Collected Fly Ash Research Articles

Estimating CO2 emission from fly ash and bottom ash collection and transport from thermal waste processing in Jakarta

Abstract Municipal solid waste poses a significant challenge in DKI Jakarta Province. This study assumes that DKI Jakarta has distributed waste treatment facilities (ITFs) covering western, eastern, and southern service areas, employing thermal waste systems due to their efficiency in handling large waste volumes. However, its residual waste, Fly Ash and Bottom Ash (FABA), presents its own concerns. FABA accounts for 1.5% and 18.5% of the total waste volume in all ITFs, equivalent to 88.47 tons of fly ash and 1,091.07 tons of bottom ash daily. The study analyses total distance travelled and fuel consumption for FABA transportation from each ITF to designated disposal sites. The planned fleet is 12-ton capacity truck or equivalent. Arc-GIS is employed for trip assignment and generate daily trip requirements. Three FABA disposal scenarios are considered: TPST Bantargebang, certified third-party sites in Gunung Putri, and a combination of both. The daily total distance ranges from 8,247.96 to 10,026.48 km and consume 5,071.16 to 6,164.66 Liters of biosolar. The trip assignment reveals that the distance to Gunung Putri exceeds the other alternatives, while transporting FABA to TPST Bantargebang yields the lowest total distance travelled. Estimated CO2 emissions range from 11.22 to 13.64 tons per day.

Measurement of radon exhalation rate and radiation doses in fly ash samples.

Coal based thermal power plants contribute about ~ 72% of the power generation in India. Indian coal is of bituminous type, having a high ash content with 55-60% ash. Due to considerable environmental importance the collected fly ash has become a subject of worldwide interest in recent years. In the present study radon exhalation rate and the activity concentration of 226Ra, 232Th and 40K radionuclides in fly ash samples from Kasimpur Thermal Power Plant, Aligarh, Uttar Pradesh, India have been measured by 'Sealed Can technique' using LR-115 type II detectors and a low-level NaI (Tl)- based gamma-ray spectrometer, respectively. Radon exhalation rate has been found to vary from 57.1±5.3 to 119.4±7.7 mBq m-2h-1 with an average value of 87.3±5.8 mBq m-2h-1. Activity concentration of 226Ra ranged from 20.0±8.5 to 30.0±9.7Bqkg-1 with an average value 23.4±9.0Bqkg-1, 232Th ranged from 17.0±9.9 to 69.0±13.8Bqkg-1 with an average value of 46.5±12.1Bqkg-1 and 40K ranged from 130.0±7.2 to 332.0±11.1Bqkg-1 with an average value of 177.0±8.1Bqkg-1.

Insight into heavy metal chemical fractions in ash collected from municipal and industrial waste incinerators in northern Vietnam.

This investigation involved the collection of fly ash and bottom ash specimens from seven waste incinerators situated in the northern provinces of Vietnam, aimed at assessing the composition and distribution patterns of five chemical fractions of heavy metals (Pb, Cr, As, Cd Cu, and Zn) present in incinerator waste ash. The outcomes reveal that fly ash exhibited a relatively elevated concentration of industrial waste metals (25-66%) such as As, Cd, and Pb primarily in exchangeable (F1) and carbonate fractions (F2), which are mobile forms susceptible to environmental dissolution and consequential bioaccumulation posing health risks to humans. The predominant states of the metals Cr, Cu, and Zn were identified as residual, Fe-Mn oxide, and carbonate, respectively, with their relative proportions showing minimal variation. Conversely, heavy metals were predominantly present in residual residue and Fe-Mn bound form (F3) in bottom ash derived from both residential and commercial waste incineration operations. The non-carcinogenic hazard indices (HI) associated with the examined metals, ranked for both adults and children, were as follows: Pb > Cr > As > Cd > Cu > Zn. Notably, the HI values for Pb, Cr, and As exceeded the permissible threshold (HI > 1) for children. However, the risk of As, Cd, and Pb-related cancer via exposure pathways remained within acceptable limits for both age groups. Conversely, the probability of carcinogenic effects attributable to Cr surpassed the permissible threshold (>10-4), indicating significant health concerns associated with heavy metals in waste incinerators for humans, particularly children.

Coupling of alkaline and mechanical modified fly ash for HCl and SO2 removal in the municipal solid waste incineration plant

In this study, fly ash was modified by ball milling through coupling alkaline and mechanical to achieve the reuse of fly ash. The adsorption capacity of fly ash for acidic gases was improved in experiments using simple ball milling. Under the optimal ball milling conditions with coupled NaOH, the desulfurization efficiency can reach 100% and the dechlorination efficiency can be maintained above 90% for the first 100 s of the experiment. Different characterizations show that the ball milling process increases the specific surface area of fly ash, which makes NaOH adhere uniformly to the surface of fly ash particles in an amorphous structure and improves the adsorption effect of the fly ash on acid gases. In addition, experiments with different gas parameters proved that increased temperature, increase of the flue gas flow rate, and increase of the acidic gas concentration in flue gas all lead to the decrease of the modified fly ash’s deacidification efficiency. This provides a reference for engineering applications of modified fly ash under different working conditions. In summary, a comprehensive technical route of “fly ash collection - online modification - timely injection” is proposed in the municipal solid waste incineration (MSWI) plant.

Specifics of Electrostatic Precipitation of Fly Ash from Small-Scale Fossil Fuel Combustion

This paper investigates the removal efficiency of a honeycomb electrostatic precipitator (ESP) applied to control particulate matter (PM) emissions from a small-scale boiler with combustion lignite and hard coal. The specifics of the precipitation of emissions from small-scale boilers are discussed, and the design principles for relevant ESPs are presented and used. The ion-induced nucleation of sulfuric acid occurred, causing the drastic penetration of 19 nm particles through the ESP. Despite this, the overall collection efficiency was sufficient to meet the EU’s Ecodesign Directive requirements. Back corona was not detected. The optimal ESP performance is defined with further parameters: a current density of 0.5 mA/m2 at an electric field strength of about 2.7 × 105 V/m; a minimal specific collecting area of ESP (SCA) of 60 m2/(m3/s); and Nt-product of 4.5 × 1014 s/m3. Such parameters of ESPs should ensure adequate PM emissions control for any type of boiler with similar emissions characteristics. The composition of collected fly ash particles was analysed, and a method for fly ash utilisation was proposed. This research may be helpful for designing ESPs to control PM emissions for small-scale units with fossil fuel combustion.

Coal Feed-Dependent Variation in Fly Ash Chemistry in a Single Pulverized-Combustion Unit

Four suites of fly ash, all generated at the same power plant, were selected for the study of the distribution of rare earth elements (REE). The fly ashes represented two runs of single-seam/single-mine coals and two runs of run-of-mine coals representing several coal seams from several mines. Plots of the upper continental crust-normalized REE, other parameters derived from the normalization, and the principal components analysis of the derived REE parameters (including the sum of the lanthanides plus yttrium and the ratio of the light to heavy REE) all demonstrated that the relatively rare earth-rich Fire Clay coal-derived fly ashes have a different REE distribution, with a greater concentration of REE with a relative dominance of the heavy REE, than the other fly ashes. Particularly with the Fire Clay coal-derived fly ashes, there is a systematic partitioning of the overall amount and distribution of the REE in the passage from the mechanical fly ash collection through to the last row of the electrostatic precipitator hoppers.

Composition and properties of fly ash collected from a multifuel fluidized bed boiler co-firing refuse derived fuel (RDF) and hard coal

In Poland, Refuse Derived Fuel (RDF) potential is significant, but high heterogeneity and contamination of the fuel limit its direct use in power industry. In this work samples were collected from a real-scale multifuel unit co-firing RDF with hard coal. Fuel samples and fly ashes collected from secondary cyclone and from bag filter were analysed in details. The thermal behaviour of fly ashes was investigated using X-ray diffraction (XRD), simultaneous thermal analysis (STA) and high-temperature microscope. High content of calcium compounds in both ash samples was noted. To determine the influence of flue gas treatment installation on the ash morphology and composition, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) was used. Fly ash after flue gas treatment (FGT) system was much finer and higher content of heavy metals was observed. The mass distribution of mercury and leachability of selected heavy metals from the fly ashes were performed for the analysed unit. The concentration of mercury was several times higher in case of first collected fly ash due to longer contact time of flue gases with ash. Fly ashes contained high amounts of copper, lead and vanadium, but leachability of analysed metals was lower in case of bag filter ash.

Separating Al2O3 particles from high-speed flue gas by an induced flow recirculation in two-stage electrostatic precipitator

Although fly ash is known to be harmful to human health, fly ash is full of metals and compounds that are useful in certain applications. Aluminum oxide is one of the economic compounds in fly ash emitted from coal-fired power plants where electrostatic precipitators (ESPs) are commonly used to collect fly ash. The collection efficiency of an ESP decreases rapidly when the passing airflow velocity increases and could get even worse because of particle reentrainment when rapping the collecting electrode for cleaning purposes. This paper presents how the flow recirculation, induced by square-wave structure, prevents the collection efficiency from dropping too fast by suppressing particle reentrainment. The results show that the ESP comes with the square-wave collecting electrode (ESP-SW) has higher collection efficiency than that comes with the traditional flat-plate collecting electrode (ESP-FP), and the difference gets larger when the airflow velocity increases. The particle reentrainment rate of the ESP-SW is up to 22% lower than that of the ESP-FP. Furthermore, when the airflow velocity goes higher, the square-wave collecting electrode collects more and more percentage of particles, while the flat-plate collecting electrode collects a fewer and fewer percentage of particles.

Characteristics of Fly Ash under Oxy-Fuel Circulating Fluidized Bed Combustion

The objective of the present paper is to study the physiochemical properties of fly ash under oxy-fuel circulating fluidized bed (CFB) combustion mode. Tests were conducted in a 50 kW oxy-fuel CFB combustor under both air and oxy-fuel combustion. The analyses of the collected fly ash samples included particle size analysis, N₂ adsorption analysis, char carbon, inductively coupled plasma optical emission spectrometry (ICP-OES) , and X-ray diffraction (XRD). It was found that the d₁₀, d₅₀, and d₉₀ of fly ash under oxy-fuel combustion mode were larger than that under air combustion mode and increased with the rise of the inlet oxygen concentration. The Brunauer–Emmett–Teller (BET) surface area, pore volume, and pore size of fly ash under air combustion are almost the same with that at inlet oxygen concentration of 30%. The element mass concentrations were obviously different between the two combustion modes, but the main mineral phase was insignificantly different. Moreover, the inlet oxygen concentration has no significant effect on the element mass distribution in the fly ash, except for the alkaline earth metal under oxy-fuel combustion.

Fly ash classification efficiency of electrostatic precipitators in fluidized bed combustion of peat, wood, and forest residues

The increasing use of biomasses in the production of electricity and heat results in an increased amount of burning residue, fly ash which disposal is becoming more and more restricted and expensive. Therefore, there is a great interest in utilizing fly ashes instead of just disposing of it. This study aimed to establish whether the utilization of fly ash from the fluidized bed combustion of peat, wood, and forest residues can be improved by electrostatic precipitator separation of sulfate, chloride, and some detrimental metals. Classification selectivity calculations of electrostatic precipitators for three different fuel mixtures from two different power plants were performed by using Nelson's and Karnis's selectivity indices. Results showed that all fly ashes behaved similarly in the electrostatic separation process SiO2 resulted in coarse fractions with Nelson's selectivity of 0.2 or more, while sulfate, chloride, and the studied detrimental metals (arsenic, cadmium, and lead) enriched into fine fractions with varying selectivity from 0.2 to 0.65. Overall, the results of this study suggest that it is possible to improve the utilization potential of fly ashes from fluidized bed combustion in concrete, fertilizer, and earth construction applications by using electrostatic precipitators for the fractionating of fly ashes in addition to their initial function of collecting fly ash particles from flue gases. The separation of the finer fractions (ESP 2 and 3) from ESP 1 field fly ash is recommended.

Impact of coal source changes on mercury content in fly ash: Examples from a Kentucky power plant

Mercury capture by coal combustion fly ash is a function of the chemistry of the feed coal, including halogens; the amount and type of carbon in the fly ash; and the type of fly ash collection and the flue gas temperature at the point of fly ash collection. In this study of fly ash collected at different points in time from a five-row electrostatic precipitator (ESP) system at a Kentucky power plant, relationships were seen between the amount of fly ash carbon and the concentration of Hg in the ash. Coincident with the burning of low-S coal at two collection times, a better correlation between Hg and C was seen in the relatively cooler 3rd and 4th ESP rows than in the first two rows. This was particularly evident in the 2007 collection where the fly ash carbon was higher than in the 2004 collection. In 2013, following the installation of flue-gas desulfurization and the resulting switch to high-S coal and the installation of a hydrated-lime injection system between the 2nd and 3rd ESP rows, no significant Hg vs. C trend was observed.

Characterization of the flowability of fly ashes from grate-fired combustion of forest residues

Data about the flowability of fly ashes are important for the design of hoppers of fly ash collection equipment and fly ash storage silos. Fly ashes from sixteen grate-fired combustion plants (first-stage and second-stage de-dusting fly ash) were examined for flow relevant properties. The flowability category of the coarser first-stage fly ashes was cohesive to easy-flowing, while for the second-stage fly ashes the flowability category was very cohesive to cohesive. A good correlation was found between the flowability of the fly ashes and the mass median diameter of their particle size distribution. The correlation of the flowability with the bulk density or with the angle of repose was less significant. No correlation was found with the other parameters investigated. Moreover, the effective angle of internal friction, the wall friction angle and bulk density can be expressed as a function of the mass median diameter. Thus, the particle size is the most important parameter for the flowability of the fly ashes.

Simulation of fly ash particulates separation in cyclone separator

The response surface Box-Behnken design is used to study the dependence and interactions of particle size, load of fly ash and pressure drop inside the cyclone separator for collection efficiency of fly ash. The maximum collection efficiency of fly ash obtained was 95% in the cyclone separator studied. The Barth model is used to evaluate the axial and tangential velocities of cyclone separator studied. The static pressure contour plots at different inlet velocities of 41 m/s and 104 m/s at top and bottom horizontal planes of cyclone separator were developed using computational fluid dynamics software Fluent. The contour regions of axial, radial and tangential velocity fields in the cyclone separator were analysed using Fluent finite volume code for flow analysis inside the cyclone separator for fly ash collection. It was observed that the radial velocity increases rapidly towards the vortex core and the tangential velocity is dependent on the geometrical design of cyclone separator, wall friction and particle loading of fly ash.

Powder Resistivity Inferred Differential Collection of Heterogeneous Coal Fly Ash and Powered Activated Carbon Admixtures Within a Cylindrical Electrostatic Precipitator

One of the primary goals of U.S. EPA’s Mercury Air Toxics Standards (MATS) is to remove approximately 90 % of mercury emissions from coal-fired power plants (CFPPs). Sorbent injection upstream of electrostatic precipitators (ESPs) has been the leading method for capturing mercury at CFPPs. However, electrostatic precipitators (ESPs) that are marginally sized and/or operated may face new performance challenges due to sorbent injection. Injected mercury sorbent particles having different properties (i.e., particle size, surface chemistry, or electrical properties), mixing with native fly ash, can potentially affect the collection behaviors of ESPs. The present study uses powder resistivity to study the differential collection behaviors within a cylindrical ESP by manually feeding admixtures containing Norit DarcoⓇ FGD powdered activated carbon (PAC) and fly ash samples from either Powder River Basin (PRB) or Illinois bituminous coals. Powder resistivity measurements, performed on fly ash admixtures at various PAC ratios (i.e. 0−10 wt. %) prior to ESP processing, serve as the initial resistivity data to infer the impact of PAC injection on ESP collection by comparing to powder resistivity of samples collected from the collection electrode. This study presents not only the evidence of differential collection behaviors within an ESP but also the implications for mercury emissions and the particulate matter (PM) control through ESPs.

Effect of powdered activated carbon on the air void characteristics of concrete containing fly ash

Abstract One of the common methods to reduce mercury vapor emissions from coal-fired power plants involves the injection of powdered activated carbon (PAC) into the flue gases to adsorb the mercury vapor. If the PAC then settles along with the fly ash in the electrostatic precipitator, the ability to use the collected fly ash as a supplementary cementitious admixture in concrete must be established. This study examined the influence of PAC in fly ash on the air void networks and consequent properties of concrete produced with an air entraining admixture. Samples included those with PAC added to the fly ash at the laboratory as well as PAC-containing fly ash collected at a generating station. The air void content, specific surface area and spacing factor of hardened concrete were determined using an image analysis technique on epoxy-impregnated and ink-prepared samples. The PAC-containing fly ash had an insignificant effect on the air void content and spacing factor compared to samples with laboratory-added PAC. Image analysis using ink-prepared samples provided improved reliability of the air void network results compared to epoxy-prepared samples.

Levels and environmental impact of PAHs and trace element in fly ash from a miscellaneous solid waste by rotary kiln incinerator, China

The increase disposals of fly ash from solid waste incinerator have becoming a serious environmental problem in China. Levels of PAHs in fly ash from a selected full-scale miscellaneous solid waste incinerator were determined by gas chromatograph/mass spectrometer. Content of trace elements and other major elements of fly ash were studied by inductively coupled plasma-mass spectrometry and X-ray fluorescence spectrometry, respectively. Experimental results showed that a high content of lead occurred in the collected fly ash samples with the value of 35,037.90 µg/kg, but lower contents of total 16 PAHs, which mainly smaller PAHs. This was different from previous studies regarding the levels of PAHs in fly ash collected from the similar hospital waste incinerators. This survey indicated that the emission factors are attributed to combustion temperatures, type of incinerator, and the occurrences of elements in solid wastes. The total toxic equivalent quantities (TEQ) value of PAHs, a potential toxicity risk assessment using index TEQ model, has been reached to 4.00 µg/kg in ash from this study, but may not suitable for the soil amendment. Therefore, a further treatment of discharged ash and assessment of its environmental risk are unavoidable.

Numerical and experimental evaluation of fly ash collection efficiency in electrostatic precipitators

This paper evaluates experimentally and numerically the influence of different geometrical and operating parameters of a single stage wire-duct electrostatic precipitators (WDEP) on its fly ash collection efficiency. The governing equations are solved under dust loading conditions using the finite element method (FEM) and a modified method of characteristics (MMC). In addition, a proto-type design that represents a WDEP was successfully designed and fabricated at the research institute of KFUPM (RI-KFUPM). The experiments were carried out under laboratory conditions where the WDEP was made of Plexiglas with a length of 2m, height of 1m, wire-to-collecting plate spacing of 0.2–0.3m, and an inter-electrode (wire-to-wire) spacing of 0.16–0.21m. Smoke of fired coal was used as a source of seed particles of PM10 category (with 75–80% of particles lying below 10μm). An indication of the effectiveness of the numerical approach was carried out through a comparison of computed results as well as presently and previously obtained experimental data.

Influence of Chemical Composition on the Electrical Resistivity of Fly Ash Generated from Indian Coal Based Thermal Power Plants

Electrostatic Precipitators (ESP) are control devices widely used for collection of fly ash in Indian coal based thermal power plants. The design, performance, sizing, collection and operation of ESP depend largely on the properties and quality of the coal burned and the fly ash generated in the boilers. This study presents the influence of fly ash composition on the resistivity of Indian fly ash generated from coal based power plants, which is one of the critical parameter required to make accurate predictions of ESP in terms of their collection efficiency. The fly ash electrical resistivity measurements were conducted over a wide range of temperature in both ascending and descending cycles in the range of 90 to 455oC at 9% moisture as per IEEE-Standard 548 (1991). The earlier developed Empirical relations used for calculating fly ash electrical resistivity for western coals were modified for the calculations of electrical resistivity of Indian fly ashes and new empirical relations have been developed based on experimental results and chemical composition of fly ash samples collected from different coal based power plants in India which have different chemical composition in comparison to western coals. Results in the newly developed correlations show better agreements with experimentally determined resistivity compared to those developed by Bickelhaupt and others.

Trace elemental characterization of fly ash

The purpose of this study was to determine heavy metal concentrations in ash samples taken from the filter of the gas cleaning system of biomass incinerators in Austria. Knowing the concentrations of heavy metals is important for the decision of further treatment or utilization of the ashes. The heavy metals contained in the ashes remain in the bottom ash of the incinerator or leave the incinerator with the off-gas and are collected in the off-gas filter. The amount of the metals in the collected fly ash depends on the composition of the input material. The aim of this study was to examine this influence and compare the results with literature data. For measurement, the fly ash samples were at first dissolved in a microwave digestion unit using nitric acid and hydrochloric acid. Afterwards, 20 metals were analyzed by inductively coupled plasma optical emission spectrometry. Al, Fe, Mg, Mn, and Zn were found in higher concentrations in the fly ash samples. The enrichment factor between the concentrations in the fly ash and the concentrations in the input material was on average in the range of 18.

Effect of the existing air pollutant control devices on mercury emission in coal-fired power plants

Ontario-Hydro method (OHM) and semi-continuous mercury emission (SCEM) were used to study the effects of the existing air pollutant control devices on mercury emission in coal-fired power plants. The results indicate that more than 50% of Hg 0 is oxidized into Hg 2+ by selective catalytic (V 2O 5/TiO 2) reduction (SCR), but SCR itself couldn't control mercury emission. The collection of fly ash by electrostatic precipitator (ESP) directly lowers the proportion of particle mercury in the flue gas. For water soluble Hg 2+, wet flue gas desulphurization (FGD) could control mercury emission by absorbing Hg 2+ in flue gas. Most of Hg 2+ is reduced into Hg 0 by reacting with SO 3 2– and HSO 3 − in FGD slurry, which results in the decrease in mercury control efficiency. At the same time, it leads to the secondary emission of mercury, and it is more serious when SCR is in service.