Experimental Investigation Of NO Derived From Pyrolysis Reduction Of High Temperature Flue Gas From Semi-coke Organic Ammonia Nitrogen Wastewater

Semi-coke wastewater is an ammonia rich and phenolic wastewater generated duri ng the low-temperature dry distillation production process of semi-coke.The actual trea tment faces problems such as high treatment costs and unstable effluent quality through conventional treatment processes.In response to the above issues,this study conducted a feasibility study on the pyrolysis reduction of NO in high-temperature flue gas from se mi-coke wastewater based on its rich ammonia and organic matter characteristics.We h ave established a flue gas simulation denitrification experimental system for organic am monia nitrogen wastewater from semi-coke,investigated the influence of key factors on the denitrification of semi-coke wastewater and its by-products,investigated the influen ce of main factors on the denitrification of semi-coke wastewater flue gas,explored and proposed the influence of pyrolysis products of semi-coke wastewater on the denitrificat ion of semi-coke wastewater flue gas,proposed methods for improving the quality and e fficiency of semi-coke wastewater,and explored the denitrification and efficiency enhan cement laws of three types of semi-coke wastewater additives,Explored the denitrificati on mechanism of semi-coke wastewater.The main research findings are as follows:（1）Compared with the SNCR denitrification reaction based on urea or ammonia as a reducing agent,the denitrification temperature window of semi-coke wastewater signi ficantly shifts towards the low temperature zone and expands,from 850℃to 1000℃t o 700℃to 900℃,and the temperature window expands by 50℃.The optimized oper ating conditions for denitrification of semi-coke wastewater are temperature 800℃,ox ygen content 4%,gas retention time 6.87 s,and ammonia nitrogen molar ratio of 1;Und er this condition,the highest denitrification efficiency can reach 42.67%.（2）The denitrification process of semi-coke wastewater will produce by-products s uch as NH₃,SO₂,and N₂O.Under optimal operating parameters,the emission concentra tions of ammonia,SO₂,and N₂O can be controlled at 41.36 ppm,11.77 ppm,and 19.57ppm,respectively.By optimizing key control parameters such as NSR and utilizing the synergistic removal effect of existing supporting flue gas purification systems（such as d ust removal and desulfurization）,further deep purification of the above-mentioned by-pr oducts can be achieved.（3）Four low-carbon reducing substances,CO,CH₄,HCN,and C₂H₄,are produced by the pyrolysis of semi-coke wastewater.These low-carbon reducing substances play a certain role in the NO reduction process by generating free radicals and promoting the c onversion of NH₃ to NH₂.（4）Within a certain temperature range,urea and sodium bicarbonate additives have a significant positive effect on the denitrification of semi-coke wastewater,while PAM has a significant negative effect.After adding 1.0 wt.%urea to the semi-coke wastewate r,the peak denitrification efficiency was 90.1%,which was 49.15%and 20.53%higher t han the peak denitrification efficiency of single semi-coke wastewater and single urea,r espectively.At a reaction temperature above 800℃,the addition of sodium bicarbonate has a significant positive effect on the denitrification of semi-coke wastewater,especiall y with a 6.29%increase in denitrification efficiency at 900℃.Within the range of 800℃to 1000℃,the addition of PAM has a significant negative effect on the denitrificati on of semi-coke wastewater,with a maximum reduction in denitrification efficiency of nearly 30%.（5）The effects of urea,sodium bicarbonate,and PAM additives on the byproducts of semi-coke wastewater are different.All three additives have inhibitory effects on SO₂.At the optimal denitrification temperature of 800℃,the SO₂ concentration decreased from 12.02 ppm to 2.69 ppm,0.21 ppm,and 0.13 ppm,with a decrease of 77.62%,98.25%,and 98.92%,respectively.The addition of PAM has a significant inhibitory effect o n the emission concentration of NH₃,decreasing from 37.52 ppm to 12.91 ppm,with a d ecrease of 65.59%.The addition of urea and sodium bicarbonate increases the emission concentration of NH₃.At the optimal denitrification temperature of 800℃,the NH₃ con centration increases from 37.52 ppm to 69.17 ppm and 85.38 ppm,respectively,with sig nificant increases.Attention should be paid to preventing ammonia escape during use.T he addition of urea is beneficial for the generation of N₂O,and the N₂O concentration in creased significantly from 19.57 ppm to 127.03 ppm.The other two additives showed in hibitory effects on N₂O.After the addition of sodium bicarbonate and PAM,the N₂O co ncentration decreased from 19.57 ppm to 5.37 ppm and 4.17 ppm,respectively,with a d ecrease of 72.56%and 78.69%,indicating significant inhibitory effects.（6）The optimal operating parameters for the composite denitration agent formed b y using additives are to use a composite denitration agent of 1 wt.%urea for denitration.The optimal operating conditions include a denitration temperature window of 800℃t o 1000℃,an oxygen content of 4%,a gas residence time of 6.87 seconds,and NSR=1.At this point,the optimal denitrification efficiency is 96.28%.