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摘要: 在模拟水泥分解炉的实验台架上研究CO2浓度（体积分数0-35%）对污泥再燃还原性气体析出特性及其对污泥与污泥焦还原NO反应的动态变化规律的影响。结果表明，污泥再燃产生的还原性气体主要为HCN、NH3、CH4及CO；当CO2浓度从0增加到25%时，由于CO2与污泥焦气化作用增强，导致HCN、NH3及CH4的析出量缓慢下降，而CO析出量显著增加，最终促进NO还原率从51%增加至61%；继续增加CO2浓度至35%，由于CO2的辐射吸收导致局部热不稳定性增强，气化作用的减弱导致CO析出量下降，且HCN析出量有较大幅度下降，NH3析出量变化不大，CH4析出量有一定幅度上升，综合影响使得NO的还原率逐渐下降至55%。研究表明，实验室条件下污泥再燃能较高效地对烟气中NO进行还原；机理研究表明，污泥再燃过程中同时存在对NO的气气均相还原反应和气固异相还原反应，实验确定污泥焦对NO的气固异相还原率仅为18%，因此，污泥脱硝以气气均相还原反应为主。Abstract: The effect of CO2 content(volume fraction 0-35%) on the reducing gas release characteristics from sewage sludge re-burning and the dynamic properties of NO reduction by sewage sludge and char were investigated in a simulated experimental platform of cement pre-calciner. The experimental results show that the reducing gas release from sewage sludge combustion are mainly HCN, NH3, CH4 and CO. With the increase of CO2 content from 0 to 25%, the release of HCN, NH3 and CH4 slowly decreased due to the enhancing effect of sludge gasification by CO2, while the release of CO increased significantly, eventually promoting the NO reduction rate from 51% to 61%. As continually increasing CO2 content to 35%, the local thermal instability was enhanced due to the radiation absorption of CO2, and the weakening of gasification resulted in the decrease of CO release. Moreover, HCN release decreased significantly, while NH3 release did not change much, CH4 release increased to a certain extent, and the combined effect makes the NO reduction rate gradually decreased to 55%. The results show that sludge re-burning can efficiently reduce NO in flue gas. It is also found that the homogeneous and heterogeneous reduction of NO are concurrence during sludge re-burning, while the experimental studies revealed that the NO reduction rate over the sludge char was only 18%, it implied that sludge denitration is dominated by gas-gas homogeneous reduction.
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Key words:
- CO2 /
- reducing gas /
- sewage sludge /
- char /
- NO reduction
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图 1 高温气固悬浮实验系统示意图
Figure 1 Schematic view of bench scale precalciner
1:quartz tube reactor; 2:electric furnace; 3:thermocouple; 4:electric furnace controller; 5:feeding hopper; 6:holder; 7:flue gas analyzer; 8:computer; 9, 10, 11:cylinder; 12, 13, 14:mass flow controller; 15:mixed gas cylinder; 16:filter
图 2 空气气氛下污泥燃烧的TG-DTG曲线(a)、TG-FTIR曲线(b)、TG-FTIR在波长为4000-2000 cm-1处的放大图(c)及波长为2000-400 cm-1处的放大图(d)
Figure 2 Curves of TG-DTG(a), TG-FTIR(b), magnification of TG-FTIR at wavelength 4000-2000 cm-1 (c) and at wavelength 4000-2000 cm-1(d) by sewage sludge combustion under air atmosphere
图 4 不同CO2体积分数下HCN的析出速率(a)及析出量(b)
Figure 4 Release rate(a) and yield(b) of HCN under different CO2 content
图 5 不同CO2体积分数下CO的析出速率(a)及析出量(b)
Figure 5 Release rate(a) and yield(b) of CO under different CO2 content
图 6 不同CO2体积分数下CH4的析出速率(a)及析出量(b)
Figure 6 Release rate(a) and yield(b) of CH4 under different CO2 content
图 7 不同CO2体积分数下NH3的析出速率(a)及析出量(b)
Figure 7 Release rate(a) and yield(b) of NH3 under different CO2 content
图 8 不同CO2浓度下含N气体析出产率
Figure 8 Nitrogen species release rate under different CO2 content
图 9 不同CO2体积分数下污泥再燃还原NO的动态特性(a)及NO还原阶段的NO还原率(b)
Figure 9 Dynamic properties of NO reduction over sewage sludge reburning
(a) and the NO reduction rate during the NO reduction stage(b) under different CO2 content
图 10 在CO2体积分数为25%时污泥及污泥焦还原NO的动态特性
Figure 10 Dynamic properties of NO reduction by sewage sludge and char under 25% of CO2 volume fraction
图 11 污泥及污泥焦还原NO过程中O2及CO2体积分数变化特性
Figure 11 Concentration variation of O2 and CO2 during NO reduction by sewage sludge and char
表 1 污泥及污泥焦的工业分析和元素分析
Table 1 Proximate analysis and ultimate analysis of sewage sludge and char
Sample Proximate analysis w/% Ultimate analysis w/% Mad Vad Aad FCad C H N S Sewage sludge 6.83 30.56 58.49 4.12 27.06 3.2 3.78 0.83 Char 1.12 1.93 91.16 5.79 4.02 0.34 0.54 0.15 
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表 2 污泥中C、N的存在形态的含量
Table 2 Existing form and content of C and N in sewage sludge
Atomic surface composition /% C N COOH C=O C-O C-C/C-H A-N Pr-N N-5 In-N 11.4 9.1 19.8 59.7 33.65 53.73 1.08 11.54
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