What is an SCR system? How it reduces NOx on industrial diesel machinery
Selective catalytic reduction (SCR) is an exhaust aftertreatment technology that reduces nitrogen oxides by dosing a urea solution, normally DEF or AdBlue, upstream of a catalyst. Industrial integration depends on exhaust temperature, duty cycle, packaging and control strategy.
How an SCR system works
The dosing module injects a calibrated amount of DEF into the exhaust. Under suitable thermal conditions, ammonia is formed and reacts with NOx across the SCR catalyst, producing mainly nitrogen and water.
Main components
- SCR catalyst.
- DEF/AdBlue tank and supply circuit.
- Dosing module and injector.
- Temperature and, where required, NOx sensors.
- Electronic control and diagnostics.
SCR, DPF and DOC are not interchangeable
SCR targets NOx. A DPF captures particulate matter, while a DOC primarily oxidises CO and hydrocarbons. Demanding applications may require a combined architecture.
Industrial and mining applications
Underground mining equipment, tunnel machinery, rail maintenance vehicles and heavy off-road machines require application-specific thermal and mechanical engineering. NOxBUSTER® combines DPF and SCR for simultaneous NOx and particulate control.
Frequently asked questions
Does SCR remove particulate matter?
Not as its primary function. A diesel particulate filter is normally required when particulate control is also needed.
Can SCR be retrofitted to older machinery?
It may be feasible after assessing exhaust temperature, duty cycle, packaging, control and maintenance requirements.