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( Hiroyuki Ishimori ),( Hirofumi Sakanakura ),( Kazuto Endo ),( Tomonori Ishigaki ),( Masato Yamada ) 한국폐기물자원순환학회(구 한국폐기물학회) 2013 한국폐기물자원순환학회 추계학술발표논문집 Vol.2013 No.-
Prediction method for the long-term chemical leaching amount from by-product/recycled materials such as waste concrete and steel slag and so on is necessary to widely promote their effective utilization and evaluate their environmental safety. Although there are the batch leaching tests and the column leaching test as the testing methods for evaluating the long-term leaching behavior, the leaching mechanism and the testing result compatibility in both tests has insufficiently been clarified yet. Thus, the prediction of the leaching behavior from the by-product/recycled materials used in actual civil works and their environmental safety evaluation are by no means certain. This paper shows the difference between the batch leaching tests and the column leaching tests in the chemical leaching behavior of Cu-slag. The batch leaching tests were conducted under liquid/solid ratio = 10, liquid = distilled water, stirring strength = 0, 30, or 120 rpm. After a certain elapsed time, the leaching solution was exchanged with the pure distilled water and then the stirring was restarted. The elapsed time was set at 1, 2, 4, 8, 16, 32 days. The column leaching tests were also conducted under the same conditions as those of the batch leaching tests in order to evaluate the effects of the pore distribution and the pore flow velocity in the Cu-slag column on the leaching behavior. In the column leaching tests, the effluent passing through the column was circulated as the influent (Fig. 1). The leaching duration in the column tests can be equivalent as that in the batch tests, so that the difference in the leaching behavior between the batch leaching tests and the column leaching tests may be dependent on the pore-scale heterogeneous flow and path generated in porous materials. Figure 2 shows the leaching rate evaluated from the batch leaching tests and the column leaching tests. In the same fluid velocity levels, the leaching rate in the column tests was larger than that in the batch tests. The leaching rate has been considered large with the fluid velocity. Although the fluid velocity generated by the stirring was the same as the flushing velocity on the surface of the Cu-slag in the batch tests, the fluid velocity in the column tests was enhanced because the permeant liquid was concentrated into the limited pore space in the Cu-slag column. Thus, the pore-scale heterogeneous flow and path generated in porous materials should be evaluated in order to clarify the compatibility between the batch leaching tests and the column leaching tests.
Sorting of MSW incineration bottom ash according to size and density by applying Air Table separator
( Seungki Back ),( Hirofumi Sakanakura ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1
Various types of metal could be contained in a municipal solid waste (MSW) incineration bottom ash ranging from a large size of scrap metal to trace of valuable metal in small size particles. Recently, interest in physical separation of metals from MSW incineration bottom ash is growing up in order to move towards a material cycles society. Separation and characterization of MSW incineration bottom ash could derive two effects: recovery of metals as resources and excluding toxic metals before recycling the bottom ash in construction as a secondary raw material. The present research examined the Air table separator as a dry method for physical sorting according to size and density of bottom ash particles. Recycling of scrap metal such as iron and aluminum have been widely carried out in commercial MSW incineration plants. Also, ferrous and non-ferrous metals were separated from incineration bottom ash using conventional magnetic and eddy current separation. However, efficiency for small particles of a commercial eddy current separator is known to be unsatisfactory. A technique for separating small size particle containing metal compounds is needed to be applied in order to more aggressive metal recovery from incineration bottom ash. Air Table is an effective method for sorting mixtures of various particles with different density. Air Table has advantages; low capital and operating costs and less possibility secondary contamination because Air table is a dry type physical separator without chemicals. Particles with different density could be separated by changing of variables: air injection rate, vibration intensity, end slope, and side slope. Introduced target sample could be separated depends on density of particles by controlling the variables of Air Table. In this study, Air Table separation was applied to classification of MSW incineration bottom ash depends on particle density. And, bulk density and dry density of separated bottom ash were measured. MSW incineration bottom ash with 4-8, 2-4, 1-2, and 0.5-1 mm was applied to Air Table to identify particle movement on Air Table by various operating conditions as a performance test. The outlet of Air Table was divided into 4 parts to collect separated bottom ash particles according to its density. Based on data from the performance test, the effect of each variable (air injection rate (1.0-2.9 m/sec), vibration intensity (5.5-8.0 Hz), and end slope (3-14.5˚)) on particle movement was evaluated. Then, the bottom ash with 4 size ranges was classified into 6 bulk density ranges from < 0.7 g/cm3 to >1.1 g/cm3 at intervals of 1 g/cm3. Measuring cylinder and balance were used for the measurement of bulk density of particles. And, the dry density meter (AccuPyc Ⅱ 1340, Micromeritics) was applied to measure the dry density in a series of experiments. The dry density of the separated bottom ash was measured ranging from 2.19 g/cm3 to 3.63 g/cm3. The fractions which contain a high proportion of the specific elements could be separated according to particle size and its density. XRF analysis was conducted to identify the element composition of the separated particles. Heavy metals (Pb, Cu, Zn) of the higher density fractions showed high concentration compared to the lighter density fractions. On the other hand, the concentration of certain elements (Ca, Cl, etc.) showed a negative correlation with the density of the particles. The results of this study could be utilized for the sorting of MSW incineration bottom ash in terms of recycling of metal, and reducing of environmental hazard.
Hiroyuki Ishimori,Hirofumi Sakanakura,Kazuto Endo,Tomonori Ishigaki,Masato Yamada 한국폐기물자원순환학회 2013 한국폐기물자원순환학회 학술대회 Vol.2013 No.2
Prediction method for the long-term chemical leaching amount from by-product/recycled materials such as waste concrete and steel slag and so on is necessary to widely promote their effective utilization and evaluate their environmental safety. Although there are the batch leaching tests and the column leaching test as the testing methods for evaluating the long-term leaching behavior, the leaching mechanism and the testing result compatibility in both tests has insufficiently been clarified yet. Thus, the prediction of the leaching behavior from the by-product/recycled materials used in actual civil works and their environmental safety evaluation are by no means certain. This paper shows the difference between the batch leaching tests and the column leaching tests in the chemical leaching behavior of Cu-slag. The batch leaching tests were conducted under liquid/solid ratio = 10, liquid = distilled water, stirring strength = 0, 30, or 120 rpm. After a certain elapsed time, the leaching solution was exchanged with the pure distilled water and then the stirring was restarted. The elapsed time was set at 1, 2, 4, 8, 16, 32 days. The column leaching tests were also conducted under the same conditions as those of the batch leaching tests in order to evaluate the effects of the pore distribution and the pore flow velocity in the Cu-slag column on the leaching behavior. In the column leaching tests, the effluent passing through the column was circulated as the influent (Fig. 1). The leaching duration in the column tests can be equivalent as that in the batch tests, so that the difference in the leaching behavior between the batch leaching tests and the column leaching tests may be dependent on the pore-scale heterogeneous flow and path generated in porous materials. Figure 2 shows the leaching rate evaluated from the batch leaching tests and the column leaching tests. In the same fluid velocity levels, the leaching rate in the column tests was larger than that in the batch tests. The leaching rate has been considered large with the fluid velocity. Although the fluid velocity generated by the stirring was the same as the flushing velocity on the surface of the Cu-slag in the batch tests, the fluid velocity in the column tests was enhanced because the permeant liquid was concentrated into the limited pore space in the Cu-slag column. Thus, the pore-scale heterogeneous flow and path generated in porous materials should be evaluated in order to clarify the compatibility between the batch leaching tests and the column leaching tests.
( Astryd Yiandila Dahlan Hiroki Kitamura ),( Yu Tian ),( Hirofumi Sakanakura ),( Takashi Yamamoto ),( Fumitake Takahashi ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 심포지움 Vol.2018 No.1
Incineration is major treatment method of municipal solid waste (MSW) in Japan to reduce volume and weight of the waste. In 2016, total MSW generation in Japan was about 43.17 million tons and around 80 % of MSW were combusted by incinerators. Bottom ash and fly ash are the main products from MSW 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 like dioxins. Although MSWI fly ash is fine particles and has been regarded as homogeneous in numerous previous researches, it has not been proved based on sufficient analysis in the micro-scale. Therefore, the objective of the study is to investigate particle-scale heterogeneity of fly ash, in particular heterogeneity among fly ash particles (interparticle heterogeneity). In this study, fly ash generated from a fluidized bed and stoker combustor were analyzed and compared. Surface elemental concentrations of each fly ash particles, measured by SEM-EDS, were used to analyze elemental heterogeneity among fly ash particles. In order to measure interparticle heterogeneity of inner matrices of fly ash particles, Japan leaching test 19th (JLT 19), which used hydrochloric acid as leaching medium with liquid-to-solid ratio of 33.3, were conducted to remove semi-soluble and soluble components of fly ash particles. For each sample of stoker incinerator fly ash, fluidized bed incinerator fly ash, and their insoluble residues of JLT 19, 100 particles were measured. Elemental binary molar ratio among Ca, Si and A1 were plotted in ternary diagrams to visualize interparticle heterogeneity. Major elements in fly ash particles generated from both incinerators have large distributions of elemental concentrations. On the other hand, there are not significant differences of elemental concentration distribution between both incinerator fly ash excluding calcium (Ca). Ca concentration in fluidized bed combustor is relatively higher than stoker combustor. Ca concentration distribution of fluidized bed incinerator fly ash is wider than that of stoker combustor fly ash. Elemental ratios among Ca, Si and Al, plotted in triangular graphs, clearly shows that fly ash particles produced from stoker combustor concentrated in Ca area. On the other hand, fly ash of fluidized bed incinerator are dispersed more to Ca and Si sides as shown in Figure 1. This means that fly ash of fluidized bed incinerator has larger interparticle elemental heterogeneity compared to stoker combustor fly ash although different waste streams might have caused this difference to some extent. Fly ash residues of JLT 19 are relatively concentrated in Si area compared to fly ash particle surfaces. The authors expected that most of residue samples would be plotted near Si area. However, some particles spread to Ca and A1 areas. Moreover, fly ash of stoker incinerator has more scattered plots than fluidized bed incinerator fly ash. In contrast to interparticle elemental heterogeneity on fly ash surfaces, insoluble inner matrices of stoker incinerator fly ash have larger interparticle heterogeneity than fluidized bed incinerator fly ash. These analysis results would be useful for not only evaluation of fly ash heterogeneity but also considerations of fly ash formation mechanisms.