Is an SCR a catalytic converter?
A Selective Catalytic Reduction (SCR) system uses a metallic or ceramic wash-coated catalyzed substrate, or a homogeneously extruded catalyst and a chemical reductant to convert nitrogen oxides to molecular nitrogen and oxygen in oxygen-rich exhaust streams like those encountered with diesel engines.
What is the SCR on a Cummins motor?
Selective Catalytic Reduction
The Selective Catalytic Reduction (SCR) system is an advanced exhaust after treatment system to reduce NOx. The engine controls the production of PM by increasing the combustion temperature thus limiting it within the permissible value.
What is SCR treatment?
Selective catalytic reduction (SCR) is a technology used to reduce the level of nitrogen oxides (NOx) in the presence of a catalyst. Vaporized reagent (Ammonia or Urea) is injected into flue gas and reacts with NOx on the SCR catalyst resulting in nitrogen (N2) and water (H2O).
How effective is SCR?
Achievable Emission Limits/Reductions: SCR is capable of NOx reduction efficiencies in the range of 70% to 90% (ICAC, 2000). Higher reductions are possible but generally are not cost-effective.
Can you clean a SCR catalyst?
SCR catalyst systems need to be cleaned to remove contaminants and plugs. If the catalyst is not kept clean and the ammonia injection system is not tuned, ammonia slip occurs.
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 does SCR mean in power generation?
The selective catalytic reduction (SCR) removes nitrogen oxides (NOx) from flue gas emitted by power plant boilers and other combustion sources, and the catalyst is the key component of this system.
Why SCR is used in power plant?
Can SCR get clogged?
In some cases, though, it is possible for the SCR to become clogged. As mentioned above, the filter needs to be dosed with a chemical reactant—usually either urea or Diesel Exhaust Fluid (DEF) to formulate chemical reactions successfully.
What is the function of a SCR?
The basic purpose of the SCR is to function as a switch that can turn on or off small or large amounts of power. It performs this function with no moving parts that wear out and no points that require replacing.
What is the difference between a SCR and a thyristor?
Generally, SCR and Thyristor are used interchangeably but SCR is a kind of Thyristor. Thyristor includes many types of switches, some of them are SCR ( Silicon Controlled Rectifier ), GTO (Gate Turn OFF), and IGBT (Insulated Gate Controlled Bipolar Transistor ) etc. But SCR is the most widely used device, so the word Thyristor become synonymous to SCR.
How does a SCR turn on?
As mentioned earlier, the SCR can be switched on either by increasing the forward voltage beyond forward break over voltage V FB0 or by applying a positive gate signal when the device is forward biased. Of these two methods, the latter, called the gate-control method, is used as it is more efficient and easy to implement for power control.
How does a SCR conduct?
An SCR conducts when a gate pulse is applied to it, just like a diode. It has four layers of semiconductors that form two structures namely; NPNP or PNPN. In addition, it has three junctions labeled as J1, J2 and J3 and three terminals(anode, cathode and a gate). An SCR is diagramatically represented as shown below.