Wanchun low temperature flue gas SCR denitrification system

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Hebei Hanlan Environmental Technology Co., Ltd. has developed a low-temperature denitrification system with wider adaptability on the basis of traditional denitrification technology, combined with its own engineering experience and low-temperature environmental protection catalyst flue gas denitrification technology. The system adopts an advanced flue gas heating system. And flue gas denitrification equipment, in the temperature range of 180--400 ℃, it can achieve a denitrification efficiency of more than 90%, and even at normal temperature, the exhaust gas can also use SCR technology.

The system can be used with ships, pickling waste gas, glass furnaces, industrial boilers, nitric acid, fertilizers, ethylene cracking furnaces, caprolactam, garbage incinerators and chemical waste gas treatment and other equipment with low flue gas temperature, which reduces the pollution of particulate matter and nitrogen oxides to the surrounding environment, and also relieves the enterprise from worries about environmental protection.

1.Reaction principle of low temperature SCR denitrification system

The full name of SCR is Selective Catalytic Reduction, which is the most widely used denitrification technology in the industry. It can be applied to NOx emission control of combustion equipment such as power station boilers, industrial boilers and waste incineration. Ideally, the removal rate of NOx can reach more than 90%. It is the best fixed source NOx treatment technology that can be found at present.

The reaction principle of low-temperature SCR is also to use a reducing agent such as ammonia or urea to reduce NOx (NO, NO2) in the exhaust gas through the action of a catalyst at a certain temperature, and convert NOx into non-polluting element molecular nitrogen (N2), The reaction of NOx with ammonia is as follows:

2NO2+4NH3+O2         3N2+6H2O

NO+NO2+2NH3         2N2+3H2O

2.Low temperature SCR denitrification solution

Our low-temperature SCR denitrification system uses V-Ti-based SCR flue gas denitrification catalyst suitable for lower temperature conditions. The catalyst modified the traditional catalyst by doping X ions, even when the flue gas temperature is only 160 ℃, the denitrification efficiency can be maintained above 90%, and the catalyst can reach more than 90% denitration efficiency in the temperature range of 160--400 ℃.
At present, due to the strong anti-sulfur poisoning ability of anatase TiO2, TiO2 is widely used as a carrier to support other oxides as a catalyst for low-temperature SCR. Donovan A et al. used anatase TiO2 to support V, Cr, Mn, Fe, Co, Ni and Cu metal oxide catalysts, respectively, and conducted a comparative study. The results show that the activities of various supported metal oxides can be simply expressed as: Mn>Cu>Cr>Co>Fe>V>>Ni at 120℃. The Mn/TiO2 catalyst has the highest activity, the selectivity to N2 and the conversion rate of NOx are both 100%, so it is an ideal catalyst.
The MnOx/TiO2 catalyst was prepared by co-precipitation method and its low temperature selective reduction performance was investigated. At 150~250℃, the removal rate of NOx is above 90%. The analysis shows that high loading can improve the NOx removal efficiency of MnOx/TiO2, and the optimal value is n(Mn)/n(Ti)=0.4. In addition, the conversion rate of NOx increases with the increase of O2 concentration. When the volume fraction of O2 is 3%, the removal rate of NOx begins to become a constant value. When the concentration of NH3 is low, the conversion rate of NOx increases with the increase of the concentration of NH3. When the concentration of NH3 is excessive, the removal efficiency remains constant.

3. Selection of low temperature SCR catalysts

According to different structures, SCR denitration catalysts are divided into: honeycomb type, plate type and corrugated type. The honeycomb catalyst selected by our company is the honeycomb catalyst with the highest market share at present. It uses Ti-WV as the main active material, and is fully mixed with TiO2 and other materials. It is extruded and calcined by a die. Therefore, after the surface is damaged and worn by ash, the original catalytic performance can still be maintained, and the catalyst can be regenerated. Features: The catalyst activity per unit volume is high, and the catalyst volume used to achieve the same denitrification efficiency is small, which is suitable for the flue gas environment with ash content below 30 g/m3 and low ash viscosity.

Real picture of low temperature SCR denitrification catalyst product

4.  SCR denitrification System Features

（1） It has a wide range of applications, and can maintain good activity in the treatment temperature zone of 160--400 °C, which solves the technical problem that the catalyst loses activity below 300 °C;
（2）The design is flexible, and the formula, pitch and wall thickness of the catalyst can be adjusted according to the composition of different flue gases, and a reasonable filling unit can be set at the same time;
（3）In the process of low temperature operation, due to the decrease of the total air volume, the amount of catalyst can be reduced and energy can be saved under the condition of constant air velocity;
（4）The design of the urea decomposition device is reasonable and economical, and there is no need to install a urea decomposition furnace, which greatly reduces the equipment cost and operating cost;
（5）Excellent design of flow field simulation, diversion, ammonia homogenization and ash cleaning;
（6）The system adopts automatic control, and the design is simple, and there is no need to use expensive online instruments;
（7）Less equipment, small footprint, easy on-site design. It is not only suitable for the management of new boilers, but also convenient for the management of old boilers, and is basically not limited by site and technology;
（8） SO2 conversion rate is low, NH4HSO4 (ABS) production is low;
（9） The catalyst can be regenerated efficiently, with a life span of 3-5 years, and the replacement frequency is low, which makes the later maintenance and operation cost relatively low;
（10） All raw materials and production equipment can be localized;
（11）The equipment runs stably and the treatment effect is remarkable.