National IV will elaborate on SCR

It is still more than four months before China’s heavy-duty trucks have implemented IV emission standards. Is the technical route for the upgrading of heavy-duty diesel vehicles IV determined? What problems may arise in the future application process? On August 16th, the “China IV Diesel Emissions and SCR Technology Application Summit Forum” was held in Nanjing. Leaders from industry authorities, vehicle and engine companies, research institutes, related equipment suppliers and user representatives from all parts of the country gathered together to discuss possible problems with SCR technology after the implementation of the National IV Standard and the use of the previous SCR IV products. Experience exchanged.

There are still obstacles for the deadline to reach the implementing country IV

According to the regulations of the Ministry of Environmental Protection, the time for the implementation of IV emissions from heavy vehicles is January 1, 2012. With the approaching of this date, the attention of the entire industry to the National IV is getting higher and higher. Can national IV standards be implemented on schedule? Many people are still not at the bottom of their hearts.

According to statistics, in 2010, China's automobile NOx emissions were about 6 million tons (excluding non-road machinery), and heavy-duty diesel vehicles that accounted for less than 20% of the total car ownership emitted about 60% of NOx. The "Twelfth Five-Year Plan" requires that by the end of the "Twelfth Five-Year Plan", NOx emissions should be reduced by 10% compared with 2010.

According to the prediction of relevant experts of the Ministry of Environmental Protection, by the end of the “Twelfth Five-Year Plan”, if the quantity of heavy-duty vehicles is equal to that of 2010, and 50% of them meet the national IV emission standards, the NOx emissions of heavy-duty vehicles will decrease by 15% compared with 2010. the above. According to this indicator, it is not possible to achieve the binding NOx emission reduction targets in the “Twelfth Five-Year Plan”. At present, the mainstream diesel engine companies in China have technical reserves and upgrades for engines that meet the National IV emission standards. The vehicle manufacturers have obtained more than 2,000 IV models that have been announced by the Ministry of Environmental Protection.

At the same time, the uncontrollable problems in the automotive industry such as the construction of low-sulfur clean diesel and urea solution filling networks required for the implementation of heavy-duty vehicle IV emission standards will still partially affect the new emission standards that will be implemented as scheduled next year. .

SCR dominant country IV is a foregone conclusion

Regarding the selection of EGR or SCR as a technical route for the upgrading of heavy-duty diesel vehicles IV, domestic companies have already reached a consensus.



Compared with the EGR technology route, the engine with SCR technology has higher combustion efficiency, lower exhaust gas back pressure, higher fuel economy, and more in line with the general trend of energy conservation and emission reduction in China. Moreover, the use of SCR technology to upgrade the original engine is relatively small changes in the core parts of foreign technology dependence is also lower. In addition, another important reason for the domestic companies to choose SCR technology is that, compared with the EGR technology route, SCR has significantly higher tolerance to diesel fuels with higher sulfur content.

Since SCR was chosen, it had to suffer its shortcomings while enjoying its advantages. First, the use of SCR technology requires a selective catalytic reduction system installed on the vehicle to not only occupy space, increase vehicle weight, but also require the entire society to build a complete urea solution filling infrastructure; secondly, the use of SCR system The OBD monitoring system puts forward higher requirements. Engines and vehicle companies have increased the difficulty in the development of electronic systems. Third, the industry’s most controversial issue is the issue of integrity in the use of SCR systems, in which not only unscrupulous supply exists. The possibility of commercial inferior urea being sub-filled is even more worrying. If users do not use the SCR system under the drive of profits, they will have serious emissions problems.

It is worth mentioning that the reporter learned at the forum that despite the fact that the two major petrochemical giants that control the vast majority of gas stations in China have not yet started the infrastructure construction of urea solution filling equipment, urea solutions such as Jiangsu Kelansu Suppliers are cooperating with vehicle companies such as Yutong, which has a complete service network in the country, and provide users with urea solution filling services through the service network of the vehicle companies to meet the users' requirements for urea solutions.

Choose the right technology to choose the right product
Although the industry does not have much disagreement on the use of SCR technology in the national IV phase, the technical route is different from that of post-processing system manufacturers and urea solution suppliers. effect.

The public transportation industry first used SCR technology in China. In this seminar, Ge Weifen, Director of Technical Affairs Department of Nanjing Public Transport Corporation, reflected that the 50 Chinese buses using SCR technology purchased by the company at the end of 2010 had serious urea in May and June this year. As a result of the crystallization phenomenon, the exhaust pipe is severely blocked and the vehicle cannot travel. A technician from the company also reported that they had encountered similar "kidney stones" phenomenon in the bench test. This phenomenon may be related to the bus's long-term low-speed, low-load working conditions and the ability of the manufacturer to match the technology.

However, according to Zhang Minying, a senior engineer of the Shanghai Bus Group, more than 400 of their State IV buses using SCR technology have been used for a longer period of time, but no such situation has occurred. According to him, this aspect is that they have selected imported engines and related systems to match mature models; on the other hand, they have conducted rigorous assessment and bidding on the selection of urea solutions instead of simply selecting the cheapest products. , and in strict accordance with the technical regulations for filling, to avoid contamination of urea solution caused by improper operation.

According to Zhang Minying’s calculations, at present, the ratio of urea solution and fuel consumption of the China IV Bus Group IV vehicle is approximately 2.5%, and the average cost of urea is increased by approximately RMB 0.13 per liter of fuel, and the use cost is within the controllable range.

China has mature urea supplier
As an essential consumable of the SCR system, the quality of the urea solution is directly related to the exhaust of the entire vehicle and the life of the SCR system. At the forum, some experts have given a specific case: If a drop of sweat is accidentally dropped in a vat of urea solution, the index of various impurities such as sodium ions can exceed the limit.

At present, Jiangsu Kelansu Automotive Environmental Protection Technology Co., Ltd. is the only company in China that has obtained German VDA certification and its products comply with European standards. Its AdBlue urea solution has been exported to the United States, Europe, Japan, Singapore and other overseas markets, and its domestic market. The share has also reached 70%. According to Shi Junfeng, general manager of the company, the total demand for urea solution in the first year will be about 2 million tons in the first year after the implementation of national IV emissions from domestic heavy vehicles, and will jump to 4 million to 5 million tons in the second year. Very broad.

As a relatively young technology, the technology for SCR vehicle urea is still evolving, and related companies are also making active technical reserves. Under normal circumstances, the freezing point of urea solution is at -11°C, but this does not meet the requirements for use in winter cold regions such as the North. The development of urea solution products with a freezing point of -25°C and -35°C and adapting to a low-temperature climate requires enterprises to have considerable technical strength.

At present, in the automotive urea solution that meets international standards, water accounts for 67%. Its volume and weight have caused great waste on the car and logistics transportation. The development of solid urea products has become a frontier issue in the field of SCR.

According to Zhang Qiming, a technical center of FAW Group, vehicles that use urea solutions according to the standard design can travel 3000 to 8000 kilometers on a single refueling. If overload conditions are taken into account, this distance should be shortened to 2,000 to 5,000 kilometers. With solid urea, it is added once. Will be able to travel 15,000 to 20,000 kilometers.

Qualified oil supply is not optimistic
Although SCR's tolerance to sulfur content in diesel fuel is the highest among various technical routes, according to company technical personnel's estimation, if domestic companies want to implement the national IV standard normally, they still need the sulfur content of diesel fuel to be less than 350 ppm. In Europe, the sulphur content of diesel fuel meeting Euro IV standards must not exceed 50 ppm.

According to a report on the quality of diesel fuel carried out by China's Infineon in China, in 2010, China could only obtain diesel with a sulfur content below 350ppm in central cities such as Beijing and Shanghai, and a few economically developed regions. In most regions, the sulphur content of diesel is in the range of 500 to 1500 ppm.

From July 1 this year, the "Car Diesel" (GB19147-2009) standard has entered the mandatory stage. According to the standard, the sulfur content of diesel fuel should be less than 350ppm, and diesel fuel that fails to meet this standard is an unqualified product.

Judging from the market situation, the implementation of the standard has been more than a month. Except for the sale of low-sulphur diesel, which is a nominal clean diesel, in a few areas, gas stations in many regions have not responded. The reason is that due to cost issues, many refineries have not started to produce new standard diesel, and the supply of qualified oil products is not optimistic.

SCR use process supervision is difficult

Filling urea solution must increase the cost of use for the user, if you do not add urea according to the requirements of the enterprise, it will not directly affect the life of the vehicle like consumables such as engine oil and filter elements. Therefore, users have a lack of enthusiasm for actively filling urea solutions. If they rely solely on ethical constraints, the phenomenon of urea addition or non-increasing will certainly occur. This has already occurred in the European region where the Euro IV standard was implemented. Therefore, in our country, how to guarantee the user to add qualified urea solution after the implementation of State IV becomes an unavoidable problem.

According to experts, if a national IV diesel engine with an SCR technology route is used, if there is no urea solution for the catalytic reduction of NOx in the exhaust gas, engine emissions will not only fail to reach State IV, but even worse than State II, but will cause even more serious problems. Pollution.

In order to solve this problem, Europe has adopted the OBD system to monitor the SCR system. If the SCR system is not working properly, the vehicle will alarm, reduce the engine power and torque, until the flame is forcibly turned off, which restricts the user to some extent.

Some experts believe that in China, it is difficult to say whether this monitoring mechanism can achieve the same effect. Because both the quality of users themselves and the degree of compliance with laws and standards by enterprises, there is a certain gap between China and Europe. In order to ensure that State IV achieves the desired results in its implementation, relevant supervision and punishment systems must be quickly established and improved.