CN114832624A - Tail gas purification method and system for diesel vehicle emission inspection mechanism - Google Patents

Abstract

The invention discloses a method and system for purifying the exhaust gas of a diesel vehicle emission inspection mechanism, which is applied to the technical field of vehicle exhaust gas treatment, and records vehicle information; drives a negative pressure fan to extract the exhaust gas of the vehicle, collects the flow, and heats it to the optimum working temperature of the catalyst and purification treatment; it is judged whether the exhaust gas after the purification treatment meets the purification standard, and if not, the heating and purification treatment is performed again. The invention discloses and provides a method and system for purifying the exhaust gas of a diesel vehicle emission inspection mechanism, which realizes the purification of the exhaust gas of the motor vehicle following detection and purification. Besides, the regeneration method adopted when the DPF is blocked adopts the negative pressure fan and heating device in the measurement module. , remove the soot with a small air volume and high temperature, that is, realize DPF regeneration by controlling the flow rate and temperature.

Description

A method and system for purifying exhaust gas of a diesel vehicle emission inspection mechanism

technical field

The invention relates to the technical field of vehicle exhaust gas treatment, in particular to a method and system for exhaust gas purification of a diesel vehicle emission inspection mechanism.

Background technique

At present, diesel vehicle emission inspection institutions are not equipped with an effective exhaust gas purification system, and most of them are directly extracted and discharged into the atmosphere through the extraction system.

In order to reduce the impact of vehicle exhaust on the environment during the diesel vehicle emission inspection process, some inspection agencies have adopted various exhaust purification methods to ensure that the environment in the inspection station is free from pollution. For example, a forced extraction system is adopted in some testing stations to remove vehicle exhaust gas in the testing stations, and activated carbon is used in some testing stations to adsorb gaseous pollutants. Because the above methods do not purify the exhaust gas or the purification effect is not ideal, it is impossible to effectively prevent the exhaust gas from polluting the atmospheric environment.

Therefore, how to quickly and centrally collect and efficiently purify the exhaust gas discharged during the vehicle inspection process, so as to be able to control and purify the exhaust gas pollution generated in the vehicle emission inspection agency in real time, is an urgent problem to be solved at present.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a method and system for purifying the exhaust gas of a diesel vehicle emission inspection mechanism, which can rapidly and centrally collect and efficiently purify the exhaust gas discharged during the vehicle inspection process, and can control and purify the exhaust gas generated in the vehicle emission inspection mechanism in real time. of exhaust pollution.

In order to achieve the above object, the present invention provides the following technical solutions:

A method for purifying exhaust gas of a diesel vehicle emission inspection mechanism, the specific steps comprising the following steps:

Enter vehicle information;

Drive the negative pressure fan to extract the exhaust gas of the vehicle, collect the flow, heat it to the best working temperature of the catalyst, and purify it;

It is judged whether the exhaust gas after the purification treatment meets the purification standard, and if not, the heating and purification treatment is performed again.

Optionally, in the above-mentioned method for purifying exhaust gas of a diesel vehicle emission inspection mechanism, the purification treatment includes:

Through the oxidation catalytic converter, the carbon monoxide, hydrocarbons and soluble organics in the exhaust gas are oxidized to generate carbon dioxide and water;

The oxidized exhaust gas enters the particle filter for filtration to remove soot particulate matter;

Entering the selective catalytic reducer, the control unit controls the spray amount of the urea aqueous solution according to the flow rate of the exhaust gas to be purified, the nitrogen oxide content and the conversion efficiency of the selective catalytic reducer, and reduces the nitrogen oxides in the exhaust gas to nitrogen and water; The unreacted ammonia gas in the catalytic reducer is absorbed and processed by the ammonia slip catalyst, and at the same time, it catalyzes the reaction of NH ₃ and NO _x into nitrogen gas.

Optionally, in the above-mentioned method for purifying exhaust gas of a diesel vehicle emission inspection mechanism, the heating treatment includes: collecting the inlet temperature of the heating device and displaying the temperature state, adjusting the heating power to control the heating, and monitoring the temperature according to the temperature sensor in front of the SCR. Determine the heating temperature of the heating device so that the carrier temperature and exhaust gas temperature in the subsequent purification device reach the optimal working temperature of the catalyst. If not, continue to control the heating, and use this cycle control until the purification system stops running.

Optionally, in the above-mentioned method for purifying exhaust gas of a diesel vehicle emission inspection mechanism, the method further includes: a regeneration step of the particle trap, and the specific steps are as follows:

Obtain the change of the pressure difference before and after the purification of the particle filter;

When the pressure drop across the particle trap is greater than the upper threshold, the purification work is stopped and regeneration begins;

In the rising stage of the regeneration temperature of the particle filter, obtain whether the peak temperature of the wall of the particle filter reaches the minimum temperature of the regenerated particle filter or whether it reaches the damage temperature of the particle filter carrier;

If it does not reach the minimum regeneration temperature of 600°C or higher than 700°C, continue to adjust the heating power and the diluted exhaust gas flow until the regeneration requirements are met;

During the temperature maintenance stage of the regeneration of the particle filter, the differential pressure sensor at both ends of the particle filter continuously monitors whether the pressure drop is less than the regeneration threshold, and controls the cycle until the regeneration stops.

Optionally, in the above-mentioned method for purifying exhaust gas of a diesel vehicle emission inspection mechanism, the specific steps of controlling the spray amount of the aqueous urea solution are as follows:

The controller sends the motor on command, the pump status command, the diagnostic instrument command on confirmation, the _NOx sensor dew point enable on confirmation, and the urea nozzle manual control on command;

The urea pump enters the pre-injection state. According to the concentration and flow of nitrogen oxides, the injection amount of urea is given, and finally the pump information is fed back and output.

Optionally, in the above-mentioned method for purifying exhaust gas of a diesel vehicle emission inspection mechanism, the calculation process of the given urea injection amount according to the concentration of nitrogen oxides and the flow rate is as follows:

Among them, the volume flow rate of V _S exhaust gas under standard conditions, m ³ /min; NO _x nitrogen and oxygen concentration, ppm; M _urea urea injection amount; δ is the physical conversion efficiency; , 60g/mol is the molar mass of urea; 0.325 is the concentration of urea aqueous solution; 1.087 is the density of urea aqueous solution.

An exhaust gas purification system for a diesel vehicle emission inspection institution, comprising:

The exhaust gas collection and flow measurement module drives the negative pressure fan to obtain the exhaust gas emission, and provides the flow value in the standard state for the subsequent exhaust gas purification module;

The exhaust gas heating module adopts electric heating to heat the exhaust gas of diesel vehicles to meet the optimal catalytic temperature value of the catalyst in the exhaust gas purification module;

The exhaust gas purification module treats CO, HC, SOF, NO _x and soot harmful substances in the exhaust gas through DOC+DPF+SCR+ASC;

The control module respectively controls the actions of the exhaust gas collection and flow measurement module, the exhaust gas heating module and the exhaust gas purification module.

Optionally, the above-mentioned exhaust gas purification system of a diesel vehicle emission inspection mechanism further includes a DPF regeneration module, which performs DPF regeneration by adjusting the heating power and the diluted exhaust gas flow.

As can be seen from the above technical solutions, compared with the prior art, the present invention discloses and provides a method and system for purifying the exhaust gas of a diesel vehicle emission inspection mechanism, which realizes the detection and purification of vehicle exhaust emissions. The regeneration method adopted adopts the negative pressure fan and heating device in the measurement module to remove soot with a small air volume and high temperature, that is, DPF regeneration is realized by controlling the flow rate and temperature.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to the provided drawings without creative work.

Fig. 1 is the method flow chart of the present invention;

Fig. 2 is the purification system self-check flow chart of the present invention;

Fig. 3 is the temperature maintenance flow chart of the heating device of the present invention;

Fig. 4 is the DPF regeneration flow chart of the present invention;

Fig. 5 is the pressure building flow chart of the urea pump of the present invention

Fig. 6 is the injection flow chart of the urea pump of the present invention;

FIG. 7 is a schematic structural diagram of the purification device of the present invention.

In the figure, 1-negative pressure fan; 2-flow meter; 3-pipe heater; 4-exhaust gas delivery pipe; 5-catalytic converter (DOC); 6-particulate trap (DPF); 7-selectivity Catalytic reducer (SCR); 8- ammonia slip catalyst (ASC); 9- front nitrogen and oxygen sensor; 10- rear nitrogen and oxygen sensor; 11- temperature sensor; 12- differential pressure sensor; 13- urea tank; 14- urea pump; 15 - urea nozzle.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The embodiment of the present invention discloses a method for purifying exhaust gas of a diesel vehicle emission inspection mechanism, as shown in FIGS. 1 and 7 , and the specific steps include the following:

The object of the exhaust gas purification system of the diesel vehicle emission inspection agency is the diesel vehicle emission detection item in the detection station, so the beginning of the exhaust emission detection is the beginning of purification. Before the exhaust gas detection and purification starts, after the information of the vehicle to be tested is entered, the vehicle enters the chassis dynamometer, and the operator places the sampling probe of the exhaust gas analyzer into the exhaust pipe. After the preliminary preparations are completed, the exhaust gas detection can be carried out. Exhaust purification begins. The driver controls the speed of the vehicle, the chassis dynamometer is loaded, and the measurement begins; at the same time, the purification system is also in working state, and the exhaust gas collection pipe is placed on the same axis as the exhaust pipe of the vehicle under test, and the air intake of the exhaust gas collection pipe is separated by Measure the exhaust pipe of the vehicle with a length of 15-20 cm, start the variable frequency motor to drive the negative pressure fan, and pump the exhaust gas of the vehicle under test through the V-cone flowmeter to the heating device for electric heating treatment, so that the exhaust gas reaches the catalyst in the subsequent purification device. The best working temperature (about 280 ℃). After that, the exhaust gas enters the vehicle purification device for purification treatment. First, the harmful gases in the exhaust gas (mainly carbon monoxide (CO), hydrocarbons (HC) and soluble organic matter (SOF), etc. ) is oxidized to generate carbon dioxide (CO ₂ ) and water (H ₂ O). The oxidized exhaust gas enters a particulate filter ( _DPF ) for filtration to remove particulate matter such as soot, and then enters a selective catalytic reducer (SCR). ) content and SCR conversion efficiency to control the injection amount of urea aqueous solution, and reduce nitrogen oxides (NO _x ) in the exhaust gas to nitrogen (N ₂ ) and water (H ₂ O). The unreacted ammonia gas (NH ₃ ) in the selective catalytic reducer (SCR) is absorbed and processed by the ammonia slip catalyst (ASC), and at the same time, NH ₃ and NO _x are catalyzed to react to nitrogen gas (N ₂ ). A sensor for collecting _NOx and visible pollutant content is installed at the outlet of the ammonia slip catalyst (ASC) to monitor whether the purified exhaust gas meets the purification standard. This achieves the purpose of purifying the environment around the diesel vehicle emission inspection agency and ensuring the health of the staff and surrounding residents.

In order to further optimize the above technical scheme, as shown in Figure 2, in order to ensure the smooth progress of the purification process of the exhaust gas purification system of the emission inspection agency, the system itself is firstly checked before purification. After the purification system is powered on and initialized, the command is first sent through the CAN bus, that is, it is first detected whether the communication function of the purification system CAN bus is normal. After the CAN bus communication function is normal, the fan can be turned on, and the function of the fan and the exhaust gas flow sensor after dilution are judged in turn. Then, you can send an instruction to detect the temperature sensor. The temperature sensor is mainly used to monitor the exhaust gas temperature after dilution. After judging that the temperature sensor is working properly, the heating device is turned on to determine whether the heating function of the heating device is normal. The temperature adjusts the heating power to control the heating. When the temperature sensor before the SCR detects that the exhaust gas temperature is higher than 280 °C, the temperature of the DOC, DPF, SCR, and ASC carrier catalysts is satisfied, and the high temperature hydrolysis of urea to generate ammonia and NOx is effective. The temperature of the reaction is then judged whether the nitrogen oxygen sensor function and the pressure sensor function are normal. After each sensor is faultless, the urea dosing pump motor can be turned on to judge whether the urea dosing pump pressure building function and the back suction and pumping function are normal. During the self-checking process of the whole system, if any function of the purification system is abnormal, all checks will be stopped and a fault alarm signal will be issued. Finally, save the system self-test results.

In order to further optimize the above technical solution, as shown in FIG. 3 , the heating treatment includes: the main function of maintaining the temperature of the heating device is to continuously and stably maintain the exhaust gas of the diesel vehicle at the optimum catalytic temperature of the purification device. After the purification system is powered on and initialized, the heating function program of the heating device starts, and then waits for the temperature preset, collects the inlet temperature of the heating device and displays the temperature status, adjusts the heating power to control the heating, and judges whether the temperature before SCR meets the target temperature. Then continue to control the heating, and this cycle control until the purification system stops running.

In order to further optimize the above technical solution, as shown in Figure 4, it also includes: a regeneration step of the particle trap, the specific steps are as follows:

When the purification system of the diesel vehicle emission inspection agency is in working state, the pressure difference sensor of the purification device has been monitoring the change of the pressure difference before and after the DPF. When the pressure drop at both ends of the DPF is greater than the upper threshold (15kPa), the lower computer sends an alarm signal and stops the process. Purification work, perform regeneration procedure. After the DPF regeneration program starts, the heating device and the fan are turned on, and the regeneration temperature is steadily increased by adjusting the heating power and the exhaust gas flow rate after dilution. During the rising stage of DPF regeneration temperature, the temperature sensor continuously monitors whether the peak temperature of the DPF wall reaches the regeneration temperature range (600℃～700℃). Because the soot particles attached to the carrier during the regeneration stage of DPF will release a lot of heat, causing the DPF carrier to burn. If it is damaged due to overheating, if it does not reach the minimum regeneration temperature or exceeds the carrier damage temperature, continue to adjust the heating power and the diluted exhaust gas flow until the regeneration requirements are met. Then enter the DPF regeneration temperature maintenance stage, the differential pressure sensor at both ends of the DPF continuously monitors whether the pressure drop is less than the regeneration threshold (3kPa), and this cycle controls until the regeneration program stops running. In order to further optimize the above technical solution, as shown in Figure 5, after the diesel vehicle emission inspection mechanism exhaust gas purification system is powered on and initialized, the urea dosing pump self-test is completed, the system is fault-free and the exhaust gas temperature after dilution is greater than 180 ℃. Subsequently, the pump controller sends a frame of CAN message to the urea dosing pump, the urea dosing pump enters the pressure building state, the urea dosing nozzle is closed, and the urea solution flows in from the urea dosing tank assembly inlet pipe. Then, the pressure of the urea dosing pump is detected. When the pressure of the urea dosing pump is greater than or equal to 5.5 bar and the pressure building time is less than or equal to 35s, it indicates that the pressure of the urea dosing pump is successfully established, and the urea dosing pump stops rotating, otherwise the cycle control is performed until the pressure building of the urea dosing pump system is successful.

In order to further optimize the above-mentioned technical scheme, as shown in Figure 6, the specific steps of controlling the spray amount of the aqueous urea solution are as follows:

After the pressure build-up of the urea dosing pump is successful, the pump receives the injection command from the controller, and the urea dosing pump enters the injection state. The pump control sends the motor on command, the pump status command, the diagnostic instrument command on confirmation, the NO _x sensor dew point enable on confirmation, the urea nozzle manual control on command, etc. Then, the urea dosing pump enters the pre-injection state, and then enters the injection state, given The urea injection amount, and finally the pump information is fed back and output, which mainly includes information such as pump pressure, nozzle opening, actual injection amount, and actual state of the pump.

It should be understood that the relational formula of urea injection quantity is determined: 1 mol of urea is hydrolyzed at high temperature to generate 2 mol of NH ₃ , and the reaction ratio of NH ₃ to NO _x is 1:1.

In order to further optimize the above technical scheme, the calculation process of the given urea injection amount according to the nitrogen oxide concentration and flow rate is as follows:

Among them, the volume flow rate of V _S exhaust gas under standard conditions, m ³ /min; NO _x nitrogen and oxygen concentration, ppm; M _urea urea injection amount; δ is the physical conversion efficiency; , 60g/mol is the molar mass of urea; 0.325 is the concentration of urea aqueous solution; 1.087 is the density of urea aqueous solution.

Another embodiment discloses a diesel vehicle emission inspection mechanism exhaust gas purification system, comprising:

The exhaust gas collection and flow measurement module drives the negative pressure fan to obtain the exhaust gas emission, and provides the flow value in the standard state for the subsequent exhaust gas purification module;

The exhaust gas heating module adopts electric heating to heat the exhaust gas of diesel vehicles to meet the optimal catalytic temperature value of the catalyst in the exhaust gas purification module;

The exhaust gas purification module treats CO, HC, SOF, NO _x and soot harmful substances in the exhaust gas through DOC+DPF+SCR+ASC;

The control module respectively controls the actions of the exhaust gas collection and flow measurement module, the exhaust gas heating module and the exhaust gas purification module.

In order to further optimize the above technical solution, a DPF regeneration module is also included, which performs DPF regeneration by adjusting the heating power and the diluted exhaust gas flow.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. As for the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. a diesel vehicle emission inspection mechanism tail gas purification method, is characterized in that, concrete steps comprise as follows: Enter vehicle information; Drive the negative pressure fan to extract the exhaust gas of the vehicle, collect the flow, heat it to the best working temperature of the catalyst, and purify it; It is judged whether the exhaust gas after the purification treatment meets the purification standard, and if not, the heating and purification treatment is performed again. 2. The exhaust gas purification method of a diesel vehicle emission inspection mechanism according to claim 1, wherein the purification treatment comprises: First, through the oxidation catalytic converter, the carbon monoxide, hydrocarbons and soluble organics in the exhaust gas are oxidized to generate carbon dioxide and water; The oxidized exhaust gas enters the particle filter for filtration to remove soot particulate matter; Entering the selective catalytic reducer, the control unit controls the spray amount of the urea aqueous solution according to the flow rate of the exhaust gas to be purified, the nitrogen oxide content and the conversion efficiency of the selective catalytic reducer, and reduces the nitrogen oxides in the exhaust gas to nitrogen and water; The unreacted ammonia gas in the catalytic reducer is absorbed and processed by the ammonia slip catalyst, and at the same time, it catalyzes the reaction of NH ₃ and NO _x into nitrogen gas. 3. The method for purifying exhaust gas of a diesel vehicle emission inspection mechanism according to claim 1, wherein the heating treatment comprises: collecting the inlet temperature of the heating device and displaying the temperature state, adjusting the heating power to control the heating, and according to the SCR pre- The monitoring temperature of the temperature sensor determines the heating temperature of the heating device, so that the carrier temperature and the exhaust gas temperature in the subsequent purification device reach the optimal working temperature of the catalyst. . 4. The method for purifying exhaust gas of a diesel vehicle emission inspection mechanism according to claim 2, further comprising: a regeneration step of the particle trap, and the specific steps are as follows: Obtain the change of the pressure difference before and after the purification of the particle filter; When the pressure drop across the particle trap is greater than the upper threshold, the purification work is stopped and regeneration begins; In the rising stage of the regeneration temperature of the particle filter, obtain whether the peak temperature of the wall of the particle filter reaches the minimum temperature of the regenerated particle filter or whether it reaches the damage temperature of the particle filter carrier; If it does not reach the minimum regeneration temperature of 600°C or higher than 700°C, continue to adjust the heating power and the diluted exhaust gas flow until the regeneration requirements are met; During the temperature maintenance stage of the regeneration of the particle filter, the differential pressure sensor at both ends of the particle filter continuously monitors whether the pressure drop is less than the regeneration threshold, and controls the cycle until the regeneration stops. 5. a kind of diesel vehicle emission inspection mechanism tail gas purification method according to claim 2, is characterized in that, the concrete steps of controlling the spray amount of urea aqueous solution are as follows: The controller sends the motor on command, the pump status command, the diagnostic instrument command on confirmation, the _NOx sensor dew point enable on confirmation, and the urea nozzle manual control on command; The urea pump enters the pre-injection state. According to the concentration and flow of nitrogen oxides, the injection amount of urea is given, and finally the pump information is fed back and output. 6. a kind of diesel vehicle emission inspection mechanism tail gas purification method according to claim 2, is characterized in that, according to nitrogen oxide concentration and flow, given urea injection quantity calculation process is as follows:

Among them, the volume flow rate of V _S exhaust gas under standard conditions, m ³ /min; NO _x nitrogen and oxygen concentration, ppm; M _urea urea injection amount; δ is the physical conversion efficiency; , 60g/mol is the molar mass of urea; 0.325 is the concentration of urea aqueous solution; 1.087 is the density of urea aqueous solution. 7. A diesel vehicle emission inspection mechanism tail gas purification system, characterized in that, comprising: The exhaust gas collection and flow measurement module drives the negative pressure fan to obtain the exhaust gas emission, and provides the flow value in the standard state for the subsequent exhaust gas purification module; The exhaust gas heating module adopts electric heating to heat the exhaust gas of diesel vehicles to meet the optimal catalytic temperature value of the catalyst in the exhaust gas purification module; The exhaust gas purification module treats CO, HC, SOF, NO _x and soot harmful substances in the exhaust gas through DOC+DPF+SCR+ASC; The control module respectively controls the actions of the exhaust gas collection and flow measurement module, the exhaust gas heating module and the exhaust gas purification module. 8 . The exhaust gas purification system of a diesel vehicle emission inspection mechanism according to claim 7 , further comprising a DPF regeneration module, which performs DPF regeneration by adjusting the heating power and the diluted exhaust gas flow. 9 .

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