Species In Ash Research Articles

Valorization of agriculture waste: Preparation of alkoxysilanes from mixed rice straw and rice husk ash

Synthesis of alkoxysilanes from renewable silica resources could promote their sustainability but remain grand challenges. Herein, we present a simple, effective strategy to synthesize tetraethyl orthosilicate (TEOS) directly from bio-derived silica through supercritical ethanol processing, where no catalyst nor additives are required. Crucially, calcination temperature is demonstrated to play a critical role in altering the structure of silica in rice husk ash (RHA), which directly influences its conversion activity to alkoxysilanes. Specifically, under optimized conditions at 280 °C and 1 h, RHA obtained at 400–625 °C calcination allows for an amorphous silica structure and as high as 85 mol% yield to alkoxysilanes. Moreover, the ash obtained from mixed rice straw and rice husk yields over 94 mol% alkoxysilanes, demonstrating the self-catalytic potential of the natural complexity of the ash. The effects of typical minerals contained in ash on the reaction are probed. It is revealed that potassium oxide is the main catalytic species in ash, which provide a suitable alkaline strength. The concentration of potassium ion exhibits a pronounced positive effect on catalyzing the synthesis of alkoxysilanes, and the co-existed phosphorus species exhibits promotional effect to TEOS selectivity. Furthermore, 29Si MAS NMR and Laplacian bond order analysis reveal that the cleavage of Si-O-Si bond predominates in the supercritical ethanol environment, providing a viable path for the production of TEOS.

Analysis of fouling in domestic boilers fueled with non-woody biomass

The greater sustainability of agricultural and industrial wastes (non-woody biomass) when compared to the widely used high-quality forestry biomass encourages their usage in small-scale thermal devices (residential and domestic applications). However, the typical significant ash and alkali-compounds content of agro-industrial wastes may form undesirable deposits over the heat exchange surfaces that could require additional cleaning systems (thus increasing the cost and complexity of the boilers). This work analyses the fouling tendency of exhausted olive cake and almond shells when used in a biomass boiler (with a nominal thermal capacity of 55 kW) at partial and nominal load, trying to highlight the main mechanism leading to the deposits growth depending on the fuel properties and load. Inertial impaction of coarse fly ash governs deposition at partial load for almond shells, this is attributed to the low K, Cl and S content and the lower bed temperature reached (431 °C vs 528 °C at nominal load). Among the deposition mechanisms associated to K-salts condensates, direct condensation on the incipient layers dominates over thermophoresis of submicron particles at nominal load. Although no additional maintenance procedures seem to be required when using almond shells, it is highly recommended to remove K/Cl components from exhausted olive cake through prior water leaching or by using additives to retain these species in the bottom ash.

Interactions of co-firing coal gangue and high sodium coal: Combustion characteristics and emission behaviors of polluting gases

To promote the utilization of coal gangue (CG) as alternative fuels for heat or power generation, this work investigated the interactions between a CG (denoted as XJG) and a high sodium coal (HSQ) during co-combustion as well as the evolution behaviors of gaseous pollutants (SO2 and NO). Results show that co-firing HSQ with less than 30 % XJG does not deteriorate its combustion performance. Synergistic conversion is observed due to the complementarity of the fuels in volatile matter, fixed carbon, ash content and reactivity. Moreover, alkali and alkaline-earth metals promote co-firing and lower activation energy of combustion from 100 to 70 kJ/mol. Both SO2 and NO are evolved in two stages during co-combustion as described by the shrinking core model and 3D-diffusion model. NO is reduced by char and CO and the reduction is catalyzed by the alkaline species(especially CaO) in ash. SO2 emission behavior is significantly varied by the competitive reactions of calcium oxide with silica/alumina species. Overall, NO is decreased by about 10 % relatively at 900–1100 °C while SO2 is notably enhanced at 1000 °C by 23 %. The mechanism of formation and reaction of SO2 and NO are proposed. These results provide useful reference for clean utilization of CG and controlling of polluting gas emission, thus boosting sustainable development of energy, ecology and environment.

Effects of flood duration on seedling survival and growth of potential replacement species in black ash (Fraxinus nigra Marshall) forests threatened by emerald ash borer

Within black ash (Fraxinus nigra Marshall) wetlands, black ash acts as a foundational species, resulting in high vulnerability to the invasive emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae). One mitigation strategy being considered is the planting of alternative tree species to increase compositional diversity, however, there is limited understanding of how replacement tree species tolerate flooding. A greenhouse experiment was used to explore early survival and growth of eighteen tree species in response to five flooding durations (3, 6, 9, 12, or 15 weeks). Seedlings were assigned to flood tolerance groups according to their responses to the various flooding duration treatments. Taxodium distichum (L.) Rich., Ulmus americana L., and Betula nigra L. were able to survive and grow with flooding durations of up to 15 weeks. Thuja occidentalis L., Acer rubrum L., Larix laricina (Du Roi) K. Koch, Quercus bicolor Willd., and Betula alleghaniensis Britton had high survival and growth rates with flooding durations up to 6 weeks in length. Finally, Juglans nigra L. and Acer saccharum Marshall responded poorly to flooding of any duration. These results can assist managers in matching potential black ash replacement species to the hydrology of their local black ash wetlands.

Effects of torrefaction on ash-related issues during biomass combustion and co-combustion with coal. Part 3: Ash slagging behavior

Torrefaction is a competitive technology for biomass upgrading. Knowing that the effects of torrefaction on ash-related issues during biomass combustion and co-combustion with coal have been less investigated, Parts Ⅰ and Ⅱ of this work investigated the particulate matter emission and ash fouling behavior. To be a continuation, in the present paper, the effect of biomass torrefaction on ash slagging deposition which occurs in the high-temperature areas of the furnace was focused on. Two herbaceous biomass, one woody biomass, and their torrefied chars were fired and co-fired with two coals respectively on a drop-tube furnace at 1300℃. The slags were collected from mullite tubes placed in the furnace for quantification and characterization. Computer-controlled scanning electron microscope (CCSEM) was employed to obtain the distribution of particle size and inorganic species in the bulk ash. The results indicate that co-firing the biomass with high-Ca coal significantly reduces the ash slagging rates due to the substitution of alkalis by Ca from the silicates/aluminosilicates which inhibits the agglomeration and sintering of the ash particles, and finally reduces the inertial impaction and capture of the particles on the tube. Co-firing corn stalk with the high-Si/Al coal promotes the formation of alkaline aluminosilicates which are sticky at a high temperature. Therefore, the slagging tendency is exacerbated. Torrefaction reduces the ash slagging rate of sawdust resulting from the effective removal of S and Cl and the transformation of AAEMs (alkaline and alkaline earth metals) into less-reactive forms during torrefaction which reduces the vaporization and transformation of AAEMs into coarse particles as aluminosilicates by surface reactions. However, the ash slagging rates are increased by torrefaction for other fuels due to more retention of AAEMs after torrefaction resulting in more mixed silicates or aluminosilicates in bulk ash contributing to the growth of slagging deposits during combustion. Measures are suggested to be taken, such as optimizing the operation conditions, co-firing with high-Ca coals, using additives, etc. to alleviate the ash slagging during torrefied herbaceous biomass combustion.

Dispersion of arsenic species from highly explosive historical volcanic eruptions in Patagonia

Andean volcanic rocks typically have low to moderate arsenic (As) concentrations. However, elevated levels of As in groundwaters of southern South America have been reported as a consequence of weathering of volcanic glass. This study discusses the abundance, speciation and dispersion of As species in fresh volcanic ash from highly explosive (Volcanic Explosivity Index: 4–5) Patagonian eruptions, as well as the potential of As release to aqueous reservoirs. Synchrotron-based X-ray absorption and micro-focused X-ray photoelectron spectroscopies were used to evaluate As solid speciation. Batch experiments at different pH conditions were performed with the aim of understanding the controls on As release to aqueous reservoirs. Bulk chemical and mineralogical characterizations were performed by inductively coupled plasma optical emission spectroscopy, X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy. Finally, to understand how As-bearing phases are spatially distributed after eruptions, simulations of volcanic ash emission, transport and deposition were performed.Results indicate that the concentration, speciation, and mobility of As in fresh Patagonian volcanic ash depend on the silica content of source magmas. Although the main As host in volcanic ash is Al-silicate glass, this phase is stable at neutral pH characteristic of most aqueous reservoirs. Higher contributions of As to water are associated with the more mobile As species that concentrate onto the surface of Al-silicate glass. Atmospheric dispersion simulations revealed that primary fallout of As-bearing ash has affected large areas in Patagonia, but also reached the Chaco-Pampean plain, where the presence of As-rich groundwater has been widely documented.

Mitigation of particulate matter emissions from co-combustion of rice husk with cotton stalk or cornstalk

PM emission is one of key issues in the biomass combustion of heat and power plants. In this paper, rice husk (RH) was co-combusted with cotton stalk (CSK) or cornstalk (CS) to study the PM emission behaviors. The experimental results show that the addition decreases PM1 yields by 20.13–54.65% for CSK and 45.99–76.70% for CS in comparison to the CSK or CS combustion alone. A strong synergistic effect exists during the co-combustion process, which can appreciably inhibit the generation of fine particulate matter. The synergistic effect is caused by the physical dilution effect, and mainly by the reaction between alkali metals species in cornstalk/cotton stalk ash and Si-containing species in rice husk ash to inhibit the volatilization of alkali metals. However, the PM reduction degree is also affected by the ash chemistry, especially the Si/(Ca + Mg) ratio, as confirmed by the higher synergistic effect of rice husk/cornstalk compared to rice husk/cotton stalk. The results suggest that co-combustion of biomass with high Si-containing rice husk is a promising approach to reduce PM1 emissions during biomass co-combustion.

A review of concrete durability in marine environment

There are many concrete constructions in marine environments. Due to its salinity content, seawater is aggressive, both towards concrete and reinforcement. Concrete interacts with seawater which causes deterioration. The chemical attack occurs at least through 3 common mechanisms: sulfate-attack, carbonation, and chloride-induced corrosion of reinforcement. The chemical resistance of concrete is determined by the porosity and chemical composition of the concrete. Partly subsitution of cement with supplementary cementitious materials (SCM) known as an effective way to create the less permeable concrete. Concrete with fly ash as SCM has excellent potential to be applied to marine construction in Indonesia because the abundant availability of fly ash in Indonesia and the presence of aluminum species in fly ash provide an opportunity to increase binding capacity to chloride.

Eighth-year survival and growth of planted replacement tree species in black ash (Fraxinus nigra) wetlands threatened by emerald ash borer in Minnesota, USA

Black ash (Fraxinus nigra) is native to lowland forests of the western Great Lakes region, USA, where it often comprises a majority of trees. Like all native ash in North America, black ash is threatened by emerald ash borer (EAB; Agrilus planipennis), but the impacts from EAB mortality may be particularly severe in these forests given the foundational role of black ash at regulating ecosystem function. Compounding the problem is that associated tree species occur in low abundance and their abundance may be further reduced as habitat declines with climate change. These converging threats point to the need for silvicultural intervention to establish replacement tree species in anticipation of EAB invasion. Here we report on a large-scale management experiment from Minnesota, USA that includes different silvicultural approaches for establishing replacement tree species in black ash forests. Specifically, we examined eighth-year survival and growth of planted seedling in treatments that included clearcutting, group selection, uncut forest, and emulation of EAB mortality by girdling black ash. Species included nine that are native to the ecosystem, two from the next southern climate zone, and one exotic species, Manchurian ash (Fraxinus mandshurica). Among species and treatment combinations, survival was highest for American elm (Ulmus americana), averaging around 81% in uncut, group selection, and girdle treatments. Swamp white oak (Quercus bicolor), a species from the next southern climate zone, also had high survival in these treatments (ranging from 61% to 79%). Both species had survival under 60% in the clearcut treatment. Most native southern boreal species, as well as Manchurian ash, had low survival (0% to less than 40%) in most treatments. In the clearcut, girdle, and group selection treatments relative diameter and relative height growth was highest for balsam poplar (Populus balsamifera), averaging, respectively, around 0.25 mm mm−1 yr−1 and 0.20 cm cm−1 yr−1, followed by swamp white oak and red maple (Acer rubrum). Non-native Manchurian ash had consistently low growth in all treatments compared to other species. All species had low growth rates in the uncut treatment. An integration of survival and diameter growth pointed to group selection as the treatment that provides the best balance between survival and growth. Our results indicate promising survival and growth of at least some replacement species, including several predicted to be future climate-adapted, as well as a silvicultural approach in group selection that is an effective method to regenerate these species.

Mitigation of Particulate Matter Emissions by Co-Combustion Rice Husk with Two Other Biomass

PM emission is one of key issues in the biomass combustion of heat and power plants. In this paper, rice husk (RH) was co-combusted with cotton stalk (CSK) and cornstalk (CS) to study the PM emission behaviors when RH was added to CSK or CS. The experimental results show that the addition decreases PM 1 yields by 20.13-54.65% for CSK and 45.99-76.70% for CS in comparison to the CSK or CS combustion alone. A strong synergistic effect exists during the co-combustion process, which can appreciably inhibit the generation of fine particulate matter. The synergistic effect is caused by the physical dilution effect, and mainly by the reaction between alkali metals species in cornstalk/cotton stalk ash and Si-containing species in rice husk ash to inhibit the volatilization of alkali metals. However, the PM reduction degree is also affects by the ash chemistry, especially the Si/(Ca+Mg) ratio, as confirmed by the higher synergistic effect of rice husk/cornstalk compared to rice husk/cotton stalk. The results suggest that co-combustion of biomass with high Si-containing rice husk is a promising approach to reduce PM 1 emissions during biomass co-combustion.

Demineralization of Food Waste Biochar for Effective Alleviation of Alkali and Alkali Earth Metal Species

Ash-related issues from a considerable amount of alkali and alkaline earth metal species in biochar are major obstacles to the widespread application of biomass in thermoelectric plants. In this study, food wastes were converted into biochar through pyrolysis at 450 °C or 500 °C and four different demineralization approaches, using deionized water, citric acid, nitric acid, and CO2 saturated water. The chemical properties of the resulting biochars were investigated, including proximate analysis, concentrations of inorganic species in biochar and ash, and the crystalline structure. All demineralization treatments produced food waste biochar with sufficient calorific value (>4000 kcal/kg) and a chlorine concentration <0.5%. Among the inorganic species in biochar, Na and K exhibited a significantly higher removal rate through demineralization, which ranged from 54.1%–85.6% and 53.6%–89.9%, respectively; the removal rates of Ca and Mg were lower than 50.0%. The demineralization method was more critical than the pyrolysis temperature in the removal of alkali and alkaline earth metals. Especially, the lower slagging and fouling tendency was expected for the biochar demineralized with citric acid. Our results suggested that food waste biochar pyrolyzed at 500 °C and demineralized with citric acid is a promising co-firing material for electric power generation in thermoelectric power plants.

Speciation analysis of arsenic in coal and its combustion by-products in coal-fired power plants

The speciations of Arsenic (As) in coal will inevitably convert during the combustion process. The As speciations in coal and its by-products are closely related to human health and environmental safety which is urgent to be identified. However, there is a lack of pretreatment procedure and analysis method on the As species in coal-related products in power plants. In this study, the As species in coal, fly ash (FA), and gypsum were successfully determined by high performance liquid chromatography coupled with hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS). The instrument parameters, extract reagents, and pretreatment methods (i.e. ultrasound and microwave-assisted) were optimized. The whole separation time of inorganic As was shorten to 7 min after optimization, with the detection limit of 1.8 and 4.6 ng/g for As(III) and As(V), respectively. The efficient As extract reagent was the mixture of 1.0 mol/L H3PO4 and 0.1 mol/L ascorbic acid solution. Microwave-assisted (2000 W, 80°C, 40 min) and ultrasound-assisted (40 kHz, 20°C, 40 min) schemes were the optimal extraction methods for coal/FA and gypsum samples, respectively. Under the proposed microwave and ultrasound extraction procedure, the recovery of As(III) and As(V) could reach to 95.8%/104.5% and 90.6%/89.7%, respectively. The dominant occurrence of As species in coal was As(V) with a small percentage of As(III), while As(V) was the only occurrence form observed in FA and gypsum. It is indicated that revealing the transformation of As(III) to As(V) is the key for gaseous As capture. The As species distribution investigation provides a scientific insight to the controlling of As emission from power plant.

Study on reduction characteristics of Fe species in coal ash under SNCR condition

To obtain the reduction characteristics of NH3 on Fe2O3 in coal ash, and verify that the injected ammonia-bearing reductant led to slagging during SNCR, the slag sample was collected at the flue gas temperature range of 720 °C–780 °C in a medium temperature separation circulating fluidized bed boiler (MTS-CFBB). The XRF, XRD were used to determine the elemental distribution and mineral composition. The reduction reaction of CO, NH3 with Fe2O3 was calculated by HSC Chemistry 6.0 to obtain the reduction ability. Moreover, the mineral transformation in coal ash was studied by the tube furnace under N2 and N2-NH3 atmosphere. The results indicated that the contents of Fe2O3 in the three layers of slag sample were 16.36%, 16.00%, and 12.63% respectively from outside to inside, which were higher than that in burned coal ash. The NH3 has stronger reduction ability as compared to CO reacting with Fe2O3 and Fe3O4 at the temperature range of 720 °C–780 °C. With the reacting temperature increasing, the added NH3 led to more Na and O release, lower decomposed temperature of CaSO4. The NH3 reduced the Fe3+ in coal ash to form the Fe3O4, FeO or other Fe2+ contained compounds at the high-temperature. The formed Fe2+ contained compounds with low melting temperature played a glue role to promote the slagging process. At last, the slagging mechanism caused by injected ammonia-bearing reductant under the SNCR condition was established.

Uranium and thorium species in phosphate rock and sewage sludge ash based phosphorus fertilizers

Phosphorus (P) is an essential element for all forms of life and is thus often applied as phosphate rock-based P-fertilizers in agriculture to enable continuous farming. However, these P-fertilizers contain also hazardous uranium (U) and thorium (Th), up to 660 and 220 mg/kg, respectively. On the contrary, novel P-fertilizers made from sewage sludge (ash) contain only low mass fractions of U and Th. In addition to the total amount of U and Th in P-fertilizers, their mobility and bioavailability is important, which depends to a large extent on their chemical state, especially oxidation state and chemical bonding. Thus, we analyzed their chemical state in various P-fertilizers by U and Th L3-edge HERFD-XANES spectroscopy. Phosphate rocks and sewage sludge-based P-fertilizers contain mainly U(IV) compounds which have only a low bioavailability. In contrast, acidic treatment of phosphate rock to produce super phosphates lead to an oxidation to U(VI) compounds (including formation of uranium phosphates) with a strongly increased bioavailability. On the contrary, all analyzed P-fertilizers contain Th in form of strongly insoluble phosphates and oxides with a low bioavailability. Additionally performed water extractions and Diffusive Gradients in Thin-films (DGT) experiments support these findings.

High-calcium fly ash recovery from wet-stored condition and its properties

Fly ash can undergo changes in its properties during the wet-stored conditions, leading to reactivity variability consequently affecting its potential applications. Evaluation of the material properties is considerably essential. This work reports on an investigation of changes in physical and chemical properties of high calcium fly ash after recovering from the wet-stored conditions. Herein the high calcium lignite fly ash with calcium oxide constituent in a range of 20%–30% is the focus of this study. Important characteristics of fly ash have been studied, including physical properties, morphologies, chemical composition, and crystallographic phase transformation. Relation of oxide composition including silica, alumina, ferric oxide, and sulfur trioxide, to wet-storing period has been established to visualize the effect of short-term storage in water on changes in the content of mineral bearing species in fly ash. The strength activity indices of the recovered fly ash samples cured for 7 and 28 days has been presented. The significant amount of free lime and soluble calcium, aluminum, and sulfur-bearing minerals varying with storage times are believed to play their pronounced role governing compressive strength.

A kinetic study on the catalysis of KCl, K2SO4, and K2CO3 during oxy-biomass combustion

Biomass combustion under the oxy-fuel conditions (Oxy-biomass combustion) is one of the approaches achieving negative CO2 emissions. KCl, K2CO3 and K2SO4, as the major potassium species in biomass ash, can catalytically affect biomass combustion. In this paper, the catalysis of the representative potassium salts on oxy-biomass combustion was studied using a thermogravimetric analyzer (TGA). Effects of potassium salt types (KCl, K2CO3 and K2SO4), loading concentrations (0, 1, 3, 5, 8 wt%), replacing N2 by CO2, and O2 concentrations (5, 20, 30 vol%) on the catalysis degree were discussed. The comparison between TG-DTG curves of biomass combustion before and after water washing in both the 20%O2/80%N2 and 20%O2/80%CO2 atmospheres indicates that the water-soluble minerals in biomass play a role in promoting the devolatilization and accelerating the char-oxidation; and the replacement of N2 by CO2 inhibits the devolatilization and char-oxidation processes during oxy-biomass combustion. In the devolatilization stage, the catalysis degree of potassium monotonously increases with the increase of potassium salt loaded concentration. The catalysis degree order of the studied potassium salts is K2CO3 > KCl > K2SO4. In the char-oxidation stage, with the increase of loading concentration the three kinds of potassium salts present inconsistent change tendencies of the catalysis degree. In the studied loading concentrations from 0 to 8 wt%, there is an optimal loading concentration for KCl and K2CO3, at 3 and 5 wt%, respectively; while for K2SO4, the catalysis degree on char-oxidation monotonically increases with the loading potassium concentration. For most studied conditions, regardless of the potassium salt types or the loading concentrations or the combustion stages, the catalysis degree in the O2/CO2 atmosphere is stronger than that in the O2/N2 atmosphere. The catalysis degree is also affected by the O2 concentrations, and the lowest catalysis degree is generally around 20 vol% O2 concentration. The kinetic parameters under the different studied conditions are finally obtained.

The formation of deposits and their evolutionary characteristics during pressurized gasification of Zhundong coal char

The characteristics of deposits formed on stainlesssteel substrate (boiler tube) during pressurized gasification of Zhundong coal char with excessively high Na content were investigated in this work. The occurrences of alkali and alkaline earth metallic species in raw coal and its derived chars were determined by a sequential extraction method. The morphology, mineralogy and chemical compositions of deposits and bottom ash produced during the gasification of Zhundong coal char at 800, 1000 and 1200 °C were analyzed by X-ray diffraction and scanning electron microscopy combining energy dispersive X-ray spectrometer. Results show that water-soluble and ammonium acetate solution soluble sodium and potassium in raw coal tended to be converted to hydrochloric acid solution soluble form during Zhundong coal pyrolysis. Rising pyrolysis temperature increased the content of water-soluble calcium by enhancing the decomposition of CaCO3 and organically bonded calcium. During the gasification of Zhundong coal char, the released inorganic species, especially Na, Ca, Cl and S, could condense and/or agglomerate as sticky fine particles, resulting in fouling and slagging on the probes. Specifically, after Zhundong char gasification at 800 °C, alkali and alkaline earth metallic species-bearing minerals loosely clung on the probes as silicate or aluminosilicate. During char gasification at 1000 °C, a Na-S-O and/or Na-S deposit layer with a thickness of ca. 2 μm was formed on the probe No. 1 at 514 °C, while abundant Ca-Mg-Si-O and few Na2SO4 crystals were accumulated on the probe No. 2 at 771 °C. During Zhundong char gasification at 1200 °C, the minerals deposited at low temperature region (599 °C) were mainly composed of agglomerated and sintered alkali and alkaline earth metallic species-bearing compounds (mainly NaCl, KCl and Ca-Mg-Si-O). However, only few isolated particles were observed on the probe with temperature higher than 924 °C. Residual alkali and alkaline earth metallic species in bottom ash could form low-melting eutectics, such as NaAlSiO4 and Ca2Al2SiO7.

Efficacy of carbonated petroleum coke fly ash as supplementary cementitious materials in cement mortars

Abstract In this study, an innovative valorization of petroleum coke fly ash as supplementary cementitious materials in blended cement mortars was investigated. To stabilize and upgrade the properties of fly ash, accelerated carbonation was performed to convert calcium oxide and other calcium-bearing species in fly ash into calcium carbonate. The results indicated the achievable carbonation conversion of fly ash was approximately 40%. The changes in physico-chemical properties of fly ash before and after carbonation also were examined by thermal analysis and Fourier-transform infrared spectroscopy. Several material function tests of blended cement mortars with carbonated fly ash, including workability, strength development and durability, were carried out. We found that the strength of cement mortars blended with carbonated fly ash was 20% higher than that of original Portland cement. A mathematical model on the strength development kinetics was developed to elucidate the relationship between mineral compositions and curing times. The carbonated fly ash could facilitate the hydration reaction in blended cement, as well as accelerating the strength development of blended cement by 28%. This study revealed the possibility of establishing a waste-to-resource supply chain by connecting CO2 mineralization with fly ash valorization as cementitious materials.

Effect of Ash Components on the Performance of Solid Oxide Electrolyte-Based Carbon Fuel Cells

The effect of coal ash on the electrochemical performance of solid oxide electrolyte-based carbon fuel cells (SO-CFCs) is investigated in this study. The polarization and durability performance of SO-CFCs fueled by lignite char, ash-free char, and ash-added char were measured and compared from 1023 to 1123 K. The influence of five different coal ashes and six typical inorganic species was evaluated in SO-CFCs during short-term operation. The anode morphologies were analyzed to clarify the cell degradation. The results indicate that lignite char shows a higher initial cell performance but a lower stability than ash-free char in SO-CFC. The higher initial cell performance is attributed to the superior CO2 gasification reactivity, while the lower stability is more likely caused by carbon and ash deposits. The effect of coal ash on the cell performance is strongly dependent upon the ash composition. Inorganic Ca, K, and Fe species in coal ash improve the initial cell performance by catalyzing char–CO2 gasific...

Study on the Hg emission and migration characteristics in coal-fired power plant of China with an ammonia desulfurization process

Migration and emission characteristics of mercury in coal-fired power plant with an ammonia-based wet flue gas desulfurization (Am-based WFGD) process were studied based on the Ontario Hydro Method (OHM). The temperature-programmed desorption (TPD) method was used to identify the mercury species enrichment mechanisms in fly ash and the by-products of desulfurization. The SCR has a 95.41% mercury oxidation efficiency attributed to the high chlorine content in feed coal. SCR+ESP+WFGD combination has 94.15% gaseous mercury removal efficiency. Mercury distribution analysis showed that most of incoming mercury was deposited in solid (76.46%), and only 4.94% gaseous mercury was emitted to atmosphere. The TPD results indicate that HgCl2 and HgO are the dominant mercury species in fly ash while mercury in WFGD products exists in HgCl2 form. The re-emission of mercury during ammonia desulfurization did not occur due to the presence of forced oxidation process, while mercury release from desulfurization product was monitored suggesting the mercury re-emission from the ammonium sulfate separate and drying system could not be ignored. The mercury emission factor of the coal-fired power plant is calculated as 0.319g/1012J, less than the mean value of Chinese power plant. With the equipment of Am-based WFGD, the mercury content in ammonium sulfate is 1.126mg/kg, therefore the environmental influence from ammonium should be taken into account.