Furnace Bottom Ash Research Articles

Integrated Use of Furnace Bottom Ash as Fine Aggregate and Cement Replacement for Sustainable Mortar Production.

Recycling fly ash (FA) and furnace bottom ash (FBA) help with reducing greenhouse gas emissions, conserving natural resources, and minimizing waste accumulation. However, research on recycling FBA is progressing more slowly compared to FA. This research aims to investigate the combined use of FBA as a replacement for both fine aggregate and cement and its influence on the performance of mortar. The findings indicated that incorporating 25% FBA as a fine aggregate replacement and 10% or 20% ground FBA (GFBA) as a cement replacement significantly enhanced compressive strength after 28 and 56 days. Flexural strength was comparable to control mortar at 28 days and superior at 56 days. However, increasing the FBA content beyond 25% as a fine aggregate replacement reduced workability and increased porosity, which negatively affected mechanical performance and water absorption. Microstructural analyses revealed denser and more compact structures in the mortar with combined FBA replacement for both fine aggregate and cement, specifically 25% as a fine aggregate replacement and 10% and 20% as cement replacements. Optimal performance was noted in mixtures with Ca/Si and Ca/Al ratios within the ranges of 1.8-1.5 and 0.24-0.19, respectively. Trace element leaching analysis has not shown significant differences between GFBA, FA, and OPC. Regarding environmental impact assessment, using FBA as a fine aggregate replacement did not show a significant reduction in CO2 emissions, but replacing cement with FBA reduced emissions remarkably. Generally, using FBA as a replacement for both fine aggregate and cement in mortar enhances compressive and flexural strengths at optimal levels, promotes sustainability by reducing landfill waste and CO2 emissions, and supports cleaner production practices despite some workability challenges.

Co-grinding treatment for developing integrated-properties SCMs from basic oxygen furnace slag and furnace bottom ash: A step toward synthesis advanced SCMs

The recycling of the basic oxygen furnace slag (BOF) and the furnace bottom ash (FBA) as supplementary cementitious materials (SCMs) will contribute to achieving the sustainability requirements of the infrastructure sector. The BOF possesses inherent hydraulic properties due to its high content of glass network-modifying phases (e.g., CaO, MgO, Na2O, and K2O). However, its poor grindability, variability in quality, and purity are factors that may limit its reuse as a SCM. This paper aims to explore the impact of co-grinding BOF with FBA on the chemical, physical, and microscopic properties of the new combinations and their effect on the performance of their designed mortar. Combinations consisting of three ratios of BOF to FBA (3:1, 3:2, and 1:1) were synthesized, and the results of the co-grinding were compared with those equivalents in separate grinding. The findings indicate that co-grinding improved the fineness and synergies of the BOF-FBA particles without significantly altering the crystalline phases or developing new ones compared to the original materials. Combined grinding had a positive effect on the flowability of mortar mixtures and the development of compressive strength at all curing ages. Microstructural analyses revealed denser and more compact microstructures in mortar designed from the co-ground BOF-FBA combinations, along with lower Ca/Si and Si/Al ratios, indicating the positive influence of co-grinding on the growth of hydrates.

Comparative assessment of the effects of furnace bottom ash and fly ash on mortar performance

Comparative assessment of the effects of furnace bottom ash and fly ash on mortar performance

Novel Thermal and Microscopic Techniques To Determine the Causes of Suboptimal Combustion Performance at Colombian Stoker Furnaces.

This study presents the application of a novel approach, using thermal and optical techniques, to identify the causes of poor burnout performance of Colombian stoker furnaces in the Cauca Valley State. The four coals used in these furnaces were characterized to obtain particle size distribution, particle and tapped density, elemental and proximate composition, mineral composition, and maceral content. Up to 80% incomplete combustion was noted in macro-TGA tests compared to complete combustion in a micro-TGA. Reflectance and intrinsic reactivity measurements were for chars prepared in three different particle sizes (<6, 6–19, and 19 mm), three temperatures (700, 900, and 1050 °C), and three residence times (10, 30, and 120 min). Two of the coals produced char samples with reflectance values above 6%, which matched those seen in the stoker, indicating that the furnace temperature was not the cause of poor combustion and that only two of the four coals were likely to be present in the furnace bottom ash. These tests were also able to prove that oxygen diffusion limitation was the root cause of the poor burnout where the carbon inside the furnace bottom ash was shielded from oxygen ingress through the formation of a nonpermeable slag layer. Thus, this study demonstrates the potential of both thermal profiling and optical reflectance as a tool for forensically evaluating the thermal history and operational performance of furnaces.

Phosphate removal from wastewater by furnace bottom ash

Orthophosphate is a natural chemical found in large quantities in the Earth's crust, and its inclusion in water causes eutrophication. As a result, several experiments have been conducted to investigate the potential of various treatment systems to remove phosphate from wastewater. According to recent research, filtration methods are useful for phosphate removal, with one drawback being the expensive cost of the filtration materials. Therefore, new research has focused on reducing the cost of filtration method using cheap replacements. The current research focuses on the efficacy of using iron industry wastes which the blast furnace bottom ashes to remove phosphates from contaminated wastewater. Some operating conditions, like and phosphate level, treating periods and blast furnace bottom ashes dosages, have investigated in order to find a suitable set for achieving the highest probable removal rate at a fair charge. The findings showed that the bottom ashes are an effective phosphate removal substitute. The highest removal of phosphate was 91.2% at 37.5 minutes treatment period, using initial concertation of 5 ppm, and a dose of the bottom ashes of 575 ppm. The findings have been used to build a production model with a high level of reliability.

Reusing of furnace bottom ash as an adsorbent for phosphate removal from water

Phosphate is a common chemical element that resides extensively in the Earth’s crust, and its presence in water results in eutrophication of water. Therefore, many studies were devoted to study the ability of phosphate removal from water and wastewater using different treatment methods. Recent studies have suggested that filtration treatment techniques are effective for phosphate removal with one disadvantage which is the high cost of industrial filtration materials used. As a result, recent studies are concentrating on minimizing the operational costs of the filtration method by using cost-effective alternatives. This study is focusing on the efficiency of using the wastes of the iron industry (furnaces bottom ashes (FBAs)) for phosphates elimination from synthetic water. Several operational conditions which are detention times, FBAs doses, and phosphate concentrations, were studied to obtain the best conditions which ensure the best possible removal rate and a reasonable operational cost. The results indicated that FBAs are an efficient alternative for phosphate removal with an optimum removal rate of 88.9% with 31 min retention time, phosphate concentration of 5 mg/L, and 550 mg/L FBAs doses. The results obtained were used to construct a model with high reliability at R2 = 0.967.

Production of foamed glass-ceramics using furnace bottom ash and glass

This research has produced foamed glass-ceramics from coal fired power station furnace bottom ash (FBA) and soda-lime-silica glass. The as-received FBA was wet milled with different additions of glass. The resultant slurry was dried and formed into a powder. The powder was pressed and sintered at a range of temperatures with additions of a fluxing agent (sodium tetraborate decahydrate), a bubble stabilising additive (tri-sodium phosphate) and a bloating agent (calcium carbonate) and this produced foamed FBA-glass-ceramics. The effect of glass content and sintering temperature on the properties of the sintered ceramic foams are reported. A range of potential applications including thermal insulation and biological filters for water and wastewater treatment are discussed. The research demonstrates that it is possible to engineer the properties of FBA derived glass-ceramic foams by careful control of the composition and processing conditions in order to transform a problematic waste into commercially interesting materials.

PERFORMANCE INVESTIGATION OF FURNACE BOTTOM ASH AS A FILTER MEDIA FOR PHOSPHATE REMOVAL

This study investigates the capability of furnace bottom ash (FBA) as a filter media for phosphorus removal from wastewater effluents. Lab-scale studies were conducted, in which a mass of FBA was brought into contact with the phosphate solution (a predominant form of phosphorus in wastewater) in batch experiments and lab-scale filter. Intraparticle Diffusion Model (IPD) was applied and revealed that the mechanism of phosphate adsorption onto FBA consist of three phases; film phase occurred in the external surface and intraparticle diffusion phases take place in the wide pores and microspores. A Point Zero Charge (PZC) study was conducted and indicated that the FBA acts as anion exchanger and develops negative charge when the pH more than 9. Based on the PZC outcomes the FBA efficiency was regenerated by two washing methods (continuous and intermittent) with deionized water solution at pH 9.5 and 10. The intermittent washing method gave better results as the FBA regenerate 95% of its efficiency. FBA was achieved the phosphate permissible limit (0.1 mg/L) in synthetic solution at 150 min. While, in real wastewater sample was achieved it in 180 min. The FBA washing method based on PZC can be adopted as a strategy for absorbents efficiency regeneration and phosphorus recovery.

The Effect of Different Concrete Designs on the Life-Cycle Assessment of the Environmental Impacts of Concretes Containing Furnace Bottom-Ash Instead of Sand

The results of life-cycle assessments (LCAs) of concrete are highly dependent on the concrete design method. In this study, LCAs were conducted to evaluate the environmental impacts of the replacement of sand with furnace bottom-ash (FBA) in concrete. In the FBA-based concretes, sand was replaced with FBA at proportions of 0, 30, 50, 70, and 100 wt%. Two design methods were studied: (i) concrete with fixed slump ranges of 0–10 mm (CON-fix-SLUMP-0-10) and 30–60 mm (CON-fix-SLUMP-30-60); and (ii) concrete with fixed water/cement (W/C) ratios of 0.45 (CON-fix-W/C-0.45) and 0.55 (CON-fix-W/C-0.55). The ReCiPe2016 midpoint and single-score (six methodological options) methods were used to compare the environmental damage caused by the FBA-based concretes. A two-stage nested (hierarchical) analysis of variance (ANOVA) was used to simultaneously evaluate the results of six ReCiPe2016 methodologies. The ReCiPe2016 results indicate that replacing sand with FBA decreased the environmental impact of the concretes with fixed slump ranges and increased the environmental impact of the concretes with fixed W/C ratios. Therefore, using FBA as a partial sand replacement in concrete production is of debatable utility, as its impact highly depends on the concrete design method used.

Fuel flexible power stations: Utilisation of ash co-products as additives for NOx emissions control

This work investigated the effects of different ash co-products on the combustion of solid fuels, in particular the fuel-nitrogen behaviour: The fuel-ash additive combinations investigated were: Firstly, biomass ashes added to bituminous coals, representative of those used in power stations; Secondly, a low reactivity coal; Thirdly, a high-N biomass (olive cake) was chosen as a high reactivity fuel and studied with a power-station pulverised coal fly ash as an additive. These five solid fuels have a wide fuel ratio, FR (i.e. the ratio of fixed carbon to volatile matter content). The ash additives were a pulverised fly ash (PFA) and a furnace bottom ash (FBA) from wood pellet combustion in a UK power station. Fuels (with and without additives) were studied for nitrogen partitioning during (i) devolatilisation and for (ii) NOx formation during combustion, using two different electrically heated drop tube furnaces (DTF) operating at 1373 K. Devolatilisation was also studied via ballistic-heated thermogravimetric analysis (TGA). The extent of impact of additives on volatile yield under devolatilisation conditions was dependent on fuel ratio, high FR has the greatest increase in volatile release when co-feeding the additive. Under devolatilisation conditions, there is a correlation between volatile nitrogen and carbon conversion for all the fuels tested. Thus, additives liberate more volatile-nitrogen from the coals and also deliver enhanced carbon conversion. A mechanism is proposed whereby ultra-fine particles and vapours of reactive compounds from the additives interact with the reacting fuel/char particle and influence N-release during both devolatilisation and char burn-out. The enhanced conversion of fuel-nitrogen to volatile-nitrogen and the reduction of char-nitrogen can lead to reductions of NOx emissions in emissions-controlled furnaces. This approach could assist fuel-flexible power stations in achieving their NOx emission targets.

A Novel Coating Method for Create Filter Media Capable to Remove Phosphate from Wastewater Effectively

Filtration materials coating with metallic oxides represented a good method for phosphate sorption. However, most of the researchers utilize chemicals as a source of metallic oxides and heating process to set the chemicals over the filtration materials. This study is aimed to introduce the furnace bottom ash FBA as a source of metallic oxides; it is available free because it is dumped as a waste material from power generation plants. The method of creating new filter media involves coating the limestone and sand by FBA, and the ordinary Portland cement OPC utilized as binder to binding the mixture materials. The water is the factor which is responsible for activating the OPC. All factors such as mixed materials ratio, water content and age of reaction have subjected to optimization process. The results revealed that the optimal mixture for phosphate removal consists of 40% FBA, 5% OPC from dry weight of supporting material, 35% water ratio from the total weight of FBA and OPC, and 14 days are enough to complete the materials reaction. Limestone-furnace bottom ash LFBA indicated high capacity for phosphate sorption and possibility of efficiency regenerate. This study demonstrates a new method for coating the filtration materials more convenient with sustainability approach.

Effects of low-alkalinity binders on stabilization/solidification of geogenic As-containing soils: Spectroscopic investigation and leaching tests

The low-alkalinity stabilization/solidification (S/S) treatment of the soil containing high concentrations of geogenic As by physical encapsulation is considered as a proper management before land development; however, the choice of an effective binder and the leaching potential of As remain uncertain. In this study, the influence of S/S binders (cement blended with fuel ash (FA), furnace bottom ash (FBA), or ground granulated blast furnace slag (GGBS)) on the speciation and leaching characteristics of geogenic As was studied. The results of X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) showed the reduced amount of calcium silicate hydrate phase and the decrease in oxidation state of As(V)-O on the surface of Fe(III) oxides/hydroxides in the low-alkalinity S/S treated soils. This might be due to the binder incorporation and change in pH conditions, which slightly affected the As-Fe interaction and increased the non-specifically sorbed species of As. Therefore, the S/S treatment increased the leachability and bioaccessibility of geogenic As to varying degree but decreased the phyto-extractable As. The S/S treatment by cement incorporating 25% of class C fly ash (O4C1) could achieve comparable or better performance, while reducing the risk assessment code (RAC) to a greater extent compared to that of using cement only. This study illustrates the effectiveness and limitations of low-alkalinity binders (e.g., O4C1) for geogenic As immobilization and encapsulation, which provides a new insight for determining the appropriate S/S binder in soil remediation.

Sound insulation properties of rubberized lightweight aggregate concrete

This study aimed to develop an effective surface pre-treatment method for recycled rubber particles to improve the sound insulation properties of rubberized lightweight aggregate concrete. In this study, the control lightweight aggregate concrete mixture was prepared using lightweight expand clay aggregate as the coarse aggregate and furnace bottom ash (FBA) as the fine aggregate. The results showed that when all the FBA was replaced by the recycled rubber aggregate, the overall sound reduction level was 32.5 dB (A), which was already significantly higher than the 15.5 dB (A) achieved by the control concrete mixture prepared without rubber aggregates. A simple cement slurry coating pre-treatment method was developed to modify the surface of the recycled rubber aggregate. 10.9 dB (A) and 14.8 dB (A) further noise reduction were achieved when FBA was replaced by 50% and 75% of the pre-treated rubber aggregates, respectively. The dynamic Young's Modulus of the concrete mixtures was tested and the surface bonding of the concrete mixtures prepared with the pre-treated/un-treated rubber aggregate was also investigated. The results suggested that the pre-treatment method resulted in weaker bonding between the rubber aggregates and the cement paste, and thus increased the vibration absorption capacity and enhanced the noise insulation properties of the concrete.

Production of ceramics from coal furnace bottom ash

Furnace bottom ash (FBA) is generated in significant quantities from coal fired power stations and is a problem when commercially viable reuse applications do not exist locally. Representative samples of FBA from the Kilroot power station in Northern Ireland have been milled, pressed and sintered at a range of temperatures to form new ceramic materials. The effect of adding recycled glass to the mix has been investigated. The optimum FBA ceramics were produced by sintering at 960°C and these had a density of 2.388g/cm3, zero water adsorption indicating minimal open porosity, and a Vickers hardness comparable to commercially available glass-ceramics. The addition of 20% by weight of glass reduced shrinkage during sintering, while the samples maintained high density and hardness. This glass addition allows greater dimensional control during sintering to form FBA ceramic tiles. The research demonstrates that FBA can be processed into ceramics for use in higher value products compared to conventional use as lightweight aggregate. Further research is required to optimize processing and fully characterize material properties. This novel approach to managing FBA has potential to transform a problematic waste in Northern Ireland into a valuable resource.

Dynamic leaching behavior of geogenic As in soils after cement-based stabilization/solidification.

Cement-based stabilization/solidification (S/S) is a practical treatment approach for hazardous waste with anthropogenic As sources; however, its applicability for geogenic As-containing soil and the long-term leaching potential remain uncertain. In this study, semi-dynamic leaching test was performed to investigate the influence of S/S binders (cement blended with fuel ash (FA), furnace bottom ash (FBA), or ground granulated blast furnace slag (GGBS)) on the long-term leaching characteristics of geogenic As. The results showed that mineral admixtures with higher Ca content and pozzolanic activity were more effective in reducing the leached As concentrations. Thus, cement blended with FBA was inferior to other binders in suppressing the As leaching, while 20% replacement of ordinary Portland cement by GGBS was considered most feasible for the S/S treatment of As-containing soils. The leachability of geogenic As was suppressed by the encapsulation effect of solidified matrix and interlocking network of hydration products that were supported by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) results. The long-term leaching of geogenic As from the monolithic samples was diffusion-controlled. Increasing the Ca content in the samples led to a decrease in diffusion coefficient and an increase in feasibility for "controlled utilization" of the S/S-treated soils.

Internal curing effect of high volume furnace bottom ash (FBA) incorporation on lightweight aggregate concrete

Furnace Bottom Ash (FBA) is a by-product of coal-fired power generation plants. Few studies have focused on assessing the impact of using high volumes of FBA on lightweight aggregate concrete, especially on its dimensional stability and thermal insulation properties. In this study, normal weight coarse aggregate concrete (NAC) and lightweight coarse aggregate concrete (LWC) have been prepared. High volumes of FBA were used to replace natural fine aggregates to prepare the concrete mixes. Silica fume was used to mitigate the high permeability of concrete induced by porous aggregates incorporation. The compressive strength test results show that high strength LWC can be prepared with high volume FBA incorporation. The dimensional stability evaluation shows the linear relationship between FBA replacement ratio and autogenous shrinkage reduction. The internal curing effect of FBA aggregate has been investigated. The increased use of FBA in both NAC and LWC resulted in improved thermal insulation properties. The results indicate the potential of producing high performance lightweight aggregate concrete with high volume industrial by-products.

Alkali activated construction materials: Assessing the alternative use for oil shale processing solid wastes

The potential of oil shale ash wastes as a source material for geopolymeric or alkali activated construction materials was assessed using structural, XRD, SEM, SEM-EDX, ATR-FTIR and 29Si MAS-NMR methods. Fresh, unhydrated furnace bottom and cyclone separator ash along ash plateau sediment were used in combination with 5M NaOH and Na2SiO3 solutions with SiO2/Na2O ratios of 2.72 and 1.5 as alkaline activators, under ambient curing conditions. Our analytical results show that only activator solutions containing soluble silicate will induce the formation of amorphous C-(A)-S-H gel, giving the samples 8 times higher compressive strength (8.5MPa) than samples exhibiting cementitious properties upon hydration (1.25MPa).

Mechanical Properties of High Strength Concrete Containing Coal Bottom Ash and Oil-Palm Boiler Clinker as Fine Aggregates

This research aims to utilize Coal Furnace Bottom ash (CBA) and Oil-Palm Boiler Clinker (OPBC) as fine aggregate in concrete mix proportions. They are solid wastes from power plant and Oil Palm industry, respectively. Since these by-products do not have any primary use and are pure waste, an opportunity to use them as aggregate in concrete industry not only is economical but also will be an environmental friendly opportunity leading towards a more sustainable production chain. CBA and OPBC sands had similar grading to normal sand but have lower density and higher water absorption. In a high strength concrete, normal sand was replaced up to 25% with either CBA or OPBC. Test results showed that although water absorption of these wastes was more than normal sand but the slump value of concrete containing each of these wastes showed that these concretes had good workability. All mixes containing these wastes had slightly lower compressive strength at early ages and equivalent or higher compressive strength at later ages compared to control mix. The 28-day compressive strength of these concretes was in the range of 69–76 MPa which can be categorized as high strength concrete. In general, the performance of OPBC was better than CBA at 25% replacement level. However, it is recommended that at least 12.5% of total volume of fine aggregate in a high strength concrete is used of CBA or OPBC.

Use of Furnace Bottom Ash for producing lightweight aggregate concrete with thermal insulation properties

The influence brought by Furnace Bottom Ash (FBA) incorporation on the properties of lightweight aggregate concrete was studied systematically. In total, six mixtures of concrete targeted at a 28 d compressive strength of 30 MPa were designed, including one control mix made with all normal weight aggregates and at a water/cement ratio (w/c) of 0.6, and another five lightweight aggregate concrete mixes at a w/c of 0.39 by using 0, 25%, 50%, 75% and 100% FBA replacing natural fine aggregate (crushed fine stone). The testing results of the hardened concrete properties showed that, for the lightweight aggregate concrete using 100% FBA to replace crushed fine stone, a 28 d oven-dried density of about 1500 kg/m3 was obtained. The test results showed the lightweight aggregate concrete had lower strength and stiffness compared to the normal aggregate concrete. But in terms of the effectiveness of strength provided by unit weight of concrete indicated by compressive strength in MPa divided by saturated-surface dried (SSD) density in g/cm3, fc/D, a satisfactory ratio can be obtained when not more than 50% FBA was used to replace the crushed fine stone. The durability property indicated by the chloride ion penetration test shows the lightweight aggregate concrete with FBA had high chloride ion penetrability. The heat insulation property (thermal conductivity K-value) test demonstrated that by using the porous lightweight aggregate, the thermal conductivity could be lowered to around 70% of the control. When more FBA was used to replace crushed fine stone, the thermal conductivity value could be further reduced. The results of this study demonstrated it is feasible to produce lightweight aggregate concrete with high volume of FBA incorporation for building insulation uses.

Performance of herbaceous Evolvulus pilosus on urban green roof in relation to substrate and irrigation

Rooftop gardening (or green roof establishment) is an urban greening afforestation method that has many environmental, economic, and urban landscaping benefits. For rooftop vegetation, stressful environments that include heat, strong winds, sunshine, and drought prevent many plants from growing well, especially in shallow soil. To establish low cost urban rooftop gardens with a low weight substrate in the summer, we evaluated the green coverage and growth of a suitable groundcover ornamental plant, blue daze (Evolvulus pilosus). Blue daze was used as rooftop vegetation in a shallow substrate (10cm thick) on the flat rooftop of a four-story building in the middle of Kobe city, Japan, which has a temperate and humid climate. On average, the diurnal maximum temperatures and the total amounts of precipitation during each planting experiment between July and September were 30.8°C and 247mm in 2008 and 33.2°C and 458mm in 2009, respectively. Three different types of planting substrates (AS, amended soil, TM, turf mat as a dried-up blocks of sod, and FBA, furnace bottom ash) were tested to determine how they influenced plant cover, flowering, and growth. We evaluated the physical and chemical properties of the substrates that were used to establish the rooftop greeneries. In addition, the economy, ornamental and ecological values, reuse of material, and low rooftop weight burdens of the substrates were evaluated. The greatest blue daze ground cover occurred on the TM substrate (relative to the AS and FBA substrates) approximately three months after transplanting. The blue daze actively bloomed on all substrates throughout midsummer. However, alternate day irrigation largely reduced their shoot growth and flowering relative to daily irrigation. The AS and TM substrates had suitable physicochemical properties for use as planting substrates and had ideal solid, liquid, and vapor phase distributions and high water and nutrient holding capacities. FBA was a poor substrate with very low water and nutrient retention capacities, which resulted in depressed plant growth, especially under low watering conditions. To recycle FBA efficiently as a shallow low-cost planting substrate for rooftop gardening, the addition of coated fertilizers and organic matter to FBA should be considered to improve its water and nutrient holding capacities.