城市污水污泥与固体垃圾混烧过程中重金属迁移特性的研究

通过城市污水污泥与固体垃圾合成样品在小型管式焚烧炉内的混烧实验,采集灰渣样品进行XRF化学成分分析和浸出毒性鉴别测试,结合污水污泥焚烧过程中热力学平衡计算,定量表征了污水污泥中Cu、Pb、Zn、 Mn、Ni在焚烧过程中向底灰、飞灰和烟气迁移的特性及对灰渣的毒性影响。研究结果表明,污水污泥混烧显著提高了飞灰和底灰中重金属含量,其中Zn和Pb增加量最大,而Ni、Mn、Cu依次减少;随着有机氯的加入,飞灰中重金属含量呈现递增趋势,其中Zn表现最明显。毒性测试结果显示,污水污泥的混烧也导致了垃圾焚烧飞灰中Zn和Pb的浸出浓度超过中国对危险废物浸出的控制标准值。同时,重金属迁移的热力学平衡模型预测结果与实验结果差距较大。这表明热力学平衡计算方法还需进一步考虑影响重金属氯化物形成的其他因素,如在焚烧过程中反应动力学、焚烧室内氧气含量变化、与其他元素间的化学反应等。     

入境废物原料浸出液毒性试验方法探讨

在分析入境危险废物浸出毒性试验方法的基础上,针对入境废物原料浸出液毒性试验方法,按照我国对危险废物浸出毒性试验方法基本要求内容,对确定的14种浸出物质试验方法进行了探讨,并将该法有效运用于对入境可用作原料的工业品废物环控指标普查的工作之中。     

燃煤电厂异相凝并飞灰重金属淋滤特性

采集了燃煤电厂的异相凝并后飞灰,分析了其物理化学特性。并通过淋滤实验研究了飞灰中重金属As、Se、Pb的环境稳定性。结果表明,凝并飞灰的粒径峰值为138.04μm,而粉煤灰为60.26μm;凝并后细颗粒凝聚成了较大的颗粒;凝并飞灰中重金属As、Se、Pb含量均高于同工况下粉煤灰中的含量,且后序脱硫环节所产生石膏中重金属的含量有所下降;批淋滤实验研究结果表明,凝并飞灰中的重金属浸出能力受淋滤液的pH值影响较大,温和环境和碱性条件抑制了As的浸出,酸性和碱性条件抑制了Se的浸出,而碱性条件抑制了Pb的浸出。柱淋滤实验研究结果表明,在酸性溶液和水溶液中,凝并飞灰的重金属浸出能力均受到了抑制。     

燃煤电厂异相凝并飞灰重金属淋滤特性

采集了燃煤电厂的异相凝并后飞灰，分析了其物理化学特性。并通过淋滤实验研究了飞灰中重金属As、Se、Pb的环境稳定性。结果表明，凝并飞灰的粒径峰值为138.04 μm，而粉煤灰为60.26 μm；凝并后细颗粒凝聚成了较大的颗粒；凝并飞灰中重金属As、Se、Pb含量均高于同工况下粉煤灰中的含量，且后序脱硫环节所产生石膏中重金属的含量有所下降；批淋滤实验研究结果表明，凝并飞灰中的重金属浸出能力受淋滤液的pH值影响较大，温和环境和碱性条件抑制了As的浸出，酸性和碱性条件抑制了Se的浸出，而碱性条件抑制了Pb的浸出。柱淋滤实验研究结果表明，在酸性溶液和水溶液中，凝并飞灰的重金属浸出能力均受到了抑制。     

超细粉煤灰吸附亚甲基蓝的机理研究

以西安西郊热电厂粉煤灰(XFA),西安灞桥热电厂粉煤灰(BFA)和陕西渭河电厂粉煤灰(WFA)为原料,球磨后经旋风分级再用布袋收集逸出物分别得到超细粉煤灰XUFA、BUFA和WUFA。研究了超细粉煤灰对亚甲基蓝的吸附动力学、热力学以及pH值对吸附的影响。结果表明,超细粉煤灰对亚甲基蓝的吸附性能明显好于原粉煤灰。超细粉煤灰对亚甲基蓝的吸附性能按顺序为WUFA>XUFA>BUFA。粉煤灰颗粒粒度、比表面积和活性组分(SiO2 Al2O3)含量是影响粉煤灰吸附性能的主要因素。WUFA对亚甲基蓝的吸附符合Langmuir吸附等温式,而XUFA和BUFA对亚甲基蓝的吸附符合Freundlich吸附等温式。超细粉煤灰对亚甲基蓝的吸附均符合二级吸附动力学模型,吸附过程由颗粒内扩散过程控制。当溶液pH由2增加到8时,超细粉煤灰吸附量增加,后随pH值增加,吸附量略有下降。     

超低排放燃煤机组固相产物中Cr和As的赋存形态和浸出特性

针对燃煤电厂超低排放机组,研究了固相产物中的铬和砷两种痕量元素的含量及其赋存和浸出特性。结果表明,超低排放机组飞灰中铬和砷含量均高于底渣。对于飞灰,1#、2#、3#机组铬和砷占比最大的形态分别为可交换态和可氧化态,而4#机组铬和砷占比最大的形态均为残渣态。砷的浸出量低于地下水环境标准(GB 14848—2017)中规定的0.01 mg/L,而2#和3#机组飞灰中铬的浸出量高于排放限值,应予以高度关注。     

低温陶瓷胶凝材料固化脱硫砷渣研究

本文研究了以粉煤灰、矿渣等工业废渣为主要原料配制的低温陶瓷胶凝材料固化脱硫砷渣的影响因素,研究结果表明:脱硫砷渣中的特征砷化合物是以亚砷酸钙的形式存在,经过固化后,转化成了砷、硅、铝共同组成的复杂化合物,固化体中砷渣掺量可达50％以上,抗压强度达到20MPa以上,毒性浸出砷浓度小于0.5mg/L；随着养护时间的延长,强度逐渐提高,砷浸出浓度进一步降低.研究结果说明了低温陶瓷胶凝材料在固化危险废弃物方面具有卓越效能.     

稀土尾矿浸出毒性及Hg,Th,Pb浸出特性研究

稀土尾矿是稀土的生产过程中形成的废弃物,其中很多物质都会在自然条件下如雨水淋溶而浸出,进入到水体中造成环境污染。通过对各稀土尾矿浸出毒性实验,结合到当地的自然条件,考查浸出时间、温度、浸泡液pH值和离子的浓度条件,对尾矿中Hg,Th,Pb浸出含量的影响,讨论了稀土尾矿属于一般的工业固体废物和Hg,Th,Pb的浸出特性。     

平朔矿区粉煤灰中有价锂元素的浸出实验研究

山西平朔矿区煤中发现伴生锂矿,且燃煤过程中元素Li二次富集,使得粉煤灰有可能成为宝贵锂资源的理想替代来源。为了提取富锂粉煤灰中有价元素Li,以平朔某发电厂粉煤灰为研究对象,使用X射线荧光光谱仪(XRF)和电感耦合等离子体质谱仪(ICP-MS)测定粉煤灰中常量和Li元素含量,采用NaCl焙烧—HCl浸出的方法,确定粉煤灰最佳焙烧、酸浸条件,并结合扫描电镜(SEM)对形貌特征进行表征。结果表明,粉煤灰中常量元素Si、Al占主体,有价元素Li较富集;矿物主要为莫来石和刚玉;粉煤灰在950℃、与NaCl助剂1∶2条件下焙烧,加入4mol·L~(-1) HCl在150℃、固液比为1∶20条件下酸浸4h,Li元素浸出效果最佳,可达62.31%。粉煤灰焙烧后形貌蓬松度较大,与焙烧前相比变化明显,有利于Li的高效浸出。     

燃煤烟气非碳基吸附剂脱汞研究进展

燃煤烟气排放的汞严重危害人体健康及生态环境。本研究首先分析了超低排放燃煤电厂烟气汞排放特征,尤其是脱硝、除尘、脱硫设备超低排放改造后烟气汞的形态分布和迁移转化规律;然后总结了近年来用于燃煤烟气净化的非碳基吸附剂的研究进展,归纳了飞灰、矿物吸附剂、贵金属、金属氧化物和金属硫化物的吸附性能,并对影响其吸附性能的常见因素进行了梳理。基于当前研究进展,提出了未来的研究应关注的含汞废吸附剂上汞的稳定性和浸出毒性以及吸附剂的再生和循环利用等问题。     

用工业固体废料合成沸石分子筛的研究进展

系统总结了以工业固体废料为原料合成沸石分子筛材料的最新研究进展, 讨论了以粉煤灰、 珍珠岩工业废料、 煤矸石、 流体催化裂化(FCC)废催化剂、 锂矿渣、 铝土矿渣、 废瓷料和废弃玻璃等工业固体废料为原料, 合成LTA, FAU, MFI, CHA, GIS, SOD, ANA和KFI沸石分子筛材料的工艺方法, 及其在污水中重金属离子的脱除、 空气中CO₂的捕获、 氮氧化物的选择性还原等实际应用中的性能, 并对未来工业固体废料合成沸石分子筛的发展趋势进行了展望.     

Leachability of toxic elements from solid wastes

We have examined the leachability of the toxic elements cadmium, arsenic, mercury, and selenium from solid wastes. The solid wastes studied are municipal incinerator ash, coal fly ash, hospital incinerator ash, raw sewage sludge, sewage incinerator bottom ash, and sewage incinerator lagoon ash (which is a combination of bottom and fly ashes). Cadmium displayed the greatest leachability in all waste types, with 76% leached from the municipal refuse incinerator ash. Although the sources of elements in the wastes are diverse, the leachability and hence the bioavailability in the incinerator ash appears mainly determined by the volatility of the element.     

Calorimetry in testing waste materials from the brown coal combustion

The calorimetric measurements were applied in testing the wastes collected from different furnaces in electric power plants as materials to be used in civil engineering. The fly ash materials were collected from two power stations based on different brown coal deposits and working with conventional and fluidized bed installation. The reactivity of high calcium fly ash from sub-bituminous coal combustion has been proved in calorimetric, conductometric, chemical shrinkage, and rheological measurements before their practical implementation on larger scale. Highly soluble components of fly ash contribute to the hydration products and structure formation, followed by setting and hardening of fly ash–cement mixture. These results have been the base of research project aimed in the innovative solutions dealing with the management of deposits of wastes generated as a result of coal combustion. The standardization and potential use on larger scale of these materials, necessary from the environmental point of view, seems to be the question of nearest future.     

Hot atom effect on the leachability of elements in solid waste

The effect of neutron irradiation on the leachability of elements in solid wastes comprising of coal fly ash, hospital and municipal incinerator ashes was studied. There was a marked increase in leachability in the neutron irradiated wastes compared to non-irradiated wastes especially for elements such as As, Cd, Co, Cr, Sm and Zn. For elements such as Fe and Sm there was no significant difference in the leachabilities in the irradiated and non-irradiated wastes. The possible causes of this scenario and implications are discussed.     

The leachability of elements in solid wastes

Landfills and waste disposal sites are now routinely used for disposal of solid wastes and their incinerator ashes. Trace elements from these ashes are leached by rain and acid rain into nearby waterways providing a pathway for toxic elements to re-enter the food chain and the human life cycle. This paper examines the mechanism and the extent of leaching of 20 elements viz. Ag, Al, As, Ba, Br, Ca, Cd, Co, Cr, Fe, Hg, La, Sb, Sc, Ce, Sm, Ta, V, W and Zn. Instrumental neutron activation analysis (INAA) was used for the assay. The solid wastes studied are municipal refuse incinerator ash, coal fly ash, hospital incinerator ash, raw sewage sludge and its incinerator ash.     

An experimental analysis of coal aluminium mixture in coal fired furnace

Coal is an important fuel used in boiler furnaces. There are problems like unburnt coal and solid wastes like ash contain arsenic, selenium, chromium and cadmium while using it. In order to avoid all such difficulties, aluminium metal powder in various grain sizes mixed with pulverized coal and burned. aluminium metal powder is one of the pyrotechnics having higher calorific value and low ignition temperature. The thermal behavior of aluminium powder along with coal is recorded in DTA. The collected ashes were tested in Scanning Electron Microscope and X-Ray Diffraction meter. The SEM results show that coal ash is having granular and regular structure. All the particles have a size range from 5 to 8 μm. On the other hand, the aluminium coal mixture ash shows a fibrous matrix and the particles are irregular. In XRD graph, the peaks in the graph show orientation of atoms in particular plane and angle. The coal ash has a lot of peaks, but the maximum count value reaches only to 340.97. However the value of counts reaches a maximum of 1,539.06 for aluminium ash. This denotes high atom orientation in a single lattice plane.     

Combined adsorption and oxidation mechanisms of hydrogen sulfide on granulated coal ash

Hydrogen sulfide is highly toxic to benthic organisms and may cause blue tide with depletion of dissolved oxygen in water column due to its oxidation. The purpose of this study is to reveal the combined adsorption and oxidation mechanisms of hydrogen sulfide on granulated coal ash that is a byproduct from coal electric power stations to apply the material as an adsorbent for hydrogen sulfide in natural fields. Sulfur species were identified in both liquid and solid phases to discuss removal mechanisms of the hydrogen sulfide with the granulated coal ash. Batch experiments revealed that hydrogen sulfide decreased significantly by addition of the granulated coal ash and simultaneously the sulfate ion concentration increased. X-ray absorption fine structure analyses showed hydrogen sulfide was adsorbed onto the granulated coal ash and successively oxidized by manganese oxide (III) contained in the material. The oxidation reaction of hydrogen sulfide was coupling with reduction of manganese oxide. On the other hand, iron containing in the granulated coal ash was not involved in hydrogen sulfide oxidation, because the major species of iron in the granulated coal ash was ferrous iron that is not easily reduced by hydrogen sulfide.     

Studies on the pozzolanic and hydraulic properties of fly ashes in model systems

In this work, the pozzolanic and hydraulic properties of ashes originating from various sources were studied in model systems such as ash and ash-lime pastes. The sources of studied ashes were: fluidized combustion of brown coal, pulverized combustion of brown coal and pulverized combustion of hard coal. This article is a continuation of our previously published studies on cement pastes with mentioned ashes. The following experimental techniques were applied: calorimetry, thermal analysis (TG, DTG) and infrared absorption (IR). Previously drawn conclusions relating to the reactivity of ashes in an environment containing Ca²⁺ ions were confirmed. According to these conclusions, an ash originating from fluidized combustion of coal exhibited higher reactivity compared to other ashes from pulverized combustion. Pozzolanic and hydraulic properties of this ash were also confirmed. Differences in the behaviour of ashes originating from pulverized combustion of various types of coal in the presence of water and Ca²⁺ rich environment were demonstrated.     

Coal bioprocessing research at the institute of gas technology

Coal bioprocessing research at the Institute of Gas Technology (IGT) has included solubilization, gasification, desulfurization, denitrogenation, production of specialty chemicals, and the remediation of organic and inorganic wastes associated with coal utilization. Currently, research is focused on desulfurization and remediation. Desulfurization research concerns the development of processes to remove organic sulfur or to convert a portion of pyritic sulfur to sulfuric acid rapidly, thereby serving as a pretreatment to aid the thermochemical conversion of coal to coke and liquid products. The removal of as much as 91% organic sulfur from coal has been achieved, and biodesulfurization of coal has been confirmed by seven analytical techniques performed in six different laboratories. Recent studies have involved the use of molecular genetics to develop strains of bacteria with higher levels of desulfurization activity, and the development of methods for the preparation, storage, and utilization of biodesulfurization catalysts. Remediation studies include the development ofin situ and on-site technologies to treat soil contaminated with coal tar, the leaching of metals from fly ash, and the treatment of waste water resulting from fly ash leaching or from acidic mine drainage (AMD). IGT currently has two projects in EPA’s SITE program concerned with the remediation of coal tar-contaminated soil, and other related technologies are being developed. Efficient laboratory-scale processes for the removal of metals from fly ash and from soil so that the solids pass EPA’s TCLP test, and the subsequent treatment of the leachates or AMD to meet all regulatory requirements have been developed. Data obtained in these projects are presented in particular, and a general discussion of the application of biotechnology to coal is offered.     

Assessment of radioecological situation of a site contaminated by technologically enhanced natural radioactivity in Croatia

The paper deals with radioactivity contamination originating from the coal fired power plant and its waste dumps located in a bay of the Adriatic which is due to geographical characteristics sensitive to any kind of pollution including radioactivity. Investigations of coal used in regular plant operation and of solid incombustible ash and slag showed increased concentrations of natural radioactivity which may cause general environmental contamination of the bay as well as contamination of the marine environment of this part of Croatian Adriatic. There are two coal slag and ash piles, one of them was closed and covered by soil and the other is a still operating pile. The location of both piles presents a considerable environmental problem: situated close to the seaside, slag and ash are accumulating in the littoral zone and, in the case of operating pile, are being filled-up directly into the sea. The aim of this study was to determine the radioactivity level at the ash and slag deposits and to assess the risk of increased radioactivity for the inhabitants of the nearby urban area, for the plant workers and general environment of the bay including the marine environment of this part of the Croatian Adriatic.