煤炭清洁高效利用是推动我国能源结构低碳绿色转型的重要途径。重金属作为燃煤主要污染物之一，对人类及生态环境危害巨大，目前美国已开始执行燃煤电厂重金属排放标准，主要通过选煤技术降低重金属源头生成以实现达标排放。我国煤炭用量大、部分煤种重金属含量高、地区差异大，亟需开发符合我国国情的重金属控制技术。以挥发性强、毒性高的3种典型重金属砷、硒、铅为对象，总结了国内外燃煤电厂重金属排放现状及控制技术进展。我国煤电污染物超低排放技术路线对重金属具有一定的协同控制效果，其中硒较多以气态形式存在，集中在湿法烟气脱硫系统内洗涤脱除，砷、铅主要附着于颗粒物上，除尘器对其具有协同捕集效果，但仍存在痕量气态硒传质驱动力差、细颗粒态砷、铅易穿透等瓶颈问题，严重制约了重金属的稳定高效捕集。“转化与固定”是重金属控制的总体思路，即通过化学组分调控与物理流场优化等方式，促进烟气重金属由细颗粒态、气态向粗颗粒态，由高毒性向低毒性转变，以实现重金属的无害化处理。基于该思路，目前已形成了一系列燃煤电厂重金属全流程控制技术，根据作用阶段可分为炉前、炉中、炉后3类,主要包括选煤、煤种调配、炉内吸附剂、凝并、脱硫塔内构件优化等技术。此外，燃煤副产物（脱硫石膏与废水）中重金属的稳定化问题需额外关注，可通过浆液原位固化或先进废水处理技术，降低副产物中重金属的环境释放风险，以上部分技术已通过中试或实际机组试验验证，具备较好的推广应用前景。为进一步发展燃煤重金属控制技术，提高我国重金属污染治理水平，对重金属控制技术发展进行展望：应开发实际燃煤中痕量重金属在线连续检测技术，实现重金属浓度实时获取；剖析多机制耦合作用下重金属转化行为与动力学特性，明晰复杂烟气条件下重金属详细迁移机制；建立燃煤重金属控制技术的评估体系，根据电厂特征、目标重金属、技术成熟度、经济性、环境风险等，提供具有针对性的重金属

控制方案。

The clean and efficient utilization of coal is an important way to promote the low-carbon and green transformation of the energy structure of China. As one of the main pollutants duning coal combustion, heavy metals are harmful to human beings and the ecological environment. At present, the United States has begun to implement heavy metal emission standards for coal-fired power plants, and the emission compliance is realized mainly by coal washing to reduce the heavy metal inputs. The coal consumption amount of China is huge, with the high heavy metal content in some types of coal, and regional differences are large. It is urgent to develop heavy metal control technologies which meet China′s national conditions. Three typical heavy metals (arsenic, selenium and lead), which were highly volatile and highly toxic, were selected to summarize the current emission status and control technologies of heavy metal in coal-fired power plants at home and abroad. The ultra-low emission technology route of China has a synergistic control effect on heavy metals. Among them, selenium mostly exists in the gaseous form, and is mainly washed out in the wet flue gas desulfurization system. Arsenic and lead are mainly attached to the particulate matter, and the dust collector has synergistic capture effects for them. However there are still some bottlenecks such as poor mass transfer driving force for trace gaseous selenium and penetration of fine-particulate arsenic and lead, making it difficult to achieve stable and efficient capture of heavy metals. "Transformation and fixation" is the general idea of heavy metal control, that is, by chemical composition regulation and physical flow field optimization, to promote the transformation of heavy metals in flue gas from fine-particulate and gaseous form to coarse-particulate form, and from high toxicity form to low toxicity form, so as to realize the harmless treatment of heavy metals. Based on this idea, a series of whole-process control technologies for heavy metals in coal-fired power plants have been formed, which can be divided into three categories: pre-furnace, in-furnace, and post-furnace according to the action stage. The specific technologies include coal washing, coal blending, in-furnace adsorbents, agglomeration, internal component optimization, etc. The stabilization of heavy metals in coal-fired by-products (such as desulfurization gypsum and wastewater) requires additional attention. The release risk of heavy metals in by-products can be reduced by in-situ solidification of slurry or advanced wastewater treatment technologies. Some of the above heavy metal control technologies have been verified through pilot tests or the full-scaled unit experiments, which have a good application prospect. In order to further develop the coal-fired heavy metal control technologies and improve the level of heavy metal pollution governance, some prospects about the development of heavy metals control technologies were put forward: developing the online continuous detection technology of trace heavy metals in the actual coal-fired flue gas to realize the real-time acquisition of heavy metal concentrations in flue gas, analyzing the transformation behavior and kinetic characteristics of heavy metals under the multiple mechanisms, to clarify the detailed migration mechanism of heavy metals under complex flue gas conditions, establishing an evaluation system for coal-fired heavy metal control technologies, and providing targeted heavy metal solutions according to power plant characteristics, target, technology maturity, economy, environmental risks, etc.

0 引言

1 燃煤电厂重金属排放现状及标准

2 重金属控制技术进展

   2.1 炉前重金属控制技术

   2.2 炉内重金属控制技术

   2.3 炉后重金属控制

   2.4 副产物中重金属控制

3 结语与展望