Control of mercury vapor emissions from combustion flue gas

GOAL, SCOPE AND BACKGROUND: Mercury (Hg) emission from combustion flue gas is a significant environmental concern due to its toxicity and high volatility. A number of the research efforts have been carried out in the past decade exploiting mercury emission, monitoring and control from combustion flue gases. Most recently, increasing activities are focused on evaluating the behavior of mercury in coal combustion systems and developing novel Hg control technologies. This is partly due to the new regulatory requirement on mercury emissions from coal-fired combustors to be enacted under the U.S. Title III of the 1990 Clean Air Act Amendments. The aim of this review work is to better understand the state-of-the-art technologies of flue gas mercury control and identify the gaps of knowledge hence areas for further opportunities in research and development. MAIN FEATURES: This paper examines mercury behaviors in combustion systems through a comprehensive review of the available literature. About 70 published papers and reports were cited and studied. RESULTS AND DISCUSSION: This paper summarizes the mechanisms of formation of mercury containing compounds during combustion, its speciation and reaction in flue gas, as well as subsequent mobilization in the environment. It also provides a review of the current techniques designed for real-time, continuous emission monitoring (CEM) for mercury. Most importantly, current flue gas mercury control technologies are reviewed while activated carbon adsorption, a technology that offers the greatest potential for the control of gas-phase mercury emissions, is highlighted. CONCLUSIONS AND RECOMMENDATIONS: Although much progress has been achieved in the last decade, techniques developed for the monitoring and control of mercury from combustion flue gases are not yet mature and gaps in knowledge exist for further advancement. More R&D efforts are required for the effective control of Hg emissions and the main focuses are identified.     

Development and prospects of municipal solid waste (MSW) incineration in China

With the lack of space for new landfills, municipal solid waste (MSW) incineration is playing an increasingly important role in municipal solid waste management in China. The literatures on certain aspects of incineration plants in China are reviewed in this paper, including the development and status of the application of MSW incineration technologies, the treatment of leachate from stored MSW, air pollution control technologies, and the status of the fly-ash control method. Energy policy and its promotion of MSW-to-energy conversion are also elucidated.     

氯化剂对超细颗粒物与重金属共生成特性的影响

以循环流化床反应器为实验平台,研究了焚烧温度为850℃下添加剂（NH₄Cl和KCl）对超细颗粒物与重金属共生成特性的影响.结果表明：NH₄Cl和KCl的存在均会降低超细颗粒物的数量浓度,但KCl的效果更佳,发挥的是阶梯式或者协同式作用.此外,添加比例为3%时对超细颗粒物数量浓度的降低最为明显.重金属Cr,Mn,Ni主要通过夹带方式形成超细颗粒物;而重金属Pb,Cu,Zn则主要通过蒸发、冷凝和吸附方式累积在超细颗粒物中.无机氯在焚烧过程中可以作为颗粒之间良好的粘合剂,促进超细颗粒物之间的成长和团聚,同时促进其表面形态的生长.此外,K的存在会促进细模态颗粒物之间的凝聚成长,使得细模态颗粒物的峰值增大,而NH₄⁺的存在会降低粗模态颗粒物的峰值.本研究可为污泥等废物热处理过程中重金属与超细颗粒物的协同控制提供借鉴.     

稻壳灰中温热处理稳固化垃圾飞灰重金属

利用稻壳灰与某垃圾电厂产生的飞灰为原料,对飞灰和稻壳灰与飞灰的混合物进行中温热处理,探究热处理工艺参数对稻壳灰稳固化垃圾飞灰重金属的影响.在一定温度范围内,反应主要产物为CSSF（即Ca₁₀（SiO₄）₃（SO₄）₃F₂）、Ca₃SiO₅等硅酸盐结晶相,这些物质会包覆重金属,同时,飞灰重金属Pb、Zn、Cu、Cd中相对不稳定的酸溶态和可还原态向更稳定的可氧化态或残渣态转变,使Pb、Zn、Cu、Cd的浸出浓度显著降低;热处理时间延长,稻壳灰添加量增加,会使热处理样中硅酸盐种类增多,结晶度提高,导致重金属的浸出浓度逐渐降低;稻壳灰添加量在2%~4%范围内,经中温热处理样品的重金属浸出浓度较低,添加量过高时（超过6%时）,重金属浸出浓度逐渐升高.     

Influence of combustion-originated dioxins in atmospheric deposition on water quality of an urban river in Japan

Bulk (wet and dry) deposition samples were collected in Saitama Prefecture, Japan throughout a year (February 8, 2012 to February 7, 2013) to estimate the influence of dioxins emitting from waste incinerators on river water quality. The annual deposition flux of dioxins was 3.3 ng-toxic equivalent (TEQ)/m²/year. Source identification using indicative congeners estimated that 82% of dioxin TEQ in the bulk deposition (2.7 ng-TEQ/m²/year) was combustion-originated, indicating that most of the dioxins in the deposition were derived from waste incinerators. In Saitama prefecture the annual flux of combustion-originated dioxins in depositions was apparently consistent with that of dioxin emission into the air from waste incinerators. The TEQ of combustion-originated dioxins in the deposition per rainfall was 2.4 pg-TEQ/L on annual average, exceeding the environmental quality standard (EQS) for water in Japan of 1 pg-TEQ/L. This suggests there is a possibility that dioxins in atmospheric deposition have a significant influence on the water quality of urban rivers which rainwater directly flows into because of many paved areas in the basins. The influence of combustion-originated dioxin in the deposition on the water quality of Ayase River, an urban river heavily polluted with dioxins, was estimated at 0.29 pg-TEQ/L on annual average in 2015. It seems that dioxins in atmospheric deposition from waste incinerators have a significant influence on water quality of some urban rivers via rainwater though the dioxins in the ambient air have achieved the EQS for atmosphere at all monitoring sites in Japan.     

我国城市生活垃圾处理处置全过程大气排放研究进展

2016年我国城市生活垃圾的年清运量突破2×108 t,并且在未来一段时间内仍会呈现上升趋势.虽然近年来我国城市垃圾无害化处理率年均增幅超过10%,但随着城市化进程的不断深入,庞大的垃圾产生量给现有城市垃圾处理系统造成巨大挑战,同时使垃圾处理处置过程中大气温室气体及污染物排放逐渐引起社会关注,如2010年我国垃圾焚烧导致大气污染物NO_x、SO₂、CO、颗粒物的排放量分别为28、12 062、6 500、4 654 t等.充分调研现有垃圾处理处置全过程大气排放的研究,总结我国城市生活垃圾收集、转运到最终处理处置大气排放物种多样、排放分散的现状,结合现有研究覆盖范围有限、研究物种稀少的局限,同时为进一步推进大气排放清单系统化和精细化的进程,提出以下建议和展望:①核算城市和地区垃圾转运过程中的大气环境成本和压缩空间;②进一步完善并扩充垃圾焚烧多种有毒有害大气污染物（如二英、重金属元素及挥发性有机物等）排放特征测试和排放清单的研究;③在完善生活垃圾填埋场温室气体排放时空分布特征的同时,健全生活垃圾填埋场颗粒物及挥发性有机物等典型大气污染物排放清单相关研究.      

染料工业废水零排放的可行性研究

染料废水是目前难治理的工业废水之一.通过对某染料厂还原蓝生产废水的研究,提出了利用残余硫酸制取硫酸亚铁水处理剂,滤渣在一般锅炉内焚烧的综合利用和治理工艺.从而探索和实践了少污染,回收利用等综合治理污染的工艺,力求尝试一种“零排放”和“绿色化学”的化工生产过程.     

深度脱水污泥焚烧过程中调理剂的热转化行为及其对重金属挥发的影响

采用化学热力学平衡分析方法,应用污泥实测数据模拟计算了深度脱水后污泥焚烧过程中调理剂的热转化过程及逸出产物,并预测了含Cl调理剂与CaO耦合作用对重金属迁移转化及排放的影响.研究结果表明,污泥添加单一调理剂Al_2(SO_4)_3、Fe_2(SO_4)_3、FeSO_4、AlCl_3及FeCl_3后,Fe和Al在高温下主要以Al_2O_3(s)和Fe_2O_3(s)存在,主要气态产物是HCl和SO_2.调理剂CaO和FeCl_3共存且含量增加时,焚烧过程中HCl(g)逸出过程变慢,并且Fe_2O_3(s)易于和CaO(s)作用导致Fe_2O_3(s)存在温度区间变窄.污泥未添加调理剂焚烧过程中,重金属Cd、Pb、Cr、Tl、Hg、As易于以Cd(OH)_2(g)、PbO(g)、CrO_2(OH)_2(g)、AsO(g)、Hg(g)、Tl(g)形式挥发,而Cu、Zn、Ni以其氧化物形式存在而难挥发.调理剂FeCl_3及CaO添加到污泥后,重金属(Cd、Pb、Cu、Zn、Ni、Hg、Tl)的分布受FeCl3的影响大于CaO,导致其形成重金属氯化物而挥发,而Cr和As与CaO作用生成CaCr_2O_4(s)、Ca_3(AsO_4)_2(s)热稳定化学物,抑制了Cr、As的挥发.当脱水污泥与含硫化物掺烧时,重金属(Pb、Cu、Zn、Ni)挥发受到Cl的影响大于S,在低温区间其主要以硫酸盐为主,在中高温区间以氯化物存在,而Hg和Tl不受硫化物影响.     

Characteristics, treatment and utilization of residues from municipal waste incineration

Beneficial utilization of residues from municipal solid waste incineration is an important objective for integrated waste management in many jurisdictions. When residues are to be used as an aggregate substitute in construction applications, the release of constituents of concern to soils and water through leaching is an important environmental consideration. In this paper, residue characteristics that control constituent leaching and testing approaches for evaluating leaching are discussed. Quality control and potential improvement in case of beneficial application are addressed.     

浦东机场垃圾焚烧处理设计

系统地介绍了浦东国际机场航空垃圾焚烧处理工艺 ,对航空垃圾焚烧处理的设计条件、系统流程和物料平衡等主要工艺参数及过程安全控制进行了详细的阐述。