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China's Ultra-Low Emission Standards: What They Require and How Plants Meet Them

Part of the Emission Compliance: The Complete Guide — this article is one of the detailed pages in the guide.

Direct answer: China's ultra-low emission (ULE) program requires coal-fired power plants to achieve flue gas concentrations of 35 mg/Nm³ NOx, 35 mg/Nm³ SO₂ and 5 mg/Nm³ (or 10 mg/Nm³ depending on configuration) particulate matter — far below previous standards — with the program extended to steel, cement and other industries. Meeting the NOx number demands multi-layer SCR with careful ammonia control, because the slip constraint tightens alongside the NOx limit.

The ULE numbers

Pollutant Ultra-low emission limit Previous GB 13223 limit
NOx 35 mg/Nm³ 100 mg/Nm³
SO₂ 35 mg/Nm³ 100–200 mg/Nm³
Particulate (PM) 5–10 mg/Nm³ 20–30 mg/Nm³

The program started with power (2014–2020) and has expanded into steel sintering, cement and other sectors, each with sector-specific timetables.

What ULE means for SCR design

  • Higher conversion demand — hitting 35 mg/Nm³ from typical inlet NOx needs 85–95% conversion, which pushes catalyst volume up substantially versus legacy designs.
  • Slip becomes the binding constraint — at high conversion the system runs near the ammonia/NOx stoichiometric ratio; any distribution imperfection converts directly into ammonia slip.
  • Layer strategy is mandatory — plants run two or three catalyst layers with the spare position planned from commissioning.
  • Low-load performance — ULE also regulates low-load operation, forcing plants to address low-temperature SCR or economizer bypass designs.

Extension to non-power industries

Steel sintering, cement kilns and other sectors face sector-specific ULE targets. Their flue gas is dustier, more variable and often cooler, which changes catalyst geometry and positioning decisions — the same NOx number is much harder to hold on a sintering machine than on a boiler.

Practical implications for buyers

  • Verify the applicable standard and timetable for your industry and province.
  • Design against the worst binding expression — concentration at full load and at low load.
  • Budget for monitoring and data availability obligations that come with the permit.
  • Plan catalyst life around the ULE target, not the legacy number.

Manufacturer perspective

ULE changed the market from "install SCR" to "install SCR that holds 35 mg/Nm³ at end-of-life across the load range." We size for the end-of-life guarantee and verify low-load cases explicitly — they are where ULE compliance is won or lost.

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