preheating the air are easily seen. 13. Device according to one of claims 9 to 12, characterized in that the metering device ( 6 ) is a nozzle. 14. Device according to one of claims 8 to 13, characterized in that the fractionation device ( 5 ) in the fuel return line ( 4 , 4 a) from the internal combustion engine ( 1 ) to the fuel tank ( 2 ) is arranged. 15. Device according to one of claims 8 to 14, characterized in that the fractionating device ( 5 ) a Druckbe container ( 20 ), a heating device ( 21 ) and a riser pipe ( 22 ) through which the low-boiling components of the hydrocarbons are discharged in gaseous form , includes. 16. Device according to one of claims 8 to 15, characterized in that the heating device ( 21 ) is designed as an electrical heater and / or as a heat exchanger which uses the waste heat of the internal combustion engine ( 1 ). 17. The device according to one of claims 8 to 16, characterized in that the reformer ( 7 ) is switched a CO shift stage nachge. 18. Device according to one of claims 8 to 17, characterized in that a particle filter is provided on the reduction catalyst ( 19 ). 19. The device according to one of claims 8 to 18, characterized in that the reduction reactor ( 14 ) is followed by an Oxidationska talysator ( 15 ) 20. Device according to one of claims 10 to 19, characterized in that the oxidation catalyst ( 15 ) and / or the particle filter air through the air supply means ( 10 , 16 ) can be guided.