洁净煤技术

2020, v.26;No.125(01) 151-163

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碳材料对燃煤烟气硫脱除及资源化研究进展
Research progress of carbon materials on sulfur removal and resource utilization from coal-fired flue gas

曲智斌;孙飞;皮信信;郄志鹏;高继慧;
QU Zhibin;SUN Fei;PI Xinxin;QIE Zhipeng;GAO Jihui;School of Energy Science and Engineering,Harbin Institute of Technology;

摘要(Abstract):

中国发电煤耗每年近20亿t,虽然传统湿法脱硫工艺能够实现燃煤污染物SO_2的有效控制,但由于存在水耗高、副产劣质石膏量大难用等缺点,面临可持续发展困境。相比之下,基于多孔碳材料的SO_2脱除技术由于具备水耗少、无二次污染、污染物可资源化回收、吸附剂可再生利用等优点,是重要的发展方向。笔者综述了目前基于碳材料吸附、催化过程的燃煤烟气硫脱除及资源化研究进展,论述了碳材料资源化脱硫工艺的关键技术环节,最后提出了燃煤烟气硫脱除及资源化的未来科学和技术方向。碳材料内SO_2吸附-催化反应机制及产物迁移路径,重点讨论了碳材料孔结构、官能团、金属氧化物负载对SO_2吸附转化及副产物迁移的影响。研究表明,碳材料分级孔结构内存在SO_2吸附转化以及产物硫酸的迁移过程;在碳材料中掺杂以氮和氧为代表的非碳元素能改变碳平面的电子结构,调控SO_2在碳材料中的吸附和催化氧化过程。因此,碳材料孔隙与功能性官能团的协同定向构筑是强化碳材料吸附转化SO_2、提升脱硫性能的有效方式。脱硫饱和碳材料再生及硫资源化回收技术路径,重点讨论了碳热还原方法将SO_2资源化转化为硫磺的影响因素。热再生能耗高、活性焦质量损失严重;水洗再生效率低,活性焦循环脱硫能力差,高效再生需要活性焦不同尺度孔隙结构的有效配组,以强化物质输运扩散;在各种脱硫副产物中,硫磺物质量小、价值高、便利储运,是理想的资源化回收目标;碳基还原剂活性与选择性的调控是实现高效硫磺生成的关键。论述了高性能煤基活性焦的低成本宏量制备方法,重点讨论了强化脱硫过程的分级孔活性焦低成本制备方法。传统柱状活性焦制备工艺复杂、成本高且孔隙结构呈微孔分布,存在内扩散阻力大、内表面利用率低、SO_2脱除及再生脱附性能差等问题。破碎或颗粒状活性焦有望降低活性焦制备成本且实现活性焦孔隙的深度调控,但结构稳定性(强度)的提升是关键。通过催化活化、配煤、催化石墨化方法,可望实现兼具高活性和高结构稳定性的脱硫活性焦制备。
The coal consumption of power generation in China is nearly 2 billion tons annually. Although SO_2 emissions have been controlled at ultra-low emission level by the wet limestone-gypsum flue gas desulfurization( WFGD) technology,the problems of large consumption of H_2O as well as the difficulty in disposing the low-value by-product CaSO_4 make traditional WFGD technology face the sustainable development dilemma. By contrast,SO_2 removal based on carbon materials is regarded as one of alternative technologies to WFGD due to the advantages of low H_2O consumption,less water consumption,recycling of pollutants,eco-friendliness as well as high-value utilization of by-product. Herein,the research progress of sulfur removal and resource utilization based on the adsorption and catalysis of carbon materials was reviewed. The key technical links in the process of desulfuration by using carbon materials were discussed. Finally,the directions for future research for sulfur removal and resource utilization were proposed. The mechanism of SO_2 adsorption catalytic reaction and the product migration path in carbon materials were discussed. The effects of pore structure,functional group and metal oxide loading on the adsorption and conversion of SO_2 as well as by-product migration were discussed. The results show that the adsorption and conversion of SO_2 as well as by-product migration can occur in hierarchical pore; Doping non-carbon elements such as nitrogen and oxygen can change the electronic structure of carbon surface and further adjust the processes of adsorption as well as catalytic oxidation of SO_2 in carbon materials. Therefore,oriented construction of hierarchical pore structures and functional groups is an efficient method to strengthen the adsorption and transformation of SO_2 and improve the desulfurization performance of carbon materials. The regeneration of saturated carbon materials and the pathways of sulfur resource utilization were analyzed. Particularly,the factors that may influence the conversion of SO_2 to sulfur by carbothermal reduction were discussed. Thermal regeneration faces the problems of high energy consumption and serious loss of quality. Washing regeneration has the problems of low efficiency and poor cycling desulfurization capacity. Efficient regeneration requires effective matching of pore structures of different sizes to enhance the diffusion and transportation processes. Among all kinds of desulfurization by-products,sulfur owns the advantages of low quality,high value,convenient storage and transportation,which is an ideal goal of resource recovery. The regulation of the activity and selectivity of carbon-based reductant is the key to achieve efficient sulfur generation. Low-cost preparation methods of high-performance coal-based activated coke was analyzed. The method that could prepare activated coke with hierarchical pore structures was particularly discussed. The preparation of traditional columnar activated coke has complicated preparation process and high cost and microporous distribution of pore structure. The prepared columnar activated coke only owns micropores,leading to the problems of large internal diffusion resistance,low internal surface utilization,and poor SO_2 removal and regeneration performance. The preparation of broken or granular activated coke is able to reduce the cost of preparation of activated coke and achieve deep regulation of the pores of activated coke,but the improvement of structural stability( strength) is the key for its application. Through catalytic activation,coal blending and catalytic graphitization,the desulfurized active coke with both high activity and high structural stability is expected to be prepared.

关键词(KeyWords): SO2脱除;硫资源化;碳材料;孔结构;官能团
SO2 removal;sulfur resource utilization;carbon material;pore structure;functional group

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基金项目(Foundation): 国家重点研发计划资助项目(2017YFB0602901)

作者(Author): 曲智斌;孙飞;皮信信;郄志鹏;高继慧;
QU Zhibin;SUN Fei;PI Xinxin;QIE Zhipeng;GAO Jihui;School of Energy Science and Engineering,Harbin Institute of Technology;

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