Luhong Zhang

Calculation of Metzner Constant for Double Helical Ribbon Impeller by Computational Fluid Dynamic Method

Abstract Using the multiple reference frames (MRF) impeller method, the three-dimensional non-Newtonian flow field generated by a double helical ribbon (DHR) impeller has been simulated. The velocity field calculated by the numerical simulation was similar to the previous studies and the power constant agreed well with the experimental data. Three computational fluid dynamic (CFD) methods, labeled I, II and III, were used to compute the Metzner constant ks. The results showed that the calculated value from the slop method (method I) was consistent with the experimental data. Method II, which took the maximal circumference-average shear rate around the impeller as the effective shear rate to compute ks, also showed good agreement with the experiment. However, both methods suffer from the complexity of calculation procedures. A new method (method III) was devised in this paper to use the area-weighted average viscosity around the impeller as the effective viscosity for calculating ks. Method III showed both good accuracy and ease of use.

Heterogeneous oxidative desulfurization of diesel fuel catalyzed by mesoporous polyoxometallate-based polymeric hybrid

In this work, the simple preparation of novel polymer supported polyoxometallates (POMs) catalysts has been reported. Soluble task-specific cross-linked poly (ionic liquid) (PIL) was prepared with N,​N-​dimethyl-​dodecyl-​(4-​vinylbenzyl) ammonium chloride and divinylbenzene as co-monomers. The as-prepared cationic PILs were assembled with different commercial POMs to form the interlinked mesoporous catalysts, and the formation mechanism was provided. The catalytic oxidation activities of the catalysts were closely related to the formation pathway of their corresponding peroxide active species. The catalyst with H2W12O4210- as counterion, which exhibited the best activity in the oxidation of benzothiophene (BT) and dibenzothiophene (DBT) to sulfones in model oil with hydrogen peroxide (H2O2, 30wt%) as oxidant, was characterized by different techniques and systematically studied for its sulfur removal performance. As for the oxidative desulfurization of a real diesel, it was observed that almost all of the original sulfur compounds could be completely converted, and the catalyst could be reused for at least eight cycles without noticeable changes in both catalytic activity and chemical structure. In the end, a catalytic mechanism was put forward with the assistant of Raman analysis.

A Novel SiC Foam Valve Tray for Distillation Columns

The novel SiC foam valve tray was made of thin slices of SiC foam material with a high specific surface area. Hydrodynamic performances of the novel SiC foam valve tray were studied with air-water system at atmospheric pressure. These performance parameters included pressure drop, entrainment, weeping and clear liquid height. The mass transfer efficiency of the SiC foam valve tray was measured in laboratory plate column. Compared with the F1 float valve tray, the dry pressure drop was decreased about 25%, the entrainment rate was about 70% lower at high gas load, the weeping was much better, and the mass transfer efficiency was far higher. Thus, the overall performance of the novel SiC foam valve tray was better than that of F1 float valve tray.

Experimental Study of Precision-Woven Fabrics for Oil-In-Water Emulsion Coalescence: Operating Conditions and Oil Saturation

Fabrics have the advantage of having high mechanical strength and low environmental sensitivity. The Kozeny–Carman equation and its modified form can be used to predict permeability, pressure drop, porosity, and oil saturation, as well as to help find optimum pore size. Experiments were conducted under a wide range of flow velocity, oil concentration, bed length, and pore size. Under optimal conditions, more than 90% of surfactant-stabilized emulsified oil could be removed. Relating the pressure drop and oil saturation with separation efficiency aids in a clearer understanding of emulsion transport in fibrous media and finding the optimum medium and operating conditions.

Separations of Different Binary Hydrocarbon Mixtures Using Pressure Swing Thermally Coupled Distillation Process

This paper presents a novel distillation and separation process: Pressure Swing Thermally Coupled Distillation, and investigates the performance of the process by separating 24 different kinds of binary hydrocarbon mixtures with different boiling point differences by this process, and calculates their cost-saving efficiency in comparison with conventional distillation column, respectively. This work focuses on the comparison of cost-saving efficiency, and adopts the comparison methods of standard coal equivalent and total annul cost calculation. Based on the comparison results, this process is optimized and confirmed that it is more cost-saving than conventional distillation and even heat-pump distillation for the separation of binary systems; therefore, this process will increase distillation efficiency greatly and save much energy for all the world, and thus it is worth considering the practical application and this paper will supply valuable guidelines and simulation calculation basis for industrial application.

CFD Simulation and Experimental Validation of Fluid Flow in Pre-distributor *

Abstract Liquid distributor is a very import internal for distillation columns. Pre-distributor is usually set on the top of distributor for initial distribution. Fluid flow in pre-distributor is a complex system of variable mass flow with many orifices and sub-branches. Consequently, the two phase modeling of pre-distributors was carried out and the homogeneous model with free surface model was applied. The numerical method was validated by comparing with experimental data. Using the simulated results for different pre-distributors, the impacts of inflow rate, location and orientation upon the outflow distribution were investigated. Furthermore, influences of the outflow distribution for pre-distributor on liquid uniformity in trough were also analyzed. The conclusions can be adopted for the structural design of liquid distributor and pre-distributor of large scale.

Synthesis of chlorostannate(II) ionic liquids and their novel application in the preparation of high-quality L-lactide

Polylactic acid (PLA) is a representative biodegradable polymer, which is expected to be a promising replacement for some petroleum-based materials. Noticeably, the properties of PLA products depend strongly on the quality of the lactide monomer, a crucial precursor of PLA production. In this work, a large range of different chlorostannate(II) ionic liquids (ILs), prepared by mixing 1-butyl-3-methyl-imidazolium chloride and tin(II) chloride in various molar ratios, xSnCl2, were firstly applied for the preparation of L-lactide of high chemical and optical purity. The cation–anion interaction, the thermal stability and the acidity of imidazolium-based chlorostannate(II) ionic liquids were experimentally determined and systematically analyzed. Compared with the conventional SnCl2 catalyst, the depolymerization of oligomeric poly(L-lactic acid) catalyzed by chlorostannate(II) ionic liquids occurred in a moderate yield. Interestingly, using [Bmim]Cl–SnCl2 (xSnCl2 = 0.63) as a catalyst, L-lactide of 99.9% optical purity was obtained, simultaneously leaving a high-Mw oligomeric residue with high isotacticity (99.1%). Furthermore, the effects of various reaction parameters were investigated in order to obtain the highest possible yield of lactide. A plausible reaction mechanism was suggested and discussed. Finally, owing to the reutilization of PLLA residue of high isotacticity, a reiterative lactide synthesis was realized. The recycled catalyst showed no notable loss of activity. By combining this chlorostannate(II)-based IL (xSnCl2 = 0.63) catalyst technology with the cyclic resynthesis process, high-quality L-lactide could be selectively produced in high yield (>80%, based on L-lactic acid replenished).

Novel Protic Ionic Liquid Composite Membranes with Fast and Selective Gas Transport Nanochannels for Ethylene/Ethane Separation

Protic ionic liquids (PILs) were utilized for the fabrication of composite membranes containing silver salt as the C2H4 transport carrier to perform C2H4/C2H6 separation for the first time. The intrinsic nanostructures of PILs were adopted to construct fast and selective C2H4 transport nanochannels. The investigation of structure-performance relationships of composite membranes suggested that transport nanochannels (polar domains of PILs) could be tuned by the sizes of cations, which greatly manipulated activity of the carrier and determined the separation performances of membranes. The role of different carriers in the facilitated transport was studied, which revealed that the PILs were good solvents for dissolution and activation of the carrier due to their hydrogen bond networks and waterlike properties. The operating conditions of separation process were investigated systemically and optimized, confirming C2H4/C2H6 selectivity was enhanced with the increase of silver salt concentration, the flow rate of sweep gas, and the feed ratio of C2H4 to C2H6, as well as the decrease of the transmembrane pressure and operating temperature. Furthermore, the composite membranes exhibited long-term stability and obtained very competitive separation performances compared with other results. In summary, PIL composite membranes, which possess good long-term stability, high C2H4/C2H6 selectivity, and excellent C2H4 permeability, may have a good perspective in industrial C2H4/C2H6 separation.

Preparation of poly(L-lactic acid) membrane from solvent mixture via immersion precipitation

ABSTRACT Poly (L-lactic acid) (PLLA) membranes were fabricated through immersion precipitation method. 1, 4-dioxane (DX), N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethyl-acetamide (DMAc), and DX/NMP, DX/DMF and DX/DMAc were used as solvents severally. With a focus on the PLLA/DX/NMP/H2O system, the effect of solvent mixture on PLLA membrane was investigated by altering the ratio of DX/NMP. Various membrane morphologies were obtained, which were further correlated by mean of solubility parameter and viscosity of casting solution. It was found that the membrane cast with DX/NMP (1/1) exhibited ideal structure and better performance compared with membranes cast with same concentration of PLLA.

Modeling and simulation of a multistage absorption hydration hybrid process using equation oriented modeling environment

Abstract Separation of light hydrocarbon mixtures is one of the most important topics in chemical engineering research. With development of theories on hydrate equilibriums and kinetics, researchers are trying to apply hydration based separation technology to industrial applications. It is increasingly important to develop the corresponding simulation strategies for process design purposes. In this work we use an equation oriented modeling environment, named Aspen Custom Modeler ® (ACM ® ), which enables rapid model development and provides powerful simulation solvers. With the help of ACM ® , a multistage absorption hydration hybrid process (AHHP) for refinery dry gas separation is modeled and simulated. Sensitivities of key parameters such as water content and absorbent flow rate, are analyzed. Features of the multistage AHHP are discussed. For comparison, based on an industrial data, a butane absorption process is established and simulated. Economic evaluation shows that the multistage AHHP is competitive compared to current absorption process.