FI128683B

FI128683B - Exhaust gas after-treatment system and method for the exhaust gas after-treatment

Info

Publication number: FI128683B
Application number: FI20155248A
Authority: FI
Inventors: Andreas Döring
Original assignee: Man Diesel & Turbo Se
Priority date: 2014-04-08
Filing date: 2015-04-07
Publication date: 2020-10-15
Also published as: JP6530222B2; CN105003324A; JP2015200312A; KR102271577B1; KR20150116791A; CN105003324B; DE102014005152A1; FI20155248A

Abstract

An exhaust gas after-treatment system (2) for an internal combustion engine (1), with a particle separator (3) in the form of a granulate-containing moving bed reactor or fluidised bed reactor arranged downstream of an internal combustion engine (1) for removing soot and ash particles from the exhaust gas, wherein exhaust gas to be purified in the particle separator (3) can be fed to the particle separator (3) via at least one exhaust gas feed line (4), wherein exhaust gas purified in the particle separator (3) can be discharged from the particle separator (3) via at least one exhaust gas discharge line (5), wherein granulate can be fed to the particle separator (3) via at least one granulate feed (6), wherein granulate can be discharged from the particle separator (3) via at least one granulate drain (7), wherein the exhaust gas in the particle separator (3) flows about the granulate and in the process soot and ash particles adhere to the granulate and/or are bound on the granulate and/or react with the granulate, and wherein the granulate together with the soot and ash particles, and/or the reaction products of the same can be discharged from the particle separator (3) via the or each granulate drain (7); and with a separating device (8) assigned to the particle separator (3) for separating from the granulate soot and ash particles and/or reaction products of the same separated out of the particle separator (3) together with the granulate and for the at least partial return of the granulate separated from the soot and ash particles and/or of reaction products of the same into the particle separator (3) via at least one of the granulate feeds (6).

Description

Exhaust gas after-treatment system and method for the exhaust gas after- treatment The invention relates to an exhaust gas after-treatment system. The invention furthermore relates to a method for the exhaust gas after-treatment. To minimise the carbon-containing particulate matter from the combustion, so- called particle filters are usually employed. A typical particle filter arrangement is known from the document US 4415344 A. In such particle filters, the filter medium, which consists of ceramic, metallic or fibrous base material, is sub- jected to the throughflow of exhaust gas. The particles contained in the ex- haust gas are accumulated in the filter material and are thus prevented from reaching the clean gas side of the filter. The filters have to be cleaned off or replaced at periodical intervals since they become clogged with ash from the combusted engine oil or fuel with increasing service life. For the replacement, the plant usually has to be shut down which leads to undesirable down times, in particular when it concerns plants in power plants or ships with high annual service life and availability requirements. Further prior art is disclosed in docu- ments DE 3641205 A1, GB 2070973 A and DE 3743561 A1.

From practice, exhaust gas after-treatment systems of internal combustion en- N gines are known, which comprise a particle filter, at least one exhaust gas af- N ter-treatment assembly arranged seen in flow direction of the exhaust gas up- = stream of the particle filter and at least one exhaust gas after-treatment as- - 25 sembly arranged seen in flow direction of the exhaust gas downstream of the E particle filter. An exhaust gas after-treatment assembly positioned seen in flow X direction upstream of the particle filter is in particular an oxidation catalytic 5 converter for the oxidation of nitrogen monoxide (NO) into nitrogen dioxide N (NO>2). An exhaust gas after-treatment assembly positioned seen in flow direc- tion downstream of the particle filter can be a silencer. In particular when seen in flow direction of the exhaust gas flow an oxidation catalytic converter for the oxidation of NO into NO? is positioned upstream of the particle filter, NO is oxi- dised in the oxidation catalytic converter with the help of the residual oxygen O? contained in the exhaust gas flow into NO? according to the following equa- — tion: 2NO +02 2NO> During this oxidation of nitrogen monoxide into nitrogen dioxide the equilibrium of the oxidation reaction at high temperatures is at the side of nitrogen monox- ide. This results in that the achievable component of nitrogen dioxide is greatly limited at high temperatures. In the particle filter, the nitrogen dioxide extracted in the oxidation catalytic converter is converted with the carbon-containing particles collecting in the particle filter, so-called soot, into carbon monoxide (CO), carbon dioxide (CO), nitrogen (N2) and nitrogen monoxide (NO). In the process, a continual removal of the carbon-containing particulate matter or of the soot accumulated in the particle filter takes place in the sense of a passive regeneration of the particle filter, wherein this conversion takes place according to the following equations:

O

O N 2N0+C SS 2 NO + CO> o = NO2 + C + NO + CO

N I 2C+2N0O2 —» N2+2CO2 00 25

N DO In particular when with such a passive regeneration of the particle filter no N complete conversion of the carbon-containing particulate matter or of the soot accumulated in the particle filter can take place, the carbon component or soot component in the particle filter increases, wherein the particle filter then has a tendency towards clogging, as a result of which ultimately a so-called exhaust gas back pressure on an internal combustion engine arranged upstream of the exhaust gas after-treatment system increases. An increasing exhaust gas backpressure on the internal combustion engine reduces the power of the in- ternal combustion engine and causes increased fuel consumption. In order to avoid an increase of the carbon-containing particulate matter or of the soot in the particle filter and thus clogging of the same it is also already known from practice to provide particle filters with a catalytic coating. Here, preferentially platinum-containing coatings are employed. The use of such par- ticle filters with catalytic coating however can prevent charging the particle filter with carbon-containing particulate matter, i.e. with soot, only to an inadequate degree.

In particular when this is typically the case in marine diesel engines, the inter- nal combustion engine, in which the exhaust gas after-treatment system is op- erated, is operated with highly sulphur-containing fuel such as for example heavy fuel oil there is the further problem that because of the intensive accu- mulation of ash clogging of a particle filter of the exhaust gas after-treatment system can likewise occur. In particular in the case of internal combustion en- o gines operated with heavy fuel oil, maintenance intervals of particle filters can S be dramatically shortened through the ash that is incurred so that meaningful 3 operation of the exhaust gas after-treatment system is no longer possible. N 25

I E Starting out from this, the present invention is based on the object of creating a S new type of exhaust gas after-treatment system and a new type of method for O the exhaust gas after-treatment. This object is solved through an exhaust gas N after-treatment system according to Claim 1.

The exhaust gas after-treatment system according to the invention comprises a particle separator in the form of a granulate-containing moving bed reactor or fluidised bed reactor downstream of an internal combustion engine for remov- ing soot and ash particles from the exhaust gas, wherein in the particle separa- tor exhaust gas to be purified can be fed to the particle separator via at least one exhaust gas feed line, wherein in the particle separator purified exhaust gas can be discharged from the particle separator via at least one exhaust gas line, wherein granulate can be fed to the particle separator via at least one granulate feed, wherein granulate can be discharged from the particle separa- tor via at least one granulate discharge, wherein the exhaust gas in the particle separator flows about the granulate and in the process soot and ash particles adhere to the granulate and/or are bound in the granulate and/or react with the granulate, and wherein the granulate together with the soot and ash particles and/or the reaction products of the same can be discharged from the particle separator via the or each granulate drain.

Furthermore, the exhaust gas after-treatment system according to the inven- tion comprises a separating device assigned to the particle separator for sepa- rating soot and ash particles separated out of the particle separator together — with the granulate and/or reaction products of the same from the granulate and for the at least partial return of the granulate separated from soot and ash par- ticles and/or from reaction products of the same into the particle separator via N at least one of the granulate feeds. 2 & 25 The invention proposes an exhaust gas after-treatment system which compris- E es at least one particle separator in the form of a granulate-containing moving o bed reactor of fluidised bed reactor and a separating device assigned to the io particle separator.

In the particle separator, soot and ash particles can be ef- > fectively separated from the exhaust gas and discharged via the granulate.

In the separating device, the granulate can be separated from the soot and ash particles and/or from reaction products of the soot and ash particles with the granulate, in order to return cleaned granulate at least partially to the particle separator again. Thus, effective exhaust gas purification, namely removal of soot and ash particles from the exhaust gas of the internal combustion engine is possible. In particular in the case of internal combustion engines operated 5 with heavy fuel oil, which are employed for example on ships, effective removal of soot and ash particles from the exhaust gas of the internal combustion en- gine can be realised. According to an advantageous further development, the particle separator is designed as a moving bed reactor or fluidised bed reactor in the cross flow of exhaust gas and granulate in such a manner that the exhaust gas flows through the particle separator in horizontal direction, that the granulate can be fed to the particle separator via the or each granulate feed and can be drained via the or each granulate drain from the bottom, and that a moving or flow di- rection of the granulate between the or each granulate feed and the or each granulate drain in vertical direction runs crossing with respect to the flow direc- tion of the exhaust gas. Such a cross flow particle separator allows a particu- larly effective removal of the soot and ash particles from the exhaust gas of the internal combustion engine.

Preferentially, the particle separator is embodied in multiple stages, wherein o the exhaust gas consecutively flows through the individual stages of the parti- O cle separator, and wherein in the individual stages the chemical composition of 3 the granulate and/or the size of the granulate and/or the moving or flow speed & 25 of the granulate and/or the flow velocity of the exhaust gas deviate from one E another. The effectiveness of the removal of the soot and ash particles from o the exhaust gas of the internal combustion engine can thereby be further in- io creased.

S

According to an advantageous further development, the exhaust gas after- treatment system comprises an oxidation catalytic converter arranged up- stream of the particle separator and downstream of the internal combustion engine for the oxidation of SO? into SOs, wherein the SO3 and/or precipitated H2S04 serves for the oxidation of soot directly in the particle separator. By way of the oxidation catalytic converter for the oxidation of SO? into SO3 the oxida- tion of the soot in the particle separator can be improved. According to a further advantageous further development, an oxidation catalyt- ic converter for the oxidation of NO into NO? is arranged upstream of the parti- cle separator and downstream of the internal combustion engine, wherein the NO: serves for the oxidation of soot in the particle separator, and wherein the oxidation catalytic converter for the oxidation of NO into NO? is connected par- allel to the oxidation catalytic converter for the oxidation of SO? into SOs and can be shut off from the exhaust gas flow through shut-off valves. During oper- ation of the internal combustion engine with a fuel that is relatively highly sul- phur-containing, the exhaust gas flow can be conducted via the oxidation cata- lytic converter for the oxidation of SO? into SOs, whereas during operation of the internal combustion engine with a fuel that is relatively lightly sulphur- containing, the exhaust gas flow can be conducted via the oxidation catalytic converter for the oxidation of NO into NO>. This configuration is advantageous when internal combustion engines with different types of fuel are operated. N This is the case in marine engines.

N 3 & 25 In the case of an exhaust gas supercharged internal combustion engine, the E oxidation catalytic converter for the oxidation of SO? into SOs is positioned up- o stream of a turbine of an exhaust gas turbocharger, wherein the particle sepa- io rator is positioned downstream of the turbine. Because of the relatively high > temperatures and pressure that are present upstream of the turbine the oxida- tion of SO? into SO3 in the oxidation catalytic converter is favoured.

According to a further advantageous further development, the exhaust gas af- ter-treatment system according to the invention comprises a reactor arranged downstream of the separating device, which can be supplied on the one hand an oxidant for the oxidation of soot and on the other hand the soot and ash particles which are separated from the granulate in the separating device. Downstream of the separating device, the ash separated from the granulate can thus be effectively freed of soot. The reactor, in a further embodiment, can also be arranged between the particle separator and the separating device, so that carbon-containing soot can be oxidised even before entering the separat- ing device.

The method for the exhaust gas after-treatment according to the invention is defined in Claim 14.

Preferred further developments of the invention are obtained from the sub- claims and the following description. Exemplary embodiments of the invention are explained in more detail with the help of the drawing without being restrict- ed to this. There it shows: Fig. 1: a block diagram of a first exhaust gas after-treatment system accord- ing to the invention;

S S Fig. 2: a detail of Fig. 1; 2 Fig. 3: a block diagram of a second exhaust gas after-treatment system ac- N cording to the invention; E 25 Fig. 4: a block diagram of a third exhaust gas after-treatment system accord- X ing to the invention; 3 Fig. 5: a block diagram of a fourth exhaust gas after-treatment system ac- N cording to the invention; and

Fig. 6: a block diagram of a fifth exhaust gas after-treatment system accord- ing to the invention. The present invention relates to an exhaust gas after-treatment system for an internal combustion engine, preferentially for an internal combustion engine employed on a ship, which is operated with highly sulphur-containing fuel such as for example heavy fuel oil. Fig. 1 shows a first exemplary embodiment of an exhaust gas after-treatment system 2 positioned downstream of an internal combustion engine 1. The ex- haust gas after-treatment system 2 of Fig. 1 comprises a particle separator 3 positioned downstream of the internal combustion engine 1. The particle sepa- rator 3 is a granulate-containing moving bed reactor or fluidised bed reactor, which serves for removing soot and ash particles from the exhaust gas of the internal combustion engine 1. It is pointed out here that both seen in flow direction of the exhaust gas up- stream of the particle separator 3 and also seen in flow direction of the exhaust gas downstream of the particle separator 3 at least one further exhaust gas after-treatment component of the exhaust gas after-treatment system each can be positioned.

O

S 3 The particle separator 3 can be supplied with exhaust gas to be purified in the N particle separator 3 via at least one exhaust gas feed line 4. Exhaust gas puri- z 25 fied in the particle separator 3 can be discharged from the particle separator 3 2 via at least one exhaust gas discharge line 5. Granulate needed in the particle io separator 3 can be fed to the particle separator 3 via at least one granulate > feed 6, wherein granulate can be discharged from the particle separator 3 via at least one granulate drain 7.

In the particle separator 3, the exhaust gas circulates about the granulate wherein in the process soot and ash particles of the exhaust gas adhere to the granulate and/or are bound on the granulate and/or react with the granulate, wherein the granulate together with the soot and ash particles and/or the reac- tion products of the same can be discharged from the particle separator 3 via the or each granulate drain 7.

The particle separator 3 is assigned a separating device 8. The separating de- vice 8 can be supplied with the granulate discharged from the particle separa- tor 3 via the or each granulate drain 7 together with the soot and ash particles and/or the reaction products of the same, wherein the separating device 8 separates the soot and ash particles and/or the reaction products of the same from the granulate. Soot and ash particles and/or reaction products of the same can be discharged from the separating device 8 following the separation from the granulate according to the arrow 9, wherein cleaned granulate can be at least partially returned into the particle separator 3 via at least one granulate feed 6 according to the arrow 10. Fig. 2 shows details of the particle separator 3, wherein the particle separator 3 which is schematically shown in Fig. 2 is embodied in multiple stages. Exhaust S gas to be purified in the particle separator 3, which can be fed to the particle N separator 3 of Fig. 2 via the exhaust gas feed line 4 initially flows through a first 3 stage 11 and following this a second stage 12 of the particle separator 3 in or- & 25 der to be subsequently discharged from the particle separator 3 via the ex- E haust gas discharge line 5. Both stages 11 and 12 of the particle separator 3 x are each embodied as moving bed reactors or fluidised bed reactors, wherein LO each of these two stages 11, 12 can be supplied with the granulate 13 and 14 2 respectively needed in the respective stage 11, 12 via a granulate feed 6 and the respective granulate 13, 14 can be discharged from the respective stage 11, 12 via a granulate drain 7.

In particular when as shown in Fig. 2 the particle separator 3 is embodied in multiple stages, the chemical composition of the granulate 13, 14 and/or the size of the granulate 13, 14 and/or the moving or flow speed of the granulate 13, 14 and/or the flow velocity of the exhaust gas can preferentially deviate from one another in the individual stages 11, 12 of the particle separator 3.

Accordingly it is possible for example to use granulate with identical chemical composition however different grain size and different moving or flow speed in the individual stages 11, 12. Furthermore it is possible for example to use granulate 13, 14 with different chemical composition in the individual stages 11, 12, namely on the one hand catalytically active and on the other hand cata- — lytically inactive granulate. Even when in particular in the individual stages 11, 12 granulate 13, 14 is used which differs with respect to its chemical composi- tion can the size of the granulate and/or the moving or flow speed of the same deviate from one another in the individual stages 11, 13.

The particle separator 3, which is embodied as a moving bed reactor or fluid- ised bed reactor preferentially is a particle separator 3 in the cross flow of ex- S haust gas and granulate.

S N Accordingly, it is evident in particular from Fig. 2 that the exhaust gas flows = 25 through the particle separator 3 in horizontal direction, whereas the granulate e 13 and 14 respectively of the individual stages 11, 12 of the respective stage io 11, 12 can be fed in from the top and discharged from the respective stages > 11, 12 from the bottom, and wherein the moving and flow direction of the re- spective granulate 13, 14 runs in vertical direction from the top down crossing the flow direction 24 of the exhaust gas. This makes possible a particularly ef- fective removal of soot and ash particles in the particle separator 3. As already mentioned above, catalytically inactive granulate can be utilised as granulate 13, 14 in the particle separator 3. Here, granulate of cordierite, gran- ite, corundum, silicon carbide, aluminium oxide or of metallic materials can be employed in particular. By deflecting the soot and ash particles in the stages 11, 12 of the particle separator 3, the soot and ash particles are separated on the granulate through impaction and/or diffusion and/or interception.

Fig. 3 shows a further development of the exhaust gas after-treatment system 2 of Fig. 1, in which downstream of the separating device 8 a reactor 15 is po- sitioned. The reactor 15 can be supplied on the one hand starting out from the separating device 8 soot and ash particles according to the arrow 9, likewise an oxidant according to an arrow 16. In the reactor 15, the soot particles are oxidised in order to thereby free the ash of soot. Ash freed of soot can be dis- charged from the oxidation catalytic converter 15 according to the arrow 17. CO: created during the oxidation of the soot is discharged from the reactor 15 according to the arrow 18. As oxidant in the reactor 15, H?S04 and/or HNO3 and/or NO? and/or SOs and/or SO; can be preferentially utilised. In particular when NO? and/or SOs S from the reactor 15 is utilised as oxidant, these oxidants can be generated on a N catalyst 24 through oxidation of NO and/or SO; contained in the exhaust gas. 3 H2SO4 and HNO3 can be extracted through subsequent condensation. HoSO4 N 25 — (sulphuric acid) can effectively oxidise soot in particular at temperatures below E: 250 °C. The condensation can take place in a separate condenser 25 and/or in x the reactor 15. 3

N

The oxidation of the soot in the oxidation catalytic converter 15 with the help of SOs as oxidant in this case takes place according to the following reaction equations: 2803+ C — COz + 2 502 S03 + C + CO + S09 In order to accelerate the oxidation of the soot in the oxidation catalytic con- verter 15, a heating device can be arranged upstream of the oxidation catalytic converter 15 in order to heat the soot and ash particles, which are fed to the oxidation catalytic converter 15, to a defined process temperature. A further exemplary embodiment of an exhaust gas after-treatment system 2 assigned to an internal combustion engine 1 is shown by Fig. 4, wherein the exemplary embodiment of Fig. 4 differs from the exemplary embodiment of Fig. 1 in that upstream of the particle separator 3 and downstream of the internal combustion engine 1 an oxidation catalytic converter 19 for the oxidation of SO; into SO3 is provided. In the oxidation catalytic converter 19, the oxidation of SO; into SO; takes place according to the following reaction equation:

O N 280; + 02 «>» 2 SOs

N 2 In the oxidation catalytic converter 3, the SO? contained in the exhaust gas of > the internal combustion engine 1 is oxidised into SOs, wherein the SO3 ex- I tracted in this process serves for the oxidation of soot directly in the particle N 25 separator 3. The oxidation of the soot in the particle separator 3 with the help N of the SO3 formed in the oxidation catalytic converter 19 in this case takes = place again according to the following reaction eguations:

N

2803+ C — COz + 2 502 S03 + C + CO + S09 Should the exhaust gas cool down to below the sulphuric acid dew point, pre- cipitation of H2SO4 (sulphuric acid) takes place according to the following reac- tion equation: SOs + H20— H2S04 wherein HSOa can be likewise utilised for the oxidation of soot in the particle separator 3. Here, sulphuric acid can effectively oxidise soot in particular at exhaust gas temperatures below 250 °C.

The oxidation catalytic converter 19 uses vanadium (V) and/or potassium (K) and/or sodium (Na) and/or iron (For example) and/or cer (C) and/or caesium (Cs) and/or oxides of these elements as active component for the oxidation of SO; into SO3, wherein the oxidation catalytic converter 19 utilises titanium ox- ide TiO, and/or silicon oxide SiO; preferentially stabilised by tungsten oxide WO3. The component of vanadium in the oxidation catalytic converter 19, which is present as active component for the oxidation of SO? into SO3 is more N than 5 %, preferentially more than 7 %, particularly preferably more than 9 %. N It is likewise possible to introduce vanadium into the exhaust gas and/or utilise = vanadium-containing fuel for operating the internal combustion engine.

The - vanadium component is at least 20 mg/kg, preferably 50 mg/kg, most prefera- E 25 bly 75 mg/kg.

The conversion of SO? into SO3 in the oxidation catalytic con- X verter 19 takes place in such a manner that downstream of the oxidation cata- 0 lytic converter 3 in the region of the particle separator 3 a mass ratio between N SOs and soot of at least 7:1, preferably of at least 12:1, particularly preferably of at least 16:1 is present.

Fig. 5 shows a further development of the exhaust gas after-treatment system 2 of Fig. 4, wherein the internal combustion engine of Fig. 5 is an exhaust gas supercharged internal combustion engine, in which exhaust gas is thus ex- panded in a turbine 20 of an exhaust gas turbocharger in order to extract me- chanical energy, which serves for driving a compressor of the exhaust gas tur- bocharger which is not shown, in order to compress charge air to be fed to the internal combustion engine 1 in the compressor of the exhaust gas turbo- charger. In particular when the exhaust gas after-treatment system 2 as shown in Fig. 5 accordingly comprises a turbine 20 is the oxidation catalytic converter 19 positioned upstream of the turbine 20 and the particle separator 3 down- stream of the turbine 20. The high pressures and temperatures upstream of the turbine 20 of an exhaust gas turbocharger favour the oxidation of SO? into SOs in the oxidation catalytic converter 19.

A further advantageous further development of the exhaust gas after-treatment system 2 of Fig. 4 is shown by Fig. 6, wherein the version of Fig. 6 is particu- larly utilised in internal combustion engines 1 such as are operated both with fuel having a relatively high sulphur content as well as with fuel having a rela- tively low sulphur content. Accordingly, Fig. 6 shows an exhaust gas after- treatment system 2 which in turn comprises an oxidation catalytic converter 19 S arranged upstream of the internal combustion engine 1 for the oxidation of SO? O into SO3 and a particle separator 3 arranged downstream of said oxidation 2 catalytic converter 19, wherein however the exhaust gas after-treatment sys- 2 25 tem 2 of Fig. 6 additionally comprises an oxidation catalytic converter 21 for I the oxidation of NO into NO2. The NO? extracted in the oxidation catalytic con- © verter 21 likewise serves for the oxidation of soot in the particle separator 3. In N Fig. 6, the oxidation catalytic converter 21 for the oxidation of NO into NO? is = connected parallel to the oxidation catalytic converter 19 for the oxidation of N 30 SO? into SO3, wherein the exhaust gas of the internal combustion engine is conducted either via the oxidation catalytic converter 19 or via the oxidation catalytic converter 21 dependent on the opening position of shut-off valves 22,

23. In particular when the internal combustion engine 1 is operated with a fuel that is relatively highly sulphur-containing, the shut-off valves 22 are opened and the shut-off valves 23 closed, so that the exhaust gas flow of the internal com- bustion engine 1 is then conducted via the oxidation catalytic converter 19 for the oxidation of SO? into SO3 and the oxidation catalytic converter 21 for the oxidation of NO into NO? is separated from the exhaust gas flow. If by contrast the internal combustion engine 1 of Fig. 6 is operated with fuel that is relatively lightly sulphur-containing, the shut-off valves 23 are opened and the shut-off valves 22 closed, so that the exhaust gas is conducted via the oxidation cata- lytic converter 21 for the oxidation of NO into NO», wherein the oxidation cata- lytic converter 19 for the oxidation of SO? into SOs is separated or shut-off from — the exhaust gas flow. The version of Fig. 6 is suitable in particular for use with marine engines, which on the one hand are operated with highly sulphur- containing fuel and on the other hand with lightly sulphur-containing fuel. In particular when during operation of the internal combustion engine 1 with highly sulphur-containing fuel the shut-off valves 23 are closed, will the oxida- tion catalytic converter 21, which serves for the oxidation of NO into NO, kept o sulphur-free.

S 3 o An alternative to this consists in omitting the shut-off valves and rendering the - 25 oxidation catalytic converter 21 suitable for operation following operation with E highly sulphur-containing fuel in that the exhaust gas temperature is raised and X sulphur thus desorbed in the oxidation catalytic converter 21. The version with 3 the shut-off valves 22, 23 however is preferred since then following operation N of the internal combustion engine 1 with sulphur-containing fuel the oxidation catalytic converter 21 is subsequently ready for operation immediately.

In the above exemplary embodiments the exhaust gas continuously flows through the particle separator 3, wherein the granulate can be continuously or periodically fed to the particle separator 3 and discharged from the same con- tinuously or periodically. The separating device 8 of the above exemplary embodiments can for exam- ple be a drum peeler, a drum screen, a vibrating screen, a mill or a scrubbing device which uses water as washing medium for cleaning the granulate.

As already mentioned above, catalytically active granulate can also be utilised as granulate 13, 14 in the particle separator 3. In this case, components of the exhaust gas can react with the granulate in the particle separator 3, wherein a drum peeler is then preferentially utilised as separating device 8 in order to separate a shell of the granulate, in which the granulate has reacted with com- ponents of the exhaust gas, from a core of the granulate that has not yet re- acted with the components of the exhaust gas. With the method for the exhaust gas after-treatment of exhaust gas leaving an internal combustion engine according to the invention, an exhaust gas flow is o conducted via the particle separator 3, wherein together with the granulate O soot and ash particles discharged from the particle separator 3 and/or reaction 2 products of the same are separated from the granulate in the separating de- > vice 8, and wherein the granulate separated from the soot and ash particles I 25 and/or of reaction products of the same is at least partially returned into the N particle separator 3. Further details of the method for the exhaust gas after- N treatment are obtained from the above description of the exhaust gas after- 2 treatment systems of Fig. 1 to 6 according to the invention.

List of reference numbers 1 Internal combustion engine 2 Exhaust gas after-treatment system 3 Particle separator 4 Exhaust gas feed line 5 Exhaust gas discharge line 6 Granulate feed 7 Granulate drain 8 Separating device 9 Ash and soot particles 10 Cleaned granulate 11 Stage 12 Stage 13 Granulate 14 Granulate 15 Oxidation catalytic converter 16 Oxidant 17 Ash 18 Carbon dioxide 19 Oxidation catalytic converter 20 Turbine o 21 Oxidation catalytic converter N 22 Shut-off valve 3 25 23 Shut-off valve Q 24 Exhaust gas flow j

X 3

N

Claims

1. An exhaust gas after-treatment system (2) for an internal combustion en- gine (1), with a particle separator (3) in the form of a granulate-containing moving bed reactor or fluidised bed reactor for removing soot and ash particles from the exhaust gas arranged downstream of an internal combustion en- gine (1), wherein exhaust gas to be purified in the particle separator (3) can be fed to the particle separator (3) via at least one exhaust gas feed line (4), wherein exhaust gas purified in the particle separator (3) can be discharged from the particle separator (3) via at least one exhaust gas dis- charge line (5), wherein granulate (13, 14) can be fed to the particle sepa- rator (3) via at least one granulate feed (6), wherein granulate (13, 14) can be discharged from the particle separator (3) via at least one granulate drain (7), wherein the exhaust gas in the particle separator (3) flows about the granulate (13, 14) and in the process soot and ash particles adhere to the granulate (13, 14) and/or are bound on the granulate (13, 14) and/or react with the granulate (13, 14), and wherein the granulate (13, 14) to- gether with the soot and ash particles and/or the reaction products of the same can be discharged from the particle separator (3) via the or each granulate drain (7); a separating device (8) assigned to the particle separator (3) for N separating soot and ash particles and/or reaction products of the same N separated out of the particle separator (3) together with the granulate (13, = 25 14) from the granulate (13, 14) and for the at least partial return of the - granulate separated from the soot and ash particles and/or from reaction E products of the same into the particle separator (3) via at least one of the X granulate feeds (6).

LO

N

2. The exhaust gas after-treatment system according to Claim 1, character- ized in that the granulate consists of cordierite, granite, corundum, silicon carbide, aluminium oxide or of metallic materials.

3. The exhaust gas after-treatment system according to Claim 1, character- ized in that the exhaust gas continuously flows through the particle sepa- rator (3), and in that the granulate can be continuously or periodically fed to the particle separator (3) and continuously or periodically discharged from the same.

4. The exhaust gas after-treatment system according to Claim 1 or 3, charac- terized in that the particle separator (3) is designed as a moving bed reac- tor or fluidised bed reactor in the cross flow of exhaust gas and granulate (13, 14) in such a manner that the exhaust gas flows through the particle separator (3) in horizontal direction, and in that a moving or flow direction of the granulate runs in vertical direction crossing the flow direction of the exhaust gas.

5. The exhaust gas after-treatment system according to Claim 4, character- S 20 ized in that the granulate (13, 14) can be supplied to the particle separator 2 (3) via the or each granulate feed (6) from the top and discharged via the o or each granulate drain (7) from the bottom, so that the moving or flow di- - rection of the granulate (13, 14) between the or each granulate feed (6) , and the or each granulate drain (7) takes place in vertical direction from 3 25 the top down.

N

6. The exhaust gas after-treatment system according to any one of the Claims 1 to 5, characterized in that the particle separator (3) is embodied in multiple stages, wherein the exhaust gas consecutively flows through the individual stages (11, 12) of the particle separator (3), wherein in the individual stages (11, 12) the chemical composition of the granulate (13, 14) and/or the size of the granulate (13, 14) and/or the moving or flow speed of the granulate (13, 14) and/or the flow velocity of the exhaust gas deviate from one another.

7. The exhaust gas after-treatment system according to any one of the Claims 1 to 6, characterized in that the granulate (13, 14) of at least one stage (11, 12) of the particle separator (3) is catalytically active.

8. The exhaust gas after-treatment system according to any one of the Claims 1 to 7, characterized in that the granulate (13, 14) of at least one stage (11, 12) of the particle separator (3) is catalytically inactive.

9. The exhaust gas after-treatment system according to any one of the Claims 1 to 8, characterized by an oxidation catalytic converter (19) ar- N 20 ranged upstream of the particle separator (3) and downstream of the inter- N nal combustion engine (1) for the oxidation of SO? into SO3, wherein the 3 SOs and/or precipitated H2SOa serves for the oxidation of soot directly in N the particle separator (3). = 3 0 25

10. The exhaust gas after-treatment system according to Claim 9, character- S ized in that the oxidation catalytic converter (19) as active component for the oxidation of SO? into SO3 comprises vanadium and/or potassium and/or sodium and/or iron and/or cer and/or caesium and/or oxides of these elements, wherein the oxidation catalytic converter as base material utilises titanium oxide and/or silicon oxide preferentially stabilised by tung- sten oxide.

11. The exhaust gas after-treatment system according to Claim 9 or 10, char- acterized in that the oxidation catalytic converter (19) as active compo- nent comprises vanadium with a component of more than 5 %, preferably of more than 7 %, particularly preferably more than 9 %.

12. The exhaust gas after-treatment system according to any one of the Claims 9 to 11, characterized in that downstream of the oxidation catalyt- ic converter (19) in the region of the particle separator (3) a mass ratio be- tween SO3 and soot amounts to at least 7:1, preferably at least 12:1, par- ticularly preferably at least 16:1.

13. The exhaust gas after-treatment system according to any one of the Claims 9 to 12, characterized in that upstream of the particle separator (3) and downstream of the internal combustion engine (1) and oxidation S 20 catalytic converter (21) for the oxidation of NO into NO: is arranged, N wherein the NO? serves for the oxidation of soot in the particle separator 3 (3), wherein the oxidation catalytic converter (21) for the oxidation of NO N into NO? is connected parallel to the oxidation catalytic converter (19) for z the oxidation of SO? into SO3 and can be shut off from the exhaust gas X 25 flow through shut-off valves (23).

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14. The exhaust gas after-treatment system according to any one of the Claims 1 to 13, characterized by a reactor (15) arranged downstream of the separating device (8), which for the oxidation of soot on the one hand can be supplied with an oxidant and on the other hand the soot and ash particles separated from the granulate in the separating device (8).

15. A method for the exhaust gas after-treatment of exhaust gas leaving an internal combustion engine, wherein an exhaust gas flow is conducted via a particle separator in the form of a granulate-containing moving bed reac- tor or fluidised bed reactor, and wherein soot and ash particles and/or re- action products of the same discharged from the particle separator togeth- er with the granulate are separated from the granulate in a separating de- vice, and wherein the granulate separated from the soot and ash particles and/or reaction products of the same is at least partially returned into the particle separator.

16. The method according to Claim 15, characterized in that the same is car- ried out with the help of the exhaust gas after-treatment system according to any one of the Claims 1 to 14.

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