SCR Exhaust Gas Post-treatment System of Dual Reduction Type
Product Technical Approach
According to the requirements of transformation and treatment ofin-service diesel vehicle market, the product should meet not only the requirementsof reducing particulate matter (PM) in exhaust gas, but also meet therequirements of reducing nitrogen oxides (NOx). Therefore, Sinocat has speciallydeveloped a dual reduction post-treatment product (DOC+DPF+SCR) for dieselautomobile to better satisfy market demand.
Working principle of Post-treatment Products of dual reduction(As shown on the right).
Sinocat has successfully developed a DOC+CDPF+SCR dual reduction post-treatment product by integrating Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), and NOx Selective Catalytic Reduction (SCR) (a catalytic converter with a precious metal catalyst coated on a DPF carrier, namely CDPF). On the one hand, the DOC in this product oxidizes NO to NO2 in an appropriate temperature range, providing sufficient NO2 for the downstream CDPF to achieve passive regeneration smoothly, while also supplying NO2 for the rapid reduction reaction for SCR. On the other hand, by using excellent fuel ignitability of DOC, CDPF’s active regeneration can be realized smoothly, improving CDPF’s active regeneration efficiency, reducing fuel consumption, therefore booting economic efficiency of fuel.
The DOC+CDPF+SCR system integrates numerous modern high technologies such as precious metal catalysts for diesel automobiles, selective catalytic reduction technology, polymer ceramic materials, high-precision sensor technology, SCR injection control technology and online supervision and alarm technology. It is the industry-leading product of China’s road diesel exhaust emission control technology.
The product monitors the internal working conditions of the system in real time through temperature and pressure sensors, and uploads the informations to the monitoring platform of the modified vehicle. At the same time, it precisely controls the treatment of NOx through multiple temperature and nitrogen-oxygen sensors, gas flow or speed sensors
By optimizing the integrated system of DOC+CDPF+SCR, the CO, HC, NOx and PM in exhaust gas of reformed diesel engine are significantly reduced and meet emission requirements. After the product is installed, fuel consumption increases by no more than 5% and urea consumption will not exceed 5% of fuel consumption.
Product Categories
The product of DOC+DPF+SCR developed by Sinocat for diesel automobiles includes air-assisted and non-air-assisted exhaust gas post-treatment system. According to different layout of the original car, products with different structures are designed.
Three Structures ofthe Product
"一" ShapeStructure
Such a structure is simple, practical and detachable. It issuitable to replace the truck with cylindrical muffler at the bottom of thevehicle, or the vehicle with the original muffler in “one” shape atthe bottom of the vehicle.
“S” Shaped Structure
Such structure is relatively compact, with the front and rear barrels being connected side by side or at different angles, and the detachable design is suitable to replace the original muffler on the side of the car.
Box-type Structure
It is the most compact structure and is very suitable to replace the square muffler on most of the diesel trucks. Thanks to the direct replacement of the original muffler, the product can be installed through original method at the fixed position of original muffler, which is convenient and secure. In this way, the structure of the whole vehicle will not change and its safety is guaranteed.
Product performance parameters:
Product Performance Parameters
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Control Strategy
The control strategy of Sinocat is an open-loop control strategy based on the model, which adopts the dual nitrogen oxygen sensor and adds the feedforward control link.(As shown on the right)
Adaptability of Fuel
F-diesel products can adapt to National V stage of diesel vehicle (sulfur content S≤10ppm). The Company’s pre-sales and after-sales techniciansand instructions will also emphasize and stipulate that the use of diesel fuelabove National IV standard is mandatory, which means that the sulfur content mustbe lower than 50PPM. If our company’s after-sales personnel have doubts aboutthe use of substandard diesel oil, they can negotiate with customers to samplethe diesel oil in the tank under the condition of third-party authenticationand send it to a third-party professional testing agency for oilidentification.
The catalyst utilized in this system exhibits excellent sulfur resistance and is capable of operating for at least 200 hours with 350 ppm fuel. If the truck driver accidentally adds substandard oil, it will not have an irreversible impact on the whole system in a short time.
The catalyst utilized in this system exhibits excellent sulfur resistance and is capable of operating for at least 200 hours with 350 ppm fuel. If the truck driver accidentally adds substandard oil, it will not have an irreversible impact on the whole system in a short time.
Experiments have also been performed on thefuel even with a sulfur content of 3500 ppm. Although continuous operation ofthe catalyst for approximately 20 hours, its performance has been significantlydiminished.
EXPERIMENTAL TRANSFORMATION DIAGRAM OF SULFUR RESISTANCE OF CATALYSTS
After switching to diesel of National V standard, the sulfates covered on catalyst will be removed from the catalyst surface (SO3&SO4) after approximately 30 minutes at 350°C or above. It is also observed that the catalyst can be regenerated smoothly for desulfurization, with a significant recovery in performance, which basically attains the initial performance state. Hence, it is proved that the modified catalyst can withstand diesel fuel with high sulfur content for a short time to the utmost extent.
After extracting the online monitoring data of 100 diesel vehicles, it is found that the exhaust temperature above 350℃ will also occur. In addition, if the DOC effect decreases, the regeneration performance of CDPF will also decrease, and the increase of back pressure will lead to the increase of engine exhaust temperature. We can also heat and regenerate the post-treatment system during maintenance to ensure that the service life of the system is not limited by occasional accidents.
Image of Product (Image of S-type Product of Dual Reduction)
Passive Diesel Particulate Filter (DPF)
Product Technical Approach
DPF (Diesel Particulate Filter) is alsoknown as DPF Exhaust Post-treatment System, after a long time of particulatecapturing, the porous media channels of the filter will be blocked, which willresult an increase of back pressure within the exhaust system, thus affectingthe normal operation of the engine. Therefore, it is necessary to adoptmeasures to remove the carbon soot particles filtered by DPF and restore thefiltration capacity of the DPF, which is termed as regeneration. Regenerationapproaches are generally categorized as active and passive regenerations.
The products developed by Sinocat are designed to reduce theemission of pollutants such as CO and HC in exhaust gas through DOC catalyticoxidation reaction, while DOC oxidizes NO to NO2 in exhaust gas. At the propertemperature, the passive regeneration of PM captured by CDPF (a catalyticconverter coated with a layer of catalyst on a DPF carrier, known as a CDPF) willbe realized. Upon fulfilling the conditions for active regeneration, thecontrol unit manages the injection device to inject fuel in front of the DOC,and the exhaust temperature is greatly increased by DOC, so that the PM in CDPFcan be regenerated. The catalytic performance of DOC and the filteringperformance of the CDPF contribute to the purification of exhaust gases.
The company’s products are tested according to the test standard of Ministry of Ecology and Environment, and industry test standard (HJ451-2008). The conversion efficiency of DOC of catalyst for HC and CO exceeds 80%, the capturing efficiency of DPF for particulate matter reaches more than 90%, while the regeneration efficiency of particulate matter attains over 90%.
The control unit monitors the temperature of the catalyst and thepressure difference before and after CDPF, and judges whether the regenerationis needed according to the carbon load and working conditions. If regenerationis needed, the controller will regulate the regeneration system and it isequipped with remote online monitoring device.
In view of the actual situation of diesel vehicle emissions inuse, the longitude and latitude of different regions and the temperature inwinter, Sinocat provides two different schemes of modifications, whoseprincipal difference lies in the varying regeneration technology approaches, soas to meet the transformation requirements of diverse automobiles.
Product Categories
Adaptability of fuel
The products of Sinocat can adapt toNational V stage for diesel automotive (sulfur content S≤10ppm)
Product SafetyRequirements
Product Installation
(1) Product Installation
Remove the muffler of the original vehicle, install the product behindthe engine exhaust manifold, and fix it on the vehicle frame. While ensuringthe installation space of catalytic muffler, the distance from the engineshould be minimized. When necessary, the exhaust pipe should be insulated, andthe maximum distance after insulation should not exceed 2000mm.
After the installation of the product, it ensures that the original safety performance o the vehicle is unchanged and meets the relevant safety regulations. In view of safety of system control strategy, the control system will mandatorily terminate the active regeneration of the product under some special circumstances and occasions, including terminating the active regeneration process after parking and in special occasions (such as gas stations, flammable and explosive places, etc.).
(2) Structural Safety
All products, mounting brackets and other accessories shall be made of materialsmeeting the strength requirements of the whole automobile, to prevent theproducts from fracturing and falling off by severe vibration during driving.The structure and size of the muffler are similar to those of the originalvehicle, which will not affect the original safety performance of the vehicle. Excellentinsulation measures are in place to prevent fire or personnel scald caused byhigh temperature.
(3) Security of Control Strategy
Precise regeneration condition evaluation ensures the product regeneration in atimely and effective manner. As a result, it is necessary to specify stringentregeneration condition threshold, including vehicle speed, exhaust temperature,CDPF back pressure, setting value of cumulative operation time for regeneration,and mandatory termination of active regeneration after parking or under specialoccasions (such as gas stations, flammable and explosive places, etc.).
The power is taken from the standby terminal of the originalvehicle, and the system will automatically power off after parking, withoutaffecting the electrical system of the vehicle. The system is equipped with itsown gas source, therefore, there is no need to take gas from the originalvehicle, which will by no means affect the braking performance of the vehicle.
Passive Type of DPF Exhaust Gas Post-treatment System
Principle of Regeneration
The passive type of DPF exhaust gas post-treatment system employsa passive regeneration scheme. Passive regeneration relies on DOC, whichoxidizes NO in the exhaust gas to NO2. NO2 reacts with carbonsoot in DPF to remove carbon particles and realize passive regeneration. At thesame time, a layer of catalyst (CDPF) is coated on the DPF carrier to reducethe reaction temperature between carbon particles and NO2, to increasethe temperature interval for passive regeneration and to improve the efficiencyof passive regeneration.
Product Structure
Products of both modified solutions adopt the structure of DOC+CDPF catalytic muffler with direct air intake or side air intake. According to different engine displacements, the products with different diameters and lengths are designed. The overall structure and size are similar to the original muffler, it can be installed after the original muffler is removed. The installation height is equivalent to that of the original muffler, so as to ensure that the trafficability of the vehicle will not be affected.
The products of Sinocat has high maintainability. CDPF is designed as a detachable structure. When there is a lot of unburned ash in the device, the CDPF can be easily disassembled. Dedicated device is used to blow out the ash through compressed air, and the blown air is filtered by water, which poses no impact on the air quality. There is no additional vent for the product, which can eliminate emission falsification at the source.
Regeneration Conditions
The DOC oxidizes NO from the NOx in the engine exhaust to NO2. When thetemperature is between 250°C and 500°C in exhaust process, NO2reacts with the particles in the DPF catalytic converter. The passiveregeneration theory is given as follows:
C+NO2_CO+NO
C+2NO2_CO2+2NO
Passive-type product requires good performance of catalyst, and has certain requirementson original emissions of the vehicle, operating condition of the vehicle, andquality of the fuel. And the application of this kind of catalyst is relativelylimited.
Thermal Management Solutions
The First Solution:
For both of the modified solutions developed by Sinocat, their thermalmanagement solutions are designed to incorporate a heat shield (commonly knownas an “thermal insulation jacket”) on the exterior of the productbody. The functions of the heat shield are as follows:
— It features a sound absorption rate of more than 90%, which isresistant to noise, exceeding the average requirements of NRC;
— It is characterized by good toughness and corrosion resistance,and its heat resistance is up to 700℃;
— It offers high tensile strength, so it will not produce any dust；
— It possesses extremely low shrinkage and long service life at hightemperature;
— The high sound absorption rate can achieve the effect of noisereduction, while high thermal insulation and heat resistance enable fuel toreact fully at high temperature in the exhaust pipe, thus attaining goal of lowemission
TechnicalRequirements for the Heat Shield:
– The heat shield is an inorganic fiber composite product, whose physical andchemical properties are as follows: thermal conductivity at roomtemperature is ≤0.04W/mK. Tensile Strength is ≥ 0.72MPa, non-flammability isgrade A, and the safe use temperature is ≤ 600 ℃. The heat shield shall not be changed,broken, peeled off, agglomerated, dropped or dusted.;
— The heat shield shall not burn and produce toxic substances andgases;
— During installation of the heat shield, it should be fitted on theexterior surface of the pipe, and it is required to fit tightly;
— It is required to connect the joint pinsof the heat shield through the round holes of the cotter pins on both lapjoints in sequence and tighten them.
The Second Solution:
Fuel injection will be discontinued when the temperature at theDOC outlet is higher than the set value, or when the temperature at the CDPFoutlet is higher than the set value. Both methods can achieve thermalmanagement effect.
Solutions for low temperatureenvironment and unachievable regeneration conditions
The passive-type product of DPF post-treatment system increasesthe probability of passive regeneration by adding catalyst coating and a layerof heat shield. In the cases of low temperature and the failure to achieveregeneration conditions, it is recommended that the driver shall increase theload, or drive at high speed for 15-30 minutes, or consider dismantling or conductingregular manual maintenance of the CDPF to remove the soot, such as taking emergencymeasures for back blowing of high-pressure air flow.
Surveillance Terminals
Remote Online Surveillance System
The online surveillance system for vehicle exhaust post-treatment devicedeveloped by Sinocat consists of 2 parts: remote online surveillance platformand surveillance terminal. The integral structure and function of the onlinesurveillance system are illustrated as follows:
Surveillance Terminal
The surveillance terminal developed by Sinocat serves as a terminal device forreal-time measurement and monitoring of automobile exhaust emissions duringdriving. The monitoring terminal equipment has the functions of fault alarm andremote online monitoring alarm. It is installed in driver’s cab where it iseasy for the driver to see, and has clear indication signs. The signs containthe product maintenance requirements, fault alarm information processingmethods and after-sales service contact methods and other informations (see theafter-sales operation manual for the signs). The surveillance terminal deviceof Sinocat is shown in the figure below:
— The surveillance terminal developed by the Company is capable of transmitting data to 2 surveillance platforms simultaneously, in order to satisfy the respective needs of government departments and post-treatment product providers. Such surveillance terminal can be operated not only for commercial vehicle exhaust emission, but also for passenger vehicle for the purpose of monitoring and data acquisition and processing. The data collected and transmitted are as follows:
— Uploading relevant information parameters of engine, including vehicle speed, torque, revolutions per minute (RPM), instantaneous fuel consumption, throttle opening, air intake flow, gear, engine temperature, etc.;
— Uploading relevant data concerning exhaust gas post-treatment product, including intake manifold temperature/pressure, post-treatment system temperature and pressure, carbon load, pressure difference, fuel injection volume, urea level, urea pump working status, nitrogen and oxygen concentration, etc, and possessing functions of vehicle management, system management, report statistics, etc.;
— Uploading informations such as product manufacturer, installation company, vehicle owner, vehicle license plate, etc.;
— Recording the informations processed by government authorities and regulatory agencies, such as vehicle emission detection data from vehicle testing agencies, and penalty information for vehicles of illegal emissions;
— The informations of OBD include at least the following details: MIL alarm, diagnostic support, diagnostic availability, fault code, VIN, calibrated software identification number, calibrated verification code and IUPR;
— Being capable of reading engine data streamed from CAN communication interface: RPM, torque, fuel injection volume, NOx emission data, air intake volume, exhaust temperature, DPF pressure difference, urea level, cooling water temperature, longitude and latitude, etc.;
— Data acquisition and transmission frequency is 1Hz.
Thelogical conditions for the alarm of Sinocat products are as follows:
— When the temperature at the DOC outlet is higher than the threshold set bythe system, the system will give an alarm;
— Whenthe temperature at the CDPF outlet is higher than the threshold set by thesystem;
— Whenthe temperature at the SCR outlet is higher than the threshold set by the system;
— When the differential pressure at the CDPFexceeds the alarm threshold and the maximum threshold set by the system;
— Whenthe value of the differential pressure is less or greater than the thresholddue to malfunction or poor contact of the differential pressure sensor;
— Whenthe value of nitrogen and oxygen concentration is greater than the thresholdset by the system;
— Whenthe liquid level sensor fails;
— When the switch ofthe regeneration control panel fails.
Emergency disposal plan for fault alarm ofSinocat products
Each set of remote online monitoring terminal equipment should be clearly anduniquely identified to ensure that the relevant parameters on the platform arecompletely matched with the installed vehicle information and vehicle operationstatus. In case of product failure alarm, the company provides a complete and detailedemergency plan:
[1] The company has personnel who is in charge of the dataanalysis and processing of the online surveillance platform everyday, which canidentify and solve problems in a timely manner.
[2] Automatic statistical analysis of vehicles’ online status will be conductedby the company’s online surveillance platform on a regular basis to evaluatewhether the products and vehicles are running properly. Moreover, regardingsome alarm parameter sets, the alarm will be activated through the platform window,in which the personnel in charge will immediately receive the alarm informationfor timely processing and communicate with the repairing workshop simultaneouslyfor product maintenance. Meanwhile, by monitoring certain data informationthrough the platform, it will ensure that the vehicle owners will by no meansdismantle the installed products without permission.
[3]When the monitoring terminal equipment encounters problems, it canautomatically alert the driver and send the alarm information to thesurveillance platform through the surveillance terminal, thereby ensuring thesafety of the vehicle.
On-line Monitoring System for Vehicle Exhaust Temperature and Back Pressure
Related Surveillance Terminal Equipment
Related surveillance terminal equipments developed by Sinocat consist of wire harnesses, sensors, etc..
Burner Type Diesel Particulate Filter (DPF)
Product Technical Approach
DPF (Diesel Particulate Filter) is also known as DPF Exhaust PostprocessingSystem, after a long time of particulate capturing, the porous media channelsof the filter will be blocked, which will result in an increase of back pressurewithin the exhaust system, thus affecting the normal operation of the engine. Therefore,it is necessary to adopt measures to remove the carbon soot particles filteredby DPF and restore the filtration capacity of the DPF, which is termed asregeneration. Regeneration approaches are generally categorized as active andpassive regenerations.
The products developed by Sinocat are designed to reduce theemission of pollutants such as CO and HC in exhaust gas through DOC catalyticoxidation reaction, while DOC oxidizes NO to NO2 in exhaust gas. At the propertemperature, the passive regeneration of PM captured by CDPF (a catalyticconverter coated with a layer of catalyst on a DPF carrier, known as CDPF) willbe realized. Upon fulfilling the conditions for active regeneration, thecontrol unit manages the injection device to inject fuel in front of the DOC,and the exhaust temperature is greatly increased by DOC, so that the PM in CDPFcan be regenerated. The catalytic performance of DOC and the filteringperformance of the CDPF contribute to the purification of exhaust gas.
The company’s products are tested according to the test standardof Ministry of Ecology and Environment, and industry test standard (HJ451-2008).The conversion efficiency of DOC of catalyst for HC and CO exceeds 80%, the capturingefficiency of DPF for particulate matter reaches more than 90%, while theregeneration efficiency of particulate matter attains over 90%.
The control unit monitors the temperature of the catalyst and thepressure difference before and after CDPF, and judges whether the regenerationis needed according to the carbon load and working conditions. If regenerationis needed, the controller will regulate the regeneration system and it isequipped with remote online monitoring device.
In view of the actual situation of diesel vehicle emissions inuse, the longitude and latitude of different regions and the temperature inwinter, Sinocat provides two different schemes of modifications, whose principaldifference lies in the varied regeneration technology approaches, so as to meetthe transformation requirements of diverse automobiles.
Product Categories
Adaptability of Fuel
The products of Sinocat can adapt toNational V stage for diesel automotive (sulfur content S≤10ppm)
Product Safety Requirements
（1）Product Installation
Removing the muffler of the original vehicle, installing theproduct behind the engine exhaust manifold, and fixing it on the vehicle frame.While ensuring the installation space of catalytic muffler, the distance fromthe engine should be minimized. When necessary, the exhaust pipe should beinsulated, and the maximum distance after insulation should not exceed 2000mm.
After the installation of the product, it ensures that theoriginal safety performance of the vehicle is unchanged and meets the relevantsafety regulations. In view of safety of system control strategy, the controlsystem will mandatorily terminate the active regeneration of the product undersome special circumstances and occasions, including terminating the activeregeneration process after parking and in special occasions (such as gas stations,flammable and explosive places, etc.).
(2) Structural Safety
All products, mounting brackets and other accessories shall be made of materialsmeeting the strength requirements of the whole automobile, to prevent theproducts from fracturing and falling off by severe vibration during driving.The structure and size of the muffler are similar to those of the originalvehicle, which will not affect the original safety performance of the vehicle. Excellentinsulation measures are in place to prevent fire or personnel scald caused byhigh temperature.
(3) Security of Control Strategy
Precise regeneration condition evaluation ensures the product regeneration in atimely and effective manner. As a result, it is necessary to specify stringentregeneration condition threshold, including vehicle speed, exhaust temperature,CDPF back pressure, setting value of cumulative operation time for regeneration,and mandatory termination of active regeneration after parking or under specialoccasions (such as gas stations, flammable and explosive places, etc.). Thepower is taken from the standby terminal of the original vehicle, and thesystem will automatically power off after parking, without affecting theelectrical system of the vehicle. The system is equipped with its own gassource, therefore, there is no need to take gas from the original vehicle,which will by no means affect the braking performance of the vehicle.
The power is collected from the spare terminal of the original vehicle, and the system automatically loses power after parking, without affecting the electric system of the vehicle. With its own air source, the system does not need to take air from the original vehicle, and does not affect the braking performance of the vehicle.
DPF Exhaust Gas Post-treatmentSystem Combustor Type
Principle of Regeneration
The DPF exhaust gas post-treatment system combustor employs acombination of active + passive regenerative combustor scheme. As the passiveregeneration scheme is identical to that of the DPF exhaust gas post-treatmentsystem, it will not be presented here. The combustor ignition regenerationsystem utilizes operating time (8 hours of continuous operation) + pressure differenceto detect the carbon soot load in CDPF, thereby triggering active regeneration.By controlling the fuel injection volume, air intake volume, the controllerwill combust the injected fuel in the combustor and rapidly raise the exhaustgas temperature, so that the temperature at the inlet of CDPF can reach morethan 500°C and realize the active regeneration of CDPF.
In this system, a suitable operating condition is selected forregeneration, and closed-loop control is adopted to monitor the temperature atthe front and rear end of the DOC and regulate the fuel injection volume andair volume in order to ensure the required temperature for regeneration whileavoiding damage to the CDPF carrier by uncontrolled regeneration.
Product Structure
① Passive type of DPF exhaustgas post-treatment system
Regeneration Conditions
Ascan be seen from the figure above, the regeneration condition for products ofthis system is as follows: the regeneration of the combustor can be realized undermedium exhaust flow rate within 300℃.
Active RegenerationDevice Structure
Regeneration Control Strategy
The combustor ignition regeneration system utilizes operating time(8 hours of continuous operation) + pressure difference to detect the carbonsoot load in the CDPF, thereby triggering active regeneration. By controllingthe fuel injection volume, air intake volume and the fuel injected by theignition plug, the controller will combust the fuel in the combustor andrapidly raise the exhaust gas temperature, so that the temperature at the inletof CDPF can reach more than 500°C and realize the active regeneration of CDPF.
Thermal Management Scheme
Passive type of DPF exhaust gas post-treatment system
