To account for the effect of liquid viscosity, the bubble breakup model considering turbulent eddy collision based on the inertial subrange turbulent spectrum was extended to the entire turbulent spectrum that included the energy-containing, inertial, and energy-dissipation subranges. The computational fluid dynamics-population balance model (CFD-PBM) coupled model was modified to include this extended bubble breakup model for simulations of a bubble column. The effect of turbulent energy spectrum on the bubble breakup and hydrodynamic behaviors was studied in a bubble column under different liquid viscosities. The results showed that when the liquid viscosity was < 80 mPas, the bubble breakup and hydrodynamics were almost independent on the turbulent spectrum. At liquid viscosity > 80 mPas, the bubble breakup rate and gas holdup were significantly under-predicted when the inertial turbulent spectrum was used, and when using the entire turbulent spectrum the predictions were more consistent with experimental data.

Additive manufacturing is increasingly being used to develop innovative packings for absorption and desorption columns. Since distillation has not been in focus so far, this paper aims to fill this gap. The objective is to obtain a miniaturized 3D printed packed column with optimized properties in terms of scalability and reproducibility, which increases process development efficiency. For this purpose, a flexible laboratory scale test rig is presented combining standard laboratory equipment with 3D printed components such as innovative multifunctional trays or the column wall with packing. The test rig offers a particularly wide operating range (F=0.15 Pa0.5…1.0 Pa0.5) for column diameters between 20 mm and 50 mm. First results regarding the time to reach steady-state, operational stability and separation efficiency measurements are presented using a 3D printable version of the Rombopak 9M. Currently, innovative packings are being characterized, which should exhibit a optimized bevavior regarding scalability, reproducibility and separation efficiency.

Bubble breakup plays an important role in gas-liquid flows, but detailed studies are still scarce. In this work, the breakup behavior of a single bubble in a stirred tank was experimentally studied with a high-speed camera, focusing on the effect of gas density, liquid properties, agitation speed and mother bubble size. The bubble breakup time, breakup probability, breakup rate and daughter bubble size distribution were determined. The internal flow phenomenon inside a deformed bubble was studied in detail, which accounted for the effect of gas density or operating pressure. The results showed that with increasing gas density, agitation speed, mother bubble size and decreasing surface tension, the bubble breakup rate and probability of equal-size distribution significantly increased. With increasing liquid viscosity, the bubble breakup rate decreased especially in the high viscosity range. An M-shaped daughter bubble size distribution was observed, which was consistent with our previous bubble breakup model.

Separation of mixed ion, especially Cl- and SO42-, is essential for reduced energy consumption and achievement of the minimal or zero-liquid discharge. Membrane technology has attracted significant attention in this respect owing to its good system coupling and maturity. However, it remains challenging to fabricate highly selective nanofilm with fine-tuning pore and structure that is suitable for the separation of Cl- and SO42-. Herein, we report an asymmetric alicyclic polyamide nanofilm with enhanced interconnectivity pore by manipulating the molecular geometry structure, composed of the porous aromatic polyamide dendrimer layer, and the dense alicyclic polyamide layer with hollow stripes. This resulted membrane shows a 107.14% separation rate of Cl- and SO42-, and a water flux (for Na2SO4) of ~2.2 times that of the pristine polyamide membrane. We estimate this fine-tuning pore approach resulting from alicyclic structure also might be employed in other separation membranes such as gas, solvent or neutral molecules.

Reactor corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems through a protective water film formed on its internal surface. In this work, the effects of key structural parameters on water film properties of transpiring wall reactor were explored by numerical simulation, and established models were validated by comparing simulation and experimental values. The results show that transpiration water layer, transpiring wall porosity and inner diameter hardly affected organic matter degradation. Increasing transpiration water layer and transpiring wall porosity reduced reactor center temperatures in the middle and lower zones of the reactor. Increasing transpiration water layer, transpiring wall porosity and inner diameter decreased water film temperatures but increased water film coverage rates. Increasing reactor length affected slightly on the volume of the upper supercritical oxidation zone but enlarged the subcritical zone.

We present the development and application of a two-phase stirred reactor model for heavy oil upgrading in the presence of supercritical water (SCW), with coupled phase-specific thermolysis reaction kinetics and multicomponent hydrocarbon water phase equilibrium. We demonstrate the inference of oil and water phase kinetics parameters for a compact lumped reaction kinetics model through the application of this model to two different sets of batch reactor experiments reported in the literature. We infer that, though SCW can suppress the formation of newer polynuclear aromatics (PNA) from distillate range species, it is broadly ineffective in deterring the combination of pre-existing PNA fragments in the oil feed. Quantification of the conversion to distillate liquids before the onset of coke formation helps arrive at a clearer conclusion on whether the use of SCW in the batch reactor leads to better product outcomes for different oil feeds and operating conditions.

Reactive transport codes are today one of the cornerstones of environmental research. They now contain multiphysics with very complex algorithms, including flow, transport, chemical and sometimes heat transport, mechanical and/or biological algorithms. Because of this complexity, some parts of these algorithms still have not been sufficiently studied. Here, we present a comparison of 3 algorithms for activity correction, a specific subset of equilibrium chemistry algorithms. We show that the most used algorithm (the inner fixed-point algorithm) or the most rigorous algorithm (the full Newton) might not be the most efficient, and we propose the outer fixed-point algorithm, which is more robust and faster than other algorithms.

We investigate the drying process of monodisperse colloidal film over a wide range of Péclet number (Pe) by using the Brownian dynamics simulation. We analyze the detailed process in three aspects; accumulation front, normal stress, and microstructure. The evolution of particle distribution is quantified by tracking the accumulation front. The accumulated particles contribute to the continuous increase of the normal stress at the interface. At the substrate, the normal stress first stays constant and then increases as the accumulation front touches the substrate. We quantitatively analyze the stress development by a scaled normal stress difference between the two boundaries. At all tested Pe, the stress difference increases to the maximum, followed by a decrease during drying. Interestingly, a mismatch is observed between the stress difference maximum and the initial stress increase at the substrate. The microstructural analysis reveals that this mismatch is related to the microstructural development at the substrate.

A predictive model based on Fick’s second law for radial diffusion is proposed and validated for modeling the diffusion of fragrances. A pure component, two binary systems, and a ternary system were used for validation. The model combines the prediction model to represent the liquid phase non-idealities, using the UNIFAC group contribution method, with the Fickian radial diffusion approach. The experimental headspace concentrations were measured in a diffusion chamber using the solid-phase microextraction (SPME) technique and quantified using gas chromatography with a flame ionization detector (GC-FID). The numerical solutions were obtained along with an analytical model considering constant surface concentration. The odor intensities of the studied systems were calculated using Stevens’ power law and the strongest component model, respectively. The numerical simulation presented good adherence to the experimental gas concentration data. The proposed methodology is an efficient and validated tool to assess the radial diffusion of fragrance and volatile systems.

Centrifugal pumps are used in several industrial processes. It is common the operation of this equipment with gas-liquid mixtures, which is the case of the electrical submersible pumping artificial lift method used in the oil industry. The increase of free gas fraction inside the pump may lead to unstable operation and problems such as surging and gas locking phenomena to occur. In this study a drift-flux model is proposed for the gas-liquid flow subjected to centrifugal fields using the impeller as an example. The model is closed with experimental data of bubble diameter, displacements and velocities acquired via high-speed camera at several different rotational speeds and gas mass flow rates using water as the continuous medium. From the modeling and the forces balance in the bubbles, a quantitative criterion for the start point of surging and gas locking conditions was proposed.

Ethyl levulinate, one of main derivatives of levulinic acid (LA), is of significant potential as platform chemicals for bio-based materials. The esterification of LA was generally carried out in a conventional batch reactor or in a conventional reactive distillation column. However, traditional methods are hard to deal with equilibrium limited reactions and azeotropic issues. Therefore, the reactive-vapor permeation-distillation (R-VP-D) process, which integrated reaction, distillation and membrane dehydration into one single unit, is proposed in this paper and validated in the pilot-scale experiments. A comparative study is made between a pilot-scale RD column with and without vapor permeation membrane module. Owing to the water-selective membrane and the ingenious design of related apparatuses, the R-VP-D process reveal a superiority in LA conversion of 21.9% maximum higher than RD without VP process and removing of product water about 53.6% from VP module, which indicates its promising industrial application in process intensification field.

Hydrophobic deep eutectic solvents (DESs) have emerged as excellent extractants. Their performance depends on the heterogeneous hydrogen bond environment formed by multiple hydrogen bond donors and acceptors. An understanding of this heterogeneous hydrogen bond environment can be used to develop principles for designing high-performance DESs for extraction and other separation applications. We investigate the structure and dynamics of hydrogen bonds in eight hydrophobic DESs formed by decanoic acid, menthol, thymol, and Lidocaine using molecular dynamics simulations. The results show the diversity of hydrogen bonds in the eight DESs and their impact on diffusivity and molecular association. Each DES possesses four-six types of hydrogen bonds and one or two of them overwhelm the others in quantity and lifetime. The dominating hydrogen bonds determine whether the DESs are governed by intra- or inter-component associations. The component diffusivity presents an inverse relationship with the hydrogen bond strength.

Bubbles rising through fluidized beds at velocities several times superficial velocities contribute to solids backmixing. In micro-fluidized beds, the walls constrain bubble sizes and velocities. To evaluate gas-phase hydrodynamics and identify diffusional contributions to longitudinal dispersion, we injected a mixture of H2, CH4, CO, and CO2 (syngas) as a bolus into a fluidized bed of porous fluid catalytic cracking catalyst while a mass-spectrometer monitored the effluent gas concentrations at 2 Hz. The CH4, CO, and CO2 trailing RTD traces were elongated versus H2 demonstrating a chromatographic effect. An axial dispersion model accounted for 92% of the variance in the data but including diffusional resistance between the bulk gas and catalyst pores and adsorption explained 98.6% of the variability. At 300 °C, the CO2 tailing disappeared consistent with expectations in chromatography (no adsorption). H2 and He are poor gas-phase tracers at ambient temperature. We recommend measuring the RTD at operating conditions.

In this work, the enumeration algorithms presented in parts I and II for the globally optimal synthesis of heat exchanger networks are extended to consider non-isothermal mixing. The previous models are modified by adding non-isothermal mixing constraints and new models are constructed to target the bounds of the energy consumption and the binding exchanger minimum approximation temperature. These new models are solved using algorithms that involve solving the solution of systems of equations instead of mathematical programming. We also present two alternatives for optimizing each enumerated structure, namely, the use of a global solver, or the use of a golden search with simple resolution of non-isothermal mixing model for fixed energy consumption. The non-isothermal mixing model is reformulated as a convex model, either solved using nonlinear programming or a programming-free methodology, i.e. solving Karush-Kuhn-Tucker equations. A global optimum search algorithm is developed and examples are tested comparing the proposed strategies.

A gas-liquid stirred tank reactor (STR) has some problems, such as low mass transfer efficiency, high exhaust gas oxygen concentration, and low product conversion rate, due to limitations of stirring speed and input power. This article proposes a method to enhance the gas-liquid mass transfer in a STR using circulating jet internals. When a circulating jet is added, the average bubble size in the reactor is reduced to 1.26 mm, and the overall gas holdup is increased to 8.23%, which is an increase of 3.62 times of the original STR. The gas-liquid volumetric mass transfer coefficient is increased to 0.05556 s-1, which is 4.84 times of the original STR. The unit volume power is increased by only 1.4 times. These data provide references for the design and scale-up of new jet STRs.

First principles studies combined with the microkinetic analysis were performed to study the reliability and reaction mechanisms of single-atom doped graphene (SADGr) materials in catalyzing NOx reduction with CO. By screening the 3d transition metals (Sc-Zn) and group-IV elements (Si and Ge), it was found that the Ti and Co doped graphene sheets (TiGr and CoGr) respectively own excellent catalytic activities in the NO/NO2-to-N2O and the N2O-to-N2 processes at low temperatures. Therefore, the TiGr/CoGr composite can be a promising catalyst in NOx reduction with CO. It was further revealed the combination of adsorption energy and electronegativity was a good descriptor to predict the activation energies. The obtained results can provide useful information for rational design of carbon-based single-atom catalysts for NOx reduction by CO at low temperatures.

The vast majority of solid-liquid mixing studies have focused on high Reynolds number applications with configurations and impeller geometries adapted to this type of regime. However, the mixing of particles in a viscous fluid is an essential element of many contemporary industries. We used the CFD-DEM model previously developed in our group to investigate solid-liquid mixing with close-clearance impellers in the laminar regime of operation. We compared different geometries that is, the double helical ribbon, anchor, Paravisc$^{TM}$, and Maxblend$^{TM}$ impellers. We investigated the impact of fluid viscosity and compared the results with those obtained with the pitched blade turbine, a more commonly used impeller, based on power consumption for equivalent mixing states. This study highlights that the higher the viscosity of the fluid, the more interesting it is to use close-clearance impellers for their ability to generate a strong shear stress and a strong bulk flow in the entire vessel.

A bubble column was investigated as a method to achieve a desired and controllable rate of evaporation of a pharmaceutical solution in continuous processing mode. Applying a developed thermodynamic model to predict the rate of evaporation, all predicted values achieved accuracies within the bounds of instrumentation errors. The model accounted for the measured effect of reduced vapor pressure caused by dissolved solids as a function of their concentration. A general method to obtain accurate measurement of this effect is introduced and applied, improving the accuracy of model predictions. Predicting the rate of evaporation using the developed model, consistent and repeatable evaporation rates ranging from 0.7–6.9 g/min were achieved. Applying the column as a controllable evaporator, the concentration of a dilute feed stream was increased in a single equilibrium stage and coupled to a crystallizer. The configured system achieved a steady state of controllable operation over a duration of 5 hours