Denitrification is an important part of flue gas treatment, and SCR denitrification catalyst is a key component of denitrification system. There are 3 common types of catalysts, honeycomb type, plate type and corrugated plate type, among which honeycomb SCR denitrification catalyst is more widely used, not only has good strength, but also easier to clean ash.

Catalysts need to be replaced periodically during use as operating time increases due to dust clogging, sintering, alkali metal poisoning, loss of active components, etc.

The common causes of denitrification catalyst deactivation are physical factors and chemical factors deactivation.
Physical factors: Catalyst activity decreases due to changes in the physical properties of the catalyst itself or physical changes in the catalyst surface structure; there are three main types: sintering, clogging, and abrasion.

Chemical factors: The chemical activity of the active component is destroyed or inhibited after the catalyst absorbs or adsorbs the chemical components in the flue gas, which leads to the reduction of denitrification catalyst activity; mainly including: alkali metal (Na) poisoning, alkaline earth metal (Ca) poisoning, arsenic (As) poisoning, SO3 poisoning, phosphorus (P) poisoning, and the effect of water vapor (H2O).

1、 Sintering
After long-term operation of SCR denitrification catalyst at high temperature, TiO2 will undergo phase transition from anatase to rutile; at the same time, the active component V2O5 will agglomerate to form large particles resulting in reduced dispersion. The specific surface area and activity of the catalyst will be reduced as a result.

Coping strategies
1) Doping the carrier with SiO2, rare earth elements or transition metal elements to inhibit the phase transition of TiO2.
2) Introduce W on the catalyst surface to inhibit the agglomeration of vanadium species.

2、 Clogging
1) Surface coverage - the fly ash in the flue gas covers the surface of the catalyst monomer causing blockage (fly ash deposition).

2) Pore blockage - the internal pores of the catalyst are blocked, resulting in catalyst deactivation (ammonium salt deposition).

Coping strategies
1) Selecting a reasonable catalyst pitch and honeycomb size.
2) Use suitable soot blowers for soot blowing (sonic soot blower, rake soot blower, steam soot blower).
3） Carry out flue gas heating and heat exchange.

3、 Abrasion
The abrasion intensity of the catalyst is related to the airflow speed, fly ash characteristics, impact angle and the characteristics of the catalyst itself.
1) The catalyst is impacted by external forces during installation or replacement.
2) Excessive flue gas flow velocity (> 8 m/s) during operation.
3) Excessive dust concentration (> 45 g/Nm3).

Coping strategies
1) Optimize airflow distribution and install airflow adjustment devices.
2) Hardening of catalyst monomer ends and improving edge hardness.
(3) Installing pre-dusting device to filter fly ash.

The next issue will share the chemical deactivation of denitrification catalyst and the countermeasures for the causes of deactivation.

Anhui Yuanchen Environmental Technology Co., Ltd (hereinafter referred to as "Yuanchen Technology") is a high-tech enterprise integrating R&D, production and sales of dust removal bags and denitrification catalysts. Over the past sixteen years, Yuanchen Technology has been focusing on the environmental protection field, and now has 4 international PCT, 33 authorized invention patents and 77 invention patents in process, among which many products such as "dust removal and denitrification integrated technology products" have been awarded the Scientific Progress Award of Anhui Province. The products of dust bag (mainly PPS, PTFE, P84 and composite series filter neecle felt) and SCR denitrification catalyst have been widely used in cement, steel, glass kilns, waste incineration power generation, biomass power generation, non-ferrous metal smelting and other industries!
 
With 16 years of growth and planning, Yuanchen Technology has been driven by the policy of vigorously developing environmental protection industry, and finally welcomed the rapid development after a big wave. In the future, Yuanchen Technology will be guided by "becoming the guardian of global ecological environment", always rooted in environmental protection and insist on the great cause of guarding the blue sky and white clouds. Leveraging on the national ecological civilization construction pattern, we will continue to deepen technology, optimize management, strengthen brand, refine industry, solidify advantages, and create synergistic value for industry through comprehensive and integrated management and services.