Minerals In Fly Ash Research Articles

Lithium activation pretreatment mechanism and leaching process from coal fly ash

As a result of the coal combustion process, high lithium enrichment in fly ash has been observed in some areas of China, which is considered to be a potential unconventional lithium resource. At present, most of the studies on lithium in fly ash focus on the leaching process, while there are fewer studies on the activation mechanism of roasting. In view of the above problems, the roasting activation mechanism of fly ash in the Pingshuo mining area (northern China) is investigated, and the leaching process of lithium is optimized. The activation pretreatment that destroys an inert composition of fly ash is necessary. In this study, fly ash and a mixed roasting agent (Na2CO3 and K2CO3 mass ratio of 3:1) were mixed at a mass ratio of 2:1 under 950 °C for 2 h. The results showed that the leaching rate of lithium increased by 70%. Direct acid leaching experiments show that 90% lithium in fly ash is related to insoluble aluminosilicate minerals. The mineralogical analysis of the calcined product shows that the stable aluminosilicate minerals in fly ash disappear and form nepheline KNa3(AlSiO4)3 which is soluble in acid, and the percentage of nepheline in the roasted product controls the leaching rate of lithium. The kinetic analysis of the acid leaching process of the roasting product shows that the lithium leaching process is mainly controlled by chemical reactions. Under the optimal leaching conditions, the leaching rate of lithium is 87.41%.

Effects of alkali activation and hydrothermal processes on the transformation of fly ash into Al-substituted tobermorite fiber

By choosing two sample fly ash with different chemical compositions and calcium-bearing mineralogical phases, this article explored the influence of calcium-bearing minerals in fly ash and hydrothermal methods on the synthesis of tobermorite fiber. It was found that fly ash with more than 20% calcium oxide content easily decomposed and transformed into 9 Å and 11 Å tobermorite fiber, with the tobermorite content exceeding 30%, under the conditions of hydrothermal solution without alkali and 1 h reaction time. It was demonstrated by FTIR spectrogram and solid NMR analysis results that calcium-bearing mineral is a significant factor which can trap most of Al2O3 in the fly ash, preventing it from soaking up into the lattice of tobermorite, and also inhibiting the substitution of Si by Al. A thermal activation method was designed to enhance the transformation process of fly ash with lower calcium concentration by a similar mechanism to calcium action.

A rational and feasible approach to the co-management of condensates from biomass torrefaction and carbon-rich fly ash from fluidized-bed coal gasification

This study explored a promising approach to the co-management of torrefaction condensates (TCs) from biomass and carbon-rich fly ash (FA) derived from an industrial fluidized-bed coal gasifier. TC was a low-quality liquid product consisting mostly of water and a small amount of organic acids and other oxygenated organics. FA was the ultra-fine particulates with high carbon content (40–70%) and some extreme characteristics such as ultra-low volatiles, low reactivity, and high ignition temperature. The blending of FA and TC induced most of the organic components in TC to be chemically or physically adsorbed by FA, accounting for 3–13 wt% of the resultant mixtures of FA and TC (FATCs) and 11–33 wt% of the TCs. The acidic components in TC dissolved locally aggregated Ca minerals in FA, resulting in more evenly dispersed Ca on the surface of FA as an in-situ catalyst. As a result, FATCs exhibited a many-fold improvement in CO2 gasification reactivity compared to FA. And the syngas evolution rate of FATC gasification in steam-oxygen atmosphere was also remarkably elevated. In addition to the promoting effect on gasification, the combustion performance of FATCs was also greatly improved. Specifically, the ignition and burnout temperatures of FATCs were 46.5–68.5 °C and 12.4–31.7 °C lower than those of raw FA, respectively. The lower activation energy also demonstrated the higher reactivity of FATC gasification and combustion.

Study of the Mechanical Properties of Alkali-Activated Solid Waste Cementitious Materials at the Interface.

The paper uses alkali-activated slag and fly ash as cementitious materials to pour and repair concrete. Their modification on the bonding surface of new and old concrete is studied. The new and old concrete composite specimens were prepared. The split tensile strength test of the new and old concrete specimens along the interface was carried out, and the test results of different alkali-stimulated slag and fly ash concrete as repair materials were compared and analyzed. The influence of activator modulus and other factors on the bond strength of new and old concrete interfaces was studied, and the law of its strength change was explored. The research results show that with the gradual increase in the amount of fly ash minerals, the splitting tensile strength presents a trend of first increasing and then decreasing. When the amount is 50%, the splitting surface partly occurs on the old concrete. It shows that the bonding effect is the best at this content; the alkali excitation modulus gradually increases, and the splitting tensile strength shows a downward trend. When the activator modulus is 1.3, more gelatinous substances can be observed in the section of the specimen. These overlap each other to form a tight material skeleton structure; a comparative analysis of the bonding strength of the new and old concrete interfaces with different interface agents and without interface agents showed that the alkali-activated solid waste cementitious material has the best repair performance and greater bonding strength when the water-to-binder ratio is 0.3.

Hydration Mechanisms of Alkali-Activated Cementitious Materials with Ternary Solid Waste Composition.

Considering the recent eco-friendly and efficient utilization of three kinds of solid waste, including calcium silicate slag (CSS), fly ash (FA), and blast-furnace slag (BFS), alkali-activated cementitious composite materials using these three waste products were prepared with varying content of sodium silicate solution. The hydration mechanisms of the cementitious materials were analyzed by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. The results show that the composite is a binary cementitious system composed of C(N)-A-S-H and C-S-H. Si and Al minerals in FA and BFS are depolymerized to form the Q0 structure of SiO4 and AlO4. Meanwhile, β-dicalcium silicate in CSS hydrates to form C-S-H and Ca(OH)2. Part of Ca(OH)2 reacts with the Q0 structure of AlO4 and SiO4 to produce lawsonite and wairakite with a low polymerization degree of the Si-O and Al-O bonds. With the participation of Na+, part of Ca(OH)2 reacts with the Q0 structure of AlO4 and the Q3 structure of SiO4, which comes from the sodium silicate solution. When the sodium silicate content is 9.2%, the macro properties of the composites effectively reach saturation. The compressive strength for composites with 9.2% sodium silicate was 23.7 and 35.9 MPa after curing for 7 and 28 days, respectively.

Characteristics of MSWI fly ash with acid leaching treatment

The chemical and mineralogical characteristics of fly ash from a municipal solid waste incineration (MSWI) in China and the influence of processing parameters on heavy metals removal during leaching were investigated in this work. The fly ash particles had complex surface structure with limited specific surface area. The alkali chloride and metal salts in MSWI fly ash showed evidently impact on leaching efficiency. Metal leachability was related to their properties and speciation in fly ash. Water-soluble salts such as KCl, NaCl and CaCl2 in fly ash were easily washed out. In this study, removal efficiency by water washing was achieved to 93.1% for Cl, 41.4% for Na, 48.5% for K and 24.8% for Ca, respectively. Mineralogical analysis also revealed change of fly ash mineral phases and specification distribution after water washing. Under liquid to solid ratio of 40:1 L/kg and treatment time of 120 min, the leaching process achieved high dropping yields of toxicity characteristic leaching procedure (TCLP) concentrations for Cu, Zn Cd and Pb (80%–100%), moderate dropping yields for As (30%–80%) and relatively low dropping yields of Ni (< 30%). In addition, heavy metals such as Pb and Zn in fly ash with twice water washing treatment at a low liquid-solid ratio could reach lower TCLP concentrations. The result indicated that the combination process of twice water washing and one acid washing could significantly reduce the environmental risk of MSWI fly ash.

Mechanical properties and acid attack test of hybrid fiber reinforced high performance concrete for fly ash based mineral admixture

The scope of the present investigation the mechanical properties and acid attack test of hybrid fiber reinforced high performance concrete (HFRHPC) for Fly ash (FA) based mineral admixture. HFRHPC is prepared by adding crimped steel fibers and polypropylene fiber to the concrete to make it a composite mixture. It derives benefits from each of the added fibers and exhibits significant response. A constant proportion of 0.25% for polypropylene fibers (PF) and varying proportions of 0%, 0.5%, 0.75% and 1.0% for crimped steel fibers (SF) making a total fiber volume fractions of 0%, 0.75%, 1.0% and 1.25% were used to develop hybrid fiber. Four replacement levels for hybrid fibers by volume of the binders and four partial replacement levels for FA (0%, 10%, 20% & 30%) by weight of cement have been considered for three different water binder ratios (0.275, 0.325 & 0.375). An aggregate binder ratio of 1.75 was kept constant. This study shows that hybrid fiber may improve the mechanical properties of fly ash-based high-performance concrete. Acid attack tests have been conducted to measure the durability of HFRHPC. Cubes have been cast, cured, and immersed in 5% concentrated solutions of Hydrochloric acid (HCL), Magnesium sulphate (MgSO4), and Sulphuric acid (H2SO4) for 30, 60 and 90 days and then tested to record the residual compressive strength of HFRHPC produced with the fly ash mineral admixtures. It was observed that a combination of 1.25% hybrid fibers and 10% FA as cement replacement resulted in enhanced mechanical performance and acid resistance.

In-situ reaction between arsenic/selenium and minerals in fly ash at high temperature during blended coal combustion

Blended coal combustion technology was extensively used in coal-fired power plants in China. In order to investigate the in-situ reaction between trace elements and minerals in fly ash during blended coal combustion, a bituminous (HLH), anthracite (ZW) and the blended coal of these two parent coals were combusted in a drop tube furnace at 1150°C. The ash gathered at high temperature segment (HTA) and low temperature segment (LTA) of the furnace were analyzed, respectively. The results indicated that the retention rates of arsenic in HTA were lower than that in LTA, which suggested that arsenic would be re-absorbed by ash during cooling down of flue gas. For HTA the retention rates of arsenic in ash of ZW, Z3H1, Z1H1, Z1H3, HLH were 60.31%, 26.85%, 13.29%, 20.23% and 36.11%, respectively. The arsenic was more difficult to be captured by HTA of blended coal than that of parent coal. As for selenium, the retention rates in HTA of five coal samples were 24.68%, 23.60%, 20.58%, 15.19% and 38.13%, which had the same retention law as arsenic. The results of X-ray diffraction (XRD) demonstrated that the mineral morphology was changed obviously during blended coal combustion. Unlike parent coal, mullite appeared in HTA of blended coal, and peak of mullite was enhanced with proportion of ZW increased in blended coal. It was consistent with the trend of retention of As and Se in HTA. It illustrated that change of mineral species and in-situ reaction between minerals and trace elements significantly affected emission of arsenic and selenium during blended coal combustion.

Mechanism study of selenium retention by iron minerals during coal combustion

The interactions between selenium vapors and coal accessory Ca/Fe-minerals favor selenium emission control by transferring selenium into fly ash during coal combustion. Considering the complicated effects of iron transformation on selenium retention, iron species in fly ashes from seven coal-fired power plants were distinguished and the associations between selenium and iron minerals were assessed. Iron oxides (including Fe3O4, γ-Fe2O3 and ɑ-Fe2O3) were determined as the main form of iron minerals in fly ash. The adsorption of selenium vapors by different iron oxides was conducted at temperatures ranging from 300 to 900 °C and the species of captured selenium were identified. Furthermore, reaction sites on the surfaces of fresh and reacted iron oxides were compared to investigate the mechanism regarding selenium adsorption over these iron oxides, which were further clarified through density functional theory study. The results showed that iron oxides were surely to play a significant role in selenium retention mainly through chemisorption and the reactions probably occurred at temperatures below 900 °C. At 300 °C, ɑ-Fe2O3 had better selenium adsorption performance than Fe3O4/γ-Fe2O3. Regardless of iron species, Fe atoms on iron oxides participated in the selenium adsorption by forming a Se–O–Fe Structure. With temperature increasing, selenium adsorption by Fe atoms was suppressed, which caused a drop off in selenium capture capacity of Fe3O4 and ɑ-Fe2O3. Differently, increasing temperature promoted selenium adsorption over γ-Fe2O3, which owned a high selenium adsorption capacity even at 700 °C. Further analysis confirmed that the presence of O2/H2O(g) in the flue gas contributed to the formation of oxygen vacancies on the surface of γ-Fe2O3 at high temperatures and facilitated selenium vapors to react with Fe atoms.

The influence of utilizing slag in lieu of fly ash on the performance of engineered cementitious composites

The need for sustainable power generation resources is increasing day after day. Among many countries around the world, Canada is considering elimination of coal plants. This is causing a shortage in the supply of good quality fly ash minerals. Recent research on the production of engineered cementitious composites (ECC) focused on utilizing of Class F Fly Ash. Hence, this study was designed to experimentally investigate the influence of partial and full replacement of slag with fly ash on the mechanical and durability performance of ECC mixtures through a comprehensive experimental program. Test results from this study showed that slag containing mixtures exhibited strain-hardening behaviour and a comparable or similar ductility characteristics as fly ash containing mixtures. Moreover, incorporating slag in the mixtures were found to be effective in reducing permeability in terms of rapid chloride penetration, sorptivity, and water absorption at both 28 and 90 days. However, mixtures containing slag had higher drying shrinkage strains when compared to fly ash mixtures.

Characteristics of ash and slag from four biomass-fired power plants: Ash/slag ratio, unburned carbon, leaching of major and trace elements

The utilization of biomass energy is attracting worldwide attention due to the worsening energy crisis and the concerns on carbon dioxide emission. However, the rapidly development of biomass-fired power plants generate enormous amount of slag and ash. At present, the main treatment method of biomass slag and ash is landfill, which not only requires high cost, but also causes a series of environmental issues. Aiming at this problem, the slag and fly ash from four biomass power plants were sampled and characterized. The major/trace element composition and leaching characteristics of slag and fly ash are analyzed, and the effect of volatile mineral in these solid residues on furnace efficiency is also evaluated. The results indicate that for biomass-fired grate furnaces, in the generated solid residues, the slag accounts 60 ~ 70% while the fly ash accounts for 30 ~ 40%. The volatile elements in slag are much lower than those in fly ash, and the unburned carbon content of fly ash is generally lower than that of slag. Due to the enrichment of volatile minerals in fly ash, instead of 815 °C, 550 °C is suggested to measure the unburned carbon content in fly ash. When the measuring temperature of unburned carbon decreases from 815 °C to 550 °C, the measured energy loss from the incomplete combustion of solid fuels decreases by one third, which affords a more reasonable evaluation on combustion efficiency. The contents of cadmium and lead in certain fly ash samples exceed the standard, however, all fly ash samples have a high leaching rate of potassium but low leaching rates of copper, zinc, cadmium, lead, chromium and arsenic. It indicates that the fly ash from biomass-fired grate furnace is suitable for producing potassium fertilizer by leaching instead of direct soil fertilization or landfill. The leaching rate of most minerals in slag is much lower than that in fly ash and the contents of heavy metals are far below the prescribed upper limit in standard, which indicates that the slag from biomass-fired grate boiler is more suitable for direct use in soil improvement due to the low contents of hazardous elements.

Sulphates removal from AMD using CFA hydrothermally treated zeolites in column studies

Hydrothermally treated zeolites were synthesized from a coal combustion waste by-product, coal fly ash. Synthesis of this material involved dissolution of the coal fly ash matrix followed by crystallization of the slurry. Characterization of coal fly ash using BET indicated that the coal fly ash had a surface area of 3.141 m2 g−1. The XRD patterns on coal fly ash showed dominance of the mullite and quartz peaks and was observed to be amorphous. The optimized parameters for dissolution of the coal fly ash matrix was a concentration of 3 M NaOH aged for 24 h at a solid/ liquid ratio of 15 g/120 mL. The second stage was focused on optimization of crystallization conditions of the CFA/NaOH slurries for synthesis of zeolite. The effect of variation of water content, crystallization time and crystallization temperature were studied where the optimized conditions obtained were a H2O/SiO2 ratio of 0.53, crystallized at 140 °C for a duration of 24 h. Powder x-ray diffraction studies indicated successful conversion of coal fly ash into zeolites as the dominant coal fly ash minerals such as mullite and quartz diminished while the zeolitic hydroxysodalite phase was formed. Fourier transform infra-red studies showed formation of zeolitic bands at 948 cm−1 due to Al–O and Si–O asymmetric stretching, indicating conversion of the CFA aluminosilicate phase. Thereafter, the adsorption performance of hydrothermally treated zeolites for SO42 was evaluated. The parameters evaluated included, zeolite bed height, flow rate and concentration where the optimized conditions were 4.0 cm, 0.45 mL min−1 and 5.0 mg L−1 respectively. Application studies on AMD derived water from Fleurhof dam indicated an anion selectivity with an increasing order of Cl− < NO3– < Br− < NO2– < SO42−.

Mineralogy and geochemistry of feed coals and combustion residues of the Kangal power plant (Sivas, Turkey)

This study focuses on mineralogical and geochemical compositions of feed coal (FC) and combustion residues, namely fly ash (FA) and bottom ash (BA) samples, obtained from the Kangal coal-fired power plant in central Turkey. The X-ray powder diffraction data indicate that carbonate and clay minerals are dominant phases in the FC samples. In the FA samples, quartz, hematite, anhydrite, lime, and feldspar are generally dominant and abundant phases, whereas calcite, ettringite, and portlandite are generally more abundant in the BA samples. The elements Mo, Cs, and U are significantly enriched in the studied FC, FA, and BA samples. The statistical analysis and SEM-EDX data show that Ca, Ti, and the vast majority of trace elements are inorganically affiliated, and only Tl and U have prob-able organic affinity in the FC. In addition, the redox conditions in the paleomires presumably resulting in Mo and U enrichment in FC, whereas their enrichment in FA and BA is most likely related to retention by CaO and Ca-sulfate. The Cs enrichment in FA is due to retention by glass. The elements in the FA and BA are distinguished into four groups according to their volatility during combustion. The elements As, Mo, Cd, Tl, and U (Group I) are the most volatile elements during combustion and condensation in the FA. The elements Li, Zn, Ga, Rb, Nb, Cs, Ba, La, and Pb (Group IV) did not become more volatile or less volatile during combustion and are located in BA. Nevertheless, Zn and Pb in the BA seem to be related to the presence of unaffected pyrite and sphalerite, and are due to low combustion efficiency of the boiler during the sampling period. Overall, enriched elements and minerals in FA and BA suggest that their disposal should be undertaken with caution.

TINJAUAN PENAMBAHAN ADITIF MINERAL ABU TERBANG TERHADAP KETAHANAN BETON PADA LINGKUNGAN AGRESI SULFAT

&lt;p&gt;&lt;em&gt;The research aims to determine ( 1) the increase of compressive strength of concrete with addition of fly ash to be compared to normal concrete ( 2) the resistant of normal concrete and also concrete with fly ash mineral additive in 2%, 5% and 7% sulphuric acid solutions, and ( 3) the resitant of concrete with fly ash mineral additive with the increase of concentration of sulphuric acid solution in comparing normal concrete.&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;em&gt;The method employed in this research was experimental method, by preparing the test object constituting the concrete cylinder with &lt;/em&gt;&lt;em&gt;Æ&lt;/em&gt;&lt;em&gt; 150 mm and 300 mm height for the compressive strength test. With the percentage of fly ash addition are 0%, 20%, 30% and 40% from requirement cement and qualities of designed concrete is 22,5 MPa. Amount of object test to the each condition is 4. To know concrete resistant in sulphate aggression environment, hence conducted by immersied of concrete in sulphuric acid solutions with concentration 2%, 5% and 7% during 30 days.&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;em&gt;From the research, it can be found that: ( 1) the addition of fly ash into fresh concrete will improve compressive strength of concrete. At addition fly ash 20% from requirement cement, compressive strength of concrete increase 23,39%. For the addition of fly ash 30% and 40%, the increase of compressive strength concrete were 21,54 % and 0,31%. While in optimum percentage of fly ash addition is 23,46% (2) the immersied concrete in sulphuric acid solution result degradation compressive strength of concrete. At the same concentration of sulphuric acid solution, concrete with fly ash additive mineral have resistant which is better to be compared to normal concrete. This seen [at] percentage of compressive strength degradation of fly ash concrete which is smaller to be compared to normal concrete. Equally the percentage of compressive strength degradation inversely proportional with the percentage of fly ash addition ( 3) the increase of concentration of sulphuric acid solution will be result of aggression that happened at ever greater. If compared to normal concrete, concrete with fly ash in the reality more effective if used at high concentration of sulphuric acid solution. This matter can be seen from difference of percentage of compressive strength degradation ever greater at the height of concentration of sulphuric acid solution.&lt;/em&gt;&lt;/p&gt;

Effect of Mineral Filler type on Strength of Roller Compacted Rubbercrete for Pavement Applications

This paper investigated the possibility of using crumb rubber as partial replacement to fine aggregate in roller compacted concrete for pavement applications where fine aggregate was replaced with crumb rubber at 0%, 10%, 20% and 30% to produce roller compacted rubbercrete (RCR). In order to achieve a combined aggregate gradation similar to the one recommended by ACI 211.3R and US Army Corps of Engineers method, fly ash was used as mineral filler. Several trials were done to achieve the combined grading, and finally a combination of 55% fine aggregate, 40% coarse aggregate and 5% fly ash as mineral filler was used. Silica fume was then used as mineral filler instead of fly ash and the fresh density and compressive strength were compared. A target flexural strength of 4.5 MPa and the mix design was developed using the geotechnical concept according to ACI 211.3R/CRD-C161-92. The Results showed that fresh density and compressive strength decreases with increase in partial replacement of fine aggregate with crumb rubber. RCR containing silica fume showed lower fresh density and higher compressive strengths than that with fly ash. However, all the mixes achieved a strength higher than the design target strength at 28 days except for 30% crumb rubber containing fly ash mineral filler, while 10% crumb rubber achieved target strength even at 3 and 7 days for silica fume and fly ash.

Use of Secondary Ion Mass Spectrometry (SIMS) to identify fly ash mineral spatial and particulate distribution in epoxy polymer

Fly ash from coal power stations consists typically of a series of oxide minerals. These minerals can have beneficial effects when used as reinforcement in a plastic matrix. In this work the advanced technique SIMS has been utilised to identify the spatial distribution of the various minerals in fly ash in an epoxy matrix with fly ash weights of 10% and 50%. It is observed that SIMS, which can scan normally to a precision of 0.5 to 0.05wt.%, could positively identify the distribution of the fly ash mineral elements in the epoxy. Attempts were also made to identify the fly ash element distribution in the epoxy using a composition analysis method, namely, EDS. However, it is observed that in the present fly ash–epoxy composites, EDS could not identify the fly ash elements demonstrating SIMS is a much preferred identification technique than the popular EDS method.

Use of fly ash with no water consumption for cold regions transportation infrastructure

The construction period in cold regions is very short due to problems related to excavation and use of frozen soils in embankment construction, which leads to excessive deformations upon thawing. Also, handling of compaction water is critical due to freezing temperatures. Coalburning thermal power plants are very common in cold regions to supply electricity. The inorganic part of the pulverized coal after burning produces fly ash, which is available in large volumes. Due to excavation difficulties and the poor engineering behavior of frozen soils in cold regions, the utilization of fly ash when it is readily available must be promoted. Any construction technique which utilizes alternative materials like fly ash and minimizes water consumption has a potential to extend the short construction season and even allow service and maintenance during extreme weather conditions. This paper presents two potential techniques to solve the moisture affinity of silt-sized materials like fly ash. One technique involves in-plant production of fly ash pellets using cold-bonding pelletization to manufacture aggregates of up to 40,000-μm diameter from 15- to 60-μm-diameter fly ash grains. Large disc pelletizers have annual production capacities of up to one million ton at a reasonable cost. The product has adequate strength for embankment construction even when no water is used and no compaction is applied. The second technique is an in situ mixing technique which uses snow instead of compaction water for fly ash. The snow is the main element in this technique to compact the embankment. Water is needed for the hydration reactions to form cementitious minerals in fly ash. The slower the hydration reaction, the greater the crystal growth of cementitious minerals. In the proposed technique, in situ snow is mixed with fly ash and is compacted on-site. The temperature increase due to the hydration reaction of fly ash upon contact with snow crystals provides water for continued long-term hydration, which results in high strength, a hig

Effects of Blended Steel Slag-Superfine Fly Ash Mineral Admixture and Ordinary Fly Ash on the Properties of Concrete

The effects of blended steel slag-superfine fly ash mineral admixture and ordinary fly ash on the properties of concrete were compared in this study. The results show that, in the case of the same adding amount, blended steel slag-superfine fly ash mineral admixture and ordinary fly ash have similar effects on the early strength and chloride ion permeability of concrete. Blended mineral admixture has higher ability to improve the late strength of concrete than ordinary fly ash. Paste and concrete containing blended mineral admixture have smaller porosities than that containing ordinary fly ash. Blended steel slag-superfine fly ash is an ideal mineral admixture for concrete.

Comparison of the Spray Combustion Characteristics and Emissions of a Wood-Derived Fast Pyrolysis Liquid-Ethanol Blend with Number 2 and Number 4 Fuel Oils in a Pilot-Stabilized Swirl Burner

Biomass fast pyrolysis liquid (bio-oil) is a cellulose-based alternative fuel with the potential to displace fossil fuels in stationary heat and power applications. To understand the combustion behavior and emissions of bio-oil, a 10 kW spray burner was designed and constructed. The effect of swirl, atomization quality, ignition (pilot) energy, and total primary combustion air on the stability and emissions of bio-oil spray flames was investigated. A blend of 80% pyrolysis liquid and 20% ethanol by volume was used during the tests, and the results were compared to the burner operation with number 2 and number 4 fuel oils. Bio-oil exhibits higher emissions than number 2 fuel oil at any given operating point. This is primarily due to better atomization quality with number 2 fuel oil, although not as a consequence of viscosity differences, which are minor at the measured fuel temperature in the nozzle (>80 °C). The disparity in atomization quality is caused by differences in the relative amount of atomizing air to liquid fuel flow rate provided to the nozzle at a fixed energy throughput. Another factor that contributes to higher bio-oil blend emissions is worse overall distillation characteristics compared to number 2 fuel oil. As a fully distillable fuel that evaporates high-energy compounds, number 2 fuel oil is far less sensitive to changes in flame stability or blow-off brought upon by varying the swirl number, atomizing air, pilot energy, or primary combustion air flow rate. Because of a combination of these atomization quality and fuel volatility effects, the bio-oil blend cannot operate over as wide of a range of primary air or atomizing air flow rates as number 2 fuel oil. The bio-oil blend has a lower boiling point than diesel and is much more susceptible to flashing-induced combustion instabilities, which lead to intermittent blow-out and higher CO emissions. The NOx and particulate emissions of number 2 fuel oil are lower than bio-oil because of the negligible fuel nitrogen and ash contents in the fuel, respectively. Number 4 fuel oil is more comparable to bio-oil because of its nondistillable fraction, fuel nitrogen, and ash contents. CO and hydrocarbon emissions are lower than the bio-oil blend, but total particulates and carbonaceous residues are higher for number 4 fuel oil. This is despite better atomization and a lower nondistillable fraction, suggesting that the fuel-oil residues are more difficult to burn out completely. Fuel NOx conversion efficency of number 4 fuel oil is similar to the bio-oil blend. There are differences in fly ash mineral composition between the two fuels, as well as a much higher sulfur content for number 4 fuel oil. Carbon burnout analysis indicates that all fuels can achieve high carbon conversion efficiency (>99%) at the best operating conditions. The bio-oil blend has the highest amount of unburned carbon, of which the majority is in the form of gaseous CO.

Vapor-phase sorption of hexachlorobenzene on typical municipal solid waste (MSW) incineration fly ashes, clay minerals and activated carbon

Column sorption experiments were conducted at 330 °C and 250 °C to study the vapor-phase sorption of hexachlorobenzene (HCB) on two kinds of municipal solid waste (MSW) incinerator fly ashes, kaolinite, montmorillonite and activated carbon (AC). Both Freundlich equation and linear equation well fitted the sorption isotherms of HCB vapor on fly ashes and clay minerals at 330 °C ( r 2 > 0.87), while the sorption isotherm of HCB vapor on AC at 330 °C was in the shape of Brunauer type-II adsorption. Catalytic dechlorination of HCB was found to occur on the surface of fly ashes, and pentachlorobenzene was the only dechlorination product detected in the effluent gas. Increasing temperature decreased the sorption of HCB vapor on fly ashes, and promoted the catalytic dechlorination of HCB. On the assumption that the organic carbon and clay minerals in fly ash were derived from AC, kaolinite and montmorillonite, the relative contributions of these components to the apparent sorption capacity of fly ashes at 330 °C were estimated. It was found that very small percentage of AC contributed the most to the apparent sorption of HCB vapor on fly ash. The sorption coefficient of HCB on montmorillonite at 250 °C was 37 times higher than that at 330 °C, suggesting montmorillonite could be a kind of low-cost sorbent to effectively reduce the emission of vapor-phase organochlorine compounds from MSW incinerators.