【作者】 林瑜；

【导师】 魏敦崧； 陈德珍；

【作者基本信息】 同济大学 ， 热能工程， 2006， 博士

【摘要】 目前基于中低温段的焚烧烟气净化方式不利于飞灰的后续处理、难以避免过热器的高温腐蚀，并对抑制二噁英的生成不利。为此本研究提出了焚烧烟气高温净化的思路。即在过热器前的高温烟气段用干式净化的方法将大部分酸性气体和飞灰除去，以保护过热器并控制飞灰的毒性，达到提高焚烧炉的安全性和降低整体处理费用的目的。基于这一思路，研究工作主要针对焚烧烟气的高温净化（包括对HCl和NO_x的净化）展开。研究了采用石灰类吸收剂对焚烧烟气中HCl气体进行高温净化的机理，并探索了提高干式净化效率的措施。在实验研究的基础上，对吸收剂喷入烟道后的混合、扩散过程进行了数值模拟，并据此对实验系统的进一步完善提出了改造方案。为了在中高烟温段同时净化NO_x，研究了肼类物质作为还原剂在中、高温段对NO_x的净化效果，并同氨的还原性能进行了比较。最后探索了用肼类物质处理的石灰类吸收剂在过热器前的高温段同时净化HCl气体和NO_x的效果。 为提高HCl气体的干式净化效率，研究了钠碱改性石灰吸收HCl气体的过程。结果表明，与普通石灰相比，改性石灰在高温段具有更好的活性。其原因是改性石灰的晶体规则程度较低；产物层多孔；且其煅烧分解速度能适应反应持续进行的要求。普通石灰在不同温度下的产物成分相同，而改性石灰在各温度下的反应产物成分并不一致。 为确定合适的HCl气体高温净化温度，研究了石灰吸收HCl气体对应的平衡浓度随温度的变化、石灰的热分解规律及温度对反应率的影响。结果表明：石灰吸收HCl气体对应的平衡浓度随温度的升高而升高；烟气中CO₂浓度增大，HCl平衡浓度亦升高，但改性石灰可在一定程度上消除CO₂对HCl吸收的不利影响。石灰在高温下的反应率明显高于低温时的值。即使200℃下已达最大反应率的石灰，在升温到600℃时仍能继续反应，高温提高了反应率。 在水平烟道加旋风除尘器这一连续加料的反应系统上的研究表明，石灰干式净化HCl气体的效率随温度的上升而上升，在650℃时达到峰值后降低。净化效率随HCl初始浓度增加而升高，在HCl浓度为400-1400mg／Nm³时基本呈线性关系；Ca／Cl当量比越高，净化效率越高，但当量比大于4后，效率上升缓慢。综合考虑温度对净化效率和收尘效率的影响，HCl气体的干式净化温度宜设在600℃左右。 实验发现，500℃以上的高温条件下，喷入烟道中的很大一部分石灰会与烟更多还原

【Abstract】 Presently most of incineration flue gas scrubbers are running at moderate to low temperature. This kind of scrubbing mode separates flue gas purification from fly ashes disposal. Thus superheater corrosion cannot be avoided. Meanwhile, the fly ashes and flue gas purification products collected in those scrubbers are toxic because of their dioxin and heavy metal contents. In this work a new scrubbing mode, namely, flue gas dry scrubbing at high temperature was put forward. According to this mode, most of the acidic gas and fly ashes are removed at high temperature before superheater, so that superheater corrosion can be avoided and fly ashes collected under high temperature are less toxic and easy to dispose of. Based on the above idea, this work mainly focused on high temperature scrubbing of gas pollutants （including HCl and NO_x） from incinerators. Firstly, HCl scrubbing with Ca-based absorbents was investigated and measures to improve HCl dry interception efficiency were explored. On the basis of experimental research, numerical simulation on diffusion of absorbent particles sprayed into flue gas scrubber was carried out. The simulation results provided a guide for improving performance of the dry scrubber. Secondly, De-NO_x effect with hydrazine-based compounds as reductants at moderate to high temperatures was examined and the results were compared with having ammonia as reductant. Finally, the possibility of simultaneous HCl and NO scrubbing with Ca-based absorbents treated by hydrazine-based compounds was explored.In order to improve HCl dry interception efficiency, HCl dry scrubbing with modified lime treated by NaOH was studied which proved that at high temperature modified lime’s reactivity is better than normal lime, because of modified lime’s crystal structure being irregular, its product layer being porous and its calcination rate being low to fit reaction process. Modified lime forms different product components at different temperature, which is not the same as normal lime.In order to obtain the optimum temperature for HCl high temperature scrubbing, temperature influence on HCl equilibrium concentration, lime decomposition and lime conversion rates was investigated. The results showed that HCl equilibrium concentration rises when temperature rises or CO₂ partial pressure increases, but modified lime can partially eliminate CO₂’s negative impact on HCl absorption. Lime has higher conversion rate at high temperature than low temperature. Completely reacted lime at 200℃ regains its reactivity when the temperature is raised to 600 ℃.Experiments on a continuous absorbent-feeding scrubbing system which is composed of a horizontal reaction pipe and a Stairmand cyclone indicated that HCl removal efficiency of slaked lime increases with rising temperature until 650°C of its peak temperature. In the range of 400-1400mg/m³, removal efficiency increases with更多还原