According to statistics, the cumulative national cement production in 2019 was 2.33 billion tons, and NOx emissions from the cement industry accounted for about 10% to 12% of the total NOx emissions in the country, which is the third largest source of pollution after thermal power and motor vehicles. As some provinces and cities have introduced ultra-low emission standards one after another, with NOx emission standards from 150mg/m³ to 50mg/m³ covered in each province and city, ultra-low emission transformation has become an inevitable trend.

Selective Catalytic Reduction Technology
Selective catalytic reduction (SCR) technology, with denitrification efficiency of over 90%, is widely used in industrial flue gas NOx treatment and can meet the demand for ultra-low emission in cement industry, with its core being denitrification catalyst.

Cement kiln flue gas characteristics
1、High dust content
Dust concentration in flue gas reaches 80-120 g/Nm3.
2、Sulfur content fluctuates greatly
Due to the difference of fuel and mineral source, the sulfur content of working condition varies greatly, and the concentration of SO2 can reach more than 1000mg/Nm3.
3、High content of heavy metals
The dust contains Cr, Hg, Pb, As, Tl and other heavy metal elements, and the content of some elements is much higher than that of the electric power industry.
4、Small dust particle size and concentrated distribution, high viscosity
The particles smaller than 10μm account for about 75~90%.
5、Complex composition
The dust is rich in alkali/alkaline earth metal oxides, Si, Al, Fe and other elemental compounds, and waste/solid waste blending leads to more complex dust composition.

Difficulties of SCR technology application
1. Catalyst blockage/wear
The dust content of cement kiln tail flue gas is extremely high, up to 80-120g/Nm3, while the small particle size of fly ash leads to high dust stickiness and strong adhesion. It is easy to adsorb on the catalyst surface, forming a reaction isolation layer, resulting in a decrease in activity.
The dust content of cement kiln tail flue gas is very high, and the windward end of the catalyst is easily worn by the high dust flue gas, which makes the catalyst lose its mechanical properties and directly lose its usability.
2、CaSO4 coverage
CaSO4 generated by the reaction of Ca component with SO3/SO2, causing the blockage of catalyst micropores is the main reason of catalyst performance degradation.
Poisoning process: CaO is firstly deposited on the surface, due to the catalytic oxidation of SO2 on the catalyst surface to generate SO3 with relatively high concentration for fast reaction. The volume of generated CaSO4 will expand about 14%, obscuring the active bit of the reaction.
3、Heavy metal/alkali metal poisoning
Cement kiln ash contains a large amount of Ca and a small amount of K, Na and other alkali metals, which can poison the active site on the catalyst surface and deactivate the catalyst.
 Cement kiln ash contains high content of heavy metals (Cr, Pb, Hg, As, Tl), which are easily enriched in the catalyst, obscuring the active activity and blocking the reaction.
4、Soot blowing system
Commonly used acoustic sootblower or steam sootblower (commonly used rake sootblower) ash treatment. Germany ThyssenKrupp benefits from its advanced dust cleaning facilities and generally adopts high temperature and high dust SCR denitrification technology. In order to improve the universality of high dust SCR application in China, there is still room for improvement in dust cleaning and de-dusting technology.

Alkali-resistant SCR denitrification catalyst
Over the years, Yuanchen Technology has always insisted on leading the industrial development by scientific and technological innovation. Starting from the relationship of "quality structure - energy efficiency" of catalysts, combining with the working conditions of cement kiln flue gas, introducing the third metal with multiple acidic sites, increasing the density and number of acidic sites, and developing special functional catalysts --- alkali-resistant SCR denitrification catalyst. The alkali-resistant SCR denitrification catalyst was developed.

Cement denitrification process can be divided into low temperature denitrification and high temperature denitrification. In low-temperature denitrification, SO2 conversion is inhibited by multiple technologies to ensure high activity and stability between 170-380°C. In high-temperature denitrification, high sulfur dust requires high catalyst wear resistance and alkali metal resistance.

The 9-hole alkali-resistant SCR denitrification catalyst of Yuanchen Technology can be used in working conditions with dust content of 100g/Nm3. And special process is adopted for catalyst wear resistance, which essentially improves the strength and wear resistance of catalyst.

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. Our dust removal bags (mainly PPS, PTFE, P84 and composite series filter needle felt) and SCR denitrification catalysts have been widely used in cement, steel, glass kilns, waste incineration power generation, biomass power generation, non-ferrous metal smelting and other industries. 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 and solidify advantages, and create synergistic value for industry through comprehensive and integrated governance and services.