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Due to the serious economic losses and deaths caused by COVID-19, the modeling and control of such a pandemic has become a hot research topic. This paper finds an analogy between a polymerization reaction and COVID-19 transmission dynamics, which will provide a novel perspective to optimal control measures. Susceptible individuals, exposed people, infected cases, recovered population, and the dead can be assumed to be specific molecules in the polymerization system. In this paper, a hypothetical polymerization reactor is constructed to describe the transmission of an epidemic, and its kinetic parameters are regressed by the least-squares method. The intensity of social distancing u is considered to the mixing degree of the reaction system, and contact tracing and isolation ρ can be regarded as an external circulation in the main reactor to reduce the concentration of active species. Through these analogies, this model can predict the peak infection, deaths, and end time of the epidemic under different control measures to support the decision-making process. Without any measures (u = 1.0 and ρ = 0), more than 90% of the population would be infected. It takes several years to complete herd immunity by nonpharmacological intervention when the proportion of deaths is limited to less than 5%. However, vaccination can reduce the time to tens to hundreds of days, which is related to the maximum number of vaccines per day.

A co-reaction of methane with methanol over zeolite catalysts has emerged as a new approach to the long-standing challenge of methane transformation. However, the effect of catalyst acid properties on the co-reaction has been rarely studied. In this study, a series of HZSM-5 zeolites with comparable diffusion abilities and various acidities were synthesized directly through steaming with 100% water vapor at 693 K. The co-reaction of methane and methanol was subsequently evaluated. Bronsted acidity at 0.262 mmol/g was detected to reach the maximum methane conversion of 5.42% at 673 K, which was also the odd point in the relationship between acid concentration and C4 hydrogen transfer index. Moreover, the influence of methanol feed was investigated over parent and steamed ZSM-5 catalyst, with results showing that excessive acid sites or methanol molecules reduce methane conversion. It is proposed that acid sites adsorbed with methanol molecules construct the methane activation sites. Hence, a proper design of zeolite acidity should be achieved to obtain higher methane conversion in the co-reaction process.

We present the first 3D-printed continuous flow platform for the green synthesis of methylaluminoxane (MAO), the most powerful olefin polymerization co-catalyst with metallocenes. This platform consists of an on demand designed and 3D-printed liquid–liquid mixer, reactors, and a separator to enable precise control of the highly exothermic hydrolytic reaction of trimethylaluminum (TMA). Moreover, during TMA hydrolysis, solid by-products are formed and methane gas is released, both of which impede reagents blending and MAO formation, thereby making it a challenging implementation with a continuous flow strategy. By optimizing the platform configuration and reaction conditions, we obtain an MAO product with a high yield and superior co-catalytic activity, as measured by two different groups of polymerization tests. This low-volume process, which avoids the accumulation of any explosive reagents, offers long-term stability and inherent safety and facilitates scale up with multiple reactors. In addition, such an efficient, scalable, and safe flow platform preserving the mixing and heat transfer advantages delivers insights into handling other highly exothermic reactions involving the formation of solids and gases.

Busbar current sensor without magnetic core is used more and more in compact power electronic equipment due to its small size and lightweight. The differential measurement technique is generally adopted to resist external magnetic interference. The sensitivity of busbar current sensors varies with the frequency of the sensed current due to the skin effect in the busbar. Traditional coreless busbar current sensors can accurately measure dc current, but the measurement error increases when sensing high-frequency ac current. A coreless sensor configuration based on four tunneling magnetoresistance (TMR) chips is proposed in this article with high measurement accuracy for both dc and high-frequency ac currents while eliminating the effect of magnetic stray field. An optimization method is introduced for the layout of the TMR chips around the busbar in order to obtain a current error below 1.5% up to 1 kHz. The effectiveness of the proposed sensor configuration and layout optimization method are verified by finite element simulation and prototype tests.

Large dc current is typically measured by an open-loop sensor without a magnetic core. The widely used configuration uses a differential magnetic sensor inserted into the busbar hole or a differential magnetic sensor placed on the upper and lower surfaces of the busbar. The use of a differential sensor has the advantage of being resistant to external magnetic fields. In this article, a new differential ultra-small magnetic sensor with the size of 23.2 mm × 16.5 mm × 7.2 mm is designed. The sensor is based on tunneling magnetoresistance (TMR) and is placed on the upper surface edge of the busbar. The supply voltage is 5 V, the rated current measurement range is ±150 A, and the peak current measurement range is ±250 A, corresponding to 2.5 ± 2 V output at ±250 A dc peak current. The relative accuracy is less than ±1% at 25 °C and is less than ±2% over the full temperature range from -40 °C to 105 °C.

Limited by harsh reaction conditions, the activation and utilization of methane were regarded as holy grail reaction. Co-reaction with methanol, successfully realizing mild conversion below 450 °C, provides practical strategies for methane conversion on metal-loaded ZSM-5 zeolites, especially for highly efficient Zn loaded ones. However, Zn species, regarded as active acid sites on the zeolite, have not been sufficiently studied. In this paper, Zn-loaded ZSM-5 zeolite was prepared, and Zn was modified by capacity, loading strategy, and treating atmosphere. Apparent methane conversion achieves 15.3% for 1.0Zn/Z-H2 (16.8% as calculated net conversion) with a significantly reduced loading of 1.0 wt.% against deactivation, which is among the best within related zeolite materials. Besides, compared to the MTA reaction, the addition of methane promotes the high-valued aromatic production from 49.4% to 54.8%, and inhibits the C10+ production from 7.8% to 3.6%. Notably, Zn2+ is found to be another active site different from the reported ZnOH+. Medium strong acid sites are proved to be beneficial for methane activation. This work provides suggestions for the modification of the Zn active site, in order to prepare highly efficient catalysts for methane activation and BTX production in co-reaction with methanol.

In this work, experimental data from the novel high speed particle image velocimetry (HSPIV) measurements and pressure fluctuations complemented by numerical predictions from TFM simulations are processed using advanced signal processing protocols to identify and characterize coherent structures in a gas–solid fluidized bed with Geldart D particles. The time-frequency properties of the bed dynamics were studied using the wavelet coherent analysis (WCA) and the Hilbert Huang transform. The WCA of numerical pressure drop signals at different measurement positions showed the existence of spatial-temporal coherent structures. At close measurement positions phase locked coherent phenomenon due to bubble generation dominate most of the frequency and time scales due the proximity to the distributor. At a wider measurement spacing the fast traveling waves are attenuated due to gas bubble/void coalescence and acceleration and only pockets of highly coherent oscillations are visible mostly in the frequency range of 0.5–3 Hz at certain times. Multi-resolution of the particle fluctuations realized with the Hilbert–Huang transform. The structures were resolved into the micro, meso and macro scales of fluidization based on the energy and frequency distributions. The meso scale structures form the main contribution to the normal axial Reynolds stresses and bubble granular temperature and ultimately the mixing.

Molecular reconstruction is popular in current oil refinery modeling. It aims to understand the refining process from the molecular level, to predict product properties accurately, to optimize the processes, and to increase the value of each molecule. Molecular reconstruction technique determines the detailed molecular composition of petroleum fractions through obtainable bulk properties and chemical details. In this paper, the existing molecular reconstruction models involving models with a set of predefined deterministic molecules, stochastic reconstruction method, structure-oriented lumping method, molecular type-homologous series matrix method, reconstruction by entropy maximization method, stochastic reconstruction-entropy maximization method and state space representation method are reviewed and compared. The credibility of the simulated composition and the drawbacks of molecular reconstruction technique are also discussed.

Fluidized beds with the liquid spray have been widely applied due to efficient heat transfer ability. In this work, the liquid-containing particles and the liquid dispersion pathway are visualized by a unique reversible thermochromic material (RTM) tracking method. The effects of evaporative liquid considering different nozzle modes on bubble density, particle motion and heat transfer are investigated combining PIV and DIA. The results indicate that the liquid injection decreases particle fluctuation and promotes bubble generation. A stable liquid-containing zone is observed under the top spray mode, whereas liquid disperses rapidly under the side-wall spray mode. A multi-zone heat transfer model (MHTM) is then developed based on the bubble growth and inter-layer exchange models. Experimental and calculated temperature profiles indicate that the side-wall spray mode leads to larger temperature differences. The methods proposed can be applied for the analysis of the complex multiphase system and optimization of the nozzle configuration. This work is supported by the National Natural Science Foundation of China for Young (No. 21808198), the Major Research Project of National Natural Science Foundation of China (91834303), the Natural Science Foundation of Zhejiang Province for Young (No. LQ18B060001), the National Science Fund for Distinguished Young (No. 21525627).

Production of vinyl chloride monomer (VCM) via acetylene hydrochlorination reaction (AHR) is consuming huge amount of mercury catalyst that is highly toxic. A cheap, nontoxic, and effective alternate is urgently required. Here, we designed an AuI catalyst for AHR with the excellent catalytic performance. The designed 0.1AuI(wt%)/AC2 catalyst shows the comparable catalytic efficiency to the commercial mercury catalyst, which is applicable for industrial production of VCM. Theoretical calculations determine the activation mechanism of C2H2 by AuI, and highlight the high stability of AuI.

The gas–solid vertical single helical ribbon agitated reactor (G-S-VSAR) is a gas–solid dense-phase agitated reactor, in which the interaction between the agitator and the dense granules dominates the flow field and transfer behavior. The particle movement characteristics are essential for determining the reactor space–time yield and product quality. In this work, the particle residence time distribution (RTD) was measured through magnetic-particles pulse experiment to investigate the overall movement and mixing characteristics of a G-S-VSAR, with the effects of rotation speed and gas velocity studied. The RTD curves were featured by time lag, bypass peak and exponential tail, and thus a model of ‘PFR + double parallel CSTRs’ was established. Results showed that the increase in rotation speed could eliminate the bypass, but only reduce the lag time. The lag time adversely influenced the mixing. Photography was applied to characterize the local particle movements near the reactor wall. It was found that the particles spiraled upwardly along the wall in laminar-like flow and the fully mixed state reached after one circulation. During the spiraled process, the undulating displacement in the vertical direction was induced by agitation in the ribbon-wall gap, which inhibited the radial mixing. Therefore, a narrow gap was recommended for reducing such undulating movements and promoting radial mixing.

In many industrial processes, electrostatic charges are inevitable and affect the hydrodynamic behavior and heat transfer ability of chemical equipment. A comprehensive study of the electrostatic effect on bubble behavior, particle fluctuation velocity and heat transfer coefficient in the fluidized bed with a central jet has been evaluated in this paper by Eulerian-Eulerian two-fluid model coupled with electrostatic model and energy model. The simulated voidage profiles at different positions, bubble detachment time and initial bubble diameter are compared with experimental results from the literature without charge. The bubble behaviors including bubble frequency and bubble numbers, combined with particle fluctuation parameters are analyzed in both charged and uncharged system. The electrostatic effect on two kinds of heat transfer coefficients is quantitatively compared, namely bubble to emulsion phase heat transfers based on the gas throughflow velocity and gas-solid local heat transfer coefficient. Simulation results show that electrostatic charges decrease bubble numbers and granular temperature, whereas the averaged heat transfer coefficients are enhanced. Overall, the electrostatic effect on the hydrodynamic and heat transfer characteristics can be revealed. This work was supported by the Project of National Natural Science Foundation of China (No. 91434205), the National Science Fund for Distinguished Young Scholar (No. 21525627), the Science Fund for Creative Research Groups of National Nature Science Foundation of China (No. 61621002).

In this study, a series of aryloxy-aluminoxanes originated directly from the hydrolysis of reaction products of AlMe3 and phenols were synthesized, which could serve as effective polymer-retarding activators for the iron-catalyzed ethylene oligomerization. The molar ratios of [PhOH]/[AlMe3] and [H2O]/[Al] during the preparation were explored and their impacts on the oligomerization activity and product distribution were discussed. To obtain the effective activators with good polymer-retarding effect and relatively high activity, the optimized conditions were proposed to be [PhOH]/[AlMe3] = 0.5 and [H2O]/[Al] = 0.7. Various aluminoxanes with different [―OH] sources confirmed the importance of using phenols in preparing the effective polymer-retarding activators. By utilizing these aryloxy-aluminoxanes, the mass fraction of polymers in the total products could be reduced to lower than 1.0 wt%, which is much lower than that of the MAO-activated systems (> 30 wt%). This is a potential benefit for the industrial application of the iron-catalyzed oligomerization process.

A Polyhedral oligomeric silsesquioxane (POSS) modified Ziegler-Natta catalyst is reported to synthesize the weakly entangled ultra-high molecular weight polyethylene at a high temperature and with a high activity. Incorporation of POSS can form numbers of aggregates with a mean size of 48 nm adsorbing on the surface of SiO 2 . The structure of nanoaggregates is evidenced by the experiments and theoretical calculations where one POSS can coordinate with multiple MgCl 2 molecules serving as an electric donor to the further immobilized TiCl 4 . The catalyst is thus featured by two distinct active regions positioned in the POSS/MgCl 2 nanoaggregates and δ -MgCl 2 , respectively. The former regions present extremely low activity on ethylene polymerization, which function as horizontal separators for isolating the active TiCl 4 sites and the growing chains. This catalyst exhibits an exceptional activity ( i.e. 1.3 × 10 6 gPE mol Ti −1 h −1 bar −1 ) for the synthesis of weakly entangled polyethylene at 60 °C.

Combining cryogenic flash units with membrane units is attractive for gas separation processes such as effluent gas recovery and CO2 capture. However, systematic design methodology for such hybrid systems have not been reported yet. The hybrid system is a complicated system that not only includes separation units, but also includes pressure manipulation units and heat exchangers. A two-step decomposition strategy is proposed to deal with the design of such complicated system. The separation sequence is first determined with energy consumption consideration in the first step. Subsequently, the remaining energy recovery units, the heat exchanger network and turbines are simultaneously synthesized with the separation flowsheet optimization. When applying the proposed strategy to recover the effluent gas from polyolefin plant, we find a novel flowsheet that avoid intensive capital and operating cost by tightly integration of process units.

When the liquid is injected into a gas-solid fluidized bed, particles are easily wetted and prone to form liquid bridges among them, further leading to particle agglomeration. Wet particle agglomeration induced by liquid bridge is dynamic and unstable, and its evolution behavior affects the stable operation of fluidized bed reactor. Therefore, based on the formation-fragmentation competition mechanism, a wet agglomeration evolution model is proposed to predict the evolution characteristics of wet agglomerates under different conditions. Furthermore, a modified drag force model which attributed the effect of wet agglomerates into the drag force was established and applied to the CFD simulation of a fluidized bed with wet agglomerates under the liquid spray-evaporation equilibrium state. Meanwhile, the particle image velocimetry (PIV) technology is applied in this work, and it was found that the vertical solid velocity simulated by CFD is in good agreement with the PIV measurement results.

The design of refinery hydrogen networks minimizing the total annualized cost is a computationally hard optimization problem. This is mainly due to the highly nonlinear compression power constraint and the nonconvexities of the problem. To decrease the nonlinearities, we propose in this work a concept of pressure discretization, and therein the pressure variables of new makeup compressors make discrete choices among the specified pressures of hydrogen origin and destination units. Based on this concept, the constraint of compression power is linearized without losing rigors. Then, hydrogen networks design is formulated as a mixed integer nonlinear programming model that is applicable to both grass-roots synthesis and retrofit problems. We develop a global optimization algorithm to solve the proposed model to global optimality. Two grass-roots synthesis and three retrofit examples are tested for illustration purposes. The total annualized cost and computing time of our solutions compare favorably to those of literature solutions.

This work proposed a theoretical acoustic emission (AE) model showing the correlation between the acoustic energy of particle motions and conveying conditions in horizontal hydraulic conveying. The acoustic energy of particle motions was extracted and calculated from the original acoustic signals by frequency domain analysis, showing a “two-stage” linear changing trend with the squared mixture velocity. The high-speed photography and fluctuation distribution index showed that the “two-stage” linear changing trend was caused by the different particle dispersion states (uniform and non-uniform). Based on the classification of particle dispersion states and the AE model, the prediction model of solid concentration in hydraulic conveying was established, which had high prediction accuracy and good universality (prediction error: 10.2% for quartz sands and 14.0% for slag particles). Furthermore, the AE model also had the potential to directly apply a prediction model established for one material to another material only using some elementary experiments.

We present a 3D-printed continuous flow platform for controllable synthesis of isobutylaluminoxanes (IBAO), an effective olefin polymerization co-catalyst, via the highly exothermic hydrolytic reaction of triisobutylaluminum (TIBA). This platform encompasses modules of mixing and reaction, in-line separation, and in situ UV–vis characterization. In addition, two NMR protocols are established to validate the results of in-line UV–vis analysis (by 31P NMR) and reveal product structures (by 1H NMR). Measured temperature profiles over the reactor indicate essentially fast heat removal, ensuring inherent safety. Co-catalytic activities of IBAO are obtained from ethylene oligomerization experiments using an iron-based catalyst system at atmospheric pressure. Furthermore, we investigate the influence of key operating parameters including temperature, initial molar ratio between water and TIBA, initial TIBA concentration, and residence time. A high IBAO yield over 98% and a superior co-catalytic activity of ~ 5000 kg·(mol Fe)–1·h−1 are achieved with optimal parameters in this single-pass platform, demonstrating the advantages of process.

Electric fields have great potential to control meso-scale structures, typically bubbles and agglomerates in gas-solid fluidized beds. However, previous research only considered the effects of polarization forces and ignored the electrostatic effects. This work, by means of cold model experiments, for the first time investigates the effects of DC electric fields on meso-scale structures in a 3-D fluidized bed with electrostatic effects. Results show that particles will also experience the Coulomb force under the effects of electrostatics besides of polarization forces, and the effects of these two electric field forces are different. The Coulomb forces make particles migrate at lower field strengths, then increases the bubble size and breaks up agglomerates. While at higher field strengths, the polarization forces result in formation of agglomerates and reduction of bubble size. Therefore, the effects mechanism of electric fields is the competition effects between the Coulomb force and the polarization forces. The critical transition field strength, at which the predominant position of Coulomb and polarization forces on bubbles and agglomerates changes, is significant in the control of meso-scale structures by DC electric fields.

The gas–liquid mass transfer was investigated in a gas–liquid-solid three-phase moving bed based on the dissolved oxygen method, and a semi-quantitative gas–liquid boundary identification method was developed to measure the gas–liquid interfacial area. Results showed that the effects of gas velocity and liquid velocity on gas–liquid mass transfer in the three-phase moving bed were the same as those in the trickle bed. Since the gas–liquid interfacial area and its renewal speed were promoted at the low particle velocity and inhibited at the high particle velocity, the liquid-phase volumetric mass-transfer coefficient first increased and then decreased with the increasing particle velocity. Moreover, an empirical correlation for the liquid-phase volumetric mass-transfer coefficient was established based on 296 data, and the average relative deviation was 8.11%. The sensitivity analysis showed that the liquid velocity was more important to gas–liquid mass transfer than gas velocity and particle velocity.

Fluidized beds reactors with liquid bridge and solid bridge coupling actions have been widely used in industry and thus studies of particle agglomerations under such fluidization conditions are of great significance. This work proposed an experimental apparatus combining electro-magnetic induction heating system with fluidized bed to simulate the real conditions for particle reaction heat release and heat transfer in industrial polymerization fluidized bed reactors. The effects of liquid content on agglomeration behavior of wax/graphite composite particles under different fluidization gas temperatures, gas velocities and heating powers have been studied. Through a force balance analysis of particles with liquid bridge and solid bridge coupling actions, relative solid bridge force was taken as a key parameter to demonstrate the effects of solid bridge force and other forces on agglomerations. Results showed that as the relative solid bridge force varied in different ranges, the agglomeration mass presented three different variation trends with liquid increases, namely monotonic increasing, non-monotonic changing and monotonic decreasing, due to different dominating agglomerating mechanisms (liquid evaporation and liquid bridge) during fluidization. According to the results of this study, the proposed criterion based on relative solid bridge force can be used to guide the regulation and control of particle agglomerations in fluidization with liquid bridge and solid bridge coupling actions.

Heat integrated water allocation networks (HIWAN) is a system where water and energy are highly interconnected. Well arranged nexus between water allocation networks and heat exchanger networks would reduce the water and energy consumption significantly. The aim of this study is to develop a novel mathematical programming model for targeting minimum simplified total annual cost of HIWAN. A new transshipment type of heat exchanger networks (HEN) representation is proposed, with features of stream splitting, stream by-pass, non-isothermal mixing, and isothermal mixing. Constraints are added to follow up on the flowrate consistency when stream splitting or mixing happens. Furthermore, a new formulation is presented to count heat exchanger units. The proposed model is formulated as a mixed-integer linear programming (MILP) problem. It is much easier to get feasible solutions than mixed-integer non-linear programming (MINLP) problems, especially for large-scale problems. Three examples including an industrial example and a large-scale case are solved by the proposed model. It is shown that the proposed model is suitable for the synthesis of HIWAN, and more importantly, the obtained results are better than literature records.

Repeated particle-particle and particle-wall collisions and frictions lead to the generation and accumulation of electrostatic charges in the gas-solid fluidized beds. Variations of electrostatic signals are a rich source of information on particle motions and charging, which have rarely been explored and interpreted. To gain a more comprehensive understanding of the induced electrostatic signals in the fluidized beds, an array of arc-shaped induced electrostatic sensors were attached to the outer wall of a fluidized bed. Combined with cross-correlation method, induced electrostatic voltage signals and correlation velocity of particles were measured simultaneously. It was found that electrostatic charges accumulation restrained the particle motions while the average correlation velocity of particles increased with the amount of injecting liquid antistatic agent. Based on the analyses of induced electrostatic signals, the particle correlation velocity, and the particles charge-to-mass ratio under different charging levels, a predictive model of the average particles charge-to-mass ratio was established. Compared with the results obtained from Faraday cup, the estimated results showed a relative error no more than 40%. Simultaneous measurement of particle correlation velocity and particles charge-to-mass ratio were complemented by arc-shaped induced electrostatic sensors array combined with cross-correlation method.

The fluidized bed is widely used in many industrial processes because of its vigorous mixing and heat transfer properties. However, when heat transfer is blocked, the particles are easily melted and agglomerated, and even cause the industrial reactor to shut down. From the point of mechanism analysis, the process of explosive agglomeration is a typical meso-scale problem in the fluidized bed, and there is a complex evolution process between particle fluidization and reactor shutdown. Grasping the regulation of meso-scale structure is one of the major challenges faced by chemical engineering. Thus, in this background, the fluidized bed acoustic emission detection technology, agglomeration fault self-repair technology, and a direct scale-up technique of the fluidized bed mathematical model were invented. These technologies have provided strong reliability for stable operation and have been successfully applied in 14 sets of industrial plants.

The effect of a gradual contraction pipe (GCP) on gas-liquid flow in a circular-sectioned horizontal to vertical 90° duct bend was investigated by computational fluid dynamics (CFD) simulation. The hydrodynamics of gas-liquid flow in 90° duct bends with and without a GCP in the vertical section were compared using a 3D steady Eulerian-Eulerian approach. The predicted static pressure in the vertical section of the pipes and the pressure drop in the whole pipe were consistent with experimental data. Results of simulations showed that liquid could distribute more uniformly at the exit of the pipe with a GCP. The increased uniformity was accompanied by an increase in pressure drop by a factor of less than 10% compared to the pipe without a GCP. The position of minimum pressure in the bend was changed by the GCP. A GCP can alter the trajectories of the fluid and secondary flow. As a result, the fluid can quickly reach a steady state downstream from the bend.

Effluent gas is common in the petrochemical industry. The recovery of effluent gas is of great importance to resource recycle and environmental protection. However, low concentration, low boiling point feature of petrochemical effluent decreases the recovery economy. This article presents a systematic approach to design process networks for recovering effluent gas at subambient temperature. An effluent recovery superstructure that contains HENS (Heat Exchanger Network Synthesis) operator, pressure operator and separation operator is proposed. In addition, multicomponent nonisothermal phase change of streams are allowed inside the HENS operator. Since the process streams exhibit nonlinear temperature-enthalpy relations ( T-H curve), we correlate the enthalpy ( H ) with temperature ( T ), pressure ( P ) and compositions ( m ) of the process streams by a cubic polynomial function to balance the nonlinearity and accuracy of the state equations. The objective of the model is to maximize total annualized revenue by regulating connecting structures as well as operating parameters. Two industry cases are presented to show the accuracy and effectiveness of the proposed approach.

Gas-solid fluidized beds are widely applied in numerous industrial processes. Particle motions significantly affect the performance of fluidized bed reactors and the characterization of particle movements is therefore important for fluidization quality monitoring and scale-up of reactors. Electrostatic charge signals in the fluidized bed contain much dynamic information on particle motions, which are poorly understood and explored. In this work, correlation velocities of Geldart B and D particles were measured, analyzed and compared by induced electrostatic sensors combined with cross-correlation method in the fluidized bed. The results indicated that the average correlation velocity of particle clouds increased and the normalized probability density distributions of correlation velocities broadened when the superficial gas velocity increased in the dense-phase region. Both upward and downward correlation velocities could be acquired in the dynamic bed level region. Under the same excess gas velocity, the average correlation velocity of Geldart D particles was significantly smaller than that of Geldart B particles, which was caused by the smaller bubble sizes caused by the dominant bubble split over coalescence and less volume of gas forming bubbles for Geldart D particles. The experimental results verified the reliability and repeatability of particle correlation velocity measurement by induced electrostatic sensors in the gas-solid fluidized bed, which provides definite potential in monitoring of particle motions.

Based on a cold-flow experimental setup, the transition between trickle flow and pulse flow in a 3D concurrent downflow three-phase moving bed is investigated by the standard deviation of pressure drop and visual observations. Results show that at a constant gas flow rate, the trickle-to-pulse transition shifts to a higher liquid flow rate with the increasing solid flow rate because the particle moving inhibits the formation of local liquid blockage. Furthermore, an empirical model is proposed to fit the trickle-to-pulse transition boundary by correlating the dynamic liquid holdup at the boundary with the gas Reynolds number, the particle velocity, and the relative viscosity. Finally, the effects of the particle moving on the liquid distribution are investigated, which shows that the particle moving makes the liquid distribution more uniform when the solid flow rate is smaller than a certain value. But further increasing the solid flow rate, the liquid distribution becomes uneven.

Solids oscillation circulation is an unstable solids flow behavior exhibited during the start-up process of a circulating fluidized bed (CFB) with sweeping bend return. It results in significant pressure fluctuation and particle loss, further brings about difficulties in establishing a stable solids circulation and blockage of the heat exchanger for recycling gas. However, the oscillation mechanism and hydrodynamic characteristics of the solids oscillation circulation are still far from understanding, since the variation of solids transfer rate, gas flow rate and their complex interactions are still unknown. In this work, the Eulierian-Eulerian method has been employed for the simulation of solids oscillation circulation in a two-dimension (2D) CFB. The results indicate that solids oscillation circulation is triggered by the formation of slugging in the downer, which leads to a decrease of the downer pressure drop and a sharp increase of the riser bypass gas velocity. Besides, intense slugging fluidization is observed in the downer at larger valve opening or higher inlet gas velocity. Moreover, statistical hydrodynamic shows uniform lateral solids volume distributions in the riser and downer. Solids fluctuating energy spectrum is generated to explore the turbulent characteristics, a segment phenomenon is observed in the inertial sub-region. In addition, the deviation of scale index in the inertial region form the Kolmogorov −5/3 scaling law indicates the flow intermittency. According to the wavelet analysis of particle fluctuation velocity, the particle-particle and particle-wall interaction are found to be the main reason for the flow intermittency.

To improve the aromatics yield of methanol to aromatics conversion (MTA) over zeolite, which has become a potential route for producing aromatics, modified ZSM-5 catalysts with equimolar metals denoted as EM-X/ZSM-5 (X = Zn, Cu, Ag, and Ni) were investigated under CO2 and N2 flow for MTA in a fixed-bed reactor. The physicochemical properties were characterized by atomic absorption spectroscopy (AAS), N2 adsorption–desorption isotherms, X-ray diffraction (XRD), and NH3 temperature-programmed desorption (NH3-TPD). Comparison with the results obtained in pure N2 flow showed that catalysts doped with Zn, Ni, and Ag could promote aromatization activity and BTX yield in the presence of CO2. Among these, EM-Zn/ZSM-5 showed an aromatics yield of 59.05%, with an increase of 8.1%, whereas EM-Cu/ZSM-5 was found to reduce the aromatization activity in the presence of CO2. Moreover, the interaction mechanism of the active sites of the catalysts with CO2 for the MTA reaction was explored on the basis of the absorbability of the catalysts for CO2, which was studied by CO2 temperature-programmed desorption (CO2-TPD); the activation ability for CO2 to combine with hydrogen was investigated by the catalytic reaction of CO2 + H2, and the verification experiments for the coupling behavior of ZSM-5 doped with different contents of Zn in the presence of CO2 were carried out.

A series of Ce1−xTixO2−δ mixed oxide catalysts were synthesized using a homogeneous precipitation method and characterized, and then these catalysts were applied to convert acetic acid to acetone using a gas-phase ketonization reaction. Ti-doped Ce1−xTixO2−δ catalysts (x = 0.1–0.5) exhibited much better ketonization performance than their parent catalysts of CeO2 and TiO2, and such Ti-doping-induced catalysis improvement is attributed to the formation of a Ce–O–Ti structure depending on the Ti content. Among the different Ce1−xTixO2−δ catalysts, the Ce0.7Ti0.3O2−δ catalyst calcinated at 500 °C showed the best catalysis activity and high stability. A combination of techniques (i.e. TEM, FTIR, H2-TPR, NH3/CO2-TPD and XPS) further revealed that the formation of the Ce–O–Ti structure modified the surface acid–base properties and thus enhanced the redox properties. Moreover, the introduction of Ti into CeO2 also increased the number of oxygen vacancies on the catalysts’ surface that favored the ketonization of acid molecules. This work provides valuable insights into the design of highly efficient CeO2-based catalysts for acid removal in the upgrading process of bio-oil.

This paper presented a novel mathematical programming model for the simultaneous optimization of heat integrated water allocation networks featuring parallel heat exchanger network (HEN) structure. In the HEN structure, both freshwater and wastewater can be split freely. This model was suitable for both uniform wastewater treatment and separate wastewater treatment cases. The proposed model was formulated as a MINLP (mixed-integer non-linear programming) problem, making it applicable to large scale problems. The main objective was to minimize the total annual cost. Three literature examples, including a large scale example, were illustrated to demonstrate the applicability of the model. It was shown that the proposed method was as accurate as the literature methods for small scale problems, but performed better for large scale problem applications.