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Propane dehydrogenation (PDH) is an industrial technology for direct propylene production which has received extensive attention in recent years. Nevertheless, existing non-oxidative dehydrogenation technologies still suffer from the thermodynamic equilibrium limitations and severe coking. Here, we develop the intensified propane dehydrogenation to propylene by the chemical looping engineering on nanoscale core-shell redox catalysts. The core-shell redox catalyst combines dehydrogenation catalyst and solid oxygen carrier at one particle, preferably compose of two to three atomic layer-type vanadia coating ceria nanodomains. The highest 93.5% propylene selectivity is obtained, sustaining 43.6% propylene yield under 300 long-term dehydrogenation-oxidation cycles, which outperforms an analog of industrially relevant K-CrO x /Al 2 O 3 catalysts and exhibits 45% energy savings in the scale-up of chemical looping scheme. Combining in situ spectroscopies, kinetics, and theoretical calculation, an intrinsically dynamic lattice oxygen “donator-acceptor” process is proposed that O 2- generated from the ceria oxygen carrier is boosted to diffuse and transfer to vanadia dehydrogenation sites via a concerted hopping pathway at the interface, stabilizing surface vanadia with moderate oxygen coverage at pseudo steady state for selective dehydrogenation without significant overoxidation or cracking. Non-oxidative dehydrogenation technologies suffer from the thermodynamic equilibrium limitations and severe coking. Here, the authors report the intensified propane dehydrogenation to propylene by the chemical looping engineering on nanoscale core-shell redox catalysts.

We investigate the dynamics of a self-rewetting drop placed on a substrate with a constant temperature gradient via three-dimensional numerical simulations using a conservative level-set approach to track the interface of the drop. The surface tension of a so-called self-rewetting fluid exhibits a parabolic dependence on temperature with a well-defined minimum. Two distinct drop behaviours, namely deformation and elongation, are observed when it is placed at the location of the minimum surface tension. The drop spreads slightly and reaches a pseudo-steady state in the deformation regime, while it continuously spreads until breakup in the elongation regime. Theoretical models based on the forces exerted on the drop have been developed to predict the critical condition at which the drop undergoes the transition between the two regimes, and the predictions are in good agreement with the numerical results. We also investigate the effect of the initial position of the drop with respect to the location of the minimum surface tension on the spreading and migration dynamics. It is found that, at early times, the migration of the drop obeys an exponential function with time, but it diverges at the later stage due to an increase in the drop deformation.

Dynamic reserves are an important dynamic parameter for evaluating well pattern adaptability and predicting development index. Due to the characteristics of low permeability, easy powder production and adsorption/desorption mechanism of coalbed methane wells, there are few static pressure data and long time for gas wells to reach pseudo-steady state. As a result, the commonly used dynamic reserve methods such as pressure drop method, elastic two-phase method and modern production decline analysis are not suitable for coalbed methane wells, especially for gas wells in the early stage of production. Based on the adsorption/desorption mechanism of coalbed methane, this paper proposes a new method of comprehensive analytical solution and numerical simulation, which can be applied to the dynamic reserve calculation of mid-early coalbed methane wells, and can generate real-time formation pressure field data for the characterization of underground desorption field. The simulation methods mainly include three aspects: (1) The fracturing fracture length and reservoir permeability are evaluated by using the early single-phase drainage and depressurization stage. Its advantage is that compared with the gas-water two-phase flow stage, it can effectively avoid the error caused by the uncertainty of gas-water two-phase seepage. (2) By carrying out the water production decline analysis, the final water production of gas wells is predicted, and the volumetric method is used to reverse calculate the swept area of gas well drainage and depressurization. (3) Using the above formation parameters, a single well numerical model is established to carry out the historical simulation and prediction of production and pressure, and obtain the final desorption radius, dynamic reserves, recoverable reserves and other parameters of the gas well. Based on the pre-production data of block AA and the data of the whole production cycle, the dynamic reserves predicted by the pre-production data are consistent with the dynamic reserves predicted by the whole production cycle, and the predicted recoverable reserves are basically consistent with the predicted results of EUR, indicating that the prediction results of this method are reliable. This method overcomes the shortcomings of traditional methods in the interpretation of coalbed methane wells, and can be applied to the assessment of gas wells in the middle and early stage.

BackgroundWildfire propagation is inherently non-steady, although forecasts of their spread focus on a pseudo-steady state assumption.AimsTo investigate the variability in rate of fire spread of wildfires in southern Australian grassland landscapes, and the effect of landscape features in inhibiting fire propagation. To evaluate the adequacy of grassfire rate of spread models currently used in Australia.MethodsWe reconstructed the propagation of six wildfires in grassland fuels and characterised the unsteady nature of rate of spread. We also analysed the effect of barriers to fire spread in slowing or halting wildfire propagation.Key resultsHeadfire rate of spread in wildfires was observed to be non-steady, with peaks in forward rate of spread being on average 2.6-times higher than mean values. The rate of spread had an average coefficient of variation of 88%. Areas of fuel discontinuity, such as roads, did not stop fires under moderate burning conditions, but resulted in slowing the average rate of fire spread.ConclusionsAnalysis of wildfire observations is key to understand fire behaviour features that are not replicable in experimental or modelling environments. Findings from the analysis can support fire-fighting safety awareness and inform landscape fire propagation modelling.

Due to high augmentation in population and low availability of land, the quantum of wastewater production has surged resulting in advancements in wastewater treatment systems. To cope under such stressful circumstances, moving bed biofilm reactor (MBBR) proves to be an upgraded treatment technology for industrial and municipal wastewater treatment. The present startup study has been carried out using a laboratory-scale aerobic MBBR with working volume of 25L for textile dye wastewater treatment having AnoxKaldnes K3 media at filling percentage of 50%. In order to acclimatize the microorganisms on textile dye wastewater, the startup of the reactor was carried out using lactose as readily degradable co-substrate with textile dye wastewater in different ratios at hydraulic retention time (HRT) of 24 h. The biofilm on the media was developed in 63 days duration and the reactor attained pseudo-steady state (PSS) in 185 days period. During PSS condition of the MBBR, the maximum chemical oxygen demand (COD) removal efficiency of 92% with mixed liquor suspended solids (MLSS) concentration of 4224 ± 22 mg/L has been achieved. The kinetic study for biodegradation of textile dye wastewater has also been carried out using the Monod growth kinetics. The values of bio-kinetic coefficients of yield of heterotrophic biomass (Y) and endogenous decay coefficient for heterotrophic biomass (Kd) recorded are 0.394 mgVSS/mgCOD.d and 0.087 day−1, respectively. The values of specific substrate removal rate (k), Monod half saturation constant (Ks), and maximum specific growth rate for heterotrophic biomass (µmax) are 0.024 mgCOD/mgVSS.d, 53.203 mg/L, and 0.0095 day−1, respectively, demonstrating the suitability and healthy performance of MBBR for textile dye wastewater treatment.

A closed-loop Flat Plate Pulsating Heat Pipe, filled with a water-ethanol mixture (filling ratio = 50% vol.), is tested in horizontal orientation at different heat loads to assess local wall-to-fluid heat fluxes exchanged within its adiabatic section. In addition, the thermal interactions between adjacent channels are investigated since they could be responsible for poorer thermal performances in such kinds of cooling systems. The studied device is obtained from a copper plate (width: 80 mm, length: 200 mm, thickness: 3.5 mm) machined with a single square shaped groove (3 x 3 mm 2 ) forming a series of 8 turns in the evaporator zone and covered with a second copper plate having same length and width, and thickness equal to 0.5 mm. During the Flat Plate Pulsating Heat Pipe operation, the temperature of the external wall, coated with a high-emissivity paint, is monitored within the whole adiabatic section by an InfraRed camera during the pseudo-steady state. The thermographic measurements are post-processed by adopting the Inverse Heat Conduction Problem resolution approach, adequately validated by numerical simulations. The resulting wall-to-fluid heat fluxes are studied in terms of amplitude and oscillation, thus providing novel pieces of information regarding the working behaviour of Flat Plate Pulsating Heat Pipes in terms of oscillatory flow and thermal interactions by conduction between adjacent channels.

Production Log is a key log that directly define the facies and layers behavior. The PLT measures the inflow zone thickness and the flow rate of each phase which is directly function of facies properties in terms of deliverability. On the basis of pseudo steady state flow regime (which is the dominant phase of production during PLT log operations) a mathematical relationship developed to determine skin and reservoir pressure per each inflow zone with reasonable error.

The adequate configuration and the effect of the reduction was studied for the In2O3-ZrO2/SAPO-34 catalyst with the aim of improving its performance (activity and selectivity in the pseudo-steady state) for the hydrogenation of CO, CO2 and CO2/CO (COx) mixtures into olefins. The experiments were carried out in a packed bed reactor at 400 °C; 30 bar; a H2/COx ratio of 3; CO2/COx ratios of 0, 0.5 and 1; a space time (referred to as In2O3-ZrO2 catalyst mass) of 3.35 gInZr h molC−1; and a time on stream up to 24 h. The mixture of individual catalyst particles, with an SAPO-34 to In2O3-ZrO2 mass ratio of 1/2, led to a better performance than hybrid catalysts prepared via pelletizing and better than the arrangement of individual catalysts in a dual bed. The deactivation of the catalyst using coke deposition and the remnant activity in the pseudo-steady state of the catalyst were dependent on the CO2 content in the feed since the synergy of the capabilities of the SAPO-34 catalyst to form coke and of the In2O3-ZrO2 catalyst to hydrogenate its precursors were affected. The partial reduction of the In2O3-ZrO2/SAPO-34 catalyst (corresponding to a superficial In0/In2O3 ratio of 0.04) improved its performance over the untreated and fully reduced catalyst in the hydrogenation of CO to olefins, but barely affected CO2/CO mixtures’ hydrogenation.

Sutherland et al. (2020) used simulations from a physics-based numerical fire behaviour model to investigate the effect of the ignition protocol (namely length, direction and rate of ignition) on the spread rates measured in experimental fires. They concluded that the methods used by Cruz et al. (2015) were inadequate as the fires were not spreading at the pseudo-steady state when rate of spread measurements were made, thereby raising questions about the validity of several published experimental and modelling results. Fire spread measurement data from three different outdoor experimental burning studies conducted in grass fuels are used to show that, contrary to the claims of Sutherland et al. (2020), the fire behaviour data collected in Cruz et al. (2015) were from fires spreading in the pseudo-steady-state regime and thus are compatible with data from larger experimental plots. A discussion is presented addressing why Sutherland et al. (2020) simulations were unable to replicate real-world data.

Stimulated shale reservoirs consist of kerogen, inorganic matter, secondary and hydraulic fractures. The dispersed distribution of kerogen within matrices and complex gas flow mechanisms make production evaluation challenging. Here we establish an analytical method that addresses kerogen-inorganic matter gas transfer, dispersed kerogen distribution, and complex gas flow mechanisms to facilitate evaluating gas production. The matrix element is defined as a kerogen core with an exterior inorganic sphere. Unlike most previous models, we merely use boundary conditions to describe kerogen-inorganic matter gas transfer without the instantaneous kerogen gas source term. It is closer to real inter-porosity flow conditions between kerogen and inorganic matter. Knudsen diffusion, surface diffusion, adsorption/desorption, and slip corrected flow are involved in matrix gas flow. Matrix-fracture coupling is realized by using a seven-region linear flow model. The model is verified against a published model and field data. Results reveal that inorganic matrices serve as a major gas source especially at early times. Kerogen provides limited contributions to production even under a pseudo-steady state. Kerogen properties’ influence starts from the late matrix-fracture inter-porosity flow regime, while inorganic matter properties control almost all flow regimes except the early-mid time fracture linear flow regime. The contribution of different linear flow regions is also documented.