Cleaner Chemical Engineering最新文献

The number of research activities to find alternative fuels for Internal Combustion Engines has increased tremendously in recent years, owing to depleting oil reserves and growing climate concerns. In this scenario, biodiesel is one of the few promising alternatives that can potentially replace conventional fuel. When vegetable oil is used for frying food items, it undergoes physiochemical changes. After a while, it is discarded as waste cooking oil (WCO) which can be used in the production of biodiesel. Since WCO is a degraded raw material, it is important to understand its effect on the quality of biodiesel produced in terms of engine performance and engine emission. In current research study, total polar matter (TPM) is considered as a measure of quality for waste cooking oil. Sunflower oil and palm olein were used in this study for comparison since both exhibit different fatty acid compositions. Among the properties considered in this study, the results found that the kinematic viscosity of the biodiesel gets highly affected by total polar matter content of waste cooking oil. Further, the study also identified correlations to predict the kinematic viscosity of biodiesel from total polar matter content of WCOs. The authors found no significant difference in engine performance during engine tests between the biodiesels produced from fresh oils and waste cooking oils. However, biodiesels produced from WCOs emitted slightly higher carbon monoxide than the biodiesel produced from fresh oils. On the contrary, nitric oxide and smoke emissions from biodiesels produced from waste cooking oils and fresh oils were similar. Even though waste cooking oil is a degraded feedstock, the biodiesel produced from it has no adverse effect on engine performance and emissions. Therefore, WCO oil can be considered as a promising feedstock in the sustainable production of biodiesel.

Petroleum refinery effluent (PRE) containing a high concentration of colloidal particles causing turbidity is a point source pollutant. There is currently no baseline for the residual concentration of colloids in industrial effluent. In the present study, the performance of land snail shells (LSS) characterized using FTIR and XRD techniques used for the treatment of PRE was investigated. The effluent collected from the outlet train of the industrial facility contains 220 NTU of turbidity corresponding to 520 mg/L of colloidal particles. Analysis of the industrial effluent yielded a COD to BOD ratio > 3.5 eliminating the option of a biological method of treatment. Coagulation-flocculation treatment of the PRE was carried-out following a standard nephelometric test. To clarify the applicability of LSS beyond removal efficiency, machine learning (ML), adsorption, and coag-flocculation kinetics were applied to investigate the treatment process. The predictive capacities of the ML models were compared using statistical metrics. The synergetic effects of operating variables were equally studied. The predicted optimum operating conditions of the treatment process were pH 6, dosage of 0.1 g/L, and a settling time of 30 minutes. The pseudo-second-order and coag-flocculation kinetics result confirmed the reduction of the colloidal particles that occurred via adsorption and inter-particle bridging mechanism. The flocculation outcome proved that the mixing regime 20 s⁻¹≤ G≤120 s⁻¹ promoted aggregation rate over breakage coefficient transcending to 90% removal efficiency. The finding shows that the stability of the finished water corresponds to the 23 mg/L threshold of residual colloidal particles, and 10NTU, which satisfied the EPA guideline for environmentally sustainable recovery.

Coal gasification fine slag (FS) is a solid waste of difficult-to-separate nature. In order to improve the reuse rate of coal gasification fine slag resources, so as to improve the value-added utilization and clean transformation for coal chemical industry, which is necessary to deeply study the composition characteristics and effective separation of FS. In this study, the dry pulverized coal gasification fine slag (DPFS) was divided into different particle sizes by wet screening, and the composition and structure characteristics of components with different particle sizes were investigated. Then a combined treatment method of airflow crushing and classification was used to separate DPFS. The results showed that the fixed carbon content, the ash composition, the micro morphology and the pore structure of FS were related to the particle size distribution. The fixed carbon content of particles with particle sizes ranging between 74–98 μm was the highest (about 39.98%), the particles with a size grade of 13–74 μm and larger than 98 μm was between 11.85 and 30.85%, The minimum fixed carbon content of 0–13 μm particle size is 8.69%. The microstructure of DPFS was composed of several relatively independent particle units with special morphology, including porous irregular particles, spherical particles, floccule, and the element contents of these particle units were very different. The residual carbon and ash components in the DPFS could be effectively separated and enriched in different products by airflow crushing and classification. When the grinding gas pressure was set to 0.5 MPa, the low carbon product with fixed carbon content of 4.99% and yield of 19.86% could be obtained. The mechanism of airflow crushing of FS showed that airflow crushing based on impact force and shear force could effectively separate the residual carbon and ash components, and greatly improve the separation and recovery rate of residual carbon. Therefore, the airflow crushing and classification has a good application prospect in the separation and enrichment of residual carbon of gasification fine slag.

This paper evaluated steam and CO₂-enhanced gasification of spent coffee ground (SCG) biomass, including energy and exergy aspects focusing on hydrogen production. The waste-to-hydrogen (WTH) conversion was performed via gasification (1000 °C) with a drop-tube-reactor investigating six different steam to biomass (SBR of 0.5, 0.8 and 1.2) and CO₂ to biomass (CO₂BR 0.09, 0.18 and 0.27) ratios. The syngas production indicated clear improvement against O₂/N₂ with an H₂ yield increase up to 69.21% and 18.32% for steam and CO₂ mediums. The energy and exergy analysis points out the 0.8 SBR as the optimum condition with 210% CGE and 48.05% exergy efficiency for H₂ production. As a strategy for carbon capture and usage, the medium with 0.27 CO₂BR provided a 28.52% exergy efficiency for H₂ production and reduced soot formation, showing a potential gasification medium for SCG. Results encourage waste-to-hydrogen prospection within circular economy principles, boosting circular economy principles in urban districts.

The goal of this research is to model/optimise aquaculture effluent (AQE) turbidity (TD) treatment with the aid of the extract of Garcinia kola (GKE) used as a coagulant. GKE was characterized via scanning methods. The research entails the optimisation of the process by RSM (response surface methodology) and Artificial Neural Network (ANN) techniques. The sorption component analysis of the coagulation-flocculation (CF) process of TD reduction from AQE was also analysed for its mechanism. SEM revealed that the GKE possesses uneven-sized, porous, and granular-shaped lumps on its surface. FTIR revealed that GKE had a high hydroxyl group which makes it soluble in aqueous media and contributes to attachment sites for the AQE pollutant particles. The process was effectively optimised (%TD = 74.23%, with TDS, COD, BOD, and colour reductions at 81.03%, 67.68%, 68.19%, and 76.89%, respectively) at optimum conditions of time = 30 min, pH = 2, and GKE dosage = 115 mgL⁻¹. The model generated was significant via ANOVA. The pseudo-second-order (PSO) sorption kinetic is the best fit model considering the error estimates. The predominant mechanism of the process is electrostatic interaction, liquid film diffusion and intraparticle diffusion. RSM(R²=0.9567)>ANN(R²=0.9491) for the models' prediction reliability. This study has shown that aquaculture effluent (AQE) turbidity (TD) treatment with the aid of the extract of Garcinia kola (GKE) can be optimised/modelled productively.

In this study pyrolysis of polypropylene (PP) was performed with and without cobalt oxide from 355 to 445 °C in inert conditions in an indigenously manufactured furnace. No oil was produced from non-catalytic reaction; however, the catalytic reaction resulted in production of oil in sufficient quantity. Optimum conditions for the maximum oil yield were explored and 100 min reaction time, 430 °C temperature and 5% of catalyst in continuous flow of nitrogen were observed as the most appropriate conditions for maximum oil production. Gas chromatography-mass spectrometry (GC-MS) of the obtained oil was performed for determining the composition of the oil. Moreover, fuel properties of the oil were examined and found comparable with commercial fuel. Furthermore, thermal degradation of polypropylene with and without cobalt oxide catalyst was performed in a thermobalance under nitrogen environment in the temperature ranging from 30 to 600 °C at temperature programmed rate of 5, 10, 15 and 20 °C/min. Using Kissinger-Akahira-Sunnose (KAS) kinetic model, the average activation energy (Ea) of non-catalytic reaction was found to be 83.14 kJ/mol, while in the presence of cobalt oxide the average Ea was observed as 63.55 kJ/mol. It was observed from the comparison of both the results that use of cobalt oxide has not only reduced Ea but also resulted in the production of oil having resemblance with fuel grade oil. Hence, cobalt oxide was found to be an efficient catalyst for the conversion of polypropylene into valuable products and the study performed on model polypropylene can be extended to polypropylene waste on industrial scale.

Kinetic information extracted from biochemical methane potential (BMP) tests is often reported but its value is unclear. Inter-laboratory reproducibility provides a useful indication of its value. Here we extracted estimates of the first-order rate constant $k$ from 1259 methane production curves collected in a large inter-laboratory study on BMP in order to quantify reproducibility. Reproducibility in $k$ was poor; relative standard deviation was 50–140%. Substrate comparisons ($k$ for one substrate compared to another) also had low reproducibility, regardless of low $p$ values from inferential statistical tests. The use of a shared inoculum did not improve reproducibility in $k$. We conclude that $k$ estimates from BMP tests only partially reflect intrinsic substrate properties. Therefore, interpretation and application of batch kinetic results should be done cautiously.

The present paper expounds development of a two stage solvent extraction scheme for separation of rare earths (REE) from a sulfuric acid leachate obtained from an Indian coal flyash sample containing 2160 ppm REE. The leachate has low concentration of REE (305 mg/L) and high content of impurities (32.6 g/L). The problem of gel formation due to presence of Si in the leachate was prevented by gelatin strike which lowered dissolved Si content. About 94% of HREE and 86% of Light Rare Earths (LREE) values could be recovered in first and second stages of solvent extraction stages using D2EHPA solvent of optimized concentrations 12% (v/v) and 40% (v/v) saponified up to 40%, respectively. The two organic streams, former rich in HREE and the later rich in LREE, were subjected to multi stage cross current stripping at low A/O ratio using 6 mol/L HCl solution to obtain strip solutions concentrated in HREE and LREE respectively. The two strip liquors were neutralized with NaOH from which REE were precipitated using oxalic acid dihydrate to produce mixed REE concentrates, assaying 13% HREE and 17.5% LREE. The present study was a maiden attempt to recover REE from the actual leachate, of complex chemistry, obtained from an India flyash sample. Further, the flowsheet was up scaled to bench scale which includes easily scalable processes like leaching at ambient temperature (25 °C) and high solids concentration (20% w/v) followed by solvent extraction and precipitation stages. This study establishes a high potential for the recovery of REE from an Indian coal flyash at industrial scale. Scope exists for future studies on separation of individual rare earths oxides from the mixed REE oxalates that can be produced according to the present study.

Biodiesel has proven to be better in terms of emission and engine performance when compared to diesel. The reason for this can be attributed to the fact that they are environmentally friendly and combust well in diesel engines. Implementing the use of Cashew Nut Shell Liquid (CNSL) for biodiesel production on a commercial scale has the potential to be profitable as the feedstock is a waste. The environmental concern associated with improper waste disposal and combustion of fossil fuel for energy production is a huge issue that is ravaging most developing regions of the world. Providing research-based solutions to these problems is expedient and meets major sustainable development goals. The waste-to-fuel technique has proven to be an effective tool that can be harnessed in ending these concerns. Hence, improving the efficiency of wastes used as feedstock to produce clean fuel is pivotal to building a sustainable environment. CNSL is inexpensive and using it as fuel can help mitigate the environmental effects of improper waste disposal in cashew processing factories. CNSL is obtained from cashew nuts through different methods, including mechanical extraction, thermal extraction and solvent extraction. This paper reviews the state of research on the utilization of cashew nut shell liquid biodiesel (CNSLBD) in diesel engines. Further research gaps that need to be addressed for this fuel to be more efficient were also mentioned. This work weighs the potential of this fuel as a good alternative energy source. Performance parameters such as brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) were considered in this review. This article established that CNSLBD gives a BTE as low as 12.3% and as high as 25.7% depending on the experimental conditions involved. It gives high BSFC and low HC, CO and CO₂ emissions. It produces high NO_X emission, but this can be reduced with techniques like Exhaust Gas Recirculation and blending the fuel with other additives. The main problem with CNSLBD is its high density and viscosity. However, this can be fixed by blending the fuel with another low viscous fuel. The ideal mix ratio for CNSLBD blends is 80% diesel: 20% CNSL. This work also established that the yield of CNSLBD during transesterification can be increased through ultrasonication. Finally, CNSLBD can be said to be a promising alternative fuel that has the potential to benefit both cashew nut companies and the energy industry.

A deeper understanding of the kinetic and thermodynamic parameters of thermal degradation of sugarcane bagasse (SCB) is fundamental to defining appropriate conditions for primary biorefining in the production of renewable fuels. In this work, the kinetics of thermal degradation of high polymers of SCB was investigated through thermogravimetric data. Model-free and model-fitting methods were used to calculate apparent activation energies (E_a) and other related reaction parameters. An essential advance of this work is related to the quantitative interpretation of the degradation process (an endothermic and non-spontaneous process) via a multi-stage model governed by diffusion-controlled reactions and order-based models, which helps explain the differences observed in the mass balance of biorefining processes. Based on derivative thermogravimetric curves, three major peaks were associated with pseudo-components (PSE): PSE 1 (hemicelluloses + extractives and lignin), PSE 2 (cellulose + extractives and lignin), and PSE 3 (lignin + extractives and residual holocellulose). For PSE 1, PSE 2, and PSE 3, respectively, E_a ranges of 124–154, 147–153, and 230–530 kJ⋅mol⁻¹ were obtained using the Kissinger-Akahira-Sunose method, and 120–152, 144–150, and 232–545 kJ⋅mol⁻¹ were obtained using the Flynn-Wall-Ozawa method. These data support the calculation of many critical operating parameters of biorefinery processes, such as the minimum pretreatment temperature. SCB biorefining could lead to a degradation of up to 10, 0.5, and 11% of PSE 1, PSE 2, and PSE 3, respectively, at 473.15 K for 200 min.