Metal correlation analysis of fly ash produced from fluidized bed thermal treatment of municipal solid waste incineration

( Astryd Viandila Dahlan ),( Hiroki Kitamura ),( Yu Tian ),( Hirofumi Sakanakura ),( Takashi Yamamoto ),( Hidetoshi Kuramochi ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1

Incineration is mostly used to treat Municipal Solid Waste (MSW) in Japan to reduce volume and weight of the waste. In 2014 total municipal solid waste (MSW) generated in Japan was about 44.32 million tons and around 80% from total MSW are treated by incinerator. Bottom ash and fly ash are the main secondary pollutant generated from incinerators. MSW incineration fly ash is categorized as hazardous waste due to high concentration of leachable toxic heavy metals and the presence of toxic organic compounds. Therefore, fly ash should be treated before its final disposal in landfill. The incineration bottom ash was obviously a heterogeneous matrix because of the different nature of municipal solid waste burnt in the incineration system. In contrast, MSWI fly ash is fine particles and has been regarded as homogeneous in numerous previous researches. However, it has not been proved based on sufficient micro-analysis. From the previous research of the authors’ group, it was found that fly ash particles from a stoker type MSW incinerator had mineralogical active surface because the secondary mineral formation on the surface of MSWI fly ash particles. We need further research about micro characteristic of MSWI fly ash regarded heterogeneous particles and correlation between particles in fly ash MSW incinerator. Therefore, the objective of the study is to investigate the metal correlation in fly ash particles from fluidized bed incinerator. Surface elemental concentrations of each fly ash particles, measured by SEM-EDS, were used to analyze elemental heterogeneity among fly ash particles. The surface of MSWI fly ash divided to 5 parts from the top side to down side horizontally. In this study, we focused on certain sections of fly ash particles on which Iron (Fe) and titanium (Ti) were detected in higher concentrations than other particles based on elemental mapping measurement using SEM-EDX. Detection intensities of silicate and iron of one section along with the distance is shown in Figure 1 (left). When silicate intensity, which is linearly correlated to silicate concentration, is high, iron intensity is lower. On the other hand, iron intensity is higher when silicate intensity is low. It is supported by negative correlation coefficient of silicate and iron. According to the authors’ previous research, MSW incineration fly ash particles consist of NaCl/KCl-base surface, Al/Ca/Si-base inner matrices, and Si-base cores with complex structures. This implies that Si-rich regions in Al/Ca/Si- base inner matrices include less amount of iron aggregates than Al-rich and/or Ca-rich regions. Detection intensities of aluminum and titanium of the other section along with the distance is shown in Figure 1 (right). Ti also has negative correlation with aluminum (Al). This implies that Al-rich regions in Al/Ca/Si-base inner matrices include less amount of titanium aggregates. Although sufficient number of observations and measurements are necessary, correlation analysis of major elements and metals of micro sections of fly ash particles might be useful to investigate elemental compositions of amorphous phase in fly ash particles

Intraparticle heterogeneity analysis of fly ash in fluidized bed thermal treatment of municipal solid waste incineration

( Astryd Viandila Dahlan ),( Hiroki Kitamura ),( Hirofumi Sakanakura ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2016 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2016 No.-

Incineration is mostly used to treat Municipal Solid Waste (MSW) in Japan to reduce volume and weight of the waste. Around 80% from total MSW are treated by incinerator. Bottom ash and fly ash are the main secondary pollutant generated from incinerators. MSW incineration fly ash is categorized as hazardous waste due to high concentration of leachable toxic heavy metals and the presence of organic compounds. Therefore, fly ash should be treated before its final disposal in landfill. The incineration bottom ash was obviously a heterogeneous matrix because of the different nature of municipal solid waste burnt in the incineration system. In contrast, MSWI fly ash is fine particles and has been regarded as homogeneous in numerous previous researches. However, it has not been proved based on sufficient micro-analysis. Therefore, the objective of the study is to investigate the micro-characteristics of fly ash from a fluidized bed type MSW incinerator and to investigate the elemental heterogeneity in into fly ash particles. According to SEM observation, raw fly ash from a fluidized bed combustor was categorized into two shapes based on morphological characteristics. Based on SEM image and elemental mapping results, major elements in fly ash particles generated from fluidized bed combustor are Na, Mg, Al, Si, Cl and Ca. Using line analysis from elemental mapping data, we can analyze correlation and distribution of elements in each particle. To get dispersion of element distribution in a particle, we calculate coefficient of variation of each element. It enables to evaluate the heterogeneity of each particle. Major elements in fly ash particles shows different dispersion in fly ash particles (see Figure 1). According to Figure 1, all major elements have large frequency distribution of coefficient of variation. However, calcium (Ca) and sulfur (S) shown different result than other elements. They have small frequency distribution of coefficient of variation. It shows that elemental distribution in a particle fly ash surface is heterogeneous.

Experimental trials of Si coating on the surface of municipal solid waste incineration fly ash particles using hydrated silica with sodium hydroxide

( Yu Tian ),( Astryd Viandila Dahlan ),( Giun Jo ),( Takashi Yamamoto ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 심포지움 Vol.2018 No.1

From about 1960, Japan accelerated treatment of urban garbage by incineration. In 2009, there were 1243 incineration facilities for municipal solid wastes (MSW) in Japan. Fly ash from municipal solid waste incinerators (MSWI) contains a lot of heavy metals as well as toxic organic substances. Incineration plants for MSW always equip flue gas treatment devices to remove SOx, HC1, NOx, smoke, dioxin and particulate solid residues in flue gases. The solid particles produced during municipal solid waste incineration (MSWI) in mass burning units may be grouped into bottom ashes (BA) and fly ashes (FA). MSWI fly ash is classified as hazardous waste because high contents of heavy metals and toxic organic compounds are possibly leached to the environment. Therefore, it is necessary to take some immobilization treatment before landfill disposal of fly ash. This research focuses on inorganic treatment for stable immobilization of toxic elements. Because the authors already found secondary mineral formation on the surface of fly ash particles under certain conditions and it was partially effective on physical immobilization of soluble elements, this study tried silicate-based inorganic treatment to promote secondary mineral formations and/or physical silicate coverage on the surface. In this study, fly ash sample was collected from a Japanese MSWI facility plant. Deionized water, hydrated silica (0.01mol/L) and sodium hydroxide (0.01mol/L) were used as inorganic agents to treat the MSWI fly ash. The inorganic agents were mixed with MSWI fly ash at the solid to liquid (L/S) ratio of 1. Moistened samples were dried at room temperature about 20 °C for about 120 hours. Scanning electron microscope (SEM) was used to observe the morphology of fly ash particles. Energy dispersive X-ray spectrometry (EDX) was used to observe the surface elemental concentrations of each fly ash particle. X-ray diffraction analysis (XRD) was used to detect major secondary minerals. According to the measurement results of XRD, the main minerals were sylvite, halite, anhydrite, gypsum, calcite and quartz. By the results of SEM observations and XRD analysis, there is no significant difference between raw and inorganic-treated MSWI fly ash in terms of mineralogical composition. It suggests that inorganic treatment tested in this study was not effective to promote secondary mineral formations which was detectable by XRD. This study also expected physical immobilization of soluble elements by silicate coverage on the surface of fly ash particles. Therefore, the authors focused on Si distribution on fly ash particle surfaces. In order to evaluate homogeneous or heterogeneous Si coverage by hydrated silica, the authors checked certain sections of the surface of MSWI fly ash particles on which high degradation of surface elemental concentration were found by elemental mappings. Especially, chlorine (Cl), calcium (Ca), and silica (Si) were detected in higher concentrations than other sections. When line profiles of elemental concentration variations along target sections were analyzed, large variation of Si compared to Cl and Ca were observed. The results of line profile analysis suggested that sodium silica solution, sodium aluminum or sodium silica was not simply adhered to the particle surface during inorganic treatment. This means that physical immobilization by Si coating would require method modification. At least, simple mixing using hydrated silica solution generates heterogeneous Si coating on the surface of fly ash particles.

Heterogeneity analysis of municipal solid waste incineration fly ash particles investigated by elemental line profile measurement

( Hiroki Kitamura ),( Astryd Viandila Dahlan ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2016 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2016 No.-

In Japan, municipal solid waste incineration (MSWI) fly ash is landfilled after immobilization treatment owing to high contents of heavy metals. Major treatment method is chelate treatment. Its immobilization mechanism is considered as complexation between chelating substances and heavy metals. Although mineralogical characteristics of MSWI fly ash are changed dramatically by secondary mineral formation in chelate treatment process, MSWI fly ash has been considered as homogeneous because fly ash is fine particles. However, micro-characteristics of fly ash might have non-negligible impact on leaching behavior of heavy metals if fly ash is heterogeneous. Therefore, this study investigated heterogeneity of raw and chelate-treated MSWI fly ash particles by elemental line profile analysis. Experimental samples are raw and chelate-treated MSWI fly ash collected from a Japanese MSWI facility plant equipped with stoker-type incinerator (incineration capacity : 250 Mg/d). Elemental mapping was conducted to investigate elemental distribution of fly ash particles by scanning electron microscope (SEM) equipped with energy dispersive X-ray analyzer (EDX). After elemental mapping, the surface of a fly ash particle was divided to 5 sections from the side to the other side horizontally. Line profile analysis was conducted at each divided section to analyze relative intensity of constituent elements. The coefficient of variation (C.V) of each element was calculated based on line profiles to evaluate heterogeneity in each particle. Elemental mapping showed that raw and chelate-treated MSWI fly ash particles consist mainly of Al, Ca, Cl, Na, O, and Si. In some cases, they contained other elements (K, Mg, and S) as well as heavy metals (e.g. Cr, Fe, Mn, Ti, and Zn). Calculated C.V. of major elements are shown in histogram (see Fig. 1). The C.V of Al, Na, O, and Si are mainly distributed in the range of 0 to 0.8. However, they often distributed around 1.0. Therefore, these elements seem to be heterogeneous in each particle. The C.V. of Ca are distributed in the range of 0 to 0.5. Therefore, Ca seems to be slightly heterogeneous in each particle. On the other hand, the C.V. of Cl are distributed widely. This means that Cl is very heterogeneous in each particle. As a result, these results suggest that a MSWI fly ash particle is heterogeneous although it has been considered as homogeneous without sufficient observations. In addition, its heterogeneity might have non-negligible impact on leaching behaviors of heavy metals. Line profile analysis is useful for micro-scale characterization of MSWI fly ash particles. However, only 51 particles were analyzed in this study. Therefore, further observations are required to homogenize experimental results.

Heterogeneity analysis of the surface and inner matrices of chelate-treated MSWI fly ash particles employing strong acid extraction

( Hiroki Kitamura ),( Astryd Viandila Dahlan ),( Yu Tian ),( Takashi Yamamoto ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1

Municipal solid waste incineration (MSWI) fly ash is considered as hazardous waste owing to toxic characteristics of heavy metals. In Japan, chelate treatment is mainly used to reduce their toxicity. However, the impacts of morphological and/or heterogeneous characteristics of MSWI fly ash on leaching behaviour of heavy metals are still uncertain. Therefore, this study investigated heterogeneity of the surface and inner matrices of chelate-treated MSWI fly ash particles at microscale level for fly ash characterization. Chelate-treated MSWI fly ash, which are collected from a Japanese MSWI facility plant equipped with stoker-type incinerator (incineration capacity : 250 Mg/d), were analyzed in order to investigate heterogeneity of the particle surface. Residual materials after acid extraction (Japan Leaching test 19th, JLT19) were also analyzed in order to investigate heterogeneity of inner matrices. Morphology and elemental distributions on the surfaces of MSWI fly ash particle were investigated by scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDX). One hundred chelate- treated MSWI fly ash particles and residual materials after JLT19 were analyzed, respectively. Line profile analysis was conducted on one fly ash particle surface, which is divided to 5 sections uniformly, in order to measure relative intensity of major elements. Coefficient of variation (CV value) was calculated based on obtained relative intensity in order to quantify heterogeneity of individual particles. Area analysis was also conducted in order to measure elemental concentration on particle surfaces as weight percent (wt%) and evaluate heterogeneity among fly ash particles. Elemental mapping by EDX showed that chelate-treated MSWI fly ash particles consist mainly of Al, Ca, Cl, K, Mg, Na, O, S and Si. In contrast, residual materials consist mainly of Al/Ca/Si-based matrices owing to leaching of soluble components such as KC1 and NaCl by JLT19. Calculated CV values and measured weight percent of inner matrices (Al, Ca, and Si) are shown in Figure 1. According to heterogeneity analysis, CV values of inner matrices were in the range of 0 to 1.0. However, large differences of CV values between chelate-treated MSWI fly ash and residual materials were not observed although the particle surfaces are covered by soluble components before JLT19. The A1 and Si weight percent of residual materials increased relatively in comparison with chelate-treated MSWI fly ash owing to leaching of soluble and semi-soluble components. In addition, their weight percent distributed widely after JLT19. This means that they have large heterogeneous characteristics among fly ash particles. In some case, residual materials (aluminosilicate) also had complicated structure such as skeleton. Therefore, these results showed that morphological and heterogeneous characteristics might have impacts on leaching behavior of heavy metals.

Preliminary observations of surface morphology of municipal solid waste incineration fly ash particles treated by sodium carbonate, sulfate, and phosphate

( Yu Tian ),( Hiroki Kitamura ),( Astryd Viandila Dahlan ),( Takashi Yamamoto ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1

Municipal solid wastes incineration (MSWI) is a commonly accepted solution in Japan for waste management by municipalities. The main products after incineration are bottom ash (BA) and fly ash (FA). The fly ash is cargorized as hazardous waste owing to high contents of heavy metals and toxic organic compounds like dioxin. It is necessary to take some immobilization treatment before landfill disposal of fly ash. The major treatment method in Japan is organic treatments such as chelating treatment. In this process, the authors found secondary mineral formations on fly ash surfaces. Because chelate reagents for organic treatment can be decomposed within several years and cause high concentraions of organic carbon in landfill leachate, this research focuses on inorganic treatments for stable immobilize of toxic elements. In this study, MSWI fly ash sample was collected from a Japanese MSWI facility plant. Materials used in this research are chelate-treated MSWI fly ash, and three kinds of inorganic reagents. They are sodium carbonate (0.01mol/L), sodium phosphate (0.01mol/L) and sodium sulfate (0.01mol/L). In organic treatment, sodium solutions were mixed with fly ash at the solid to liquid (L/S) ratio of 1. Moistened samples were dried at room temperature about 20 °C for about 5 days. X-Ray Diffraction (XRD) method was used to detect major secodaiy minerals. Scanning Electron Microscope (SEM) was used to observe the surface morphology of fly ash particles and Energy Dispersive X-Ray analyzer (EDX) equipped with SEM was used to measure elemental distribtuions of fly ash particle surfaces. According to the experiment results of XRD, the main crystals were sylvite, halite, anhydrite, gypsum, calcite and quartz. There is no significant difference bteween raw and inorganic-treated MSWI fly ash. It suggests that inorganic treatment did not promote secondary mineral formations which were detecable by XRD. SEM-EDX analysis showed that raw, chelate-treated and inorganic-treated MSWI fly ash particles consist mainly of Na, K, Cl, Ca, Al, and Si. According to SEM observations, significant differences of surface morphology of fly ash after inorganic treatment were not found in spite of chelate-treated MSWI fly ash. Although inomgaic treatments were expected to promote the formations of calcite (CaCO₃), gypsum (CaSO₄·2H₂O) and apatite (Ca₅(PO₄)₃(OH)₂), experimental conditions should be improved in particular water content, pH, and reaction time.

Surface and thermal properties of geocasted municipal solid waste incineration fly ash composites

( Giun Jo ),( Mengzhu Song ),( Patcharanat Kaewmee ),( Astryd Viandila Dahlan ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1

Municipal solid waste (MSW) generation is rapidly increasing in many developing countries owing to population and economic growths. Therefore, reducing MSW is a major issue in the world. In Japan, the incineration is one of the major treatments for reducing MSW volume and weight. Specially, MSWI ashes, which are bottom ash and fly ash, have great potential for recycling in various field such as construction. However, fly ash contains heavy metals like Pb and Zn. Therefore, it might cause environment pollution when they are recycled without any treatment. Chelate treatment for immobilizing hazardous heavy metals in fly ash has possibility of chemical/biological decomposition of chelate-metal complex and might cause long-term high concentration of organic hydrocarbons in landfill site as well as leaching of heavy metals to the environment. In this research, the authors targeted fluidized-bed incinerator fly ash. Fluidized-bed incinerators produce only fly ash and its application is strongly requested in Japan. To replace sand by fly ash, aggregating was required to adjust appropriate particle size in order to comply with physical requirements of heat carrier in fluidized bed combustors. This research utilized geocasting method to create sand-alternative heat carrier using fly ash. When fly ash are recycled as heat carrier, thermal treatment of fly ash is also expected for further immobilization of heavy metals contained in fly ash. In this research, the authors measured surface morphology by scanning electron microscope (SEM), heavy metal leachabilities by leaching tests, surface area by nitrogen adsorption based on Brunauer-Emmett-Teller model (BET), and thermal stability by thermogravimetric analysis. The results demonstrated geopolymer by calcined condition effects improved heavy metal immobilization value, and porous characteristic and heavy metal immobilization were influenced by high temperatures.

Preliminary micro-characteristics analysis of municipal solid waste incineration fly ash treated by geocasting and calcination

( Giun Jo ),( Patcharanat Kaewmee ),( Yu Tian ),( Mengzhu Song ),( Astryd Viandila Dahlan ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 심포지움 Vol.2018 No.1

Municipal solid waste (MSW) generation is increasing rapidly since 20^th century. For reducing volume and weight of MSW, incineration is one of the major treatments. Major products of municipal solid waste incineration (MSWI) are bottom ash and fly ash. MSWI Fly ash contains heavy metals like Pb and Zn. In order to immobilize hazardous heavy metals in fly ash, some treatments are used such as chelate treatment. However, chelate treatment has possibility of chemical/biological decomposition and cause long-term high concentration of organic hydrocarbons in landfill site as well as leaching of heavy metals to the environment. In this study, the authors focus on the alternative treatment. Fly ash can be replaced fluidized bed sand as heat carrier and it might provide thermal treatment like calcination during combustion operations. To replace sand by fly ash, however, fly ash is too fine particle so it should be aggregated to bigger particles in order to comply with physical requirements of heat carrier in fluidized bed combustors. Therefore, geocasting might be a promising solution for both fly ash application and fly ash thermal treatment. Materials used in this study are fluidized bed type MSWI fly ash, potassium silicate and potassium hydroxide. Geopolymer slurry was produced using 15M KOH solution, which should be used 24 hours after the solution curing. Then KOH solution was mixed with potassium silicate and distilled water in a mixer (200 rpm, 20 min) according to the following weight ratio: KOH (15 M): potassium silicate: H₂O = 1:2: 0.5. In this study, the authors added 20 g of KOH solution, 40 g of potassium silicate and 10 g of distilled water. Fly ash was added to this solution with equal amount to 15 M KOH solution. They were stirred at 200 rpm for 30 min at room temperature. Accelerating geopolimerzation reaction, geopolymer slurry was placed into an oven at 80 °C for 2 hours. After geopolymer foam was casted, some samples were calcined at 600 °C for 4 hours to simulate similar situation in a fluidized bed combustor. After sample treatments, raw fly ash, geocasted fly ash and geocasted-calcinated fly ash were analyzed by scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX). From SEM observations, raw fly ash mainly consisted of Al, Na, Ca and Cl. They showed sphere particles with smooth surface. On the other hand, geo casted fly ash consisted of more Si and K than raw fly ash. Geocasted fly ash also showed porous characteristic and irregular shape than raw fly ash. Lastly, geocasted-calcinated fly ash consisted of similar elements with geocasted fly ash particles. After calcination, however, porous characteristic disappeared. These results imply that geocasting makes porous particle and following calcination might melt the surface and degrade porous structure. Further research is necessary to check physical stability of goecasted fly ash and toxic element immobilization after geocasting and calcination.