NOx reduction

In addition to combustion optimization Valmet offers several solutions for lower emissions of nitrogen oxides (NOx):

• SNCR - Selective Non-Catalytic Reduction
• SCR - Selective Catalytic Reduction
• Valmet NOx scrubber – a flue gas scrubber for reducing NOx

SNCR – good reduction, low investment

SNCR is a well-known technology for reduction of NOx from power boilers.

Ammonia or urea is injected straight into the furnace or cyclone inlet and mixed with the hot flue gas. Ammonia reacts with nitrogen oxides to produce water and nitrogen. The reduction depends on the design and load of the boiler, but is normally in the range of 20 to 70%.

SNCR offers good reduction efficiency at a relatively low installation cost. The system can be installed in new boilers or retrofitted into existing ones.

Valmet has successful references installed in boilers ranging from 10 to 550 MW.

SCR - high reduction with catalyst

SCR - Selective Catalytic Reduction – is a technology that reduces nitrogen oxides to water and nitrogen using a catalyst. The benefits of SCR include high reduction efficiency – over 90% reduction of NOx - with low operating costs.

During the past 20 years, Valmet has supplied SCR systems to numerous new and retrofit boilers.

Valmet NOx scrubbers

The Valmet NOx scrubber is a new technology that uses an oxidizing agent to reduce emissions of NOx.

Valmet has extensive experience in scrubber technology and the first results indicate major reductions of NOx to air. Read more here about the first installation and the results achieved.

Reducing NOx from recovery boilers is a challenge. Both SCR and SNCR have been tested but a solution that would be both technically and financially viable has not yet been found. But the new Valmet NOx scrubbers may, depending on the situation at the mill, offer new options going forward.