Therefore, during denitration transformation, it is necessary to check whether the motor power of high temperature fan and the body of high temperature fan can meet the requirements.

The amount of flue gas under working conditions is small, and the SCR reactor occupies a small area.

The reactor is set behind the waste heat boiler, which has no impact on the power generation.

When the concentration of dust at the outlet of C1 cyclone preheater is too large to adopt the high-temperature and high-dust process route, this process route can be adopted.

1.1 High temperature, high dust, high temperature and high dust SCR denitration refers to that the cement kiln tail gas directly enters the SCR denitration system from the C1 outlet of the preheater.

At present, SCR denitration catalysts used in cement kilns are mainly vanadium-titanium based catalysts, which are composed of carrier TiO2, auxiliary WO3 and active component V2O5, and other components are added to improve the poisoning resistance and abrasion resistance of the catalysts.

The reaction formula is as follows: NH3+SO3+H2O → NH4HSO4 Therefore, SO2 concentration usually needs to be controlled at a lower level.
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The catalyst commonly used in high-temperature and high-dust process is a 13-hole honeycomb catalyst, which can withstand a maximum dust concentration of 100g/Nm3.

To some extent, the problems of catalyst plugging and wear are alleviated, and the chemical life of catalyst is usually 16000-24000h.

The SCR denitration performance parameters related to the catalyst are emphatically analyzed, and the reasonable values of SCR denitration efficiency, ammonia escape, SO2 conversion rate, catalyst chemical life, and the uniformity of flue gas flow field at the inlet of the reactor are discussed.

At present, the denitration technology in cement industry mainly adopts the combination of staged combustion and SNCR.

According to the difference of flue gas temperature and dust concentration entering SCR reactor, the process route of SCR denitration system of cement kiln tail flue gas is mainly divided into high-temperature high dust, high-temperature medium dust and medium-temperature medium dust.

In the process of high temperature and medium dust, the resistance is increased by about 1100 Pa after the addition of denitration reactor, high temperature electrostatic precipitator and inlet flue, so whether the motor power of high temperature fan and the body of high temperature fan can meet the requirements shall be considered at the same time during denitration transformation.

The active temperature range of high temperature catalyst is 300~400 ℃ (which can be extended to 260~400 ℃ under low sulfur conditions), and the active temperature range of medium and low temperature catalyst is 180~280 ℃.

In recent years, China has paid more and more attention to the emission of nitrogen oxides (NOx) from the cement industry, and the emission standards have become increasingly strict.

However, in this temperature range, SO3 (source: ① residual SO3 in the flue gas; ② SCR catalyst oxidizes SO2 in the flue gas to SO3) reacts with NH3 in the flue gas to form ammonium bisulfate, which can not be decomposed, and will combine with fly ash particles in the flue gas to attach to the surface of the catalyst, causing microporous plugging of the catalyst and poisoning deactivation.

The flue gas temperature here is 280~350 ℃, which is suitable for the reaction temperature of most catalysts, so it is widely used.

Based on the experience of ultra-low emission of flue gas denitration in power, steel and other industries and the flue gas denitration technology in foreign cement industry, some domestic cement production lines, on the basis of the original SNCR denitration, add SCR system as a deep denitration device, which can meet the requirements of ultra-low emission of NOx in the cement industry.

However, the high temperature medium dust increases the dust collector, which covers a large area, has a large system resistance and a slightly higher operating cost.

NOx in the flue gas is mixed with the ammonia injected by the supplementary ammonia injection system, and the reduction reaction occurs through the catalyst to complete the scheduled denitration process.

This can reduce the abrasion and blockage of dust on catalyst.

Main process route SCR denitration process route of cement kiln tail gas, its core is denitration catalyst.

The flue gas after denitration continues to enter the subsequent production process.

Shim Pack

For high temperature and high dust process, the resistance is increased by about 800Pa after adding denitration reactor and inlet and outlet flue.

Due to the different flue gas temperature and dust concentration at the installation location of the denitration reactor, the SCR denitration of the flue gas at the end of the cement kiln is divided into high-temperature and high-dust, high-temperature and medium-temperature and medium-temperature process routes, and the engineering conditions applicable to each process route are obtained through analysis.

The temperature is 180~230 ℃, and the dust is 50~60g/Nm3.

1.

Electrostatic precipitator has high failure rate, high construction difficulty and high investment cost.

The influence of high temperature and high dust process route on the follow-up equipment of cement kiln is introduced.

Due to the high dust concentration in the flue gas at the C1 outlet of the cement kiln, there is a risk of blocking the catalyst, which is easy to accelerate the wear of the catalyst, and a safe and reliable ash cleaning system is required.

Under the condition of excessive ammonia injection, some cement production lines can meet the requirement that the NOx concentration is less than 50mg/Nm3, but the ammonia escape concentration is not guaranteed to be less than 5mg/Nm3, so a deep denitration technology is urgently needed as a supplement to meet the requirements of ultra-low emission standards.

Some local governments have also gradually strengthened the control of atmospheric NOx emission standards, such as Shanxi Province, Henan Province, Jiangsu Province, Tangshan, Xingtai, Handan and other regions in Hebei Province, which have started (or planned) to control the atmospheric NOx emission standards below 50mg/Nm3, while meeting the requirement that the ammonia escape concentration is less than 5mg/Nm3 (the concentration is standard, dry basis, 10% oxygen state, the same below).

If the dust concentration at the outlet of C1 cyclone preheater is more than 100g/Nm3, it is necessary to carry out dust reduction transformation on C1 cyclone preheater or add a dust collector at the inlet of SCR denitration device.

The selection of process shall be based on comprehensive consideration of catalyst application maturity, site layout conditions, dust and SO2 concentration in flue gas, flue gas temperature, etc.

1.3 The medium temperature medium dust denitration reactor is arranged behind the high temperature fan or between the high temperature fan and the kiln tail waste heat boiler.

1.2 High-temperature medium dust High-temperature medium dust denitration technology refers to that after the kiln tail gas passes through the C1 cyclone separator, it first passes through the high-temperature electrostatic precipitator for pretreatment to reduce the dust concentration to below 30g/Nm3, and then enters the SCR denitration reactor for denitration treatment.