DE102009008743B4 - Heating circuit for heating an ammonia storage device when the internal combustion engine is at a standstill - Google Patents

Abstract

Heating circuit for heating a device (2) that stores ammonia in bound form and through which coolant of a coolant circuit of an internal combustion engine (3) having a coolant delivery pump (4) flows, wherein the heating circuit has a delivery pump (9) for delivering coolant to the device (2) and by means the heat emitted by the internal combustion engine (3), the device (2) can be heated, characterized in that the heating circuit has a non-return valve (6) which can be actuated in such a way that coolant heated by means of the feed pump (9) when the internal combustion engine (3) is at a standstill can be conveyed to the device (2) and through the heat of the internal combustion engine (3) to the means releasing the coolant.

Description

The present invention relates to a heating circuit for heating a device that stores ammonia in bound form and through which coolant of a coolant circuit of an internal combustion engine having a coolant delivery pump flows, wherein the heating circuit has a delivery pump for delivering coolant to the device and the device can be heated by means of the heat emitted by the internal combustion engine , according to the preamble of claim 1.

Vehicles with internal combustion engines usually have a coolant circuit whose heat is used, for example, to heat the vehicle interior via a heat exchanger. Coolant flows through the heat exchanger and is circulated by means of a coolant feed pump of the internal combustion engine. Due to the pressure difference in the coolant circuit of the internal combustion engine, the heat exchanger is also flowed through when this is not functionally required, ie the heat exchanger is not required to emit heat to the vehicle interior.

Internal combustion engines that operate on the principle of the lean-burn engine are operated with excess air and nitrogen oxides are found in the oxygen-containing exhaust gases from these internal combustion engines, which can be removed by means of selective catalytic reduction, for which purpose ammonia is used as a selective and efficient reducing agent . The reduction takes place in a so-called SCR catalytic converter, to which ammonia is fed for reduction.

In known systems, ammonia is obtained from aqueous urea by hydrolysis by evaporating the urea and passing it over a catalyst to form ammonia.

Based on DE 197 28 343 C1 a method and a device for the selective catalytic reduction of nitrogen oxides have become known, according to which ammonia is not obtained from aqueous urea, but is bound to a metal salt in the form of, for example, strontium chloride and is kept ready in a container that is carried in the vehicle and is heated to release the ammonia.

According to this publication, a heating device which uses the waste heat from the engine coolant of the internal combustion engine has become known as a heating device. The container for releasing ammonia from the metal salt is heated via the heating device. It has been shown that such ammonia storage tanks operated with metal salt react very sluggishly to the supply of heat, depending on the fill level or residual load with ammonia.

Based on DE 27 12 438 A1 a heating device for a motor vehicle has become known which has an electric water pump in the cooling circuit of the engine and the electric water pump is switched on and off via a temperature sensor which measures the temperature of the coolant.

Based on DE 10 97 761 A1 a coolant circuit of an internal combustion engine has become known, which is generally controlled by a thermostat.

Based on DE 103 48 799 B4 a device for exhaust gas aftertreatment has become known, in which aqueous urea is fed to a heating device together with air. There, the mixture is vaporized and the resulting vapor is introduced into the exhaust gas flow, which enters the SCR catalytic converter.

Based on WO 2008/ 065 390 A1, a combined system consisting of a device for exhaust gas recirculation and selective catalytic reduction has become known, which has an EGR heat exchanger for heat exchange with a cooling fluid before exhaust gas recirculation to the engine to reduce the formation of nitrogen oxides, and an SCR catalyst for Separation of the nitrogen oxides from the exhaust gas before it is released into the atmosphere.

Based on EP 1 806 487 A1 a device for cleaning exhaust gas for engines has become known, which has a cooling water line for guiding the cooling water to a reducing agent tank with a shut-off valve, which is opened to defrost the reducing agent and which is also opened when the reducing agent is not frozen, in order to ensure that the cooling water circulates in the cooling water line.

The present invention is based on the object of creating a heating circuit for heating a device storing ammonia in bound form, which makes it possible for ammonia to be released more quickly even in the case of an ammonia storage device which is already reacting sluggishly. A method serving to improve the release behavior of ammonia in such an ammonia storage device is also to be created.

In order to solve this problem with regard to the heating circuit, the invention has the features specified in claim 1 . Advantageous Expenses Arrangements thereof are described in the further claims. In addition, the invention has the features specified in claim 7 with regard to the method, an advantageous embodiment of which is specified in the further claim.

The invention provides a heating circuit for heating a device that stores ammonia in bound form and through which coolant of a cooling circuit of an internal combustion engine having a coolant delivery pump flows, wherein the heating circuit has a delivery pump for delivering coolant to the device and the device can be heated by means of the heat given off by the internal combustion engine. wherein the heating circuit has a non-return valve which can be actuated in such a way that coolant heated by means of the delivery pump when the internal combustion engine is at a standstill can be delivered to the device and through heat from the internal combustion engine to the coolant-emitting means.

The heating circuit according to the invention makes it possible to use the thermal energy stored in the internal combustion engine after it has been switched off to heat up the ammonia storage device. For this purpose, the check valve can be actuated in such a way that the supply pump provided in the heating circuit can be used to convey coolant to the device in order to heat it up and coolant can be conveyed through heat from the internal combustion engine to the coolant-emitting agent. These means can be, for example, cooling water ducts of the internal combustion engine, through which the coolant flows and which heat up in the process.

These cooling water ducts can be provided, for example, in the crankcase, in the cylinder head or in other areas of the internal combustion engine, very generally those areas that are heated by the intended operation of the internal combustion engine and through which the coolant can flow, so that the coolant heats up and its heat then to the ammonia storage device.

It is therefore also possible that the means that give off heat to the coolant are, for example, heat exchange devices that are heated by the intended operation of the internal combustion engine, for example the heat exchanger provided in the cooling circuit of the internal combustion engine, a heat exchanger for heating the vehicle interior or also a heat exchanger provided for cooling the engine oil of the internal combustion engine.

According to a development of the invention, it is provided that the non-return valve in the heating circuit is provided in such a way that it can be actuated by means of the system pressure generated by the coolant feed pump to allow coolant to pass in the direction of a heat exchanger.

In other words, this means that the coolant feed pump, which first delivers the coolant in the small, inner cooling circuit and then also in the large, outer cooling circuit, generates such a system pressure in the heating circuit that the non-return valve is opened and the coolant flows in the direction of a heat exchanger lets through, which may be the vehicle radiator.

During the intended operation of the internal combustion engine, the check valve is opened in such a way that the coolant feed pump arranged on the internal combustion engine can pump the coolant to the vehicle radiator in the intended manner. From there it goes back towards the internal combustion engine and enters it, the cycle begins again.

During this open state of the check valve, due to the small pressure difference between the exit of the coolant at the internal combustion engine and the entry of the coolant into the internal combustion engine, there is no significant mass flow of coolant through the heating circuit in the direction of the ammonia storage device, an undesired, uncontrolled mass flow of coolant through the ammonia storage device is thus avoided. Therefore, no undesired ammonia vapor pressure can arise in the ammonia storage device.

If it is desired to increase the ammonia vapor pressure, it is only necessary to operate the feed pump to feed coolant towards the device until the desired ammonia vapor pressure has been reached. A respectively desired ammonia vapor pressure can thus be achieved by appropriate control or regulation of the mode of operation of the feed pump. However, an uncontrolled increase in the ammonia vapor pressure is avoided in this way, since the coolant flow conveyed by the coolant feed pump does not necessarily flow through the heating circuit.

After the internal combustion engine has been switched off, heated coolant can continue to flow through the heating circuit in the direction of the ammonia storage device and through the still via a corresponding control of the feed pump Heated internal combustion engine are pumped through to use the existing residual heat to maintain the ammonia vapor pressure. If the internal combustion engine is switched off for a predetermined period of time, the ammonia vapor pressure can be maintained in this way and sufficient gaseous ammonia is also available immediately after the internal combustion engine is restarted to immediately initiate a selective catalytic reaction in the SCR catalytic converter for exhaust gas aftertreatment.

As already mentioned above, a further development of the invention also provides for the heating circuit to be designed in such a way that when the check valve is open and the feed pump is not actuated, a flow of coolant in the direction of the device is largely avoided.

The check valve may be a normally closed type check valve. In other words, this means that the coolant feed pump of the internal combustion engine must actively press open the check valve, for example against a spring device. If the internal combustion engine is switched off, the non-return valve closes automatically due to the spring device and a feed pump which has been put into operation or is already in operation and which conveys the heated coolant towards the device can be operated with little power in order to pump heated coolant through the heating circuit towards the ammonia storage device.

With such a design of the check valve, heating of the ammonia storage device can be achieved with a low-power delivery pump and an undefined state of the heating circuit is avoided, which could consist in the coolant being delivered by the delivery pump in the direction of the ammonia storage device, this leaves again and without passing through the heat of the internal combustion engine to the coolant-releasing agent, re-enters the ammonia storage device.

The closed non-return valve ensures that the coolant conveyed by the feed pump passes through the medium giving off heat from the internal combustion engine.

According to a development of the invention, it is also provided that the check valve can be closed by means of the system pressure generated by the feed pump in the heating circuit. In other words, this means that the feed pump ensures that the check valve is closed due to the system pressure it generates, so that the short-circuit flow described above between the coolant inlet and the coolant outlet at the ammonia storage device is avoided in turn, without the coolant flowing through the Heat of the internal combustion engine emitting agent is passed through. With such an embodiment, the coolant feed pump of the internal combustion engine can be provided with low power since it is not required to force open the normally closed check valve. With such a configuration, electrical drive energy for operating the coolant feed pump can be saved.

In order to improve the ammonia release behavior of the ammonia storage device, the invention provides a method for heating a device that stores ammonia in bound form and through which coolant of a coolant circuit of an internal combustion engine flows, according to which, when the internal combustion engine is at a standstill, coolant is pumped by means of a feed pump through means of the internal combustion engine that release heat to the coolant and the heated coolant is used to heat the device.

According to this method, the residual heat stored in the internal combustion engine can be used to heat the ammonia storage device and in this way to ensure sufficient ammonia vapor pressure, which is available for catalytic reduction immediately after the internal combustion engine is started or restarted.

In order to counteract an undesired formation of ammonia vapor pressure in the ammonia storage device, the method according to the invention provides, according to a development, that a check valve in a heating circuit for heating up the device is actuated in such a way that the coolant is conveyed through the means when the internal combustion engine is at a standstill and when the internal combustion engine is running without the conveyance of coolant by means of a conveying pump provided in the heating circuit, a flow of coolant in the direction of the device is largely avoided.

In this way it is achieved that the coolant feed pump provided in the coolant circuit of the internal combustion engine does not force hot coolant to flow through the ammonia storage device. In this way, an undesired formation of ammonia vapor pressure in the ammonia storage device can be avoided.

The invention is explained in more detail below with reference to the drawing. This shows in the single figure a schematic representation of a heating circuit according to an embodiment of the present invention.

An ammonia storage device 2 containing a metal salt in the form of, for example, strontium chloride, which contains ammonia in bound form, can be heated via the heating circuit 1 . Heating the ammonia storage device 2 releases ammonia, which can be fed via a fluid line (not shown) to an exhaust system in which an SCR catalytic converter is located for the catalytic, selective reduction of nitrogen oxides in the exhaust gas of the vehicle.

Coolant circulates in the heating circuit 1 from a coolant circuit of an internal combustion engine 3, which has a coolant feed pump 4, which is intended to pump coolant heated by the operation of the internal combustion engine through a heat exchanger 5, which may be the vehicle radiator.

The heating circuit 1 has a check valve 6 which is fluidically integrated between a coolant outlet A of the internal combustion engine 3 and a coolant outlet D of the ammonia storage device 2 or a fluid line 7 connected to the coolant outlet D.

During the operation of the internal combustion engine 3, the check valve 6 is opened by the coolant flow generated by the coolant feed pump 4.

The heated coolant exits the internal combustion engine 3 at point A and enters the fluid line 7 through the open check valve 6 and at point B and is conveyed by the coolant feed pump 4 in the direction of the inlet E of the heat exchanger 5, there during of the passage is cooled and exits the heat exchanger 5 again at point F. From there it flows in the direction of the internal combustion engine 3 and enters it again, the cycle begins again.

Because the check valve 6 is open during normal operation of the internal combustion engine 3, there is no significant pressure difference between point A and point B, so that an unintended flow of coolant fluid in the direction of the ammonia storage device 2 does not occur.

An electrically operated feed pump 9 is provided in the fluid line 8 between the internal combustion engine 3 and the ammonia storage device 2, via which the heated coolant can be pumped from the coolant circuit of the internal combustion engine 3 to the ammonia storage device 2, where it enters the ammonia storage device 2 at point C Metal salt is heated, for example, via a heat exchanger arranged in the ammonia storage device 2, so that ammonia is released and leaves the ammonia storage device 2 again at point D and is fed back to the coolant circuit of the internal combustion engine via the fluid line 7.

Due to the small pressure difference between point A and point B, there is not a significant fluid flow of refrigerant through the ammonia storage device 2 when the electric feed pump 9 is not operated. An undesired formation of ammonia vapor pressure in the ammonia storage device 2 is avoided in this way.

The dynamic pressure generated by the coolant feed pump 4 is greater than the negative pressure generated by the feed pump 9, so that when both pumps are in operation, the check valve 6 is in the open state.

If the internal combustion engine 3 is switched off, the coolant feed pump 4 also stops operating. If the feed pump 9 is operated, the negative pressure generated in the fluid line 8 ensures that the check valve 6 is closed. The coolant delivered by the feed pump 9 enters the ammonia storage device 2, is pumped via the fluid line 7 in the direction of the heat exchanger 5, a short-circuit flow from point B to point A is avoided via the closed check valve 6, the coolant flows through the heat exchange device 5, which is physically connected, for example, to the cooler for the engine oil of the internal combustion engine 3 , can already absorb heat there and is conveyed in the direction of the coolant inlet of the internal combustion engine 3 .

The coolant flows through the coolant channels of the internal combustion engine 3, is heated there and exits the internal combustion engine 3 at point A. A flow of coolant from point A to point B is avoided via the closed check valve 6, the coolant thus heated by the residual heat of the internal combustion engine 3 is returned by the feed pump 9 in the direction of the ammonia storage device 2.

In this way, the residual heat of the internal combustion engine is used to maintain the ammonia vapor pressure in the ammonia storage device by means of the heating circuit according to the invention and the method according to the invention th, so that after starting or restarting the internal combustion engine immediately ammonia for nitrogen oxide reduction is available.

The check valve present in the heating circuit ensures that forced flow through the ammonia storage device due to the coolant feed pump of the internal combustion engine is largely avoided, so that no undesirable ammonia vapor pressure can develop in the ammonia storage device.

With regard to features of the invention that are not detailed above, reference is expressly made to the claims and the drawing.

Reference List

1

heating circuit

2

ammonia storage device

3

internal combustion engine

4

coolant feed pump

5

heat exchanger

6

check valve

7

fluid line

8th

fluid line

9

pump

Claims (8)

Heating circuit for heating a device (2) that stores ammonia in bound form and through which coolant of a coolant circuit of an internal combustion engine (3) having a coolant delivery pump (4) flows, wherein the heating circuit has a delivery pump (9) for delivering coolant to the device (2) and by means the heat emitted by the internal combustion engine (3), the device (2) can be heated, characterized in that the heating circuit has a non-return valve (6) which can be actuated in such a way that the coolant heated by means of the feed pump (9) when the internal combustion engine (3) is at a standstill can be conveyed to the device (2) and through the heat of the internal combustion engine (3) to the means releasing the coolant. heating circuit after claim 1 , characterized in that the check valve (6) in the heating circuit (1) is provided in such a way that it can be actuated by means of the coolant feed pump (4) generated system pressure for the passage of coolant in the direction of a heat exchanger (5). heating circuit after claim 1 or 2 , characterized in that the heating circuit (1) is designed in such a way that when the check valve (6) is open and the feed pump (9) is not actuated, a flow of coolant in the direction of the device (2) is largely avoided. Heating circuit according to any one of the preceding claims, characterized in that the non-return valve (6) is of the normally closed type. Heating circuit according to one of the preceding claims, characterized in that the non-return valve (6) can be closed by means of the system pressure generated by the feed pump (9) in the heating circuit (1). Heating circuit according to one of the preceding claims, characterized in that the check valve (6) is arranged in the flow direction of the coolant between a coolant outlet (A) of the internal combustion engine and a coolant outlet (D) of the device (2). Method for heating a device (2) which stores ammonia in bound form and through which coolant of a coolant circuit of an internal combustion engine (3) flows, characterized in that when the internal combustion engine (3) is at a standstill, means of the Internal combustion engine (3) is promoted through and the heated coolant for heating the device (2) is used. procedure after claim 7 , characterized in that a check valve (6) in a heating circuit (1) for heating the device (2) is actuated in such a way that the coolant is conveyed through the means when the internal combustion engine (3) is at a standstill and without when the internal combustion engine (3) is running the conveying of coolant by means of a conveying pump (9) provided in the heating circuit (1) largely avoids a flow of coolant in the direction of the device (2).

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