KR102397622B1 - An apparatus and a method for purifying exhaust gas from internal combustion engine - Google Patents

Abstract

The apparatus and method according to the present invention effectively recover thermal energy from exhaust gas discharged from an internal combustion engine to generate a hydrogen-rich gas from a mixed aqueous solution of methanol and dimethyl ether, and supply the hydrogen-rich gas to an engine and/or an after-treatment device. By supplying it, it is possible to reduce the emission of pollutants emitted from various vehicles equipped with an internal combustion engine, for example, carbon monoxide, nitrogen oxide (NOx), particulate matters, etc., and at the same time improve the fuel efficiency of the vehicle. , since it can be implemented as a device that can be simply mounted on a vehicle, it is more efficient and economical than the prior art.

Description

An apparatus and a method for purifying exhaust gas from internal combustion engine

The present invention relates to pollutants emitted from various transportation means or various mechanical devices using an internal combustion engine (ICE), for example, carbon monoxide, nitrogen oxides (NOx), unburned hydrocarbons, particulate matters. The present invention relates to an apparatus and method capable of improving fuel efficiency of a vehicle while reducing emissions of the vehicle.

In general, an internal combustion engine refers to a heat engine that generates power by generating combustion gas by detonating and burning fuel in a cylinder and converting it into mechanical energy.

Various products of incomplete combustion occurring inside the cylinder of an internal combustion engine, for example, carbon monoxide (CO), unburned hydrocarbons (HCs, hydrocarbons), and particulate matters (PM) are nitrogen oxides ( It is emitted as exhaust gas together with NOx) and is a major cause of environmental pollution.

In the case of a vehicle, which is a representative example of using an internal combustion engine, electric hybrid vehicles or electric charging vehicles have appeared in order to improve fuel efficiency and reduce pollutant emissions, reducing dependence on internal combustion engines. For this, a lot of effort is required in terms of economic feasibility, stability, convenience, and hinterland facilities.

For the above reasons, efforts to primarily increase the fuel efficiency of the vehicle through lightening the vehicle, improving the thermal efficiency of the internal combustion engine, and optimizing the driving pattern, and secondarily, to improve the performance of the exhaust gas after-treatment system, are continuing. come.

As part of the above efforts, methods for increasing the combustion efficiency of an internal combustion engine and reducing the emission of pollutants by mixing and burning hydrogen or hydrogen-enriched gas with fossil fuels have been continuously studied. By mixing and burning, it is possible to reduce the consumption of fossil fuels and increase the ratio of hydrogen to carbon, which seems to have the effect of reducing the emission of products of incomplete combustion or greenhouse gases. The following patent documents disclose methods for achieving this effect.

Korean Patent Application Laid-Open No. 2005-0127363 discloses a method for controlling the emission of nitrogen oxides (NOx) and unburned hydrocarbons according to the amount of hydrogen mixed in a natural gas engine.

Korean Patent Application Laid-Open No. 2006-0051733 discloses a method for reducing pollutants by re-combusting hydrogen generated by reforming hydrocarbons in some cylinders of a separate internal combustion engine with hydrocarbons.

Korean Patent Application Laid-Open No. 2017-0008237 discloses a method of operating a gasoline engine vehicle with hydrogen generated by reforming an ethanol-water mixture in a cylinder.

Korea Patent No. 0782134 uses LPG, LNG, gasoline, diesel, biodiesel, or oxygen-containing hydrocarbon DME as fuel and supplies air as an oxidizing agent to generate heat, or at the same time, combustion / combustion of hydrocarbons that can supply reducing gas Disclosed is a device for supplying fuel and air for a reforming reactor.

Korean Utility Model Publication No. 1998-0037526 discloses an engine capable of reducing the amount of unburned hydrocarbons contained in exhaust gas by injecting hydrogen into a combustion chamber during cold start when the engine is started in a cooled state.

According to the above patent documents, the expected effect of using hydrogen or hydrogen-enriched gas is obvious, but in the method of providing hydrogen, a separate hydrogen storage container is required, water is electrolyzed, or fuel is used in an internal combustion engine. In order to reform from the inside or the outside, there are problems in that excessive installation of an apparatus is required, thermal efficiency is lowered, or fuel penalty is generated. However, the above patent documents do not disclose specific efforts to solve this problem, and also do not specify a solution to the problem of increasing the emission of nitrogen oxides (NOx).

Meanwhile, as another method of reducing pollutants emitted from vehicles, efforts have been made to improve the performance of the after-treatment device by mixing hydrogen or hydrogen-rich gas into the exhaust gas flow.

As a conventional after-treatment device to reduce pollutants emitted from exhaust gas, a catalytic converter including three-way catalysts (TWC) is used for vehicles equipped with natural gas, LPG, and gasoline engines. is using

A vehicle equipped with a diesel engine consists of a combination of an exhaust gas recycling (EGR) system, diesel oxidation catalysts (DOC), and a diesel particulate filter (DPF) to meet emission standards In order to satisfy more stringent emission standards, a new combination is formed by adding a lean NOx trap (LNT) or selective catalytic reduction (SCR) device to the method consisting of the above combination. is using it.

Methods for reducing the emission of pollutants through the post-treatment device using hydrogen or hydrogen-enriched gas are disclosed in the following patent documents.

US Patent Publication No. 2005-0274104 discloses a method of regenerating a DPF by plasma reforming fossil fuel to generate a hydrogen-rich gas and injecting the hydrogen-rich gas.

US Patent No. 6,976,353 discloses a method of using some of reformate generated by plasma reforming of fossil fuels in a post-treatment device.

U.S. Patent No. 7,163,668 discloses that after partial oxidation of fossil fuels, reformate, which is a gas rich in hydrogen, is obtained, and reformate is converted back to water gas to produce hydrogen, followed by hydrogen selective reduction (H2-SCR, hydrogen selective catalytic). reduction) A method of injecting into a catalyst device and using it as a reducing agent for nitrogen oxides (NOx) is disclosed.

US Patent No. 5,845,485 discloses a method of effectively removing pollutants contained in exhaust gas by generating hydrogen by electrolysis of water and injecting the generated hydrogen into a post-treatment device including a three-way catalyst.

The above patent documents disclose the performance improvement effect and method of an aftertreatment device using hydrogen or hydrogen-rich gas, but the problems similar to the case of the mixed combustion described above are still not resolved, and the prior art fuel direct A method for clearly improving the problem of fuel penalty caused by the direct fuel injection (DFI) method has not been disclosed.

Korean Patent Publication No. 2005-0127363 Korean Patent Publication No. 2006-0051733 Korean Patent Publication No. 2017-0008237 Korean Patent No. 0782134 Korea Public Utility Model No. 1998-0037526 US Patent Publication No. 2005-0274104 US Patent No. 6,976,353 US Patent No. 7,163,668 US Patent No. 5,845,485

The present inventors reduce the emission of pollutants emitted from various vehicles equipped with an internal combustion engine (ICE), for example, carbon monoxide, nitrogen oxides (NOx), particulate matters, etc. Research efforts were made to develop a method to improve the fuel efficiency of

As a result, thermal energy is effectively recovered from the exhaust gas discharged from the internal combustion engine to generate hydrogen-rich gas from a mixed aqueous solution of methanol and dimethyl ether (DME), and then the hydrogen-rich gas is supplied to the engine to provide fossil fuels. By reducing the use of fossil fuels by mixing and burning with fuel, the emission of various pollutants and carbon dioxide can be reduced primarily, or by injecting the hydrogen-enriched gas into a specific location of the exhaust gas post-processing device to reduce the pollutants contained in the exhaust gas. A method was devised to secondarily reduce the amount.

In addition, since the method according to the present invention can be implemented as a device that can be simply mounted on a vehicle, it is more efficient and economical than the prior art.

The present invention provides the following preferred means to solve the above problems, but is not limited thereto, and various modifications and the like are possible from the point of view of those skilled in the art.

An exhaust gas purification method of an internal combustion engine according to the present invention comprises the steps of: (a) vaporizing a mixed aqueous solution of methanol and dimethyl ether into a methanol-dimethyl ether-steam mixed gas using heat recovered from the exhaust gas; (b) steam reforming the methanol-steam mixed gas using heat recovered from the exhaust gas to generate a hydrogen-rich gas; (c) dispensing a hydrogen-enriched gas; and (d-1) introducing the distributed hydrogen-enriched gas to the internal combustion engine; or (d-2) introducing the distributed hydrogen-enriched gas to the aftertreatment unit; or (d-3) simultaneously introducing the distributed hydrogen-enriched gas to the internal combustion engine and the aftertreatment device.

The concentration of methanol in the mixed aqueous solution of methanol and dimethyl ether in step (a) is preferably 35 wt% to 70 wt%.

The concentration of dimethyl ether in the mixed aqueous solution of methanol and dimethyl ether in step (a) is preferably 3% by weight or less.

The supply amount of the mixed aqueous solution of methanol and dimethyl ether in step (a) is preferably 0.051 g or less per 1 g of fossil fuel in consideration of the supply amount of hydrogen-rich gas in step (d-1) or (d-3) Do.

The supply amount of the mixed aqueous solution of methanol and dimethyl ether in step (a) is that the amount of dimethyl ether is 3.7 mg or less per 1 g of fossil fuel in consideration of the supply amount of the hydrogen-rich gas in step (d-1) or (d-3) desirable.

The location of the heat recovery in step (a) is preferably a point where the temperature of the exhaust gas is 100 ^o C to 550 ^o C.

It is preferable that the steam reforming reaction of step (b) is carried out in a reforming reaction unit composed of a preheater and a reactor that are integrally fabricated with a heat exchanger.

The reforming reaction unit of step (b) is preferably located at a point where the temperature of the exhaust gas is 180 ^o C to 400 ^o C.

The reforming reaction part of step (b) preferably includes a hydration reaction of dimethyl ether.

It is preferable that step (c) proceeds in a distributor configured as a manifold type.

Preferably, the hydrogen-rich gas distributed in step (d-1) or (d-3) is mixed with an exhaust gas recirculation flow or an intake air flow and supplied to the combustion chamber.

Preferably, the hydrogen-rich gas of step (d-2) or (d-3) acts as a reducing agent for reducing nitrogen oxides to nitrogen in the post-treatment device.

Preferably, the hydrogen-rich gas of step (d-2) or (d-3) is combusted in an aftertreatment device to increase the temperature of the exhaust gas stream.

An exhaust gas purification apparatus for an internal combustion engine according to the present invention comprises: a vaporizer for vaporizing a mixed aqueous solution of methanol and dimethyl ether into a methanol-dimethyl ether-steam mixed gas using heat recovered from the exhaust gas; a reforming reaction unit for generating hydrogen-rich gas by steam reforming the methanol-dimethyl ether-steam mixed gas using the heat recovered from the exhaust gas; and a distributor for distributing the hydrogen-enriched gas for introduction to the internal combustion engine or the aftertreatment device or both; It is preferable to include

It is preferable that the vaporization part is a point where the temperature of the exhaust gas is 100 ^o C to 550 ^o C.

It is preferable that the reforming reaction unit is composed of a preheater and a reactor manufactured as an integrated heat exchanger.

Preferably, the reforming reaction unit is located at a point where the temperature of the exhaust gas is 180 ^o C to 400 ^o C.

Preferably, the distributor is of a manifold type.

Preferably, it further comprises means for mixing the hydrogen-enriched gas distributed in the distributor with the exhaust gas recirculation stream or the intake air stream and supplying it to the combustion chamber.

Preferably, the distributed hydrogen-rich gas is supplied to act as a reducing agent for reducing nitrogen oxides to nitrogen in the post-treatment device.

Preferably, the distributed hydrogen-rich gas is combusted in an after-treatment device to increase the temperature of the exhaust gas stream.

The apparatus and method according to the present invention reduce the emission of pollutants emitted from various vehicles equipped with an internal combustion engine (ICE), for example, carbon monoxide, nitrogen oxides (NOx), particulate matters, etc. It is possible to reduce and improve the fuel efficiency of the vehicle, and since it can be implemented as a device that can be simply mounted on a vehicle, it is more efficient and economical than the prior art.

1 schematically shows a device according to the invention;
2a and 2b show the configuration of the reforming reaction unit of the apparatus according to the present invention by way of example.
3A to 3D illustrate the configuration of the dispenser of the device according to the present invention by way of example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

In describing the present embodiments, the same names and reference numerals are used for the same components, and thus overlapping additional descriptions are omitted below. In the drawings referenced below, no scale ratio applies.

An exhaust gas purification method for an internal combustion engine according to the present invention comprises the steps of: (a) vaporizing a mixed aqueous solution of methanol and dimethyl ether into a methanol-dimethyl ether-steam mixed gas using heat recovered from the exhaust gas; (b) steam reforming the methanol-dimethyl ether-steam mixed gas using the heat recovered from the exhaust gas to generate a hydrogen-rich gas; (c) dispensing a hydrogen-enriched gas; and (d-1) introducing the distributed hydrogen-enriched gas to the internal combustion engine; or (d-2) introducing the distributed hydrogen-enriched gas to the aftertreatment unit; or (d-3) simultaneously introducing the distributed hydrogen-enriched gas to the internal combustion engine and the aftertreatment device.

Specifically, in step (a) of the present invention, thermal energy is recovered from the high-temperature exhaust gas discharged from the internal combustion engine, and a mixed aqueous solution of methanol and dimethyl ether is vaporized using the recovered thermal energy to vaporize methanol-dimethyl ether-water vapor. This is a step for generating a mixed gas.

1, the mixed aqueous solution of methanol and dimethyl ether in FIG. 1 is vaporized using a variable flow pump 131 from the storage tank 102 of the mixed aqueous solution of methanol and dimethyl ether in FIG. It is supplied to the unit 121 .

The concentration of methanol in the mixed aqueous solution of methanol and dimethyl ether in step (a) is preferably 35 wt% to 70 wt%. When the concentration of methanol is 35% or less, too much thermal energy is required to vaporize water to generate water vapor, so that the amount of heat of the hydrogen-rich gas produced through the reforming reaction of step (b) is lowered, thereby improving the thermal efficiency of the internal combustion engine I don't see much improvement in fuel efficiency. In addition, along with the problem that the capacity of the storage tank of the mixed aqueous solution of methanol and dimethyl ether becomes excessively large, the freezing point of the mixed aqueous solution of methanol and dimethyl ether is high, and in order to use it in the winter season, a storage container with heat treatment or a heating device is required. , there is also a problem that a separate heating device is required, such as a supply pump. On the other hand, when the concentration of methanol is 70% or more, a significant amount of unconverted methanol is generated in the reforming reaction step of step (b), so that methanol slip occurs in the post-treatment device of (d-2) or (d-3) or It may give an excessive load to the catalyst of the after-treatment unit.

The concentration of dimethyl ether in the mixed aqueous solution of methanol and dimethyl ether in step (a) is preferably 0 wt% to 3 wt%. Compared to methanol, dimethyl ether has high energy per unit weight and a large amount of hydrogen that can be obtained through reforming reaction per unit molecule. Therefore, the higher the concentration of dimethyl ether in the mixed aqueous solution of methanol and dimethyl ether, the better.

However, since the equilibrium fraction of dimethyl ether in the mixed aqueous solution of methanol and dimethyl ether is very sensitive to temperature, when the concentration of dimethyl ether is too high, the stability of the mixed aqueous solution of methanol and dimethyl ether may be lowered by the influence of external temperature. . Therefore, in order to stably maintain the equilibrium fraction of dimethyl ether in the mixed aqueous solution of methanol and dimethyl ether at the general atmospheric temperature and pressure, the concentration of dimethyl ether is preferably limited to 3% by weight or less.

The supply amount of the mixed aqueous solution of methanol and dimethyl ether in step (a) is 0 g to 0.051 g per 1 g of fossil fuel in consideration of the supply amount of hydrogen-rich gas in step (d-1) or (d-3) it is preferable In addition, it is preferable that the amount of dimethyl ether is 0 mg to 3.7 mg per 1 g of fossil fuel. Details of the supply amount of the mixed aqueous solution of methanol and dimethyl ether will be described later in step (d-1).

The heat recovery position of step (a) is preferably performed through a vaporization unit installed at a point where the temperature of the exhaust gas is 100 ^o C to 550 ^o C. Details of the vaporization unit will be described later.

Step (b) of the present invention is a step of generating a hydrogen-rich gas by reforming the methanol-dimethyl ether-water vapor mixed gas generated in step (a). The hydrogen-enriched gas includes unconverted water vapor, unconverted methanol, unconverted dimethyl ether, and reaction products hydrogen and carbon dioxide.

The principle of the steam reforming reaction of methanol is shown in [Reaction Equation 1] below.

[Scheme 1] CH ₃ OH(g) + H ₂ O(g) → 3H ₂ (g)+ CO ₂ (g) ΔH _O = +49.5KJ/mol

In the methanol-dimethyl ether-water vapor mixed gas, dimethyl ether is converted to methanol by a hydration reaction and then reformed or directly reformed.

The principle of the hydration reaction of dimethyl ether is shown in [Scheme 2] below.

[Scheme 2] CH ₃ OCH ₃ (g) + H _{2 O} (g) → 2CH ₃ OH(g) ΔHO = +21.5KJ/mol

The principle of the reforming reaction of dimethyl ether is shown in [Scheme 3] below.

[Scheme 3] CH ₃ OCH ₃ + 3H ₂ O → 6H ₂ + 2CO ₂ ΔH _O = +123KJ/mol

Referring to FIG. 1 in more detail, the methanol-dimethyl ether-steam mixed gas discharged through the outlet of the vaporization unit 121 of FIG. 1 is a reforming reaction unit 111 including a second heat exchange unit 122 . ) and is converted into hydrogen and carbon dioxide through steam reforming as shown in [Reaction Equation 1].

The conversion rate of methanol and dimethyl ether and the yield of hydrogen may vary depending on reaction parameters such as reaction temperature, reaction pressure, steam to methanol ratio or steam to dimethyl ether ratio.

If the reaction temperature is too low, it is difficult to sufficiently convert water vapor and methanol or dimethyl ether. If the reaction temperature is too high, catalyst deactivation may proceed quickly. Since there is an economic loss, the reaction temperature is suitable in the range of 180 °C to 400 °C. Therefore, the reforming reaction unit 111 of step (b) is preferably located at a point where the temperature of the exhaust gas is 180 ^o C to 400 ^o C.

The lower the reaction pressure, the better, but in order to maintain the pressure below atmospheric pressure, a separate vacuum generator is required, so from a practical point of view, the range of atmospheric pressure to 9 atmospheres (atm) or less is preferable.

The space velocity (GHSV) of the steam reforming reaction may be 100 to 20,000 hr ⁻¹ based on standard conditions (STP). However, if the space velocity is too high, the conversion rate is low, and if the space velocity is too low, the amount of catalyst used increases and the heat transfer area is increased. Since it becomes large, it is practically 500 to 5000 hr ^-1 between is preferable.

As the catalyst for the steam reforming reaction, a catalyst composed of CuO, ZnO and Al ₂ O ₃ may be used, but it contains at least one catalyst component, and contains Ce and/or La-based rare earth metals or Ni or Co-based catalysts. It is more effective to use a catalyst containing a transition metal or a noble metal of the Pt, Pd, Ir and Ru series.

Since the steam reforming reaction is an endothermic reaction, it is preferable to rapidly supply heat required for the reaction. The exhaust gas discharged from another outlet of the vaporization unit 121 of FIG. 1 supplies thermal energy Q required by the reforming reaction unit including the preheater and the reactor through the second heat exchange unit 122 . The second heat exchange unit may be manufactured integrally with the reactor in order to quickly supply thermal energy required for the reforming reaction and may include a heat transfer medium inside or outside, but the steam reforming reaction of step (b) is integrated with a heat exchanger. It is preferably carried out in the reforming reaction unit composed of the prepared preheater and reactor.

The steam reforming reaction may include the hydration reaction of dimethyl ether of [Scheme 2], and as a catalyst for the hydration reaction of dimethyl ether, metal oxides containing at least one component among Al, Si, W, and Zr, various zeolites, A solid acid catalyst such as an ion exchange resin can be used.

The solid acid catalyst for the hydration reaction of dimethyl ether may be independently disposed in front of the steam reforming reaction catalyst or may be used in combination with the steam reforming reaction catalyst.

The hydrogen-enriched gas generated by the [Reaction Equations 1] to [Reaction Equation 3] is discharged through the outlet of the reforming reaction unit to form the hydrogen-enriched gas 203 .

Step (c) of the present invention is a step of distributing the gas to supply the hydrogen-rich gas produced in step (b) to each device. The hydrogen-enriched gas produced in step (b) of the present invention may be supplied to the internal combustion engine, or to the aftertreatment device, or to the internal combustion engine and the aftertreatment device simultaneously. 1, the hydrogen-rich gas discharged from the outlet of the reforming reaction unit 111 of FIG. 1 has a flow direction determined in the distributor 112 of FIG. 1 to determine the engine injection unit 132, Alternatively, it is supplied to the post-treatment device 113 , or to the engine injection unit 132 and the post-treatment device 113 at the same time.

In order to distribute the hydrogen-rich gas and supply it to each device as described above, the inlet to which the hydrogen-rich gas is introduced, and signals from various sensors of the vehicle are received, interpreted, and transmitted from an electronic control unit (ECU) that calculates A manifold type distributor including a plurality of automatic on/off valves (eg, solenoid valves) controlled by receiving a signal from .

Steps (d-1) and (d-3) of circulating the hydrogen-rich gas generated in step (b) and introducing it into the engine 101 will be described in more detail with reference to FIG. 1 , the reforming reaction unit of FIG. 1 . The flow direction of the hydrogen-rich gas discharged from the outlet of 111 is determined in the distributor 112 of FIG. 1 , and the exhaust gas recirculation (EGR) flow 104 or intake air in the engine injection unit 132 is It is mixed with stream 104 and injected into the engine.

The hydrogen-enriched gas introduced into the internal combustion engine is exploded and combusted inside the cylinder together with the fossil fuel composed of hydrocarbons as shown in [Reaction Equations 4] to [Reaction Equation 6] below, and partially replaces the amount of heat in the fossil fuel. will improve fuel economy.

[Scheme 4] H ₂ (g) + 0.5O ₂ (g) → H ₂ O (g) ΔH _O = -241.8KJ/mol

[Reaction Equation 5] shows the combustion reaction and heat quantity of gasoline.

[Scheme 5] C ₈ H ₁₈ (g) + 12.5O ₂ (g) → 8CO ₂ (g) + 9H _{2 O} (g) ΔHO = -5,324.2KJ/mol

[Reaction Equation 6] shows the combustion reaction and heat quantity of diesel.

[Scheme 6] C ₁₆ H ₃₄ (g) + 24.5O ₂ (g) → 16CO ₂ (g) + 17H _{2 O} (g) ΔHO = -10,406.6KJ/mol

As the amount of hydrogen contained in the hydrogen-rich gas injected into the cylinder of an internal combustion engine increases, the amount of fossil fuel used to achieve the same fuel efficiency decreases, which further increases fuel efficiency and further decreases the amount of pollutants emitted per 1 km. . However, it is undesirable to generate an excessively large amount of hydrogen, because the thermal energy that can be recovered from the exhaust gas is finite, and the consumption of the aqueous methanol solution stored in the storage tank 102 of FIG. 1 is accelerated, so that the capacity of the storage tank This is because this may become excessively large or the filling cycle of the aqueous methanol solution may be too short.

Therefore, in the present invention, it is preferable that the supply amount of methanol, which is a raw material for hydrogen-rich gas, per 1 g of fossil fuel supplied to the engine is 0 g to 0.051 g, and the supply amount of dimethyl ether is preferably 0 mg to 3.7 mg. The supply amount of the hydrogen-rich gas is obtained by receiving signals from various sensors mounted on the vehicle, analyzing and calculating by an electronic control unit (ECU) of the vehicle, and preparing a mixed aqueous solution of methanol and dimethyl ether with a predetermined concentration as shown in FIG. It can be controlled by adjusting the supply amount of the aqueous methanol solution with a variable flow pump. The above-described range and method of adjusting the supply amount of the hydrogen-rich gas may be equally applied to step (d-2).

Step (d-2) or (d-3) of the present invention is a step of injecting the hydrogen-rich gas generated in step (b) into the exhaust gas post-treatment device 113, which will be described in more detail with reference to FIG. , the hydrogen-rich gas discharged from the outlet of the reforming reaction unit 111 of FIG. 1 is injected into the post-treatment device 113 by controlling the flow direction in the distributor 112 of FIG. 1 .

In FIG. 1 , the positions of the vaporization unit 121 , the reforming unit 111 , the distributor 112 , and the post-treatment device 113 are not particularly limited, and their order may be changed according to the purpose. The hydrogen-enriched gas may be introduced into various combinations of after-treatment devices according to the type of the internal combustion engine or the target reduction rate of the pollutant source.

The hydrogen-enriched gas of step (d-2) or (d-3) preferably acts as a reducing agent for reducing nitrogen oxides to nitrogen in the post-treatment device, as shown in the following [Reaction Schemes 7a] to [Reaction Schemes 7c] .

[Scheme 7a] 2NO + 2H ₂ → N ₂ + 2H ₂ O

[Scheme 7b] 2NO ₂ + 4H ₂ → N ₂ + 4H ₂ O

[Scheme 7c] N ₂ O + H ₂ → N ₂ + H ₂ O

In addition, the hydrogen-enriched gas of step (d-2) or (d-3) is burned as in [Reaction Equation 4] in the post-treatment device to increase the temperature of the exhaust gas, so that the temperature of the catalytic reaction in each post-treatment device to enhance the reaction activity and promote the combustion of soot.

In the method according to the present invention, fuel efficiency loss that was inevitably accompanied in the conventional direct fuel injection (DFI) method in which a portion of fossil fuel is used for use as a reducing agent or to increase the temperature of exhaust gas by combustion (fuel penalty) can be solved.

On the other hand, the exhaust gas purification apparatus of an internal combustion engine according to the present invention includes: a vaporizer for vaporizing a mixed aqueous solution of methanol and dimethyl ether into a methanol-dimethyl ether-steam mixed gas using heat recovered from the exhaust gas; a reforming reaction unit for generating hydrogen-rich gas by steam reforming the methanol-dimethyl ether-steam mixed gas using the heat recovered from the exhaust gas; and a distributor for distributing the hydrogen-enriched gas for introduction to the internal combustion engine or the aftertreatment device or both; It is preferable to include

Matters overlapping with the description of the exhaust gas purification method of the internal combustion engine of the present invention will be omitted, and will be described in more detail with reference to FIG. 1 .

The vaporizer 121 may be configured as a shell-and-tube type or plate heat exchanger, but a vaporizer manufactured integrally with a pipe may be used to simplify the device and save installation space.

Described in more detail one example of the pipe-integrated vaporization part, the vaporization part may be located inside the cylindrical pipe or may be installed in the form of surrounding the exhaust gas discharge pipe outer wall. The vaporizing part is a tube, a coil wound around the tube, a container with an empty interior, and a heat transfer part designed to promote heat transfer, for example, various heat transfer pins or fins that can replace the effect of fins and are easy to process. The structure may be, for example, a container including a honeycomb made of a metal or ceramic material, a corrugated structure, a mesh, a foam, a mat, and the like.

On the other hand, the exhaust gas discharged from the internal combustion engine passes through a heat transfer unit installed inside the cylindrical pipe and transfers heat energy to the inside of the vaporization unit. The heat transfer part is a fin or a structure that can replace the effect of a fin and is easy to process and does not interfere with the smooth flow of exhaust gas, for example, a honeycomb made of metal or ceramic, a corrugated structure, mesh, foam, mat can be

The outside of the cylindrical pipe is covered with insulation to prevent loss of thermal energy.

The installation location of the vaporizer is preferably a point where the temperature of the exhaust gas is 100 ^o C to 550 ^o C.

A mixed aqueous solution of methanol and dimethyl ether is introduced into the inlet of the vaporization unit, vaporized into a mixed gas of methanol-dimethyl ether-water vapor, and then further heated and discharged through the outlet of the vaporization unit. The methanol-dimethyl ether-water vapor mixed gas flow out of the outlet of the vaporization unit 121 of FIG. 1 is introduced into the reforming reaction unit 111 including the second heat exchange unit 122 .

It is preferable that the reforming unit is composed of a preheater and a reactor manufactured as an integrated heat exchanger.

When the heat exchanger integrated reforming unit is described in more detail with reference to FIG. 2 , the exhaust gas 201 discharged from the internal combustion engine passes through the heat transfer unit 212 installed in the pipe 214 provided for the discharge of the exhaust gas, Thermal energy is transferred to the reforming reaction unit 211 .

The heat transfer unit 212 is a pin or a structure that can replace the effect of a pin and does not interfere with the exhaust gas flow and is easy to process, for example, a honeycomb made of a metal or ceramic material, a corrugated structure, It may be a mesh, foam, mat, or the like.

The outside of the exhaust gas pipe 214 is covered with a heat insulating material 213 to prevent loss of thermal energy.

The methanol-dimethyl ether-water vapor mixed gas 202 is introduced into the inlet of the reforming reaction unit 211, preheated to the reaction temperature in the preheater, and then introduced into the reactor filled with the catalyst. The reforming reaction unit 211 including the preheater and the reactor may be located inside the pipe through which the exhaust gas flows as shown in FIG. 2A or outside the pipe as shown in FIG. 2B .

The preheater and the reactor are a tube, a coil wound around the tube, an empty vessel, a heat transfer part designed to promote heat transfer, for example, various heat transfer pins or fins that can replace the effect of the processing This easy structure may be, for example, a honeycomb made of a metal or ceramic material, a corrugated structure, a mesh, a foam, or a container including a mat.

The steam reforming catalyst in the reactor may be powder or various molded articles, and may be in a form coated on a metal or ceramic support, for example, a honeycomb, a corrugated structure, a mesh, a foam, or a mat.

The distributor 112 is preferably of a manifold type, and will be described in more detail with reference to FIG. 3 . 3A to 3D exemplarily show a configuration method of a distributor installed to control the supply of hydrogen-enriched gas. 3A to 3D, the hydrogen-rich gas 311 generated in the reforming reaction unit is introduced into the internal combustion engine injection units 321 and 322 and/or the unit post-treatment unit injection units 3301 to 3311. An automatic on/off valve 341 is provided to connect or block the flow of hydrogen-rich gas introduced into the internal combustion engine injection unit, and connect the flow of hydrogen-rich gas injected into each unit post-processing device injection unit 3301 to 3311. Automatic opening/closing valves 3401 to 3411 for shutting off or on are also provided. Furthermore, when the hydrogen-rich gas is to be discharged simultaneously through two or more outlets, a flow regulator may be additionally used or the automatic on/off valve may be replaced with a proportional control type valve having a flow rate control function.

3A to 3D illustrating the present invention by way of example are described in detail. In the case of a gasoline engine, FIG. 3A is an internal combustion engine injection unit 321 into which a hydrogen-enriched gas 311 is injected into the gasoline engine, and a three-way A unit post-treatment unit injection unit 3301 for injecting hydrogen-enriched gas to a catalytic converter including a catalyst (TWC, three way catalysts) is illustrated by way of example.

3B to 3D illustrate the case of a diesel engine by way of example, and FIG. 3B is an internal combustion engine injection unit 322 into which hydrogen-rich gas 311 is injected into the diesel engine, and a diesel oxidation catalyst (DOC, diesel, respectively). Illustrative unit post-treatment unit injection units 3302, 3303, 3304 for injecting hydrogen-rich gas into oxidation catalysts) devices, lean NOx traps (LNTs) and diesel particulate filters (DPFs) is shown as

3C shows an internal combustion engine injection unit 322 into which a hydrogen-rich gas 311 is injected into a diesel engine, a diesel oxidation catalyst (DOC) device, a diesel particulate filter (DPF), and a selective catalyst, respectively. The unit post-processing unit injection units 3305, 3306, 3307, and 3308 for injecting hydrogen-rich gas into a reduction (SCR) device and a Clean-up Catalysts device are exemplarily shown. .

3D shows an internal combustion engine injection unit 322 into which a hydrogen-rich gas 311 is injected into a diesel engine, a diesel oxidation catalyst (DOC) device, a diesel particulate filter (DPF) and a hydrogen selective filter, respectively. The unit post-processing unit injection units 3309 , 3310 , and 3311 for injecting a hydrogen-rich gas into a catalytic reduction (H ₂ -SCR, hydrogen selective catalytic reduction) apparatus are exemplarily shown.

3B to 3D do not limit the order of configuration of the post-treatment device, and by changing the order or combination of each device according to the type of catalyst used in each post-treatment device, reduction performance of the device, reduction rate target, etc. can be used The catalyst used in each device may use a catalyst having a chemical composition and form well known in the art.

It is preferable to further include a means for mixing the hydrogen-rich gas distributed in the distributor 112 with the exhaust gas recirculation flow or the intake air flow 104 and supplying the mixture to the combustion chamber, that is, the engine injection unit 132 .

The position of the engine injection unit 132 may be provided at an appropriate position from the branching point of exhaust gas provided for exhaust gas recirculation to the engine inlet including the EGR mixer, and if injected before the EGR mixer, separate for mixing It is sufficient to inject hydrogen-enriched gas into the recirculation stream of the exhaust gas without the need to install a device in the exhaust gas. At this time, since the hydrogen spontaneous ignition temperature in the air is 585 ^o C, the explosive concentration range is 13 to 59%, the position of the mixer or the engine injection part 132 of the hydrogen-rich gas is a point where the temperature of the exhaust gas is 585 ^o C or less. . As another method, the hydrogen-enriched gas engine injection unit 132 may be installed at an appropriate position in the intake air flow from the air intake port of the internal combustion engine to the EGR mixer.

101: engine (internal combustion engine)
102: a mixed aqueous solution storage tank of methanol and dimethyl ether
103: exhaust port
104: intake air flow
111: reforming reaction unit 112: distributor
113: post-processing device
121: vaporization unit 122: second heat exchange unit
131: variable flow pump 132: engine injection unit
201: exhaust gas 202: methanol-dimethyl ether-water vapor mixture
203: hydrogen-enriched gas
211: reforming reaction unit 212: heat transfer unit
213: insulation 214: piping
311: hydrogen-enriched gas 321, 322: internal combustion engine injection unit
341, 3401 to 3411: automatic on-off valve
3301 ~ 3311: unit post-processing unit injection unit

Claims (21)

(a) vaporizing a mixed aqueous solution of methanol and dimethyl ether into a methanol-dimethyl ether-steam mixed gas using the heat recovered from the exhaust gas;
(b) steam reforming the methanol-dimethyl ether-steam mixed gas using the heat recovered from the exhaust gas to generate a hydrogen-rich gas;
(c) dispensing a hydrogen-enriched gas; and
(d-1) introducing the distributed hydrogen-enriched gas to the internal combustion engine; or (d-2) introducing the distributed hydrogen-enriched gas to the aftertreatment unit; or (d-3) simultaneously introducing the distributed hydrogen-enriched gas to the internal combustion engine and the aftertreatment device;
Exhaust gas purification method of an internal combustion engine comprising a. The method according to claim 1, wherein the concentration of methanol in the mixed aqueous solution of methanol and dimethyl ether in step (a) is 35 wt% to 70 wt%. The method according to claim 1, wherein the concentration of dimethyl ether in the mixed aqueous solution of methanol and dimethyl ether in step (a) is 3 wt% or less. According to claim 1, wherein the supply amount of the mixed aqueous solution of methanol and dimethyl ether in step (a) is the amount of methanol to the internal combustion engine in consideration of the supply amount of the hydrogen-rich gas in step (d-1) or (d-3) A method of purifying the exhaust gas of an internal combustion engine that is less than 0.051 g per 1 g of supplied fossil fuel. The internal combustion engine according to claim 1, wherein the supply amount of the mixed aqueous solution of methanol and dimethyl ether in step (a) is adjusted in consideration of the supply amount of the hydrogen-rich gas in step (d-1) or (d-3). A method of purifying exhaust gas from internal combustion engines with an amount of less than 3.7mg per 1g of fossil fuel supplied to the The exhaust gas purification method of an internal combustion engine according to claim 1, wherein the location of heat recovery in step (a) is a point where the temperature of the exhaust gas is 100 ^o C to 550 ^o C. The exhaust gas purification method of an internal combustion engine according to claim 1, wherein the steam reforming reaction of step (b) is performed in a reforming reaction unit composed of a preheater and a reactor integrated with a heat exchanger. The exhaust gas purification method of an internal combustion engine according to claim 7, wherein the reforming reaction unit in step (b) is located at a point where the temperature of the exhaust gas is 180 ^° C to 400 ^° C. The method according to claim 7, wherein the reforming reaction part of step (b) comprises a hydration reaction of dimethyl ether. The exhaust gas purification method of an internal combustion engine according to claim 1, wherein the step (c) is performed in a distributor configured as a manifold type. The exhaust gas purification method of an internal combustion engine according to claim 1, wherein the hydrogen-rich gas distributed in step (d-1) or (d-3) is mixed with an exhaust gas recirculation flow or an intake air flow and supplied to the combustion chamber. The exhaust gas purification method of an internal combustion engine according to claim 1, wherein the hydrogen-rich gas in step (d-2) or (d-3) acts as a reducing agent for reducing nitrogen oxide to nitrogen in the after-treatment device. The exhaust gas purification method of an internal combustion engine according to claim 1, wherein the hydrogen-rich gas in step (d-2) or (d-3) is burned in an aftertreatment device to increase the temperature of the exhaust gas stream. a vaporizer for vaporizing a mixed aqueous solution of methanol and dimethyl ether into a methanol-dimethyl ether-water vapor mixed gas using heat recovered from the exhaust gas;
a reforming reaction unit for generating hydrogen-rich gas by steam reforming the methanol-dimethyl ether-steam mixed gas using the heat recovered from the exhaust gas; and
a distributor for distributing the hydrogen-enriched gas for introduction into the internal combustion engine or the aftertreatment unit or both;
Exhaust gas purification device of an internal combustion engine comprising a. 15. The exhaust gas purification apparatus of an internal combustion engine according to claim 14, wherein the vaporization part is at a point where the temperature of the exhaust gas is 100 ^o C to 550 ^o C. 15. The exhaust gas purification apparatus of an internal combustion engine according to claim 14, wherein the reforming reaction unit includes a preheater and a reactor that are integrally manufactured with a heat exchanger. 15. The exhaust gas purification apparatus of an internal combustion engine according to claim 14, wherein the reforming reaction unit is located at a point where the temperature of the exhaust gas is 180 ^o C to 400 ^o C. 15. The exhaust gas purification apparatus of an internal combustion engine according to claim 14, wherein the distributor is of a manifold type. 15. The apparatus according to claim 14, further comprising means for mixing the hydrogen-rich gas distributed in the distributor with the exhaust gas recirculation flow or the intake air flow and supplying the mixture to the combustion chamber. 15. The exhaust gas purification apparatus of an internal combustion engine according to claim 14, wherein the distributed hydrogen-rich gas is supplied to act as a reducing agent for reducing nitrogen oxides to nitrogen in the after-treatment apparatus. 15. The exhaust gas purification apparatus of an internal combustion engine according to claim 14, wherein the distributed hydrogen-rich gas is burned in an after-treatment device to increase the temperature of the exhaust gas flow.

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