Optimization Of NO_x Ultra-low Emission And Ammonia Escape From Cement Kiln Mixed With Burning Sludge

The large amount of NO_xemission and ammonia escape from cement kilns have always been major environmental protection problems for enterprises.It is a new way to solve this problem to install SNCR denitrification system in cement calciners and burn municipal sludge.At the same time,the wet desulfurization system has a strong ability to remove ammonia escaping from the kiln flue gas,which can effectively reduce the NH₃emission concentration at the chimney outlet.The research results of this paper provide an effective way for the treatment of ammonia escaping from the flue gas of cement industry.At present,various provinces and cities guide the development of air pollutant emission standards of cement industry to ultra-low emission standards through policies.In order to make the NO_xemission concentration meet the emission standards,cement plants usually inject a large amount of ammonia,that is,increasing the ammonia nitrogen molar ratio（NSR）to improve the efficiency in actual operation,and the ammonia escape amount increases gradually.Aiming at the problem of ultra-low NO_xemission in cement industry and ammonia escape under ultra-low emission standard,the following researches are carried out:（1）taking the flue gas treatment system of a large cement production line in Guangdong Province as the research object,the optimization experiment of ultra-low NO_xemission and ammonia escape based on municipal sludge combustion is carried out The change law of NO_xemission and ammonia escape from cement kiln was found.（2）The method of using wet desulfurization system to remove runaway ammonia from flue gas of kiln tail is put forward,so as to achieve the emission standard of ammonia from flue gas of cement industry.By establishing the material balance equation of ammonia absorption in the desulfurization tower,it can be seen that the ammonia removal efficiency is mainly affected by the liquid gas ratio,the p H value of desulfurization slurry and the ammonia nitrogen concentration in the slurry.Experiments were carried out in the wet desulfurization system at the end of cement kiln to study the effects of liquid gas ratio,p H value of desulfurization slurry and ammonia nitrogen concentration in slurry on the removal efficiency of gaseous NH₃.（3）A method of using waste heat of clinker in grate cooler to evaporate desulfurization wastewater from cement kiln to achieve zero emission was proposed.The effects of atomization evaporation of desulfurization wastewater in grate cooler on flue gas temperature,NO_xconcentration,ammonia escape rate and flue gas dust concentration were studied.The main conclusions are as follows:（1）After optimizing the ammonia injection method of the denitrification system and admixing municipal sludge,the NO_xemission concentration and the escape ammonia concentration of the kiln tail gas have been significantly reduced;compared with before and after optimization,the NOx emission concentration is less than 100 According to the ammonia water consumption underthe condition of sludge blending ratio of 0.024 and NSR of1.6,the NOx emissionconcentration is reduced from 120mg/m³to 89mg/m³,and the escaped ammonia concentration is reduced from 38mg/m³to 21mg/m³.（2）In the stage where the denitrification efficiency is 50%-70%,in terms of reducing the amount of ammonia escape,the operation mode of increasing the sludge blending ratio is better than the operation mode of increasing the NSR;（3）The scrubbing effect of the slurry in the wet desulfurization system can effectively remove the escaped ammonia from the cement kiln denitration system.Increasing the liquid-to-gas ratio,reducing the p H value of the slurry,and reducing the slurry ammonia nitrogen concentration are beneficial to improve the ammonia removal efficiency.（4）The evaporation of desulfurization wastewater at the grate cooler can achieve zero discharge of desulfurization wastewater and reduce the NO_xemission concentration of the kiln tail gas;the evaporation of desulfurization wastewater in the grate cooler helps reduce the amount of ammonia injected by the SNCR system,thereby reducing the ammonia escape rate;with the increase of desulfurization wastewater injection amount,NO_xemission concentration gradually decreases,and NO_xconcentration reaches the lowest value when the wastewater injection amount is 5.5 m³/h.（5）The evaporation of desulfurization wastewater in the high-temperature section of the grate cooler is helpful to solve the ammonia escape problem in the chimney.Injecting the desulfurization wastewater at the high-temperature section of the grate cooler can reduce the concentration of ammonia nitrogen in the slurry pool of the desulfurization tower,so that the ammonia escape concentration of the chimney is reduced by 3.86 mg/m³is reduced to1.25mg/m³.The research results of this paper can provide technical reference for ultra-low NO_xemission and ammonia escape of cement kiln burning municipal sludge.