DE102014005244A1 - Exhaust after-treatment system and exhaust aftertreatment process - Google Patents

Abstract

An exhaust gas aftertreatment system (2) for an internal combustion engine, comprising means (3) arranged downstream of an internal combustion engine (3) for introducing calcium-containing and / or sodium-containing powder into an exhaust gas stream, and a separator (4) arranged downstream of said device (3) a granulated mobile bed reactor or fluidized bed reactor.

Description

The invention relates to an exhaust aftertreatment system. Furthermore, the invention relates to a method for exhaust aftertreatment.

In combustion processes in stationary internal combustion engines, which are used for example in power plants, as well as combustion processes in non-stationary internal combustion engines, which are used for example on ships, arise sulfur oxides, such as SO ₂ and SO ₃ , these sulfur oxides are typically sulfur-containing, fossil fuels, such as coal, hard coal, lignite, oil or heavy fuel. Therefore, such internal combustion engines exhaust treatment systems are assigned, which serve in particular the desulfurization of the engine leaving the exhaust gas.

For the desulfurization of the exhaust gas absorptive methods are known from the prior art primarily as absorbent primarily fire limestone (CaO) or hydrated lime (Ca (OH) ₂ ) or calcium carbonate (CaCO ₃ ) or NaHCO ₃ + Na ₂ CO ₃ use. In this case, dust from calcium sulfate (CaSO ₄ ) is formed, wherein to remove the calcium sulfate dust from the exhaust downstream of the desulfurization filter devices must be used.

From the DE 36 03 365 C2 is a method and an exhaust aftertreatment system for the treatment of nitrogen oxides and dust-containing exhaust gas is known.

On this basis, the present invention has the object to provide a novel exhaust aftertreatment system and a novel method for exhaust aftertreatment.

This object is achieved by an exhaust aftertreatment system according to claim 1.

The exhaust aftertreatment system according to the invention for an internal combustion engine has a device arranged downstream of the internal combustion engine for introducing calcium-containing and / or sodium-containing powder into an exhaust gas flow, and a separator arranged downstream of this device in the form of a granular-containing moving bed reactor or fluidized bed reactor. The invention proposes an exhaust aftertreatment system which enables effective desulfurization of the exhaust gas. In the desulfurization resulting calcium sulfate powder and / or sodium sulfate powder can be effectively separated from the exhaust gas by means of the separator.

According to an advantageous development, the grain size of the calcium-containing and / or sodium-containing powder introduced via the device into the exhaust gas stream, whose calcium and / or sodium have at least the oxidation state +1, is less than 1 mm, preferably less than 0.5 mm preferably less than 0.25 mm, wherein the calcium-containing and / or sodium-containing powder preferably comprises CaO and / or Ca (OH) ₂ and / or CaCO ₃ and / or NaHCO ₃ and / or Na ₂ CO ₃ . Hereby, a particularly advantageous desulfurization of the exhaust gas is possible. The relatively small particle size of the introduced into the exhaust, calcium-containing and / or sodium-containing powder promotes effective conversion of sulfur oxides to calcium sulfate and / or sodium sulfate. The adsorbent-containing, calcium-containing and / or sodium-containing powder having the relatively small grain size provides a large surface area for reacting the adsorbent with the sulfur oxides.

According to an advantageous development, the grain size of the granules in the moving bed reactor or fluidized bed reactor is more than 2 mm, preferably more than 3 mm, more preferably more than 4 mm, wherein the granules are preferably calcium or sodium or magnesium-containing and CaO and / or Ca (OH) ₂ and / or CaCO ₃ and / or Na ₂ CO ₃ .

Furthermore, corderite, silicon carbide, granite, metal balls (stainless steel) or Al ₂ O ₃ can be used.

The calcium sulfate powder and / or sodium sulfate powder formed in the reaction of the adsorbent with the sulfur oxides can effectively be discharged via the granules from the downstream moving bed reactor or fluidized bed reactor together with the granules thereof.

Then, when calcium granules are used as granules, the exhaust aftertreatment according to the invention can be further improved in the exhaust aftertreatment system according to the invention.

As a result of the selected grain size of the then calcium-containing granules can be ensured that the granules do not react to the center with sulfur oxides and therefore at least in the core consists of unreacted components, which are then surrounded by a shell of calcium sulfate. After discharge of the granules from the moving bed reactor or fluidized bed reactor, the calcium sulfate shell can then be separated from the core of the granules to continue to use the granule core.

According to a further advantageous development, an oxidation catalyst for SO ₂ oxidation is arranged downstream of the internal combustion engine and upstream of the device for introducing the calcium-containing and / or sodium-containing powder into the exhaust gas stream. The use of the oxidation catalyst for the oxidation of SO ₂ in SO ₃ , the desulfurization of the exhaust gas can be further improved because SO ₃ reacts faster with the used as adsorbent, calcium-containing and / or sodium-containing powder as SO ₂ .

In an exhaust-charged internal combustion engine, the oxidation catalyst is positioned upstream of a turbine of an exhaust gas turbocharger, wherein the means for introducing the calcium-containing and / or sodium-containing powder is positioned downstream of the oxidation catalyst. Due to the relatively high temperatures and pressures prevailing upstream of the turbine, the oxidation of SO ₂ in SO ₃ in the oxidation catalyst is favored.

According to a further advantageous development, the exhaust aftertreatment system comprises a device for introducing NH ₃ (urea) or gaseous NH ₃ into the exhaust gas, which is arranged downstream of the oxidation catalytic converter. As a result, the desulfurization of the exhaust gas can be further improved.

The inventive method for exhaust aftertreatment is defined in claim 15.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings.

Showing:

1 a block diagram of a first exhaust aftertreatment system according to the invention;

2 a block diagram of a second exhaust aftertreatment system according to the invention;

3 a block diagram of a third exhaust aftertreatment system according to the invention; and

4 a block diagram of a fourth exhaust aftertreatment system according to the invention.

The present invention relates to an exhaust aftertreatment system for an internal combustion engine, such as for a stationary internal combustion engine in a power plant or for coming on a ship used, non-stationary internal combustion engine.

1 shows a first embodiment of an internal combustion engine 1 downstream exhaust aftertreatment system 2 , wherein the exhaust aftertreatment system according to the invention 2 An institution 3 for introducing calcium-containing and / or sodium-containing powder into the internal combustion engine 1 leaving exhaust gas, so therefore the device 3 for introducing the calcium-containing and / or sodium-containing powder into the exhaust gas downstream of the internal combustion engine 1 is arranged.

In addition, the exhaust aftertreatment system according to the invention comprises 2 at least one downstream of the device 3 for introducing the calcium-containing and / or sodium-containing powder arranged separator 4 , where it is at the separator 4 is a granulated moving bed reactor or fluidized bed reactor.

The device 3 the exhaust aftertreatment system according to the invention 2 introducing the calcium-containing and / or sodium-containing powder into the exhaust gas of the internal combustion engine 1 is calcium-containing and / or sodium-containing powder having a particle size of less than 1 mm, preferably less than 0.5 mm, more preferably less than 0.25 mm, in the exhaust gas, wherein the calcium and / or sodium of the calcium-containing and / or sodium-containing powder has at least the oxidation state +1. Preferably, the calcium-containing and / or sodium-containing powder comprises CaO and / or Ca (OH) ₂ and / or CaCO ₃ and / or NaHCO ₃ and / or Na ₂ CO ₃ .

The device 3 For example, the calcium-containing and / or sodium-containing powder can be introduced either dry as an aerosol with air as the carrier gas or wet as an emulsion with water as a solvent in the exhaust gas stream.

The use of such calcium-containing and / or sodium-containing powder as adsorbent and the above incorporation thereof via the device 3 in the exhaust gas ensures a large surface area for the reaction of the calcium-containing and / or sodium-containing powder with in the exhaust gas of the internal combustion engine 1 contained sulfur oxides, namely with SO ₂ and SO ₃ , so that the sulfur oxides can be effectively converted into calcium sulfate CaSO ₄ and / or sodium sulfate Na ₂ SO ₄ . The reaction of the calcium-containing and / or sodium-containing powder with SO ₂ and SO ₃ is typically carried out according to the following reaction equations, namely for Ca (OH) ₂ according to the following reaction equations Ca (OH) ₂ + SO ₂ ↔ CaSO ₃ + H ₂ O Ca (OH) ₂ + SO ₂ + ½O ₂ ↔ CaSO ₄ + H ₂ O Ca (OH) ₂ + CO ₂ ↔ CaCO ₃ + H ₂ O Ca (OH) ₂ + SO ₃ ↔ CaCO ₄ + H ₂ O for CaCO ₃ according to the following reaction equations CaCO ₃ + SO ₂ - CaSO ₃ + CO ₂ CaCO ₃ + SO ₂ + ½O ₂ ↔ CaSO ₄ + CO ₂ CaCO ₃ + SO ₃ ↔ CaSO ₄ + CO ₂ for NaHCO ₃ according to the following reaction equations 2NaHCO ₃ → Na ₂ CO ₃ + CO ₂ + H ₂ O Na ₂ CO ₃ + SO ₂ + ½O ₂ → Na ₂ SO ₄ + CO ₂ Na ₂ CO ₃ + SO ₃ → Na ₂ SO ₄ + CO ₂ for MgO according to the following reaction equations MgO + SO ₂ + ½O ₂ → MgSO ₄ MgO + SO ₃ → MgSO ₄

By introducing the calcium-containing and / or sodium-containing powder into the exhaust gas via the device 3 upstream of the separator 4 is formed powdered calcium sulfate CaSO ₄ and / or sodium sulfate Na ₂ SO ₄ , which together with the granules of the trained as a moving bed reactor or fluidized bed reactor separator 4 can be discharged.

In the moving bed reactor or fluidized bed reactor and thus the separator 4 granules are used, which compared to the on the device 3 calcium-containing and / or sodium-containing powder introduced into the exhaust gas has a relatively large particle size, namely a particle size of more than 2 mm, preferably of more than 3 mm, particularly preferably of more than 4 mm.

As granules, an inert granulate can be used, which does not react with the sulfur oxides still present in the exhaust gas. However, particularly preferred is the use of a calcium, sodium, magnesium-containing granules comprising CaO and / or Ca (OH) ₂ and / or CaCO ₃ and / or Na ₂ CO and / or NaHCO ₃ and / or MgO.

Then, when calcium or sodium-containing granules are used as granules, sulfur oxides still present in the exhaust gas can react with the granules. Due to the above-defined, relatively large particle size of the granules, the sulfur dioxide does not react to the center, but in the core at least partially consists of not yet reacted with sulfur oxide components, which are then surrounded by a shell of calcium sulfate.

Designed as a moving bed reactor or fluidized bed reactor separator 4 Preferably, a means is associated to separate in the moving bed or fluid bed over the granules intercepted calcium or sodium sulfate, which is discharged together with the granules from the moving bed reactor or fluidized bed reactor, from the granules. This device may, for example, be a drum scraper, a drum screen or a mill. The freed of calcium sulfate granules can then be then returned to the moving bed reactor or fluidized bed reactor, so as to form a granular circuit and to use the granules more effectively. It is by the use of a mill, the granules remotely ground and added before the reactor, which one reaches a better degree of utilization. This is particularly advantageous if in the moving bed reactor or fluidized bed reactor, a calcium or sodium or magnesium-containing granules is used, which can react with the remaining sulfur in the exhaust gas. In this case, then the calcium sulfate or sodium sulfate or MgSO ₄ shell of the granules can be separated from not yet reacted with sulfur oxides core of the granules.

2 shows a development of the invention, in which the exhaust aftertreatment system according to the invention 2 additionally an oxidation catalyst 5 according to 2 downstream of the internal combustion engine 1 and upstream of the device 3 for introducing the calcium-containing and / or sodium-containing powder into the exhaust gas of the internal combustion engine is arranged.

In the oxidation catalyst 5 SO ₂ reacts to SO ₃ according to the following reaction equation 2SO ₃ + O ₂ → 2SO ₂

The provision of the oxidation catalyst 5 has the advantage that the SO _{3 formed} in the subsequent desulfurization of the exhaust gas through the modules 3 and 4 faster with the adsorbent, namely on the device 3 calcium-containing and / or sodium-containing powder introduced into the exhaust gas, as well as possibly faster with the calcium-containing granules of the precipitator 4 responding. This can reduce the effectiveness of desulfurization in the assemblies 3 and 4 be increased.

As active components in the oxidation catalyst 5 For the oxidation of SO ₂ to SO ₃ preferably the following chemical elements are used: V (vanadium), K (potassium), Na (sodium), Fe (iron), Ce (cerium) and Cs (cesium), the Proportion of vanadium (V) is more than 5%, preferably more than 7%, particularly preferably more than 9%. The base material used is the oxidation catalyst 5 TiO ₂ (titanium oxide) and / or SiO ₂ (silicon oxide), optionally stabilized by WO ₃ (tungsten oxide).

3 shows a variant of the invention, in which the internal combustion engine 1 is shown as an exhaust gas-charged internal combustion engine, in which therefore the exhaust aftertreatment system 2 a turbine 6 an exhaust gas turbocharger, in which the internal combustion engine 1 leaving exhaust gas is released to gain mechanical energy.

In such an exhaust-charged internal combustion engine is the oxidation catalyst 5 seen in the flow direction of the exhaust gas upstream of the turbine 6 arranged, the device 3 for introducing the calcium-containing and / or sodium-containing powder into the exhaust gas downstream of the turbine 6 is arranged.

The upstream of the turbine 6 prevailing, high pressures and high temperatures in the exhaust stream favor the oxidation of SO ₂ in SO ₃ in the oxidation catalyst 5 ,

Preferably, the oxidation of SO ₂ in SO ₃ takes place in the oxidation catalyst 5 such that, downstream of the oxidation catalyst, the proportion of SO ₃ of all sulfur oxides (SOx) in the exhaust gas is at least 20%, preferably more than 40%, particularly preferably more than 60%.

Another embodiment of an exhaust aftertreatment system according to the invention 2 for an internal combustion engine shows 4 , wherein the exhaust aftertreatment system 2 of the 4 as well as the exhaust aftertreatment system 2 of the 2 the oxidation catalyst 5 , the device 3 for introducing calcium-containing and / or sodium-containing powder into the waste gas, the separator designed as a moving bed reactor or fluidized bed reactor 4 as well as an additional facility 7 for introducing gaseous NH ₃ or NH ₃ precursor substances into the exhaust gas, this device 7 for introducing the gaseous NH ₃ in the exhaust gas downstream of the oxidation catalyst 5 is arranged so that therefore NH ₃ downstream of the oxidation catalyst 5 in the exhaust of the internal combustion engine 1 is introduced. It may be provided to introduce the NH ₃ either directly into the gas stream in the exhaust gas stream or to inject an NH ₃ precursor substance, such as urea, into the exhaust gas stream and to vaporize it in the exhaust gas stream to NH ₃ .

At the in 1 to 4 shown exhaust aftertreatment systems 2 may be a multi-stage, designed as a moving bed reactor or fluidized bed reactor separator 4 be used to improve the deposition of calcium sulfate and / or sodium sulfate, wherein when a multi-stage separator 4 is used in the individual stages of the separator 4 Granules of different particle size is used. In the individual stages of the designed as a moving bed reactor or fluidized bed reactor separator 4 Accordingly, the grain sizes of the granules and / or the type of granules differ from one another.

Preferably, a trained as a cross-flow separator separator 4 used.

The exhaust aftertreatment system according to the invention 1 allows effective desulfurization of exhaust gas. For the desulfurization of exhaust gas using the exhaust aftertreatment system according to the invention 2 For example, a calcium-containing and / or sodium-containing powder is first introduced downstream of the internal combustion engine into the internal combustion engine and then the exhaust gas is passed through a separator in the form of a granular-containing moving bed reactor or fluidized bed reactor. As related to 1 to 4 Desulfurization of the exhaust gas can be improved by oxidation of SO ₂ in SO ₃ upstream of the introduction of the calcium-containing and / or sodium-containing powder into the exhaust gas and optionally by introducing NH ₃ into the exhaust gas. It is based on the comments 1 to 4 directed.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

aftertreatment system

3

Facility

4

separators

5

oxidation catalyst

6

turbine

7

Facility

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3603365 C2 [0004]

Claims (19)

Exhaust aftertreatment system ( 2 ) for an internal combustion engine, with a downstream of an internal combustion engine ( 1 ) ( 3 ) for introducing calcium-containing and / or sodium-containing powder into an exhaust gas stream, and with a downstream of this device ( 3 ) arranged separators ( 4 ) in the form of a granulataltige moving bed reactor or fluidized bed reactor. Exhaust after-treatment system according to claim 1, characterized in that the particle size of the device ( 3 ) introduced into the exhaust stream, calcium-containing and / or sodium-containing powder is less than 1 mm, preferably less than 0.5 mm, more preferably less than 0.25 mm. Exhaust gas after-treatment system according to claim 1 or 2, characterized in that the calcium and / or sodium of the device ( 3 ) in the exhaust gas flow introduced, calcium-containing and / or sodium-containing powder has at least the oxidation state +1. Exhaust gas after-treatment system according to one of claims 1 to 3, characterized in that via the device ( 3 ) in the exhaust gas stream introduced, calcium-containing and / or sodium-containing powder CaO and / or Ca (OH) ₂ and / or CaCO ₃ and / or NaHCO ₃ and / or Na ₂ CO ₃ and / or MgO comprises. Exhaust after-treatment system according to one of claims 1 to 4, characterized in that the device ( 3 ) introduces the calcium-containing and / or sodium-containing powder dry as an aerosol or as a wet emulsion in the exhaust stream. Exhaust gas aftertreatment system according to one of claims 1 to 5, characterized in that the grain size of the granules in the moving bed reactor or fluidized bed reactor more than 2 mm, preferably more than 3 mm, more preferably more than 4 mm. Exhaust gas aftertreatment system according to one of claims 1 to 6, characterized in that the granules calcium and / or sodium and / or magnesium-containing. Exhaust gas aftertreatment system according to claim 7, characterized in that the granules comprise CaO and / or Ca (OH) ₂ and / or CaCO ₃ and / or Na ₂ CO ₃ and / or NaHCO ₃ and / or MgO. Exhaust gas aftertreatment system according to one of claims 1 to 8, characterized in that the moving bed reactor or fluidized bed reactor is formed in multiple stages, wherein the grain sizes of the granules in the individual stages of the moving bed reactor or fluidized bed reactor differ from each other. Exhaust gas aftertreatment system according to one of claims 1 to 9, characterized in that the moving bed reactor or fluidized bed reactor is designed as a cross-flow separator. Exhaust after-treatment system according to one of claims 1 to 10, characterized in that downstream of the internal combustion engine ( 1 ) and upstream of the device ( 3 ) for introducing the calcium-containing and / or sodium-containing powder into the exhaust gas stream, an oxidation catalyst ( 5 ) is arranged for SO ₂ oxidation. Exhaust gas aftertreatment system according to one of claims 1 to 11, characterized in that as active components in the oxidation catalyst ( 5 ) for the oxidation of SO ₂ to SO _{3 the} following chemical elements are used: V (vanadium), K (potassium), Na (sodium), Fe (iron), Ce (cerium) and Cs (cesium) on vanadium (V) is more than 5%, preferably more than 7%, particularly preferably more than 9%. Exhaust gas aftertreatment system according to one of claims 1 to 12, characterized in that the oxidation of SO ₂ in SO ₃ in the oxidation catalyst ( 5 ) is carried out such that downstream of the oxidation catalyst, the proportion of SO ₃ at all sulfur oxides (SOx) in the exhaust gas is at least 20%, preferably more than 40%, particularly preferably more than 60%. Exhaust after-treatment system according to claim 11, characterized in that in an exhaust-charged internal combustion engine, the oxidation catalyst ( 5 ) upstream of a turbine ( 6 ) of an exhaust gas turbocharger, wherein the device ( 3 ) for introducing the calcium-containing and / or sodium-containing powder downstream of the oxidation catalyst ( 5 ) is positioned. Exhaust after-treatment system according to claim 11 or 14, characterized by a device ( 7 ) for introducing gaseous NH ₃ into the exhaust stream upstream of the oxidation catalyst ( 5 ) is arranged. Exhaust gas aftertreatment system according to any one of claims 1 to 15, characterized by a separator associated with the moving bed reactor or fluidized bed reactor for separating together with the granules from the moving bed reactor or fluidized bed reactor precipitated CaSO ₄ and / or Na ₂ SO ₄ from the granules and for returning the CaSO ₄ and / or Na ₂ SO ₄ separated granules in the moving bed reactor or fluidized bed reactor. Exhaust gas aftertreatment system according to one of the preceding claims, characterized in that the granules are remilled and metered in front of the reactor A method for exhaust aftertreatment of exhaust gas leaving an internal combustion engine, wherein a calcium-containing and / or sodium-containing powder is first introduced into an exhaust gas stream and then the exhaust gas stream is passed through a granular-containing moving bed reactor or fluidized bed reactor. A method according to claim 18, characterized in that the same is carried out with the aid of the exhaust gas aftertreatment system according to one of claims 1 to 17.

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