查看更多>>摘要：An alarming rise in greenhouse gases originating from on-road vehicles and the rapid depletion of cultivable land for fuel feedstocks has led researchers to explore alternative means of biofuel production. In this context, the current study explores the heterotrophic cultivation of Chlorella pyrenoidosa microalgae by scaling-up using various combinations of stir-tank bioreactors for the sustainable synthesis of low-density biodiesel. Furthermore, statistical tools are employed to develop prediction models to incorporate 20% (vol/ vol) of the low-density biodiesel with diesel fuel (CP20) to obtain optimal experimental outputs. From the study, it was found that the percentage dry cell weight of samples acquired from 100 L, 200 L and 300 L stir tank bioreactors achieved 44.1%, 46.7% and 41% of lipid content and biomass concentrations of 5.15 g/L, 4.24 g/L and 4.36 g/L on up-scaling. At an optimal reaction temperature and time of 37 °C and 12 h, the highest biodiesel conversion rate of 98% was achieved during enzymatic transesterification. The prediction engine models reveals that at the finest engine input parameter combinations, 0.74% improvement in brake thermal efficiency and a 50% drop in smoke emissions are achieved using the low-density CP20 blend. Also, superior combustion characteristics are delivered on operation as a trade-off for NOx emissions.
查看更多>>摘要：The blast-mitigation effect produced by water droplets sprayed into a confined geometry was studied. When a one-dimensional blast wave interacts with a layer of water droplets, blast mitigation occurs that can be expected to reduce the damage from an accidental explosion. Focus was on the blast-mitigation effect produced by the quasi-steady drag force between the shocked air and the stationary water droplets. Momentum transfer due to the drag mitigated the blast wave, and the maximum blast-wave mitigation occurred just behind the layer of droplets. The study parameters (the volume fraction of water droplets, the location and length of the region with sprayed water droplets, and the mass of the high explosive) demonstrated that higher momentum loss from the air resulted in greater mitigation. The momentum loss was evaluated using the volume fraction and length of the layer of water droplets and the quasi-steady drag force when the shock wave reached the layer. Relationships were formulated between the initial conditions, the momentum loss, and the blast-mitigation effect, which made it possible to evaluate quantitatively the mitigation effect on the blast wave caused by the water droplets.
查看更多>>摘要：The removal of excessive phosphate from water is very important to avoid eutrophication. For this purpose, metal-organic frameworks (MOFs) have recently attracted great attention in phosphate adsorption due to their outstanding physicochemical features. However, most of the used MOFs in the adsorption of phosphate are based on those synthesized from organic ligands derived from petroleum sources such as tricarboxylic (BTC) and dicarboxylic acid (BDC), which can negatively impact the environment. Consequently, using stable MOF synthesized from an eco-friendly ligand is highly desired. In this work, Aluminum based fumarate MOF (Al-Fum) was used in the adsorption of phosphate from water and subsequently compared with other Al-MOF derived dicarboxylic acid (Al-BDC) and tricarboxylic acid (Al-BTC). The phosphate adsorption performance of the different synthesized Al-MOFs was evaluated with the help of different batch experiments related to the effect of adsorbent/adsorbate concentrations, the contact time, the pH and the temperature. Interestingly, Al-Fum displayed the highest adsorption capacity (67,62 mg P/g) compared to Al-BDC (47,58 mg P/g) and AI-BTC (23,17 mg P/g) at RT (22,2 °C). The regeneration of Al-Fum was tested for several cycles showing continuous adsorption capacity and stability. This work opens a new avenue toward the development and use of more environmentally friendly and reused MOFs for the removal of phosphate from water.
查看更多>>摘要：Safety is a key part of any modern production process and as such is reflected in legislation and work regulations. Decision-making concept based on inherently safer design principles is introduced in this paper. Two case studies representing typical modern chemical processes are studied with the emphasis on their inherent safety level. First case study is a novel process to convert refinery waste into valuable products-production of ammonium thiosulphate. As a second case study, production of ethyl acetate by esterification was selected due to its potential for process intensification through reactive distillation. For each case study, two design alternatives are proposed. Utilising process data, the design alternatives are evaluated using five safety indices and compared to each other to identify the inherently safer one considering fire and explosion hazards as well as toxicity level. Results show that different sensitivity of index methods can lead to different outcomes of hazard potential identification. For the second case study, results of each method were in agreement. However, reverse order of design alternatives was obtained in the analysis of the first case study. As a part of this article, novel processing technique employing geometry of polygons to assess hazard distribution and inherent safety level of different process routes has been introduced and employed. Obtained results suggest possible implementation of the proposed approach to robust multi-criteria decision analysis as a safety assessment criterion.
查看更多>>摘要：To recycle isopropanol and ethyl acetate from wastewater by extractive distillation, l-butyl-3-methylimi-dazolium acetate ([BMIM][OAc]) is considered to be an appropriate entrainer by comparing with ethylene glycol on VLE diagram and a-Profiles, respectively. Then, the extractive distillation processes with [BMIM] [OAc] as entrainer are proposed. Since the degradation temperature of [BMHVI][OAc] requires the entrainer recovery section of processes to operate under high vacuum, one-stage evaporator and one stripping column configuration is determined to recycle entrainer [BMIM][OAc]. After optimizing the IL processes, the heat integration technology is applied to the optimized processes. Compared conventional extractive distillation process with EG as entrainer, the heat integration assisted IL process with appropriate entrainer recovery configuration which uses IPA as stripping agent can reduce 24.76% of TAC, 45.64% of energy consumption and 45.52% of gas emission.
查看更多>>摘要：The existences of non-biodegradable 5-Fluorouracil (5-FU) in aquatic systems and its potential toxic effects on aquatic organisms have caused widespread concern. In this work, two typical oxidants (O3 and-OH) were selected to investigate the mechanism, kinetics, and the potential eco-toxicology assessment of 5-FU using computational chemistry methods. Results show that 5-FU can be degraded rapidly by O3 and-OH, which subsequently undergoes ring-opening, decomposition, defluorination, and hydroxylation steps. The rate constants of initiation reactions are suppressed as the temperature increases. The half-lives of 5-FU determined by O3 and-OH are on the order of seconds in the advanced oxidation processes (AOPs) system. Fifteen structures of transformation products were identified by theoretical calculation, including five experimental products. The toxicity assessment results show that the acute and chronic toxicities of the degradation process to aquatic organisms gradually decreased, but the developmental toxicity and mutagenicity of several products on human still exist. In addition, the main products have been found to decompose into some small molecules (NO, Formic acid, Acetic acid, etc.). This result could help to reveal the transformation behaviors and risk assessment of 5-FU in aquatic environments, and further design the experimental and industrial infrastructure.
查看更多>>摘要：In recent years, several major accidents, such as the US Macondo well blowout in 2010, Chinese Bohai Bay oil spills in 2011, Brazilian FPSO Cidade de Sao Mateus gas explosion in 2015 and Chinese Bohai oil field blowout & fire accident in 2021, have provoked a high awareness that an essential distinction exists between the major accident management and the occupational accident management in the offshore petroleum sector. Further, the urgent need for defining effective major accident indicators is confirmed for the purpose of identifying early warning signals before the major offshore accident occurs. Regrettably, to this day, the offshore petroleum sector has not reached a consensus on the theoretical foundation for the development of effective major accident indicators. This article presents a focused review on the extensive work of the development of major accident indicators in the offshore petroleum sector, including terminologies, assessment criteria for good indicators, development approaches, as well as an overview of current major accident indicators. Following the close scrutiny of this focused review, the strengths and weaknesses of different development approaches are compared. The progress, challenges, suitability and validity of the development of major accident indicators are discussed. On the basis of these insights, future works are suggested to develop effective major accident indicators to better engage on the emerging and complex challenges in preventing major offshore accidents.
查看更多>>摘要：Based on the panel data of various daily air pollution indicators of 288 prefecture-level cities in China from January 1, 2015 to December 31, 2018, this paper takes the first round of central environmental protection inspection (CEPI) as a quasi-natural experiment, and empirically analyzes its impact on urban air pollution by using multi-period difference-in-difference (DID) method. The results show that: (1) the first round of five batches of environmental inspection and two batches of "looking back" have significantly reduced the concentration of seven pollutants; (2) The first five batches of environmental inspection have a stronger impact on reducing air pollution than "looking back"; Moreover, in the short term after the inspection, it still has a significant reduction effect on air pollution; (3) The impact of central environmental protection inspection on air pollution shows strong heterogeneity in different batches of inspections, urban scale and economic development level, as well as the air quality level of cities before the inspection. The research results of this paper provide corresponding policy recommendations and decision-making basis for the Chinese central government to further deepen the reform of environmental protection supervision mechanism and promote the emissions of multiple pollutants mitigation.
查看更多>>摘要：The rapid cleanup of endogenous CO2 has become a necessity in environmental control and life support systems (ECLSSs), to ensure crew safety and long-term task execution. The extensively used non-regener-able LiOH and soda lime adsorbents, although exhibit high CO2 storage capacities and fast kinetics, can hardly fulfill the demands of reduced launch weight and storage volume in the space-and load-limited ECLSSs. New CO2 adsorbents with desirable attributes including high CO2 uptakes, good selectivity, facile regeneration, fast adsorption and desorption kinetics, and good multicycle stability are urgently needed. We developed amine-functionalized adsorbents by loading tetraethylenepentamine (TEPA) on mesoporous supports of activated carbon (AC), aluminum oxide (AO) and silica gel (SG). The adsorbents were characterized by N2 adsorption-desorption, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) to study their microstructural properties. CO2 adsorption capacities and kinetic performance of the adsorbents with different supports and various amine loadings (10-50 wt%) were evaluated in 2%CO2 at 20 °C. The effects of support and amine loading on the structure-performance relationships of the adsorbents were demonstrated. The TEPA-SG-20 adsorbent (20 wt% TEPA loaded on silica gel support) exhibits the highest CO2 adsorption capacity of 1.90 mmol CO2/g and the maximum amine efficiency of 0.48 mmol CO2/mmol N. TEPA-SG-20 also exhibits fast CO2 adsorption kinetics, and the Avrami fractional order kinetic model provides a satisfactory correlation of the experimental CO2 uptakes. Furthermore, the TEPA-SG-20 adsorbent can be efficiently regenerated at 110 °C with a great regeneration efficacy of 97%. The desired adsorbent also exhibits good working stability with a low loss-in-capacity of 4.32% in 10 consecutive cycles. The good CO2 adsorption performance of TEPA-SG-20 is associated with the excellent microstructural properties such as high surface area, great pore volume and uniform dispersion of amine species. Overall, the desired TEPA-SG-20 adsorbent shows promise for low-concentration CO2 removal in ECLSSs.
查看更多>>摘要：Municipal sewage sludge (SS) can be used as an alternative carbon-neutral feedstock for energy utilization owing to its considerable higher heating value compared with lignite coal. It is potential to efficiently co-utilize SS by coal-sludge-slurry gasification technology avoiding the energy consumption for SS drying process. In this study the effects of SS blending on the techno-economic performance of Integrated Gasification Combined Cycle (IGCC) systems based on different kinds of gasification technology and coal are analyzed. The results show that the overall energy efficiency of the system based on dry gasifier is more sensitively affected by the blending of SS than the one based on wet gasification due to the energy consumption during drying process. For wet gasification technology, the overall energy efficiency for coal A first increases from 45.17% to 45.26% and then reduces to 44.77% with the SS mix ratio, while the overall energy efficiency for coal C declines from 38.58% to 38.03%. The results indicate the overall energy efficiency has positive correlation with the cold gas efficiency instead of ash fusion temperature and the effects of SS addition on the overall energy efficiency can be qualitatively estimated by analyzing the cold gas efficiency. In most cases the blending of SS in IGCC systems benefits the economic performance and the net present value of the system based on wet gasification and coal A could be increased by 88% due to the increasing power output and the SS treatment subsidy.
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