Cleaner Chemical Engineering最新文献

This study aims to highlight the energy improvement potentials of Pakistan's paper sector that is one of the most energy intensive industries by benchmarking its specific energy consumption (SEC) to produce a similar grade of paper. To address issues such as the lack of indicators for energy efficiency benchmarking in Pakistan's paper industry. Furthermore, energy saving potential was estimated by comparison with paper industries in the United Kingdom and Canada, where energy benchmarks have already been established and data on energy benchmarking is readily available. This study energy consumption data accounts for 75% of the total energy utilized in Pakistan's paper industry and is compared with the energy consumption of the UK and Canada paper sectors where the most up-to-date energy-saving techniques are used. The calculation shows that when compared to the paper industries in the UK and Canada, Pakistan's paper industry utilizes an additional 1.3 MWh of energy for every tonne of paper produced. With a total yearly paper production of 314,549 metric tonnes, this equates to an additional 408,913 MWh of overall annual energy use. It is concluded that if the proposed energy benchmark in this study is applied within the country's mill comparison, savings of 16.4% of overall energy consumption in the Pakistan paper sector can be achieved. It is also shown that the implementation of the best available techniques used in the UK and Canada in Pakistan's paper sector could result in a potential energy saving of 43% of the total energy consumed by this sector.

This study investigated the use of carbon-coated-sand (CCS), as a more sustainable alternative to activated carbon (AC), for the removal of Ni²⁺and Cu²⁺ ions from an aqueous solution. The CCS was synthesized from sugar and sand without any additional binders and then activated using 0.1 M H₂SO₄ to form the modified version called MCSS. Activation increased the specific surface area by 15-folds from 0.409 (CCS) to 6.183 (MCCS) m²/g. Multi-linear regression was applied to evaluate the adsorption capacity as a function of three independent factors: pH of the solution; contact time; and initial concentration of the adsorbate. The optimum adsorption of Cu²⁺ and Ni²⁺ was achieved at pH 6.0 for both adsorbents. Activation enhanced the adsorption capacity by 68% for Cu²⁺and 54% for Ni²⁺. The adsorption behavior under different conditions was successfully modeled using multi-linear regression with high accuracy R² > 0.86 for CCS and R² > 0.96 for MCCS. Cost estimation provided encouraging evidence of the cost-effectiveness of CCS and MCCS compared to activated carbon. The results obtained in this study revealed that carbon-coating is a promising greener low-cost technique for water treatment.

The relevance of heterogeneous catalysis in biodiesel production cannot be overemphasized, as heterogeneous catalysts have eliminated the demerits associated with a homogeneous catalysts. Some heterogeneous catalysts experience drawbacks such as partial recoverability and reusability, energy and waste conservation issues during biodiesel processing and leaching of active catalyst sites. This paper highlights and summarizes several heterogeneous catalysts used in biodiesel production. The catalyst preparation, reaction conditions, feedstock, and biodiesel yield for the heterogeneous base and acid catalysts were emphasized. The inability of heterogeneous base catalysts to trans-esterify low-grade oil with high free fatty acid (FFA) is a primary concern; the cost of processing low-grade oil with high FFA using heterogeneous acid catalysts is also a big issue. Nano-doped heterogeneous catalysts with unique properties were recommended because they can process oil with high FFA transesterification, improve reaction efficiency, simplify production, reduce the leaching of active sites, enable better biodiesel yield by minimizing energy and waste, and increase catalyst recoverability, activity, selectivity and durability.

The aim of this study was to evaluate the effect of impregnation with zinc chloride on the characteristics of orange albedo biochar produced in a top-lit updraft biomass conversion reactor with retort heating. The study was done in a bid to improve the porosity and surface area of the orange albedo biochar. The impregnated biochar was impregnated with zinc chloride salt (impregnation ratio = 1:1 for 24 h) before carbonization. Three techniques of characterization (SEM-EDS, FTIR, and BET) were used to characterize the biochars to determine their porosity, chemical composition, morphology, and chemistry. The un-impregnated biochar and the impregnated biochar have a specific surface area of 114.036 m²/g and 148.030 m²/g, respectively, and both biochars are mesoporous.

Na in Fe-based catalysts can be used to increase CO conversion and C₂-C₄ olefins and decrease the conversion of H₂ and C₁ selectivity, but its behaviour at different reaction temperatures is of importance in Fischer-Tropsch synthesis (FTS). The dependency of the C₁ formation rate, the conversions of H₂ and CO, the water-gas shift reaction, the olefins and paraffins of the C₂-C₄ and C₅-C₁₂ hydrocarbons, and C₁₃₊ hydrocarbons on the reaction temperature for prepared Fe/Al₂O₃ and FeNa/Al₂O₃ catalysts was evaluated in a tubular fixed-bed reactor. This was done to investigate the effects of Na in Fe-based catalyst at different reaction temperatures (250 – 310 °C). The results show that the effects of Na in Fe-based catalysts to increase CO conversion and decrease H₂ conversion are dependent on the reaction temperature in FTS. The Na-promoted Fe-based catalyst (FeNa/Al₂O₃) gave a lower C₁ formation rate at certain lower reaction temperatures (250 °C and 270 °C) compared to the unpromoted Fe-based catalyst (Fe/Al₂O₃). The presence of Na in the Fe-based catalyst improved the C₁ formation rate at certain higher reaction temperatures (290 °C and 310 °C). Na was found to hinder the selectivity towards C₂-C₄ paraffins and C₁₃₊ hydrocarbons, including the oxygenates, and improve the formation of C₂-C₄ olefins and C₅-C₁₂ hydrocarbons at different reaction temperatures.

The cost of adsorbent preparation and usage is an important factor that determines its suitability for use in wastewater treatment in light of other competing technologies. Adsorbent cost can be determined via the cost of raw materials, discounted cash flow, cost indices, cost of adsorbent per gram of the adsorbate removed, Annual Capital Expenditure (CAPEX) and Operating Expenditures (OPEX), and the cost of adsorbent application in an adsorption operation. The need to unify the various concepts of adsorbent cost of different researchers and the evaluation of how the process efficiency affects the process cost prompted the need for this study. This paper aimed to review the cost of using different adsorbents for treating wastewater. It also developed a quantitative metric for comparing adsorbent costs known as the “adsorbent cost performance,” termed as Ĉ (and computed in $/mol). This was elucidated as the dollar cost of producing and using 1 g of an adsorbent for the removal of 1 mole of a chemical species in the aqueous phase, considered at the theoretical point of maximum uptake of the chemical species. There is a wide variation in adsorbent cost performance, but most adsorbents fall between 1 and 200 $/mol. Adsorbents at < 1 $/mol threshold can be considered very cheap for the intended application, while those at > 200 $/mol can be considered very expensive. More investigations into adsorbent cost analysis are encouraged, especially in routine adsorption studies, to help extend the practical relevance of these papers.

Epoxidation-esterification of fatty acid methyl ester obtained from Terminalia catappa L. kernel oil (TCKO), its characterization, kinetics and thermodynamics were the main focus of this study. The methyl ester obtained via base catalyzed transesterification was used for epoxidation-esterification modification process. Epoxidation kinetics and thermodynamics parameters were also investigated. The properties of the TCKO and epoxidized-esterified Terminalia catappa L. kernel oil methyl ester (MTCKO^e) were determined using standard methods. MTCKO^e was analyzed using Dissolved Gas Analysis equipment, so as to determine its constituent gases compositions. The order ${10}^{-5}$Lmol⁻¹s⁻¹ and 39.97 KJ/mol were the respective rate constant K and activation energy Ea, obtained for the epoxidation process. ΔG, ΔH, and ΔS values for the epoxidation process were (136.00–148.82 kJ mol⁻¹), 37.24 kJ mol⁻¹, and $-$320.64 J mol⁻¹ K⁻¹, respectively, indicating non-spontaneous, endothermic, and endergonic process. The properties of MTCKO^e sample were: -8°C, 280°C, 820 Kg/dm³, 8.56 mm²/s, 0.80 mgKOH/g, 0.65 mg/Kg and 50.05 KV for pour point, flash point, density, viscosity, acid value, moisture content and dielectric strength, respectively. The dissolved gas analysis result (in ppm) of the key gases for MTCKO^e sample are: <5, 87, 1441, <1, 6, 84, 3, <0.5 for H₂, H₂O, CO₂, CO, C₂H₄, C₂H₆, CH₄, C₂H₂, respectively. The characteristics met acceptable standard limits. The MTCKO^e properties indicated its possible use as bio-transformer oil.

The use of microalgae for CO₂ sequestration helps in mitigating global warming. This paper reviews the application of microalgae for CO₂ sequestration with emphasis on performance evaluation, lifecycle, economic assessment, as well as environmental impact. The CO₂ sequestration mechanism is done during photosynthesis, via bioconcentration. Performance evaluation revealed that the efficiency of capture and sequestration of CO₂ by microalgae ranges between 40% and 93.7%. However, the macro performance of microalgae in carbon emission reduction has not yet been fully understood, and therefore requires more studies. Also, the cost-effectiveness of the CO₂ sequestration by microalgae cultivation still needs more research based on recent economic realities. It is recommended that design and operation be focused on cost-effectiveness so the technology can compete favourably with existing technologies. Overall, it can be surmised that the application of microalgae for CO₂ sequestration is an effective technique for carbon capture, but still has interesting areas for development for greater global environmental impact.

Poultry wastes (PW) and palm oil mill effluents (POME) are thought to be promising starting materials for biogas production. In the present study, the optimization of biomethanization process from co-digested (PW) and POME was investigated. To assist digestion, samples were sun-dried, ground, and mixed with water to form slurry. The central composite design was used in the experimental design, while the desirability function was applied in the process optimization of the co-digestion process. The interactive effects of temperature, pH, and hydraulic retention time were equally studied. The results showed a high co-efficient of determination (R²) value of 0.9920. Also, the predicted and experimental values obtained were 4377.71 ml and 4379.01 respectively, while the optimum conditions obtained were 45 °C, 8.00 and 15 days for temperature, pH, and hydraulic retention time, respectively. This finding shows that the proposed technique is effective and robust in predicting biomethane generation from co-digested POME and PW.

Energy consumption is increasing day by day, thereby depleting the fossil fuel reserve at an alarming rate. The fossil-based fuels have many adverse effects on the environment and cause global warming due to emission of greenhouse gases. Biodiesel produced via the transesterification process is an alternative, eco-friendly, and renewable fuel. Transesterification is carried out using homogeneous, enzyme, and heterogeneous catalysts. Heterogeneous catalysts can resolve the issues faced by the homogeneous and enzyme catalysts during biodiesel synthesis. At the same time, heterogeneous nanocatalysts have much more potential due to their higher surface area, more selectivity, and stronger catalytic activity. In this review, various nanocatalysts such as metal oxides (CaO, MgO, ZnO, Ti₂O, CuO, and ZrO₂), magnetic nanocatalyst, nano-zeolite catalyst, and nano-hydrotalcite catalysts were studied. In addition, catalyst preparation methods, physical properties of catalyst along with various reaction parameters such as reaction temperature and time, methanol to oil molar ratio (MTOMR), catalyst loading, and biodiesel yield were highlighted and discussed. In short, biodiesel synthesis using nanocatalyst can provide a cheap and clean energy and thus the nanocatalyst can be further developed as a strong candidate for the global energy industry in the future.