JP6000506B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust emission control device.

  Conventionally, a diesel engine is equipped with a selective reduction catalyst having a property of selectively reacting NOx with a reducing agent even in the presence of oxygen in the middle of an exhaust pipe through which exhaust gas flows, and the selective reduction catalyst A required amount of a reducing agent is added to the upstream side of the catalyst so that the reducing agent undergoes a reduction reaction with NOx (nitrogen oxide) in the exhaust gas on the selective catalytic reduction catalyst, thereby reducing the NOx emission concentration. There is what I did.

On the other hand, in the field of industrial flue gas denitration treatment in plants and the like, the effectiveness of a method for reducing and purifying NOx using ammonia (NH ₃ ) as a reducing agent is already widely known. Since it is difficult to ensure safety with respect to traveling with ammonia itself, in recent years, the use of non-toxic urea water as a reducing agent has been studied (see, for example, Patent Document 1). .

That is, if urea water is added to the exhaust gas upstream of the selective catalytic reduction catalyst, the urea water in the exhaust gas is thermally decomposed into ammonia and carbon dioxide gas by the following formula, and the exhaust gas is exhausted on the selective catalytic reduction catalyst. NOx is reduced and purified well by ammonia.
[Chemical 1]
(NH ₂ ) ₂ CO + H ₂ O → 2NH ₃ + CO ₂

  As shown in FIG. 11, as a conventional technique for adding urea water 3 to the exhaust gas 2 on the upstream side of the selective catalytic reduction catalyst 1, the nozzle portion 4 a of the urea water addition device 4 is connected to the axial center of the exhaust flow path 5. It is known that the urea water 3 is added to the center of the flow of the exhaust gas 2 by inserting it to the vicinity. However, in this case, the nozzle portion 4a of the urea water addition device 4 causes the flow of the hot exhaust gas 2 to flow. Since it will be exposed directly, the durability of the urea water addition apparatus 4 is considered uneasy.

  For this reason, as shown in FIG. 12, an injection port 6 that obliquely branches upstream is provided on the side surface of the exhaust passage 5, and the urea water addition device 4 is attached to the injection port 6 from the outside of the exhaust passage 5. Then, it has been studied to add the urea water 3 while facing the exhaust flow path 5 and protecting the urea water adding device 4 from being directly exposed to the flow of the hot exhaust gas 2.

JP 2005-273614 A

  However, when the urea water 3 is added to the exhaust gas 2 in the form of FIG. 11 or FIG. 12, if the amount of urea water 3 added is increased in order to obtain a higher NOx purification performance than before, urea water that cannot be completely vaporized is obtained. 3 adheres (or intervenes) to the inner peripheral surface of the exhaust flow path 5 to form a flow, and there is a possibility that rapid progress of corrosion may be induced by a substance generated by the chemical reaction of the urea water 3. In particular, in the type in which the urea water 3 is injected from the injection port 6 formed on the side surface of the exhaust passage 5 as shown in FIG. 12, the spray of the urea water 3 is easily affected by the flow of the exhaust gas 2, and the exhaust passage 5 Since it is easy to form a biased flow along the inner peripheral surface, it is difficult for the urea water 3 to vaporize, and it is easy to intervene in the inner peripheral surface of the exhaust flow path 5, and corrosion is easily induced.

  Further, in the known urea water adding apparatus 4 as shown in FIG. 11, the urea water 3 is mixed with air and guided to the nozzle portion 4a in a gas-liquid mixed state, and then the urea water 3 is added by an injection system with air assist. However, in order to reduce the cost by omitting the air piping, when an airless type injection method in which the urea water 3 is injected under pressure without air assist is employed, air is contained in the added urea water 3. Therefore, the oxygen concentration on the surface of the stainless steel constituting the exhaust passage 5 is likely to be lowered, the surface of the stainless steel is difficult to passivate, the corrosion resistance is lowered, and the urea water 3 is added. Corrosion is more likely to occur.

  In addition, when a particulate filter that collects particulates in the exhaust gas 2 is provided on the upstream side of the selective catalytic reduction catalyst 1 via the exhaust passage 5, the NOx concentration during regeneration of the particulate filter is provided. It is necessary to increase the amount of urea water 3 added in order to cope with the increase and to cool the urea water addition device 4, and the exhaust temperature increases due to the combustion of the particulates collected in the particulate filter. As a result, the chemical reaction of the urea water 3 is activated and the corrosion rate is increased, so that corrosion due to the addition of the urea water 3 is more likely to occur.

  Therefore, in consideration of the direction of future increase in the amount of urea water 3 added, adoption of an airless type injection method, and combined use of a particulate filter, corrosion due to the addition of urea water 3 occurred in the exhaust passage 5. However, in the present situation, if corrosion due to the addition of urea water 3 occurs in the exhaust passage 5, the entire exhaust passage 5 must be replaced. There is a problem that a large part replacement cost is required because the various members that have been removed or are integrally assembled to the exhaust passage 5 by welding or the like must be replaced together.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust emission control device that can suppress the parts replacement cost to the minimum necessary even when corrosion due to the addition of urea water occurs.

The present invention relates to a selective reduction catalyst that reacts NOx contained in exhaust gas with ammonia, an exhaust passage that guides the exhaust gas to the selective reduction catalyst, and an exhaust passage that is provided in the middle of the exhaust passage. A urea water addition means that employs an airless type injection system that pressurizes and injects urea water, and the inner peripheral surface over the required range near the urea water addition position in the exhaust flow path by a removable covering piece Exhaust purification characterized in that the covering piece is configured so that the covering piece can be appropriately replaced, and the covering piece is made of a material having a higher corrosion resistance to a substance generated by addition of urea water than the exhaust passage. It is also related to the device.

  Thus, in this way, when the amount of urea water added is increased in order to improve the NOx purification performance, urea water that cannot be vaporized adheres to the inner wall in the required range near the urea water addition position. Even if corrosion occurs, the inner peripheral surface of the exhaust passage in this range is covered with a removable covering piece, so that the corrosion extends only to the covering piece and the exhaust passage side is protected. The corrosion site can be repaired simply by removing the coated piece in which corrosion has occurred and replacing it with a new one.

Furthermore, in the present invention, the covering piece is made of a material having higher corrosion resistance to the substance generated by the addition of urea water than the exhaust passage, so that the progress of corrosion in the covering piece is slowed and the covering piece is replaced. The frequency can be greatly reduced.

  According to the exhaust emission control device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, even if corrosion occurs due to the addition of urea water, the corrosion site can be repaired simply by removing the coated piece and replacing it with a new one. Therefore, the parts replacement cost per time required for repairing the corrosion site can be suppressed to the minimum necessary.

According to the invention described in claim 1, (II) the present invention can be lowered significantly replacement frequency of slow to cover pieces of progress of corrosion in the coating pieces, with long-term use of increase depending on the frequency of replacement The parts replacement cost can be greatly reduced.

It is sectional drawing which shows the reference example of this invention. It is the schematic which shows the example of the exhaust gas purification device of S character arrangement. It is sectional drawing which shows another reference example of this invention. It is the schematic which shows the example of the exhaust gas purification apparatus of U shape arrangement | positioning. It is the schematic which shows the example of the exhaust gas purification apparatus of L character arrangement | positioning. It is the schematic which shows the example of the exhaust gas purification apparatus of an in-line arrangement | positioning. It is sectional drawing which shows an example of the form which implements this invention. It is sectional drawing which shows another example of a form of this invention. It is sectional drawing which shows another example of a form of this invention. It is sectional drawing which shows another example of a form of this invention. It is sectional drawing which shows an example of the conventional exhaust gas purification apparatus. It is sectional drawing which shows another example of the conventional exhaust gas purification apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a reference example of the present invention, and the same reference numerals as those in FIGS. 11 and 12 denote the same components.

  As shown in FIG. 1, in this reference example, a required range in the vicinity of the addition position of the urea water 3 in the exhaust passage 5 is divided as a detachable divided piece 5a, and the divided piece 5a can be appropriately replaced. In the case of the example shown here, the flange portion 5b is provided at the front and rear ends of the divided piece 5a, and the flange portion is also provided at the connection end of the upstream and downstream exhaust passages 5. 5c is provided, and a structure in which these flange portions 5b and 5c are detachably fastened with bolts 5e and nuts 5f via gaskets 5d is adopted.

  Further, a urea water addition device 4 adopting an airless type injection system in which an injection port 6 that branches obliquely toward the upstream side is provided on the side surface of the divided piece 5 a and the urea water 3 is injected under pressure to the injection port 6. Is attached from the outside.

  FIG. 2 shows an example in which the structure of FIG. 1 is specifically applied. In the example shown here, the selective reduction catalyst 1 and the particulate filter 7 are held by casings 8 and 9, respectively. Arranged in parallel, the outlet side end of the particulate filter 7 and the inlet side end of the selective catalytic reduction catalyst 1 are connected by the exhaust flow path 5 and discharged from the outlet side end of the particulate filter 7. The exhaust gas purification device having an S-shaped configuration in which the exhaust gas 2 is folded in the opposite direction and introduced into the inlet side end portion of the adjacent selective catalytic reduction catalyst 1 is used as a target. The structure of FIG. 1 is applied.

  In the example shown here, an oxidation catalyst 10 that oxidizes unburned fuel in the exhaust gas 2 is provided in the front stage in the casing 9 in which the particulate filter 7 is held, A rear stage in the casing 8 in which the selective catalytic reduction catalyst 1 is held is equipped with an ammonia reduction catalyst 11 for oxidizing excess ammonia.

  Thus, in this way, when the amount of urea water 3 added is increased in order to improve the NOx purification performance, the urea water 3 that cannot be completely vaporized is within the required range near the urea water 3 addition position. Even if it adheres to the surface and causes corrosion, the exhaust passage 5 in this range is divided and configured as a detachable divided piece 5a. Therefore, the divided piece 5a is divided into bolts 5e and nuts 5f of the flange portions 5b and 5c. It is possible to repair the corroded area simply by unfastening and removing it and replacing it with a new one.

  Therefore, according to the above reference example, even if the corrosion due to the addition of the urea water 3 occurs, only the split piece 5a is removed by unfastening the flanges 5b and 5c with the bolts 5e and nuts 5f and replaced with a new one. Since the corrosion site can be repaired only by this, the parts replacement cost per time required for repairing the corrosion site can be minimized.

  Further, the divided piece 5a can be made of a material having a higher corrosion resistance to the substance generated by the addition of the urea water 3 than the remaining part of the exhaust passage 5 excluding the divided piece 5a. In this case, the progress of corrosion in the divided piece 5a is slowed down, so that the replacement frequency of the divided piece 5a can be greatly reduced, and the part replacement cost in the long-term use that increases according to the replacement frequency can be greatly reduced. it can.

  In the above description, the case where the urea water 3 is added from the middle of the straight extension portion A of the exhaust passage 5 in the S-arranged exhaust gas purification apparatus of FIG. 2 has been described. When the urea water 3 is added from the corner portion B of the exhaust passage 5 in the purifier, a split piece 5a bent into an elbow shape may be used as shown in FIG. 3, and the middle portion of the split piece 5a is used. Is provided with an injection port 6 that protrudes along the axis of the downstream exhaust flow channel 5 and away from the downstream exhaust flow channel 5, and the urea water addition device 4 is connected to the exhaust flow channel with respect to the injection port 6. 5 may be attached from the outside.

  Further, the layout of the exhaust gas purification apparatus equipped with the particulate filter 7 upstream of the selective catalytic reduction catalyst 1 is a U-shaped arrangement as shown in FIG. 4 in addition to the S-shaped arrangement as shown in FIG. In addition, when the urea water 3 is added from the straight extension portion A of the exhaust passage 5 in the U-arranged exhaust purification device of FIG. 4, the structure of FIG. When the urea water 3 is added, the structure of FIG. 3 may be applied.

  Further, if the layout of the exhaust gas purification device equipped with the particulate filter 7 upstream of the selective catalytic reduction catalyst 1 is L-shaped as shown in FIG. 5, the exhaust flow in the L-shaped exhaust gas purification device of FIG. The structure of FIG. 1 is applied when the urea water 3 is added from the straight extension portion A of the path 5, and the structure of FIG. 3 is applied when the urea water 3 is added from the corner portion B of the exhaust flow path 5. It ’s fine.

  If the layout of the exhaust purification device equipped with the particulate filter 7 upstream of the selective catalytic reduction catalyst 1 is in-line arrangement as shown in FIG. 6, the exhaust flow path 5 in the in-line arrangement exhaust purification device of FIG. The structure shown in FIG. 1 may be applied to the straight extension portion A.

  Further, the above has described an example in which the required range near the addition position of the urea water 3 in the exhaust flow path 5 is divided as a detachable divided piece 5a, and the divided piece 5a can be appropriately replaced. However, in the example of carrying out the present invention shown in FIG. 7, the inner peripheral surface over the required range in the vicinity of the addition position of the urea water 3 in the exhaust passage 5 is covered with a detachable covering piece 5g. 5 g can be appropriately exchanged.

  That is, in the case of the example shown in FIG. 7, the exhaust flow path 5 is divided into the front and the rear on the upstream side near the addition position of the urea water 3, and the covering piece 5g is moved downstream from the divided end of the exhaust flow path 5. The flange portion 5h provided at the end of the covering piece 5g on the side opposite to the insertion side can be covered with the split end of the exhaust passage 5 so that the inner peripheral surface of the exhaust passage 5 can be covered. The flanges 5b and 5c provided are sandwiched together with the gasket 5d and are detachably fastened by bolts 5e and nuts 5f.

  In the case of the embodiment shown in FIG. 7, there is a risk of corrosion at the injection port 6, so that a small covering piece 5 j is placed in the injection port 6 from the mounting side of the urea water addition device 4. It can be inserted in the injection direction to cover the inner peripheral surface of the injection port 6, and the flange portion 5k provided at the end of the small covering piece 5j on the side opposite to the insertion side is added with the urea water. The device 4 is sandwiched between the mounting bracket 12 of the apparatus 4 and the flange portion 6a of the injection port 6 together with the gasket 6b, and is detachably fastened by a fastener (not shown).

  The covering piece 5g is provided with an opening 5i that matches the opening position of the injection port 6 when the covering piece 5g is mounted, and the injection port 6 is not blocked by the mounting of the covering piece 5g. It is like that.

Further, the covering pieces 5g and 5j are made of a material having higher corrosion resistance to the substance generated by adding the urea water 3 than the exhaust passage 5, so that the progress of corrosion in the covering pieces 5g and 5j is delayed. It is.

  Thus, in this way, when the amount of urea water 3 added is increased in order to improve the NOx purification performance, the urea water 3 that cannot be completely vaporized is within the required range near the urea water 3 addition position. Even if the inner surface of the exhaust passage 5 in this range is covered with the detachable coating piece 5g, the corrosion extends only to the coating piece 5g even if the corrosion occurs due to the corrosion. The side will be protected, and it becomes possible to repair the corroded area simply by removing the coated piece 5g where the corrosion has occurred and replacing it with a new one.

  Further, the inner peripheral surface of the injection port 6 in the exhaust passage 5 is also covered with the small coating piece 5j, so that the inner peripheral surface of the injection port 6 is protected, so that the coated piece 5j in which corrosion has occurred. The corrosion site can be repaired simply by removing and replacing it with a new one.

  Therefore, according to the above embodiment, even if corrosion due to the addition of the urea water 3 occurs, the corrosion site can be repaired by removing only the covering pieces 5g and 5j and replacing them with new ones. It is possible to suppress the parts replacement cost per one time required for repairing to the minimum necessary.

Further, since the covering pieces 5g and 5j are made of a material having higher corrosion resistance against the substance generated by adding the urea water 3 than the exhaust passage 5 , the progress of corrosion in the covering pieces 5g and 5j is delayed. Thus, the replacement frequency of the covering pieces 5g and 5j can be greatly reduced, and the part replacement cost in the long-term use that increases according to the replacement frequency can be greatly reduced.

  Further, FIG. 8 shows that the exhaust flow path 5 is divided into the front and rear sides near the addition position of the urea water 3, and the covering piece 5 g is inserted from the divided end of the exhaust flow path 5 toward the upstream side to exhaust the exhaust flow path 5. 7 is a configuration example that can cover the inner peripheral surface of the case, and it is substantially the same as the structure of FIG. 7 except that the direction of the insertion direction is reversed. In addition, the same operational effects as the above-described embodiment of FIG. 7 can be obtained.

  7 and FIG. 8 described above, the exhaust flow path 5 in the exhaust purification device of the S-shaped arrangement of FIG. 2, the U-shaped arrangement of FIG. 4, the L-shaped arrangement of FIG. 5, and the in-line arrangement of FIG. Although the case where the urea water 3 is added from the middle of the straight extension portion A is shown as an object, the exhaust gas in the exhaust purification apparatus having the S-shaped arrangement in FIG. 2, the U-shaped arrangement in FIG. 4, and the L-shaped arrangement in FIG. When the urea water 3 is added from the corner portion B of the flow path 5, as shown in FIG. 9, the exhaust flow path 5 is divided into front and rear at the end of the corner portion B of the exhaust flow path 5. It is only necessary to insert the covering piece 5g from the divided end 5 toward the upstream side so as to cover the inner peripheral surface of the exhaust flow path 5, and in the same manner as in the embodiment of FIGS. A small covering piece 5j is also inserted into the urea water adding device 4 from the side where the urea water adding device 4 is mounted in the injection direction of the urea water 3, and the inside of the injection port 6 is inserted. The surface may be so as to cover.

  Further, in the exhaust gas purification apparatus having the S-shape arrangement as shown in FIG. 2, the structure of the exhaust flow path 5 where the exhaust gas 2 discharged from the outlet end portion of the particulate filter 7 is folded in the reverse direction. However, as shown in FIG. 10, the gas collecting chamber 5m that collects the exhaust gas 2 immediately after exiting from the outlet end of the particulate filter 7 while changing the direction in a substantially perpendicular direction, and the gas collecting chamber 5m The exhaust gas 2 is assembled with an exhaust pipe 5p that extracts the exhaust gas 2 through the opening 5n in the direction opposite to the exhaust flow of the particulate filter 7, and the exhaust pipe 5p is located at the center of the inlet side end of the exhaust pipe 5p. In the case where the urea water addition device 4 is equipped toward the outlet end side, it is costly to replace the entire assembly as a divided piece. In the case of structures that can not be divided by location, requires to exchange parts are smaller preferable to use a coating pieces 5g as described in FIGS. 7 to 9, it can be said that preferable in achieving a significant reduction in cost.

  That is, in the case of FIG. 10, the covering piece 5g is inserted from the split end of the exhaust pipe 5p toward the upstream side so that the inner peripheral surface of the exhaust pipe 5p is covered to the entrance end of the exhaust pipe 5p. In this case, the covering piece 5g may be cut out at a portion corresponding to the opening 5n so that the opening 5n is not blocked by the attachment of the covering piece 5g.

  Note that the exhaust emission control device of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Selective reduction type catalyst 2 Exhaust gas 3 Urea water 4 Urea water addition apparatus (urea water addition means)
4a Nozzle part 5 Exhaust flow path 5a Split piece 5b Flange part 5c Flange part 5d Gasket 5e Bolt 5f Nut 5g Covering piece 5h Flange part 5i Opening part 5j Covering piece 5k Flange part 5m Gas collection chamber 5n Opening part 5p Exhaust pipe 6 Port 6a Flange 6b Gasket 7 Particulate Filter 8 Casing 9 Casing 10 Oxidation Catalyst 11 Ammonia Reduction Catalyst 12 Mounting Bracket

Claims (1)

A selective reduction catalyst that reacts NOx contained in the exhaust gas with ammonia, an exhaust passage that guides the exhaust gas to the selective reduction catalyst, and urea water is provided in the exhaust gas that is provided in the middle of the exhaust passage. Urea water addition means adopting an airless type injection system for pressure injection, and covering the inner peripheral surface over a required range in the vicinity of the urea water addition position in the exhaust flow path with a removable covering piece, An exhaust purification apparatus characterized in that the covering piece can be appropriately replaced, and the covering piece is made of a material having a higher corrosion resistance to a substance generated by addition of urea water than the exhaust passage .

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