废弃物衍生吸附剂合成过程S/Cl/Br定向调控强化脱汞机理研究

The chemical-impregnated sorbent injection is an effective method to reduce mercury emission from coal-derived flue gas. However, the cost of modified-sorbent is relatively high for full-scale commercial application—this limits the popularization of the injection technology particularly in developing countries. Based on this principle, the applicant proposes a novel sorbent synthesis technology, i.e., waste PVC/tire/ brominated flame retardant materials in e-waste plastics were selected as Cl/S/Br precursor and waste biomass as carbon-based materials. A kind of high-efficiency and low-cost mercury sorbent is then obtained through co-pyrolysis of these two materials in municipal solid waste. In order to reveal the regularity of the formation of the surface active groups and the mechanism of mercury adsorption, this application is going to study the following aspects: 1) migration and transformation of S/Cl/Br, and the induction of highly reactive groups for mercury removal during the pyrolysis process；2) effects of activation on physical and chemical properties of modified char; 3) surface/interface reaction between new-born reactive functional groups and mercury, and the competition, synergetic adsorption and selective control mechanism of multi-component contaminant; 4) effects of adsorption/desorption cycle on the surface active groups and its mercury adsorption performance. This research will provide the fundamentals of how to synthesize cost-effective sorbents for mercury removal by using municipal solid waste.

化学改性吸附剂喷射是控制燃煤烟气汞排放的有效手段，但改性吸附剂较高的成本限制了该项技术的发展。基于此，申请人提出以生物质废弃物为碳基材料，以废弃PVC/轮胎/电子产品塑料外壳为活性组分前驱体，采用共热解方法一步制得脱汞吸附剂，从改性活性组分成本、吸附剂基体成本和制造成本三方面降低脱汞吸附剂的成本。本申请围绕热解过程中S/Cl/Br的迁移转化规律及高汞反应活性基团的诱导生成；活化造孔过程对改性焦物理、化学性质的影响规律；焦的表/界面汞脱除机理，多组分污染物竞争、协同吸附及选择性调控机制；多次吸附/脱附循环过程对改性焦表面活性基团及脱汞性能的影响规律等方面开展应用基础研究，揭示新型吸附剂表面活性基团定向调控生成规律及汞吸附机理，为开发以城市固体废弃物中的生物质和含S、Cl、Br塑料混合物制备新型高效、价格低廉的脱汞吸附剂新技术开发与应用奠定基础。

活性炭喷射技术被认为是脱除燃煤烟气中汞最有效的方法，本项目以城市固体废弃物为原料，通过一步共热解法制备了含Cl/Br/S生物焦脱汞吸附剂。.首先探究了PVC强化木竹生物焦脱汞的可行性。共热解过程中引入PVC会造成含Cl生物焦孔道的堵塞，PVC中的Cl以KCl和C-Cl官能团的形式存在于生物焦中；含Cl生物焦最佳制备参数为600 oC和PVC/木竹混合比例为1:3；NO，HCl和SO2可以促进脱汞；C-Cl官能团是主要的吸附位点。.其次探究了溴系阻燃塑料强化木竹生物焦脱汞的可行性。塑料中的Br以Br–和C-Br形式存在于生物焦中，塑料热解残渣会阻塞孔道；含Br生物焦的脱汞性能远高于原始生物焦，最佳制备参数为600 oC和溴系阻燃塑料/木竹混合比例为1:1；O2，NO，HCl和SO2可以促进脱汞；含Br官能团（C-Br）将Hg0氧化为HgBr2。.然后探究了废弃轮胎强化木竹生物焦脱汞的可行性。含S生物焦孔隙结构优良；改性焦中的硫以硫化物，有机硫、元素硫和硫酸盐存在；含S生物焦具有更高的Hg0捕获能力，最佳制备参数为800 oC和废弃轮胎/木竹混合比例为1:1；O2，NO，HCl和SO2对脱汞具有促进作用；有机硫/元素硫可用作Hg0氧化成HgS的活性组分。.紧接着对吸附剂进一步优化，制备了磁性改性吸附剂。铁的催化作用使得生物焦的比表面积和表面官能团含量增加；磁性含Cl生物焦的最佳制备参数为700 oC、Fe(NO3)3溶液浓度为0.05 wt.%。O2，NO，HCl和SO2会促进改性焦对汞的脱除；磁性含Cl生物焦的Fe3O4，C-Cl和C=O提供化学吸附活性位。.最后对改性焦中Hg/Cl/Br的稳定性进行了淋滤测试。Hg在含Br生物焦表面的稳定性优于含Cl生物焦，Hg/Cl/Br在共热解吸附剂表面的稳定性优于化学浸渍吸附剂。