SE535363C2 - Arrangement and method of a dosing system for supplying a reducing agent in the exhaust gas flow from a combustion device - Google Patents

Abstract

The invention relates to an arrangement and a method for a dosing system for supplying a reducing agent in the exhaust gas from an internal combustion device such as a single-combustion engine. More particularly, the invention relates to how to identify an inadequate agent used as a reducing agent in an exhaust gas aftertreatment system. By sensing the temperature of the exhaust gases and comparing it with normal values which occur when using the correct reducing agent, indication of an inadequate agent can be indicated. The indication allows continued dosing of an incorrect agent to be stopped. If, for example, fuel is dosed instead of the intended reducing agent, the commercial temperature of the exhaust gases will exceed what can normally be expected and the damage that can occur as a result of too high exhaust gas temperatures can be avoided (Fig. 1)

Description

25 30 535 363 2 If fuel is filled into the tank intended for reducing agents and the fuel is metered into the exhaust line, there is a considerable risk that components in the exhaust gas treatment system, e.g. the dosing system, catalysts, pipes or surrounding parts are damaged, at the same time as the requested reduction of emissions is absent and instead results in an actual increase in the emissions mot in the engine.

As known in the art, reference is made to US 20100199644 which describes an arrangement and method for diagnosing an exhaust gas treatment system. More specifically, it is stated how this can be used to indicate whether an overly diluted reducing agent is dosed. A control unit is connected to temperature sensors arranged before and after a catalyst, respectively. With knowledge of the amount of reducing agent injected and the temperature before the catalyst, the control unit calculates an expected temperature after the catalyst, and in case the sensed temperature after the catalyst is not the expected one, an error signal is emitted.

There is thus a need to make it possible to detect whether other than the intended reducing agent has been filled into the tank and dosed into the exhaust line.

Summary of the invention The present invention aims to meet the above-mentioned needs. The sewing is achieved by an arrangement according to claim 1 and a method according to claim 5.

The arrangement according to the invention comprises a temperature sensor located downstream of the catalyst. The temperature sensor is connected to a monitoring unit that compares the measured temperature in the exhaust gas downstream of the catalyst with a predetermined verified temperature range that can normally be expected when the correct reducing agent is supplied to the exhaust gas. If the measured temperature does not fall within the range, this is an indication that an agent other than the intended reducing agent is supplied to the exhaust gas by the dosing system.

According to the invention, the supply of agents from the dosing system to the exhaust gas stop is stopped if the measured temperature falls outside the predetermined range. 10 15 20 25 30 535 363 3 This further increases safety against breakdowns and unwanted emissions as the media supply via the dosing system is automatically stopped when there is an indication of an incorrect agent.

In an advantageous embodiment of the arrangement, the temperature range, which the measured temperature should be within about 50 ”C. This range provides reliable measurement and the necessary space for temperature variations which occur due to variations in, for example, ambient conditions, load level in the engine and the like.

In one embodiment of the arrangement, the control unit is connected to an instrument panel where a signal unit indicates whether an agent other than the correct reducing agent is injected into the exhaust port.

This is a good solution to alert an operator that a problem exists, and that corrective action is needed to correct the error. In one embodiment of the arrangement, the filter line includes a filter arranged in the exhaust line downstream of the catalyst and where the temperature sensor is arranged downstream of the filter. This enables the temperature sensor to be placed where there is suitable space. It also means that other types of temperature sensors can be used that are active in other temperature ranges.

The invention also relates to a method which makes it possible to determine in a simple and reliable manner whether the agent dosed from the dosing system tank is not the intended reducing agent. In accordance with the invention, the method also comprises the step of switching off the dosing of agents in the dosing system. This has the advantage that no manual shut-off is required if an incorrect agent in the dosing system has been identified.

In an advantageous embodiment, the method comprises the further subsequent steps after the dosing has been stopped comparing the temperature of the exhaust gases with expected temperatures when no dosing takes place. If this temperature is within the expected range, it is an indication that the other components of the dosing system are working properly. This embodiment of the method makes it possible to determine whether the error is in which agent has been dosed or whether another error prevails in the arrangement.

The invention also relates to a computer program comprising program code for implementing a method according to any of the described embodiments. The process can advantageously be carried out by a computer program which can continuously monitor prevailing temperatures downstream of the catalyst and / or the filter in order to ensure that reducing agents are metered into the exhaust gas.

Brief description Fig. 1 schematically shows an embodiment of the arrangement, and Fig. 2 shows a flow chart for a method according to the invention.

Detailed Description of the Invention Exemplary Embodiments I fi g. 1 shows a schematic arrangement according to the invention. The arrangement comprises an internal combustion engine 10 and an exhaust line 11 intended to direct combustion gases from the engine 10 to a suitable outlet. The size and design of the engine 10 can be varied in many ways to adapt to the vehicle or application where it is intended to function as a source of demand. The engine can thus alternatively be used for marine use or be part of a permanently installed engine for industrial use.

From the engine 10, the exhaust gases are first led to a turbocharger 12, which is driven by the combustion gases. The turbocharger does not have to be included in the arrangement according to the invention and can therefore also be excluded without affecting the arrangement.

The arrangement also includes a system for post-treatment of the exhaust gases from the engine in order to reduce emissions such as reducing nitrogen oxides. For this purpose, the arrangement includes a dosing system 20 for dosing a reducing agent in the exhaust gas in the exhaust line 11. The dosing system 20 comprises a tank 21 intended to hold reducing agent, which may be a suitable aqueous solution of urea, usually marketed under the name AdBlue. The reducing agent is led by means of a pump 22 which generates a pressurized flow in a supply line 23 and then dosed in the exhaust gas port of a dosing unit 24 arranged so that its murmur is placed in the exhaust line 11. There are also other types of reducing agents whose shape and consistency can vary. The components are then adapted based on the selected reducing agent.

The dosing of reducing agent is controlled by a control unit (not shown) which, based on various parameters such as the engine load and / or external influencing factors, determines the amount of reducing agent to be dosed. To ensure that the amount of reducing agent supplied to the dosing unit must always be sufficient, the pump 22 constantly generates a greater flow than is dosed and the excess is led from the dosing unit 24 back to the tank 21.

Downstream of the dosing unit 24 in the exhaust line 11, a catalyst 13 is arranged and in which the reducing agent reacts with the nitrogen oxides in the exhaust gases and thus purifies the exhaust gas. Such a catalyst is often called an SCR catalyst, the construction of which in itself constitutes a well-known technique. In the exhaust line 11, different types of filters can also be arranged to reduce the amount of particles in the exhaust gases. However, something. Lter is not illustrated in the fi guren.

Likewise, other components may be included in the exhaust line for reducing emissions, for example an ammonia grinding catalyst arranged after the catalyst 13. The exhaust line may suitably also include a muffler for reducing noise. As these components are not necessary for understanding the invention, these components are not described in more detail.

Downstream of the catalyst 13, and where appropriate also downstream of a filter, a temperature sensor 14 is provided for measuring the temperature T. of the exhaust gas.

The temperature sensor 14 measures the temperature T at selected intervals and sends the result to a monitoring unit 15. If additional components are included in the exhaust line, the temperature sensor 14 can be arranged before or after these, the important thing is that the temperature sensor 14 is placed downstream of the catalyst 13, regardless of additional components between the catalyst 13 and the temperature sensor 14. 10 15 20 25 30 535 363 6 The monitoring unit 15 compares the measured temperature T against a predetermined temperature range Tmin - Tma, which is determined by testing which temperatures should normally prevail in the exhaust gas vid during continuous operation of the engine If the temperature T in the exhaust gas meter measured by the temperature sensor 14 falls outside the desired determined temperature range, this is an indication that the agent dosed by the dosing unit 24 is not the intended reducing agent.

As an example, if the tank 21 is accidentally (or intentionally) filled with diesel or other fuel instead of reducing agent, the temperature T in the exhaust gas downstream of the catalyst 13 will increase and exceed the highest temperature Tm within the determined desired temperature range. The difference between Tmin and Tmx in this example is of the order of 50 ° 'which gives room for the normal variations that can occur during normal operation with correctly injected reducing agent.

In other applications, temperature ranges can be significantly narrower, on the order of 10 ° or significantly larger on the order of 100 °. How large the temperature range should be is determined, among other things, by where in the exhaust line the temperature sensor 14 is located and whether there are other components between the temperature sensor 14 and the catalyst 13.

Should it be indicated by the temperature input of the monitoring unit 15 that an incorrect reducing agent has been dosed in the exhaust line 11, the arrangement comprises means which make it possible to indicate this to an operator on a signal means intended for this purpose on an instrument panel. In addition, the monitoring unit 15 comprises means by its connection to the dosing unit 24 to be able to stop continued dosing of means in the exhaust line 11, as well as means to be able to switch off the dosing system.

The shut-off of the dosing system 20 can be done manually by an operator when indicating that the wrong agent has been dosed, but it can also be done automatically by the monitoring unit 15 giving a suitable signal to the dosing unit 24.

The arrangement described above operates on the basis of a method, of which an embodiment is illustrated in the fl diagram in fi g. 2.

The method comprises the steps: a) b) C) d) 535 363 7 The first step in the method is to determine whether the agent is dosed by the dosing system 20 by the monitoring unit 15 communicating with the dosing system control unit. If agents are not dosed from dosing unit 24 then step a is repeated and if agents are dosed proceed to step b; Thereafter, the prevailing temperature T downstream of the catalyst 13 is determined by means of the temperature sensor 14; The temperature measured by the temperature sensor 14 is compared with a predetermined temperature range (Tmin <T <Tmax), which normally applies when the correct reducing agent is metered into the exhaust gas flow; if the measured temperature T falls within the range, the intended reducing agent is dosed, and step a is then repeated to verify again that this applies and if not, the procedure continues to step d; The measured temperature T is outside the range, which means that the wrong agent is dosed; the dosage should therefore be switched off. Once it has been determined that the wrong agent has been dosed, this can be visualized to an operator so that the dosing system 20 can be switched off manually or it can be done automatically. The error can then be corrected.

In this type of arrangement, of course, other errors can also occur and to increase the precision of the troubleshooting, the procedure can be further supplemented. This is done by adding additional steps. These are: e) determine the prevailing temperature T downstream of the catalyst 13 after the dosing has been switched off; f) compare the measured temperature T with another predetermined 8) temperature range with reference values (Tmin <T occurring temperatures when reducing agent is not dosed; if the measured temperature T now falls within the range this indicates that other components in the arrangement work properly was the intended reducing agent that has been dosed; the entire dosing system can now be switched off to prevent incorrect agents being circulated in the dosing system; and take corrective action to ensure that the correct reducing agent is used before the dosing system is restarted. h) if the measured temperature T does not fall within the range, this indicates that there is probably an error other than an incorrect reducing agent that has been dosed, for example an error in a sensor or the like; the dosage can therefore be switched on again to reduce nitrogen oxides in the exhaust gases; repeat the procedure again; The invention has been described above on the basis of exemplary embodiments which can of course be combined in different ways. An aqueous solution of urea has been given as an example of a properly intended reducing agent. A correct agent does not have to be in liquid form but can alternatively be an agent in both solid form and gaseous form.

The invention has mainly been described how it can be used to indicate that an incorrect reducing agent is used and that the tank has thus filled in and contains an incorrect reducing agent. Of course, the invention can also be used to indicate that a correct reducing agent is used, which is the case if the measured temperature in the exhaust gas range is within the predetermined range. Such an indication may consist of an absence of an error indication as described.

Alternatively, the arrangement can be supplemented with a signal transmitter, for example in the form of a control lamp, which indicates that there is no fault.

A simplified form of the invention can be used in case there is only a risk that the tank has filled with fuel or other means which risks causing an excessive temperature of the exhaust gases. In such a case, the lower limit of the predetermined temperature range can be set so low that the temperature in practice always exceeds the lower limit. In this case, the arrangement will in practice only indicate incorrectly injected means in the event that an excessively high temperature is measured in the exhaust gases.

Claims (7)

10 15 20 25 30 535 363 PATENT REQUIREMENTS Arrangement for a dosing system (20) for supplying a reducing agent in the exhaust gas flow from an combustion device, comprising an exhaust line (11) which is intended to conduct combustion gases from a combustion device, a catalyst (13) arranged in the exhaust line (1 1) for purification of the exhaust gas, a dosing system (20) for supplying reducing agent to the exhaust gas upstream of the catalyst (13), and a temperature sensor (14) located downstream of the catalyst (13), the temperature sensor (14) being connected to a monitoring unit (15), characterized in that the monitoring unit (15) compares the measured temperature (T) with a predetermined temperature range which normally prevails when the intended reducing agent is dosed, in which case the measured temperature (T) exceeds the temperature range normally prevailing when the intended reducing agent is dosed is used to indicate that an agent other than the intended reducing agent has been dosed by the dosing system (20 ), and that the arrangement comprises means for automatically stopping the supply of means from the dosing system (20) to the exhaust gas if the measured temperature exceeds the predetermined temperature range. Arrangement according to claim 1, characterized in that the feed-determined temperature range is about 50 ° C. Arrangement according to one of the preceding claims, characterized in that the monitoring unit (15) is connected to an instrument panel with a signal unit which, when indicating that an agent other than the intended reducing agent is dosed in the dosing system, shows that an agent other than the intended reducing agent is injected into the exhaust gas flow. Arrangement according to one of the preceding claims, characterized in that a filter is arranged in the exhaust line (1 1) downstream of the catalyst (13) and in that the temperature sensor (14) is arranged downstream of the filter. 10 15 20 25 535 363 10 A method of an arrangement according to any one of the preceding claims, wherein said method comprises the steps of: a) b) C) d) g) h) determining whether dosing is performed by the dosing system (20), and if not, step a is repeated , if dosing is continued to step b; determining the prevailing temperature (T) downstream of the catalyst (1 3); that iron fi ira the measured temperature (T) with a predetermined temperature range, and if the measured temperature (T) falls within the range, this indicates that the system is functioning properly, whereby step a is repeated, but if the measured temperature (T) exceeds the predetermined temperature range indicates this that the wrong agent is dosed, proceed to step d; to automatically switch off the dosing of agents in the dosing system (20). A process according to claim 5, comprising the further steps e or step d: determining the prevailing temperature (T) downstream of the catalyst (13); comparing the measured temperature (T) with a predetermined temperature range with reference values for desired temperatures when reducing agent is not dosed; not proceeding to step h if the measured temperature (T) falls within the range indicating that the intended reducing agent has not been dosed in step a; proceed to step h if the measured temperature (T) falls within the range, switch on the dosing and repeat step a; as it did not help to stop the dosing, the error must be elsewhere in the arrangement. Computer program comprising program code for implementing a method according to any one of claims 5 - 6.