Method for non-road diesel engine to deal with SCR sulfur poisoning

Abstract

The invention discloses a method for a non-road diesel engine to deal with SCR (Selective Catalytic Reduction) sulfur poisoning, relates to the field of SCR conversion, and solves the problem that after high-sulfur diesel is used, the SCR conversion efficiency is sharply reduced when the exhaust temperature is lower than 300 DEG C. The method comprises the steps that real-time SCR conversion efficiency and real-time exhaust temperature are obtained, and when the real-time SCR conversion efficiency is smaller than a preset first SCR conversion efficiency set value, a low-temperature regeneration measure and a high-temperature regeneration measure are triggered in sequence to judge whether an SCR unit is subjected to sulfur poisoning or not; and when it is judged that the SCR unit is subjected to sulfur poisoning and the high-temperature regeneration measure is ended, a thermal management mode is triggered. According to the method, a user is reminded of diesel oil replacement, so that the SCR unit keeps high SCR conversion efficiency, and the emission of the whole vehicle meets the requirements of laws and regulations.

Description

Technical Field

[0001] The present invention relates to the field of SCR conversion, and more specifically, it relates to a method for a non-road diesel engine to cope with SCR sulfur poisoning. Background Art

[0002] The SCR (Selective Catalytic Reduction System) in an engine is an important environmental protection technology, mainly used to reduce the emissions of nitrogen oxides (NOx) in the engine exhaust gas to meet more stringent emission regulation standards.

[0003] The selective catalytic reduction technology (SCR) is a treatment process for NOx in diesel vehicle exhaust emissions. That is, under the action of a catalyst, a reducing agent ammonia or urea is injected to reduce NOx in the exhaust gas to N2 and H2O. The catalysts are divided into two categories: precious metals and non-precious metals. The basic working principle of the system is as follows: After the exhaust gas comes out of the turbine, it enters the exhaust mixing pipe. A urea metering injection device is installed on the mixing pipe, and aqueous urea solution is injected. Urea undergoes hydrolysis and pyrolysis reactions at high temperatures to generate NH3. On the surface of the SCR system catalyst, NH3 is used to reduce NOx, and N2 is discharged. The excess NH3 is also oxidized to N2 to prevent leakage. Generally, when consuming 100L of fuel, 5L of aqueous urea solution is consumed simultaneously.

[0004] This technology is also widely used in the after-treatment of diesel engine exhaust gas. By optimizing the fuel injection and combustion processes, the generation of particulate matter PM is controlled as much as possible inside the engine, and then the nitrogen oxides formed under oxygen-rich conditions are treated outside the engine. Vehicle urea (vehicle urea decomposes to generate ammonia at a certain temperature) is used to selectively catalytically reduce nitrogen oxides (NOx) in a timely manner, so as to achieve the purpose of both energy conservation and emission reduction.

[0005] However, when users use high-sulfur diesel, copper-based molecules in the SCR unit will generate copper sulfate when the exhaust gas temperature is lower than 300 °C, resulting in a sharp decrease in the SCR conversion efficiency and ultimately causing the vehicle exhaust NOx emissions to fail to meet the regulatory requirements. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for a non-road diesel engine to cope with SCR sulfur poisoning in view of the deficiencies of the prior art, and solve the problem that the SCR conversion efficiency drops sharply when the exhaust gas temperature is lower than 300 °C after using high-sulfur diesel.

[0007] A method for a non-road diesel engine to cope with SCR sulfur poisoning according to the present invention, the method includes obtaining the real-time SCR conversion efficiency and the real-time exhaust temperature. When the real-time SCR conversion efficiency is less than a preset first SCR conversion efficiency setting value, low-temperature regeneration measures and high-temperature regeneration measures are triggered in sequence to adjust the real-time exhaust temperature to determine whether the SCR unit is sulfur poisoned; when it is determined that the SCR unit is sulfur poisoned and the high-temperature regeneration measure ends, a thermal management mode is triggered.

[0008] For further improvement, the low-temperature regeneration measure is to increase the real-time exhaust temperature to a preset first exhaust temperature setting value.

[0009] Furthermore, the method for determining whether the SCR unit is sulfur poisoned is that when the real-time exhaust temperature is greater than the first exhaust temperature setting value and the real-time SCR conversion efficiency is greater than a preset second SCR conversion efficiency setting value, it is determined that the SCR unit is sulfur poisoned and an abnormal sulfur poisoning alarm is given; otherwise, the SCR unit is not sulfur poisoned.

[0010] Even further, the thermal management mode is to set a thermal management time. During the thermal management time, the throttle is opened to keep the real-time exhaust temperature at a preset third exhaust temperature setting value. When the thermal management time counting ends, the thermal management mode is cancelled.

[0011] Even further, the abnormal sulfur poisoning alarm is cancelled while the thermal management mode is cancelled.

[0012] Even further, a delay time is set. The real-time SCR conversion efficiency after cancelling the thermal management mode is used as the third SCR conversion efficiency. When the third SCR conversion efficiency is less than the first SCR conversion efficiency setting value, the delay time starts to count; the real-time SCR conversion efficiency after the delay time counting is completed is used as the fourth SCR conversion efficiency. When the fourth SCR conversion efficiency is still less than the first SCR conversion efficiency setting value, the thermal management mode is triggered again.

[0013] Even further, the high-temperature regeneration measure is to increase the real-time exhaust temperature to a preset second exhaust temperature setting value to remove sulfur elements in the SCR unit.

[0014] Beneficial effects

[0015] The advantages of the present invention are as follows:

[0016] The present invention obtains the real-time SCR conversion efficiency and the real-time exhaust temperature. When the real-time SCR conversion efficiency is less than a preset first SCR conversion efficiency setting value, low-temperature regeneration measures and high-temperature regeneration measures are triggered to determine whether the SCR unit is sulfur poisoned; when it is determined that the SCR unit is sulfur poisoned and the high-temperature regeneration measures are completed, a thermal management mode is triggered, thereby realizing a reminder for the user to replace the diesel, enabling the SCR unit to maintain a high SCR conversion efficiency, and enabling the emissions of the whole vehicle to meet the regulatory requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flowchart of the method for dealing with SCR sulfur poisoning of the present invention;

[0018] Figure 2 is a schematic diagram of the curve related to the exhaust temperature and SCR efficiency of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following describes the present invention in further detail with reference to embodiments, but does not constitute any limitation to the present invention. Any limited modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0020] Refer to Figure 1 - Figure 2 , a method for a non-road diesel engine of the present invention to deal with SCR sulfur poisoning, the method includes obtaining the real-time SCR conversion efficiency and the real-time exhaust temperature. When the real-time SCR conversion efficiency is less than a preset first SCR conversion efficiency setting value, low-temperature regeneration measures and high-temperature regeneration measures are sequentially triggered to adjust the real-time exhaust temperature to determine whether the SCR unit is sulfur poisoned; when it is determined that the SCR unit is sulfur poisoned and the high-temperature regeneration measures are completed, a thermal management mode is triggered.

[0021] SCR is a selective catalytic reductant, mainly for treating NO in the exhaust gas X . When the user uses high-sulfur diesel, copper-based molecular sieves in the SCR unit will generate copper sulfate.

[0022] As Figure 2 shown, when the exhaust temperature is below 300 °C, the conversion efficiency of SCR drops sharply, and the NOx emissions of the whole vehicle's exhaust gas cannot meet the regulatory requirements.

[0023] The low-temperature regeneration measure is to raise the real-time exhaust temperature to a preset first exhaust temperature setting value. The first exhaust temperature setting value is 350 °C. In the present invention, when the NOx sensor downstream of the post-treatment device recognizes that the SCR conversion efficiency is lower than the first SCR conversion efficiency setting value, a low-temperature regeneration measure is first triggered, that is, the exhaust temperature is raised to about 350 °C to see if the SCR conversion efficiency increases. That is, to see if the SCR conversion efficiency at this exhaust temperature is greater than the second SCR conversion efficiency calibration value or has an upward trend of change.

[0024] The method for judging whether the SCR unit is sulfur poisoned is that when the real-time exhaust temperature is greater than the first exhaust temperature setting value and the real-time SCR conversion efficiency is greater than the preset second SCR conversion efficiency setting value, the SCR unit is judged to be sulfur poisoned, and a sulfur poisoning abnormal alarm is issued; otherwise, the SCR unit is not sulfur poisoned. If it is sulfur poisoning, the SCR conversion efficiency below 300°C will be relatively low or even negative, but the conversion efficiency above 350°C is very high. Therefore, the role of low-temperature regeneration measures is to increase the exhaust temperature, check the SCR conversion efficiency after the low-temperature regeneration measures, and analyze whether it is sulfur poisoning. If the SCR conversion efficiency is greater than the second SCR conversion efficiency setting value, it is judged that the sulfur poisoning is caused by the user's use of high-sulfur fuel. Inform the user to replace normal diesel and perform parking regeneration.

[0025] Then a high-temperature regeneration measure is triggered, which is to increase the real-time exhaust temperature to the preset second exhaust temperature setting value. The second exhaust temperature setting value is 600℃, which is mainly used to remove sulfur elements in the SCR unit, because at this second exhaust temperature setting value, sulfate will decompose, that is, SCR unit desulfurization.

[0026] The thermal management mode is to set the thermal management time, and open the throttle valve during the thermal management time to keep the real-time exhaust temperature at the preset third exhaust temperature setting value. The third exhaust temperature setting value is 400℃. In this mode, the throttle valve is opened to make the exhaust temperature reach 400℃. At this temperature, even after the SCR unit is sulfur poisoned, it can still maintain a high NO X After replacing the diesel, the triggering of the thermal management mode is re-judged through the existing diagnostic instrument or parking regeneration method.

[0027] After the thermal management mode is released, the sulfur poisoning abnormal alarm is released.

[0028] Set the delay time, and use the real-time SCR conversion efficiency after releasing the thermal management mode as the third SCR conversion efficiency. When the third SCR conversion efficiency is less than the set value of the first SCR conversion efficiency, the delay time starts timing; use the real-time SCR conversion efficiency after the delay time is completed as the fourth SCR conversion efficiency. When the fourth SCR conversion efficiency is still less than the set value of the first SCR conversion efficiency, the thermal management mode is triggered again.

[0029] Among them, the thermal management mode will be triggered only when sulfur poisoning is determined during the low-temperature regeneration process. If it is not sulfur poisoning, the thermal management mode will not be entered. The main purpose of the thermal management mode is to keep the engine at a temperature above 400°C, because after the SCR unit is sulfur poisoned, it can still maintain a high SCR conversion efficiency at this temperature, so that emissions meet regulatory requirements.

[0030] The SCR conversion efficiency is obtained through the downstream NOx sensor of the post-processor. By comparing the SCR conversion efficiency with the expected value of the preset SCR conversion efficiency, low-temperature regeneration measures, high-temperature regeneration measures, and thermal management modes are triggered, so as to realize the reminder for the user to replace diesel, keep the SCR unit with a high SCR conversion efficiency, and finally make the emissions of the whole vehicle meet the regulatory requirements.

[0031] The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which will not affect the implementation effect of the present invention and the practicability of the patent.

Claims

1. A method for dealing with SCR sulfur poisoning of a non-road diesel engine, characterized in that: The method includes obtaining real-time SCR conversion efficiency and real-time exhaust temperature. When the real-time SCR conversion efficiency is less than a preset first SCR conversion efficiency setting value, low-temperature regeneration measures and high-temperature regeneration measures are triggered in sequence to adjust the real-time exhaust temperature to determine whether the SCR unit is sulfur poisoned; when it is determined that the SCR unit is sulfur poisoned and the high-temperature regeneration measures are completed, a thermal management mode is triggered.

2. A method for dealing with SCR sulfur poisoning of a non-road diesel engine according to claim 1, characterized in that: The low-temperature regeneration measure is to increase the real-time exhaust temperature to a preset first exhaust temperature setting value.

3. A method for dealing with SCR sulfur poisoning of a non-road diesel engine according to claim 2, characterized in that: The method for judging whether the SCR unit is sulfur poisoned is that when the real-time exhaust temperature is greater than a first exhaust temperature setting value and the real-time SCR conversion efficiency is greater than a preset second SCR conversion efficiency setting value, the SCR unit is judged to be sulfur poisoned and an abnormal sulfur poisoning alarm is issued; otherwise, the SCR unit is not sulfur poisoned.

4. A method for dealing with SCR sulfur poisoning of a non-road diesel engine according to claim 3, characterized in that: The thermal management mode is to set a thermal management time, open the throttle during the thermal management time to keep the real-time exhaust temperature at a preset third exhaust temperature setting value, and release the thermal management mode when the thermal management time is over.

5. A method for dealing with SCR sulfur poisoning of a non-road diesel engine according to claim 4, characterized in that: After the thermal management mode is released, the sulfur poisoning abnormal alarm is released.

6. A method for a non-road diesel engine to cope with SCR sulfur poisoning according to claim 4, characterized in that: A delay time is set, and the real-time SCR conversion efficiency after the thermal management mode is released is used as the third SCR conversion efficiency. When the third SCR conversion efficiency is less than the first SCR conversion efficiency setting value, the delay time starts to count; the real-time SCR conversion efficiency after the delay time is completed is used as the fourth SCR conversion efficiency. When the fourth SCR conversion efficiency is still less than the first SCR conversion efficiency setting value, the thermal management mode is triggered again.

7. A method for a non-road diesel engine to cope with SCR sulfur poisoning according to claim 1, characterized in that: The high temperature regeneration measure is to increase the real-time exhaust temperature to a preset second exhaust temperature setting value to remove sulfur elements in the SCR unit.

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