Why is it difficult to popularize SCR denitration technology in cement plantDate: 2019-08-21 Views:
Selective catalytic reduction (SCR) is a denitrification method to reduce NOx by injecting ammonia or other suitable reducing agents into the flue gas upstream of the catalyst and converting NOx into nitrogen and water by using the catalyst.
It is known that this technology has been widely used in thermal power industry. At present, 90% production lines in thermal power industry in China adopt SCR technology for denitrification, and this technology has also been successfully applied in glass kiln and other furnaces.However, so far, SCR technology has not been widely used in the cement industry.
In fact, SCR is one of the most widely used denitrification technologies in industry, which is famous for its high efficiency in NOx removal.Ideally, the NOx removal rate can reach more than 80%, and ammonia injected into the flue gas almost completely reacts with NOx, which is the best fixed source NOx treatment technology at present.In the case of the implementation of NOx emission value of 100mg/Nm3 in the power industry, emission requirements can still be well achieved.
However, why is such a high efficiency denitrification technology rarely used in the cement industry?The reason is that the application of SCR technology in cement industry is restricted by the complicated working environment, high investment, high maintenance cost and high resistance.
1. Temperature limit
It is understood that the most commonly used catalyst today is porous Ti2O5 (carrier) to make honeycomb modularization, the surface of the carrier is coated with the active components of catalysis V2O5 and WO3, reaction temperature in 280℃ ~ 400℃ is better.However, in the new dry cement production line, the advanced temperature of the preheater outlet has been reduced to below 300℃, and the actual denitrification effect of SCR installation is affected to some extent.At the same time, in order to implement the national energy saving and consumption reduction policy, China's production line above 2500t/d is generally installed with waste heat boiler, its exhaust temperature reaches 150℃ below, for such smoke, is no longer suitable for installing SCR system.
2. Dust limitation
The dust content in the end of cement furnace is as high as 80 ~ 100mg/Nm3, which is easy to cause pore blockage of catalyst, aggravated wear of catalyst, increased pressure drop of the system, and posed a serious threat to the normal operation of induced draft fan, thus affecting the long-term stable operation of cement furnace production line.
3. Alkaline environment restriction
Sodium, potassium and other water-soluble alkali metal compounds in the flue gas of cement furnace are easy to react with V2O5 in the catalyst, thus poisoning the catalyst and reducing the activity of the catalyst.
4. Exhaust resistance limit
Due to the installation of SCR, the exhaust air resistance will increase by 500 ~ 1000pa, which will increase the burning power consumption by 0.75 ~ 1.5kwh /t for tons of clinker.
5. Cost constraints
The adoption of SCR technology for denitrification requires additional devices, space occupation, large investment and high operating costs.According to the data, the total investment of 5000t/d production line using SCR to reduce NOx is about 40 million yuan.
Affected by the above factors, SCR is rarely used in cement enterprises. However, with the continuous strict environmental protection standards and continuous improvement of technology, SCR can actually be used as an alternative direction.Jiangsu LVSSN more products, about the Raymond mill can consult our online customer service