Dynamic adjusting method and system for urea concentration and injection amount in SCR system

Abstract

The invention provides a method and a system for dynamically adjusting urea concentration and injection quantity in an SCR (Selective Catalytic Reduction) system. The method comprises the steps that (1) the load of an engine, the temperature of an inlet and an outlet of an SCR system and the NOx concentration of the inlet and the outlet of the SCR system are monitored in real time so as to judge the NOx reduction requirement; 2) dynamically adjusting the urea concentration according to the real-time monitored data; and (3) the urea injection amount is dynamically adjusted in combination with adjustment of the urea concentration, so that it is ensured that the urea injection amount is matched with the NOx concentration, the optimal NOx reduction efficiency is achieved, and ammonia escape is prevented. The method is a technology for dynamically adjusting the urea concentration and the injection amount in SCR equipment, meets NOx emission requirements under different working conditions in ship operation, optimizes the working efficiency of an SCR system, flexibly adjusts the urea solution concentration and the injection amount, achieves the effect of efficiently reducing nitrogen oxides, and meanwhile can reduce ammonia escape to the maximum extent.

Description

Technical Field

[0001] The present invention relates to SCR to deal with NO x The invention discloses a method for dynamically adjusting emission requirements, and specifically relates to a method and system for dynamically adjusting urea concentration and injection amount in an SCR system. Background Art

[0002] SCR (Selective Catalytic Reduction) technology is a highly efficient way to reduce nitrogen oxides (NO x ) emission method, which has been widely used in ship main engines and other high-temperature combustion devices. Its working principle is to selectively reduce nitrogen oxides in the exhaust gas with a reducing agent (usually a 40% concentration of urea solution) under high temperature conditions through the action of a catalyst to generate nitrogen and water vapor, thereby significantly reducing air pollution. This technology can effectively meet NO x The need for emission control.

[0003] However, in the actual ship operation environment, the performance of the SCR system faces many challenges. First, the load and exhaust temperature of the ship's main engine are constantly changing, which leads to the catalyst activity and NO in the SCR reactor. x The amount of urea generated also fluctuates. Traditional SCR systems mainly control the supply of reducing agent by adjusting the injection amount of urea, but in actual operation, this adjustment method is too simple and rough. Due to changes in load and temperature, it is difficult to achieve ammonia and NO by only adjusting the injection amount. x Precise control of reaction ratio. The limitations of this control method are particularly obvious under extremely high or low load conditions, as well as when the load or temperature changes drastically.

[0004] Under low temperature and low load conditions, the catalyst activity of the SCR system is significantly reduced. Even if the injection amount of urea solution is increased, ammonia slip may occur due to insufficient reaction, that is, unreacted ammonia is discharged into the atmosphere. This is not only a waste of urea resources, but may also cause secondary pollution to the environment, causing greater harm to the environment. In addition, a large adjustment of the injection amount may also cause urea to be oversaturated on the catalyst surface, forming deposits or blockages, further reducing the life and efficiency of the catalyst.

[0005] On the other hand, after the ship's main engine is installed on board, its operating environment (such as temperature and humidity) is significantly different from laboratory conditions, which leads to the activity of the SCR catalyst and NO x The amount of NO generated will also change significantly. When the ship is running at low load, the exhaust temperature decreases and the catalyst activity weakens. If urea is still injected according to the injection amount during the bench test, it is very easy to cause urea overspray and ammonia slip. When the ship enters high load operation or the exhaust temperature rises, NO xThe generation of NO increases significantly. If the urea injection amount cannot be adjusted in time, it will not be able to meet the higher NO x Restoring demand leads to excessive emissions.

[0006] In summary, the existing SCR system that controls the supply of reducing agent by adjusting the urea injection amount only has many problems in actual operation. These problems include the x Inaccurate emission control, waste of resources, environmental pollution, and reduced catalyst life and efficiency. In view of these problems, the industry urgently needs a more advanced SCR system control technology to achieve precise control of the reductant, so as to adapt to the NOx emission control needs under different working conditions, improve resource utilization efficiency, reduce environmental pollution, and extend the service life of the catalyst. Summary of the invention

[0007] The purpose of the present invention is to fundamentally solve the problem that the urea injection amount and injection concentration in the existing SCR system do not match the system's actual demand for reducing agent. By introducing advanced urea concentration adjustment technology and combining it with the adjustment of the injection amount, the present invention achieves dual precise control of the reducing agent.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for dynamically adjusting urea concentration and injection amount in an SCR system, the method comprising:

[0010] 1) Real-time monitoring of engine load, SCR system inlet and outlet temperature, and SCR system inlet and outlet NO x concentration to determine NO x The need for restoration to determine NO x The need for restoration;

[0011] 2) Dynamically adjust urea concentration based on real-time monitoring data;

[0012] 3) Combined with the adjustment of urea concentration, dynamically adjust the urea injection amount to ensure that the urea injection amount is consistent with NO x Concentrations are matched to achieve optimal NO x Restore efficiency and prevent ammonia slip;

[0013] The urea injection amount and NO x The matching relationship of concentration is as follows:

[0014] Urea injection amount = (k × NO x concentration) / urea concentration

[0015] Among them, urea injection volume is the amount of urea injected per unit time (L / h), NO xThe concentration is the NO in the exhaust gas at the outlet of the SCR system. x concentration (ppm), urea concentration is the concentration of urea solution (mol / L), k is a coefficient indicating the relationship between urea and NO x The reaction ratio is usually close to 1.

[0016] Furthermore, the method for adjusting the urea concentration includes: automatically diluting concentrated urea, switching urea storage tanks with different concentrations, or dynamically mixing high-concentration urea and low-concentration urea.

[0017] Furthermore, the method for adjusting the urea concentration is that when high-concentration urea and low-concentration urea are dynamically mixed, the high-concentration urea and the low-concentration urea are transported to a mixing device for mixing according to a dynamically adjusted ratio, thereby adjusting the urea concentration injected into the SCR reactor. The mixing device is not limited, and a commonly used mixing tank with an agitator can achieve mixing.

[0018] Furthermore, the method for dynamically adjusting the urea concentration and injection amount in the SCR system, step 2) and step 3) dynamically adjusting the urea concentration and the urea injection amount adopts a PID adjustment method, and automatically adjusts the urea injection amount and concentration according to the real-time monitoring data of the sensor to ensure that NO x The reduction rate is stable at the highest level.

[0019] Furthermore, under high engine load and / or high SCR system outlet temperature, NO x The emission is large, the catalyst has high working efficiency, and a higher concentration of urea solution can be used to ensure sufficient reduction reaction; under low load or low temperature conditions, due to NO x The amount generated is small and the catalyst activity is low, so a lower concentration of urea solution can be used to avoid ammonia slip.

[0020] A system for implementing the above-mentioned method for dynamically adjusting urea concentration and injection amount in an SCR system comprises:

[0021] 1) Real-time monitoring system, used to monitor the engine load, SCR system inlet and outlet temperature, and SCR system inlet and outlet NO x concentration to determine NO x The need for restoration;

[0022] 2) Urea concentration adjustment device, used to dynamically adjust the urea concentration according to real-time monitoring data;

[0023] 3) Injection amount adjustment device, used to dynamically adjust the urea injection amount in combination with the adjustment of urea concentration;

[0024] d) A control unit, which is used to receive real-time monitoring data from the real-time monitoring system, automatically generate dynamic adjustment data of urea concentration and urea injection amount, and send them to the urea concentration adjustment device and the injection amount adjustment device respectively.

[0025] Furthermore, the real-time monitoring system includes a temperature sensor, a NO x Concentration sensor and pressure sensor.

[0026] Furthermore, the control unit uses a PID adjustment method to automatically generate dynamic adjustment data of urea concentration and urea injection amount according to real-time monitoring data of the sensor.

[0027] Furthermore, the urea regulating device includes a high-concentration urea cabinet, a low-concentration urea cabinet and a neutralization cabinet. The high-concentration urea cabinet and the low-concentration urea cabinet respectively control the high-concentration urea flow rate and the low-concentration urea flow rate entering the neutralization cabinet through regulating valve A and regulating valve B respectively; the neutralization cabinet is used to mix the high-concentration urea and the low-concentration urea entering the neutralization cabinet to adjust the urea concentration. The flow control of regulating valve A and regulating valve B is controlled by the urea concentration data issued by the control unit.

[0028] Furthermore, the injection amount regulating device includes a pump station, a metering unit and a spray gun connected in sequence, the pump station is used to pump the urea regulated by the urea regulating device into the metering unit, the metering unit performs metering according to the dynamic adjustment data of the urea injection amount issued by the control unit, and delivers the metered injection amount of urea to the spray gun, and the spray gun sprays the urea into the SCR reactor.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. Fine control of ammonia and NO x The proportion

[0031] More precise control of ammonia and NO by adjusting urea concentration x The concentration of urea and NO x The molar ratio is more stable, which can avoid inefficiency or ammonia slip caused by excessive or insufficient injection.

[0032] 2. Reduce ammonia escape

[0033] Under low temperature or low load conditions, low concentration of urea can be used to slow down the entry of excessive urea. Through precise concentration adjustment, even if the injection amount is increased, it can ensure that the catalyst and urea react fully and reduce ammonia slip.

[0034] 3. Wider scope of work

[0035] Urea concentration adjustment can cope with a wider range of exhaust temperature and load changes. At high loads, high concentrations of urea can be used to quickly reduce NO x , and use low concentration urea at low load to keep the system efficiency stable.

[0036] 4. Save costs and improve efficiency

[0037] By adjusting the urea concentration, urea can be used more economically while maintaining the reduction efficiency. When the load is low and the temperature is low, using a low concentration of urea can save costs; when the load is high, using a high concentration can quickly deal with NO x high emission requirements and improve the efficiency of the entire system.

[0038] 5. Extended catalyst life

[0039] Using lower urea concentrations can reduce deposit formation, especially when the catalyst is not working properly, helping to extend the life of the catalyst and reduce maintenance frequency.

[0040] 6. Adapt to the complex working conditions of different ships

[0041] Urea concentration adjustment can more flexibly respond to emission control needs under different navigation environments, avoiding the lag and reduced reaction efficiency caused by injection quantity adjustment alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The urea concentration regulating device and the injection amount regulating device in the SCR system in Example 1 DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in combination with the drawings in the present invention and the embodiments. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0044] Example 1

[0045] A method for dynamically adjusting urea concentration and injection amount in an SCR system, the method comprising:

[0046] 1) Real-time monitoring of engine load, SCR system inlet and outlet temperature, and SCR system inlet and outlet NO x concentration to determine NO x The need for restoration to determine NO x The need for restoration;

[0047] 2) Dynamically adjust urea concentration based on real-time monitoring data;

[0048] 3) Combined with the adjustment of urea concentration, dynamically adjust the urea injection amount to ensure that the urea injection amount is consistent with NO x Concentrations are matched to achieve optimal NO x Restore efficiency and prevent ammonia slip;

[0049] The urea injection amount and NO x The matching relationship of concentration is as follows:

[0050] Urea injection amount = (k × NO x concentration) / urea concentration

[0051] Among them, urea injection volume is the amount of urea injected per unit time (L / h), NO x The concentration is the NO in the exhaust gas at the outlet of the SCR system. x concentration (ppm), urea concentration is the concentration of urea solution (mol / L), k is a coefficient indicating the relationship between urea and NO x The reaction ratio is usually close to 1.

[0052] The method for adjusting the urea concentration is to dynamically mix high-concentration urea and low-concentration urea. The high-concentration urea and the low-concentration urea are transported to a mixing device for mixing according to a dynamically adjusted ratio, thereby adjusting the urea concentration injected into the SCR reactor. The mixing device is not limited, and a commonly used mixing tank with an agitator can achieve mixing.

[0053] The method for dynamically adjusting the urea concentration and injection amount in the SCR system, the method for dynamically adjusting the urea concentration and the urea injection amount in step 2) and step 3) adopts a PID adjustment method, and automatically adjusts the urea injection amount and concentration according to the real-time monitoring data of the sensor to ensure that the NOx reduction rate is stable at the highest level.

[0054] Under high engine load and / or high SCR system outlet temperature, NO x The emission is large, the catalyst has high working efficiency, and a higher concentration of urea solution can be used to ensure sufficient reduction reaction; under low load or low temperature conditions, due to NO x The amount generated is small and the catalyst activity is low, so a lower concentration of urea solution can be used to avoid ammonia slip.

[0055] A system for implementing the above-mentioned method for dynamically adjusting urea concentration and injection amount in an SCR system comprises:

[0056] 1) Real-time monitoring system, used to monitor the engine load, SCR system inlet and outlet temperature, and SCR system inlet and outlet NO xconcentration to determine NO x The need for restoration;

[0057] 2) Urea concentration adjustment device 10, used to dynamically adjust the urea concentration according to real-time monitoring data;

[0058] 3) an injection amount adjustment device 20, used to dynamically adjust the urea injection amount in combination with the adjustment of urea concentration;

[0059] d) A control unit, which is used to receive real-time monitoring data from the real-time monitoring system, automatically generate dynamic adjustment data of urea concentration and urea injection amount, and transmit the data to the urea concentration adjustment device 10 and the injection amount adjustment device 20 respectively.

[0060] The real-time monitoring system includes temperature sensors, NO x Concentration sensor and pressure sensor. Temperature sensor monitors the inlet and outlet temperature of SCR system in real time and feeds back to the control unit. x The concentration sensor monitors the NO inlet and outlet of the SCR system in real time. x The concentration is fed back to the control unit, and the pressure sensor monitors the engine load in real time and feeds back to the control unit.

[0061] The control unit uses the PID adjustment method to automatically generate dynamic adjustment data of urea concentration and urea injection amount according to the real-time monitoring data of the sensor.

[0062] like Figure 1 As shown, the urea regulating device 10 includes a high-concentration urea tank 101, a low-concentration urea tank 102 and a neutralization tank 103. The high-concentration urea tank and the low-concentration urea tank respectively control the high-concentration urea flow rate and the low-concentration urea flow rate entering the neutralization tank through a regulating valve A 104 and a regulating valve B 105 respectively; the neutralization tank is used to mix the high-concentration urea and the low-concentration urea entering the neutralization tank to adjust the urea concentration. The flow control of the regulating valve A and the regulating valve B is controlled by the urea concentration data issued by the control unit. The neutralization tank 105 is provided with a stirrer, which can be used to mix the high-concentration urea from the high-concentration urea tank 101 and the low-concentration urea from the low-concentration urea tank 102.

[0063] like Figure 1 As shown, the injection amount regulating device 20 includes a pump station 201, a metering unit 202 and a spray gun 203 which are connected in sequence. The pump station is used to pump the urea mixed in the neutralization cabinet into the metering unit. The metering unit performs metering according to the dynamic adjustment data of the urea injection amount issued by the control unit, and delivers the metered injection amount of urea to the spray gun, which sprays the urea into the SCR reactor.

[0064] First, according to the NO before and after the SCR system xConcentration sensors measure NO before and after the system x Concentration, according to NO x concentration, the system adjusts the concentration of urea to control the use of reducing agent, which can be x High concentration urea is used when the concentration is high, and low concentration urea is used when the concentration is low. While controlling the urea concentration, the urea injection amount can be adjusted to accurately match the reducing agent and NO x The ratio of the injected urea to NO is x The reaction produces nitrogen and water vapor, and the system then x The sensor's measurements automatically adjust the urea concentration and injection amount to ensure optimal reduction efficiency and prevent ammonia slip.

[0065] The choice of urea concentration requires different concentrations of urea under different working conditions, depending on NO x Emissions and current exhaust temperature.

[0066] The injection volume is combined with the concentration. Low-concentration urea requires a larger injection volume to achieve the same reduction effect as high-concentration urea. Therefore, the optimal combination of the two is needed.

[0067] Therefore, the PID adjustment method can be used to automatically adjust the injection volume and concentration according to the real-time data of the sensor to ensure NO x The reduction rate is stable at the highest level.

Claims

1. A method for dynamically adjusting urea concentration and injection amount in an SCR system, characterized in that: The method includes: 1) Real-time monitoring of engine load, SCR system inlet and outlet temperature, and SCR system inlet and outlet NO x concentration to determine NO x The need for restoration to determine NO x The need for restoration; 2) Dynamically adjust urea concentration based on real-time monitoring data; 3) Combined with the adjustment of urea concentration, dynamically adjust the urea injection amount to ensure that the urea injection amount is consistent with NO x Concentrations are matched to achieve optimal NO x Restore efficiency and prevent ammonia slip; The urea injection amount and NO x The matching relationship of concentration is as follows: Urea injection amount = (k × NO x concentration) / urea concentration Among them, urea injection volume is the amount of urea injected per unit time (L / h), NO x The concentration is the NO in the exhaust gas at the outlet of the SCR system. x concentration (ppm), urea concentration is the concentration of urea solution (mol / L), k is a coefficient indicating the relationship between urea and NO x The reaction ratio is usually close to 1.

2. The dynamic adjustment method according to claim 1, characterized in that: The method for adjusting the urea concentration includes: automatically diluting concentrated urea, switching urea storage tanks with different concentrations, or dynamically mixing high-concentration urea and low-concentration urea.

3. The dynamic adjustment method according to claim 2, characterized in that: The method for adjusting the urea concentration is to dynamically mix high-concentration urea and low-concentration urea. The high-concentration urea and the low-concentration urea are transported to a mixing device for mixing according to a dynamically adjusted ratio, thereby adjusting the urea concentration injected into the SCR reactor.

4. The dynamic adjustment method according to claim 2, characterized in that: The method for dynamically adjusting the urea concentration and the urea injection amount in step 2) and step 3) adopts a PID adjustment method to automatically adjust the urea injection amount and concentration according to the real-time monitoring data of the sensor to ensure that the NOx reduction rate is stable at the highest level.

5. A system for implementing the method for dynamically adjusting urea concentration and injection amount in an SCR system as claimed in any one of claims 1 to 4, characterized in that: include: 1) Real-time monitoring system, used to monitor the engine load, SCR system inlet and outlet temperature, and SCR system inlet and outlet NO x concentration to determine NO x The need for restoration; 2) Urea concentration adjustment device, used to dynamically adjust the urea concentration according to real-time monitoring data; 3) Injection amount adjustment device, used to dynamically adjust the urea injection amount in combination with the adjustment of urea concentration; d) A control unit, which is used to receive real-time monitoring data from the real-time monitoring system, automatically generate dynamic adjustment data of urea concentration and urea injection amount, and send them to the urea concentration adjustment device and the injection amount adjustment device respectively.

6. The system according to claim 5, characterized in that The urea regulating device comprises a high-concentration urea tank, a low-concentration urea tank and a neutralization tank. The high-concentration urea tank and the low-concentration urea tank respectively control the high-concentration urea flow rate and the low-concentration urea flow rate entering the neutralization tank through a regulating valve A and a regulating valve B respectively; the neutralization tank is used to mix the high-concentration urea and the low-concentration urea entering the neutralization tank to adjust the urea concentration.

7. The system according to claim 5, characterized in that The injection amount regulating device includes a pump station, a metering unit and a spray gun connected in sequence. The pump station is used to pump urea regulated by the urea regulating device into the metering unit. The metering unit performs metering according to the dynamic adjustment data of the urea injection amount issued by the control unit, and delivers the metered injection amount of urea to the spray gun, and the spray gun sprays the urea into the SCR reactor.

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