Waste Disposal & Sustainable Energy最新文献

The production of biohydrogen from biological processes is cleaner and more sustainable than that of fossil fuel-based hydrogen. The drive for cleaner and sustainable energy sources is an important facet of the bioeconomy. Based on these findings, this paper aimed to examine the significance and impact of biohydrogen on the bioeconomy. These bioprocessing strategies are primarily biophotolysis, fermentation and bio-electrolytic systems. Considering that biological processes are slow compared to other thermochemical production processes, production volumes cannot match that of the latter. The inherently slow nature of biochemical reactions taking place in living organisms is a challenge that puts biohydrogen at a disadvantage. Biological processes are also very sensitive to temperature and pH, thereby requiring more intricate process monitoring and control. To obtain equivalent volumes of biohydrogen compared to production strategies, larger and more intricate facilities would be needed, implying more cost implications. It is surmised that biohydrogen will continue to play an important role in the drive for a sustainable bioeconomy despite the current challenges it faces.

Metal recovery from bottom ash was deemed to be significant to achieve a higher stability of bottom ash and recycle valuable extractable metals. In China, the existing rugged industrial production ignores the actual metal distribution and thus fails to exploit the utilization potential of recoverable metals in bottom ash. Based on these findings, this work was proposed to obtain a comprehensive and in-depth study on the recoverability of metals in bottom ash. First, the particle size distribution and elemental composition of the bottom ash were analyzed. Then, complete information on the recoverable metals in bottom ash fractions with different sizes was obtained by washing, sorting, crushing, density separation and XRF (X Ray Fluorescence) analysis. The results showed that the smaller than 5 mm fraction accounted for up to 60% of the bottom ash, and the 5–20 mm fractions accounted for about 15%. The material characterization revealed that the contents of recoverable Fe, stainless steel, Al and Cu in bottom ash were averagely 9.01%, 0.136%, 0.78% and 0.08%, respectively. About 50% of Fe, 68% of Al, 61% of Cu, and 22% of stainless steel were distributed in smaller than 10 mm fraction. Particularly, Fe was evenly distributed among 0–2 mm, 2–5 mm, 5–10 mm fractions, and the content was between 5.41% and 7.5%. Non-magnetic stainless steel was mainly distributed in 20–40 mm and larger than 40 mm fractions. The highest share of Al was present in the fractions between 5 mm and 20 mm, accounting for 48% of the total aluminum. About 45.6% of the Cu was enriched in the 5–10 mm fraction. However, the Zn content was less than 0.01%. This work provides an in-depth understanding and information on metal recovery as well as promisingly guide ash utilization.

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The challenges in the current energy consumption patterns and demand–supply gap are driving the need to develop commercially viable and sustainable alternative fuels that are eco-friendly and efficient. Given the existing alternatives, hydrogen is regarded as the ultimate carbon-less clean and green fuel with high energy density. Considerable efforts are being made to develop catalysts/photo-catalysts for the efficient production of hydrogen from abundantly available water resources via water-splitting process. In this review, the photocatalytic activity of tin oxide-based hybrid photocatalytic materials for increased hydrogen production has been studied. The existing bottlenecks and proposed solutions have also been discussed.

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Fly ash, as a byproduct of municipal solid waste incineration, contains several kinds of pollutants, especially dissolvable salts that cause a severe challenge for fly ash disposal. Washing combined with cement kiln co-processing for fly ash disposal has been applied in China. After washing, the wastewater was evaporated to produce fly ash salt (FAS). In this study, FAS was mixed the KCl and LiCl to be used as molten chloride salt for energy storage material. Twenty-three types of molten salts with various ratios of FAS-KCl-LiCl were evaluated. Thermophysical properties (melting point and latent heat) and thermal stability of these salts were characterized. The increase in FAS fraction decreased the latent heat of molten salts. Among the tested samples, the best compatibility ratio of FAS:KCl:LiCl was 10:50:40 (%, in weight), with latent heat of 108.7 J/g and melting point of 333 °C. This molten salt also showed good thermal stability after 1–13 h of thermal experiments, and the mass loss was less than 2% after 5 heating cycles at 600 °C. By corrosion test, FAS-KCl-LiCl (10:50:40, % in weight) could be more safely used in vessels made of nickel-based alloy, but it might cause corrosion risk for stainless steel.

The coal-fired flue gas spraying wastewater is a kind of refractory mixed wastewater with poor biodegradability. In this study, the degradation of model coal-fired flue gas spraying wastewater was studied by using discharge free radicals produced by double-dielectric barrier discharge. The degradation rate of pollutants, chemical oxygen demand removal rate and other indicators were detected, and the influence of different conditions on the degradation effect was analyzed. The optimal parameters are as follows: residence time 120 min, input power 170.0 W, initial pH value 3.79, and aeration rate 1.8 mL/min. The initial concentrations of acetone, formaldehyde, chloroform, benzene and toluene were 100, 100, 100, and 100 mg/L, respectively. Furthermore, it is proved that the discharge area is independent of the degradation rate. Through the analysis of the mechanism, it is found that ·OH is an important factor affecting the degradation rate of pollutants in model coal-fired flue gas spraying wastewater.

Energy is a vital input to the economic growth and development of any economic sector. One of the best-known and longest-used sources of renewable energy is biomass. Generating energy from forest resources opens the opportunity for  woodlands and other tree areas that can offer natural, environmentally-friendly energy to meet the needs of distant regions that would help protect  forest resources. On the other hand, the increases in wastewater for brewery treatment plants could result in a large amount of brewery wastewater sludge (BWWS) generation, which requires proper management before disposal. This research aimed to characterize and produce briquette fuel from the combination of sawdust and BWWS brewery using molasses as a binder. The Composite Briquitte was produced by varying the mixing ratio of sawdust to BWWS 100:0, 90:10, 80:20, 70:30, and 60:40, using 0 to 10% molasses as a binding agent. The proximate, ultimate and calorific value analyses of all composite briquettes were performed according to the American Society Testing of Material standard. It was observed that moisture content increased from 6.2% to 10.2%, fixed carbon decreased from 64.5% to 50.9%, and the caloric value decreased from 24.8 MJ/kg to 14.8 MJ/kg as the proportion of BWWS mixture in composite briquette increased. The binder ratio, hold time, and pressure effects and their interaction on the density and durability index of briquettes were investigated. The findings showed that the optimum density and durability indexes were 1019.99 kg/m³ and 97.274%, respectively, for the binder of 10%, hold time of 4.126 min and pressure of 6.076 MPa. It was concluded that the composite briquettes produced from 10%–20% BWWS proportion sawdust and the sawdust alone have high calorific values ranging from 20.9 MJ/kg to 24.8 MJ/kg, fixed carbon is from 61.18% to 64.5%, ash content is from 4.65% to 10.1%, volatile matter is from 20% to 24.85%, and moisture content is from 6.2% to 8.32%, which is guaranteed to be used  for household cooking.

Municipal solid waste (MSW) is a carbon–neutral energy source and possesses a moderate heating value; hence, it can be used as an alternative fuel for coal. To use high ash and high sulfur Indian coals efficiently, a techno economic analysis is performed for electricity generation using supercritical and subcritical based steam turbines operating in the oxy-fuel co-combustion mode of MSW with Indian coals. The impact of the capture of direct and indirect greenhouse gasses such as CO₂, NO_x and SO_x on the net thermal efficiency of the power plants is assessed. The supercritical based steam turbine achieved a higher net thermal efficiency by 8.8% using MSW based feedstock compared to sub-critical conditions. The co-combustion mode reduced the levelized cost of electricity (LCOE) by 48–73 $/MWh. Techno-economic analysis for sulfur removal in coal using ultrasonication technology has not yet been reported in the literature. The incorporation of an ultrasonicator (a pre-combustion sulfur remover) and a duct sorbent injector (a post-combustion SO_x absorber) increased the LCOE by 1.39–2.75 $/MWh. In high sulfur coals, the SO_x emissions decreased from 224.79 mg/m³ to 9.2 mg/m³.

Gasification of biomass produces a syngas containing trace amounts of viscous hydrocarbon tar, which causes serious problems in downstream pipelines, valves and processing equipment. This study focuses on the use of tire-derived pyrolysis char for tar conversion using biomass tar model compounds representative of tar. The catalytic decomposition of tar model compounds, including methylnaphthalene, furfural, phenol, and toluene, over tire char was investigated using a fixed bed reactor at a bed temperature of 700 °C and 60 min time on stream. The influence of temperature, reaction time, porous texture, and acidity of the tire char was investigated with the use of methylnaphthalene as the tar model compound. Oxygenated tar model compounds were found to have higher conversion than those containing a single or multi-aromatic ring. The reactivity of tar compounds followed the order of furfural > phenol > toluene > methylnaphthalene. The conversion of the model compounds in the presence of the tire char was much higher than tar thermal cracking. Gas production increased dramatically with the introduction of tire char. The H₂ potential for the studied tar model compounds was found to be in the range of 40%–50%. The activity of tire char for naphthalene removal was compared with two commercial activated carbons possessing a very well-developed porous texture. The results suggest that the influence of Brunauer-Emmett-Teller surface area of the carbon on tar cracking is negligible compared with the mineral content in the carbon samples.

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In this study, the method of fluidized incineration and water washing to recover hydrogen fluoride (HF) was proposed to dispose of high fluorine-containing organic waste. The resource utilization of the waste was investigated in a fluidized bed incinerator with a disposal capability of 10 t/d. The evolution characteristics of fluorine, operation conditions of the incineration system, absorption coefficient for HF by water washing, and HF corrosion during combustion were assessed. The results showed that HF and fluorocarbons were detected as the initial gaseous fluorides released during combustion. The release of HF could be divided into three stages, in which HF was generated from the volatilization of HF in the waste and the hydrolysis of fluorine in water-soluble salts (60–220 °C), oxidative decomposition of fluorinated organic components and residual carbon (220–800 °C), and hydrolysis of insoluble fluorinated inorganic minerals (800–1000 °C). Fluorocarbons could be destroyed through reactions with free radicals H, O, and OH or through single-molecule decomposition. Enhancing the temperature in the furnace and increasing the content of oxygen and hydrogen in the incineration materials were conducive to reducing the generation of fluorocarbons. By sampling and analyzing the bottom slag, bag filter ash and exhaust gas during the field test, the relevant pollutant discharge could meet the national emission standards. The waste heat utilization of high-temperature flue gas and the recovery of hydrofluoric acid and hydrochloric acid were realized. In the recovery of HF by water washing, the total absorption coefficients for 1# to 4# packed absorbers were 52.38 kg/(h m²), 39.96 kg/(h m²), 5.98 kg/(h m²) and 3.89 kg/(h m²), respectively. In the actual operation, alumina showed good corrosion resistance to high-temperature HF and could be used as bed materials or refractory materials. Low-temperature corrosion of HF occurred in the quenching heat exchanger, which was damaged after 6 months of continuous operation. High-temperature corrosion of HF occurred in the waste heat boiler. No significant corrosion was observed in the 24 months of operation.