Cleaner Chemical Engineering最新文献

The alumina industry requires a material capable of reducing the high levels of iron and alkalinity in bauxite liquid-residue in an eco-efficient manner while producing fewer by-products. This study looked at the efficacy of acid-activated kaolin (AAK) and acid-activated bentonite (AAB) in reducing the high pH value and iron content of bauxite liquid-residue in a single treatment step. The bauxite residue, AAB, and AAK were characterised using XRD, XRF, and FTIR techniques. A batch adsorption study with varying contact times and adsorbent types was conducted, and the results were analysed using adsorption kinetics and isotherm studies. The results showed that AAK and AAB could effectively remove 88% to 94% of the total iron in the bauxite liquid-residue. Similarly, the initial pH value of the bauxite liquid-residue (9.93 ± 0.13) was reduced by about 3.32% with AAK and 4.53% with AAB, respectively. Thus, batch adsorption studies revealed that adsorption capacity was strongly pH dependent, and the type of adsorbent had an effect on the reduction of iron and pH value in the bauxite liquid-residue. The AAB was found to be more effective than AAK in lowering the high pH value and iron content of the bauxite liquid-residue.

Studies on alternative and renewable fuels are maintaining due to the ever-decreasing of petroleum usage and also the environmental pollution that it has created. Alternative fuels, especially renewable fuels are one of the most emphasized issues because renewable energy sources are environmentally friendly, unconsumable and easily degradable in the environment. In this study, biodiesel was obtained from safflower. The biodiesel of safflower oil was mixed with propanol at different ratios and tested as a diesel engine fuel. The effects of both biodiesel and propanol addition on engine performance, combustion parameters and pollutant exhaust emissions have been experimentally tested. The main important point of the presented study is to detect the effects of higher ratios of pure diesel fuel in diesel engines by utilizing the positive sides of a light alcohol, the propanol. The engine performance, specific fuel consumption and emission values of the biodiesel and propanol blended fuels did not show a significant difference compared to the diesel. In the loaded cases, the combustion parameters for all test fuels were obtained in a similar manner. Peak values of HRR in higher engine loads of blend fuels with high propanol were a bit higher. It is seen that there is a decrease in NOx emissions. Safflower biodiesel and propanol mixtures can be used as alternative fuels by adding to diesel fuel in certain amounts.

In this study, biodiesel production with canola oil and methanol in the presence of dolomite catalyst was examined in a multimode Enhanced Microwave System (EMS) with simultaneous cooling worked under constant, continuous microwave (MW) power and isothermal conditions. The experiments were carried out in the EMS utilizing the "one variable at a time" method to estimate optimum values of five experiment parameters named methanol-to-oil molar ratio (n_m/n_o), amount of catalyst (% wt of oil), temperature (T,°C), reaction time (t, min) and absorbed MW power (P_a,W). The optimum values of these parameters were obtained as 9, 5%, 65°C, 120 min., 48 W, respectively. At the end of the study in EMS, an experiment was repeated in the Conventional Heating System (CHS) at the optimum conditions. Accordingly, it was found that the yield of biodiesel in EMS (99.1%) during the same period was 30.2% higher than in CHS (76%). Faster, higher-quality, and lower-cost biodiesel production was accomplished when compared to the CHS. Energy and production cost saving were accomplished by 58.2 % and production rate was increased by 30.4% in EMS. Furthermore, selective and homogenous heating effect on catalyst's local surface temperature and strong vibrational effect of MW on dipoles provided advantages in terms of catalyst activity and different methyl ester content. This showed that biodiesel with different properties can be produced using same oil in the EMS.

In this context, this study aims to reduce the harmful effects of coal combustion and to investigate the possibility of efficient use of Turkish lignite with high sulfur content. In this study, peroxide leaching process and accounts for approximately 35% of lignite reserves in Turkey total sulfur content of the garment was removed from lignite. For this purpose, the effect of H₂O₂ on 5%, 10%, 20%, and 30% solutions and H₂SO₄ on the sulfur removal using 0.05 N, 0.1 N, 0.15 N, and 0.2 N solutions separately and together were investigated. According to the results, increasing the H₂O₂ concentration from 5% to 30%, the total sulfur content of the coal sample was removed by approximately 75%. When 0.1 N H₂SO₄ and H₂O₂ were used together, about 93% of sulfur removal was realized. The originality of the study is that scenario 8 of 12 situations is both high standard chemical exergy value used for economic analysis, low CO₂ emission value determined according to the life cycle assessment method used for environmental impact assessment, and 20-year operating cost calculated by current value estimation method. The lowest value indicates that 20% of H₂SO₄ is suitable for the establishment of the desulphurization plant with a yield of 63.2% from 200 kg of coal per hour. The highest exergy efficiency value was calculated as 8,01782E-06 for the 8th scenario. So the 8th scenario should be applied for the establishment of a desulfurization plant for E.L. Due to the results, this study is an economical method of sulfur removal. The addition of H₂SO₄ to H₂O₂ has a synergistic effect on sulfur removal. In this study, a new perspective has been developed by using exergy calculation and life cycle methods apart from conventional methods while determining the economy.

Second generation oxy-combustion and load following operations are accompanied by a significant (60–70%) reduction in combustor flue gas flow rates when compared to baseload operation. Understanding the aerodynamic influences on the fly-ash particle deposition characteristics during these novel operational scenarios are critical towards anticipating operational challenges. To fill this void, a novel Computational Fluid Dynamic (CFD) methodology in conjunction with an ash deposition module was used to model the outer ash deposition process coal during combustion of coal in AIR and O₂/CO₂ (70/30 vol%, OXY70) oxidizer compositions and the predictions were compared with measurements. The measured fly-ash particle size distributions (PSD) were employed as inputs to represent the particle Stokes numbers near the deposition surface accurately and the capture criterion was based on a recently proposed particle viscosity and kinetic energy (PKE) based formulation. Prediction sensitivities to the particle viscosity model and fly-ash PSD were also assessed. Deposition rate predictions in AIR were in excellent agreement with the measurements. The deposition rate enhancement (OXY70/AIR) across all scenarios were in the range 2.8–3.3 which was in reasonable agreement with the measured values of 2.1–2.4. Predicted capture efficiencies were nearly 100% across all scenarios. The calculations were repeated by employing the corresponding fly-ash composition information rather than the bulk-ash compositions and did not alter the predictions significantly. The study therefore supports the hypothesis that ash deposition rates in these novel operational scenarios are likely to be dominated by PKE.

This study represents a numerical investigation of the methane tri-reforming with full computational fluid dynamics and reaction mechanisms in an adiabatic fixed-bed reactor. A 2-D axisymmetric model over nickel-based catalysts is stablished to analyze the influence of relevant parameters. The attained results revealed that the feed composition, feed flow rate, inlet temperature, operating pressure and reactor geometry have important effects on the efficiency of the reactor. The observed temperature profile proves that the temperature peak increase with the inlet temperature. Moreover, the H₂/CO ratio increases with decrement of O₂/CH₄ and CO₂/CH₄ and increment of H₂O/CH₄. As the feed flow rate rises, the CH₄ conversion, CO₂ conversion and the syngas ratio reduce. One of the most attractive results is the correlation between the pressure and the reactor performance. When the pressure falls, whereas less O₂ is consumed, the CH₄ and CO₂ conversion rise due to the increase of the initial reaction rates. Finally, it is proved that the variations of the reactor diameter have a greater impact on the reactor performance compering with the reactor length.

A novel passive solar thermal storage with MgCl₂·6H₂O (Magnesium chloride hexahydrate) hydrated salt as porous media on sieve plates is proposed, in which the serpentine flow channel around sieve plates and several flowing slots in each salt layer are set to enhance the convective between the airflow and hydrated salt layer, besides, the porous copper foam embedded in hydrated salt bed will enlarge the thermal conduction in salt beds. Combining the Prout-Tompkins equation with Clausius-Clapeyron relation accounts for the kinetics characteristics of endothermic dehydration (i.e. hydrated salt loses its water content) in hydrated salt layer where the local thermal non-equilibrium occurs. The double energy equations together with Darcy relation are employed to describe the heat and flow in porous salt bed, and to analyze the effects of the salt bed structure, straight-shaped slots and porous copper foam in salt layer as well as the inlet airflow velocity on the conversion extent of MgCl₂·6H₂O salt and the heat storage characteristics in the passive solar thermal storage reactor during dehydration. In comparison to the salt layer without slot, more than 18% rise of conversion rate happens in the salt bed with n = 12 slots. The higher average conversion rate of MgCl₂·6H₂O, more uniform distribution and larger heat storage rate in the salt layer embedded with copper foam occur than that without, and the amount of heat storage rises slightly with the slot number above n = 6 for the current mode. The simulations accord with the published experiment data. All results can be considered into the promotion and application of the passive solar thermal storage of MgCl₂·6H₂O salt hydrate.

Following the recent outbreak of the COVID-19 pandemic caused by the SARS-CoV-2 virus, monitoring sewage has become crucial, according to reports that the virus was detected in sewage. Currently, various methods are discussed for understanding the SARS-CoV-2 using wastewater surveillance. This paper first introduces the fundamental knowledge of primary, secondary, and tertiary water treatment on SARS-CoV-2. Next, a thorough overview is presented to summarize the recent developments and breakthroughs in removing SARS-CoV-2 using solar water disinfection (SODIS) and UV (UVA (315–400 nm), UVB (280-315 nm), and UVC (100–280 nm)) process. In addition, Due to the fact that the distilled water can be exposed to sunlight if there is no heating source, it can be disinfected using solar water disinfection (SODIS). SODIS, on the other hand, is a well-known method of reducing pathogens in contaminated water; moreover, UVC can inactivate SARS-CoV-2 when the wavelength is between 100 to 280 nanometers. High temperatures (more than 56°C) and UVC are essential for eliminating SARS-CoV-2; however, the SODIS systems use UVA and work at lower temperatures (less than45°C). Therefore, using SODIS methods for wastewater treatment (or providing drinking water) is not appropriate during a situation like the ongoing pandemic. Finally, a wastewater-based epidemiology (WBE) tracking tool for SARS-CoV-2 can be used to detect its presence in wastewater.

SARS-CoV-2 has aroused drastic effects on the global economy and public health. In response to this, personal protective equipment, hand hygiene, and social distancing have been considered the most important ways to prevent the direct spread of the virus. SARS-CoV-2 would be possible survive in wastewater for a few days, leading to secondary transmission via contact with water and wastewater. Thus, the most economical and practical approaches for decentralized wastewater treatment are renewable energies such as the solar energy disinfestation process. However, as freshwater requirements increase and fossil fuels become unsustainable, renewable energy becomes more attractive for desalination applications. Solar photovoltaic, membrane-based, and electricity desalination technologies are becoming increasingly popular due to their lower energy requirements. Several aquatic environments could be benefitted from solar energy wastewater disinfection. Besides, utilizing solar energy during the day can inactivate SARS-CoV-2 to nearly 90%. However, conventional membrane-based desalination practices have also been integrated, including reverse osmosis (RO) and electrodialysis (ED). Several exciting membrane processes have been developed recently, including membrane distillation (MD), pressure-reduced osmosis (PRO), and reverse electrodialysis (RED). Such operations can produce clean and sustainable electricity from brine and impaired water, generally considered hazardous to the environment. As a result, neither PRO nor RED can produce electricity without mixing a high salinity solution (such as seawater or brine and wastewater, respectively) with a low salinity solution. Herein, we critically review the progress in applying renewable energy such as solar energy and geothermal energy for generating electricity from wastewater treatment and uniquely discuss the effects of these two types of renewable energy on SARS-CoV-2 in air and wastewater treatment. We also highlight the significant process made on the membrane processes utilizing renewable energy and research gaps from the standpoint of producing clean and sustainable energy. The significant points of this review are: (1) among various types of renewable energy, solar energy and geothermal energy have been predominantly studied for wastewater treatment, (2) effects of these two types of renewable energy on SARS-CoV-2 in air and wastewater treatment are critically analyzed, and (3) the knowledge gaps and anticipated future research outlook have been consequently proposed thereof.

Pollution has continued to be the source of elevated nutrient levels in catchment areas, causing eutrophic conditions that threaten human health. Adsorption has been seen as a cost-effective and simple process of removing and recovering nutrients from wastewater. Biomass feedstocks have received significant research interest in recent years on the production of biochar and its magnetized variants for wastewater treatment. However, there have been minimal studies on the use of paper waste sludge obtained from the recycling industry as a feedstock for biochar production used in wastewater treatment. Hence this study focused on the production of magnetic biochar composites as an adsorbent for nutrient removal and recovery from wastewater. Neat non-demineralized biochar and its magnetized variant were produced using paper waste sludge through co-pyrolysis at 450 °C and for the magnetized variant, the feedstock was synthesized using Fe³⁺ and Fe²⁺ salts. The biochar produced exhibited good structural and chemical properties suitable for adsorption. Hence further analysis was performed using MBC-SPS-450 for the removal of phosphorus (P), selenate (Se), and methylene blue (MB) from wastewater. The observed efficiencies for P, Se, and MB were 48.83, 58.43, and 5.92 mg g ^− 1 respectively. From the results obtained, the magnetized variant (MBC-SPS-450) displayed excellent adsorption efficiencies, lower loading requirements with an optimum loading of 5 g L ^− 1, easy removal from solution by magnets, and was regenerated with excellent adsorption efficiencies. These excellent results position paper waste sludge-derived biochar as a good and low-cost adsorbent for the removal and recovery of nutrients from wastewater with the added benefit that it is part of the recycling process.