Nickel speciation of residual oil fly ash and ambient particulate matter using X-ray absorption spectroscopy

The chemical speciation of Ni in fly ash produced from approximately 0.85 wt % S residual (no. 6 fuel) oils in laboratory (7 kW)- and utility (400 MW)-scale combustion systems was investigated using X-ray absorption fine structure (XAFS) spectroscopy, X-ray diffraction (XRD), and acetate extraction [1 M NaOAc-0.5 M HOAc (pH 5) at 25 degrees C]-anodic stripping voltammetry (ASV). XAFS was also used to determine the Ni speciation of ambient particulate matter (PM) sampled near the 400-MW system. Based on XAFS analyses of bulk fly ash and their corresponding acetate extraction residue, it is estimated that > 99% of the total Ni (0.38 wt %) in the experimentally produced fly ash occurs as NiSO4.xH2O, whereas > 95% of the total Ni (1.70 and 2.25 wt %) in two fly ash samples from the 400-MW system occurs as NiSO4.xH2O and Ni-bearing spinel, possibly NiFe2O4. Spinel was also detected using XRD. Acetate extracts most of the NiSO4.xH2O and concentrates insoluble NiFe2O4 in extraction residue. Similar to fly ash, ambient PM contains NiSO4.xH2O and NiFe2O4; however, the proportion of NiSO4.xH2O relative to NiFe2O4 is much greater in the PM. Results from this and previous investigations indicate that residual oil ash produced in the 7-kW combustion system lack insoluble Ni (e.g., NiFe2O4) but are enriched in soluble NiSO4.xH2O relative to fly ash from utility-scale systems. This difference in Ni speciation is most likely related to the lack of additive [e.g., Mg(OH)2] injection and residence time in the 7-kW combustion system.     

Nickel Speciation of Residual Oil Fly Ash and Ambient Particulate Matter Using X-ray Absorption Spectroscopy

ABSTRACT

The chemical speciation of Ni in fly ash produced from ~0.85 wt % S residual (no. 6 fuel) oils in laboratory (7 kW)- and utility (400 MW)-scale combustion systems was investigated using X-ray absorption fine structure (XAFS) spectroscopy, X-ray diffraction (XRD), and acetate extraction [1 M NaOAc-0.5 M HOAc (pH 5) at 25 °C]-anodic stripping voltammetry (ASV). XAFS was also used to determine the Ni speciation of ambient particulate matter (PM) sampled near the 400-MW system. Based on XAFS analyses of bulk fly ash and their corresponding acetate extraction residue, it is estimated that >99% of the total Ni (0.38 wt %) in the experimentally produced fly ash occurs as NiSO₄-xH₂O, whereas >95% of the total Ni (1.70 and 2.25 wt %) in two fly ash samples from the 400-MW system occurs as NiSO₄-xH₂O and Ni-bearing spinel, possibly NiFe₂O₄. Spinel was also detected using XRD. Acetate extracts most of the NiSO₄-xH₂O and concentrates insoluble NiFe₂O₄ in extraction residue. Similar to fly ash, ambient PM contains NiSO₄-xH₂O and NiFe₂O₄;

however, the proportion of NiSO₄-xH₂O relative to NiFe₂O₄ is much greater in the PM. Results from this and previous investigations indicate that residual oil ash produced in the 7-kW combustion system lack insoluble Ni (e.g., NiFe₂O₄) but are enriched in soluble NiSO₄-xH₂O relative to fly ash from utility-scale systems. This difference in Ni speciation is most likely related to the lack of additive [e.g., Mg(OH)₂] injection and residence time in the 7-kW combustion system.     

煅烧-碱溶法制粉煤灰类沸石吸附剂及其在处理含铅废水中的应用

粉煤灰吸附性能研究是当前环境科学领域中的一个研究热点 ,但原状粉煤灰的吸附效果不理想。本文报道的用煅烧 -碱溶法制得类沸石吸附剂的比表面积为 112 .6m2 / g、孔隙率为 83 .1% ,分别是改性前的 40 .2 2和 1.67倍。用此类沸石吸附剂来处理浓度为 2 0 0mg/L的模拟含铅废水 ,去除率为 84.87% ,吸附容量为 3 3 .94mg/ g ,分别是改性前的3 1.13和 3 1.42倍 ,处理效果优于市售一级活性炭。并用 0 .1mol/L的HCl溶液和饱和NaCl溶液再生此吸附剂 ,解吸率达到了 98%以上 ,此再生的类沸石吸附剂处理含铅废水的去除率也达到了 83 %以上     

流化床锅炉飞灰活性激发与建材利用的试验研究

流化床锅炉飞灰活性较差,常规的粉煤灰活性激发方法对该飞灰效果不佳.本研究采用了加入适当激发剂的方法激发其活性,结果表明,加入激发剂后水泥胶砂的早期抗折、抗压强度均有100%的增长,后期抗折强度提高约100%、抗压强度提高60%以上,凝结时间和安定性均符合要求.水泥中飞灰掺量达40%时,其胶砂各龄期强度均达到甚至超过了42.5R水泥的强度;飞灰掺量65%～75%时,胶砂强度显示仍可生产一些低强度要求的建材产品,如砌筑水泥、建筑砂浆等.采用XRD、SEM等微观测试手段对飞灰活性激发机理进行了探讨.     

The effect of copper speciation on the formation of chlorinated aromatics on real municipal solid waste incinerator fly ash

A limited amount of information exists regarding the relationship between the chemical form of copper and the formation of chlorinated aromatics in fly ash. To understand the effects of the various forms of copper on the formation of chlorinated aromatics in real fly ash, we determined the chemical forms of copper present in various types of real fly ash using X-ray absorption near edge structure (XANES) and evaluated the relationship between the chemical forms of copper and the formation of chlorinated aromatics. Copper chloride hydroxide (CuCl2 x 3Cu(OH)2) and cuprous chloride (CuCl) were the predominant copper species found in real fly ash. Although pure cupric chloride (CuCl2) is known to be the most active catalyst for the formation of chlorinated aromatics under experimental conditions with synthetic fly ash, CuCl2 was not found in every real fly ash sample. The amount of copper chloride hydroxide was positively correlated with the formation of chlorinated aromatics in real fly ash and is, consequently, considered to be one of the key species involved in the formation of chlorinated aromatics.     

The capture of heavy metals from incineration using a spray dryer integrated with a fabric filter using various additives

This study investigated the effects of feedstock additives [polyvinyl chloride (PVC) and NaCl] and spray dryer additives (SiO2, CaCl2, NaHCO3) on heavy metal and fly ash removal efficiencies, and on particle size distribution of heavy metals. A spray dryer with an integrated fabric filter was used as an air pollution control device (APCD). Removal efficiencies for fly ash and heavy metals were greater than 95 and 90%, respectively. When additives of PVC or NaCl were used, the concentration of heavy metals distributed in fly ash apparently varied when the particle diameter was <1 microm. Although the effects of the additives SiO2, CaCl2, and NaHCO3 on the elemental size distribution of Cr were insignificant, these additives did slightly increase concentrations of Cd, Zn, and Pb partitioning in coarser particles (>1 microm).     

Utilization of nSiO2, fly ash, and nSiO2/fly ash composite for the remediation of triphenyltin (TPT) from contaminated seawater

The removal of triphenyltin chloride from contaminated simulated seawater with adsorption method was discussed. The adsorbents used are fly ash, nSiO₂, and nSiO₂/fly ash composite. The results showed that the adsorption of the adsorbents increases with increase in the adsorbent dose, contact time, pH, stirring speed, initial TPT concentration, and decreased with increase in temperature. The adsorption fitted well with the Freundlich isotherm, showing that the adsorbent and TPT combined with function groups and the adsorption kinetics followed the pseudo-second-order kinetic model. The thermodynamic parameters were also evaluated. Optimal conditions for the adsorption of TPT from simulated seawater were applied to TPT removal from natural seawater. A higher removal efficiency of TPT (>99 %) was obtained for the nSiO₂/fly ash composite but not for fly ash and nSiO₂.     

Study of the use of coal fly ash as an additive to minimise fluoride leaching from FGD gypsum for its disposal

The use of coal fly ash as a fluoride retention additive has been studied as a way of treating flue gas desulphurisation (FGD) gypsum for its disposal in landfills. With this end leaching studies following the standard EN-12457-4 [Characterization of waste- Leaching-Compliance test for leaching of granular waste materials and sludges - Part 4: One stage batch test at a liquid to solid ratio of 10l/kg for materials with particle size below 10mm (without or with size reduction)] have been performed on FGD gypsum samples treated with different proportions of fly ash (0.1-100%). It was found that the fluoride leachable content in FGD gypsum was reduced in the range 1-55%, depending on the fly ash proportion added to FGD gypsum. High levels of fluoride leaching reduction (close to 40%) were achieved even at relatively low fly ash additions (5%). So, low fly ash incorporations assure the characterization of this by-product as a waste acceptable at landfills for non-hazardous wastes according to the Council Decision 2003/33/EC [Council Decision 2003/33/EC of 19 December 2002 establishing criteria and procedures for the acceptance of waste at landfills pursuant to Article 16 of and Annex II to Directive 1999/31/EC] on waste disposal. Furthermore, the effectiveness of the proposed FGD gypsum stabilization method was also studied in column leaching systems, proving its good performance in simulated conditions of disposal. In such conditions a fluoride leaching reduction value slightly higher than 25% was displayed for a fly ash added amount of 5%.     

Dioxins, metals, and fish toxicity in ash residue from space heaters burning used motor oil

Ash residue, generated from burning used motor oil, is a complex and ubiquitous waste stream. Ash samples were collected from space heaters and analyzed for dioxins (N=10), expressed as toxic equivalents (TEQ), and heavy metals (N=9). TEQ averaged 148-164 ng kg(-1) (standard deviation [SD] 385-416 ng kg(-1)), depending on methods used for non-detects (NDs) and toxic equivalency factors (TEFs). It is notable that median TEQ (2.89-3.49 ng kg(-1)) was about 50 fold lower, reflecting the influence of several high end values on the mean. The proportion of NDs among 17 polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in each sample averaged 38.2% (range 0-94.1%). Total metals averaged 103,000 mg kg(-1) (SD 26,600 mg kg(-1)), with Zn, Cu, and Pb contributing 89.3%, 6.4%, and 3.0% of the total, respectively. Rainbow trout bioassays resulted in median mortalities of 3.2% and 42.0% (respective SD 25.3% and 43.2%) at ash concentrations of 10 and 100 mg l(-1), respectively. Nominal concentrations of several metals (e.g., Cu, Zn) in the fish bioassay exceeded their reported median lethal concentrations (LC50s) for the test species. Multiple regressions (Bonferroni P<0.05) demonstrated that most of the variance in fish mortality could be accounted for by pH, metals (e.g., As, Cd, Pb), and TEQ. Mean TEQ concentration in used oil ash ranked on the high end of TEQ content in other environmental matrices, including wood ash, cement kiln dust, biosolids, and soils. Overall, these results suggest that suitable disposal methods are needed for ash generated from burning used motor oil.     

Effect of reaction time on PCDD and PCDF formation by de novo synthetic reactions under oxygen deficient and rich atmosphere

The effect of reaction time on formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) was studied under laboratory conditions in the system containing municipal waste incineration fly ash, activated carbon and copper chloride dihydrate at 300 degrees C in 99.999% N2 and N2 + 10% O2 atmosphere. The concentrations of tetra- to octa-chlorinated isomers as well as I-TEQ concentrations of toxic congeners are reported. The mechanism of PCDD and PCDF formation from chlorophenols and chlorinated biphenyls is discussed in the light of the time changes of PCDD/PCDF ratios.     

滤料负载粉尘层对气态汞脱除性能的实验研究

通过不同性能纤维滤料负载燃煤飞灰粉尘层,来模拟袋式除尘器滤袋表面粉尘附着层,进而研究袋滤器用不同性能纤维滤料和粉尘附着层对燃煤烟气中Hg0的联合脱除性能。在固定床实验系统上分别进行了不同纤维滤料和燃煤飞灰粉尘层,以及经实验优选得到的华博特滤料负载燃煤飞灰粉尘层脱除燃煤烟气中Hg0的实验研究。结果表明,燃煤飞灰粉尘层和华博特滤料对Hg0分别有一定的脱除作用,脱除效率可达35%和42.5%,它们对Hg0的脱除是物理吸附和化学吸附共同作用的结果;同时,华博特滤料负载燃煤飞灰粉尘层对Hg0的联合脱除效率受到吸附反应温度、入口汞浓度和烟气停留时间等因素的影响,最佳脱汞率可达64.4%;吸附反应温度越高,脱除效率越低;烟气停留时间越大,脱除效率越高;入口汞浓度的提高并不一定提高华博特滤料负载飞灰粉尘层的脱汞效果。     

垃圾焚烧飞灰浸出特性及固化试验的研究

垃圾焚烧飞灰残留有重金属元素和二恶英等物质而被认为是危险废物,必须对之进行稳定化处理.通过试验研究分析了国内首家自主开发成功的广东省东莞市某回转窑垃圾焚烧发电厂垃圾焚烧飞灰的化学成分及矿物组成,研究了飞灰的浸出毒性,考察了水泥固化焚烧飞灰的效果,并与熔融/玻璃固化进行了比较.研究表明,该焚烧飞灰中重金属Cd的浸出毒性严重超标,并且随pH值的减小而增大,水泥固化效果随龄期的增大而更加显著.熔融/玻璃固化的效果优于水泥固化,但其经济性有待提高.     

Latent hydraulic reactivity of blended cement incorporating slag made from municipal solid waste incinerator fly ash

The reactivity of cement pastes made by blending Portland cement with slag from municipal solid waste incinerator (MSWI) fly ash was investigated to assess the potential of recycling MSWI fly ash slag. The slag, prepared by melting MSWI fly ash at 1400 degrees C for 30 min, was pulverized and ground, then blended with ordinary Portland cement (OPC), using various substitution levels to make slag-blended cement (SBC). The pozzolanic reactivity of the ecocement was then characterized by determining variations in the compressive strength, degree of hydration, microstructure, speciation, and mineralogical crystalline phases. The results suggest that the strength of the pastes at an early age decreased with increasing substitution levels, whereas the strength at a later age of the tested pastes (with substitution levels less than 10%) outperformed OPC paste because of typical SBC properties. The development of strength at a later age was also confirmed by X-ray diffraction and scanning electron microscopy techniques. This implies that active silica (Si) and alumina (Al) react with the hydration product, calcium hydroxide (Ca(OH)2), to form calcium silicate hydrate (C-S-H), which contributed to strength development at a later age by the filling up of pores in the SBC pastes. The pozzolanic activity of the SBC pastes indicates that it is suitable for use as a substitute for OPC in blended cement.     

Formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from residual carbon on municipal solid waste incinerator fly ash using Na37Cl

Na37Cl was used to study the role of chlorine in the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) from carbon. Adding Na37Cl to fly ash showed that this compound was a (relatively) poor chloride source; chlorine naturally present on the ash - which could include both chlorine in residual carbon and (metal) chlorides - was found to be ca. 17x more reactive. When both Na37Cl and CuCl2 were added to aqueous extracted fly ash, the percentage of 37Cl from Na37Cl included in PCDD/F increased, compared to the combination of Na37Cl/fly ash. When Na37Cl and CuCl2 were exchanged in water, followed by evaporation of the solvent, and mixed with aqueous extracted fly ash, the percentage of 37Cl included in PCDD/F was much higher. Apparently, direct transfer of 37Cl from CuCl2 to carbon and PCDD/F was much faster than transfer of 37Cl- from Na37Cl via a metal chloride (such as CuCl2) to carbon and PCDD/F. In addition to chlorine in PCDD/F originating from exchanged NaCl/CuCl2, chloride left on the fly ash after aqueous extraction and chlorine present in residual carbon could also have been incorporated in PCDD/F.     

控制城市垃圾焚烧二噁（口英）产生与扩散方法

控制垃圾焚烧二产生与扩散分三部分首先,通过预处理除去原生垃圾中的聚氯乙烯塑料,从源头上控制垃圾焚烧二哄产生的物质基础;其次,垃圾焚烧炉采用组合式循环流化床锅炉,实行垃圾先低温热解气化,然后高温燃烧垃圾热解气体的方式,同时在炉内加入添加剂实现稳定燃烧和部分脱氯,以减少二哄在炉内生成和炉后形成量;最后,在烟气尾部采用吸附剂吸附二哄,并与布袋除尘器配套使用,控制二哄的尾部扩散.该工艺具有成本低、控污效率高等优点,特别适用于发展中国家的垃圾焚烧二哄控制.     

Latent Hydraulic Reactivity of Blended Cement Incorporating Slag Made from Municipal Solid Waste Incinerator Fly Ash

Abstract

The reactivity of cement pastes made by blending Portland cement with slag from municipal solid waste incinerator (MSWI) fly ash was investigated to assess the potential of recycling MSWI fly ash slag. The slag, prepared by melting MSWI fly ash at 1400 °C for 30 min, was pulverized and ground, then blended with ordinary Portland cement (OPC), using various substitution levels to make slag-blended cement (SBC). The pozzolanic reactivity of the ecocement was then characterized by determining variations in the compressive strength, degree of hydration, microstructure, speciation, and mineralogical crystalline phases. The results suggest that the strength of the pastes at an early age decreased with increasing substitution levels, whereas the strength at a later age of the tested pastes (with substitution levels less than 10%) outperformed OPC paste because of typical SBC properties. The development of strength at a later age was also confirmed by X-ray diffraction and scanning electron microscopy techniques. This implies that active silica (Si) and alumina (Al) react with the hydration product, calcium hydroxide (Ca(OH)₂), to form calcium silicate hydrate (C-S-H), which contributed to strength development at a later age by the filling up of pores in the SBC pastes. The pozzolanic activity of the SBC pastes indicates that it is suitable for use as a substitute for OPC in blended cement.     

The Capture of Heavy Metals from Incineration Using a Spray Dryer Integrated with a Fabric Filter Using Various Additives

ABSTRACT

This study investigated the effects of feedstock additives [polyvinyl chloride (PVC) and NaCl] and spray dryer additives (SiO₂, CaCl₂, NaHCO₃) on heavy metal and fly ash removal efficiencies, and on particle size distribution of heavy metals. A spray dryer with an integrated fabric filter was used as an air pollution control device (APCD). Removal efficiencies for fly ash and heavy metals were greater than 95 and 90%, respectively. When additives of PVC or NaCl were used, the concentration of heavy metals distributed in fly ash apparently varied when the particle diameter was <1 μm. Although the effects of the additives SiO₂, CaCl₂, and NaHCO₃ on the elemental size distribution of Cr were insignificant, these additives did slightly increase concentrations of Cd, Zn, and Pb partitioning in coarser particles (>1μm).     

CaCl2高温热处理垃圾焚烧飞灰中重金属的挥发特性

以深圳市某垃圾焚烧厂飞灰为原料,采用高温管式电阻炉,研究了在0．6L／minN,气氛下,CaCl2在不同添加量、处理温度及处理时间下对飞灰中重金属Pb、Cd、Zn和Cu挥发特性的影响,并对收集到的二次飞灰进行成分及物相分析。结果显示,X射线衍射仪和EDS分析表明,二次飞灰主要是由NaCl、KCl和部分SiCl4组成,zn主要以K2ZnCl4形式挥发,而Pb则主要以氧化物PbO和Pb3SiO5的形式挥发。最终得到CaCl2热处理飞灰的最佳二次气化条件：以0．6L／minN,为载气,添加14wt％的CaCl2,在1100℃高温下处理2．5h。经CaCl2热处理后的剩余飞灰,其浸出毒性达到了《生活垃圾填埋场污染控制标准》要求。     

水泥对垃圾焚烧飞灰的固化处理试验研究

对垃圾焚烧飞灰的化学成分、重金属物质的含量及浸出浓度进行测试分析.结果表明,飞灰中Pb和Cr等重金属物质浸出量超过浸出毒性标准,因而被认为是危险废物,必须进行固化处理.还考察了水泥对焚烧飞灰中重金属物质固化的效果,研究表明当飞灰掺量适当时,重金属物质的固化效果良好.重金属物质通过物理固封、替代,沉淀反应和吸附等形式可固化进水泥水化产物结构中.     

Boiler briquette coal versus raw coal: Part II--Energy, greenhouse gas, and air quality implications

The objective of this paper is to conduct an integrated analysis of the energy, greenhouse gas, and air quality impacts of a new type of boiler briquette coal (BB-coal) in contrast to those of the raw coal from which the BB-coal was formulated (R-coal). The analysis is based on the source emissions data and other relevant data collected in the present study and employs approaches including the construction of carbon, energy, and sulfur balances. The results show that replacing R-coal with BB-coal as the fuel for boilers such as the one tested would have multiple benefits, including a 37% increase in boiler thermal efficiency, a 25% reduction in fuel demand, a 26% reduction in CO2 emission, a 17% reduction in CO emission, a 63% reduction in SO2 emission, a 97% reduction in fly ash and fly ash carbon emission, a 22% reduction in PM2.5 mass emission, and a 30% reduction in total emission of five toxic hazardous air pollutant (HAP) metals contained in PM10. These benefits can be achieved with no changes in boiler hardware and with a relatively small amount of tradeoffs: a 30% increase in PM10 mass emission and a 9-16% increase in fuel cost.