| Selective non-catalytic reduction（SNCR）technology reduces nitrogen oxides（NOx）to N2 and H2O by injecting ammonia reducing agent directly into high-temperature flue gas.It is one of the most important methods to control NOx emissions in waste incineration power plants.However,in industry,SNCR denitration is limited by the temperature window and the mixing effect of reducing agent and flue gas,so that the denitration effect simply cannot meet the increasingly stringent emission standards.Based on that oxygenated additives can broaden the temperature window and bio-oil is composed of various oxygen-containing compounds,the potential of bio-oil to enhance SNCR denitration is experimentally studied on a high-temperature tube furnace.In the atmosphere of waste incineration flue gas,the characteristics and mechanism of bio-oil enhanced SNCR denitration were studied and summarized.Taking the industrial waste grate furnace for example,the modeling analysis of bio-oil’s actual effect and the industrial design were carried out,aiming to explore the technical process of using bio-oil as an industrial SNCR additive,and providing a reference for the application of SNCR technology in waste incineration power plants.In this study,the effects of temperature,bio-oil addition ratio,ammonia-nitrogen equivalent ratio and oxygen concentration on the denitrification characteristics（denitration efficiency,temperature window,optimal denitration efficiency,etc.）and CO emissions of bio-oil-enhanced SNCR were studied.The experimental results showed:adding bio-oil to the urea solution can move the SNCR temperature window to a low range,and at the same time widen the temperature window.When the adding proportion of bio-oil is 5wt%,the optimal denitration temperature window is widened from 210.25℃（944.04℃～1154.29℃）to 262.43℃（881.93℃～1144.36℃）.In the range of 700℃～900℃,whenβ=10wt%,the average denitrification efficiency is increased by 21%.In the SNCR process,CO emissions increase with the increase of the proportion of bio-oil added,but when the temperature is 800℃and the oxygen concentration is above 4%,there is basically no CO emissions.Considering the influence of fly ash in the actual flue gas atmosphere of waste incineration,the effects of fly ash on urea crystal pyrolysis,urea solution oxidation,bio-oil decomposition,and bio-oil enhanced SNCR denitration reaction were studied in turn.The effect of fly ash on urea crystal pyrolysis and bio-oil decomposition is not obvious,but it has a significant promotion effect on the oxidation reaction of urea solution at high temperature.This is mainly due to the catalytic reaction of the active components Ca O and Fe2O3 in the fly ash.At the same time,in the presence of fly ash,the denitration efficiency of SNCR with bio-oil decreased.The urea SNCR experiment with three typical bio-oil molds（acetic acid,phenol,and furfural）was carried out and found that the three molds had the samilar effect on SNCR denitrification,all of which promoted SNCR denitrification below 900℃and reduced the denitration efficiency at high temperatures,but the influence degree was different due to the difference in decomposition characteristics.Based on the comprehensive temperature window and the best denitration efficiency,compared to phenol and furfural,the enhancement effect of acetic acid is better.The promotion of bio-oil can be regarded as the simultaneous action of multiple oxygenated compounds on the SNCR reaction.The core mechanism is that a large amount of OH is generated in the reaction atmosphere,and the reduction of NO by NH3 and HNCO is strengthened in the temperature range below 900℃.Combined with the design and operation parameters of the 500 t/d waste incinerator grate,the modeling analysis and industrial design of the bio-oil enhanced urea SNCR denitration technology were carried out.The analysis results showed that:under BMCR condition,adding 15～20wt%bio-oil to the urea solution can improve the actual SNCR denitration efficiency by about 10～15%.Based on the laboratory experiment conclusions and modeling analysis results,an industrial technology route was designed:before the urea solution is sent to the SNCR spray gun,the bio-oil was evenly mixed in by a certain ratio.Then the mixed solution with bio-oil was added into the furnace where the temperature is below 900°C,by the high-pressure air atomization,to exert the bio-oil enhanced denitrification effect. |
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