The control of emissions from motor vehicles is an important part of the defense of the blue skies. Among them, the management of diesel vehicles is the most important. In this process, how to control whether the technology is mature or not determines the effect of governance directly. This has become a common concern in the industry. On June 8th, at the 16th China International Environmental Protection Exhibition on Diesel Engine Emissions Management Technology, the reporter of China Auto Daily was exclusively informed of the latest developments in diesel vehicle pollution prevention technology and also learned the essence of the regulatory platform. Sexual function.
Diesel vehicles are the main source of pollution
At present, the atmospheric pollution situation in China is quite severe, causing widespread concern in the industry. The “2018 China Motor Vehicle Environmental Management Annual Report” revealed that motor vehicle exhaust is the main source of atmospheric pollution, and diesel vehicles account for the highest proportion of motor vehicle exhaust emissions. of.
Diesel trucks are the main contributors of NOx and PM, accounting for 57.3% and 77.8%, respectively. However, in the diesel vehicles, the pollution of the National 3 and 4 vehicles is different, and the NOx and PM emissions of the National 3 diesel trucks are accounted for. They accounted for 63% and 68.9%, respectively. The NOx and PM emissions of the Guotai diesel trucks accounted for 26.8% and 17.6%, respectively. Yu Yunbo, a researcher at the Air Pollution Control Center of the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, told the China Automotive News reporter: 'Diesel trucks' Is the focus of motor vehicle pollution emission control, in the use of diesel vehicle emissions control should be the country three, the country four cars, focusing on the treatment.
In addition, the pollution of motor vehicles in various parts of the country is not the same. There are 2.415 million heavy-duty trucks in Beijing-Tianjin-Hebei and the surrounding areas, accounting for 30.7% of the total number of heavy-duty trucks in the country. This has also caused Beijing-Tianjin-Hebei and surrounding areas to become national One of the most polluted areas.
On the whole, in view of the pollution control of diesel vehicles, the country has now formed a “2+26” (Beijing-Tianjin-Hebei air pollution transmission channel, including Beijing, Tianjin and 26 surrounding cities) pollution control situation, and proposed a three-year action plan. Among the 26 cities, there are 1.319 million heavy trucks, accounting for 16.8% of the national total. 'From the point of view of regional distribution, the diesel vehicles in the Beijing-Tianjin-Hebei and surrounding '2+26' cities need to be controlled with a focus on heavy trucks. Focus on these areas, causing serious air pollution.' Yu Yunbo said.
Post-processing technology has matured
There are many pollutants in motor vehicle exhaust, PM 2.5, NOx are the two main pollutants. However, the characteristics of these two pollutants are different. Therefore, the solution is not the same. What technology should be used to solve different pollution? The issue of emissions from materials Yu Yunbo said: 'The Chinese Academy of Sciences undertook a research project and conducted a special study on the issue of pollution emissions from diesel vehicles. It has formed a post-processing retrofit upgrade technology for diesel engines in various applications. The use of diesel engines to upgrade the post-processing of key materials, and the formation of key equipment production technology.
Yu Yunbo told the reporter that the task group evaluated the effects of different PM and NOx technology routes for reducing emissions, established assessment methods and procedures for different pollutant treatment technologies, and selected the best and feasible treatment technologies. After the technical route was determined, the research group started research and development. Low ignition temperature, low precious metal content and anti-aging DOC and CDPF catalytic materials and efficient and durable SCR catalyst, and the research and development results from the laboratory into scientific research results, and then applied to the actual. 'The research group developed a post-processing Transform and upgrade the industrialized production process of key materials and quantitative coating technology to ensure large-scale production consistency and product reliability. ' Yu Yunbo said.
One of the key technologies for the upgrading of diesel engine aftertreatment is diesel particulate filter (DPF). This technology can be used to oxidize NO to NO2 by DOC (diesel oxidation catalytic), trap the soot particles by NO2 oxidation, and coat it with CDPF catalyst. The layer further reduces the light-off temperature.
In order to achieve this goal, the research team developed a 1% Pt/CeO2-NP catalyst with excellent performance. The laboratory test results showed that the CO light-off temperature was 47°C, the C3H6 light-off temperature was 140°C, and the catalyst was calcined at 800°C for 10 hours. Maintaining thermal stability. In the development of CDPF catalysts, the research group developed a non-precious metal SOOT catalyst with excellent performance and has good thermal stability after being fired at 700°C. In the development of SCR catalysts, the research group improved the coupling of catalyst components. , Achieve the close coupling of various compounds, so that the various components play a stronger synergy, this improvement is very suitable for the use of diesel engine after-treatment transformation and upgrading work.
Yu Yunbo said: 'The task force has also developed mass production technologies for key materials and components, and formed diesel engine post-processing retrofit kits, such as DOC+CDPF equipment assemblies and SCR catalytic converters. These devices can meet different transformation space requirements. The layout of the post-processing device is designed. 'It has been learned that the research results of the research group have passed the practice test. After the 400 heavy-duty diesel vehicles used in Tianjin and the 230 heavy-duty diesel vehicles in Handan have been transformed, the average emission reduction rate has reached 83.1%.
Different vehicles need to be screened
Good technologies must be applied in a reasonable way to realize their value. Therefore, the newly developed technologies must be applied to the specific characteristics of their technologies. China's automotive exhaust gas management is a chronic problem. The group put forward specific proposals for the control of emissions from diesel vehicles. In summary, it is to take the national triple emission control as the starting point, coupled with on-line monitoring technology to ensure that the diesel vehicles meet the standards.
Specifically, at present, China still has a considerable number of national diesel vehicles. In addition, China has had the situation of flooding with three vehicles. Therefore, the task group recommends the selection of vehicles suitable for installing DPFs. Low value, long-term, unrepaired vehicles directly limit the line scrap; for burning oil, soot, water leakage, oil spills, DPV transformation of gas leakage vehicles, and install all-weather emission on-line monitoring equipment.
Yu Yunbo said: 'National 3 diesel trucks have a relatively high proportion of NOx and PM emissions, which are 63% and 68.9%, respectively, which must be transformed.'
After the motor vehicles entered the Fourth National and State Five emission stages, China has paid more attention to the issue of vehicle exhaust emission control. It generally requires vehicles to install SCR after-treatment systems. This system has a good effect on the purification of exhaust gas. However, some Due to system failure or artificial shielding, some vehicles have exceeded the standard emission levels. Yu Yunbo said: 'In the event that the SCR system fails, NOx in the country's five heavy-duty diesel vehicles is more than 10 times the normal vehicle emissions. In 2016, the national vehicle The actual consumption of urea only accounts for about one-third of the theoretical demand. This shows that some vehicles are not filled with urea during their actual use. Therefore, all-weather emission on-line monitoring equipment should be installed for the National IV and State V vehicles. Emissions of the vehicle, through the data to identify whether the SCR system fails, whether there is no urea, etc.
Yu Yunbo also pointed out that natural gas vehicles are not absolutely environmentally friendly products. He told reporters that the actual measured value of NOx emissions from the State V natural gas vehicles is 2.5 times that of the National IV diesel vehicles. This needs to attract everyone’s attention. At present, natural gas prices are cheaper than diesel. In the field of commercial vehicles, it is becoming more and more popular. Although the current base number is small, the future number will be very considerable. Therefore, it is necessary to install on-the-spot emissions on-line monitoring equipment for natural gas vehicles to monitor NOx emissions in real time, based on actual emissions Situation and then develop the next work plan.
The regulatory platform is effective
Good technology and good methods also require good supervision and synergy to achieve optimal performance. At the forum, Fang Xiyu, an engineer at China Automotive Technology and Research Center Co., Ltd., introduced the role of the current vehicle pollution emission monitoring platform. Overall, the regulatory platform Divided into four areas of control access, standard installation, strict acceptance and long-term supervision.
Fang Xiyu said that the current regulatory platform has been put into use in many places. Vehicles in eight provinces and cities have access to the monitoring platform, and 4,539 vehicles have been connected. The cumulative operating time of vehicles on the platform has exceeded 800,000 hours, and the accumulated mileage has exceeded 14 million kilometers. , The effectiveness of supervision is remarkable.
Specifically, Fang Xiyu introduced that the monitoring platform consists of five function menus and 14 sub-function modules. It monitored a total of 17 parameters including key performance parameters such as vehicle speed, geographical location information, and emissions information, and achieved the basics of the vehicle on the same platform. The statistical analysis of information management, dynamic parameter monitoring, fault alarm query and emission reduction effect can not only meet the supervision requirements of environmental protection departments, but also provide data support for the optimization of enterprise product performance.
In addition, the monitoring platform also established an intelligent judgment model for vehicle speed, DPF front and rear end temperature, and pressure difference between DPF front and rear ends, realizing real-time monitoring alarms for all monitored vehicles, and helping relevant departments to implement efficient management. 'In addition to regulatory functions, the platform The post-processing system installed in each vehicle is also recorded in detail. Through the actual comparison, it can also be seen which kind of post-processing system is more advanced, which is beneficial to the improvement of product performance. ' Fang Xiyu said.
Judging from the current situation, China's motor vehicle aftertreatment technology has matured. The joint efforts of advanced technologies and an efficient monitoring platform will effectively control the pollution of motor vehicles and help protect the blue skies.