Research on the generation and control of NOx and SO2 during the combustion of pyrolysis gas from waste tires
The stable and clean combustion of pyrolysis gas from waste tires is a key factor for the stable operation of the pyrolysis system.However,due to the complexity of gas composition,controlling pollutants has always been a challenge in the industry.Based on a two-stage experimental system of primary pyrolysis and secondary combustion,the composition of the pyrolysis gas and its purification process were studied in this paper.The results showed that the pyrolysis gas was mainly composed of CH4,H2,and small amounts of other hydrocarbons(C2—C4),with a calorific value of 46.49MJ/m3(standard state).The pyrolysis gas also contained a variety of N-and S-containing compounds,mainly including 96.43mg/m3(standard state)of HCN and 308.44mg/m3(standard state)of H2S.When the pyrolysis gas was directly combusted at 800℃ in an excess air atmosphere,the average emission concentrations of NOx and SO2 were 206.65mg/m3(standard state)and 706.01mg/m3(standard state),respectively,with NOx mainly in the form of fuel NO.Washing the pyrolysis gas with a wash bottle containing 200mL of alkaline solution and organic solvents(such as ethylene glycol,lactic acid,glycerol,and diesel)could effectively control the NOx and SO2.Specifically,using a NaOH solution with a pH=13.7 combined with glycerol for washing the pyrolysis gas shows the best control effect,reducing the average emission concentrations of NOx and SO2 to 27.72mg/m3(standard state)and 48.86mg/m3(standard state)respectively,achieving removal efficiencies of 86.58%and 93.08%.This study could provide an effective method for the large-scale application and promotion of waste tire pyrolysis technology.
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