SCRsystem

SCRSystem refers to a selective catalytic reduction aftertreatment system used to lower nitrogen oxide (NOx) emissions from lean-burn diesel and gas engines. It is a common solution in on-road and non-road equipment, as well as in power generation and marine applications, to help meet stringent emission standards.

A typical SCRSystem includes an exhaust-based catalyst module, a urea storage and dosing subsystem, and an control strategy that coordinates injection and monitoring. The urea solution (often marketed as DEF or AdBlue) is stored in a tank, metered by a dosing unit, and injected into the exhaust stream where it hydrates and decomposes to ammonia. The ammonia then reacts with NOx over a SCR catalyst (commonly copper- or iron-zeolite formulations, or vanadium-based catalysts in some designs) to form nitrogen and water. The system is usually equipped with sensors to monitor NOx, ammonia slip, exhaust temperature, and flow, and is controlled by an engine or aftertreatment control unit to optimize dosing.

SCRSystems are effective at high NOx conversion (often over 80–90%) under appropriate temperatures, and they can operate in conjunction with exhaust gas recirculation (EGR) for further emissions reduction. Cold-start and low-temperature operation can limit performance, and ammonia slip or injector failures are potential maintenance concerns. Regular DEF refilling, leak checks, and catalyst condition monitoring are typical maintenance tasks.

Applications include heavy-duty trucks, buses, construction machinery, industrial generators, and some marine and locomotive engines, all aiming to meet standards such as Euro 6, EPA Tier 4, or equivalent regulations.