浅谈粉煤灰的资源化利用现状

粉煤灰是电力行业排放的主要固体废弃物,对其的资源化利用已成为环保的首要任务。对粉煤灰进行高附加值的资源化回收利用,是实现可持续发展的必经之路。介绍了大唐国际成功开发研制的从高铝粉煤灰中提取氧化铝技术,开辟了粉煤灰综合利用的新途径。     

Large-scale utilization of desulfurization ash and fly ash for unfired production of high-strength road-base stones

Journal of Material Cycles and Waste Management - This paper utilizes desulfurization ash (DA), fly ash (FA) and ordinary Portland cement (OPC) to prepare unfired high-strength road-base stones by...     

Coal fly ash utilization: low temperature sintering of wall tiles

We present here a study of the sintering of fly ash and its mixture with low alkali pyrophyllite in the presence of sodium hexa meta phosphate (SHMP), a complex activator of sintering, for the purpose of wall tile manufacturing. The sintering of fly ash with SHMP in the temperature range 925-1050 degrees C produces tiles with low impact strength; however, the incremental addition of low alkali pyrophyllite improves impact strength. The impact strength of composites with 40% (w/w) pyrophyllite in the fly ash-pyrophyllite mix satisfies the acceptable limit (19.6J/m) set by the Indian Standards Institute for wall tiles. Increasing the pyrophyllite content results in an increase in the apparent density of tiles, while shrinkage and water absorption decrease. The strength of fly ash tiles is attributed to the formation of a silicophosphate phase; in pyrophyllite rich tiles, it is attributed to the formation of a tridymite-structured T-AlPO(4) phase. Scanning electron micrographs show that the reinforcing rod shaped T-AlPO(4) crystals become more prominent as the pyrophyllite content increases in the sintered tiles.     

粉煤灰-粉煤灰合成沸石对Cs~+的固化

以电厂废弃物粉煤灰为原料、采用碱熔-水热法制备了粉煤灰合成A型沸石(以下简称沸石),再以沸石对溶液中的Cs+进行分离富集,最后在碱激发剂的作用下以粉煤灰和吸附后的沸石制得地聚合物固化体。对固化体的性能进行了评价,并探讨了固化机理。实验结果表明:在吸附温度25℃、初始Cs+质量浓度100 mg/L、固液比10.0 g/L的条件下,沸石对的Cs+的吸附率达98%,比粉煤灰提高了2倍以上;沸石掺量为20%~30%(w)时,固化体的抗压强度符合GB 14569.1—2011要求,固化体中Cs+的42 d浸出率和累计浸出分数均远优于GB 14569.1—2011限值,表现出优异的抗浸出性能。     

曲靖电厂灰渣性质及其用作水泥混合材的试验研究

在对粉煤灰及炉渣的主要物理、化学性质进行分析测试的基础上，对它们用作水泥混合材所表现出的性能及存在的问题进行了分析研究。     

The hydration characteristics and utilization of slag obtained by the vitrification of MSWI fly ash

This study investigated the effects of slag composition on the hydration characteristics of slag blended cement (SBC) pastes. Synthetic slag samples were prepared by melting CaO-modified and Al(2)O(3)-modified municipal solid waste incinerator (MSWI) fly ash. MSWI fly ash was mixed with 5% CaO and 5% Al(2)O(3) (by weight), respectively, resulting in two fly ash mixtures. These mixtures were then melted at 1400 degrees C for 30 min to produce two types of slag with different contents, designated at C-slag and A-slag. Both the C-slag and A-slag samples exhibited a pozzolanic activity index higher than the unmodified slag sample. The results show that the synthetic slags all met the Taiwan EPA's current regulatory thresholds. These synthetic slags were then blended with ordinary Portland cement (OPC) at various weight ratios ranging from 10 to 40%. The 28-day strength of the C1 paste was higher than that developed by the OPC paste, suggesting that the C-slag contributed to the earlier strength of the SBC pastes. At curing times beyond 28 days, the strength of the A1 paste samples approached that of the OPC paste samples. It can be seen from this that increasing the amount of calcium and aluminum oxide increases the early strength of SBC. The C-slag blended cement paste samples showed an increase in the number of fine pores with the curing time, showing that the C-slag enhanced the pozzolanic reactions, filling the pores. Also, the incorporation of a 10% addition of C-slag also tended to enhance the degree of hydration of the SBC pastes during the early ages (3-28 days). However, at later ages, no significant difference in degree of hydration between the OPC pastes and the SBC pastes was observed with the 10% C-slag addition. However, the incorporation of A-slag did decreased the degree of hydration. A slag blend ratio of 40% significantly decreased the hydration degree.     

粉煤灰在废水处理中的应用

就粉煤灰处理废水的研究与应用现状进行了综述.粉煤灰主要通过其吸附作用(物理吸附和化学吸附)处理废水,对于城市污水、工业废水、含重金属离子、F-、PO3-4废水等均有较好的处理效果.对粉煤灰进行物理或化学改性研制高效复合粉煤灰混凝剂是提高粉煤灰利用价值的有效途径之一.同时,提高粉煤灰吸附容量以及妥善处理吸附饱和灰是当前急需解决的问题.     

Diopside-based glass-ceramics from MSW fly ash and bottom ash

By utilising MSW fly ash from the Shanghai Yuqiao municipal solid waste (MSW) incineration plant as the main raw material, diopside-based glass-ceramics were successfully synthesized in the laboratory by combining SiO(2), MgO and Al(2)O(3) or bottom ash as conditioner of the chemical compositions and TiO(2) as the nucleation agent. The optimum procedure for the glass-ceramics is as follows: melting at 1500 degrees C for 30 min, nucleating at 730 degrees C for 90 min, and crystallization at 880 degrees C for 10h. It has been shown that the diopside-based glass-ceramics made from MSW fly ash have a strong fixing capacity for heavy metals such as lead (Pb), chromium (Cr), cadmium (Cd) etc.     

Radon diffusion and exhalation from mortar modified with fly ash: waste utilization and benefits in construction

Journal of Material Cycles and Waste Management - The utilization of fly ash in construction and cement industry increases from last few decades. But the question on utilization of fly ash for...     

Rockwool waste in fly ash geopolymer composites

Journal of Material Cycles and Waste Management - Mineral wool waste is often considered unrecyclable, due to its difficult-to-process physical composition, and potential microbial contamination in...     

Lead immobilization in mechanochemical fly ash recycling

In previous studies, we focused on a mechanochemical process for recycling fly ash for use in cement; this process was expected to immobilize heavy metals in the fly ash, a desirable outcome in light of the fact that recycled fly ash is commonly used in the synthesis of inorganic materials. Here, we investigated the leaching of lead (Pb) from fly ash treated by a mechanochemical process and from cement prepared from the treated fly ash. We used lead oxide (PbO), a typical Pb compound in fly ash, as a model substance. Mechanochemical treatment of the fly ash inhibited Pb leaching by 93%, and further inhibition (more than 99.9%) was observed in cement produced from the treated fly ash. During the mechanochemical treatment, PbO was reduced to Pb by iron from the stainless-steel mill used for processing, and the lower solubility of Pb in water resulted in immobilization of the Pb.     

Remediation of fly ash landfills through plantation

In India, a significant area of land is occupied by preexisting coal‐fired thermal power plants (TPPs) for the storage of fly ash slurry in ash ponds. However, the area available for storage of fly ash at these TPPs is limited. In addition, this type of fly ash disposal poses a problem due to restricted land availability and potential contamination issues. A viable alternative is the reclamation of fly ash ponds by plantation. A study at the Ramagundam Super Thermal Power Station (RSTPS) in Andhra Pradesh, India, on reclamation of a portion of an ash‐filled, low‐lying area has been performed. This article describes the characteristics of the RSTPS pond ash, ash leachates, and improvements in the fertility status of the reclaimed area over a three‐year period. Furthermore, morphometric observations of different planted species indicate that these types of ash‐filled, low‐lying areas can be suitably reclaimed and the nutrient‐rich leachate from ash‐filled areas potentially can be used for irrigation purposes. © 2008 Wiley Periodicals, Inc.     

Comparative study on the characteristics of fly ash and bottom ash geopolymers

This research was conducted to compare geopolymers made from fly ash and ground bottom ash. Sodium hydroxide (NaOH) and sodium silicate (Na(2)SiO(3)) solutions were used as activators. A mass ratio of 1.5 Na(2)SiO(3)/NaOH and three concentrations of NaOH (5, 10, and 15M) were used; the geopolymers were cured at 65 degrees C for 48 h. A Fourier transform infrared spectrometer (FT-IR), differential scanning calorimeter (DSC), and scanning electron microscope (SEM) were used on the geopolymer pastes. Geopolymer mortars were also prepared in order to investigate compressive strength. The results show that both fly ash and bottom ash can be utilized as source materials for the production of geopolymers. The properties of the geopolymers are dependent on source materials and the NaOH concentration. Fly ash is more reactive and produces a higher degree of geopolymerization in comparison with bottom ash. The moderate NaOH concentration of 10 M is found to be suitable and gives fly ash and bottom ash geopolymer mortars with compressive strengths of 35 and 18 MPa.     

粉煤灰干法除炭技术与设备

根据最新收集的文献资料，介绍了国外典型的粉煤灰干法除炭，特别是电选除炭方面的新进展，包括其工作原理、优缺点及工业应用情况。旨在为国内相关企业提供参考。     

Leachate from land disposal of coal fly ash

The results of large-scale lysimeter tests in which two pulverized coal fly ashes (PCFA) have been exposed to natural weather conditions for up to seven years are presented and compared with those of laboratory leaching tests. Laboratory column leaching tests on PCFA show good reproducibility, and comparisons between lysimeter and laboratory leaching results are promising for several salt ions and trace elements in the leachate when expressed in terms of the leachate to solids ratio (L/S). A long-term disposal strategy which takes into account the largely insoluble nature of PCFA is suggested.     

Chitosan composites reinforced with nanostructured waste fly ash

Journal of Material Cycles and Waste Management - This paper outlines the preparation and characterization of chitosan (CS) composites reinforced with mechano-chemically activated fly ash (MCA-FA)....     

Removal techniques for heavy metals from fly ash

This study reviews different technologies for extraction of heavy metals from fly ash. With this perspective processes like bioleaching using microbes, carrier in pulp method, chemical extraction via acids, alkaline leachates and chelating agents, chloride evaporation process, electrodialytic and thermal treatments were studied thoroughly. A comprehensive comparison of all the techniques is also done by studying in detail their reaction conditions, metals leached and percentage extraction achieved. The study concluded that depending on the type of fly ash and metal under consideration determines the suitability of the process adopted for detoxification of fly ash. In addition to these, factors like cost, time and energy also define the final selection process.     

Evaluation of the mechanical properties of class-F fly ash

Coal-burning power plants in the United States (US) generate more than 70 million tons of fly ash as a by-product annually. Recycling large volumes of fly ash in geotechnical applications may offer an attractive alternative to the disposal problem as most of it is currently dumped in ponds or landfills. Class-F fly ash, resulting from burning of bituminous or anthracite coals, is the most common type of fly ash in the US. In the present study, the mechanical characteristics (compaction response, compressibility, and shear strength) of class-F fly ash were investigated by performing various laboratory tests (compaction test, one-dimensional compression test, direct shear test and consolidated-drained triaxial compression test) on fly ash samples collected from three power plants in the state of Indiana (US). Test results have shown that despite some morphological differences, class-F fly ash exhibits mechanical properties that are, in general, comparable to those observed in natural sandy soils.     

Transformation of nitrogen during vermicomposting of fly ash.

In view of environmental problems generated by large-scale production of fly ash, increasing attention is now being paid to the recycling fly ash as a source of plant nutrients in agriculture. However, the low amount of nitrogen in such materials forms a major constraint for such application. In the present study, the possibility of improving the N status in mixtures of fly ash and organic matter was investigated by adopting vermicomposting technology. Different combinations of fly ash and cow (Bos taurus) dung; namely fly ash alone, cow dung alone and fly ash + cow dung at 1:1, 1:3 and 3:1 ratios were incubated with and without epigeic earthworms (Eisenia fetida) for 50 days. The occurrence of N in different bio-available forms; namely easily mineralizable, NH4+ and NO3- tended to increase considerably in the series treated with earthworms. This behaviour was attributed primarily to increased microbiological activity in the vermicomposted samples and also to a considerable rise in the concentration of nitrogen-fixing bacteria in this series. Among the three combinations of vermicomposted fly ash and cow dung, the 1:1 mixture appeared to exhibit the highest availability of nitrogen.