Chiou-Liang Lin

Effects of dissolved oxygen on dye removal by zero-valent iron.

Effects of dissolved oxygen concentrations on dye removal by zero-valent iron (Fe(0)) were investigated. The Vibrio fischeri light inhibition test was employed to evaluate toxicity of decolorized solution. Three dyes, Acid Orange 7 (AO7, monoazo), Reactive Red 120 (RR120, diazo), and Acid Blue 9 (AB9, triphenylmethane), were selected as model dyes. The dye concentration and Fe(0) dose used were 100 mg L(-1) and 30 g L(-1), respectively. Under anoxic condition, the order for dye decolorization was AO7>RR120>AB9. An increase in the dissolved oxygen concentrations enhanced decolorization and chemical oxygen demand (COD) removal of the three dyes. An increase in gas flow rates also improved dye and COD removals by Fe(0). At dissolved oxygen of 6 mg L(-1), more than 99% of each dye was decolorized within 12 min and high COD removals were obtained (97% for AO7, 87% for RR120, and 93% for AB9). The toxicity of decolorized dye solutions was low (I(5)<40%). An increase in DO concentrations obviously reduced the toxicity. When DO above 2 mg L(-1) was applied, low iron ion concentration (13.6 mg L(-1)) was obtained in the decolorized AO7 solution.

Metal catalysts supported on activated carbon fibers for removal of polycyclic aromatic hydrocarbons from incineration flue gas.

The aim of this research was to use metal catalysts supported on activated carbon fibers (ACFs) to remove 16 species of polycyclic aromatic hydrocarbons (PAHs) from incineration flue gas. We tested three different metal loadings (0.11 wt%, 0.29 wt%, and 0.34 wt%) and metals (Pt, Pd, and Cu), and two different pretreatment solutions (HNO(3) and NaOH). The results demonstrated that the ACF-supported metal catalysts removed the PAHs through adsorption and catalysis. Among the three metals, Pt was most easily adsorbed on the ACFs and was the most active in oxidation of PAHs. The mesopore volumes and density of new functional groups increased significantly after the ACFs were pretreated with either solutions, and this increased the measured metal loading in HNO(3)-0.48% Pd/ACFs and NaOH-0.52% Pd/ACFs. These data confirm that improved PAH removal can be achieved with HNO(3)-0.48% Pd/ACFs and NaOH-0.52% Pd/ACFs.

Waste-gasification efficiency of a two-stage fluidized-bed gasification system

This study employed a two-stage fluidized-bed gasifier as a gasification reactor and two additives (CaO and activated carbon) as the Stage-II bed material to investigate the effects of the operating temperature (700°C, 800°C, and 900°C) on the syngas composition, total gas yield, and gas-heating value during simulated waste gasification. The results showed that when the operating temperature increased from 700 to 900°C, the molar percentage of H2 in the syngas produced by the two-stage gasification process increased from 19.4 to 29.7mol% and that the total gas yield and gas-heating value also increased. When CaO was used as the additive, the molar percentage of CO2 in the syngas decreased, and the molar percentage of H2 increased. When activated carbon was used, the molar percentage of CH4 in the syngas increased, and the total gas yield and gas-heating value increased. Overall, CaO had better effects on the production of H2, whereas activated carbon clearly enhanced the total gas yield and gas-heating value.

Effect of Cu species on leaching behavior of simulated copper sludge after thermal treatment: ESCA analysis

The aim of this study is to evaluate the efficiency of thermal treatment on residual copper sludge after separation treatment. The toxicity characteristic leaching procedure (TCLP) concentration, pattern distribution and possible Cu species of simulated copper sludge were analyzed. Parameters such as different reaction time and temperature are also discussed in this study. The TCLP leaching results showed that the TCLP concentration of Cu in thermally treated simulated copper sludge decreased (T=900 degrees C) as the reaction time increased to 4 h. The sequential extraction results showed that the main fraction of raw simulated copper sludge was carbonate. When temperatures were 500 and 700 degrees C, the main fraction of thermally treated simulated copper sludge was also carbonate. The percentage of Fe-Mn oxides and residue increased when T=900 degrees C. Electron Spectroscopy for Chemical Analysis (ESCA) showed that the possible Cu species of raw simulated copper sludge was Cu(OH)(2). The main possible Cu species of thermally treated simulated copper sludge were CuO and Cu(2)O when T was 500 and 700 degrees C, respectively. CuO, Cu(2)O, and Cu(3)O(2) were the possible Cu species in thermally treated simulated copper sludge when T=900 degrees C.

Effects of bed material size distribution, operating conditions and agglomeration phenomenon on heavy metal emission in fluidized bed combustion process.

This study investigates the effects of the bed material size distribution, the operating conditions and the agglomeration/defluidization phenomenon on the heavy metal pollutant emissions in the combustion process. After defluidization, the emission concentration of heavy metals increased, because Na may form a low melting eutectic material that enhances bed material adherence. The emission of Cd increased when the feed simulated urban residues contained sodium; however, the presence of Na had no significant effect on the emission of Cr. Furthermore, the Cd emission concentration was low when the material had a Gaussian distribution; however, the decreases in the Cd emission when the bed material had narrow, binary or flat distributions were not significant. The heavy metal Cr showed the same trend. In addition to the operating parameters, the bed material size distribution may influence the heavy metal emissions during combustion processes.

Copper emission during thermal treatment of simulated copper sludge

This study evaluates Cu emissions in air-particulate and gas phases during thermal treatment of simulated copper sludge by a rotary kiln. Influences of operating parameters, including treatment temperature (400–700 °C), rotary speed (0.89–2.00 rpm) and copper content in sludge (1% to 5% by weight) on copper emissions were investigated. The toxicity characteristic leaching procedure (TCLP) and scanning electron microscopy (SEM) were also conducted to evaluate copper leaching and the surface structure of thermally treated sludge, respectively. The results indicated that (1) low Cu emissions in air-particulate and gas phases were associated with the two operating conditions of 400–500 °C at 0.89–1.39 rpm and 600–700 °C at 2.00 rpm; (2) temperatures and rotary speeds did not affect gaseous copper emission, except for the operating condition of 400 °C at 2.00 rpm; (3) rising copper content of sludge at 600 °C and 2.00 rpm increased the particulate copper emission, but not the gaseous copper emission; (5) the TCLP copper leaching concentrations of sludge treated at 400 °C were obviously higher than those treated at 500–700 °C; however, all of the thermally treated products agreed with the Taiwan EPA TCLP regulations.

Effect of operating conditions on emission concentration of PAHs during fluidized bed air gasification of biomass

With the concern of future energy use, hydrogen is taken as an important role in energy alternatives. In addition, biomass air gasification by using fluidized bed is an efficient and advanced method for hydrogen production. Despite of energy product generation, some pollutants such as PAHs easily formed in gasification process because of tar decomposition. Accordingly, this study provides a fundamental work of emission behavior of PAHs generated under different operating conditions such as temperature, air factor, and addition of catalysts. The experimental result shows the emission concentration of PAHs decreases with the operating temperature increases, but PAHs increases with increasing of air factor. Besides, addition of CaO resulting a reduce influence on PAHs emission, but Al2O3 added in fluidized bed cause bimodal particle size segregate and reduce fluidized bed quality that leads PAHs formation during biomass air gasification.

Determination of the Pb, Cr, and Cd distribution patterns with various chlorine additives in the bottom ashes of a low-temperature two-stage fluidized bed incinerator by chemical sequential extraction

A novel low-temperature two-stage fluidized bed (LTTSFB) incinerator has been successfully developed to control heavy-metal emissions during municipal solid waste (MSW) treatment. However, the characteristics of the residual metal patterns during this process are still unclear. The aim of this study was to investigate the metal patterns in the different partitions of the LTTSFB bottom ash by chemical sequential extraction. Artificial waste was used to simulate the MSW. Different parameters including the first-stage temperature, chloride additives, and operating gas velocity were also considered. Results indicated that during the low-temperature treatment process, a high metal mobility phase exists in the first-stage sand bed. The main patterns of Cd, Pb, and Cr observed were the water-soluble, exchangeable, and residual forms, respectively. With the different Cl additives, the results showed that polyvinyl chloride addition increased metal mobility in the LTTSFB bottom ash, while, sodium chloride addition may have reduced metal mobility due to the formation of eutectic material. The second-stage sand bed was found to have a lower risk of metal leaching. The results also suggested that, the residual ashes produced by the LTTSFB system must be taken into consideration given their high metal mobility.

Evaluating the Relationships between Pb Species and Leaching Properties in Simulated MSWI Fly Ash with Thermal Treatment by ESCA

AbstractThe aim of this study was to develop a fundamental understanding of the association between lead (Pb) species and leachability behavior in the simulated municipal solid waste incinerator (MSWI) fly ash during the thermal treatment process. Two main factors that influence this process, temperature and the carbon content in the simulated ash, were also studied. In the sequential extraction results, the main distribution pattern of Pb in treated simulated ash was carbonate fraction with different temperatures when the carbon content was 3.5%. The chief fraction of the raw simulated ash (carbon content=0%) was carbonate and that of raw simulated ash when carbon content was increased was Fe-Mn oxide Electron spectroscopy for chemical analysis (ESCA) results showed that Pb (element) in treated simulated ash could increase the toxicity characteristic leaching procedure (TCLP) concentration of Pb when temperatures reached 700°C. With a temperature of 900°C, PbSiO3 was present in the treated simulated ash ...

Experimental investigation of synthetic gas composition in a two-stage fluidized bed gasification process: effect of activated carbon as bed material

ABSTRACT In this study, a two-stage fluidized bed gasifier was used to investigate the effect of the equivalence ratio (ER) and steam/biomass ratio (S/B) on the synthetic gas distribution while activated carbon (AC) was added as the bed material in secondary gasifier (Stage II). The experimental results showed that when the empty bed (without the bed material) was used for the Stage II reaction, the hydrogen (H2) content in the synthetic gas emitted from the Stage II reactor was 2–3 mol% higher than that from the first-stage gasifier (Stage I). It was supposed that using the Stage II reactor prolongs the reaction time and thereby increases the H2 production. Besides, when the AC was added in the Stage II gasifier, the H2 concentration, the total gas yield, and gas heating value reached their maximum (30 mol%) when ER and S/B were 0.3 and 1.5, respectively.