As more and more regions in the country begin to popularize the five national emission standards, the engines of the fifth national emission are drawing more and more attention. Each engine company has its own technology to achieve the five national standards. However, in the past 20 years, with the acceleration of the emission standard upgrade rate, it has been difficult to catch up with the emission standards simply relying on "in-house purification" technology. Therefore, it has to rely on the "external purification" technology to help.
Xichai Conway 4DW Engine
Currently, most of the engines on the market have reached the emission standards of the National 3 and 4 countries. For diesel engines that have reached the national 3 or 4 emission levels, there are two technical routes to achieve the 5th emission. One is the SCR technology route: SCR injection + post-processor, and the other is EGR technology route: EGR + DPF.
The popular SCR technology line is to use the aqueous solution of 32.5% high-purity urea to treat the nitrogen oxides in the exhaust gas. The PM pellets are first reduced to an emission limit of 0.02 by â€œin-house purificationâ€ (increasing injection pressure/optimizing combustion, etc.). Below g/kW.h, NOx will increase and then decrease the NOx to 2g/kW.h limit value through SCR.
The EGR technology route first reduces the NOx to below the emission limit of 2.0 g/kW.h through "in-house purification" (cooling EGR/increasing injection pressure/VGT, etc.), and then reduces PM particles to 0.02 g/kW.h through DPF. Within limits.
In the domestic market, almost all other similar products adopt the SCR technology route, and Xichai's Conway 4DW State V adopts the EGR+DPF program, in which the DPF system is divided into two parts before and after, namely the pre-DOC+ post-stage DPF.
DOC (diesel oxidation catalyst), the acronym for diesel oxidation catalysts, coats precious metal catalysts (such as Pt, Pd, etc.) on honeycomb ceramic carriers or metal honeycomb carriers to reduce hydrocarbons (Cn Hm) in diesel exhaust. The activation energy of chemical reactions such as soluble organic components (SOF) in carbon monoxide and particulates allows these substances to undergo oxidation reaction with oxygen in the exhaust gas at a relatively low temperature and convert them into carbon dioxide and water. At the same time, high temperatures are generated during regeneration, which promotes DPF regeneration.
DPF (diesel particulate filter), the acronym for Diesel Particulate Filter, captures more than 95% of carbon particles in diesel emissions. The carbon particles captured by the DPF postprocessor can be oxidized with the NO2 in the exhaust gas. The exhaust temperature can reach 200 degrees. Therefore, the carbon particles can be removed by the oxidation reaction while the car is traveling normally. If the time is long, the DPF post-processor regeneration may be forced to return the carbon particles to the initial state of combustion so as to achieve the purpose of repeated use of the DPF post-processor.
Xichai Conway 4DW State Five Engine EGR+DPF Aftertreatment System
What are the advantages and disadvantages of the two technical routes?
The SCR technology route, based on the four engines of the original country, can improve the SCR's working ability and meet the national five emission standards. The engine's main body does not substantially change. This feature makes SCR become the country's current five-phase mainstream technical route. The disadvantage is that urea needs to be consumed during the entire vehicle operation, and urea crystallization occurs when the exhaust gas temperature is low.
EGR + DPF technology route, the engine body changes greatly, increased electronically controlled throttle, EGR valve, EGR cooling system. Compared with the SCR technology line, no need to consume urea, to avoid the risk of crystallization, while reducing the cost of use; and basically do not need to use the maintenance later, only two or three times after the DPF postprocessor ash handling.
The EGR+DPF technology route control system is complex and technically difficult. The biggest risk is the blockage of the DPF's postprocessor. For this reason, Xichai adopts various technical measures to deal with it, such as regular forced regeneration, forced differential pressure regeneration, and forced regeneration of carbon load. , forced regeneration of diagnostic equipment.
Xichai Conway 4DW has five engine displacements of 2.54L. Its exhaust temperature is relatively low compared to large displacement engines. If SCR technology is adopted, urea injection at relatively low temperatures is also required to meet emission standards. The small diameter of the exhaust pipe will lead to crystallization of urea during the entire vehicle operation. Therefore, the selection of EGR+DPF technology route is the fourth national road of Xichai 4DW.
Sand Making Machine used to produce artificial sand & plaster sand; sand manufactured by crushing,The sand making machine is specially designed for manufacturing artificial sand from the grit. It is a better utilization of the large size of rock materials and stones through rock on rock metal machine mechanism roughly as follows-
Sand and gravel aggregate play an important role in making up building materials like concrete, which makes the separation and screening process extremely necessary.
Sand making production line is also called sand and stone production line. And the sand production line is a kind of special equipment for producing construction sand and stone. The sand making machine for sale is often needed in many fields, and this processing line can meet the requirements of simultaneous production of stone and artificial sand.
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Three Systems of Sand Plant Equipment:
sand plant mainly has three systems. Here is their basic information:
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Sand Making Equipment
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