Waste Disposal & Sustainable Energy最新文献

Oil-based drill cuttings (OBDCs) are hazardous wastes generated during shale gas exploration, and the rapid, efficient and safe disposal methods for OBDCs have attracted the attention of many researchers. Plasma pyrolysis technology is widely used in solid waste treatment due to its extremely high temperature and reaction activity. A laboratory-scale thermal plasma pyrolysis system was built to investigate the plasma pyrolysis mechanism of simulated OBDCs. The thermal decomposition characteristics of OBDCs were studied by thermogravimetric-derivative thermo gravimetric-differential scanning calorimetry (TG-DTG-DSC) analysis in the range of 50–1300 °C. The thermal decomposition process of OBDCs was divided into the following four stages: evaporation of water and light oil, evaporation and decomposition of heavy oil, carbonate decomposition, and phase change reaction from solid to liquid. The effects of the oil ratio, water content, and water/oil (W/O) ratio of OBDCs on the composition and gas selectivity of pyrolytic gas were investigated. The results show that thermal plasma can crack the mineral oil in the OBDCs into clean gases such as H₂, CO and C₂H₂, while water can promote the decomposition of the heavy oil molecules and enhance the H₂ production. The energy consumption model calculation for the pyrolysis and melting of OBDCs shows that the highest energy utilization and the lowest molar energy consumption of H₂ were achieved at a W/O ratio of 1:4. Based on the thermal plasma pyrolysis system used in this study, the commercial application prospects and economic benefits of the plasma pyrolysis of OBDCs were discussed.

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Extensive use of fossil fuel has led to an increase in solid and gaseous particulates in the environment, which in turn necessitated newer, effective, and economical control strategies to abate pollutants, particularly gaseous pollutants. In the current research work, focus has been placed on utilizing industry wastes to adsorb nitrogen oxides present in diesel engine exhaust, which is pre-treated by plasma. Sampled exhaust from a 5 kW diesel generator is exposed to discharge plasma where the oxidation of nitric oxide to nitrogen dioxide occurs, which is then made to flow through another reactor filled with industry wastes drawn from agriculture, foundry, utility, marine industry, etc., comprising mulberry waste, rice husk, wheat husk, areca nut husk, sugarcane bagasse, coffee husk, foundry sand, lignite ash, red mud, and oyster shells. While the adsorption of nitrogen dioxide was observed in all the wastes, reduction of nitric oxide was observed in metallic compound-based industry wastes. At about 184 J/L, specific energy plasma cascaded industrial waste red mud yielded 98% NO_x removal efficiency, and that with agriculture rice husk waste yielded 53% NOx removal. TiO₂/Fe₂O₃ present in industry wastes might have exhibited photo-catalysis in visible light resulting in the possible reduction of NO. A new pathway for recycling the waste can be expected through nitrogen dioxide adsorption, and the results are further discussed with respect to plasma-alone and cascaded plasma adsorbent systems.

The present research work aims to explore the potency of piranha solutions at the best-optimized concentrations, i.e., 40% and 30% to reduce the recalcitrant and heterogeneous structure of wheat straw, and the treated wheat straw was denoted as WS40 and WS30. The effect of pretreatment on wheat straw was determined by anaerobic digestion (AD) in a batch mode, followed by the analysis of soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFAs). After pretreatment, the surface fibers shattered and detached, showing a distorted surface of wheat straw. An increase in the crystallinity of wheat straw after pretreatment was also observed due to the removal of amorphous cellulose and lignin. Enhancement in methane yield was obtained on the 9th day, which was 103±6.92 and 99.33±0.57 mL/d for WS40 and WS30, respectively. Displaced water measurement revealed that the pretreatment of wheat straw minimized the hydrolysis period by 14 days. It also improved the methane yield by 2.65 (WS40) and 2.45 (WS30) fold in comparison with the control which yielded 35.66 mL/d methane on the 23rd day. The modified Gompertz model (MGM), logistic function model (LFM) and transference function model (TFM) adequately described the degradation process and explained the kinetic behavior of the cumulative methane yield. Among the three models, MGM was found to fit best for the methane yield of WS40 and WS30.

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This study was carried out in a full-scale (50 t/d) rotary kiln incinerator to explore the removal characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) by different units of air pollution control devices (APCDs), and special interest was focused on the “memory effect” phenomenon of PCDD/Fs in the wet scrubber (WS), which usually caused an undesirable rise in PCDD/F emission concentrations. The general removal efficiency of PCDD/Fs by APCDs was 99.4% (from 14.11 at exhaust heat boiler (EHB) outlet to 0.09 ng I-TEQ/Nm³ at stack) under medical waste (MW) incineration condition, and 99.2% (from 19.91 to 0.16 ng I-TEQ/Nm³) under hazardous waste (HW) incineration condition. The PCDD/F concentrations in flue gas decreased along the APCDs except for WS, in which the “memory effect” was observed. In detail, WS largely increased the I-TEQ concentration of gas-phase PCDD/Fs from 0.047 to 0.188 ng I-TEQ/Nm³ in the flue gas, and the concentration of particulate-phase PCDD/Fs increased from 0.003 to 0.030 ng I-TEQ/Nm³. In addition, this study found that phase migration promoted the accumulation of PCDD/Fs in scrubbing water, and the flow entrainment phenomenon played a great role in causing the “memory effect”. The PCDD/F concentrations of fly ash collected from cyclone and fabric filter (FF) were as high as 4.23 and 6.99 ng I-TEQ/g, respectively, which had exceeded the national landfill limitation (3 ng I-TEQ/g) in China. The system balance calculations revealed that APCDs promoted the migration of PCDD/Fs from the gas-phase to the particulate-phase, which caused fly ash to be the main carrier of PCDD/Fs and led to excessive emissions. The results of this study can contribute to the optimized design of combustion conditions and system cleaning for controlling PCDD/F emissions from rotary kiln incinerators.

One of the most misunderstood technologies in some parts of the world and widely adopted technologies in others is the recovery of energy and materials by the controlled combustion of post-recycling wastes. This technology is commonly called waste-to-energy, or simply WTE. After all possible efforts for recycling or composting wastes, there remains a large post-recycling fraction that is either landfilled or used as fuel in WTE power plants that also recover metals and minerals. Several nations, e.g., Switzerland, Japan, Sweden, Belgium, Denmark, and Germany, have succeeded in phasing out landfilling by processing all theãir post-recycling municipal solid wastes (MSW) in WTE power plants. This paper reviews the evolution and importance of WTE in the twenty-first century, with special focus on the world’s largest economies: the EU, US, and China.

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The pyrolysis of poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) catalyzed by five alkaline earth metal-based minerals/wastes, namely calcined dolomite, calcite, magnesite, calcium carbide slag (CCS), and ophicalcitum, was conducted by a pyrolyzer-gas chromatography-mass spectrometer (Py-GC-MS) with the objective of recovering benzenes-enriched oil. Compared with magnesium-based catalysts and pure CaO, the calcium-based catalysts with calcium hydroxide as the main component performed better catalytic effect, which could simultaneously promote the hydrolysis of ester products and the decarboxylation of aromatic acids after hydrolysis. For PET, the addition of solid base catalysts at 600 °C promoted the complete degradation of aromatic acids and aryl esters, which accounted for 32.6% and 30.7% of the pyrolysis oil, respectively. The content of benzene in oil increased from 8.8% to 31.7%–78.8%. For PBT, the addition of solid base catalysts at 600 °C completely decomposed the aromatic acids, which accounted for 67.1% of the pyrolysis oil, and the content of benzene in oil increased from 12.3% to 34.5%–81.0%. During the deoxygenation of polyester pyrolysis products, increasing temperature was more effective for the decomposition/conversion of acetone and tetrahydrofuran, while increasing the alkalinity of the reaction environment contributed to the rapid decrease in acetaldehyde and aryl ketone contents.

Hydrothermal carbonization (HTC) technologies for producing value-added carbonaceous material (hydrochar) from coal waste and sewage sludge (SS) waste might be a long-term recycling strategy for hydrogen storage applications, cutting disposal costs and solving waste disposal difficulties. In this study, hydrochars (HC) with high carbon content were produced using a combination of optimal HTC (HTC and Co-HTC) and chemical activation of coal tailings (CT), coal slurry (CS), and a mixture of coal discard and sewage sludge (CB). At 850 °C and 800 °C, respectively, with a KOH/HC ratio of 4:1 and a residence time of 135 min, activated carbons (ACs) with the highest Brunauer–Emmett–Teller specific surface (S_BET) of 2299.25 m²g^{− 1} and 2243.57 m²g^{− 1} were obtained. The hydrogen adsorption capability of the produced ACs was further studied using gas adsorption isotherms at 77 K. At 35 bars, the values of hydrogen adsorbed onto AC-HCT (AC obtained from HTC  of CT), AC-HCS (AC obtained from HTC of CS), and AC-HCB (AC obtained from HTC of the blending of coal discard (CD) and SS) were approximately 6.12%, 6.8%, and 6.57% in weight, respectively. Furthermore, the cost of producing synthetic ACs for hydrogen storage is equivalent to the cost of commercial carbons. Furthermore, the high proportion of carbon retained (>70%) in ACs synthesized by HTC from CD and SS precursors should restrict their potential carbon emissions.