News; Reducing diesel engine exhaust emission control technologies

Published: Saturday 15 October, 2011


Diesel particulate filter, to exhaust particulate does not make it overboard discharge and used catalyst, oxidization, decomposition and combustion of burner. Lee device can reduce harmful substances in diesel exhaust particles 70%~90%. Used to trap particulate filter material and structure there are many, a common monolithic ceramics, metal mesh, textile fiber, ceramic fiber, ceramic foam. Trapping of principle is generally believed that these filter materials are as follows:


1. collision mechanism: diesel engine exhaust gas flow through the capturing unit, its happened many times turn the flow line, at the current corner, since most movement inertia of larger particles out of the flow line and collision trap unit, and absorption or deposited on it.
2. the closure mechanism: diesel engine exhaust gas flow through the trap occurs when the cell either, one size larger than the pore filter material particles is blocked and not glued to live, that is sieving effect; the second is the particle size smaller than the filter material pore due to adhesion and aggregation and some closure.


3. diffusion principle: particles in diesel exhaust gas molecular thermal motion caused by the collision of Brownian motion, the county seat the smaller particles, the more significant, will be the diffusion effect. When the exhaust gas flow through the trap unit, fiber-like trapping of particles from the movement of the cells into a convergence effect, which makes it possible to be particulate.


4. gravity settling mechanism: when slow when you run a diesel engine exhaust gas flow through the trap, exhaust stay longer, larger particles may occur in the role of gravity for precipitation from the displacement of the flow lines on the collection unit. Exhaust particulate filter installed in the system, it might make diesel engine exhaust back pressure increased. Power is reduced, trapping particles of material deposited on the more exhaust back-pressure is higher.


Therefore, you must periodically clear the sediment particles on the filter material.


Clear process of sediment particles on the filter material to trap regeneration. Under the working engine speed and load, exhaust temperature is generally 250~500℃, and particle normal ignition is 550~600℃, rely on the regeneration of diesel engine exhaust is difficult to trap. To put the trap regeneration must reduce particle ignition or increase the exhaust temperature. By adding additives or filter material in the fuel coated catalyst layer reduces particle ignition point, enabling the particulate to burn at lower temperatures, generally called active regeneration.
The other is the use of external energy sources, such as electric heater heating afterburning and afterburning burner heating to increase exhaust temperature will trap particles burn on the material, commonly known as passive regeneration. Passive regeneration is a periodic regeneration, detection and control of complex techniques to determine regeneration time. Currently, trap regeneration regeneration of active and passive regeneration technology combining results are obvious.

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