DE102010009946B4 - Emission control system and method for purifying exhaust gas - Google Patents

Abstract

Exhaust gas purification system (1) for purifying exhaust gas from a large-scale internal combustion engine system with a capacity greater than 1 MW, comprising a reactor arrangement (3) which has a catalyst device (8) through which the exhaust gas (A) can flow in a flow direction (s2) the reactor arrangement (3) has a plurality of reactors (4) arranged in parallel, each having a container (6) with a catalyst device (8) arranged therein, and a common supply line (16) for the exhaust gas (A) upstream of the respective catalyst device (8) and a common discharge line (18) for the exhaust gas (A) downstream of the respective catalyst device (8) with the respective container (6) is connected, so that in operation the exhaust gas stream into equal partial streams (a) divides, which the respective catalyst means (8 ), wherein the container (6) are formed as equal components and have a circumferential side wall (9), to the front side each a bottom and a lid adjoins, wherein the supply line (16) and the discharge (18) are laterally connected to the side wall (9) and the individual successive containers via connecting pieces (16 B, C; 18B, C) are connected to each other as part of the inlet or outlet, so that the inlet and outlet (16, 18) in the horizontal direction and senrecht to the flow direction of the exhaust gas (A) within the catalyst device (8)

Description

The invention relates to an exhaust gas purification system and a method for purifying exhaust gas, which originates from a large-scale engine system. Large-scale combustion engine systems are understood here to mean systems which have an output of a few MW up to 100 MW. In particular, these are understood as internal combustion engine systems in which the power is provided via a diesel engine. Such internal combustion engine systems are used for example as stationary systems in a power plant for power generation. In addition, such diesel engine systems are also used as drive motors in the shipping sector, especially in large cargo ships.

From the EP 1 189 681 B1 is an emission control system for a flue gas from a fired fossil fuel steam generator in a power plant to remove. The emission control system has a reactor arrangement called a catalyst tower. This comprises a catalyst device, formed by a plurality of successive catalyst layers in the flow direction. The catalyst device is used for nitrogen oxide reduction according to the principle of selective catalytic reduction. In this nitrogen oxides contained in the exhaust gas are admixed with a reducing agent, such as ammonia or a precursor thereof, such as aqueous urea solution, in the presence of the catalytically active material to nitrogen and water. Such catalysts are referred to as DeNOx catalysts or as SCR catalysts.

In large-scale internal combustion engine systems, the catalyst device is arranged due to the comparatively high exhaust gas pressures in the range of up to 10 bar in a pressure vessel through which the exhaust gas can flow. Due to the large amounts of exhaust gas due to the high performance of such pressure vessel must be designed very large volume. They are usually designed as cylindrical containers with a diameter in the range between 4 and 7 m and a height greater than 10 m, for example in the range of 12 to 13 m. In order to withstand the high pressures, the container wall must be correspondingly strong and has a wall thickness in the range between 40 and 100 mm. The container wall is made of steel.

Such pressure vessels are therefore assembled only immediately at the site and then subjected to a pressure test.

For an efficient cleaning effect as uniform as possible flow through the catalyst device is of crucial importance. Due to the different load conditions occurring in internal combustion engine systems, however, different flow conditions occur in the course of operation as a function of the respective engine load. This must be taken into account when designing and designing the reactor arrangement as far as possible. For this purpose, simulations are usually carried out, which are, however, usually very complex. Both the planning and the construction of such an emission control system is very complex due to this one-off production.

From the US 4,246,234 is to be taken from an exhaust gas purification system in which a plurality of catalyst devices are arranged in a common container and the exhaust gas to be cleaned are discharged via a plurality of supply lines to the container the catalyst devices to and via several outlets.

From the WO 2007/131035 A1 is to take an exhaust gas purification device in which a plurality of specially designed as monolithic units catalyst elements are arranged in a common housing.

From the DE 10 2007 013 867 A1 Furthermore, a modular system for the aftertreatment of engine exhaust gases can be taken, in which a soot particle filter is arranged in a respective module in addition to further catalyst units. Several modules are arranged side by side and are supplied via a manifold in parallel with the exhaust, with individual modules can be individually decoupled from the exhaust gas supply to allow regeneration of the particulate filter.

The invention has for its object to enable a simplified planning and construction of such an emission control system.

The object is achieved according to the invention by an exhaust gas purification system having the features of claim 1. Thereafter, a reactor arrangement is provided with a plurality of reactors connected in parallel, each having a container with catalyst means arranged therein. The exhaust gas is supplied via a common supply line to each of the individual reactors upstream of the catalyst device and discharged downstream of the catalyst device via a discharge line.

By dividing it into several reactors arranged parallel to one another, there is the decisive advantage that they can be formed significantly smaller in size compared to only one reactor. This allows the prefabrication of such individual reactors, which are already preferably pre-tested and certified. To create the Exhaust gas purification system therefore need only a plurality of such reactors to be connected to each other via the supply line or discharge. The reactor arrangement is therefore modularly composed of standardized reactors. Due to the smaller container volume also the exhaust gas pressure, which is for example in two-stroke engines in the range between 3 bar and 10 bar (3 · 10 ⁵ Pa to 10 · 10 ⁵ Pa), technically manageable with significantly less effort than when using only a large-volume reactor , Due to the standardization, the performance characteristics of the individual reactors can be determined better and more accurately. Overall, a higher qualification is achieved by this configuration with the parallel arrangement. This is understood inter alia that the efficiency of the exhaust gas purification is improved compared to conventional arrangements even with different load incidents. An important aspect in this case is the parallel arrangement of the individual reactors, which typically sets at least almost identical flow conditions in the individual reactors, so that the individual catalyst devices arranged in the reactors are flowed through uniformly.

The emission control system is designed for use in a large-scale combustion engine system. Under large-scale internal combustion engine system here is a system, especially diesel engine system, typically understood with a capacity of at least several megawatts up to 100 megawatts. The exhaust gas purification system is used in particular for two-stroke engines, which generate a high exhaust gas pressure.

The individual reactors are designed and arranged such that, during operation, the exhaust gas flows through the reactors distributed in the same way. In particular, this is provided in a preferred development that a flow path for the exhaust gas through the reactor arrangement is independent of which reactor flows over a respective partial flow of the exhaust gas. The flow path is therefore always constant.

The containers and in particular also the catalyst devices contained therein are identical and preferably identical. Under the same design of the container is in this case understood in particular their same geometric configuration. The individual containers are therefore at least approximately the same and preferably identical in terms of their height and diameter and thus also their container volume, as well as the basic geometry. The containers are preferably designed as cylindrical containers with a particular dome-shaped bottom and lid. The bottom and the lid are each fixedly connected to the cylindrical side wall, for example by welding. Preferably, the individual containers are also formed identically with respect to the material used and the wall thickness, etc. These are therefore equal components. These equal components preferably have connecting flanges for the supply and discharge at the same positions, blank flanges also being able to be provided. Alternatively, the equi-components are suitably assembled by attaching connecting flanges so that, depending on whether the reactor within the reactor arrangement is a first reactor, a middle reactor or a last reactor, they have different connections for the supply. and derivatives.

In this case, the same or identical catalyst devices are understood in particular to mean that they are preferably designed as modules and have the same design with regard to their construction and their geometric dimensions as well as with regard to the catalyst material. Preference is given to using modules as catalyst devices which are likewise prefabricated into the respective containers. The respective catalyst device preferably has a plurality of individual and juxtaposed in a plane catalysts, which are in particular designed as honeycomb catalysts. These are preferably formed as a monolithic body of a Vollextrudat. The honeycomb bodies optionally consist of a catalytically active material or are impregnated or coated with a catalytically active material. The individual catalysts have a multiplicity of individual flow channels which are separated from one another by webs and through which the exhaust gas flows in the flow direction. Preferably, the individual reactors contain only one layer of such catalysts. In contrast to previous reactor arrangements with only one container, in which usually several consecutive successive layers of catalysts are provided in the flow direction, therefore, the structure is simplified and improved. In particular, however, improved flow conditions are achieved in comparison to a plurality of layers connected in series.

The individual features described above, namely the same flow path, the same design of the container and the same configuration of the catalyst devices in each case promote the most uniform and homogeneous flow of the individual catalyst devices and thus efficient exhaust gas purification. In particular, in combination, these features result in a load-independent, even distribution of the exhaust gas flow over the entire flow area provided by the individual reactors.

Due to the identical or at least similar design of the individual reactors and their parallel connection namely the flow resistance for the exhaust gas in the individual reactors is the same, which has the consequence that the same pressure losses occur in each reactor. Since the same reactor geometries are provided in addition, the same flow rates are established in each reactor and the exhaust gas flow is distributed uniformly among the different reactors.

The containers each have a circumferential side wall, at the end of each connect a bottom and a lid. The supply and discharge are connected laterally on this side wall and the individual successive containers are also connected laterally via connecting pieces as part of the supply or discharge.

The containers are usually mounted vertically in their longitudinal direction, d. H. the longitudinal direction of the usually cylindrical container extends in the direction of the cylinder axis. The inlet and outlet extends in the horizontal direction or generally perpendicular to the flow direction of the exhaust gas within the catalyst device. In general, therefore, the arrangement results in a deflection of the exhaust gas, in particular by 90 ° when the exhaust gas flows from the supply line into the container. The case required conversion of the kinetic energy of the original horizontal flow in pressure energy supports a uniform and homogeneous flow of the catalyst device. Since the derivative is also arranged horizontally, the exhaust gas flow is in turn preferably deflected by 90 ° after flowing through the catalyst device.

Preferably, all portions of the horizontally extending supply line and in particular also the horizontally arranged discharge are arranged at the same height, so they are aligned with each other.

Conveniently, the containers are designed as pressure vessels for exhaust gas pressure in the range of 3 x 10 ⁵ Pa to 10 x 10 ⁵ Pa to withstand the exhaust pressure, especially in two stroke diesel engines.

The containers preferably have a height of about 3 to 7 m and in particular of about 5 m. Conveniently, a diameter of about 2 to 4 m and preferably in the range of about 2.5 to 3 m is provided at the same time. Finally, the wall thickness is preferably in the range between 10 and 30 mm, in particular in the range between 20 and 25 mm. Compared to the previously known containers are therefore relatively small-sized container that can be easily supplied as prefabricated units in the corresponding engine rooms of a combustion engine system and installed there. A delivery in individual parts and an assembly only on site is therefore not necessary and not provided.

The containers are rather in a preferred embodiment to prefabricated and in particular also tested standardized components that are already present before their assembly to the reactor system as prefabricated modular components.

In the exhaust gas purification system is preferably a system for nitrogen oxide reduction, in particular according to the principle of selective catalytic reduction. As catalysts in particular so-called DeNOx or SCR catalysts are used. A reducing agent required for the catalytic reduction is expediently introduced, in particular injected, into the supply line for the exhaust gas during operation via a feed point arranged upstream of the reactor arrangement. The reducing agent is in particular a liquid reducing agent or reducing agent solution, preferably an aqueous urea solution.

The object is further achieved according to the invention by a method for purifying an exhaust gas with the features of claim 8. With regard to the emission control system mentioned advantages and preferred embodiments are to be transferred analogously to the process.

An embodiment of the invention will be explained in more detail with reference to the single figure. This shows in a schematic and simplified representation of an emission control system.

The emission control system 2 has a reactor arrangement 3 with several parallel reactors 4 on, each one a container 6 and a catalyst device disposed therein 8th include. The containers 6 are preferably cylindrical with a side wall 9 a floor 10 as well as a lid 12 formed, which are preferably non-detachably connected to each other, for example by welding. Inspection hatches for the access (maintenance, replacement) of the catalyst device 8th are preferably provided, in particular in the side wall 9 , The containers 6 each extend along a central axis in the longitudinal direction 14 , In the embodiment, soil 10 and lid 12 each dome-shaped and in particular symmetrical to each other, as is customary in pressure vessels. The containers 6 have a circular cross-sectional area. Their diameter D is preferably in the range between 2.5 m and 3 m. The height H of the container is for example in the range of about 5 m. With the containers 6 it is a pressure vessel with a steel wall whose thickness is for example in the range between 20 and 25 mm.

A supply line 16 for the exhaust gas A extends in the embodiment in the horizontal direction and each opens into the side wall 9 of the respective container 6 , The supply line 16 therefore connects the individual containers quasi serially 6 together. It is for this purpose divided into different sections, namely an inlet piece 16A which is in the first reactor 4 opens, and a first and a second connector 16B , C, which is the first with the middle and the middle with the last reactor 4 connect.

In the same way are the reactors 4 also about a derivative 18 for the exhaust A connected to each other. The derivative 18 has an outlet piece 18A as well as connectors 18B , C up. The outlet piece 18A joins the last reactor 4 at.

The individual reactors are preferably at the same height and in particular equidistant from each other by the distance b, which is for example in the range of 1.5 to 3 times the diameter D.

Before the first reactor 4 is as a injection device 22 trained feed point for a reducing agent R arranged. Following the injection device 22 Can be provided with the exhaust gas A here not shown mixer for mixing the injected reducing agent.

The supply line 16 as well as the derivative 18 are formed as exhaust channels and in particular as exhaust pipes with a circular cross-section. The supply line 16 is connected to an internal combustion engine system not shown here. The derivative 18 is connected to an exhaust duct for the discharge of the purified waste gases to the environment.

In the respective catalyst device 8th it is an arrangement of a plurality of juxtaposed, in particular monolithic honeycomb catalysts with a plurality of individual flow channels, which are traversed by the exhaust gas A in operation. It can here several levels or layers of catalysts in the longitudinal direction 14 be arranged one behind the other.

The catalyst device 8th covered with the individual catalysts arranged side by side, the entire cross-sectional area of the container 6 so that the entire exhaust gas flow through the catalyst device 8th must flow through.

In conventional systems, flow guide elements are present before and / or between the individual layers, and in principle also in the individual reactors 4 can be provided. However, this is not absolutely necessary and due to the homogeneous and good inflow characteristic due to the parallel structure is preferably also omitted.

During operation, the exhaust gas A to be cleaned flows in the supply line 16 in a first horizontal flow direction s1 into the reactor 4 one. Due to the parallel arrangement, the exhaust gas stream is divided into three equal partial flows a. The partial flows a undergo a change in direction and flow through the catalyst device 8th in a second vertical flow direction s2. After flowing through the catalyst device 8th the sub-streams a again undergo a deflection, in order subsequently again in the horizontal flow direction s1 via the discharge line 18 abzuströmen.

Due to this configuration with the same trained individual reactors 4 arise within each reactor 4 the same pressure conditions, so that set equal partial flows a (identical volume flows) automatically. Due to the configuration chosen, the flow paths from an inlet side of the reactor arrangement to an outlet side of the reactor arrangement are identical. There are the same flow conditions for each partial flow a.

Due to the embodiment in the preferred embodiment 90 ° deflection from the first flow direction s1 in the second flow direction s2 is a homogeneous and over the entire surface of the catalyst devices 8th uniformly distributed flow of the entire catalyst surface favors. This homogeneous and uniform flow is given even in different load cases of the internal combustion engine system. Only the volume flows change.

Overall, this embodiment provides a modular reactor arrangement with a plurality of individual reactors 4 educated. At the reactors 4 These are prefabricated, standardized and similar module assemblies that no longer require individual pressure testing and certification. To assemble the reactor plant is only the connection of the supply line 16 as well as the derivative 18 required. The containers 6 For this example, have prepared connection flanges for attachment of the individual sections 16A , B, C; 18A , B, C of the supply line 16 or the derivative 18 on.

Due to the use of standardized components, the planning and construction of the entire emission control system can be carried out quickly and cost-effectively. It is easily adaptable to different requirements. In the exemplary embodiment is a reactor arrangement 3 with a total of three reactors 4 shown. Depending on the requirement, there are two or more individual reactors 4 connected in parallel. The individual cuts 16A , B, C; 18A , B, C between the individual reactors 4 can also be different in length and allow an uneven distribution of the reactors 4 for example, in different rooms or even different levels, without the functionality is impaired.

Claims (8)

Emission control system ( 1 ) for the purification of exhaust gas from a large-scale engine installation with a capacity greater than 1 MW, with a reactor arrangement ( 3 ) comprising a catalyst device ( 8th ), which can be traversed by the exhaust gas (A) in a flow direction (s2), wherein the reactor arrangement ( 3 ) several reactors arranged in parallel ( 4 ) each with a container ( 6 ) with catalyst device ( 8th ) and for this purpose a common supply line ( 16 ) for the exhaust gas (A) upstream of the respective catalyst device ( 8th ) and a common derivative ( 18 ) for the exhaust gas (A) downstream of the respective catalyst device ( 8th ) with the respective container ( 6 ) is connected, so that in operation the exhaust gas flow into equally large partial flows (a) divides, which the respective catalyst device ( 8th ), whereby the containers ( 6 ) are formed as equal components and a circumferential side wall ( 9 ), at the front side in each case a bottom and a lid adjoins, wherein the supply line ( 16 ) and the derivative ( 18 ) laterally on the side wall ( 9 ) and the individual successive containers via connecting pieces ( 16B , C; 18B , C) are connected as part of the inlet or outlet, so that the inlet and outlet ( 16 . 18 ) in the horizontal direction and senrecht to the flow direction of the exhaust gas (A) within the catalyst device ( 8th ) Emission control system ( 1 ) according to claim 1 or 2, characterized in that a flow path for the exhaust gas (A) through the reactor arrangement ( 3 ), irrespective of which of the reactors ( 4 ) the flow path leads. Emission control system ( 1 ) according to one of the preceding claims, characterized in that the containers ( 6 ) is designed in each case as a pressure vessel for an exhaust gas pressure in the range up to 3 · 10 ⁵ Pa to 10 · 10 ⁵ Pa. Emission control system ( 1 ) according to one of the preceding claims, characterized in that the containers ( 6 ) each have a height of about 3 to 7 m, and a diameter of about 2 to 4 m. Emission control system ( 1 ) according to one of the preceding claims, characterized in that it is in the containers ( 6 ) before their assembly to the reactor plant ( 3 ) prefabricated and tested components. Emission control system ( 1 ) according to one of the preceding claims, characterized in that the respective catalyst device ( 8th ) is designed for nitrogen oxide reduction and in particular acts on the principle of selective catalytic reduction. Emission control system ( 1 ) according to one of the preceding claims, in which upstream of the reactor arrangement ( 3 ) an entry point ( 22 ) is provided for introducing a reducing agent (R). Process for purifying an exhaust gas (A) of a large-scale combustion engine installation with a power greater than 1 MW with the aid of an exhaust gas purification system according to one of the preceding claims.

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