JP5593139B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus in which a countermeasure for freezing urea water supplied as a reducing agent to a selective catalytic reduction catalyst for reducing and purifying NOx is taken.

  Conventionally, diesel engines are equipped with a selective reduction catalyst (selective reduction catalyst) that has the 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. The required amount of reducing agent is added to the upstream side of the selective catalytic reduction catalyst, and the reducing agent is subjected to a reduction reaction with NOx (nitrogen oxide) in the exhaust gas on the selective catalytic reduction catalyst, whereby NOx emission concentration There is one that can reduce the above.

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.

  That is, if urea water is added to the exhaust gas upstream of the selective catalytic reduction catalyst, the urea water is decomposed into ammonia and carbon dioxide under a temperature condition of about 170 ° C. or higher, and the exhaust gas is exhausted on the selective catalytic reduction catalyst. The NOx contained therein is reduced and purified well by ammonia.

  When urea water is used as a reducing agent in this way, urea water is sent from the urea water tank mounted on the vehicle to the upstream side of the selective catalytic reduction catalyst via the urea water supply line. Since it freezes at about −11 ° C. or less, in use in a cold region, the urea water freezes inside the urea water supply line or the urea water tank, and the situation where the urea water cannot be supplied does not occur. It is necessary to take some measures against freezing.

  Therefore, as a conventional countermeasure against freezing of the urea water supply line and the urea water tank, the urea water supply line and the urea water tank are heated by using an electric heater and frozen in use in a cold region. It is contemplated that the tank can be thawed.

  In addition, as prior art document information related to this type of urea water freezing countermeasure, the following patent document 1 and patent document 2 by the same applicant as the present invention already exist.

JP 2005-248823 A JP 2005-248824 A

  However, if the urea water supply line or the urea water tank is heated using the electric heater in this way, the load on the engine increases due to the power consumption of the electric heater, which may cause a significant deterioration in fuel consumption. There was this.

  The present invention has been made in view of the above circumstances, and provides an exhaust emission control device capable of thawing urea water that has frozen in a urea water supply line or a urea water tank, without using power, using the engine as a heat source. Objective.

The present invention provides a selective reduction catalyst that is provided in the middle of an exhaust pipe and can selectively react NOx with ammonia even in the presence of oxygen, and urea water as a reducing agent in the exhaust pipe upstream of the selective reduction catalyst. a urea water injector to be added, the urine Motomi urea water tank for supplying the urea water through the urea water supply line to the injector, and an exhaust gas purifying device provided with, via the urea water tank and the urea water along the feed line provided with a cooling water line, the in after passing through the cooling water line by extracting cooling water from the water-cooled oil cooler of the pressure of the cooling water is relatively high engine side in the cooling water line In the cooling water line, the cooling water is returned to the engine-side water pump having the lowest pressure .

  Thus, in this way, even if urea water freezes in the urea water supply line or inside the urea water tank due to use in a cold region, it passes through the water-cooled oil cooler on the engine side to the cooling water line. By feeding the cooling water whose temperature has been raised, it becomes possible to thaw the urea water frozen in the urea water tank or the urea water supply line by applying heat from the cooling water line.

  At this time, the pressure analysis by the present inventor has confirmed that the pressure of the cooling water in the water-cooled oil cooler is relatively high among the water-cooling systems of the engine. It has already been verified that the cooling water can be circulated well by returning to the side.

  Since the water-cooled oil cooler has a sufficient amount of cooling water for cooling the lubricating oil, even if the cooling water is withdrawn from here, there is an effect on the water cooling system downstream of the water-cooled oil cooler. There is also a favorable situation that only a minor amount is required.

  In the present invention, the cooling water line branches from the upstream side of the urea water tank, passes through the urea water injector, and merges with the downstream portion after finishing along the urea water supply line in the cooling water line. It is also possible to provide a bypass line and provide a flow path switching means so that the flow of the cooling water can be switched to the bypass line.

  In this way, when the urea water tank or the urea water supply line is not frozen, the flow of the cooling water is switched to the bypass line by the flow path switching means, and the cooling water is allowed to flow through the urea water injector. The urea water injector can be cooled.

  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, urea water frozen in the urea water supply line or the urea water tank can be thawed without consuming electric power using the engine as a heat source.

  (II) According to the invention described in claim 2 of the present invention, when the urea water tank and the urea water supply line are not frozen, the flow of the cooling water is switched to the bypass line by the flow path switching means, and the urea water injector The urea water injector can be cooled by flowing the cooling water through the.

It is a whole system diagram showing typically an example of an embodiment which carries out the present invention.

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

  FIG. 1 is an overall system diagram schematically showing an example of an embodiment of the present invention. A selective reduction catalyst 4 is provided in the middle of an exhaust pipe 3 through which exhaust gas 2 from an engine 1 flows. The selective catalytic reduction catalyst 4 is formed as a flow-through type honeycomb structure or the like, and has such a property that NOx can be selectively reacted with ammonia even in the presence of oxygen.

  A urea water supply line 8 connects a urea water injector 5 provided upstream of the selective catalytic reduction catalyst 4 and a urea water tank 7 provided at a required location and storing the urea water 6. The urea water 6 in the urea water tank 7 is sucked up by driving the urea water pump 9 installed in the middle of the urea water supply line 8.

  In the example shown here, a particulate filter 10 is provided upstream of the urea water injector 5, and the particulate filter 10 and the selective catalytic reduction catalyst 4 are respectively connected by casings 11 and 12. In addition to being held in parallel, the outlet side end of the particulate filter 10 and the inlet side end of the selective catalytic reduction catalyst 4 are connected by an S-shaped connecting flow path 13, and the particulates The exhaust gas 2 discharged from the outlet end of the filter 10 is folded in the reverse direction and introduced into the inlet end of the adjacent selective catalytic reduction catalyst 4.

  In addition, an oxidation catalyst 14 that oxidizes the unburned fuel in the exhaust gas 2 is provided in the front stage in the casing 11 in which the particulate filter 10 is held, and the selective reduction catalyst 4 is provided. An ammonia reduction catalyst 15 that oxidizes surplus ammonia is provided in the rear stage in the casing 12 that is held.

  And regarding the exhaust gas purification device configured in this way, in this embodiment, a cooling water line 16 is provided so as to pass through the urea water tank 7 and along the urea water supply line 8. The cooling water 18 is extracted from a water-cooled oil cooler 17 on the engine 1 side with respect to the cooling water line 16, passed through the cooling water line 16, and then returned to the water pump 19 on the engine 1 side.

  More specifically, the urea water supply line 8 includes a suction pipe 8a for pumping the urea water 6 from the urea water tank 7 to the urea water pump 9, and an internal flow path (not shown) of the urea water pump 9. ) And a feed pipe 8b for feeding urea water 6 from the urea water pump 9 to the urea water injector 5, and the cooling water line 16 includes the suction pipe 8a, the urea water pump, and the like. 9 is formed along all the internal flow paths and the feed pipe 8b.

  Further, in the present embodiment, the cooling water line 16 branches from the branch point A upstream from the urea water tank 7, passes through the urea water injector 5, and finishes along the urea water supply line 8 in the cooling water line 16. A bypass line 20 is provided so as to join the junction B in the downstream portion after the downstream, and downstream of the branch point A in the cooling water line 16 so that the flow of the cooling water 18 can be switched to the bypass line 20. A cooling water cutoff valve 21 (flow path switching means) is provided on the side, and an electromagnetic valve 22 (flow path switching means) is provided downstream of the branch point A in the bypass line 20.

  Thus, in this way, even if the urea water 6 freezes in the urea water supply line 8 or the urea water tank 7 due to use in a cold region, the cooling water shut-off valve 21 is opened and the electromagnetic valve The urea water that has been frozen in the urea water tank 7 and the urea water supply line 8 by sending the cooling water 18 heated through the water-cooled oil cooler 17 on the engine 1 side to the cooling water line 16 by closing 6 can be defrosted by applying heat from the cooling water line 16.

  At this time, among the water cooling systems of the engine 1, the pressure analysis by the inventor has ascertained that the pressure of the cooling water 18 in the water cooling type oil cooler 17 is relatively high, and water having the lowest pressure in the water cooling system. It has already been verified that the cooling water 18 can be circulated favorably by returning to the pump 19 (suction side).

  The water-cooled oil cooler 17 has a sufficient amount of cooling water 18 for cooling the lubricating oil. Even if the cooling water 18 is extracted from the water-cooled oil cooler 17, the water-cooling system downstream of the water-cooled oil cooler 17 is used. There is also a preferable circumstance that the influence on the image is minimal.

  Further, particularly in the present embodiment, the water is branched from the branch point A upstream of the urea water tank 7 of the cooling water line 16, passes through the urea water injector 5, and is along the urea water supply line 8 in the cooling water line 16. A bypass line 20 is provided so as to join the junction B in the downstream portion after the completion, and the cooling water shutoff valve 21 and the electromagnetic valve 22 are connected to the bypass line 20 so that the flow of the cooling water 18 can be switched in the bypass line 20. Therefore, when the urea water tank 7 and the urea water supply line 8 are not frozen, the cooling water shut-off valve 21 is closed and the electromagnetic valve 22 is opened at an appropriate opening according to the operating state of the engine 1 for cooling. By switching the flow of the water 18 to the bypass line 20 and flowing the cooling water 18 through the urea water injector 5, the urea water injector 5 can be cooled.

  If the urea water tank 7 and the urea water supply line 8 are not frozen and the urea water injector 5 is not particularly required to be cooled, both the cooling water shut-off valve 21 and the electromagnetic valve 22 are closed, and the cooling water line 16 and Of course, the circulation of the cooling water 18 to the bypass line 20 may be stopped.

  Therefore, according to the above embodiment, the urea water 6 frozen in the urea water supply line 8 and the urea water tank 7 can be thawed without using the engine 1 as a heat source, and the urea water tank 7. When the urea water supply line 8 is not frozen, the cooling water shut-off valve 21 is closed and the electromagnetic valve 22 is opened at an appropriate opening according to the operating state of the engine 1 to switch the flow of the cooling water 18 to the bypass line 20. The urea water injector 5 can be cooled by flowing the cooling water 18 through the urea water injector 5.

  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 3 Exhaust pipe 4 Selective reduction type catalyst 5 Urea water injector 6 Urea water 7 Urea water tank 8 Urea water supply line 16 Cooling water line 17 Water cooling type oil cooler 18 Cooling water 19 Water pump 20 Bypass line 21 Cooling water shutoff valve (flow path) Switching means)
22 Solenoid valve (flow path switching means)

Claims (2)

A selective reduction catalyst that is installed in the middle of the exhaust pipe and can selectively react NOx with ammonia even in the presence of oxygen, and urea water that adds urea water as a reducing agent into the exhaust pipe upstream of the selective reduction catalyst and the injector, and an exhaust gas purification device provided with a urea water tank for supplying urea water through the urea water supply line to the urine Motomi injector,
A cooling water line is provided through the urea water tank and along the urea water supply line, and cooling water is supplied from a water-cooled oil cooler on the engine side in which the pressure of the cooling water is relatively high. An exhaust emission control device configured to return to an engine-side water pump having the lowest cooling water pressure in the cooling water line after being extracted and passed through the cooling water line .   A bypass line is provided so as to branch from the upstream side of the urea water tank of the cooling water line, pass through the urea water injector, and merge with the downstream portion after finishing along the urea water supply line in the cooling water line. The exhaust emission control device according to claim 1, further comprising a flow path switching means so that the flow of the cooling water can be switched in the line.

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