WO2016034401A1

WO2016034401A1 - Device for the recovery of water from a gas and method for reducing nitrogen oxides

Info

Publication number: WO2016034401A1
Application number: PCT/EP2015/068930
Authority: WO
Inventors: Ulrich Sauter
Original assignee: Robert Bosch Gmbh
Priority date: 2014-09-02
Filing date: 2015-08-18
Publication date: 2016-03-10
Also published as: DE102014217450A1

Abstract

The invention relates to a device (30) for the recovery of water from a gas, which is adapted to supply water to an electrolyzer (50), wherein the electrolyzer (50) is designed to supply hydrogen to at least one nitrogen oxide reduction catalyst (23). The invention further relates to a process for reducing nitrogen oxides. This includes the extraction of water from a gas, the supply of water to an electrolyzer (50), and the supply of hydrogen from the electrolyzer (50) to at least one nitrogen oxide reduction catalyst (23).

Description

description

title

Apparatus for recovering water from a gas and method for

Nitric oxide reduction

The present invention relates to a device for recovering water from a gas. Furthermore, the invention relates to a method for nitrogen oxide reduction, in particular using the device according to the invention. In addition, the present invention relates to a computer program which is set up to carry out each step of the method according to the invention and to a machine-readable storage medium on which the computer program according to the invention is stored. Finally, the invention relates to an electronic control device which is set up to carry out a reduction of nitrogen oxide by means of the method according to the invention.

State of the art

Motor vehicles are today equipped with energy-saving internal combustion engines, which are mainly operated in combustion states that have an excess of air (lambda> 1). As a result, nitrogen oxides are formed, which must be reduced in the catalyst. For this purpose, two methods are known:

The Nitrogen Oxide Storage Catalyst (NSC) stores the nitrogen oxides. After that, they are reduced when the accumulator is full or in between in an operating condition of the internal combustion engine in which rich exhaust gas (lambda <1) is produced. The nitrogen oxides react to water, carbon dioxide and nitrogen. This is done by reacting the nitrogen oxides with hydrogen or carbon monoxide, which in this operating condition are present in the exhaust gas. Thereafter, the engine management is switched back to normal driving with lean exhaust.

When using a Selective Catalytic Reduction (SCR), a urea water solution (HWL) is added to the

Exhaust line is injected, generates ammonia and this reacts on a special catalyst with the nitrogen oxides to water and nitrogen. The exhaust gas is lean in this process (lambda> 1). However, the use of the SCR catalyst has the disadvantage that unreacted ammonia escapes from the catalyst when the HWL metering is too high and passes into the environment through this so-called slip. In addition, the

Urea water solution corrosive and requires a complex handling.

Both the NSC process and the SCR process are used to reduce nitrogen oxides in the exhaust gas of gasoline engines. In diesel engines, the SCR process is predominantly used because the diesel engine can not be operated favorably for a long time in the rich state at lambda <1. Here he produces a lot of soot. As an alternative to rich operation in NSC and urea metering in SCR, hydrogen upstream of the NSC and / or SCR catalyst may also be metered into the exhaust line and used to reduce nitrogen oxides. Hydrogen can either be carried in a small pressure tank or generated on board the motor vehicle by means of steam reforming or electrolysis of water. Water for electrolysis must be in the

Tank must be carried and must be refilled regularly.

DISCLOSURE OF THE INVENTION The apparatus for recovering water from a gas according to the invention is adapted to supply water to an electrolyzer. The electrolyzer is configured to supply hydrogen to at least one nitrogen oxide reduction catalyst. The at least one nitrogen oxide reduction catalyst is in particular an NSC catalyst and / or an SCR catalyst. In a motor vehicle, which has the device according to the invention, water for Generation of hydrogen by means of electrolysis not be carried and refueled, but can be obtained on board the motor vehicle.

It is preferred that the device for obtaining water from a gas is connected to the exhaust gas line of an internal combustion engine such that its exhaust gas can be supplied to the internal combustion engine. This makes it possible for the electrolyzer to supply water, which in fuel combustion in the

Internal combustion engine is created. Furthermore, it is preferred that the device for obtaining water from a gas is connected to an air conditioning system of a motor vehicle such that it can remove water from a condenser of the air conditioning system. This allows the electrolyzer to supply water from the ambient air.

In order to ensure a high quality of the water supplied to the electrolyzer, it is preferable that the device has a reverse osmosis unit arranged so that water leaving the water-collecting device is conditioned in the reverse osmosis unit before being supplied to the electrolyzer , Reverse osmosis has over alternative methods, such as the water purification by means of a

Ionenaustauschers, the advantage that this membrane process maintenance-free reaches very long operating times. On the other hand, an ion exchanger cartridge must be changed regularly or be designed to be extremely large for long periods of operation, which entails installation space and cost disadvantages.

Basically, however, the device may instead of the reverse osmosis unit or in addition to this also other components for

Have water treatment. This is in particular a mechanical filter for removing particles (abrasion), an activated carbon filter for removing hydrocarbons, and / or an ion exchanger for removing foreign ions, such as iron ions (especially Fe ²⁺ ) from the exhaust system.

The electrolyzer is preferably a PEM electrolyzer, that is a

Electrolyser with a proton-conducting polymer membrane (PEM). A PEM electrolyzer is due to its special compact design for the production of hydrogen on board a

Motor vehicle particularly suitable. Although it places high demands on the water quality of the water used for the electrolysis, in particular with regard to the foreign ion content, which may lead to a maximum permissible conductivity of the water of less than 1.0 μδ / ηηη or even less than 0.1 μδ / ηηη. However, these requirements can be met with the water production according to the invention.

Preferably, the apparatus comprises a hydrogen pressure tank arranged to allow hydrogen leaving the electrolyzer in the tank

Hydrogen pressure tank is temporarily stored, wherein it is supplied to the at least one nitrogen oxide reduction catalyst. The feeding can be done, for example, by the hydrogen upstream of the

Nitrogen oxide reduction catalyst is metered into the exhaust system. Of the

Hydrogen can do this in the electrolyzer directly at the required

Hydrogen tank pressure to be generated. For this he is preferred in one

Pressure range of 0.5 to 15 MPa, more preferably from 1 to 6 MPa, most preferably generated from 1 to 3 MPa.

The temporary storage of the hydrogen in the hydrogen pressure tank makes it possible to supply the nitrogen oxide reduction catalyst with hydrogen as needed.

In one embodiment of the invention, the electrolyzer is arranged to discharge oxygen generated in the electrolysis of water into the ambient air. This makes it possible to operate the oxygen side of the electrolyzer at atmospheric pressure.

In another embodiment of the invention is the

Nitrogen oxide reduction catalyst is arranged in an exhaust line, wherein a soot filter is arranged in the exhaust line. The electrolyzer is arranged to supply oxygen to the soot filter. This makes it possible to support the reduction of the soot collected in the soot filter by metering the oxygen produced during the electrolysis into the exhaust gas line upstream of the exhaust gas Soot filter. The feeding can be done, for example, by the hydrogen is metered upstream of the soot filter in the exhaust line.

It is particularly preferred that the device has an oxygen pressure tank arranged so that oxygen exiting the electrolyzer is temporarily stored in the oxygen pressure tank before being fed to the soot filter. For this purpose, the oxygen side of the electrolyzer can be operated at elevated pressure, so that the oxygen in the electrolyzer can be generated directly at the required oxygen tank pressure. The intermediate storage of the oxygen has the advantage that it can be supplied to the soot filter as needed during a regeneration operation.

The inventive method for nitrogen oxide reduction, in particular in the exhaust line of an internal combustion engine, comprises recovering water from a gas, supplying the water to an electrolyzer, and supplying hydrogen from the electrolyzer to at least one

Nitrogen oxide reduction catalyst. The recovery of water takes place preferably by means of the device according to the invention.

The computer program according to the invention is set up to carry out each step of the method according to the invention, in particular if it is executed on a computer or electronic control unit. It allows the implementation of the method according to the invention on an electronic control unit, without having to make any structural changes thereto. For this purpose, the computer program is stored in particular on the machine-readable storage medium according to the invention.

When the computer program according to the invention is played on an electronic control unit, the inventive electronic

Receive control unit which is adapted to perform a nitrogen oxide reduction by means of the method according to the invention.

Brief description of the drawings Embodiments of the invention are illustrated in the accompanying drawings and will be described in more detail in the following description.

Fig. 1 shows schematically components of a motor vehicle with a

Apparatus for obtaining water according to an embodiment of the invention.

Fig. 2 shows schematically components of a motor vehicle with a

Apparatus for obtaining water according to another

Embodiment of the invention.

Embodiments of the invention

In a motor vehicle with a device 30 for recovering water from a gas according to a first embodiment of the invention, an internal combustion engine 10 is arranged, which emits its exhaust gas in an exhaust line 20. This is shown in Fig. 1. In the exhaust line 20, a catalyst 21 for decreasing the hydrocarbon and carbon monoxide concentration of the exhaust gas, a soot filter 22, and a nitrogen oxide reduction catalyst 23 are arranged in downstream sequential order. The catalyst 21 is designed as an oxidation catalyst or as a 3-way catalyst. Of the

Nitrogen oxide reduction catalyst is designed as an NSC catalyst, as an SCR catalyst or as a combination of the two. Downstream of the

Nitrogen oxide reduction catalyst 23 branches off from the exhaust line 20 from a bypass, which returns a portion of the exhaust gas into the device 30 for recovering water from a gas into and then from this into the exhaust line 20. The device 30 for water extraction comprises a

Heat exchanger 31, on which water contained in the exhaust gas to a

Large part is condensed. Downstream of the heat exchanger 31 is located in the device 30 for recovering water, a mist eliminator 32, which separates the condensed water from the exhaust stream and out of the bypass, a first valve 33 passes. It enters a pump 41 which supplies the condensate to a reverse osmosis unit 42. This consists in the present case of a bundle of membrane filaments in a cartridge. Retentate contaminated with foreign ions and other pollutants from the exhaust system Reverse osmosis optionally partially is supplied to the pump 41 through a second valve 43 together with fresh condensate. Not again the pump 41 supplied retentate a third valve 44 is discarded. The high-purity permeate water of the reverse osmosis, which penetrates through the walls of the membrane filaments, is fed to the electrolyzer 50. Here it becomes one

Subjected to electrolysis, wherein at the cathode 51 of the electrolyzer 50th

Hydrogen is generated, which is supplied to a hydrogen pressure tank 60 under a pressure in the range of 0.5 to 15 MPa. Through a

Hydrogen outlet valve 61 of the hydrogen pressure tank 60 can be supplied to the nitrogen oxide reduction catalyst 23 as needed. For this purpose, it is fed into the exhaust gas line upstream of the catalytically active material of the nitrogen oxide reduction catalytic converter 23. When an NSC catalyst is used as the nitrogen oxide reduction catalyst 23, the hydrogen is introduced when the storage is full. If, on the other hand, an S CR catalyst is used as the nitrogen oxide reduction catalyst 23, then feed-in takes place

Dependence on the nitrogen oxide content of the exhaust gas and the hydrogen loading of the SCR catalyst. Oxygen generated at the anode 52 of the electrolyzer is released into the ambient air. In a second embodiment of the device according to the invention, the installation in a motor vehicle is shown schematically in Fig. 2, the electrolyzer 50 is at its anode 52, however, also operated under pressure and the oxygen produced is stored in an oxygen pressure tank 70. From there, it can be supplied by opening an oxygen extraction valve 71 to the soot filter 22 so that it is fed into the exhaust line 20 upstream of the filter elements in the soot filter 22. This feed occurs in the regeneration mode of the soot filter to aid in the oxidation of the carbon black collected therein to carbon dioxide. Both in the first embodiment and in the second embodiment of the invention, the device 30 for recovering water from a gas alternatively or in addition to the connection to the exhaust line 20 of the

Motor vehicle have a connection to an air conditioner (not shown) of the motor vehicle to the pump 41 to be able to supply water, which is deposited on a condenser of the air conditioner.

Claims

claims

A device (30) for recovering water from a gas, wherein the

Device (30) is arranged to supply water to an electrolyzer (50) and wherein the electrolyzer (50) is arranged to supply hydrogen to at least one nitrogen oxide reduction catalyst (23).

2. Device (30) according to claim 1, characterized in that the at least one nitrogen oxide reduction catalyst (23) is an NSC catalyst and / or an S CR catalyst.

3. Device (30) according to claim 1 or 2, characterized in that it is connected to the exhaust line (20) of an internal combustion engine (10) such that its exhaust gas of the internal combustion engine (10) can be supplied.

4. Device (30) according to one of claims 1 to 3, characterized

characterized in that it is connected to an air conditioning system of a motor vehicle, that it can remove water from a condenser of the air conditioner.

5. Device (30) according to one of claims 1 to 4, characterized

characterized in that it comprises a reverse osmosis unit (42) arranged so that water exiting the apparatus (30) is conditioned in the reverse osmosis unit (42) before it is discharged

Electrolyzer (50) is supplied.

6. Device (30) according to one of claims 1 to 5, characterized

characterized in that the electrolyzer (50) is a PEM electrolyzer. Device (30) according to one of claims 1 to 6, characterized

characterized in that it comprises a hydrogen pressure tank (60) arranged to allow hydrogen leaving the electrolyzer (50) to be intermediately stored in the hydrogen pressure tank (60) before being supplied to the at least one nitrogen oxide reduction catalyst (23).

Device (30) according to one of claims 1 to 7, characterized

characterized in that the electrolyzer (50) is arranged to discharge oxygen generated in the electrolysis of water into the ambient air.

Device (30) according to one of claims 1 to 8, characterized

characterized in that the nitrogen oxide reduction catalyst (23) is arranged in an exhaust line (20), wherein a soot filter (22) in the

Exhaust line is arranged, wherein the electrolyzer (50) is arranged to supply the soot filter (22) oxygen.

Device (30) according to claim 9, characterized in that it comprises an oxygen pressure tank (70) arranged so that oxygen exiting the electrolyzer (50) in the

Oxygen pressure tank (70) is cacheable before he

Soot filter (22) is supplied.

Nitrogen oxide reduction process comprising the following steps:

Extraction of water from a gas,

Supplying the water to an electrolyzer (50), and

Supplying hydrogen from the electrolyzer (50) to at least one nitrogen oxide reduction catalyst (23).

A method according to claim 11, characterized in that the

Recovery of water by means of a device according to one of claims 1 to 10 takes place.

A computer program configured to perform each step of the method of claim 11 or 12.

14. Machine-readable storage medium on which a

Computer program according to claim 13 is stored.

15. Electronic control device, which is set up to a

Nitrogen oxide reduction by means of a method according to claim 11 or 12 perform.