SE441027B - DEVICE FOR MECHANICAL AND CATALYTICAL CLEANING OF DIESEL ENGINE EXHAUSTS - Google Patents

Description

8001507-6 it is necessary to heat it to a high temperature, which is not only troublesome, but also causes deterioration of the catalytic function, as well as deformation or destruction of the catalyst.

In the above-mentioned conventional device designated (b), on the other hand, the water-operated smoke-washing device can remove the smoke satisfactorily.

However, as a result of the water supply, a large amount of steam is formed, which seriously impedes visibility. Furthermore, difficult maintenance work is required, such as, for example, the devices for supplying washing water and more.

For complete removal of bad odors and harmful components from the exhaust gases, it is necessary that these have a high temperature of between 300 ° C and 500 ° C at the catalyst inlet. In the device denoted by (b), however, the gas temperature is lowered disturbingly when washing the exhaust gases with the water in the flue gas scrubber. For this reason, it is not permitted to install the catalyst on the downstream side of a flue gas scrubber working with water. Accordingly, it is inevitable that the smoke particles adhere to the catalyst, which causes several problems as described in more detail above in connection with the disadvantages of the conventional device designated (a). The object of the present invention is therefore to provide a purification device for diesel engine exhaust gases capable of maintaining high efficiency in exhaust gas purification for a long period of time by safely removing smoke particles by means of a heat-resistant filter arranged on the upstream side of the catalyst bed, whereby the problems described above prior art is overcome. Yet another object of the present invention is to provide a device for purifying exhaust gases from diesel engines, in which the arrangement for combustion and removal of the smoke particles is considerably simplified, which smoke particles are captured by the heat-resistant filter during the passage of the exhaust gases therethrough.

A purification device of the type specified in the preamble of the appended main claim is characterized according to the present invention by the peculiar properties stated in the characterizing part of the claim. In the arrangement according to the invention, few (Û ÉÜ reach CÜ c ... “få f É fi 'are effectively prevented from adhering smoke particles to the catalyst bed as a result of the filtration performed by the heat-resistant filter, whereby good cleaning for a long period of time. The smoke particles, which are captured by the heat-resistant filter, are at the same time easily combustible fl and removable by means of the regeneration device.

The heat-resistant filter of the purification device according to the invention is designed so that the combustion and removal of smoke particles, which are captured by the heat-resistant filter, is feasible even while the exhaust gases flow through the heat-resistant filter. The purification device according to the invention also has a small size.

With reference to the accompanying drawing, various embodiments of the purification device according to the invention are described below by way of example. In the drawing, Fig. 1 is a block diagram of a practically useful such embodiment of the purification device according to the invention, Fig. 2 is a longitudinal section through another embodiment of the exhaust purification device according to the invention, Fig. 3 is a cross section taken along line A - A through the purification device according to fig. 2, and Figs. H and 5 were each their practical embodiment for applying the device according to Figs. 2 and 3, H Figs. 1 illustrates a diesel engine 1 with an exhaust gas purification device according to the invention. The exhaust gases from the diesel engine 1 are supplied to an exhaust gas purification circuit with an inlet end 2, which branches into two branch lines 3, H. At the branch point of the branch lines 5, Ä a reversing damper 5 is arranged, whereby the exhaust gas flow is reversible between the branch lines 3 and Ä depending on the position of the reversing damper 5.

In the branch lines 3, Ä, heat-resistant filters 6 resp. The filters 6, 7 are made of metal fibers with several different fiber diameters, which are selected with regard to the size distribution of the smoke particles. Metal fibers with different fiber diameters are arranged in layers which are so superimposed or laminated that they in their entirety form a substantially non-cylindrical or disc-shaped body. Ü The branch lines 3, H branch in turn into lines Ba, Bb and Ra, Hb respectively. The lines Ba and Äa lead to an outlet end 5, while the lines Bb, Hb are communicatively connected to a catalyst converter 9, the outlet end of which is P05 çïÜ ;; j: ~ --- ~ ._ '. Iaf-IT? I are communicatingly connected to the outlet end 8 of the circuit. At the junction point 8061507-6 between the lines Ba, 3b and between the lines Hb, reversing dampers 10 and 11, respectively, are arranged when operating the lines Ha, nade. The arrangement is so designed, the dampers 10, 11 are the communicable in the circuit reversible first state, in which the branch lines 5, and an intermediate one Ä communicates directly with the outlet end 8 of the circuit, nat state, in which said branch lines are communicated with the catalyst converter 9. The regeneration arrangement for regeneration of the heat-resistant filters 6. and 7 is con- From these branch lines 3 and H separate 13. These regeneration joints- 7 inlet ends.

In a blow-in opening lü, arranged in the middle of a burner 16, a reversing damper 15 is further arranged. The arrangement is designed in such a way that the smoke particles which clog the filters 6, 7 are burned and removed when hot air is supplied to the filters 6, 7 by means of the fan 17. Since the exhaust gases emitted from the diesel engine contain only a small amount of oxygen. very difficult to burn the smoke particles. F1äkten ~ which enables complete destruction as below. separate regeneration lines 12, connections are connected to the filters 6 and E35, respectively, 17 therefore supply external air, burning of the smoke particles.

Pressure drop meters 18, 19 are connected across the heat-resistant filters 6 and 7, respectively. In more detail, this means that the pressure drop meter 18 is connected to the outlet and inlet ends of the filter 6, while the pressure drop meter 19 is connected to the outlet and inlet ends of the filter 7. These pressure drop meters are adapted for measuring the pressure difference or pressure drop across the filters 6, 7, ie the degree of clogging of the filters with smoke particles. An automatic control device (not shown) is provided for automatic reversal of the reversing dampers 5, 10, 11, 15, to enable alternative use of the branch lines 3, H and for automatic start of the burner 16 and the fan 17, whereby hot air is fed into the filters 6, 7 for combustion and removal of the smoke particles adhering to the filters. The automatic control device operates depending on the degree of clogging of the filters 6, 7, which is sensed by the pressure drop meters 18, 19.

With the diesel engine in operation and the dampers 5, 10, 11, 15 8G0í5u? ~ F 5 in the positions illustrated in the figure, the exhaust gases of the diesel engine 1 flow into the branch line 3 through the inlet end 2 of the purge circuit and then flow further through the heat-resistant filter 6 and then reach the catalyst converter 9 via the branch line šb.

The gases are finally released into the atmosphere through the exhaust line 8.

Since the capture of the smoke particles depends on the filtering ability of the filter 6, it should be noted that it is possible to safely capture even comparatively small smoke particles, with the result that the smoke particles accompanying the exhaust gases are completely removed. Harmful components in the exhaust gases, such as carbon monoxide and hydrocarbons, as well as bad odors, on the other hand decompose into harmless carbon dioxide, due to the catalytic oxidizing action carried out by the catalyst in the catalyst converter 9. It is to be noted in this connection that the smoke particles adhesion to the catalyst converter 9 is completely avoided due to the fact that the smoke particles have already been captured and removed from the gas by means of the filter 6, whereby the catalytic effect of the catalyst is maintained for a longer period of time without deterioration.

The adhesion of the flue gas particles to or deposition on the heat-resistant filter 6 becomes visible in the form of an increased pressure drop across the filter 6. This increase is conveniently detected by the pressure drop meter 18, the effect of which entails automatic reversal of the reversing dampers 5, 10, 11, 15. from line 3 to line H and consequently also through the heat-resistant filter 7, so that continuous purification of the gases is possible. At the same time, the burner 16 and the fan 17 for supplying hot air to the filter 6, which has become partially clogged by flue gas particles, are also automatically started, whereby these particles are completely burned and the filter 6 is regenerated for a comparatively short period of time. 6 The gases generated during the regeneration of the filter 6 are blown out directly through the exhaust line 8 via the branch line Ba.

Since the regeneration is completed, the pressure drop across the filter 6 has decreased. This reduction is effectively sensed by the pressure drop meter 18, which in turn emits a signal which stops the burner 16 and the fan 17. In the embodiment described above, the heat-resistant filters are arranged in two parallel lines, in order to enable reversal; between them, so that one line is in use while the other line is regenerated. However, this arrangement is not the only useful one, but it is also possible to make the exhaust gas cleaning device according to the invention smaller in size and more compact by using only one line with a heat-resistant filter and designing the arrangement so that the engine exhaust gases are allowed to flow through this single filter even during regeneration thereof.

Figs. 2 - 5 describe another embodiment of the purification device according to the invention, which has only one line with a heat-resistant filter.

A cylindrical, hollow housing 21 is arranged in the exhaust system of a diesel engine. The inlet 22 for the engine exhaust gases is formed in the peripheral wall of the housing 21 in a portion located near one axial end of the housing, while an exhaust outlet 23 is formed near the other axial end of the housing 21. The housing 21 houses a heat-resistant filter 2Ä, which consists of metal fibers or a similar material and has the shape of a mat or the like and is wound in a spiral to a hollow cylinder. As in the case of the heat-resistant filters 6, 7 of the first described embodiment, the filter 2Ä in this second embodiment is composed of metal fibers with different fiber diameters selected with regard to the size distribution of the smoke particles. The axial end portion of the filter 2ü, which faces the inlet 22, is closed by a lid 25, while the end of the filter facing the outlet 23 is open and communicates with the outlet 23.

A catalytic bed 26 is also arranged in the housing 21.

The catalyst bed 26 consists of a spongy metal catalyst wound in a spiral into a hollow cylinder. The metal catalyst usually consists of platinum or a similar material capable of removing bad odors and harmful exhaust components, such as carbon monoxide and hydrocarbons. The catalyst beds 26 are arranged in the hollow cylindrical filter 2H, more specifically on its downstream side, and the bed lies inside the filter zu.

Near the outlet 23 of the housing 21 a partition 27 is arranged, which separates the inlet 22 and outlet 23 of the housing 21 from each other. The exhaust gases entering the housing 21 through the inlet 22 are therefore allowed to reach the outlet 23 only after passage through the peripheral surfaces of the filter 2fl and the catalyst bed 26. e 7 At the axial end of the housing 21 located next to the inlet 22, a high-pressure burner 28 is arranged airtight. The burner 28 can be actuated depending on the pressure drop across the laminated layer of the filter 2H and the bed 26 or the pressure difference between the inlet 22 and the outlet 23 of the housing 21, i.e. the degree of clogging of the filter 2U, which is sensed by a pressure drop meter (not shown). The high pressure burner 28 is also useful during operation of the diesel engine, i.e. while the exhaust gases flow through the filter 24. For regeneration of the filter 2H, the burner 28 can thus supply hot air to the filter, even if exhaust gas flow through it takes place.

The high pressure burner 28 has an air supply 29 for high pressure air to the combustion. The high pressure burner 28 also has the necessary means to withstand pressure fluctuations in the exhaust gases supplied to the housing 21. Furthermore, a cylindrical heat radiation plate 30 is attached to the burner 28, which is adapted to surround the flame from the burner 28. In the peripheral wall of the plate 30 near its free end, several openings 30a are formed. Insulation 31 is arranged in the housing 21 and fastening means 32 for mounting on the outside of the housing.

Figs. H and 5 illustrate modifications of the second embodiment. In the second embodiment described above, §Qm having only a heat-resistant filter, the device for regenerating the filter 24 is the high-pressure burner 28. In this modification, however, the burner 28 is replaced by a combination of a conventional low-pressure burner and a vacuum generating section formed in the exhaust line. The vacuum generating section, given the reference numeral 33, is formed in the inlet line 3Ä upstream of the housing 21. The section 33 is formed by locally reducing the diameter of the line 3H, as shown in Fig. Ä, or by dividing the inlet line 3fl into two sections, the facing portions of which are formed with different diameters, as shown in fig. 5. The low pressure burner 35 is arranged in the middle of a conduit 36, which is open into the vacuum generating section 33, so that the hot air generated by the burner 35 is supplied to the housing 21 due to the vacuum which develops The gas gas flow through the vacuum generating section 33- The most recently described exhaust gas purifier according to the invention * by 'f' x ': WWW' v. , -. v. Én .aa -... s RÅM fyße ... píivm _. ifïfsfßw-çff- ~ _ 8001507-6 works as follows. When the diesel engine is started, exhaust gases emanating from the engine are supplied to the housing 21 through its inlet 22 and flow through the 2H of the filter and the bed 26.

The exhaust gases are finally blown out through the outlet 23. The flue gas particles entrained by the exhaust gases are safely captured by the heat-resistant filter 24 during the flow of the gas therethrough. Bad odors and harmful components, such as carbon monoxide and hydrocarbons, are also effectively removed by the catalytic action of the catalyst bed 26 as the gas passes through the bed.

Since the exhaust gases of smoke particles have been trapped and completely removed by the filtering action of the filter 24, it is to be noted that unwelcome adhesion of smoke particles to the catalyst bed 26 is completely avoided, so that the catalyst bed has a good catalytic effect for a long period of time. 2 As the amount of filter particles trapped by the filter 2Ä increases, the pressure difference between the inlet 22 and the outlet 23 of the housing 21 increases to a corresponding degree. This increase in pressure difference is detected by the pressure drop meter (not shown). When a predetermined pressure difference is reached, the pressure drop meter gives a signal to start the high pressure burner. Hot air is thereby supplied to the housing 21, whereby the smoke particles trapped by the filter are completely burned and removed, so that the filter 2Ä is regenerated. This causes a reduction in the pressure difference across the housing 21, the detection of which causes the high-pressure burner 28 to stop. The heat radiation plate 30 is in this case red hot as a result of the heating of the burner 28.

Exhaust gases entering through the inlet 22 are blown towards the end portion of the peripheral surface of the plate 30, the gas being heated in a spiral flow around the cylindrical peripheral surface of the plate 30.

The heated air then flows through the filter 2Ä for complete combustion and removal of the smoke particles.

In the device illustrated in Figs. 1 and 5, the pressure drop meter (not shown) detects, as in the case of Fig. 1, the degree of clogging for activating the low pressure burner 35. The hot air generated by the burner is introduced into the housing 21 due to the vacuum generated in section 33, whereby all smoke particles captured by the filter 2H are completely burned and removed. In summary, the present invention provides a small size device for purifying exhaust gases emitted from diesel engines, which device has a high cleaning ability, is easy to maintain, is useful in various types of diesel engines, such as engines mounted in construction equipment and conventional vehicles, such as buses and lorries, as well as stationary diesel engines. . .-....._......_ .., .._._._._ .. ~ _..__._.._.-._. I _ _..- -_>, _ -..__ _

Claims (6)

8--061507-6 Patent claims Device for mechanical and catalytic purification of diesel engine exhaust gases, with an exhaust purification line (3, Ä, 21) to which the exhaust gases from the diesel engine (1) are supplied, a pre-separation device (6, 7, 2N) fitted in the line for to capture smoke particles contained in the exhaust gases and a catalytic converter (9, 26) in the line downstream of the pre-separation device to eliminate bad odor and harmful components in the exhaust gases, characterized in that the pre-separation device as in and for is known to consist of at least one heat-resistant filter (6, 7, 2%), that a regeneration device (16, 17, 28-30) is arranged in connection with this filter, and that the catalyst in the converter (9, 26) is constituted of porous metal arranged in wall form, the filter wall being applied substantially parallel to the longitudinal direction of the line to allow a large flow area in relation to the area of the line and thus slow exhaust gas flow through the converter. Purification device according to claim 1, characterized in that the exhaust gas purification line just after the engine (1) divides into two branch lines (3, 4) which reconnect before the catalyst converter (9), that a reversing device (5) is arranged at the dividing point and each branch line each have their own heat-resistant filter (6, 7), that a further line (12) with a further reversing device (15) connects the regenerator (16, 17) to either of the branch lines (3, Ä). in the vicinity of the corresponding filter (6, 7), that each branch line (3, U) downstream of the corresponding filter each has its own bypass line (Ba, Na) with switching device (10, 11) for bypassing the catalyst converter ( 9), whereby one branch line (3, Bb, U, Hb) is useful for exhaust gas cleaning while the other branch line (H, Ha, 3, Ba) is useful for regenerating the filter of the latter line (7, 6) by corresponding setting of the switching devices (5, 10, 11, 15) . Purification device according to claim 1, characterized in that the exhaust gas purification line is formed by a cylindrical jacket (21) with an inlet (22) at one end of the jacket and an outlet (23 at the other, and with a main flow direction in the jacket coaxial, etc. mantelns centrumaxel., _ __, .... g - l iiy / -f * - 8061507-6 11 H. Purification device according to claim 3, characterized in that both the heat-resistant filter (ZU) and the catalyst converter (26) are in the form of a hollow cylinder and are laminated with each other to a common hollow cylinder arranged near the outlet (21) of the jacket (21). 23), the filter catalyst hollow cylinder (2A, 26) being arranged so as to allow the exhaust gases to flow through it substantially radially and through the filter before the catalyst. Purification device according to one or more of Claims 1 to H, characterized in that the heat-resistant filter (6, 7, 2Ä} consists of metal fibers with different fiber diameters. Purification device according to one or more of Claims 1 to 5, characterized in that the heat-resistant filter (6, 7, ZH) is formed with a pressure indicator (18, 19) which detects the pressure difference across the filter, and that the switching on and off of the regeneration device (16, 17, 28-30) is controlled by the pressure indicator at predetermined upper resp. lower pressure drop limits.