油页岩热解过程中部分重金属元素的挥发动力学研究

以桦甸油页岩为试样,研究了油页岩在热解过程中重金属元素的挥发规律,并对油页岩中重金属元素的挥发动力学机理进行了分析.结果表明：随着热解温度的升高,重金属挥发率变化情况基本相似,其热解过程迁移曲线均呈现S形状,Weibull函数能够很好地描述重金属元素在油页岩热解过程中的挥发行为;在油页岩热解过程中,重金属元素挥发动力学活化能E处于30~130kJ/mol;各重金属元素迁移的频率因子相对较低,均不高于1×107min-1.活化能E和频率因子A之间呈线性关系;初始热解温度低的元素其挥发活化能也较低.     

污泥热解处理过程中重金属迁移与转化规律综述

归纳总结了各种污泥重金属化学形态分析方法的发展和优缺点、重金属化学形态与生物毒性及生物有效性的关系、污泥重金属评估指数;并重点阐述了对于污泥热解过程中重金属迁徙转化的影响因子,包括污泥自身理化特性、热解终温与加热速率、催化剂、添加剂等对于不同种类重金属的作用规律,为在污泥热解处理中重金属未来的研究趋势方向提供了科学参考。     

城市污泥流化床焚烧炉飞灰中重金属迁移特性

对120 t/d城市污泥循环流化床焚烧炉飞灰中重金属迁移富集特性进行试验研究,对污泥、飞灰及不同温度、取样点的飞灰中Cr、Mn、Ni、Cu、Zn、As、Cd和Pb 8种重金属迁移富集特性进行了分析。试验结果表明:飞灰、底渣及入炉污泥中主要化学成分为Si O_2、Fe_2O_3、Ca O、Al_2O_3和P_2O_5,"Si0_2-Ca O-Al_2O_3-金属氧化物"体系构成了重金属吸附的载体,也为不同形态重金属的吸附提供了活性空间。Cd、As为易挥发性重金属,在炉膛内挥发的Cd、As及其化合物蒸气在503℃和475℃时几乎全部富集于飞灰颗粒;Cr、Mn、Cu、Zn主要通过夹带富集于飞灰颗粒,它们在尾部烟道不同温度区域飞灰颗粒上的富集程度相当,为难挥发性重金属。     

土壤重金属污染现状及其修复技术方法概述

针对土壤重金属污染现状及危害,论述各种土壤重金属修复技术方法的原理和运用,为地方环保部门在进行土壤重金属污染修复决策提供参考。地方环保部门在选择重金属污染土壤修复技术时,应根据受重金属污染土壤的理化性质、污染程度、修复目标、治理经费、治理期限以及技术方法的适用范围等因素进行综合考虑,以选择最佳的技术方法或其组合。在实际工作中,植物修复技术由于具有低耗费、效果显著、无二次污染等特点而建议优先考虑使用。     

废弃印刷线路板共热解影响因素及热解产物表征

热解是资源化利用废弃印刷线路板的重要方法之一。分别以沸石和Fe₃O₄为共热解剂，探讨了共热解剂与废弃线路板的质量比以及热解温度对液相产物产率的影响，并对热解后固、液、气三相产物进行了表征。结果表明，共热解剂的添加不会影响热解油的产率，但可有效降低液相中溴化有机物的含量。热解液相产物组分分析结果表明，直接热解废弃线路板时会有大量溴化有机物释放到液相产物中。加入共热解剂后，苯酚及其同系物成为液相产物的主要成分，溴变成主要以无机溴化物的形式存在。同时，不同共热解剂对废弃线路板的热解影响也不同。Fe₃O₄共热解时，液相产物中小分子苯类物质更多，这可能是由于铁类物质对大分子有机物的分解作用更强。共热解剂在高温下比较稳定，热解后固体主要含有共热解剂、玻璃纤维以及重金属，而热解气的主要成分则为H₂、CH₄和CO₂。     

重金属超积累植物的研究进展

重金属对土壤的污染越来越严重,重金属超积累植物对污染土壤具有很强的修复作用,研究重金属超积累植物越来越受到人们的重视.介绍了重金属超积累植物的研究现状和其在环境修复中的应用,并对当前超积累植物研究的不足之处和需要进一步研究的方向进行了讨论.     

基于生态修复的茶同资源化的综合治理研究与实施

针对茶园土壤中重金属污染引起的茶叶重金属超标，研究了利用种植富集植物收集土壤中的铅等重金属。茶叶修枝后高密承压固化等资源化措施，以及利用太阳能光诱杀虫器物理灭虫降低茶园农药使用的技术。茶园实施综合治理技术后的检测结果表明，茶叶中的铅含量下降幅度明显。     

快速外热式热解工艺对生物质热解产物的影响

焦油一直是生物质热解技术发展的瓶颈。文中研究了快速外热式热解工艺对生物质热解产物的影响。研究表明:快速外热式热解工艺可以有效地避免常规热解过程中出现的原料夹生问题,缩短从加料到开始热解的时间,减少温度上升期间焦油的产生;由于热解温度高,速度快,大分子芳香族化合物发生二次热解,支链断裂生成小分子的烷、氢等物质,提高了热解气的产率和热值;焦油中CmHn等较大分子通过热解和重整的方式变成生物质气,降低了热解产物中焦油含量;热解过程中,由于生物质炭中的芳香族化合物分解成小分子的烷烃、烯烃等进入生物质燃气中,剩余的主要是固定碳,所以生物质炭的产率较低,其它物相与灰烬的相同。     

Cd超富集植物修复污染土壤的研究进展

Cd超富集植物是近年来植物修复技术领域研究的热点,简单介绍了超富集植物的概念及种类,综述了迄今发现的6种Cd超富集植物,探讨了Cd超富集植物对Cd耐受和富集的生理生化机制,并提出了未来Cd超富集植物研究的方向.     

金属矿山污染土壤的重金属迁移特性研究

随着矿产资源开发的逐步推进,金属矿山的开采已经成为环境污染的主要源头,本文结合金属矿山的土壤污染进行分析,通过栽种香根草对土壤中重金属元素的迁移情况的变化特性进行研究,剖析金属矿山土壤污染的详细情况.结果表明,香根草是一种良好的矿区土地污染治理的生态修复植物,为金属矿山的开采以及生态环境保护的平衡提供理论和技术基础.     

水体重金属污染现状及治理技术

工业的发展和进步虽然给人们提供了巨大的物质财富,但是工业废气、废水的排放破坏了正常的生态环境,尤其是重金属的排放对人类的健康造成了严重的威胁。如果工业排放物不经过必要的处理,则很难有效重金属的排放。重金属对水体的毒害作用非常大,并且通过水生植物、水生动物或者饮用水,重金属最终会损害人类的生命健康。因此,对水体的重金属污染进行治理具有非常积极的现实意义。在本文中,笔者着重分析和探讨了水体重金属污染的现状以及相关的治理技术。     

Study on Transition Metal Catalysts for Hydrogen Production from Coal Pyrolysis

<正>In this paper,13 kinds of transition metals are studied as catalysts for the hydrogen production from coal pyrolysis, and relationships between the catalytic activity of a transition metal and its outer electron configuration,d% of transition metals and geometric configuration are summarized.Experimental results show that the same group of transition metals show good similarity for hydrogen production from coal pyrolysis;the d%of transition metals which have activity for hydrogen production from coal pyrolysis is between 40%-50%;all transition metals which have catalytic activity possess either a face-centered cubic or a hexagonal crystal structure.Therefore,it is important to choose a transition metal with an appropriate d%and crystal structure as the catalyst for hydrogen production from coal pyrolysis.     

Beneficial effects of biochar application to contaminated soils on the bioavailability of Cd,Pb and Zn and the biomass production of rapeseed (Brassica napus L.)

Phytoremediation of soils contaminated by heavy metals was tested by liming (CaCO₃) or adding biochar (1%, 5% and 10%, mass fraction) and by growing rapeseed (Brassica napus L.), a common bioenergy crop. Bioavailable metal concentrations (0.01 mol L⁻¹ CaCl₂ extraction) decreased with increasing concentrations of biochar amendment. The reduction reached 71%, 87% and 92% for Cd, Zn and Pb respectively in the presence of 10% biochar. Twelve weeks after sowing, all plants cultivated on the untreated soil and on the soil amended by biochar at 1% had died, while the plants grew normally on the soil that had the other treatments. Compared to liming, treatment with 10% biochar proved equally efficient in reducing metal concentrations in shoots but the biomass production tripled as a result of the soil fertility improvement. Thus, in addition to C sequestration, the incorporation of biochar into metal-contaminated soils could make it possible to cultivate bioenergy crops without encroaching on agricultural lands. Although additional investigations are needed, we suggest that the harvested biomass might in turn be used as feedstock for pyrolysis to produce both bioenergy and new biochar, which could contribute further to the reduction of CO₂ emission.     

Agronomic and environmental effects of land application of residues in short-rotation tree plantations: A literature review

Land application of residues in short-rotation plantation has a priori the double advantage to meet the nutrient needs of these tree plantations at lower cost while recycling residues. Agronomic and environmental effects of a very wide variety of residues on plants and soils have been studied worldwide. I attempt here to compile and to summarize the results of the studies about the effects of land applications of residues (mostly organic) in plantations or under controlled pot conditions of the three species mostly used for short-rotation coppice: willow, poplar, and eucalyptus. The spreading of most residues causes an enrichment of the soil in nutrients and a subsequent increase in the growth of plants. Manure, compost, sewage sludge, and wastewater seem most effective in stimulating growth. Ashes have less impact on growth. Few negative effects on the plant have been highlighted in response to spreading, except in the case of very rich effluents in salt in response to which growth reduction and leaf loss nevertheless did not lead to plant death. The high transpiration potentials of the fast growing species dedicated to intensive tree plantations allow them to absorb and tolerate, without major damages, nutrients in excess, most heavy metals, and antibiotics. In some cases, heavy metal accumulation in soils following the spreading of residues, but few of them showed leaching or water pollution. Nevertheless, the used doses and the intervals between applications were of primary importance to avoid leakage of undesirable elements in the environment.     

Microbial fuel cell (MFC)-based biosensor for combined heavy metals monitoring and associated bioelectrochemical process

To explore the feasibility and related mechanism of MFC biosensor for wastewater detection under the action of combined heavy metals. Cyclic voltammetry (CV) and scanning electrochemical impedance spectroscopy (EIS) were used to explore the related bioelectrochemical process. The response of the reactor to single/combined heavy metals, low/high heavy metal concentrations, and the differences in ohmic resistance (Rs) and charge transfer resistance (Rct) were investigated using Ni as the core heavy metal and the combined action of Cd, Cu and Zn. The results indicated that there was a linear relationship between the concentration and output voltage of the MFC biosensor under the action of combined heavy metals (R² = 0.8803–0.973). However, the internal resistance (Rint) of the MFC biosensor under the action of single heavy metal was far less than that of the combined heavy metal group, and the power density (19.849 W m^?3) was 4 times that of the combined heavy metal group (3.109–4.589 W m^?3). The Rs of the biosensors in the combined heavy metal group were 0.868Ω and 0.860, which were higher than 0.768Ω of the single heavy metal sensor. With the increase of the concentration of heavy metals in the influent, the increase of Rct was more obvious in the combined group, while the Rs in the single group significantly increased (P < 0.05). The results imply that it is possible for MFC biosensors to be used in the detection of actual water polluted by various heavy metals, but the biosensor performance is mainly limited by Rct, which needs to be further improved.     

Waste pyrolysis and generation of storable char

Sustainable cities require the generation of energy from waste that cannot be economically reused or recycled. This study focuses on slow pyrolysis that can generate a high yield of char along with liquid and gas products from waste. Char is high in energy content, storable and transportable with low cost so that it can be used as an intermediate medium for high efficiency energy conversion. Pre‐processed municipal waste pellets, wood and grass were pyrolysed in a batch type reactor for a final temperature ranging from 350 to 700°C, and the char products were characterized. The mass yields of char ranged from 55 to 20% for the tested temperature range, recovering 70–30% of energy and 62–30% of carbon in the raw material. The gross calorific value of char was 30–35 MJ kg^?1 on a dry ash free basis. The ash content of raw materials was a key parameter for the quality of char, since its proportion increased by 2–4 times in char depending on the mass yield. A significant amount of volatile metals such as Hg, As and Pb in the waste sample was evaporated at 500°C. Therefore, evaporation of volatile metals was another important parameter in determining the pyrolysis temperature and fuel residence time. The char did not show significant morphological change in the tested range of temperatures. It was concluded that slow pyrolysis of waste for char production should be performed below 500°C in order to increase the energy yield and also to reduce the evaporation of heavy metals. Copyright © 2006 John Wiley & Sons, Ltd.     

分级燃烧对固体吸附剂吸附痕量金属的影响

在一维煤粉燃烧炉实验研究了分级燃烧方式对吸附剂控制重金属元素排放的影响。试验发现分级燃烧会增加亚微米颗粒中重金属的浓度,不利于对痕量重金属元素的控制,尤其对挥发性大的元素(如Cu和Ni)影响越明显;固体吸附剂对煤中重金属的排放具有吸附作用,并且吸附剂对不同的重金属元素的吸附有选择性;最后对吸附剂吸附重金属元素的机理做了阐述,吸附剂吸附重金属元素是通过物理吸附和化学吸附,其中它们在吸附过程中是共存的。     

危险废物焚烧飞灰熔融处理过程重金属行为的研究

对危险废物焚烧飞灰的成分进行了分析,测定了典型重金属成分的含量和浸出毒性。在自行设计的小型电热式熔融炉上进行飞灰的熔融实验,着重对熔融过程中重金属的固化机理及熔渣的浸出特性进行了分析。结果表明,添加CaO能普遍提高重金属的固定率,而添加SiO2后易挥发重金属的固定率提高明显。同时,惰性气氛能显著改善重金属的固化效果。经过1400℃高温处理后的熔渣不具有浸出毒性,具备安全填埋的条件。     

Particle-metal interactions during combustion of pulp and paper biomass in a fluidized bed combustor

We compare interactions between metals and solid particles during the classic fluidized bed combustion (FBC) and a new low-high-low temperature (LHL) combustion of selected biomass. The biomass was a mixture of bark and pine wood residues typically used by a paper mill as a source of energy. Experiments, conducted on a pilot scale, reveal a clear pattern of surface predominance of light metals (Ca, Na, K) and core predominance of heavy metals (Cd, Cr) within the LHL-generated particles. No such behavior was induced by the FBC. Metal migration is linked to the evolution of inorganic particles. A composite picture of the metal rearrangements in the particles was obtained by a combination of independent analytical techniques including electron probe microanalysis, field emission scanning electron microscopy, inductively coupled plasma spectrometry, and X-ray diffractometry. It is suggested that the combination of (1) the high-temperature region in the LHL and (2) changes in the surface free energy of the particles is the driving force for the metal-particle behavior. Important practical implications of the observed phenomena are proposed, including removal of hazardous submicron particulate and reduction in fouling/slagging during biomass combustion. These findings may contribute to redesigning of currently operating FBC units to generate nonhazardous, nonleachable, reusable particles where heavy metals are immobilized while environmental and technological problems reduced.     

Impact of heavy metals in Indian fly ashes on its application as soil ameliorant

Coal contains various organic and inorganic substances including trace quantities of the heavy metals. Therefore, the combustion of coals releases some of the ultimately to the environment of some heavy metals elements in the form of their oxides and in a redistribution of these heavy metals in the surface soil and water bodies, particularly in the vicinity of coal-fired power plants. The fly ash and pond ash of different thermal power stations of India were mixed with soil at different doses separately to compare their impact on crop produce and soil. The present study deals with the presence of the heavy metals in the coal ash and its movement through the amendment of coal ash to the soil and crop produce.