Cement kiln denitration discharge method

Abstract

The invention discloses a cement kiln denitration discharge method. A preheater system, a kiln tail smoke exhaust pipeline, smoke treatment equipment, a high-temperature fan and a kiln tail dust collector of an existing dry-method cement kiln are utilized. The method comprises adding a catalyst into kiln tail flue gas at an outlet of the preheater system, after the catalyst and the flue gas are mixed, catalyzing the flue gas containing the reducing agent and the nitric oxide to be subjected to a denitration reaction, collecting the catalyst at a kiln tail dust collector, making the catalyst and the raw material pass through a raw material elevator and enter into a preheater system, catalyzing the flue gas containing the reducing agent and the nitric oxide to be subjected to the denitrationreaction, wherein the reducing agent is an ammonia compound or an amine compound, and adding at a reducing agent filling point newly arranged on the preheater or adding by utilizing an existing SNCRsystem. The invention has the characteristics of low investment, low operation cost, no blockage, no poisoning, high reliability and the like.

Description

technical field [0001] The invention relates to the field of air pollution control, in particular to a cement kiln denitrification discharge method. Background technique [0002] Nitrogen oxides can cause photochemical smog, acid rain, ozone depletion and other problems, which have caused serious harm to the ecological environment and have attracted great attention from all countries. At present, the domestic thermal power industry has undergone ultra-low emission transformation, which has greatly reduced nitrogen oxide emissions. Nitrogen oxides in the building materials industry, especially the cement industry, have become the main source of nitrogen oxides pollution. According to statistics, the total amount of nitrogen oxides emitted by cement kilns in 2017 accounted for 20% of the total industrial nitrogen oxides emissions. [0003] At present, the nitrogen oxide control technologies of cement kilns mainly include staged combustion technology, SCR denitrification techn...

AI Technical Summary

Problems solved by technology

Staged combustion technology can reduce a certain amount of nitrogen oxides produced, but cannot achieve ultra-low emissions

The LCO method mainly uses the catalytic oxidation method to desulfurize and denitrify, and realize the conversion of sulfur and nitric acid into chemical fertilizers, but it needs to use oxidants such as ozone, the actual efficiency is poor, and the actual use is relatively small

[0004] SNCR denitrification technology is widely used, but it also has the following disadvantages: first, the denitrification efficiency is 30-60%, and the denitrification efficiency is low, and ultra-low emissions cannot be achieved; second, the temperature of the reaction zone is required to be high, and the temperature range is small (too low Unable to react, too high reducing agent is oxidized); third, it is easy to produce ammonia escape and cause secondary pollution

[0005] At present, the mainstream ultra-low emission denitrification process of cement kiln is SCR denitrification technology. Under the action of catalyst, ammonia water and nitrogen oxide are used to denitrify. The general denitrification efficiency is 80-90%, but there are also the following problems: First, the vanadium-based catalyst used Medium vanadium pollutes the environment and is not easy to use in the future; second, it needs a higher temperature to achieve denitrification, and the general exhaust temperature cannot reach it; third, the dust in the flue gas is easy to cause the honeycomb hole to be blocked; fourth, the flue gas The sulfur in the catalyst is also easy to cause catalyst poisoning; fifth, the honeycomb catalyst also has problems such as strength and wear, and needs to be replaced in 1-2 years, which is expensive

There is also medium and low temperature SCR denitrification technology, but there are also the following problems: first, the low temperature SCR denitrification efficiency is low; second, the sulfur in the flue gas easily forms ammonium sulfate with the reducing agent at low temperature, causing blockage and catalyst deactivation; 3. The overall cost is high, and the honeycomb SCR reactor needs to be replaced and cleaned irregularly, which cannot be used for long-term working conditions

[0006] The application number is CN201911365007.2. The patent application discloses a combined desulfurization and denitrification method for the new dry process cement production line. By adding raw meal modifier to the raw meal elevator, the upper wind between C1 and C3 of the cyclone preheater Liquid desulfurization and denitrification agent is added to the pipe to achieve desulfurization and denitrification. It uses rare earth metals, vanadium, titanium and other transition metal compounds as raw meal modifiers and feeds them into the preheater together with the raw meal. Relatively, the preheater is used as the SCR reaction. However, there are the following problems: First, the catalytic reaction time is short, and the reaction time from the C3 preheater (where the denitrification agent is added) to the C1 preheater (where the catalyst is added) is only 0.5 seconds (the wind speed of the preheater is 18m / s); second, denitrification at high temperature, the use of rare earth and other precious metals as catalysts, the cost is high; third, the use of vanadium compounds as catalysts leads to the presence of toxic metals in cement, which affects the quality of cement; fourth, due to the short reaction time, it needs to be replaced Multiple catalysts, resulting in a large amount of catalysts

In the end, due to problems such as cost and cement quality, etc., it cannot replace the existing high-temperature SCR denitrification technology competition

[0007] At present, for the cement kiln production line, there are few denitrification technologies with good effect, low cost and no secondary pollution

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