TiO2 is one of the most commonly used carriers for denitrification catalysts due to its well-developed pore structure and huge specific surface area. iO2 has more abundant acid sites than Al2O3, which can better adsorb the alkaline reductant NH3 and improve the rate of SCR reaction; the sulphate on the iO2 surface is more stable compared to other carriers. Therefore, TiO2-loaded MnOx denitrification catalysts showed good anti-SO2 performance in SCR denitrification reaction, and its application in low-temperature NH3-SCR denitrification reaction was the most widespread. 1) Pana et al [20] prepared a 20% (mass fraction, same below) loaded MnOx/TiO2 denitrification catalyst by impregnation method, and the catalytic performance evaluation showed that the denitrification rate could reach 100% at 120°C at 8000 h-1 air speed. The activity evaluation results showed that the Mn metal on the TiO2 carrier was highly dispersed when the Mn content was less than 16.7%, and the activity of the denitrification catalyst varied with the Mn loading, and the Mn/TiO2 denitrification catalyst showed the highest catalytic activity at 175°C with the Mn loading of 16.7%, and the NO conversion was 94%. MnOx/TiO2 denitrification catalysts were prepared by Jiang et al [22] using impregnation, sol-gel and co-precipitation methods, and the MnOx/TiO2 denitrification catalysts prepared by sol-gel method showed the highest catalytic activity and better SO2 resistance at low temperature, and the denitrification rate reached 90% at 145 °C; Zhang et al [23] used ultrasonic impregnation to prepare MnO2/TiO2 denitrification catalysts, which had higher SCR catalytic activity compared with the conventional impregnation and sol-gel-suspect methods, especially in the low temperature range below 120 °C. The higher catalytic activity of the denitrification catalysts could be attributed to the strong synergistic interaction between Mn and Ti, the large specific surface area, the high concentration of hydroxyl groups, the high amorphous Mn content, the large number of Lewis acid sites, etc. 2) As with unloaded Mn denitration catalysts, the addition of transition metals can improve the active metal dispersion of MnOx/TiO2 denitration catalysts, form solid solutions with MnOx and TiO2, increase the catalytic activity and acid resistance of denitration catalysts by specific surface area, and reduce the catalytic reaction temperature window. The addition of oxide to MnOx/TiO2 denitration catalyst can improve the catalytic activity and N2 selectivity of low-temperature SCR reaction and enhance its resistance to H2O and SO2; Wu et al [25-26] found that the addition of Ce can significantly improve the denitration catalyst activity, effectively improve the resistance to SO2 and inhibit the formation of sulfate on the surface of denitration catalyst; Jin Ruiben [27] carried out the Mn/TiO2 denitration catalyst on the The doping of metallic elements on the Mn/TiO2 denitration catalyst showed that the ...

Continuing our introduction to the various carrier series SCR denitrification catalysts, today we introduce the 4MnOx/molecular sieve denitrification catalyst Molecular sieves are an important material for excellent denitrification catalyst carriers due to their unique pore structure and abundance of acidic site centres, and have also received attention in SCR denitrification technology, but most of these denitrification catalysts exhibit high catalytic activity in the medium to high temperature region, and in contrast, less research has been reported on molecular sieve-based denitrification catalysts with high SCR activity at low temperatures. Sabeti et al [37] used a special precipitation method to load an amorphous layer of MnOx on the surface of NaY zeolite microcrystals to obtain an eggshell-type MnOx/NaY denitrification catalyst, which achieved 80%-100% NO conversion at 200 °C under 5%-10% inlet gas moisture content. Qi et al [38] obtained bimetallic denitrification catalysts by first loading MnOx onto USY molecular sieves and then impregnating Ce or Fe, with NO conversions of 43% and 50% at 80 °C, respectively, and on 14%Ce-6%Mn/USY denitrification catalysts, with NO Liang et al [39] produced a V-OMS-2 denitrification catalyst by introducing vanadium ion (V5+) into MnOx octahedral molecular sieve (OMS-2) using a hydrothermal synthesis method. The highest catalytic activity was achieved at 2% V. 2.5 MnOx/other carrier denitrification catalysts Zhou et al [40] prepared a multilayer composite denitrification catalyst alternately loaded with Mn-Ce-O/TiO2 and Cu-Ce-O/TiO2 using a sol-gel method with coccolithophore honeycomb ceramics as the carrier. The NO conversion efficiency on the denitrification catalyst reached 95% at 250 °C; the NO conversion efficiency was higher than 80% at 200~300 °C. Huang et al [41] prepared Mn-Fe/MPS denitrification catalysts using MPS (mesoporous silicon oxide) as the carrier. The Mn-Fe/MPS denitrification catalysts showed the highest catalytic activity (NO conversion up to 99.1% at 160 °C) when n(Mn)/n(Fe) = 1. When the temperature was higher than 140 °C, H2O had no negative effect on the denitrification catalyst activity; the SCR catalytic activity gradually decreased in the presence of SO2 and H2O. Shen et al [42] prepared three titanium-based column clay (Ti-PILCs) carriers from TiC14, TiOSO4, and Ti(OC3H7)4, respectively, followed by the impregnation method to prepare Mn CeOx/Ti-PILCs denitrification catalysts were then prepared by impregnation. The Mn-CeOx/Ti-PILCs denitrification catalysts prepared from TiOSO4 had the highest catalytic activity for SCR reaction (up to 98% NO conversion at 220 °C) and showed good resistance to H2O and SO2; the Mn-CeOx/Ti-PILCs denitrification catalysts prepared from TiCl4 had the lowest activity. It can be expected that future research work on SCR denitrification catalysts will mainly focus on widening their low temperature active temperature window, improving their H2O and ...

In recent decades, researchers have developed a variety of low-temperature denitrification catalysts, including transition metal oxide denitrification catalysts, precious metal denitrification catalysts and ion-exchange molecular sieve denitrification catalysts. Among them, transition metal denitrification catalysts, such as those containing V, Mn, Fe, Co, Ni, Cr, Cu, W, Zr, La and other active components, have shown high catalytic activity for low-temperature SCR reactions. Due to the special valence electron configuration of Mn element (3d54s2), the valence state of Mn element is widely varied, including +2, +3, +4, +5 and some non-integer equivalents, which can achieve mutual conversion between different valence states of Mn to produce redox, which can promote the reduction of NO and thus the SCR reaction [5], and MnOx has a variety of surface active oxygen This leads to a large increase in the low-temperature catalytic activity of this denitrification catalyst [6-7]. For these reasons, MnOx-based denitrification catalysts have become a research hotspot for low-temperature SCR denitrification catalysts at home and abroad. MnOx denitrification catalysts are mainly divided into two categories: non-carrier type and carrier type denitrification catalysts. This paper introduces the current research status of low-temperature MnOx-based SCR denitrification catalysts and provides an outlook on the next step of research. Carrier-based manganese (MnOx) denitrification catalysts Another effective way to improve the specific surface area and dispersion of denitrification catalysts and enhance their performance against H2O and SO2 is to load the active components onto a carrier with a large specific surface area. Since the catalytic activity and selectivity of loaded manganese denitrification catalysts are higher than those of non-negative manganese denitrification catalysts, the study of loaded manganese denitrification catalysts has become a hot topic of interest. At present, the main carriers used for the preparation of manganese denitrification catalysts are TiO2, Al2O3, carbon based materials, molecular sieves, ceramics, etc. Low temperature SCR denitrification catalysts have many advantages such as low activity temperature and long service life, making them the main development direction for denitrification catalysts. At present, some progress has been made in the research of low temperature manganese based SCR denitrification catalysts, but there are many problems to be solved in the process of industrial application of these denitrification catalysts.

Prospects for SCR denitrification catalysts: With the current level of pollutant emissions, NOx emissions will reach 30 million t by 2020. the current rapid growth of NOx emissions in China has exacerbated the deterioration of regional acid rain, even partially offsetting the huge efforts made in SO2 control in China [4]. Statistics show that the growth of NOx emissions in China has led to a shift in acid rain pollution from sulphuric acid to a combination of sulphuric and nitric acid, with the proportion of nitrate ions in acid rain rising gradually from 10% in the 1980s to 30% in recent years. NOx is also an important cause of regional fine particle pollution and haze, and due to the significant increase in NOx emissions in recent years, atmospheric visibility in China is decreasing and hazy weather is increasing. Therefore, NOx emission control has become an important task for air pollution control. 2MnOx/Al2O3 denitrification catalyst As an amphoteric oxide with high thermal stability, Al2O3 is also an excellent low-temperature SCR carrier because it has abundant acidic sites and can better adsorb the reactants NO and NH3, which is conducive to the catalytic reaction. Wen Qingbo [29] prepared a denitrification and denitrification catalyst Fe0.05Mn0.09Ce0.05Ox/γ-Al2O3 with the complex oxides formed by three transition metal elements Fe and MnCe as the active components and γ-Al2O3 as the carrier, which has excellent denitrification performance at low temperature, good anti-SO2 performance and long service life. conversion up to 89% and over 98% when the temperature exceeded 170°C, and had good SO2 resistance and long service life. Guo Jing et al[30] used sol-gel method to produce CeO2-MnOx/Al2O3 composite denitrification catalyst, which had the highest catalytic activity at 250°C and denitrification rate of more than 95%. Jin et al[31] loaded Mn and Ce on TiO2 and Al2O3 carriers and evaluated the activity of the two denitrification catalysts. The results showed that the Mn-Ce/TiO2 denitration catalysts were more active from 80 to 150 °C, while the Mn-Ce/Al2O3 denitration catalysts had better catalytic activity above 150 °C.

Prospect of SCR denitrification catalyst: nitrogen oxides (NOx) are one of the main pollutants in the atmosphere, which are a great danger to human health and ecological environment.NOx comes from the flue gas produced by fuel combustion, and mainly exists in the form of N2O, NO, N2O3, NO2, N2O4, N2O5, etc. [1], of which NO is the main one, accounting for more than 90% of the total NOx, followed by In the atmosphere, NO is oxidized to NO2, and NO2 reacts with CHx in the smoke under the condition of ultraviolet radiation to produce a kind of photochemical smog, which is 4-5 times more toxic than NO and is extremely harmful to most human organs, animals and plants. In 2003, China emitted more than 16 million tons of NOx, and in 2012, it reached 21.94 million tons, making it the world's top NOx emitter. Therefore, NOx emission control has become an important task for air pollution control. The current denitrification technology for industrial application is mainly selective catalytic reduction (SCR) denitrification technology with NH3 as the reducing agent. At present, the commercialized denitrification catalyst is V2O5+WO3(MoO3)/TiO2(anatase) as the active component, the active temperature window of the denitrification catalyst is 300~400℃, which is vulnerable to the influence of SO2 and ash in the flue gas and reduces the life of the denitrification catalyst in the high temperature area, so the high efficiency and low temperature SCR denitrification catalyst has become a hot research topic in recent years. has become a hot research topic in recent years. Non-carrier manganese (MnOx)-based denitrification catalysts 1) Non-loaded manganese denitrification catalysts consist of only the active component - MnOx or composite denitrification catalysts with MnOx as the main active component with other metal oxides. For the single active component MnOx denitration catalysts, Kapteijn et al [8-9] did a more detailed study on the single component MnOx for the polyvalent and multivalent of Mn, prepared pure MnOx in different valence states and evaluated the catalytic activity of Mn denitration catalysts with different valence states for NH3-SCR reaction. The results showed that MnO2 had the highest catalytic activity and MnO had the lowest catalytic activity; the reaction on Mn2O3 denitration catalyst had the highest N2 selectivity, and the catalytic activity and selectivity of non-carrier type denitration catalysts were closely related to the oxidation state and the degree of crystallization of denitration catalysts.Tang et al [10] studied three different types of carrier-free MnOx denitration catalysts, and the results showed that the denitration The key factors for the high low-temperature activity of the catalysts were the amorphous crystalline state of MnOx and the large specific surface area. The main preparation method of unloaded MnOx denitrification catalysts is co-precipitation (which can obtain a high specific surface area), therefore, the choice o...

In all kinds of extreme conditions, the dust removal system is an extremely important part of the dust filter bag, and the filter bag directly determines the dust removal efficiency of the dust removal system, and due to the different working conditions, the material of the dust filter bag used is not the same, but because in the use of the process will be subject to the wear and tear of the flue gas dust, so there is often the phenomenon of dust filter bag breakage, and the reasons for the breakage of the dust collector with the The reasons for breakage are also related to the design, manufacture, installation and operation of the dust collector, but the corresponding solutions are different for different locations of wear and tear. 1. Lower part of dust filter bag wear:  lower part wear is generally divided into outer wear and inner wear, lower outer wear more filter bag bottom up within 300mm, the lower serious, up gradually reduce. Then it is possible that the local sewing line of the cloth bag dust collector will be worn off, and the position without being worn sewing line strong good. This kind of wear is mostly caused by deformation of cell plate, too small hole spacing, deformation of bag cage, too long filter bag and other reasons. Individuals have filter bags and bag filter box wall abrasion broken. Solution: Check the level of flower plate, and use well-made bag cage. 2. Dust filter bag mouth wear: dust filter bag mouth wear occurs mostly in the bag mouth down 350mm or less, there is more damage from the inside to the outside present. The reason for this situation is the work of the back-blowing dust cleaning system, compressed air deviated from the center of the filter bag, directly washing the side wall of the filter bag caused. When the filter bag in the side of the deviation of the compressed air constantly flushed, first the inner side of the filter bag coating is blown off by compressed air, followed by the base cloth is blown leak, and then the filter surface will be blown leak to form a hole. Then it will lead to dusty flue gas quickly from the broken hole to enter, flush the broken diagonal, the formation of new broken cavities and new dusty flue gas entrance, the increasing number of cavities assemble finally caused the bag mouth ring broken, and in serious cases even lead to bag head and bag body separation. Solution: adjust the compressed air pressure, blowing short pipe skew, deformation of the flower plate, and then replace the new filter bag. 3. Dust filter bag lower inside wear, this situation generally occurs in contact with the bag dust collector bag cage position, most of the bag cage and bag cage bottom diameter difference is too large, resulting in bag cleaning and filtration when the change amplitude is too large, with the bag cage abrasion caused by breakage. Solution: Replace the bag cage with a high quality bag filter. 4. Dust filter bag bottom wear: divided into outer wear and inner wear, if the bottom of...