CN211474252U

CN211474252U - Diesel generating set with tail gas purification function

Info

Publication number: CN211474252U
Application number: CN202020102180.5U
Authority: CN
Inventors: 李建宏; 李铭
Original assignee: Quanzhou Hongsheng Electromechanical Co ltd
Current assignee: Quanzhou Hongsheng Electromechanical Co ltd
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2020-09-11
Anticipated expiration: 2030-01-16

Abstract

The utility model relates to a diesel generating set with tail gas purification function, which comprises a power generation system and a purification system communicated with the power generation system, wherein the power generation system comprises a box body, an oil tank, a cooling fan, an engine, a generator and a controller which are fixed in the box body; the purification system comprises a shell, a particulate filter and an SCR (selective catalytic reduction) catalyst which are fixed in the shell, wherein the particulate filter is communicated with the SCR catalyst, and an air guide pipe which penetrates through the box body is communicated between the particulate filter and the engine; the double purification of filtration and catalytic reduction is achieved through the particulate filter and the SCR catalyst, and the method has the advantage of improving the purification degree of the flue gas.

Description

Diesel generating set with tail gas purification function

Technical Field

The utility model belongs to the technical field of the generating set technique for the diesel engine and specifically relates to a diesel generating set with tail gas purification function is related to.

Background

At present, with the rapid development of economy and the continuous increase of electric energy sources, the application of diesel generating sets in various fields becomes more and more extensive and important. However, diesel gensets produce large amounts of carbon monoxide, sulfur dioxide, and soot when subjected to noisy emissions. The increase of carbon monoxide in the air can cause dizziness, vertigo and hypodynamia of workers; the smoke dust is attached with a large amount of chemical substances, wherein the chemical substances comprise carcinogenic substances, and can stay in the lung for a long time after being inhaled into a human body.

Chinese patent with publication number CN207795349U discloses a silencing black smoke purification device for generator set, which comprises a shell, wherein a diesel particulate filter and a glass fiber silencing device are sequentially arranged in the shell from one side to the other side, the diesel particulate filter is far away from one side of the glass fiber silencing device, a smoke outlet is arranged on the side surface of the shell, a smoke inlet is arranged on the shell below the glass fiber silencing device, and the smoke inlet is positioned on one side of the glass fiber silencing device, which is far away from the diesel particulate filter. Black cigarette process the utility model discloses smoke inlet access device of amortization black cigarette purifier bottom for generating set, at first access device's amortization chamber passes through diesel particulate filter after the noise reduction in amortization chamber and purifies the effect to black cigarette, finally advances the exhanst gas outlet discharge of device side, and the purifying effect of making an uproar is good.

The above prior art solutions have the following drawbacks: the generated smoke enters a silencing cavity of the device, is subjected to noise reduction treatment in the silencing cavity, then is subjected to purification effect on black smoke through a diesel particulate filter, and finally enters a smoke outlet on the side surface of the device to be discharged; although the silencing effect is achieved through the silencing cavity, only fixed particles in the smoke can be filtered through the filter, and gaseous toxic substances in the smoke are still discharged into the atmosphere, so that the smoke is purified to a low degree by the filter.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a diesel generating set, which has the advantage of improving the flue gas purification degree.

The above technical purpose of the present invention can be achieved by the following technical solutions:

a diesel generating set with a tail gas purification function comprises a power generation system and a purification system communicated with the power generation system, wherein the power generation system comprises a box body, an oil tank, a cooling fan, an engine, a generator and a controller, wherein the oil tank, the cooling fan, the engine, the generator and the controller are fixed in the box body; the purification system comprises a shell, and a particulate filter and an SCR (selective catalytic reduction) catalyst which are fixed in the shell, wherein the particulate filter is communicated with the SCR catalyst, and a gas guide pipe which penetrates through the box body is communicated between the particulate filter and the engine.

By adopting the technical scheme, when the cooling fan is used, the engine, the generator and the cooling fan are started through the controller; harmful flue gas can be generated in the running process of the engine, and the harmful flue gas is introduced into the purification system through the gas guide tube. Harmful flue gas firstly passes through the particulate filter, and particles with larger particle diameters in the flue gas cannot pass through the particulate filter and are filtered in the particulate filter, so that the effect of eliminating black smoke is achieved; gas after particle filtration enters an SCR catalyst, passes through a reducing agent in the SCR catalyst and is subjected to catalytic reaction under the action of a catalyst to reduce nitric oxide and nitrogen dioxide into nitrogen and water, so that the phenomena that the nitric oxide in tail gas is discharged into the air, the environment is polluted and the human body is damaged are avoided; namely, the double purification of filtration and catalytic reduction is achieved through the particulate filter and the SCR catalyst, and the method has the advantage of improving the purification degree of the flue gas.

The present invention may be further configured in a preferred embodiment as: an air inlet and an air outlet are respectively formed in two sides of the shell, one end of the air guide pipe is communicated with the generator, and the other end of the air guide pipe is fixed at the position, corresponding to the air inlet, of the shell; install a plurality of filter plates in the particulate filter, seted up a plurality of filtration pores on the filter plate, the filtration pore diameter from air inlet to gas vent filter reduces gradually.

By adopting the technical scheme, the tail gas enters the particulate filter, and particles with larger particle size are filtered through the micropores on the filter plate; the filter plates with gradually reduced diameters of the filter holes are used for filtering particles contained in the tail gas step by step, so that the flue gas can be effectively filtered, and the effect of eliminating black smoke is achieved; and can avoid the granule to concentrate and pile up in one side of first filter, the problem of the clearance of being not convenient for.

The present invention may be further configured in a preferred embodiment as: a mixing pipe is communicated between the SCR catalyst and the particulate filter, a urea pump and a urea tank containing urea aqueous solution are fixed in the shell, a urea supply pipe and a urea return pipe are communicated between the urea pump and the urea tank, and the urea supply pipe is connected with a heater; and a urea injection pipe is communicated between the mixing pipe and the urea pump, and a metering nozzle is fixed at one end of the urea injection pipe communicated with the mixing pipe.

Through adopting above-mentioned technical scheme, adopt urea as the reductant, with the urea aqueous solution in the urea case, heat the decomposition for ammonia and carbon dioxide with urea aqueous solution in the urea pump through urea supply pipe input simultaneously, rethread urea injection pipe and measurement nozzle inject ammonia and carbon dioxide and get into in the hybrid tube, rethread ammonia and oxygen are to nitric oxide and nitrogen dioxide reduction, make tail gas discharge nitrogen and vapor, avoid causing the pollution and cause the injury to the human body to the environment.

The present invention may be further configured in a preferred embodiment as: a plurality of baffles which are arranged at intervals along the length direction of the shell are arranged in the SCR catalyst, and a catalyst plate is fixed on the side wall of each baffle, which faces the air inlet; the baffle is provided with a channel for smoke to pass through, and the channel comprises a plurality of micropores arranged on the baffle; the channels on the baffle plates are arranged in a staggered mode along the length direction of the shell.

By adopting the technical scheme, the flue gas and ammonia gas contact the catalyst on the surface of the baffle plate, and the reaction is accelerated under the action of the catalyst, so that the nitric oxide and nitrogen dioxide in the flue gas are reduced; the use amount of the catalyst is increased by arranging a plurality of baffles, so that the catalytic reduction reaction is ensured to be carried out; and when the flue gas needs to be discharged, the flue gas must be discharged through the channels, and the flow path of the flue gas is prolonged through the channels which are arranged in a staggered mode, so that the reaction time of the flue gas in the catalytic converter is prolonged, the nitric oxide and the nitrogen dioxide in the flue gas are fully reacted, and the purification degree of the flue gas is improved.

The present invention may be further configured in a preferred embodiment as: the side wall of the shell is hinged with a movable door, an air inlet is formed in the movable door, flanges are fixed at two ends of the particulate filter, the flange at one end is connected with the mixing pipe, the flange at the other end is connected to the part, corresponding to the air inlet, of the inner wall of the shell, and the air guide pipe is communicated with the particulate filter through the air inlet; the parts of the side walls of the two sides of the shell, which correspond to the particulate filter, are respectively hinged with a first access door and a second access door.

By adopting the technical scheme, after the SCR catalyst and the particulate filter in the shell are connected, the movable door is closed, and the flange at the end part of the particulate filter is fixed on the inner wall of the movable door through the first access door and the second access door; finally, the end part of the air duct is fixed on the surface of the movable door, so that the air duct is communicated with the particulate filter; and the part inside the shell can be periodically overhauled through the first access door and the second access door.

The present invention may be further configured in a preferred embodiment as: the air guide pipe comprises a first air guide pipe positioned in the box body and a second air guide pipe positioned outside the box body and communicated with the first air guide pipe, and the second air guide pipe is a corrugated pipe; the inner wall of the particulate filter is fixed with a plurality of groups of positioning blocks at intervals along the length direction of the particulate filter, each group of positioning blocks comprises two positioning blocks, a gap for embedding the edge of the filter plate is arranged between the two positioning blocks, and the edge of the filter plate is provided with a notch for the positioning blocks to pass through.

By adopting the technical scheme, after the purification system is used for a period of time, more particles are adsorbed in the particulate filter to cause blockage, so that the exhaust speed of the flue gas is reduced; at the moment, the particle filter and the movable door are detached through the first access door and the second access door, then the movable door can be opened through the self contractibility of the corrugated pipe, one end of the particle filter extends into the movable door, the filter plate is rotated to enable the notch of the filter plate to be aligned with the positioning block, and the filter plate can be detached from the filter for cleaning; after the washing is accomplished, inwards push the notch alignment locating piece of filter again, lie in between the locating piece of same group to the filter, rotate the filter again, make the edge embedding of filter between the locating piece of same group, accomplish the installation of filter.

The present invention may be further configured in a preferred embodiment as: the box and the casing are both arranged in a double-layer structure with sound-absorbing cotton embedded in the middle, and the first air duct sleeve is provided with a silencer.

By adopting the technical scheme, when the engine and the cooling fan operate, large exhaust noise and exhaust noise can be generated, and most of the noise can be absorbed by the sound-absorbing cotton of the shell and the box body; and exhaust noise is absorbed by the silencer on the air duct.

The present invention may be further configured in a preferred embodiment as: a support is fixed at the bottom of the shell, and a universal wheel with a locking device is fixed at the bottom of the support; and a support which is respectively supported on the particulate filter, the mixing pipe and the side wall of the SCR catalyst is fixed in the shell.

Through adopting above-mentioned technical scheme, be convenient for the dismantlement operation of filter, with the directive wheel unblock back to the flexible characteristic of bellows, can push away purification system from the box, make to have the dismantlement of the filter of being convenient for of sufficient distance between casing and the box. When one end of the particle filter is separated from the movable door, the support can support the particle filter, so that the stability of the particle filter is maintained, and the filter plate is convenient to detach.

To sum up, the utility model discloses a following at least one useful technological effect:

1. the device is provided with a particulate filter and an SCR (selective catalytic reduction) catalyst, and the filter is arranged in the filter, so that the effect of eliminating black smoke is achieved; the catalytic reaction is carried out under the action of the catalyst in the SCR catalyst, the nitrogen monoxide and the nitrogen dioxide are reduced into nitrogen gas and water, the toxic gas in the tail gas is prevented from being discharged into the atmosphere, namely, the double purification of filtering and catalytic reduction is realized through a particulate filter and the SCR catalyst, and the purification degree of the flue gas is improved;

2. the particle filter is provided with a plurality of filter plates with different pore diameters, particles contained in the tail gas are filtered step by step through the filter plates with gradually reduced filter hole diameters, the smoke can be effectively filtered, and the effect of eliminating black smoke is achieved; the SCR catalyst is internally provided with a plurality of baffles, and the baffles prolong the flow path of the flue gas by the staggered channels, thereby prolonging the reaction time of the flue gas in the catalyst, leading the nitric oxide and the nitrogen dioxide in the flue gas to be fully reacted and improving the purification degree of the flue gas;

3. through the notch and the setting of locating piece between dodge gate, bellows and filter and the particulate filter, make filter dismouting easy operation to the clearance of filter.

Drawings

Fig. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a schematic structural diagram of the interior of the case and the interior of the housing of the present invention;

fig. 3 is a schematic view of the housing structure of the present invention;

FIG. 4 is a schematic diagram of the internal structure of the particulate filter and SCR catalyst of the present invention;

fig. 5 is an enlarged view of fig. 4 at a.

In the figure, 1, a power generation system; 2. a purification system; 3. an air duct; 11. a box body; 111. sound-absorbing cotton; 12. an oil tank; 13. a heat radiation fan; 14. an engine; 15. a generator; 16. a controller; 21. a housing; 211. a support; 212. a support; 213. a universal wheel; 214. a movable door; 2141. an air inlet; 215. an exhaust port; 216. a first access door; 217. a second access door; 22. a particulate filter; 221. a filter plate; 2211. filtering holes; 2212. a notch; 222. positioning blocks; 23. an SCR catalyst; 231. a baffle plate; 232. a catalyst plate; 233. a channel; 234. micropores; 24. a mixing tube; 26. a urea pump; 261. a urea supply pipe; 262. a urea return pipe; 263. a heater; 27. a urea tank; 28. a urea injection pipe; 281. a metering nozzle; 29. a tail pipe; 31. a first air duct; 311. a muffler; 32. a second air duct; 33. and (4) a flange.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Referring to fig. 1 and 2, for the utility model discloses a diesel generating set with tail gas purification function, including power generation system 1 and the clean system 2 that communicates in power generation system 1, power generation system 1 includes box 11 and is fixed in inside oil tank 12, cooling fan 13, engine 14, generator 15 and the controller 16 of box 11. The purification system 2 comprises a shell 21, and a particulate filter 22 and an SCR catalyst 23 which are fixed in the shell 21, wherein a mixing pipe 24 is communicated between the particulate filter 22 and the SCR catalyst 23, and a gas guide pipe 3 which penetrates through a box body 11 is communicated between the particulate filter 22 and the engine 14. A support 211 respectively supported on the side walls of the particulate filter 22, the mixing pipe 24 and the SCR catalyst 23 is fixed in the housing 21, and the case 11 and the housing 21 are both of a double-layer structure in which sound-absorbing cotton 111 is embedded in the middle, wherein a bracket 212 is fixed at the bottom of the housing 21, and a universal wheel 213 with a locking device is fixed at the bottom of the bracket 212.

Referring to fig. 2 and 3, a movable door 214 is hinged to a side wall of the housing 21, the movable door 214 is opened with an air inlet 2141, and the housing 21 is opened with an air outlet 215 opposite to the side wall of the movable door 214. The gas guide pipe 3 comprises a first gas guide pipe 31 positioned inside the box body 11 and a second gas guide pipe 32 positioned outside the box body 11, the first gas guide pipe 31 is communicated with the second gas guide pipe 32, and the first gas guide pipe 31 is sleeved with a silencer 311; the second air duct 32 is a bellows, and a flange 33 is fixed to an end of the bellows, and the flange 33 at the end of the bellows is fixed to a portion of the surface of the movable door 214 corresponding to the air inlet 2141 by bolts. Flanges 33 are fixed to both ends of the particulate filter 22, the flange 33 at one end of the particulate filter 22 is connected to the mixing pipe 24, and the flange 33 at the other end is connected to the second gas-guide pipe 32 by bolts, so that the second gas-guide pipe 32 is communicated with the particulate filter 22 through the gas inlet 2141. The side walls of the two sides of the housing 21 are respectively hinged with a first access door 216 and a second access door 217 corresponding to the parts of the particulate filter 22.

Referring to fig. 4, a plurality of filter plates 221 are installed in the particulate filter 22, and a plurality of filter holes 2211 are formed in the filter plates 221 such that the diameters of the filter holes 2211 of the filter plates 221 gradually decrease from the inlet 2141 to the outlet 215. A plurality of sets of positioning blocks 222 are fixed on the inner wall of the particulate filter 22 at intervals along the length direction of the particulate filter 22, each set of positioning blocks 222 includes two positioning blocks 222, the gap between the two positioning blocks 222 is used for the edge of the filter plate 221 to be embedded, and the edge of the filter plate 221 is provided with a notch 2212 for the positioning block 222 to pass through. When the particulate filter 22 needs to be cleaned after the purification system 2 is used for a certain period of time, the particulate filter 22 is bolted to the movable door 214 through the first access door 216 and the second access door 217, and then the movable door 214 can be opened by the contractibility of the bellows itself; then, the filter plate 221 is inserted into the particulate filter 22, and the filter plate 221 is rotated to align the notch 2212 of the filter plate 221 with the positioning block 222, so that the filter plate 221 can be detached from the filter for cleaning; after cleaning, the notch 2212 of the filter plate 221 is aligned with the positioning blocks 222 and pushed inwards, the filter plate 221 is pushed to be located between the same group of positioning blocks 222, and then the filter plate 221 is rotated, so that the edge of the filter plate 221 is embedded between the same group of positioning blocks 222, and the filter plate 221 is mounted.

A urea pump 26 and a urea tank 27 containing urea aqueous solution are fixed in the housing 21, a urea supply pipe 261 and a urea return pipe 262 are communicated between the urea pump 26 and the urea tank 27, and the urea supply pipe 261 is connected with a heater 263; a urea injection pipe 28 is connected between the mixing pipe 24 and the urea pump 26, and a metering nozzle 281 is fixed to one end of the urea injection pipe 28 connected to the mixing pipe 24. A plurality of baffle plates 231 arranged at intervals along the length direction of the shell 21 are arranged in the SCR catalyst 23, and honeycomb-shaped catalyst plates 232 are fixed on the side walls of the baffle plates 231 facing the air inlet 2141; the catalyst adopted in this embodiment uses titanium dioxide as a carrier, and vanadium, tungsten and molybdenum are loaded on the carrier as a main catalyst, then catalyst raw materials are uniformly mixed, and are made into a honeycomb cuboid through extrusion molding equipment according to a required aperture, and the cuboid is dried and calcined, and then is cut into honeycomb catalyst monomers with a certain length and is fixed on the baffle 231. The baffle 231 is provided with a channel 233 for smoke to pass through, and the channel 233 comprises a plurality of micropores 234 (refer to fig. 5) arranged on the baffle 231; the passages 233 of the baffle 231 are staggered along the length of the housing 21. Referring to fig. 3 and 4, a flange 33 is fixed to one end of the SCR catalyst 23 near the exhaust port 215, and the flange 33 is connected to the tail pipe 29 by bolts; the SCR catalyst 23 and the tail pipe 29 communicate with an exhaust port 215.

The implementation principle of the embodiment is as follows: when in use, the engine 14, the generator 15 and the cooling fan 13 are started through the controller 16; during operation of the engine 14 harmful fumes are generated, which are led to the cleaning system 2 through the gas duct 3. Harmful flue gas firstly passes through the particulate filter 22, passes through the micropores 234 on the filter plate 221, and filters particles with larger particle size; the filter board 221 with the diameter gradually reduced through the filter holes 2211 filters particles contained in the tail gas step by step, so that the smoke can be effectively filtered, and the effect of eliminating black smoke is achieved.

The gas after particle filtration enters the mixing pipe 24, at this time, the gas is input into the urea pump 26 through the urea supply pipe 261, the urea aqueous solution is heated and decomposed into ammonia gas and carbon dioxide, and the ammonia gas and the carbon dioxide are injected into the mixing pipe 24 through the urea injection pipe 28 and the metering nozzle 281, so that the flue gas and the ammonia gas are fully mixed; the mixed gas enters the SCR catalyst 23, ammonia is used as a reducing agent, and ammonia, oxygen and nitric oxide or ammonia, oxygen and nitrogen dioxide are subjected to catalytic reaction under the action of a catalyst, so that the nitric oxide and the nitrogen dioxide are reduced into nitrogen and water, and the phenomena that the environment is polluted and the human body is damaged due to the emission of the nitric oxide in tail gas into the air are avoided; namely, the double purification of filtration and catalytic reduction is achieved through the particulate filter 22 and the SCR catalyst 23, and the purification degree of the flue gas is improved.

When the reduced flue gas needs to be discharged, the flue gas needs to be discharged through the channel 233, the plurality of baffle plates 231 prolong the flow path of the flue gas through the staggered channels 233, so that the reaction time of the flue gas in the catalytic converter is prolonged, the nitric oxide and the nitrogen dioxide in the flue gas are fully reacted, and the purification degree of the flue gas is improved.

The embodiment of this specific implementation mode is the preferred embodiment of the present invention, not limit according to this the utility model discloses a protection scope, so: all equivalent changes made according to the structure, shape and principle of the utility model are covered within the protection scope of the utility model.

Claims

1. The utility model provides a diesel generating set with tail gas cleanup function which characterized in that: the device comprises a power generation system (1) and a purification system (2) communicated with the power generation system (1), wherein the power generation system (1) comprises a box body (11), an oil tank (12), a heat dissipation fan (13), an engine (14), a power generator (15) and a controller (16), wherein the oil tank (12), the heat dissipation fan (13), the engine (14), the power generator (15) and the controller are fixed in the box body (11); the purification system (2) comprises a shell (21), and a particulate filter (22) and an SCR catalyst (23) which are fixed in the shell (21), wherein the particulate filter (22) is communicated with the SCR catalyst (23), and a gas guide pipe (3) which penetrates through a box body (11) is communicated between the particulate filter (22) and the engine (14).

2. The diesel generator set with the tail gas purification function according to claim 1, wherein: an air inlet (2141) and an air outlet (215) are respectively formed in two sides of the shell (21), one end of the air duct (3) is communicated with the generator (15), and the other end of the air duct is fixed at the position, corresponding to the air inlet (2141), of the shell (21); a plurality of filter plates (221) are installed in the particle filter (22), a plurality of filter holes (2211) are formed in the filter plates (221), and the diameters of the filter holes (2211) from the air inlet (2141) to the air outlet (215) of the filter plates (221) are gradually reduced.

3. The diesel generator set with the tail gas purification function according to claim 2, wherein: a mixing pipe (24) is communicated between the SCR catalyst (23) and the particulate filter (22), a urea pump (26) and a urea tank (27) containing urea aqueous solution are fixed in the shell (21), a urea supply pipe (261) and a urea return pipe (262) are communicated between the urea pump (26) and the urea tank (27), and the urea supply pipe (261) is connected with a heater (263); a urea injection pipe (28) is communicated between the mixing pipe (24) and the urea pump (26), and a metering nozzle (281) is fixed at one end of the urea injection pipe (28) communicated with the mixing pipe (24).

4. The diesel generator set with the tail gas purification function according to claim 3, wherein: a plurality of baffle plates (231) which are arranged at intervals along the length direction of the shell (21) are arranged in the SCR catalyst (23), and a catalyst plate (232) is fixed on the side wall of each baffle plate (231) facing the air inlet (2141); the baffle (231) is provided with a channel (233) for smoke to pass through, and the channel (233) comprises a plurality of micropores (234) arranged on the baffle (231); the passages (233) of the baffle plate (231) are arranged in a staggered manner along the length direction of the shell (21).

5. The diesel generator set with the tail gas purification function according to claim 2, wherein: the side wall of the shell (21) is hinged with a movable door (214), the air inlet (2141) is arranged on the movable door (214), flanges (33) are fixed at two ends of the particulate filter (22), the flange (33) at one end is connected with the mixing pipe (24), the flange (33) at the other end is connected to the part, corresponding to the air inlet (2141), of the inner wall of the shell (21), and the air guide pipe (3) is communicated with the particulate filter (22) through the air inlet (2141); the parts of the side walls of the two sides of the shell (21) corresponding to the particulate filter (22) are respectively hinged with a first access door (216) and a second access door (217).

6. The diesel generator set with the tail gas purification function according to claim 5, wherein: the air duct (3) comprises a first air duct (31) positioned inside the box body (11) and a second air duct (32) positioned outside the box body (11) and communicated with the first air duct (31), and the second air duct (32) is a corrugated pipe; the inner wall of particulate filter (22) is fixed with multiunit locating piece (222) along the length direction interval of particulate filter (22), and every group locating piece (222) includes two locating pieces (222), is provided with the space that supplies filter (221) edge embedding between two locating pieces (222), and the edge of filter (221) is seted up and is supplied notch (2212) that locating piece (222) passed.

7. The diesel generator set with the tail gas purification function according to claim 6, wherein: box (11) and casing (21) all set up to have inlayed the bilayer structure who inhales sound cotton (111) for the middle part, and first air duct (31) cover is equipped with muffler (311).

8. The diesel generator set with the tail gas purification function according to claim 3, wherein: a bracket (212) is fixed at the bottom of the shell (21), and a universal wheel (213) with a locking device is fixed at the bottom of the bracket (212); a support (211) is fixed in the housing (21) and supported on the side walls of the particulate filter (22), the mixing pipe (24) and the SCR catalyst (23).