What is SCR in diesel generator?
Selective Catalytic Reduction (SCR) is a proven and advanced active emissions control technology system that injects a liquid-reductant agent through a special catalyst into the exhaust stream of a diesel engine. The reductant source is usually automotive-grade urea, otherwise known as Diesel Exhaust Fluid (DEF).
What is SCR in Genset?
Selective Catalytic Reduction for gensets (also know as SCR) will reduce NOx emissions by combining exhaust gases with the reductant AdBlue (a type of urea) and passing it over a catalyst. AdBlue is 32% ammonia dissolved in purified water. It is handled in diluted form as it is much less harmful.
How does SCR work diesel?
An SCR (Selective Catalytic Reduction) system is a system installed on diesel vehicles to reduce harmful Nitrous Oxide (NOx) emissions. It works by injecting an automotive grade urea, or Diesel Exhaust Fluid (DEF) through a specially designed catalyst, into the exhaust stream of a diesel engine.
What is the difference between DPF and SCR?
A DPF’s core can be made of a few different materials but the most common are cordierite composites. An SCR catalyst has valuable filter contents in the form of ceramic materials and precious metals.
What causes SCR failure?
Temperature/Overheating Inadequate cooling of semiconductors such as SCR and Diodes can and will cause devices to fail prematurely, some in a matter of minutes depending on the amount of current being carried. If you are experiencing recurring device failure it may be caused by a lack of cooling.
Where is the SCR located?
In general, the SCR unit is located between the furnace economizer and the air heater, and the ammonia is injected into the catalyst chamber through an ammonia injection grid. As in other SCR applications, the temperature of operation is critical.
How does a SCR work?
SCR stands for silicon controlled rectifier. It is essentially a switch with no moving parts. It consists of a semiconductive path and what is called a bridge. When you apply voltage across the bridge, the path becomes conductive and carries the current until something interrupts the current ahead of the SCR.
Which comes first SCR or DPF?
Selective Catalytic Reduction is a separate component from the DPF in most applications, at least functionally if not physically. SCR is used to reduce Nitrogen (Di) oxide emissions from diesel engines which is again harmful.
What happens when an SCR fails?
If an SCR fails short you lose control to the load. So I have added a second set of SCRs for redundant control. One set controls the “Line side” of the load and the “Return-side”, such that if one SCR fails the other set of SCRs would allow control of the power.
How do I know if SCR is working?
To test the SCR, connect the positive output lead of the ohmmeter to the anode and the negative lead to the cathode. The ohmmeter should indicate no continuity. Touch the gate of the SCR to the anode. The ohmmeter should indicate continuity through the SCR.
What is inside a diesel SCR?
Several nitrogen-bearing reductants are currently used in SCR applications including anhydrous ammonia, aqueous ammonia or dissolved urea. All those three reductants are widely available in large quantities. Anhydrous ammonia can be stored as a liquid at approximately 10 bar in steel tanks.
How SCR is triggered?
To trigger, or fire, an SCR, voltage must be applied between the gate and cathode, positive to the gate and negative to the cathode. When testing an SCR, a momentary connection between the gate and anode is sufficient in polarity, intensity, and duration to trigger it.
How do SCR fail?
Temperature/Overheating. Inadequate cooling of semiconductors such as SCR and Diodes can and will cause devices to fail prematurely, some in a matter of minutes depending on the amount of current being carried. If you are experiencing recurring device failure it may be caused by a lack of cooling.
Can SCR convert AC to DC?
An SCR converts an AC voltage to a DC voltage. Unlike a diode that turns on when . 7V travels across the anode and cathode, an SCR includes a gate lead that requires a trigger to activate the on-state condition.
How is SCR controlled?
SCR s are controlled by a small control current through the terminal called the ‘gate’ or ‘trigger’. The output current controlled is huge by comparison (just like a relay), but there is no arcing and no contacts to pit.
Can you clean a diesel SCR?
The good news is that SCRs typically require little to no ongoing care or maintenance. Once in place, they should do their jobs without much interference from you. In some cases, the filter will need to be dosed with the chemical reactant it uses to catalyse the reaction with the NOx emissions.